Fourier fringe analysis and its application to metrology of extreme physical phenomena: a review [Invited].

PubMed

Takeda, Mitsuo

2013-01-01

The paper reviews a technique for fringe analysis referred to as Fourier fringe analysis (FFA) or the Fourier transform method, with a particular focus on its application to metrology of extreme physical phenomena. Examples include the measurement of extremely small magnetic fields with subfluxon sensitivity by electron wave interferometry, subnanometer wavefront evaluation of projection optics for extreme UV lithography, the detection of sub-Ångstrom distortion of a crystal lattice, and the measurement of ultrashort optical pulses in the femotsecond to attosecond range, which show how the advantages of FFA are exploited in these cutting edge applications.

Automatic Topography Using High Precision Digital Moire Methods

NASA Astrophysics Data System (ADS)

Yatagai, T.; Idesawa, M.; Saito, S.

1983-07-01

Three types of moire topographic methods using digital techniques are proposed. Deformed gratings obtained by projecting a reference grating onto an object under test are subjected to digital analysis. The electronic analysis procedures of deformed gratings described here enable us to distinguish between depression and elevation of the object, so that automatic measurement of 3-D shapes and automatic moire fringe interpolation are performed. Based on the digital moire methods, we have developed a practical measurement system, with a linear photodiode array on a micro-stage as a scanning image sensor. Examples of fringe analysis in medical applications are presented.

Interactive Fringe Analysis System: Applications To Moire Contourogram And Interferogram

NASA Astrophysics Data System (ADS)

Yatagai, T.; Idesawa, M.; Yamaashi, Y.; Suzuki, M.

1982-10-01

A general purpose fringe pattern processing facility was developed in order to analyze moire photographs used for scoliosis diagnoses and interferometric patterns in optical shops. A TV camera reads a fringe profile to be analyzed, and peaks of the fringe are detected by a microcomputer. Fringe peak correction and fringe order determination are performed with the man-machine interactive software developed. A light pen facility and an image digitizer are employed for interaction. In the case of two-dimensional fringe analysis, we analyze independently analysis lines parallel to each other and a reference line perpendicular to the parallel analysis lines. Fringe orders of parallel analysis lines are uniquely determined by using the fringe order of the reference line. Some results of analysis of moire contourograms, interferometric testing of silicon wafers, and holographic measurement of thermal deformation are presented.

Vortex-Airfoil Interaction and Application of Methods for Digital Fringe Analysis.

DTIC Science & Technology

1986-03-15

angles of attack. Different kinds of bluff bodies are used as vortex generators. Their wake is a Karman vortex street consisting of strong vortices of...Table of Contents 1. Introduction 1 2. A model for vortex paths around a profile and the sound generated by vortex -profile interaction 2"-- 3...I’ S.TTE(d~,t. TYPE OF PIrPORT a PERID COWERED ’. * Vortex -airfoil interaction and application of *methods for digital fringe analysis . 1 6

Optical mapping of surface roughness by implementation of a spatial light modulator

NASA Astrophysics Data System (ADS)

Aulbach, Laura; Pöller, Franziska; Lu, Min; Wang, Shengjia; Koch, Alexander W.

2017-08-01

It is well-known that the surface roughness of materials plays an important role in the operation and performance of technological systems. The roughness influences key parameters, such as friction and wear, and is directly connected to the functionality and durability of the respective system. Tactile methods are widely used for the measurement of surface roughness, but a destructive measurement procedure and the lack of feasibility of online monitoring are crucial drawbacks. In the last decades, several non-contact, usually optical systems for surface roughness measurements have been developed, e.g., white light interferometry, light scatter analysis, or speckle correlation. These techniques are in turn often unable to assign the roughness to a certain surface area or involve inappropriate adjustment procedures. One promising and straightforward optical measurement method is the surface roughness measurement by analyzing the fringe visibility of an interferometric fringe pattern. In our work, we employed a spatial light modulator in the interferometric setup to vary the fringe visibility and provide a stable and reliable measurement system. In previous research, either the averaged fringe visibility or the fringe visibility along a defined observation profile were analyzed. In this article, the analysis of the fringe visibility is extended to generate a complete roughness map of the measurement target. Thus, surface defects or areas of different roughness can be easily located.

Fringe order correction for the absolute phase recovered by two selected spatial frequency fringe projections in fringe projection profilometry.

PubMed

Ding, Yi; Peng, Kai; Yu, Miao; Lu, Lei; Zhao, Kun

2017-08-01

The performance of the two selected spatial frequency phase unwrapping methods is limited by a phase error bound beyond which errors will occur in the fringe order leading to a significant error in the recovered absolute phase map. In this paper, we propose a method to detect and correct the wrong fringe orders. Two constraints are introduced during the fringe order determination of two selected spatial frequency phase unwrapping methods. A strategy to detect and correct the wrong fringe orders is also described. Compared with the existing methods, we do not need to estimate the threshold associated with absolute phase values to determine the fringe order error, thus making it more reliable and avoiding the procedure of search in detecting and correcting successive fringe order errors. The effectiveness of the proposed method is validated by the experimental results.

Quantitative assessment of soft tissue deformation using digital speckle pattern interferometry: studies on phantom breast models.

PubMed

Karuppanan, Udayakumar; Unni, Sujatha Narayanan; Angarai, Ganesan R

2017-01-01

Assessment of mechanical properties of soft matter is a challenging task in a purely noninvasive and noncontact environment. As tissue mechanical properties play a vital role in determining tissue health status, such noninvasive methods offer great potential in framing large-scale medical screening strategies. The digital speckle pattern interferometry (DSPI)-based image capture and analysis system described here is capable of extracting the deformation information from a single acquired fringe pattern. Such a method of analysis would be required in the case of the highly dynamic nature of speckle patterns derived from soft tissues while applying mechanical compression. Soft phantoms mimicking breast tissue optical and mechanical properties were fabricated and tested in the DSPI out of plane configuration set up. Hilbert transform (HT)-based image analysis algorithm was developed to extract the phase and corresponding deformation of the sample from a single acquired fringe pattern. The experimental fringe contours were found to correlate with numerically simulated deformation patterns of the sample using Abaqus finite element analysis software. The extracted deformation from the experimental fringe pattern using the HT-based algorithm is compared with the deformation value obtained using numerical simulation under similar conditions of loading and the results are found to correlate with an average %error of 10. The proposed method is applied on breast phantoms fabricated with included subsurface anomaly mimicking cancerous tissue and the results are analyzed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, Yubo; School of Physics and Electronic Information Science, Gannan Normal University, Ganzhou 341000; Lei, Yunfei

An image converter tube with a magnetic lens was used to obtain static images of moiré fringes formed by electron beam. These moiré fringes are formed due to the interference between the anode mesh and the photocathode containing slits of various spatial frequencies. Moiré fringes are observed at an accelerating voltage of 3.5 kV requiring the magnetic excitation condition of ∼550 ampere-turns. Not only the features of the fringes are analyzed but also the change of fringe spacing as a function of the rotation angle is investigated. The experimental results are found well in agreement with the theoretical analysis. By changingmore » the rotation angle or adjusting the excitation condition of the magnetic lens, we were able to record parallel moiré and secondary moiré fringes too. The secondary moiré fringes can be observed in the rotation angle range of −39.5° to −50.6°. The theoretical analysis indicates that the secondary moiré is formed by the interference between the photocathode slits and the 2-D periodic structure of the anode mesh. Combining our proposed moiré method with the pulse-dilation technique may potentially open the door for future applications, in various fields including, but not limited to, ultrafast electrical pulse diagnostics.« less

Fringe-period selection for a multifrequency fringe-projection phase unwrapping method

NASA Astrophysics Data System (ADS)

Zhang, Chunwei; Zhao, Hong; Jiang, Kejian

2016-08-01

The multi-frequency fringe-projection phase unwrapping method (MFPPUM) is a typical phase unwrapping algorithm for fringe projection profilometry. It has the advantage of being capable of correctly accomplishing phase unwrapping even in the presence of surface discontinuities. If the fringe frequency ratio of the MFPPUM is too large, fringe order error (FOE) may be triggered. FOE will result in phase unwrapping error. It is preferable for the phase unwrapping to be kept correct while the fewest sets of lower frequency fringe patterns are used. To achieve this goal, in this paper a parameter called fringe order inaccuracy (FOI) is defined, dominant factors which may induce FOE are theoretically analyzed, a method to optimally select the fringe periods for the MFPPUM is proposed with the aid of FOI, and experiments are conducted to research the impact of the dominant factors in phase unwrapping and demonstrate the validity of the proposed method. Some novel phenomena are revealed by these experiments. The proposed method helps to optimally select the fringe periods and detect the phase unwrapping error for the MFPPUM.

Three-beam interferogram analysis method for surface flatness testing of glass plates and wedges

NASA Astrophysics Data System (ADS)

Sunderland, Zofia; Patorski, Krzysztof

2015-09-01

When testing transparent plates with high quality flat surfaces and a small angle between them the three-beam interference phenomenon is observed. Since the reference beam and the object beams reflected from both the front and back surface of a sample are detected, the recorded intensity distribution may be regarded as a sum of three fringe patterns. Images of that type cannot be succesfully analyzed with standard interferogram analysis methods. They contain, however, useful information on the tested plate surface flatness and its optical thickness variations. Several methods were elaborated to decode the plate parameters. Our technique represents a competitive solution which allows for retrieval of phase components of the three-beam interferogram. It requires recording two images: a three-beam interferogram and the two-beam one with the reference beam blocked. Mutually subtracting these images leads to the intensity distribution which, under some assumptions, provides access to the two component fringe sets which encode surfaces flatness. At various stages of processing we take advantage of nonlinear operations as well as single-frame interferogram analysis methods. Two-dimensional continuous wavelet transform (2D CWT) is used to separate a particular fringe family from the overall interferogram intensity distribution as well as to estimate the phase distribution from a pattern. We distinguish two processing paths depending on the relative density of fringe sets which is connected with geometry of a sample and optical setup. The proposed method is tested on simulated data.

Generalized spin filtering and an improved derivative-sign binary image method for the extraction of fringe skeletons

NASA Astrophysics Data System (ADS)

Yu, Qifeng; Liu, Xiaolin; Sun, Xiangyi

1998-07-01

Generalized spin filters, including several directional filters such as the directional median filter and the directional binary filter, are proposed for removal of the noise of fringe patterns and the extraction of fringe skeletons with the help of fringe-orientation maps (FOM s). The generalized spin filters can filter off noise on fringe patterns and binary fringe patterns efficiently, without distortion of fringe features. A quadrantal angle filter is developed to filter off the FOM. With these new filters, the derivative-sign binary image (DSBI) method for extraction of fringe skeletons is improved considerably. The improved DSBI method can extract high-density skeletons as well as common density skeletons.

Single and two-shot quantitative phase imaging using Hilbert-Huang Transform based fringe pattern analysis

NASA Astrophysics Data System (ADS)

Trusiak, Maciej; Micó, Vicente; Patorski, Krzysztof; García-Monreal, Javier; Sluzewski, Lukasz; Ferreira, Carlos

2016-08-01

In this contribution we propose two Hilbert-Huang Transform based algorithms for fast and accurate single-shot and two-shot quantitative phase imaging applicable in both on-axis and off-axis configurations. In the first scheme a single fringe pattern containing information about biological phase-sample under study is adaptively pre-filtered using empirical mode decomposition based approach. Further it is phase demodulated by the Hilbert Spiral Transform aided by the Principal Component Analysis for the local fringe orientation estimation. Orientation calculation enables closed fringes efficient analysis and can be avoided using arbitrary phase-shifted two-shot Gram-Schmidt Orthonormalization scheme aided by Hilbert-Huang Transform pre-filtering. This two-shot approach is a trade-off between single-frame and temporal phase shifting demodulation. Robustness of the proposed techniques is corroborated using experimental digital holographic microscopy studies of polystyrene micro-beads and red blood cells. Both algorithms compare favorably with the temporal phase shifting scheme which is used as a reference method.

Two-dimensional wavelet transform for reliability-guided phase unwrapping in optical fringe pattern analysis.

PubMed

Li, Sikun; Wang, Xiangzhao; Su, Xianyu; Tang, Feng

2012-04-20

This paper theoretically discusses modulus of two-dimensional (2D) wavelet transform (WT) coefficients, calculated by using two frequently used 2D daughter wavelet definitions, in an optical fringe pattern analysis. The discussion shows that neither is good enough to represent the reliability of the phase data. The differences between the two frequently used 2D daughter wavelet definitions in the performance of 2D WT also are discussed. We propose a new 2D daughter wavelet definition for reliability-guided phase unwrapping of optical fringe pattern. The modulus of the advanced 2D WT coefficients, obtained by using a daughter wavelet under this new daughter wavelet definition, includes not only modulation information but also local frequency information of the deformed fringe pattern. Therefore, it can be treated as a good parameter that represents the reliability of the retrieved phase data. Computer simulation and experimentation show the validity of the proposed method.

Anti-spoof touchless 3D fingerprint recognition system using single shot fringe projection and biospeckle analysis

NASA Astrophysics Data System (ADS)

Chatterjee, Amit; Bhatia, Vimal; Prakash, Shashi

2017-08-01

Fingerprint is a unique, un-alterable and easily collected biometric of a human being. Although it is a 3D biological characteristic, traditional methods are designed to provide only a 2D image. This touch based mapping of 3D shape to 2D image losses information and leads to nonlinear distortions. Moreover, as only topographic details are captured, conventional systems are potentially vulnerable to spoofing materials (e.g. artificial fingers, dead fingers, false prints, etc.). In this work, we demonstrate an anti-spoof touchless 3D fingerprint detection system using a combination of single shot fringe projection and biospeckle analysis. For fingerprint detection using fringe projection, light from a low power LED source illuminates a finger through a sinusoidal grating. The fringe pattern modulated because of features on the fingertip is captured using a CCD camera. Fourier transform method based frequency filtering is used for the reconstruction of 3D fingerprint from the captured fringe pattern. In the next step, for spoof detection using biospeckle analysis a visuo-numeric algorithm based on modified structural function and non-normalized histogram is proposed. High activity biospeckle patterns are generated because of interaction of collimated laser light with internal fluid flow of the real finger sample. This activity reduces abruptly in case of layered fake prints, and is almost absent in dead or fake fingers. Furthermore, the proposed setup is fast, low-cost, involves non-mechanical scanning and is highly stable.

Serial number coding and decoding by laser interference direct patterning on the original product surface for anti-counterfeiting.

PubMed

Park, In-Yong; Ahn, Sanghoon; Kim, Youngduk; Bae, Han-Sung; Kang, Hee-Shin; Yoo, Jason; Noh, Jiwhan

2017-06-26

Here, we investigate a method to distinguish the counterfeits by patterning multiple reflective type grating directly on the surface of the original product and analyze the serial number from its rotation angles of diffracted fringes. The micro-sized gratings were fabricated on the surface of the material at high speeds by illuminating the interference fringe generated by passing a high-energy pulse laser through the Fresnel biprism. In addition, analysis of the grating's diffraction fringes was performed using a continuous wave laser.

Quantitative assessment of soft tissue deformation using digital speckle pattern interferometry: studies on phantom breast models

PubMed Central

Karuppanan, Udayakumar; Unni, Sujatha Narayanan; Angarai, Ganesan R.

2017-01-01

Abstract. Assessment of mechanical properties of soft matter is a challenging task in a purely noninvasive and noncontact environment. As tissue mechanical properties play a vital role in determining tissue health status, such noninvasive methods offer great potential in framing large-scale medical screening strategies. The digital speckle pattern interferometry (DSPI)–based image capture and analysis system described here is capable of extracting the deformation information from a single acquired fringe pattern. Such a method of analysis would be required in the case of the highly dynamic nature of speckle patterns derived from soft tissues while applying mechanical compression. Soft phantoms mimicking breast tissue optical and mechanical properties were fabricated and tested in the DSPI out of plane configuration set up. Hilbert transform (HT)-based image analysis algorithm was developed to extract the phase and corresponding deformation of the sample from a single acquired fringe pattern. The experimental fringe contours were found to correlate with numerically simulated deformation patterns of the sample using Abaqus finite element analysis software. The extracted deformation from the experimental fringe pattern using the HT-based algorithm is compared with the deformation value obtained using numerical simulation under similar conditions of loading and the results are found to correlate with an average %error of 10. The proposed method is applied on breast phantoms fabricated with included subsurface anomaly mimicking cancerous tissue and the results are analyzed. PMID:28180134

High dynamic range fringe acquisition: A novel 3-D scanning technique for high-reflective surfaces

NASA Astrophysics Data System (ADS)

Jiang, Hongzhi; Zhao, Huijie; Li, Xudong

2012-10-01

This paper presents a novel 3-D scanning technique for high-reflective surfaces based on phase-shifting fringe projection method. High dynamic range fringe acquisition (HDRFA) technique is developed to process the fringe images reflected from the shiny surfaces, and generates a synthetic fringe image by fusing the raw fringe patterns, acquired with different camera exposure time and the illumination fringe intensity from the projector. Fringe image fusion algorithm is introduced to avoid saturation and under-illumination phenomenon by choosing the pixels in the raw fringes with the highest fringe modulation intensity. A method of auto-selection of HDRFA parameters is developed and largely increases the measurement automation. The synthetic fringes have higher signal-to-noise ratio (SNR) under ambient light by optimizing HDRFA parameters. Experimental results show that the proposed technique can successfully measure objects with high-reflective surfaces and is insensitive to ambient light.

Analysis of contact zones from whole field isochromatics using reflection photoelasticity

NASA Astrophysics Data System (ADS)

Hariprasad, M. P.; Ramesh, K.

2018-06-01

This paper discusses the method for evaluating the unknown contact parameters by post processing the whole field fringe order data obtained from reflection photoelasticity in a nonlinear least squares sense. Recent developments in Twelve Fringe Photoelasticity (TFP) for fringe order evaluation from single isochromatics is utilized for the whole field fringe order evaluation. One of the issues in using TFP for reflection photoelasticity is the smudging of isochromatic data at the contact zone. This leads to error in identifying the origin of contact, which is successfully addressed by implementing a semi-automatic contact point refinement algorithm. The methodologies are initially verified for benchmark problems and demonstrated for two application problems of turbine blade and sheet pile contacting interfaces.

Atmospheric tomography using a fringe pattern in the sodium layer.

PubMed

Baharav, Y; Ribak, E N; Shamir, J

1994-02-15

We wish to measure and separate the contribution of atmospheric turbulent layers for multiconjugate adaptive optics. To this end, we propose to create a periodic fringe pattern in the sodium layer and image it with a modified Hartmann sensor. Overlapping sections of the fringes are imaged by a lenslet array onto contiguous areas in a large-format camera. Low-layer turbulence causes an overall shift of the fringe pattern in each lenslet, and high-attitude turbulence results in internal deformations in the pattern. Parallel Fourier analysis permits separation of the atmospheric layers. Two mirrors, one conjugate to a ground layer and the other conjugate to a single high-altitude layer, are shown to widen the field of view significantly compared with existing methods.

Learning to Read and Write on the Fringes of Schooling: Some Examples of Didactic Devices in Mexican Society in the Modern Era

ERIC Educational Resources Information Center

Castro, Josefina Granja

2008-01-01

This paper focuses on the analysis of certain didactic resources that proliferated on the fringes of schooling during the second half of the nineteenth century in Mexico. The first of these is a method that, according to its author, made it possible to teach a pupil how to read in only six lessons, dated 1830; the second is a writing method from…

Particle measurement systems and methods

DOEpatents

Steele, Paul T [Livermore, CA

2011-10-04

A system according to one embodiment includes a light source for generating light fringes; a sampling mechanism for directing a particle through the light fringes; and at least one light detector for detecting light scattered by the particle as the particle passes through the light fringes. A method according to one embodiment includes generating light fringes using a light source; directing a particle through the light fringes; and detecting light scattered by the particle as the particle passes through the light fringes using at least one light detector.

Spatially-Heterodyned Holography

DOEpatents

Thomas, Clarence E [Knoxville, TN; Hanson, Gregory R [Clinton, TN

2006-02-21

A method of recording a spatially low-frequency heterodyne hologram, including spatially heterodyne fringes for Fourier analysis, includes: splitting a laser beam into a reference beam and an object beam; interacting the object beam with an object; focusing the reference beam and the object beam at a focal plane of a digital recorder to form a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis; digital recording the spatially low-frequency heterodyne hologram; Fourier transforming axes of the recorded spatially low-frequency heterodyne hologram including spatially heterodyne fringes in Fourier space to sit on top of a heterodyne carrier frequency defined by an angle between the reference beam and the object beam; cutting off signals around an origin; and performing an inverse Fourier transform.

Further Developments of the Fringe-Imaging Skin Friction Technique

NASA Technical Reports Server (NTRS)

Zilliac, Gregory C.

1996-01-01

Various aspects and extensions of the Fringe-Imaging Skin Friction technique (FISF) have been explored through the use of several benchtop experiments and modeling. The technique has been extended to handle three-dimensional flow fields with mild shear gradients. The optical and imaging system has been refined and a PC-based application has been written that has made it possible to obtain high resolution skin friction field measurements in a reasonable period of time. The improved method was tested on a wingtip and compared with Navier-Stokes computations. Additionally, a general approach to interferogram-fringe spacing analysis has been developed that should have applications in other areas of interferometry. A detailed error analysis of the FISF technique is also included.

Estimation of Phase in Fringe Projection Technique Using High-order Instantaneous Moments Based Method

NASA Astrophysics Data System (ADS)

Gorthi, Sai Siva; Rajshekhar, G.; Rastogi, Pramod

2010-04-01

For three-dimensional (3D) shape measurement using fringe projection techniques, the information about the 3D shape of an object is encoded in the phase of a recorded fringe pattern. The paper proposes a high-order instantaneous moments based method to estimate phase from a single fringe pattern in fringe projection. The proposed method works by approximating the phase as a piece-wise polynomial and subsequently determining the polynomial coefficients using high-order instantaneous moments to construct the polynomial phase. Simulation results are presented to show the method's potential.

Moire technique utilization for detection and measurement of scoliosis

NASA Astrophysics Data System (ADS)

Zawieska, Dorota; Podlasiak, Piotr

1993-02-01

Moire projection method enables non-contact measurement of the shape or deformation of different surfaces and constructions by fringe pattern analysis. The fringe map acquisition of the whole surface of the object under test is one of the main advantages compared with 'point by point' methods. The computer analyzes the shape of the whole surface and next user can selected different points or cross section of the object map. In this paper a few typical examples of an application of the moire technique in solving different medical problems will be presented. We will also present to you the equipment the moire pattern analysis is done in real time using the phase stepping method with CCD camera.

FFT swept filtering: a bias-free method for processing fringe signals in absolute gravimeters

NASA Astrophysics Data System (ADS)

Křen, Petr; Pálinkáš, Vojtech; Mašika, Pavel; Val'ko, Miloš

2018-05-01

Absolute gravimeters, based on laser interferometry, are widely used for many applications in geoscience and metrology. Although currently the most accurate FG5 and FG5X gravimeters declare standard uncertainties at the level of 2-3 μGal, their inherent systematic errors affect the gravity reference determined by international key comparisons based predominately on the use of FG5-type instruments. The measurement results for FG5-215 and FG5X-251 clearly showed that the measured g-values depend on the size of the fringe signal and that this effect might be approximated by a linear regression with a slope of up to 0.030 μGal/mV . However, these empirical results do not enable one to identify the source of the effect or to determine a reasonable reference fringe level for correcting g-values in an absolute sense. Therefore, both gravimeters were equipped with new measuring systems (according to Křen et al. in Metrologia 53:27-40, 2016. https://doi.org/10.1088/0026-1394/53/1/27 applied for FG5), running in parallel with the original systems. The new systems use an analogue-to-digital converter HS5 to digitize the fringe signal and a new method of fringe signal analysis based on FFT swept bandpass filtering. We demonstrate that the source of the fringe size effect is connected to a distortion of the fringe signal due to the electronic components used in the FG5(X) gravimeters. To obtain a bias-free g-value, the FFT swept method should be applied for the determination of zero-crossings. A comparison of g-values obtained from the new and the original systems clearly shows that the original system might be biased by approximately 3-5 μGal due to improperly distorted fringe signal processing.

Fast fringe pattern phase demodulation using FIR Hilbert transformers

NASA Astrophysics Data System (ADS)

Gdeisat, Munther; Burton, David; Lilley, Francis; Arevalillo-Herráez, Miguel

2016-01-01

This paper suggests the use of FIR Hilbert transformers to extract the phase of fringe patterns. This method is computationally faster than any known spatial method that produces wrapped phase maps. Also, the algorithm does not require any parameters to be adjusted which are dependent upon the specific fringe pattern that is being processed, or upon the particular setup of the optical fringe projection system that is being used. It is therefore particularly suitable for full algorithmic automation. The accuracy and validity of the suggested method has been tested using both computer-generated and real fringe patterns. This novel algorithm has been proposed for its advantages in terms of computational processing speed as it is the fastest available method to extract the wrapped phase information from a fringe pattern.

Fringe pattern demodulation with a two-frame digital phase-locked loop algorithm.

PubMed

Gdeisat, Munther A; Burton, David R; Lalor, Michael J

2002-09-10

A novel technique called a two-frame digital phase-locked loop for fringe pattern demodulation is presented. In this scheme, two fringe patterns with different spatial carrier frequencies are grabbed for an object. A digital phase-locked loop algorithm tracks and demodulates the phase difference between both fringe patterns by employing the wrapped phase components of one of the fringe patterns as a reference to demodulate the second fringe pattern. The desired phase information can be extracted from the demodulated phase difference. We tested the algorithm experimentally using real fringe patterns. The technique is shown to be suitable for noncontact measurement of objects with rapid surface variations, and it outperforms the Fourier fringe analysis technique in this aspect. Phase maps produced withthis algorithm are noisy in comparison with phase maps generated with the Fourier fringe analysis technique.

Accuracy and high-speed technique for autoprocessing of Young's fringes

NASA Astrophysics Data System (ADS)

Chen, Wenyi; Tan, Yushan

1991-12-01

In this paper, an accurate and high-speed method for auto-processing of Young's fringes is proposed. A group of 1-D sampled intensity values along three or more different directions are taken from Young's fringes, and the fringe spacings of each direction are obtained by 1-D FFT respectively. Two directions that have smaller fringe spacing are selected from all directions. The accurate fringe spacings along these two directions are obtained by using orthogonal coherent phase detection technique (OCPD). The actual spacing and angle of Young's fringes, therefore, can be calculated. In this paper, the principle of OCPD is introduced in detail. The accuracy of the method is evaluated theoretically and experimentally.

Encoder fault analysis system based on Moire fringe error signal

NASA Astrophysics Data System (ADS)

Gao, Xu; Chen, Wei; Wan, Qiu-hua; Lu, Xin-ran; Xie, Chun-yu

2018-02-01

Aiming at the problem of any fault and wrong code in the practical application of photoelectric shaft encoder, a fast and accurate encoder fault analysis system is researched from the aspect of Moire fringe photoelectric signal processing. DSP28335 is selected as the core processor and high speed serial A/D converter acquisition card is used. And temperature measuring circuit using AD7420 is designed. Discrete data of Moire fringe error signal is collected at different temperatures and it is sent to the host computer through wireless transmission. The error signal quality index and fault type is displayed on the host computer based on the error signal identification method. The error signal quality can be used to diagnosis the state of error code through the human-machine interface.

Detection for flatness of large surface based on structured light

NASA Astrophysics Data System (ADS)

He, Wenyan; Cao, Xuedong; Long, Kuang; Peng, Zhang

2016-09-01

In order to get flatness of a large plane, this paper set up a measurement system, composed by Line Structured Light, imaging system, CCD, etc. Line Structured Light transmits parallel fringes at a proper angle onto the plane which is measured; the imaging system and CCD locate above the plane to catch the fringes. When the plane is perfect, CCD will catch straight fringes; however, the real plane is not perfect; according to the theory of projection, the fringes caught by CCD will be distorted by convex and concave. Extract the center of line fringes to obtain the distortion of the fringe, according to the functional relationship between the distortion of fringes and the height which is measured, then we will get flatness of the entire surface. Data from experiment approached the analysis of theory. In the simulation, the vertical resolution is 0.0075 mm per pixel when measuring a plane of 400mm×400mm, choosing the size of CCD 4096×4096, at the angle 85°. Helped by sub-pixel, the precision will get the level of submicron. There are two obvious advantages: method of surface sampling can increase the efficiency for auto-repairing of machines; considering the center of fringe is required mainly in this system, as a consequence, there is no serious demand for back light.

A new method for determining the plasma electron density using three-color interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arakawa, Hiroyuki; Kawano, Yasunori; Itami, Kiyoshi

2012-06-15

A new method for determining the plasma electron density using the fractional fringes on three-color interferometer is proposed. Integrated phase shift on each interferometer is derived without using the temporal history of the fractional fringes. The dependence on the fringe resolution and the electrical noise are simulated on the wavelengths of CO{sub 2} laser. Short-time integrations of the fractional fringes enhance the reliability of this method.

Frequency guided methods for demodulation of a single fringe pattern.

PubMed

Wang, Haixia; Kemao, Qian

2009-08-17

Phase demodulation from a single fringe pattern is a challenging task but of interest. A frequency-guided regularized phase tracker and a frequency-guided sequential demodulation method with Levenberg-Marquardt optimization are proposed to demodulate a single fringe pattern. Demodulation path guided by the local frequency from the highest to the lowest is applied in both methods. Since critical points have low local frequency values, they are processed last so that the spurious sign problem caused by these points is avoided. These two methods can be considered as alternatives to the effective fringe follower regularized phase tracker. Demodulation results from one computer-simulated and two experimental fringe patterns using the proposed methods will be demonstrated. (c) 2009 Optical Society of America

Topometry of technical and biological objects by fringe projection

NASA Astrophysics Data System (ADS)

Windecker, R.; Tiziani, H. J.

1995-07-01

Fringe projection is a fast and accurate technique for obtaining the topometry of a wide range of surfaces. Here some features of the principle are described, together with the possibilities of adapting this technique for the measurement of vaulted surfaces. We discuss various methods of phase evaluation and compare them with simulated computer data to obtain the resolution limits. Under certain restrictions a semispatial algorithm, called the modified Fourier analysis algorithm, gives the best results. One special subject of interest is the application of fringe projection for the measurement of the three-dimensional surface of the cornea. First results of in vivo measurements are presented.

Phase demodulation method from a single fringe pattern based on correlation with a polynomial form.

PubMed

Robin, Eric; Valle, Valéry; Brémand, Fabrice

2005-12-01

The method presented extracts the demodulated phase from only one fringe pattern. Locally, this method approaches the fringe pattern morphology with the help of a mathematical model. The degree of similarity between the mathematical model and the real fringe is estimated by minimizing a correlation function. To use an optimization process, we have chosen a polynomial form such as a mathematical model. However, the use of a polynomial form induces an identification procedure with the purpose of retrieving the demodulated phase. This method, polynomial modulated phase correlation, is tested on several examples. Its performance, in terms of speed and precision, is presented on very noised fringe patterns.

Automatic evaluation of interferograms

NASA Technical Reports Server (NTRS)

Becker, F.

1982-01-01

A system for the evaluation of interference patterns was developed. For digitizing and processing of the interferograms from classical and holographic interferometers a picture analysis system based upon a computer with a television digitizer was installed. Depending on the quality of the interferograms, four different picture enhancement operations may be used: Signal averaging; spatial smoothing, subtraction of the overlayed intensity function and the removal of distortion-patterns using a spatial filtering technique in the frequency spectrum of the interferograms. The extraction of fringe loci from the digitized interferograms is performed by a foating-threshold method. The fringes are numbered using a special scheme after the removal of any fringe disconnections which appeared if there was insufficient contrast in the holograms. The reconstruction of the object function from the fringe field uses least squares approximation with spline fit. Applications are given.

Single-shot color fringe projection for three-dimensional shape measurement of objects with discontinuities.

PubMed

Dai, Meiling; Yang, Fujun; He, Xiaoyuan

2012-04-20

A simple but effective fringe projection profilometry is proposed to measure 3D shape by using one snapshot color sinusoidal fringe pattern. One color fringe pattern encoded with a sinusoidal fringe (as red component) and one uniform intensity pattern (as blue component) is projected by a digital video projector, and the deformed fringe pattern is recorded by a color CCD camera. The captured color fringe pattern is separated into its RGB components and division operation is applied to red and blue channels to reduce the variable reflection intensity. Shape information of the tested object is decoded by applying an arcsine algorithm on the normalized fringe pattern with subpixel resolution. In the case of fringe discontinuities caused by height steps, or spatially isolated surfaces, the separated blue component is binarized and used for correcting the phase demodulation. A simple and robust method is also introduced to compensate for nonlinear intensity response of the digital video projector. The experimental results demonstrate the validity of the proposed method.

Axial resonance of periodic patterns by using a Fresnel biprism.

PubMed

Doblas, Ana; Saavedra, Genaro; Martinez-Corral, Manuel; Barreiro, Juan C; Sanchez-Ortiga, Emilio; Llavador, Anabel

2013-01-01

This paper proposes a method for the generation of high-contrast localized sinusoidal fringes with spatially noncoherent illumination and relatively high light throughput. The method, somehow similar to the classical Lau effect, is based on the use of a Fresnel biprism. It has some advantages over previous methods for the noncoherent production of interference fringes. One is the flexibility of the method, which allows the control of the fringe period by means of a simple axial shift of the biprism. Second is the rapid axial fall-off in visibility around the high-contrast fringe planes. And third is the possibility of creating fringes with increasing or with constant period as the light beam propagates. Experimental verifications of the theoretical statements are also provided.

Comprehensive time average digital holographic vibrometry

NASA Astrophysics Data System (ADS)

Psota, Pavel; Lédl, Vít; Doleček, Roman; Mokrý, Pavel; Vojtíšek, Petr; Václavík, Jan

2016-12-01

This paper presents a method that simultaneously deals with drawbacks of time-average digital holography: limited measurement range, limited spatial resolution, and quantitative analysis of the measured Bessel fringe patterns. When the frequency of the reference wave is shifted by an integer multiple of frequency at which the object oscillates, the measurement range of the method can be shifted either to smaller or to larger vibration amplitudes. In addition, phase modulation of the reference wave is used to obtain a sequence of phase-modulated fringe patterns. Such fringe patterns can be combined by means of phase-shifting algorithms, and amplitudes of vibrations can be straightforwardly computed. This approach independently calculates the amplitude values in every single pixel. The frequency shift and phase modulation are realized by proper control of Bragg cells and therefore no additional hardware is required.

Analysis of Fringe Field Formed Inside LDA Measurement Volume Using Compact Two Hololens Imaging Systems

NASA Astrophysics Data System (ADS)

Ghosh, Abhijit; Nirala, A. K.; Yadav, H. L.

2018-03-01

We have designed and fabricated four LDA optical setups consisting of aberration compensated four different compact two hololens imaging systems. We have experimentally investigated and realized a hololens recording geometry which is interferogram of converging spherical wavefront with mutually coherent planar wavefront. Proposed real time monitoring and actual fringe field analysis techniques allow complete characterizations of fringes formed at measurement volume and permit to evaluate beam quality, alignment and fringe uniformity with greater precision. After experimentally analyzing the fringes formed at measurement volume by all four imaging systems, it is found that fringes obtained using compact two hololens imaging systems get improved both qualitatively and quantitatively compared to that obtained using conventional imaging system. Results indicate qualitative improvement of non-uniformity in fringe thickness and micro intensity variations perpendicular to the fringes, and quantitative improvement of 39.25% in overall average normalized standard deviations of fringe width formed by compact two hololens imaging systems compare to that of conventional imaging system.

Validating Laser-Induced Birefringence Theory with Plasma Interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Cecilia; Cornell Univ., Ithaca, NY

2015-09-02

Intense laser beams crossing paths in plasma is theorized to induce birefringence in the medium, resulting from density and refractive index modulations that affect the polarization of incoming light. The goal of the associated experiment, conducted on Janus at Lawrence Livermore’s Jupiter Laser Facility, was to create a tunable laser-plasma waveplate to verify the relationship between dephasing angle and beam intensity, plasma density, plasma temperature, and interaction length. Interferometry analysis of the plasma channel was performed to obtain a density map and to constrain temperature measured from Thomson scattering. Various analysis techniques, including Fast Fourier transform (FFT) and two variationsmore » of fringe-counting, were tried because interferograms captured in this experiment contained unusual features such as fringe discontinuity at channel edges, saddle points, and islands. The chosen method is flexible, semi-automated, and uses a fringe tracking algorithm on a reduced image of pre-traced synthetic fringes. Ultimately, a maximum dephasing angle of 49.6° was achieved using a 1200 μm interaction length, and the experimental results appear to agree with predictions.« less

Second-order oriented partial-differential equations for denoising in electronic-speckle-pattern interferometry fringes.

PubMed

Tang, Chen; Han, Lin; Ren, Hongwei; Zhou, Dongjian; Chang, Yiming; Wang, Xiaohang; Cui, Xiaolong

2008-10-01

We derive the second-order oriented partial-differential equations (PDEs) for denoising in electronic-speckle-pattern interferometry fringe patterns from two points of view. The first is based on variational methods, and the second is based on controlling diffusion direction. Our oriented PDE models make the diffusion along only the fringe orientation. The main advantage of our filtering method, based on oriented PDE models, is that it is very easy to implement compared with the published filtering methods along the fringe orientation. We demonstrate the performance of our oriented PDE models via application to two computer-simulated and experimentally obtained speckle fringes and compare with related PDE models.

Combination of oriented partial differential equation and shearlet transform for denoising in electronic speckle pattern interferometry fringe patterns.

PubMed

Xu, Wenjun; Tang, Chen; Gu, Fan; Cheng, Jiajia

2017-04-01

It is a key step to remove the massive speckle noise in electronic speckle pattern interferometry (ESPI) fringe patterns. In the spatial-domain filtering methods, oriented partial differential equations have been demonstrated to be a powerful tool. In the transform-domain filtering methods, the shearlet transform is a state-of-the-art method. In this paper, we propose a filtering method for ESPI fringe patterns denoising, which is a combination of second-order oriented partial differential equation (SOOPDE) and the shearlet transform, named SOOPDE-Shearlet. Here, the shearlet transform is introduced into the ESPI fringe patterns denoising for the first time. This combination takes advantage of the fact that the spatial-domain filtering method SOOPDE and the transform-domain filtering method shearlet transform benefit from each other. We test the proposed SOOPDE-Shearlet on five experimentally obtained ESPI fringe patterns with poor quality and compare our method with SOOPDE, shearlet transform, windowed Fourier filtering (WFF), and coherence-enhancing diffusion (CEDPDE). Among them, WFF and CEDPDE are the state-of-the-art methods for ESPI fringe patterns denoising in transform domain and spatial domain, respectively. The experimental results have demonstrated the good performance of the proposed SOOPDE-Shearlet.

Broadband interferometric characterization of divergence and spatial chirp.

PubMed

Meier, Amanda K; Iliev, Marin; Squier, Jeff A; Durfee, Charles G

2015-09-01

We demonstrate a spectral interferometric method to characterize lateral and angular spatial chirp to optimize intensity localization in spatio-temporally focused ultrafast beams. Interference between two spatially sheared beams in an interferometer will lead to straight fringes if the wavefronts are curved. To produce reference fringes, we delay one arm relative to another in order to measure fringe rotation in the spatially resolved spectral interferogram. With Fourier analysis, we can obtain frequency-resolved divergence. In another arrangement, we spatially flip one beam relative to the other, which allows the frequency-dependent beamlet direction (angular spatial chirp) to be measured. Blocking one beam shows the spatial variation of the beamlet position with frequency (i.e., the lateral spatial chirp).

Retrieval of phase-derivative discontinuities in digital speckle pattern interferometry fringes using the Wigner-Ville distribution

NASA Astrophysics Data System (ADS)

Federico, Alejandro; Kaufmann, Guillermo H.

2004-08-01

We evaluate the application of the Wigner-Ville distribution (WVD) to measure phase gradient maps in digital speckle pattern interferometry (DSPI), when the generated correlation fringes present phase discontinuities. The performance of the WVD method is evaluated using computer-simulated fringes. The influence of the filtering process to smooth DSPI fringes and additional drawbacks that emerge when this method is applied are discussed. A comparison with the conventional method based on the continuous wavelet transform in the stationary phase approximation is also presented.

Phase demodulation from a single fringe pattern based on a correlation technique.

PubMed

Robin, Eric; Valle, Valéry

2004-08-01

We present a method for determining the demodulated phase from a single fringe pattern. This method, based on a correlation technique, searches in a zone of interest for the degree of similarity between a real fringe pattern and a mathematical model. This method, named modulated phase correlation, is tested with different examples.

Enhanced dual-frequency pattern scheme based on spatial-temporal fringes method

NASA Astrophysics Data System (ADS)

Wang, Minmin; Zhou, Canlin; Si, Shuchun; Lei, Zhenkun; Li, Xiaolei; Li, Hui; Li, YanJie

2018-07-01

One of the major challenges of employing a dual-frequency phase-shifting algorithm for phase retrieval is its sensitivity to noise. Yun et al proposed a dual-frequency method based on the Fourier transform profilometry, yet the low-frequency lobes are close to each other for accurate band-pass filtering. In the light of this problem, a novel dual-frequency pattern based on the spatial-temporal fringes (STF) method is developed in this paper. Three fringe patterns with two different frequencies are required. The low-frequency phase is obtained from two low-frequency fringe patterns by the STF method, so the signal lobes can be extracted accurately as they are far away from each other. The high-frequency phase is retrieved from another fringe pattern without the impact of the DC component. Simulations and experiments are conducted to demonstrate the excellent precision of the proposed method.

Soot Nanostructure: Using Fringe Analysis Software on High Resolution Transmission Electron Microscopy of Carbon Soot

NASA Technical Reports Server (NTRS)

King, James D.

2004-01-01

Using high resolution transmission electron images of carbon nanotubes and carbon particles, we are able to use image analysis program to determine several carbon fringe properties, including length, separation, curvature and orientation. Results are shown in the form of histograms for each of those quantities. The combination of those measurements can give a better indication of the graphic structure within nanotubes and particles of carbon and can distinguish carbons based upon fringe properties. Carbon with longer, straighter and closer spaced fringes are considered graphite, while amorphous carbon contain shorter, less structured fringes.

3D image acquisition by fiber-based fringe projection

NASA Astrophysics Data System (ADS)

Pfeifer, Tilo; Driessen, Sascha

2005-02-01

In macroscopic production processes several measuring methods are used to assure the quality of 3D parts. Definitely, one of the most widespread techniques is the fringe projection. It"s a fast and accurate method to receive the topography of a part as a computer file which can be processed in further steps, e.g. to compare the measured part to a given CAD file. In this article it will be shown how the fringe projection method is applied to a fiber-optic system. The fringes generated by a miniaturized fringe projector (MiniRot) are first projected onto the front-end of an image guide using special optics. The image guide serves as a transmitter for the fringes in order to get them onto the surface of a micro part. A second image guide is used to observe the micro part. It"s mounted under an angle relating to the illuminating image guide so that the triangulation condition is fulfilled. With a CCD camera connected to the second image guide the projected fringes are recorded and those data is analyzed by an image processing system.

Highlight removal based on the regional-projection fringe projection method

NASA Astrophysics Data System (ADS)

Qi, Zhaoshuai; Wang, Zhao; Huang, Junhui; Xing, Chao; Gao, Jianmin

2018-04-01

In fringe projection profilometry, highlight usually causes the saturation and blooming in captured fringes and reduces the measurement accuracy. To solve the problem, a regional-projection fringe projection (RP-FP) method is proposed. Regional projection patterns (RP patterns) are projected onto the tested object surface to avoid the saturation and blooming. Then, an image inpainting technique is employed to reconstruct the missing phases in the captured RP patterns and a complete surface of the tested object is obtained. Experiments verified the effectiveness of the proposed method. The method can be widely used in industrial inspections and quality controlling in mechanical and manufacturing industries.

Surface flatness measurement of quasi-parallel plates employing three-beam interference with strong reference beam

NASA Astrophysics Data System (ADS)

Sunderland, Zofia; Patorski, Krzysztof

2016-12-01

A big challenge for standard interferogram analysis methods such as Temporal Phase Shifting or Fourier Transform is a parasitic set of fringes which might occur in the analyzed fringe pattern intensity distribution. It is encountered, for example, when transparent glass plates with quasi-parallel surfaces are tested in Fizeau or Twyman-Green interferometers. Besides the beams reflected from the plate front surface and the interferometer reference the beam reflected from the plate rear surface also plays important role; its amplitude is comparable with the amplitude of other beams. In result we face three families of fringes of high contrast which cannot be easily separated. Earlier we proposed a competitive solution for flatness measurements which relies on eliminating one of those fringe sets from the three-beam interferogram and separating two remaining ones with the use of 2D Continuous Wavelet Transform. In this work we cover the case when the intensity of the reference beam is significantly higher than the intensities of two object beams. The main advantage of differentiating beam intensities is the change in contrast of individual fringe families. Processing of such three-beam interferograms is modified but also takes advantage of 2D CWT. We show how to implement this method in Twyman-Green and Fizeau setups and compare this processing path and measurement procedures with previously proposed solutions.

Employing Conjoint Analysis in Making Compensation Decisions.

ERIC Educational Resources Information Center

Kienast, Philip; And Others

1983-01-01

Describes a method employing conjoint analysis that generates utility/cost ratios for various elements of the compensation package. Its superiority to simple preference surveys is examined. Results of a study of the use of this method in fringe benefit planning in a large financial institution are reported. (Author/JAC)

Adaptive projection intensity adjustment for avoiding saturation in three-dimensional shape measurement

NASA Astrophysics Data System (ADS)

Chen, Chao; Gao, Nan; Wang, Xiangjun; Zhang, Zonghua

2018-03-01

Phase-based fringe projection methods have been commonly used for three-dimensional (3D) measurements. However, image saturation results in incorrect intensities in captured fringe pattern images, leading to phase and measurement errors. Existing solutions are complex. This paper proposes an adaptive projection intensity adjustment method to avoid image saturation and maintain good fringe modulation in measuring objects with a high range of surface reflectivities. The adapted fringe patterns are created using only one prior step of fringe-pattern projection and image capture. First, a set of phase-shifted fringe patterns with maximum projection intensity value of 255 and a uniform gray level pattern are projected onto the surface of an object. The patterns are reflected from and deformed by the object surface and captured by a digital camera. The best projection intensities corresponding to each saturated-pixel clusters are determined by fitting a polynomial function to transform captured intensities to projected intensities. Subsequently, the adapted fringe patterns are constructed using the best projection intensities at projector pixel coordinate. Finally, the adapted fringe patterns are projected for phase recovery and 3D shape calculation. The experimental results demonstrate that the proposed method achieves high measurement accuracy even for objects with a high range of surface reflectivities.

A quantum radar detection protocol for fringe visibility enhancement

NASA Astrophysics Data System (ADS)

Koltenbah, Benjamin; Parazzoli, Claudio; Capron, Barbara

2016-05-01

We present analysis of a radar detection technique using a Photon Addition Homodyne Receiver (PAHR) that improves SNR of the interferometer fringes and reduces uncertainty of the phase measurement. This system uses the concept of Photon Addition (PA) in which the coherent photon distribution is altered. We discuss this process first as a purely mathematical concept to introduce PA and illustrate its effect on coherent photon distribution. We then present a notional proof-of-concept experiment involving a parametric down converter (PDC) and probabilistic post-selection of the results. We end with presentation of a more deterministic PAHR concept that is more suitable for development into a working system. Coherent light illuminates a target and the return signal interferes with the local oscillator reference photons to create the desired fringes. The PAHR alters the photon probability distribution of the returned light via interaction between the return photons and atoms. We refer to this technique as "Atom Interaction" or AI. The returning photons are focused at the properly prepared atomic system. The injected atoms into this region are prepared in the desired quantum state. During the interaction time, the initial quantum state evolves in such a way that the photon distribution function changes resulting in higher photon count, lower phase noise and an increase in fringe SNR. The result is a 3-5X increase of fringe SNR. This method is best suited for low light intensity (low photon count, 0.1-5) applications. The detection protocol could extend the range of existing systems without loss of accuracy, or conversely enhance a system's accuracy for given range. We present quantum mathematical analysis of the method to illustrate how both range and angular resolution improve in comparison with standard measurement techniques. We also suggest an experimental path to validate the method which also will lead toward deployment in the field.

3-D optical profilometry at micron scale with multi-frequency fringe projection using modified fibre optic Lloyd's mirror technique

NASA Astrophysics Data System (ADS)

Inanç, Arda; Kösoğlu, Gülşen; Yüksel, Heba; Naci Inci, Mehmet

2018-06-01

A new fibre optic Lloyd's mirror method is developed for extracting 3-D height distribution of various objects at the micron scale with a resolution of 4 μm. The fibre optic assembly is elegantly integrated to an optical microscope and a CCD camera. It is demonstrated that the proposed technique is quite suitable and practical to produce an interference pattern with an adjustable frequency. By increasing the distance between the fibre and the mirror with a micrometre stage in the Lloyd's mirror assembly, the separation between the two bright fringes is lowered down to the micron scale without using any additional elements as part of the optical projection unit. A fibre optic cable, whose polymer jacket is partially stripped, and a microfluidic channel are used as test objects to extract their surface topographies. Point by point sensitivity of the method is found to be around 8 μm, changing a couple of microns depending on the fringe frequency and the measured height. A straightforward calibration procedure for the phase to height conversion is also introduced by making use of the vertical moving stage of the optical microscope. The phase analysis of the acquired image is carried out by One Dimensional Continuous Wavelet Transform for which the chosen wavelet is the Morlet wavelet and the carrier removal of the projected fringe patterns is achieved by reference subtraction. Furthermore, flexible multi-frequency property of the proposed method allows measuring discontinuous heights where there are phase ambiguities like 2π by lowering the fringe frequency and eliminating the phase ambiguity.

Edge Triggered Apparatus and Method for Measuring Strain in Bragg Gratings

NASA Technical Reports Server (NTRS)

Froggatt, Mark E. (Inventor)

2003-01-01

An apparatus and method for measuring strain of gratings written into an optical fiber. Optical radiation is transmitted over one or more contiguous predetermined wavelength ranges into a reference optical fiber network and an optical fiber network under test to produce a plurality of reference interference fringes and measurement interference fringes, respectively. The reference and measurement fringes are detected, and the reference fringes trigger the sampling of the measurement fringes. This results in the measurement fringes being sampled at 2(pi) increments of the reference fringes. Each sampled measurement fringe of each wavelength sweep is transformed into a spatial domain waveform. The spatial domain waveforms are summed to form a summation spatial domain waveform that is used to determine location of each grating with respect to a reference reflector. A portion of each spatial domain waveform that corresponds to a particular grating is determined and transformed into a corresponding frequency spectrum representation. The strain on the grating at each wavelength of optical radiation is determined by determining the difference between the current wavelength and an earlier, zero-strain wavelength measurement.

Computerized evaluation of holographic interferograms for fatigue crack detection in riveted lap joints

NASA Astrophysics Data System (ADS)

Zhou, Xiang

Using an innovative portable holographic inspection and testing system (PHITS) developed at the Australian Defence Force Academy, fatigue cracks in riveted lap joints can be detected by visually inspecting the abnormal fringe changes recorded on holographic interferograms. In this thesis, for automatic crack detection, some modern digital image processing techniques are investigated and applied to holographic interferogram evaluation. Fringe analysis algorithms are developed for identification of the crack-induced fringe changes. Theoretical analysis of PHITS and riveted lap joints and two typical experiments demonstrate that the fatigue cracks in lightly-clamped joints induce two characteristic fringe changes: local fringe discontinuities at the cracking sites; and the global crescent fringe distribution near to the edge of the rivet hole. Both of the fringe features are used for crack detection in this thesis. As a basis of the fringe feature extraction, an algorithm for local fringe orientation calculation is proposed. For high orientation accuracy and computational efficiency, Gaussian gradient filtering and neighboring direction averaging are used to minimize the effects of image background variations and random noise. The neighboring direction averaging is also used to approximate the fringe directions in centerlines of bright and dark fringes. Experimental results indicate that for high orientation accuracy the scales of the Gaussian filter and neighboring direction averaging should be chosen according to the local fringe spacings. The orientation histogram technique is applied to detect the local fringe discontinuity due to the fatigue cracks. The Fourier descriptor technique is used to characterize the global fringe distribution change from a circular to a crescent distribution with the fatigue crack growth. Experiments and computer simulations are conducted to analyze the detectability and reliability of crack detection using the two techniques. Results demonstrate that the Fourier descriptor technique is more promising in the detection of the short cracks near the edge of the rivet head. However, it is not as reliable as the fringe orientation technique for detection of the long through cracks. For reliability, both techniques should be used in practical crack detection. Neither the Fourier descriptor technique nor the orientation histogram technique have been previously applied to holographic interferometry. While this work related primarily to interferograms of cracked rivets, the techniques would be readily applied to other areas of fringe pattern analysis.

Content-based fused off-axis object illumination direct-to-digital holography

DOEpatents

Price, Jeffery R.

2006-05-02

Systems and methods are described for content-based fused off-axis illumination direct-to-digital holography. A method includes calculating an illumination angle with respect to an optical axis defined by a focusing lens as a function of data representing a Fourier analyzed spatially heterodyne hologram; reflecting a reference beam from a reference mirror at a non-normal angle; reflecting an object beam from an object the object beam incident upon the object at the illumination angle; focusing the reference beam and the object beam at a focal plane of a digital recorder to from the content-based off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis; and digitally recording the content based off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis.

Improvement of the fringe analysis algorithm for wavelength scanning interferometry based on filter parameter optimization.

PubMed

Zhang, Tao; Gao, Feng; Muhamedsalih, Hussam; Lou, Shan; Martin, Haydn; Jiang, Xiangqian

2018-03-20

The phase slope method which estimates height through fringe pattern frequency and the algorithm which estimates height through the fringe phase are the fringe analysis algorithms widely used in interferometry. Generally they both extract the phase information by filtering the signal in frequency domain after Fourier transform. Among the numerous papers in the literature about these algorithms, it is found that the design of the filter, which plays an important role, has never been discussed in detail. This paper focuses on the filter design in these algorithms for wavelength scanning interferometry (WSI), trying to optimize the parameters to acquire the optimal results. The spectral characteristics of the interference signal are analyzed first. The effective signal is found to be narrow-band (near single frequency), and the central frequency is calculated theoretically. Therefore, the position of the filter pass-band is determined. The width of the filter window is optimized with the simulation to balance the elimination of the noise and the ringing of the filter. Experimental validation of the approach is provided, and the results agree very well with the simulation. The experiment shows that accuracy can be improved by optimizing the filter design, especially when the signal quality, i.e., the signal noise ratio (SNR), is low. The proposed method also shows the potential of improving the immunity to the environmental noise by adapting the signal to acquire the optimal results through designing an adaptive filter once the signal SNR can be estimated accurately.

Faster processing of multiple spatially-heterodyned direct to digital holograms

DOEpatents

Hanson, Gregory R.; Bingham, Philip R.

2006-10-03

Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms. A method includes of obtaining multiple spatially-heterodyned holograms, includes: digitally recording a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; digitally recording a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a first angle between a first reference beam and a first, object beam; applying a first digital filter to cut off signals around the first original origin and performing an inverse Fourier transform on the result; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a second angle between a second reference beam and a second object beam; and applying a second digital filter to cut off signals around the second original origin and performing an inverse Fourier transform on the result, wherein digitally recording the first spatially-heterodyned hologram is completed before digitally recording the second spatially-heterodyned hologram and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

Faster processing of multiple spatially-heterodyned direct to digital holograms

DOEpatents

Hanson, Gregory R [Clinton, TN; Bingham, Philip R [Knoxville, TN

2008-09-09

Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms. A method includes of obtaining multiple spatially-heterodyned holograms, includes: digitally recording a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; digitally recording a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a first angle between a first reference beam and a first object beam; applying a first digital filter to cut off signals around the first original origin and performing an inverse Fourier transform on the result; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram including spatial heterodyne fringes in Fourier space to sit on top of a spatial-heterodyne carrier frequency defined as a second angle between a second reference beam and a second object beam; and applying a second digital filter to cut off signals around the second original origin and performing an inverse Fourier transform on the result, wherein digitally recording the first spatially-heterodyned hologram is completed before digitally recording the second spatially-heterodyned hologram and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

Simplified paraboloid phase model-based phase tracker for demodulation of a single complex fringe.

PubMed

He, A; Deepan, B; Quan, C

2017-09-01

A regularized phase tracker (RPT) is an effective method for demodulation of single closed-fringe patterns. However, lengthy calculation time, specially designed scanning strategy, and sign-ambiguity problems caused by noise and saddle points reduce its effectiveness, especially for demodulating large and complex fringe patterns. In this paper, a simplified paraboloid phase model-based regularized phase tracker (SPRPT) is proposed. In SPRPT, first and second phase derivatives are pre-determined by the density-direction-combined method and discrete higher-order demodulation algorithm, respectively. Hence, cost function is effectively simplified to reduce the computation time significantly. Moreover, pre-determined phase derivatives improve the robustness of the demodulation of closed, complex fringe patterns. Thus, no specifically designed scanning strategy is needed; nevertheless, it is robust against the sign-ambiguity problem. The paraboloid phase model also assures better accuracy and robustness against noise. Both the simulated and experimental fringe patterns (obtained using electronic speckle pattern interferometry) are used to validate the proposed method, and a comparison of the proposed method with existing RPT methods is carried out. The simulation results show that the proposed method has achieved the highest accuracy with less computational time. The experimental result proves the robustness and the accuracy of the proposed method for demodulation of noisy fringe patterns and its feasibility for static and dynamic applications.

Analysis of the Localization of Michelson Interferometer Fringes Using Fourier Optics and Temporal Coherence

ERIC Educational Resources Information Center

Narayanamurthy, C. S.

2009-01-01

Fringes formed in a Michelson interferometer never localize in any plane, in the detector plane and in the localization plane. Instead, the fringes are assumed to localize at infinity. Except for some explanation in "Principles of Optics" by Born and Wolf (1964 (New York: Macmillan)), the fringe localization phenomena of Michelson's interferometer…

Novel method of detecting movement of the interference fringes using one-dimensional PSD.

PubMed

Wang, Qi; Xia, Ji; Liu, Xu; Zhao, Yong

2015-06-02

In this paper, a method of using a one-dimensional position-sensitive detector (PSD) by replacing charge-coupled device (CCD) to measure the movement of the interference fringes is presented first, and its feasibility is demonstrated through an experimental setup based on the principle of centroid detection. Firstly, the centroid position of the interference fringes in a fiber Mach-Zehnder (M-Z) interferometer is solved in theory, showing it has a higher resolution and sensitivity. According to the physical characteristics and principles of PSD, a simulation of the interference fringe's phase difference in fiber M-Z interferometers and PSD output is carried out. Comparing the simulation results with the relationship between phase differences and centroid positions in fiber M-Z interferometers, the conclusion that the output of interference fringes by PSD is still the centroid position is obtained. Based on massive measurements, the best resolution of the system is achieved with 5.15, 625 μm. Finally, the detection system is evaluated through setup error analysis and an ultra-narrow-band filter structure. The filter structure is configured with a one-dimensional photonic crystal containing positive and negative refraction material, which can eliminate background light in the PSD detection experiment. This detection system has a simple structure, good stability, high precision and easily performs remote measurements, which makes it potentially useful in material small deformation tests, refractivity measurements of optical media and optical wave front detection.

Theoretical and experimental study of low-finesse extrinsic Fabry-Perot interferometric fiber optic sensors

NASA Astrophysics Data System (ADS)

Han, Ming

In this dissertation, detailed and systematic theoretical and experimental study of low-finesse extrinsic Fabry-Perot interferometric (EFPI) fiber optic sensors together with their signal processing methods for white-light systems are presented. The work aims to provide a better understanding of the operational principle of EFPI fiber optic sensors, and is useful and important in the design, optimization, fabrication and application of single mode fiber(SMF) EFPI (SMF-EFPI) and multimode fiber (MMF) EFPI (MMF-EFPI) sensor systems. The cases for SMF-EFPI and MMF-EFPI sensors are separately considered. In the analysis of SMF-EFPI sensors, the light transmitted in the fiber is approximated by a Gaussian beam and the obtained spectral transfer function of the sensors includes an extra phase shift due to the light coupling in the fiber end-face. This extra phase shift has not been addressed by previous researchers and is of great importance for high accuracy and high resolution signal processing of white-light SMF-EFPI systems. Fringe visibility degradation due to gap-length increase and sensor imperfections is studied. The results indicate that the fringe visibility of a SMF-EFPI sensor is relatively insensitive to the gap-length change and sensor imperfections. Based on the spectral fringe pattern predicated by the theory of SMF-EFPI sensors, a novel curve fitting signal processing method (Type 1 curve-fitting method) is presented for white-light SMF-EFPI sensor systems. Other spectral domain signal processing methods including the wavelength-tracking, the Type 2-3 curve fitting, Fourier transform, and two-point interrogation methods are reviewed and systematically analyzed. Experiments were carried out to compare the performances of these signal processing methods. The results have shown that the Type 1 curve fitting method achieves high accuracy, high resolution, large dynamic range, and the capability of absolute measurement at the same time, while others either have less resolution, or are not capable of absolute measurement. Previous mathematical models for MMF-EFPI sensors are all based on geometric optics; therefore their applications have many limitations. In this dissertation, a modal theory is developed that can be used in any situations and is more accurate. The mathematical description of the spectral fringes of MMF-EFPI sensors is obtained by the modal theory. Effect on the fringe visibility of system parameters, including the sensor head structure, the fiber parameters, and the mode power distribution in the MMF of the MMF-EFPI sensors, is analyzed. Experiments were carried out to validate the theory. Fundamental mechanism that causes the degradation of the fringe visibility in MMF-EFPI sensors are revealed. It is shown that, in some situations at which the fringe visibility is important and difficult to achieve, a simple method of launching the light into the MMF-EFPI sensor system from the output of a SMF could be used to improve the fringe visibility and to ease the fabrication difficulties of MMF-EFPI sensors. Signal processing methods that are well-understood in white-light SMF-EFPI sensor systems may exhibit new aspects when they are applied to white-light MMF-EFPI sensor systems. This dissertation reveals that the variations of mode power distribution (MPD) in the MMF could cause phase variations of the spectral fringes from a MMF-EFPI sensor and introduce measurement errors for a signal processing method in which the phase information is used. This MPD effect on the wavelength-tracking method in white-light MMF-EFPI sensors is theoretically analyzed. The fringe phases changes caused by MPD variations were experimentally observed and thus the MFD effect is validated.

Digital fringe projection for hand surface coordinate variation analysis caused by osteoarthritis

NASA Astrophysics Data System (ADS)

Nor Haimi, Wan Mokhdzani Wan; Hau Tan, Cheek; Retnasamy, Vithyacharan; Vairavan, Rajendaran; Sauli, Zaliman; Roshidah Yusof, Nor; Hambali, Nor Azura Malini Ahmad; Aziz, Muhammad Hafiz Ab; Bakhit, Ahmad Syahir Ahmad

2017-11-01

Hand osteoarthritis is one of the most common forms of arthritis which impact millions of people worldwide. The disabling problem occurs when the protective cartilage on the boundaries of bones wear off over time. Currently, in order to identify hand osteoarthritis, special instruments namely X-ray scanning and MRI are used for the detection but it also has its limitations such as radiation exposure and can be quite costly. In this work, an optical metrology system based on digital fringe projection which comprises of an LCD projector, CCD camera and a personal computer has been developed to anticipate abnormal growth or deformation on the joints of the hand which are common symptoms of osteoarthritis. The main concept of this optical metrology system is to apply structured light as imaging source for surface change detection. The imaging source utilizes fringe patterns generated by C++ programming and is shifted by 3 phase shifts based on the 3 steps 2 shifts method. Phase wrapping technique and analysis were applied in order to detect the deformation of live subjects. The result has demonstrated a successful method of hand deformation detection based on the pixel tracking differences of a normal and deformed state.

Quantitative holographic interferometry applied to combustion and compressible flow research

NASA Astrophysics Data System (ADS)

Bryanston-Cross, Peter J.; Towers, D. P.

1993-03-01

The application of holographic interferometry to phase object analysis is described. Emphasis has been given to a method of extracting quantitative information automatically from the interferometric fringe data. To achieve this a carrier frequency has been added to the holographic data. This has made it possible, firstly to form a phase map using a fast Fourier transform (FFT) algorithm. Then to `solve,' or unwrap, this image to give a contiguous density map using a minimum weight spanning tree (MST) noise immune algorithm, known as fringe analysis (FRAN). Applications of this work to a burner flame and a compressible flow are presented. In both cases the spatial frequency of the fringes exceed the resolvable limit of conventional digital framestores. Therefore, a flatbed scanner with a resolution of 3200 X 2400 pixels has been used to produce very high resolution digital images from photographs. This approach has allowed the processing of data despite the presence of caustics, generated by strong thermal gradients at the edge of the combustion field. A similar example is presented from the analysis of a compressible transonic flow in the shock wave and trailing edge regions.

Modular digital holographic fringe data processing system

NASA Technical Reports Server (NTRS)

Downward, J. G.; Vavra, P. C.; Schebor, F. S.; Vest, C. M.

1985-01-01

A software architecture suitable for reducing holographic fringe data into useful engineering data is developed and tested. The results, along with a detailed description of the proposed architecture for a Modular Digital Fringe Analysis System, are presented.

Unsaturated flow characterization utilizing water content data collected within the capillary fringe

USGS Publications Warehouse

Baehr, Arthur; Reilly, Timothy J.

2014-01-01

An analysis is presented to determine unsaturated zone hydraulic parameters based on detailed water content profiles, which can be readily acquired during hydrological investigations. Core samples taken through the unsaturated zone allow for the acquisition of gravimetrically determined water content data as a function of elevation at 3 inch intervals. This dense spacing of data provides several measurements of the water content within the capillary fringe, which are utilized to determine capillary pressure function parameters via least-squares calibration. The water content data collected above the capillary fringe are used to calculate dimensionless flow as a function of elevation providing a snapshot characterization of flow through the unsaturated zone. The water content at a flow stagnation point provides an in situ estimate of specific yield. In situ determinations of capillary pressure function parameters utilizing this method, together with particle-size distributions, can provide a valuable supplement to data libraries of unsaturated zone hydraulic parameters. The method is illustrated using data collected from plots within an agricultural research facility in Wisconsin.

Single-shot real-time three dimensional measurement based on hue-height mapping

NASA Astrophysics Data System (ADS)

Wan, Yingying; Cao, Yiping; Chen, Cheng; Fu, Guangkai; Wang, Yapin; Li, Chengmeng

2018-06-01

A single-shot three-dimensional (3D) measurement based on hue-height mapping is proposed. The color fringe pattern is encoded by three sinusoidal fringes with the same frequency but different shifting phase into red (R), green (G) and blue (B) color channels, respectively. It is found that the hue of the captured color fringe pattern on the reference plane maintains monotonic in one period even it has the color crosstalk. Thus, unlike the traditional color phase shifting technique, the hue information is utilized to decode the color fringe pattern and map to the pixels of the fringe displacement in the proposed method. Because the monotonicity of the hue is limited within one period, displacement unwrapping is proposed to obtain the continuous displacement that is finally used to map to the height distribution. This method directly utilizes the hue under the effect of color crosstalk for mapping the height so that no color calibration is involved. Also, as it requires only single shot deformed color fringe pattern, this method can be applied into the real-time or dynamic 3D measurements.

Determination of skeleton and sign map for phase obtaining from a single ESPI image

NASA Astrophysics Data System (ADS)

Yang, Xia; Yu, Qifeng; Fu, Sihua

2009-06-01

A robust method of determining the sign map and skeletons for ESPI images is introduced in this paper. ESPI images have high speckle noise which makes it difficult to obtain the fringe information, especially from a single image. To overcome the effects of high speckle noise, local directional computing windows are designed according to the fringe directions. Then by calculating the gradients from the filtered image in directional windows, sign map and good skeletons can be determined robustly. Based on the sign map, single image phase-extracting methods such as quadrature transform can be improved. And based on skeletons, fringe phases can be obtained directly by normalization methods. Experiments show that this new method is robust and effective for extracting phase from a single ESPI fringe image.

A procedural method for express bus-fringe parking transit planning.

DOT National Transportation Integrated Search

1976-01-01

The report illustrates a procedural method for planning express bus-fringe parking transit services - a method built upon the findings from previous research, including disaggregate travel choice models and planning guidelines. The methodology addres...

Fringe pattern demodulation with a two-dimensional digital phase-locked loop algorithm.

PubMed

Gdeisat, Munther A; Burton, David R; Lalor, Michael J

2002-09-10

A novel technique called a two-dimensional digital phase-locked loop (DPLL) for fringe pattern demodulation is presented. This algorithm is more suitable for demodulation of fringe patterns with varying phase in two directions than the existing DPLL techniques that assume that the phase of the fringe patterns varies only in one direction. The two-dimensional DPLL technique assumes that the phase of a fringe pattern is continuous in both directions and takes advantage of the phase continuity; consequently, the algorithm has better noise performance than the existing DPLL schemes. The two-dimensional DPLL algorithm is also suitable for demodulation of fringe patterns with low sampling rates, and it outperforms the Fourier fringe analysis technique in this aspect.

Comparisons between real and complex Gauss wavelet transform methods of three-dimensional shape reconstruction

NASA Astrophysics Data System (ADS)

Xu, Luopeng; Dan, Youquan; Wang, Qingyuan

2015-10-01

The continuous wavelet transform (CWT) introduces an expandable spatial and frequency window which can overcome the inferiority of localization characteristic in Fourier transform and windowed Fourier transform. The CWT method is widely applied in the non-stationary signal analysis field including optical 3D shape reconstruction with remarkable performance. In optical 3D surface measurement, the performance of CWT for optical fringe pattern phase reconstruction usually depends on the choice of wavelet function. A large kind of wavelet functions of CWT, such as Mexican Hat wavelet, Morlet wavelet, DOG wavelet, Gabor wavelet and so on, can be generated from Gauss wavelet function. However, so far, application of the Gauss wavelet transform (GWT) method (i.e. CWT with Gauss wavelet function) in optical profilometry is few reported. In this paper, the method using GWT for optical fringe pattern phase reconstruction is presented first and the comparisons between real and complex GWT methods are discussed in detail. The examples of numerical simulations are also given and analyzed. The results show that both the real GWT method along with a Hilbert transform and the complex GWT method can realize three-dimensional surface reconstruction; and the performance of reconstruction generally depends on the frequency domain appearance of Gauss wavelet functions. For the case of optical fringe pattern of large phase variation with position, the performance of real GWT is better than that of complex one due to complex Gauss series wavelets existing frequency sidelobes. Finally, the experiments are carried out and the experimental results agree well with our theoretical analysis.

Complete chirp analysis of a gain-switched pulse using an interferometric two-photon absorption autocorrelation.

PubMed

Chin, Sang Hoon; Kim, Young Jae; Song, Ho Seong; Kim, Dug Young

2006-10-10

We propose a simple but powerful scheme for the complete analysis of the frequency chirp of a gain-switched optical pulse using a fringe-resolved interferometric two-photon absorption autocorrelator. A frequency chirp imposed on the gain-switched pulse from a laser diode was retrieved from both the intensity autocorrelation trace and the envelope of the second-harmonic interference fringe pattern. To verify the accuracy of the proposed phase retrieval method, we have performed an optical pulse compression experiment by using dispersion-compensating fibers with different lengths. We have obtained close agreement by less than a 1% error between the compressed pulse widths and numerically calculated pulse widths.

The Impact of Masker Fringe and Masker Sparial Uncertainty on Sound Localization

DTIC Science & Technology

2010-09-01

spatial uncertainty on sound localization and to examine how such effects might be related to binaural detection and informational masking. 2 Methods...results from the binaural detection literature and suggest that a longer duration fringe provides a more robust context against which to judge the...results from the binaural detection literature, which suggest that forward masker fringe provides a greater benefit than backward masker fringe [2]. The

Adaptive correction to the speckle correlation fringes by using a twisted-nematic liquid-crystal display.

PubMed

Hack, Erwin; Gundu, Phanindra Narayan; Rastogi, Pramod

2005-05-10

An innovative technique for reducing speckle noise and improving the intensity profile of the speckle correlation fringes is presented. The method is based on reducing the range of the modulation intensity values of the speckle interference pattern. After the fringe pattern is corrected adaptively at each pixel, a simple morphological filtering of the fringes is sufficient to obtain smoothed fringes. The concept is presented both analytically and by simulation by using computer-generated speckle patterns. The experimental verification is performed by using an amplitude-only spatial light modulator (SLM) in a conventional electronic speckle pattern interferometry setup. The optical arrangement for tuning a commercially available LCD array for amplitude-only behavior is described. The method of feedback to the LCD SLM to modulate the intensity of the reference beam in order to reduce the modulation intensity values is explained, and the resulting fringe pattern and increase in the signal-to-noise ratio are discussed.

Eliminating the zero spectrum in Fourier transform profilometry using empirical mode decomposition.

PubMed

Li, Sikun; Su, Xianyu; Chen, Wenjing; Xiang, Liqun

2009-05-01

Empirical mode decomposition is introduced into Fourier transform profilometry to extract the zero spectrum included in the deformed fringe pattern without the need for capturing two fringe patterns with pi phase difference. The fringe pattern is subsequently demodulated using a standard Fourier transform profilometry algorithm. With this method, the deformed fringe pattern is adaptively decomposed into a finite number of intrinsic mode functions that vary from high frequency to low frequency by means of an algorithm referred to as a sifting process. Then the zero spectrum is separated from the high-frequency components effectively. Experiments validate the feasibility of this method.

Phase retrieval in digital speckle pattern interferometry by application of two-dimensional active contours called snakes.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2006-03-20

We propose a novel approach to retrieving the phase map coded by a single closed-fringe pattern in digital speckle pattern interferometry, which is based on the estimation of the local sign of the quadrature component. We obtain the estimate by calculating the local orientation of the fringes that have previously been denoised by a weighted smoothing spline method. We carry out the procedure of sign estimation by determining the local abrupt jumps of size pi in the orientation field of the fringes and by segmenting the regions defined by these jumps. The segmentation method is based on the application of two-dimensional active contours (snakes), with which one can also estimate absent jumps, i.e., those that cannot be detected from the local orientation of the fringes. The performance of the proposed phase-retrieval technique is evaluated for synthetic and experimental fringes and compared with the results obtained with the spiral-phase- and Fourier-transform methods.

A STUDY OF FRINGE BENEFITS.

DTIC Science & Technology

Fringe benefits as a term was coined by the War Labor Board during World War II to describe the various indirect benefits which industry had devised...trends for the future. The appendix contains an analysis of comparative costs of fringe benefits in industry and the military services. (Author)

Local denoising of digital speckle pattern interferometry fringes by multiplicative correlation and weighted smoothing splines.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2005-05-10

We evaluate the use of smoothing splines with a weighted roughness measure for local denoising of the correlation fringes produced in digital speckle pattern interferometry. In particular, we also evaluate the performance of the multiplicative correlation operation between two speckle patterns that is proposed as an alternative procedure to generate the correlation fringes. It is shown that the application of a normalization algorithm to the smoothed correlation fringes reduces the excessive bias generated in the previous filtering stage. The evaluation is carried out by use of computer-simulated fringes that are generated for different average speckle sizes and intensities of the reference beam, including decorrelation effects. A comparison with filtering methods based on the continuous wavelet transform is also presented. Finally, the performance of the smoothing method in processing experimental data is illustrated.

Controlling Fringe Sensitivity of Electro-Optic Holography Systems Using Laser Diode Current Modulation

NASA Technical Reports Server (NTRS)

Bybee, Shannon J.

2001-01-01

Electro-Optic Holography (EOH) is a non-intrusive, laser-based, displacement measurement technique capable of static and dynamic displacement measurements. EOH is an optical interference technique in which fringe patterns that represent displacement contour maps are generated. At excessively large displacements the fringe density may be so great that individual fringes are not resolvable using typical EOH techniques. This thesis focuses on the development and implementation of a method for controlling the sensitivity of the EOH system. This method is known as Frequency Translated Electro-Optic Holography (FTEOH). It was determined that by modulating the current source of the laser diode at integer multiples of the object vibration, the fringe pattern is governed by higher order Bessel function of the first kind and the number of fringes that represent a given displacement can be controlled. The reduction of fringes is theoretically unlimited but physically limited by the frequency bandwidth of the signal generator, providing modulation to the laser diode. Although this research technique has been verified theoretically and experimentally in this thesis, due to the current laser diode capabilities it is a tedious and time consuming process to acquire data using the FTEOH technique.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, John M.; Onar, Omer C.; Chinthavali, Madhu

Various noncontacting methods of plug-in electric vehicle charging are either under development or now deployed as aftermarket options in the light-duty automotive market. Wireless power transfer (WPT) is now the accepted term for wireless charging and is used synonymously for inductive power transfer and magnetic resonance coupling. WPT technology is in its infancy; standardization is lacking, especially on interoperability, center frequency selection, magnetic fringe field suppression, and the methods employed for power flow regulation. This paper proposes a new analysis concept for power flow in WPT in which the primary provides frequency selection and the tuned secondary, with its resemblancemore » to a power transmission network having a reactive power voltage control, is analyzed as a transmission network. Analysis is supported with experimental data taken from Oak Ridge National Laboratory s WPT apparatus. Lastly, this paper also provides an experimental evidence for frequency selection, fringe field assessment, and the need for low-latency communications in the feedback path.« less

Dual exposure interferometry. [gas dynamics and flow visualization

NASA Technical Reports Server (NTRS)

Smeets, G.; George, A.

1982-01-01

The application of dual exposure differential interferometry to gas dynamics and flow visualization is discussed. A differential interferometer with Wallaston prisms can produce two complementary interference fringe systems, depending on the polarization of the incident light. If these two systems are superimposed on a film, with one exposure during a phenomenon, the other before or after, the phenomenon will appear on a uniform background. By regulating the interferometer to infinite fringe distance, a resolution limit of approximately lambda/500 can be obtained in the quantitative analysis of weak phase objects. This method was successfully applied to gas dynamic investigations.

Phase retrieval from the phase-shift moiré fringe patterns in simultaneous dual-wavelength interferometry

NASA Astrophysics Data System (ADS)

Cheng, Jinlong; Gao, Zhishan; Bie, Shuyou; Dou, Yimeng; Ni, Ruihu; Yuan, Qun

2018-02-01

Simultaneous dual-wavelength interferometry (SDWI) could extend the measured range of each single-wavelength interferometry. The moiré fringe generated in SDWI indirectly represents the information of the measured long synthetic-wavelength ({λ }{{S}}) phase, thus the phase demodulation is rather arduous. To address this issue, we present a method to convert the moiré fringe pattern into a synthetic-wavelength interferogram (moiré to synthetic-wavelength, MTS). After the square of the moiré fringe pattern in the MTS method, the additive moiré pattern is turned into a multiplicative one. And the synthetic-wavelength interferogram could be obtained by a low-pass filtering in spectrum of the multiplicative moiré fringe pattern. Therefore, when the dual-wavelength interferometer is implemented with the π/2 phase shift at {λ }{{S}}, a sequence of synthetic-wavelength phase-shift interferograms with π/2 phase shift could be obtained after the MTS method processing on the captured moiré fringe patterns. And then the synthetic-wavelength phase could be retrieved by the conventional phase-shift algorithm. Compared with other methods in SDWI, the proposed MTS approach could reduce the restriction of the phase shift and frame numbers for the adoption of the conventional phase-shift algorithm. Following, numerical simulations are executed to evaluate the performance of the MTS method in processing time, frames of interferograms and the phase shift error compensation. And the necessary linear carrier for MTS method is less than 0.11 times of the traditional dual-wavelength spatial-domain Fourier transform method. Finally, the deviations for MTS method in experiment are 0.97% for a step with the height of 7.8 μm and 1.11% for a Fresnel lens with the step height of 6.2328 μm.

Fringing in MonoCam Y4 filter images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brooks, J.; Fisher-Levine, M.; Nomerotski, A.

Here, we study the fringing patterns observed in MonoCam, a camera with a single Large Synoptic Survey Telescope (LSST) CCD sensor. Images were taken at the U.S. Naval Observatory in Flagstaff, Arizona (NOFS) employing its 1.3 m telescope and an LSST y4 filter. Fringing occurs due to the reflection of infrared light (700 nm or larger) from the bottom surface of the CCD which constructively or destructively interferes with the incident light to produce a net "fringe" pattern which is superimposed on all images taken. Emission lines from the atmosphere, dominated by hydroxyl (OH) spectra, can change in their relativemore » intensities as the night goes on, producing different fringe patterns in the images taken. We found through several methods that the general shape of the fringe patterns remained constant, though with slight changes in the amplitude and phase of the fringes. Lastly, we also found that a superposition of fringes from two monochromatic lines taken in the lab offered a reasonable description of the sky data.« less

Fringing in MonoCam Y4 filter images

DOE PAGES

Brooks, J.; Fisher-Levine, M.; Nomerotski, A.

2017-05-05

Here, we study the fringing patterns observed in MonoCam, a camera with a single Large Synoptic Survey Telescope (LSST) CCD sensor. Images were taken at the U.S. Naval Observatory in Flagstaff, Arizona (NOFS) employing its 1.3 m telescope and an LSST y4 filter. Fringing occurs due to the reflection of infrared light (700 nm or larger) from the bottom surface of the CCD which constructively or destructively interferes with the incident light to produce a net "fringe" pattern which is superimposed on all images taken. Emission lines from the atmosphere, dominated by hydroxyl (OH) spectra, can change in their relativemore » intensities as the night goes on, producing different fringe patterns in the images taken. We found through several methods that the general shape of the fringe patterns remained constant, though with slight changes in the amplitude and phase of the fringes. Lastly, we also found that a superposition of fringes from two monochromatic lines taken in the lab offered a reasonable description of the sky data.« less

3D silicon breast surface mapping via structured light profilometry

NASA Astrophysics Data System (ADS)

Vairavan, R.; Ong, N. R.; Sauli, Z.; Kirtsaeng, S.; Sakuntasathien, S.; Shahimin, M. M.; Alcain, J. B.; Lai, S. L.; Paitong, P.; Retnasamy, V.

2017-09-01

Digital fringe projection technique is one of the promising optical methods for 3D surface imaging as it demonstrates non contact and non invasive characteristics. The potential of this technique matches the requirement for human body evaluation, as it is vital for disease diagnosis and for treatment option selection. Thus, the digital fringe projection has addressed this requirement with its wide clinical related application and studies. However, the application of this technique for 3D surface mapping of the breast is very minimal. Hence, in this work, the application of digital fringe projection for 3D breast surface mapping is reported. Phase shift fringe projection technique was utilized to perform the 3D breast surface mapping. Maiden results have confirmed the feasibility of using the digital fringe projection method for 3D surface mapping of the breast and it can be extended for breast cancer detection.

Analysis of the localization of Michelson interferometer fringes using Fourier optics and temporal coherence

NASA Astrophysics Data System (ADS)

Narayanamurthy, C. S.

2009-01-01

Fringes formed in a Michelson interferometer never localize in any plane, in the detector plane and in the localization plane. Instead, the fringes are assumed to localize at infinity. Except for some explanation in Principles of Optics by Born and Wolf (1964 (New York: Macmillan)), the fringe localization phenomena of Michelson's interferometer have never been analysed seriously in any book. Because Michelson's interferometer is one of the important and fundamental optical experiments taught at both undergraduate and graduate levels, it would be appropriate to explain the localization of these fringes. In this paper, we analyse the localization of Michelson interferometer fringes using Fourier optics and temporal coherence, and show that they never localize at any plane even at infinity.

Full-Field Calibration of Color Camera Chromatic Aberration using Absolute Phase Maps.

PubMed

Liu, Xiaohong; Huang, Shujun; Zhang, Zonghua; Gao, Feng; Jiang, Xiangqian

2017-05-06

The refractive index of a lens varies for different wavelengths of light, and thus the same incident light with different wavelengths has different outgoing light. This characteristic of lenses causes images captured by a color camera to display chromatic aberration (CA), which seriously reduces image quality. Based on an analysis of the distribution of CA, a full-field calibration method based on absolute phase maps is proposed in this paper. Red, green, and blue closed sinusoidal fringe patterns are generated, consecutively displayed on an LCD (liquid crystal display), and captured by a color camera from the front viewpoint. The phase information of each color fringe is obtained using a four-step phase-shifting algorithm and optimum fringe number selection method. CA causes the unwrapped phase of the three channels to differ. These pixel deviations can be computed by comparing the unwrapped phase data of the red, blue, and green channels in polar coordinates. CA calibration is accomplished in Cartesian coordinates. The systematic errors introduced by the LCD are analyzed and corrected. Simulated results show the validity of the proposed method and experimental results demonstrate that the proposed full-field calibration method based on absolute phase maps will be useful for practical software-based CA calibration.

Measurement of the configuration of a concave surface by the interference of reflected light

NASA Technical Reports Server (NTRS)

Kumazawa, T.; Sakamoto, T.; Shida, S.

1985-01-01

A method whereby a concave surface is irradiated with coherent light and the resulting interference fringes yield information on the concave surface is described. This method can be applied to a surface which satisfies the following conditions: (1) the concave face has a mirror surface; (2) the profile of the face is expressed by a mathematical function with a point of inflection. In this interferometry, multilight waves reflected from the concave surface interfere and make fringes wherever the reflected light propagates. Interference fringe orders. Photographs of the fringe patterns for a uniformly loaded thin silicon plate clamped at the edge are shown experimentally. The experimental and the theoretical values of the maximum optical path difference show good agreement. This simple method can be applied to obtain accurate information on concave surfaces.

Highly noise-tolerant hybrid algorithm for phase retrieval from a single-shot spatial carrier fringe pattern

NASA Astrophysics Data System (ADS)

Dong, Zhichao; Cheng, Haobo

2018-01-01

A highly noise-tolerant hybrid algorithm (NTHA) is proposed in this study for phase retrieval from a single-shot spatial carrier fringe pattern (SCFP), which effectively combines the merits of spatial carrier phase shift method and two dimensional continuous wavelet transform (2D-CWT). NTHA firstly extracts three phase-shifted fringe patterns from the SCFP with one pixel malposition; then calculates phase gradients by subtracting the reference phase from the other two target phases, which are retrieved respectively from three phase-shifted fringe patterns by 2D-CWT; finally, reconstructs the phase map by a least square gradient integration method. Its typical characters include but not limited to: (1) doesn't require the spatial carrier to be constant; (2) the subtraction mitigates edge errors of 2D-CWT; (3) highly noise-tolerant, because not only 2D-CWT is noise-insensitive, but also the noise in the fringe pattern doesn't directly take part in the phase reconstruction as in previous hybrid algorithm. Its feasibility and performances are validated extensively by simulations and contrastive experiments to temporal phase shift method, Fourier transform and 2D-CWT methods.

Demodulation of moire fringes in digital holographic interferometry using an extended Kalman filter.

PubMed

Ramaiah, Jagadesh; Rastogi, Pramod; Rajshekhar, Gannavarpu

2018-03-10

This paper presents a method for extracting multiple phases from a single moire fringe pattern in digital holographic interferometry. The method relies on component separation using singular value decomposition and an extended Kalman filter for demodulating the moire fringes. The Kalman filter is applied by modeling the interference field locally as a multi-component polynomial phase signal and extracting the associated multiple polynomial coefficients using the state space approach. In addition to phase, the corresponding multiple phase derivatives can be simultaneously extracted using the proposed method. The applicability of the proposed method is demonstrated using simulation and experimental results.

Model-based multi-fringe interferometry using Zernike polynomials

NASA Astrophysics Data System (ADS)

Gu, Wei; Song, Weihong; Wu, Gaofeng; Quan, Haiyang; Wu, Yongqian; Zhao, Wenchuan

2018-06-01

In this paper, a general phase retrieval method is proposed, which is based on one single interferogram with a small amount of fringes (either tilt or power). Zernike polynomials are used to characterize the phase to be measured; the phase distribution is reconstructed by a non-linear least squares method. Experiments show that the proposed method can obtain satisfactory results compared to the standard phase-shifting interferometry technique. Additionally, the retrace errors of proposed method can be neglected because of the few fringes; it does not need any auxiliary phase shifting facilities (low cost) and it is easy to implement without the process of phase unwrapping.

Integration of fringe projection and two-dimensional digital image correlation for three-dimensional displacements measurements

NASA Astrophysics Data System (ADS)

Felipe-Sesé, Luis; López-Alba, Elías; Siegmann, Philip; Díaz, Francisco A.

2016-12-01

A low-cost approach for three-dimensional (3-D) full-field displacement measurement is applied for the analysis of large displacements involved in two different mechanical events. The method is based on a combination of fringe projection and two-dimensional digital image correlation (DIC) techniques. The two techniques have been employed simultaneously using an RGB camera and a color encoding method; therefore, it is possible to measure in-plane and out-of-plane displacements at the same time with only one camera even at high speed rates. The potential of the proposed methodology has been employed for the analysis of large displacements during contact experiments in a soft material block. Displacement results have been successfully compared with those obtained using a 3D-DIC commercial system. Moreover, the analysis of displacements during an impact test on a metal plate was performed to emphasize the application of the methodology for dynamics events. Results show a good level of agreement, highlighting the potential of FP + 2D DIC as low-cost alternative for the analysis of large deformations problems.

Optical phase distribution evaluation by using zero order Generalized Morse Wavelet

NASA Astrophysics Data System (ADS)

Kocahan, Özlem; Elmas, Merve Naz; Durmuş, ćaǧla; Coşkun, Emre; Tiryaki, Erhan; Özder, Serhat

2017-02-01

When determining the phase from the projected fringes by using continuous wavelet transform (CWT), selection of wavelet is an important step. A new wavelet for phase retrieval from the fringe pattern with the spatial carrier frequency in the x direction is presented. As a mother wavelet, zero order generalized Morse wavelet (GMW) is chosen because of the flexible spatial and frequency localization property, and it is exactly analytic. In this study, GMW method is explained and numerical simulations are carried out to show the validity of this technique for finding the phase distributions. Results for the Morlet and Paul wavelets are compared with the results of GMW analysis.

Wavefront reversal technique for self-referencing collimation testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hii, King Ung; Kwek, Kuan Hiang

2010-02-01

We present a wavefront reversal technique to produce a dual-field fringe pattern for self-referencing collimation testing in wedge-plate lateral-shear interferometry. The method requires only a suitably placed cubic beam splitter to produce two replicas of the fringe field formed by the wedge-plate lateral-shear interferometer. One of the replicas has a fringe pattern that is the reverse of the other. With these two fringe fields, the collimation testing has a built-in reference, and the detection sensitivity is twice that of a single-wedge-plate technique.

Fringes in FTIR spectroscopy revisited: understanding and modelling fringes in infrared spectroscopy of thin films.

PubMed

Konevskikh, Tatiana; Ponossov, Arkadi; Blümel, Reinhold; Lukacs, Rozalia; Kohler, Achim

2015-06-21

The appearance of fringes in the infrared spectroscopy of thin films seriously hinders the interpretation of chemical bands because fringes change the relative peak heights of chemical spectral bands. Thus, for the correct interpretation of chemical absorption bands, physical properties need to be separated from chemical characteristics. In the paper at hand we revisit the theory of the scattering of infrared radiation at thin absorbing films. Although, in general, scattering and absorption are connected by a complex refractive index, we show that for the scattering of infrared radiation at thin biological films, fringes and chemical absorbance can in good approximation be treated as additive. We further introduce a model-based pre-processing technique for separating fringes from chemical absorbance by extended multiplicative signal correction (EMSC). The technique is validated by simulated and experimental FTIR spectra. It is further shown that EMSC, as opposed to other suggested filtering methods for the removal of fringes, does not remove information related to chemical absorption.

Zero-fringe demodulation method based on location-dependent birefringence dispersion in polarized low-coherence interferometry.

PubMed

Wang, Shuang; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Yin, Jinde; Qin, Zunqi; Zou, Shengliang

2014-04-01

We present a high precision and fast speed demodulation method for a polarized low-coherence interferometer with location-dependent birefringence dispersion. Based on the characteristics of location-dependent birefringence dispersion and five-step phase-shifting technology, the method accurately retrieves the peak position of zero-fringe at the central wavelength, which avoids the fringe order ambiguity. The method processes data only in the spatial domain and reduces the computational load greatly. We successfully demonstrated the effectiveness of the proposed method in an optical fiber Fabry-Perot barometric pressure sensing experiment system. Measurement precision of 0.091 kPa was realized in the pressure range of 160 kPa, and computation time was improved by 10 times compared to the traditional phase-based method that requires Fourier transform operation.

Nondestructive evaluation of turbine blades vibrating in resonant modes

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Ahmadshahi, Mansour A.

1991-12-01

The paper presents the analysis of the strain distribution of turbine blades. The holographic moire technique is used in conjunction with computer analysis of the fringes. The application of computer fringe analysis technique reduces the number of holograms to be recorded to two. Stroboscopic illumination is used to record the patterns. Strains and stresses are computed.

Primary-Side Power Flow Control of Wireless Power Transfer for Electric Vehicle Charging

DOE PAGES

Miller, John M.; Onar, Omer C.; Chinthavali, Madhu

2014-12-22

Various noncontacting methods of plug-in electric vehicle charging are either under development or now deployed as aftermarket options in the light-duty automotive market. Wireless power transfer (WPT) is now the accepted term for wireless charging and is used synonymously for inductive power transfer and magnetic resonance coupling. WPT technology is in its infancy; standardization is lacking, especially on interoperability, center frequency selection, magnetic fringe field suppression, and the methods employed for power flow regulation. This paper proposes a new analysis concept for power flow in WPT in which the primary provides frequency selection and the tuned secondary, with its resemblancemore » to a power transmission network having a reactive power voltage control, is analyzed as a transmission network. Analysis is supported with experimental data taken from Oak Ridge National Laboratory s WPT apparatus. Lastly, this paper also provides an experimental evidence for frequency selection, fringe field assessment, and the need for low-latency communications in the feedback path.« less

Real-time fringe pattern demodulation with a second-order digital phase-locked loop.

PubMed

Gdeisat, M A; Burton, D R; Lalor, M J

2000-10-10

The use of a second-order digital phase-locked loop (DPLL) to demodulate fringe patterns is presented. The second-order DPLL has better tracking ability and more noise immunity than the first-order loop. Consequently, the second-order DPLL is capable of demodulating a wider range of fringe patterns than the first-order DPLL. A basic analysis of the first- and the second-order loops is given, and a performance comparison between the first- and the second-order DPLL's in analyzing fringe patterns is presented. The implementation of the second-order loop in real time on a commercial parallel image processing system is described. Fringe patterns are grabbed and processed, and the resultant phase maps are displayed concurrently.

Double-resolution electron holography with simple Fourier transform of fringe-shifted holograms.

PubMed

Volkov, V V; Han, M G; Zhu, Y

2013-11-01

We propose a fringe-shifting holographic method with an appropriate image wave recovery algorithm leading to exact solution of holographic equations. With this new method the complex object image wave recovered from holograms appears to have much less traditional artifacts caused by the autocorrelation band present practically in all Fourier transformed holograms. The new analytical solutions make possible a double-resolution electron holography free from autocorrelation band artifacts and thus push the limits for phase resolution. The new image wave recovery algorithm uses a popular Fourier solution of the side band-pass filter technique, while the fringe-shifting holographic method is simple to implement in practice. Published by Elsevier B.V.

Brewster-plate spoiler - A novel method for reducing the amplitude of interference fringes that limit tunable-laser absorption sensitivities

NASA Technical Reports Server (NTRS)

Webster, C. R.

1985-01-01

A simple method is described for substantially reducing the amplitude of interference fringes that limit the sensitivities of tunable-laser high-resolution absorption spectrometers. A lead-salt diode laser operating in the 7-micron region is used with a single Brewster-plate spoiler to reduce the fringe amplitude by a factor of 30 and also to allow the detection of absorptances 0.001 percent in a single laser scan without subtraction techniques, without complex frequency modulation, and without distortion of the molecular line-shape signals. Application to multipass-cell spectrometers is described.

The use of fractional orders in the determination of birefringence of highly dispersive materials by the channelled spectrum method

NASA Astrophysics Data System (ADS)

Nagarajan, K.; Shashidharan Nair, C. K.

2007-07-01

The channelled spectrum employing polarized light interference is a very convenient method for the study of dispersion of birefringence. However, while using this method, the absolute order of the polarized light interference fringes cannot be determined easily. Approximate methods are therefore used to estimate the order. One of the approximations is that the dispersion of birefringence across neighbouring integer order fringes is negligible. In this paper, we show how this approximation can cause errors. A modification is reported whereby the error in the determination of absolute fringe order can be reduced using fractional orders instead of integer orders. The theoretical background for this method supported with computer simulation is presented. An experimental arrangement implementing these modifications is described. This method uses a Constant Deviation Spectrometer (CDS) and a Soleil Babinet Compensator (SBC).

Adaptive pixel-to-pixel projection intensity adjustment for measuring a shiny surface using orthogonal color fringe pattern projection

NASA Astrophysics Data System (ADS)

Chen, Chao; Gao, Nan; Wang, Xiangjun; Zhang, Zonghua

2018-05-01

Three-dimensional (3D) shape measurement based on fringe pattern projection techniques has been commonly used in various fields. One of the remaining challenges in fringe pattern projection is that camera sensor saturation may occur if there is a large range of reflectivity variation across the surface that causes measurement errors. To overcome this problem, a novel fringe pattern projection method is proposed to avoid image saturation and maintain high-intensity modulation for measuring shiny surfaces by adaptively adjusting the pixel-to-pixel projection intensity according to the surface reflectivity. First, three sets of orthogonal color fringe patterns and a sequence of uniform gray-level patterns with different gray levels are projected onto a measured surface by a projector. The patterns are deformed with respect to the object surface and captured by a camera from a different viewpoint. Subsequently, the optimal projection intensity at each pixel is determined by fusing different gray levels and transforming the camera pixel coordinate system into the projector pixel coordinate system. Finally, the adapted fringe patterns are created and used for 3D shape measurement. Experimental results on a flat checkerboard and shiny objects demonstrate that the proposed method can measure shiny surfaces with high accuracy.

Single beam write and/or replay of spatial heterodyne holograms

DOEpatents

Thomas, Clarence E.; Hanson, Gregory R.

2007-11-20

A method of writing a spatially heterodyne hologram having spatially heterodyne fringes includes: passing a single write beam through a spatial light modulator that digitally modulates said single write beam; and focusing the single write beam at a focal plane of a lens to impose a holographic diffraction grating pattern on the photorefractive crystal, the holographic diffraction grating pattern including the spatially heterodyne hologram having spatially heterodyne fringes, wherein only said single write beam is incident on said photorefractive crystal without a reference beam. A method of replaying a spatially heterodyne hologram having spatially heterodyne fringes at a replay angle includes: illuminating a photorefractive crystal having a holographic diffraction grating with a beam from a laser at an illumination angle, the holographic diffraction grating pattern including the spatially heterodyne hologram having spatially heterodyne fringes, wherein a difference between said illumination angle and said replay angle defines a diffraction angle .alpha. that is a function of a plane wave mathematically added to original object wave phase and amplitude data of said spatially heterodyne hologram having spatially heterodyne fringes.

Local blur analysis and phase error correction method for fringe projection profilometry systems.

PubMed

Rao, Li; Da, Feipeng

2018-05-20

We introduce a flexible error correction method for fringe projection profilometry (FPP) systems in the presence of local blur phenomenon. Local blur caused by global light transport such as camera defocus, projector defocus, and subsurface scattering will cause significant systematic errors in FPP systems. Previous methods, which adopt high-frequency patterns to separate the direct and global components, fail when the global light phenomenon occurs locally. In this paper, the influence of local blur on phase quality is thoroughly analyzed, and a concise error correction method is proposed to compensate the phase errors. For defocus phenomenon, this method can be directly applied. With the aid of spatially varying point spread functions and local frontal plane assumption, experiments show that the proposed method can effectively alleviate the system errors and improve the final reconstruction accuracy in various scenes. For a subsurface scattering scenario, if the translucent object is dominated by multiple scattering, the proposed method can also be applied to correct systematic errors once the bidirectional scattering-surface reflectance distribution function of the object material is measured.

On Hilbert-Huang Transform Based Synthesis of a Signal Contaminated by Radio Frequency Interference or Fringes

NASA Technical Reports Server (NTRS)

Kizhner, Semion; Shiri, Ron S.; Vootukuru, Meg; Coletti, Alessandro

2015-01-01

Norden E. Huang et al. had proposed and published the Hilbert-Huang Transform (HHT) concept correspondently in 1996, 1998. The HHT is a novel method for adaptive spectral analysis of non-linear and non-stationary signals. The HHT comprises two components: - the Huang Empirical Mode Decomposition (EMD), resulting in an adaptive data-derived basis of Intrinsic Mode functions (IMFs), and the Hilbert Spectral Analysis (HSA1) based on the Hilbert Transform for 1-dimension (1D) applied to the EMD IMF's outcome. Although paper describes the HHT concept in great depth, it does not contain all needed methodology to implement the HHT computer code. In 2004, Semion Kizhner and Karin Blank implemented the reference digital HHT real-time data processing system for 1D (HHT-DPS Version 1.4). The case for 2-Dimension (2D) (HHT2) proved to be difficult due to the computational complexity of EMD for 2D (EMD2) and absence of a suitable Hilbert Transform for 2D spectral analysis (HSA2). The real-time EMD2 and HSA2 comprise the real-time HHT2. Kizhner completed the real-time EMD2 and the HSA2 reference digital implementations respectively in 2013 & 2014. Still, the HHT2 outcome synthesis remains an active research area. This paper presents the initial concepts and preliminary results of HHT2-based synthesis and its application to processing of signals contaminated by Radio-Frequency Interference (RFI), as well as optical systems' fringe detection and mitigation at design stage. The Soil Moisture Active Passive (SMAP mission (SMAP) carries a radiometer instrument that measures Earth soil moisture at L1 frequency (1.4 GHz polarimetric - H, V, 3rd and 4th Stokes parameters). There is abundant RFI at L1 and because soil moisture is a strategic parameter, it is important to be able to recover the RFI-contaminated measurement samples (15% of telemetry). State-of-the-art only allows RFI detection and removes RFI-contaminated measurements. The HHT-based analysis and synthesis facilitates recovery of measurements contaminated by all kinds of RFI, including jamming [7-8]. The fringes are inherent in optical systems and multi-layer complex contour expensive coatings are employed to remove the unwanted fringes. HHT2-based analysis allows test image decomposition to analyze and detect fringes, and HHT2-based synthesis of useful image.

Analysis of localized fringes in the holographic optical Schlieren system

NASA Technical Reports Server (NTRS)

Kurtz, R. L.

1980-01-01

The relation between localization of interference fringes in classical and holographic interferometry is reviewed and an application of holographic interferometry is considered for which the object is a transparent medium with nonhomogeneous refractive index. The technique is based on the analysis of the optical path length change of the object wave as it propagates through a transparent medium. Phase shifts due to variations of the speed of light within the medium give rise to an interference pattern. The resulting interferogram can be used to determine the physical properties of the medium or transparent object. Such properties include the mass density of fluids, electron densities of plasmas, the temperature of fluids, the chemical species concentration of fluids, and the state of stress in solids. The optical wave used can be either a simple plane or spherical wave, or it may be a complicated spatial wave scattered by a diffusing screen. The mathematical theory on the formation and analysis of localized fringes, the general theoretical concepts used, and a computer code for analysis are included along with the inversion of fringe order data.

An optoelectronic system for fringe pattern analysis

NASA Astrophysics Data System (ADS)

Sciammarella, C. A.; Ahmadshahi, M.

A system capable of retrieving and processing information recorded in fringe patterns is reported. The principal components are described as well as the architecture in which they are assembled. An example of application is given.

Boundary-layer transition and global skin friction measurement with an oil-fringe imaging technique

NASA Technical Reports Server (NTRS)

Monson, Daryl J.; Mateer, George G.; Menter, Florian R.

1993-01-01

A new oil-fringe imaging system skin friction (FISF) technique to measure skin friction on wind tunnel models is presented. In the method used to demonstrate the technique, lines of oil are applied on surfaces that connect the intended sets of measurement points, and then a wind tunnel is run so that the oil thins and forms interference fringes that are spaced in proportion to local skin friction. After a run the fringe spacings are imaged with a CCD-array digital camera and measured on a computer. Skin friction and transition measurements on a two-dimensional wing are presented and compared with computational predictions.

Coherent scatter-controlled phase-change grating structures in silicon using femtosecond laser pulses.

PubMed

Fuentes-Edfuf, Yasser; Garcia-Lechuga, Mario; Puerto, Daniel; Florian, Camilo; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2017-07-04

Periodic structures of alternating amorphous-crystalline fringes have been fabricated in silicon using repetitive femtosecond laser exposure (800 nm wavelength and 120 fs duration). The method is based on the interference of the incident laser light with far- and near-field scattered light, leading to local melting at the interference maxima, as demonstrated by femtosecond microscopy. Exploiting this strategy, lines of highly regular amorphous fringes can be written. The fringes have been characterized in detail using optical microscopy combined modelling, which enables a determination of the three-dimensional shape of individual fringes. 2D micro-Raman spectroscopy reveals that the space between amorphous fringes remains crystalline. We demonstrate that the fringe period can be tuned over a range of 410 nm - 13 µm by changing the angle of incidence and inverting the beam scan direction. Fine control over the lateral dimensions, thickness, surface depression and optical contrast of the fringes is obtained via adjustment of pulse number, fluence and spot size. Large-area, highly homogeneous gratings composed of amorphous fringes with micrometer width and millimeter length can readily be fabricated. The here presented fabrication technique is expected to have applications in the fields of optics, nanoelectronics, and mechatronics and should be applicable to other materials.

Variational method for integrating radial gradient field

NASA Astrophysics Data System (ADS)

Legarda-Saenz, Ricardo; Brito-Loeza, Carlos; Rivera, Mariano; Espinosa-Romero, Arturo

2014-12-01

We propose a variational method for integrating information obtained from circular fringe pattern. The proposed method is a suitable choice for objects with radial symmetry. First, we analyze the information contained in the fringe pattern captured by the experimental setup and then move to formulate the problem of recovering the wavefront using techniques from calculus of variations. The performance of the method is demonstrated by numerical experiments with both synthetic and real data.

Information retrieval from holographic interferograms: Fundamentals and problems

NASA Technical Reports Server (NTRS)

Vest, Charles M.

1987-01-01

Holographic interferograms can contain large amounts of information about flow and temperature fields. Their information content can be very high because they can be viewed from many different directions. This multidirectionality, and fringe localization add to the information contained in the fringe pattern if diffuse illumination is used. Additional information, and increased accuracy can be obtained through the use of dual reference wave holography to add reference fringes or to effect discrete phase shift or hetrodyne interferometry. Automated analysis of fringes is possible if interferograms are of simple structure and good quality. However, in practice a large number of practical problems can arise, so that a difficult image processing task results.

Computer aided fringe pattern analysis

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.

The paper reviews the basic laws of fringe pattern interpretation. The different techniques that are currently utilized are presented using a common frame of reference stressing the fact that these techniques are different variations of the same basic principle. Digital and analog techniques are discussed. Currently available hardware is presented and the relationships between hardware and the operations of pattern fringe processing are pointed out. Examples are given to illustrate the ideas discussed in the paper.

Carrier and aberrations removal in interferometric fringe projection profilometry

NASA Astrophysics Data System (ADS)

Blain, P.; Michel, F.; Renotte, Y.; Habraken, S.

2012-04-01

A profilometer which takes advantage of polarization states splitting technique and monochromatic light projection method as a way to overcome ambient lighting for in-situ measurement is under development [1, 2]. Because of the Savart plate which refracts two out of axis beams, the device suffers from aberrations (mostly coma and astigmatism). These aberrations affect the quality of the sinusoidal fringe pattern. In fringe projection profilometry, the unwrapped phase distribution map contains the sum of the object's shape-related phase and carrier-fringe-related phase. In order to extract the 3D shape of the object, the carrier phase has to be removed [3, 4]. An easy way to remove both the fringe carrier and the aberrations of the optical system is to measure the phases of the test object and to measure the phase of a reference plane with the same set up and to subtract both phase maps. This time consuming technique is suitable for laboratory but not for industry. We propose a method to numerically remove both the fringe carrier and the aberrations. A first reference phase of a calibration plane is evaluated knowing the position of the different elements in the set up and the orientation of the fringes. Then a fitting of the phase map by Zernike polynomials is computed [5]. As the triangulation parameters are known during the calibration, the computation of Zernike coefficients has only to be made once. The wavefront error can be adjusted by a scale factor which depends on the position of the test object.

Quantization error of CCD cameras and their influence on phase calculation in fringe pattern analysis.

PubMed

Skydan, Oleksandr A; Lilley, Francis; Lalor, Michael J; Burton, David R

2003-09-10

We present an investigation into the phase errors that occur in fringe pattern analysis that are caused by quantization effects. When acquisition devices with a limited value of camera bit depth are used, there are a limited number of quantization levels available to record the signal. This may adversely affect the recorded signal and adds a potential source of instrumental error to the measurement system. Quantization effects also determine the accuracy that may be achieved by acquisition devices in a measurement system. We used the Fourier fringe analysis measurement technique. However, the principles can be applied equally well for other phase measuring techniques to yield a phase error distribution that is caused by the camera bit depth.

Probing the prodigious strain fringes from Lourdes

NASA Astrophysics Data System (ADS)

Aerden, Domingo G. A. M.; Sayab, Mohammad

2017-12-01

We investigate the kinematics of classic sigmoidal strain fringes from Lourdes (France) and review previous genetic models, strain methods and strain rates for these microstructures. Displacement controlled quartz and calcite fibers within the fringes yield an average strain of 195% with the technique of Ramsay and Huber (1983). This agrees well with strains measured from boudinaged pyrite layers and calcite veins in the same rocks, but conflicts with ca. ∼675% strain in previous analogue models for the studied strain fringes produced by progressive simple shear. We show that the detailed geometry and orientation of fiber patterns are insufficiently explained by simple shear but imply two successive, differently oriented strain fields. Although all strain fringes have the same overall asymmetry, considerable morphological variation resulted from different amounts of rotation of pyrite grains and fringes. Minor rotation led to sharply kinked fibers that record a ca. 70° rotation of the kinematic frame. Larger (up to 145°) rotations, accommodated by antithetic sliding on pyrite-fringe contacts, produced more strongly and smoothly curved fibers. Combined with published Rb-Sr ages for the studied microstructures, our new strain data indicate an average strain rate of 1.41 10-15 s-1 during ca. 37 Myr. continuous growth.

Patient-specific 3D models created by 3D imaging system or bi-planar imaging coupled with Moiré-Fringe projections: a comparative study of accuracy and reliability on spinal curvatures and vertebral rotation data.

PubMed

Hocquelet, Arnaud; Cornelis, François; Jirot, Anna; Castaings, Laurent; de Sèze, Mathieu; Hauger, Olivier

2016-10-01

The aim of this study is to compare the accuracy and reliability of spinal curvatures and vertebral rotation data based on patient-specific 3D models created by 3D imaging system or by bi-planar imaging coupled with Moiré-Fringe projections. Sixty-two consecutive patients from a single institution were prospectively included. For each patient, frontal and sagittal calibrated low-dose bi-planar X-rays were performed and coupled simultaneously with an optical Moiré back surface-based technology. The 3D reconstructions of spine and pelvis were performed independently by one radiologist and one technician in radiology using two different semi-automatic methods using 3D radio-imaging system (method 1) or bi-planar imaging coupled with Moiré projections (method 2). Both methods were compared using Bland-Altman analysis, and reliability using intraclass correlation coefficient (ICC). ICC showed good to very good agreement. Between the two techniques, the maximum 95 % prediction limits was -4.9° degrees for the measurements of spinal coronal curves and less than 5° for other parameters. Inter-rater reliability was excellent for all parameters across both methods, except for axial rotation with method 2 for which ICC was fair. Method 1 was faster for reconstruction time than method 2 for both readers (13.4 vs. 20.7 min and 10.6 vs. 13.9 min; p = 0.0001). While a lower accuracy was observed for the evaluation of the axial rotation, bi-planar imaging coupled with Moiré-Fringe projections may be an accurate and reliable tool to perform 3D reconstructions of the spine and pelvis.

Precision measurement of refractive index of air based on laser synthetic wavelength interferometry with Edlén equation estimation.

PubMed

Yan, Liping; Chen, Benyong; Zhang, Enzheng; Zhang, Shihua; Yang, Ye

2015-08-01

A novel method for the precision measurement of refractive index of air (n(air)) based on the combining of the laser synthetic wavelength interferometry with the Edlén equation estimation is proposed. First, a n(air_e) is calculated from the modified Edlén equation according to environmental parameters measured by low precision sensors with an uncertainty of 10(-6). Second, a unique integral fringe number N corresponding to n(air) is determined based on the calculated n(air_e). Then, a fractional fringe ε corresponding to n(air) with high accuracy can be obtained according to the principle of fringe subdivision of laser synthetic wavelength interferometry. Finally, high accurate measurement of n(air) is achieved according to the determined fringes N and ε. The merit of the proposed method is that it not only solves the problem of the measurement accuracy of n(air) being limited by the accuracies of environmental sensors, but also avoids adopting complicated vacuum pumping to measure the integral fringe N in the method of conventional laser interferometry. To verify the feasibility of the proposed method, comparison experiments with Edlén equations in short time and in long time were performed. Experimental results show that the measurement accuracy of n(air) is better than 2.5 × 10(-8) in short time tests and 6.2 × 10(-8) in long time tests.

Denoising by coupled partial differential equations and extracting phase by backpropagation neural networks for electronic speckle pattern interferometry.

PubMed

Tang, Chen; Lu, Wenjing; Chen, Song; Zhang, Zhen; Li, Botao; Wang, Wenping; Han, Lin

2007-10-20

We extend and refine previous work [Appl. Opt. 46, 2907 (2007)]. Combining the coupled nonlinear partial differential equations (PDEs) denoising model with the ordinary differential equations enhancement method, we propose the new denoising and enhancing model for electronic speckle pattern interferometry (ESPI) fringe patterns. Meanwhile, we propose the backpropagation neural networks (BPNN) method to obtain unwrapped phase values based on a skeleton map instead of traditional interpolations. We test the introduced methods on the computer-simulated speckle ESPI fringe patterns and experimentally obtained fringe pattern, respectively. The experimental results show that the coupled nonlinear PDEs denoising model is capable of effectively removing noise, and the unwrapped phase values obtained by the BPNN method are much more accurate than those obtained by the well-known traditional interpolation. In addition, the accuracy of the BPNN method is adjustable by changing the parameters of networks such as the number of neurons.

Shape measurement and vibration analysis of moving speaker cone

NASA Astrophysics Data System (ADS)

Zhang, Qican; Liu, Yuankun; Lehtonen, Petri

2014-06-01

Surface three-dimensional (3-D) shape information is needed for many fast processes such as structural testing of material, standing waves on loudspeaker cone, etc. Usually measurement is done from limited number of points using electrical sensors or laser distance meters. Fourier Transform Profilometry (FTP) enables fast shape measurement of the whole surface. Method is based on angled sinusoidal fringe pattern projection and image capturing. FTP requires only one image of the deformed fringe pattern to restore the 3-D shape of the measured object, which makes real-time or dynamic data processing possible. In our experiment the method was used for loudspeaker cone distortion measurement in dynamic conditions. For sound quality issues it is important that the whole cone moves in same phase and there are no partial waves. Our imaging resolution was 1280x1024 pixels and frame rate was 200 fps. Using our setup we found unwanted spatial waves in our sample cone.

Structured light system calibration method with optimal fringe angle.

PubMed

Li, Beiwen; Zhang, Song

2014-11-20

For structured light system calibration, one popular approach is to treat the projector as an inverse camera. This is usually performed by projecting horizontal and vertical sequences of patterns to establish one-to-one mapping between camera points and projector points. However, for a well-designed system, either horizontal or vertical fringe images are not sensitive to depth variation and thus yield inaccurate mapping. As a result, the calibration accuracy is jeopardized if a conventional calibration method is used. To address this limitation, this paper proposes a novel calibration method based on optimal fringe angle determination. Experiments demonstrate that our calibration approach can increase the measurement accuracy up to 38% compared to the conventional calibration method with a calibration volume of 300(H)  mm×250(W)  mm×500(D)  mm.

Three-dimensional displacement measurement by fringe projection and speckle photography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barrientos, B.; Garcia-Marquez, J.; Cerca, M.

2008-04-15

3D displacement fields are measured by the combination of two optical methods, fringe projection and speckle photography. The use of only one camera recording the necessary information implies that no calibration procedures are necessary as is the case in techniques based on stereoscopy. The out-of-plane displacement is measured by fringe projection whereas speckle photography yields the 2-D in-plane component. To show the feasibility of the technique, we analyze a detailed morphological spatio-temporal evolution of a model of the Earth's crust while subjected to compression forces. The results show that the combination of fringe projection and speckle photography is well suitedmore » for this type of studies.« less

A low-cost and portable realization on fringe projection three-dimensional measurement

NASA Astrophysics Data System (ADS)

Xiao, Suzhi; Tao, Wei; Zhao, Hui

2015-12-01

Fringe projection three-dimensional measurement is widely applied in a wide range of industrial application. The traditional fringe projection system has the disadvantages of high expense, big size, and complicated calibration requirements. In this paper we introduce a low-cost and portable realization on three-dimensional measurement with Pico projector. It has the advantages of low cost, compact physical size, and flexible configuration. For the proposed fringe projection system, there is no restriction to camera and projector's relative alignment on parallelism and perpendicularity for installation. Moreover, plane-based calibration method is adopted in this paper that avoids critical requirements on calibration system such as additional gauge block or precise linear z stage. What is more, error sources existing in the proposed system are introduced in this paper. The experimental results demonstrate the feasibility of the proposed low cost and portable fringe projection system.

Simulating interfering fringe displacements by lateral shifts of a camera for educational purposes

NASA Astrophysics Data System (ADS)

Rivera-Ortega, Uriel

2018-07-01

In this manuscript we propose a simple method to emulate fringe displacements in a fringe pattern, due to the interference of two plane waves, by using lateral shifts of a CMOS detector under the scheme of a Twyman–Green interferometric setup, avoiding unwanted vibrations and the need for specific and expensive devices in order to accomplish the task. The simplicity of the proposed experimental setup allows it to be easily replicated and used for teaching or demonstrative purposes, essentially for undergraduate students.

4D metrology of flapping-wing micro air vehicle based on fringe projection

NASA Astrophysics Data System (ADS)

Zhang, Qican; Huang, Lei; Chin, Yao-Wei; Keong, Lau-Gih; Asundi, Anand

2013-06-01

Inspired by dominant flight of the natural flyers and driven by civilian and military purposes, micro air vehicle (MAV) has been developed so far by passive wing control but still pales in aerodynamic performance. Better understanding of flapping wing flight mechanism is eager to improve MAV's flight performance. In this paper, a simple and effective 4D metrology technique to measure full-field deformation of flapping membrane wing is presented. Based on fringe projection and 3D Fourier analysis, the fast and complex dynamic deformation, including wing rotation and wing stroke, of a flapping wing during its flight can be accurately reconstructed from the deformed fringe patterns recorded by a highspeed camera. An experiment was carried on a flapping-wing MAV with 5-cm span membrane wing beating at 30 Hz, and the results show that this method is effective and will be useful to the aerodynamicist or micro aircraft designer for visualizing high-speed complex wing deformation and consequently aid the design of flapping wing mechanism to enhanced aerodynamic performance.

Integrated optical 3D digital imaging based on DSP scheme

NASA Astrophysics Data System (ADS)

Wang, Xiaodong; Peng, Xiang; Gao, Bruce Z.

2008-03-01

We present a scheme of integrated optical 3-D digital imaging (IO3DI) based on digital signal processor (DSP), which can acquire range images independently without PC support. This scheme is based on a parallel hardware structure with aid of DSP and field programmable gate array (FPGA) to realize 3-D imaging. In this integrated scheme of 3-D imaging, the phase measurement profilometry is adopted. To realize the pipeline processing of the fringe projection, image acquisition and fringe pattern analysis, we present a multi-threads application program that is developed under the environment of DSP/BIOS RTOS (real-time operating system). Since RTOS provides a preemptive kernel and powerful configuration tool, with which we are able to achieve a real-time scheduling and synchronization. To accelerate automatic fringe analysis and phase unwrapping, we make use of the technique of software optimization. The proposed scheme can reach a performance of 39.5 f/s (frames per second), so it may well fit into real-time fringe-pattern analysis and can implement fast 3-D imaging. Experiment results are also presented to show the validity of proposed scheme.

Theoretical fringe profiles with crossed Babinet compensators in testing concave aspheric surfaces.

PubMed

Saxena, A K; Lancelot, J P

1982-11-15

This paper presents the theory for the use of crossed Babinet compensators in testing concave aspheric surfaces. Theoretical fringe profiles for a sphere and for an aspheric surface with primary aberration are shown. Advantages of this method are discussed.

The self-calibration method for multiple systems at the CHARA Array

NASA Astrophysics Data System (ADS)

O'Brien, David

The self-calibration method, a new interferometric technique at the CHARA Array, has been used to derive orbits for several spectroscopic binaries. This method uses the wide component of a hierarchical triple system to calibrate visibility measurements of the triple's close binary system. At certain baselines and separations, the calibrator in one of these systems can be observed quasi-simultaneously with the target. Depending on the orientation of the CHARA observation baseline relative to the orientation of the wide orbit of the triple system, separated fringe packets may be observed. A sophisticated observing scheme must be put in place to ensure the existence of separated fringe packets on nights of observation. Prior to the onset of this project, the reduction of separated fringe packet data had never included the goal of deriving visibilities for both fringe packets, so new data reduction software has been written. Visibilities obtained with separated fringe packet data for the target close binary are run through both Monte Carlo simulations and grid search programs in order to determine the best-fit orbital elements of the close binary. Several targets have been observed in this fashion, and orbits have been derived for seven targets, including three new orbits. Derivation of the orbit of the close pair in a triple system allows for the calculation of the mutual inclination, which is the angle between the planes of the wide and close orbit. Knowledge of this quantity may give insight into the formation processes that create multiple star systems. INDEX WORDS: Long-baseline interferometry, Self calibration, Separated fringe packets, Triple systems, Close binaries, Multiple systems, Orbital parameters, Near-infrared interferometry

Three-dimensional motion detection of a 20-nm gold nanoparticle using twilight-field digital holography with coherence regulation.

PubMed

Goto, Kazufumi; Hayasaki, Yoshio

2015-07-15

In the twilight-field method for obtaining interference fringes with high contrast in in-line digital holography, only the intensity of the reference light is regulated to be close to the intensity of the object light, which is the ultra-weak scattered light from a nanoparticle, by using a low-frequency attenuation filter. Coherence of the light also strongly affects the contrast of the interference fringes. High coherence causes a lot of undesired coherent noise, which masks the fringes derived from the nanoparticles. Too-low coherence results in fringes with low contrast and a correspondingly low signal-to-noise ratio. Consequently, proper regulation of the coherence of the light source, in this study the spectral width, improves the minimum detectable size in holographic three-dimensional position measurement of nanoparticles. By using these methods, we were able to measure the position of a gold nanoparticle with a minimum diameter of 20 nm.

Large radius of curvature measurement based on virtual quadratic Newton rings phase-shifting moiré-fringes measurement method in a nonnull interferometer.

PubMed

Yang, Zhongming; Wang, Kailiang; Cheng, Jinlong; Gao, Zhishan; Yuan, Qun

2016-06-10

We have proposed a virtual quadratic Newton rings phase-shifting moiré-fringes measurement method in a nonnull interferometer to measure the large radius of curvature for a spherical surface. In a quadratic polar coordinate system, linear carrier testing Newton rings interferogram and virtual Newton rings interferogram form the moiré fringes. It is possible to retrieve the wavefront difference data between the testing and standard spherical surface from the moiré fringes after low-pass filtering. Based on the wavefront difference data, we deduced a precise formula to calculate the radius of curvature in the quadratic polar coordinate system. We calculated the retrace error in the nonnull interferometer using the multi-configuration model of the nonnull interferometric system in ZEMAX. Our experimental results indicate that the measurement accuracy is better than 0.18% for a spherical mirror with a radius of curvature of 41,400 mm.

Inspection of arterial-induced skin vibration by Moire fringe with two-dimensional continuous wavelet transform

NASA Astrophysics Data System (ADS)

Wang, Chun-Hsiung; Chiu, Shih-Yung; Hsu, Yu-Hsiang; Lee, Shu-Sheng; Lee, Chih-Kung

2017-06-01

A non-contact arterial-induced skin vibration inspection system is implemented. This optical metrology system is constructed with shadow Moiré configuration and the fringe analysis algorithm. Developed with the Region of Interested (ROI) capturing technique and the Two-dimensional Wavelet Transform (2D-CWT) method, this algorithm is able to retrieve the height-correlated phase information from the shadow Moiré fringe patterns. Using a commercial video camera or a CMOS image sensor, this system could monitor the skin-vibration induced by the cyclic deformation of inner layered artery. The cross-sectional variation and the rhythm of heart cycle could be continuously measured for health monitoring purposes. The average vibration amplitude of the artery at the wrist ranges between 20 μm and 50 μm, which is quite subtle comparing with the skin surface structure. Having the non-stationary motion of human body, the traditional phase shifting (PS) technique can be very unstable due to the requirement of several frames of images, especially for case that artery is continuously pumping. To bypass this fundamental issue, the shadow Moiré technique is introduced to enhance the surface deformation characteristic. And the phase information is retrieved by the means of spectrum filtering instead of PS technique, which the phase is calculated from intensity maps of multiple images. The instantaneous surface can therefore be reconstructed individually from each frame, enabling the subtle arterial-induced skin vibration measurement. The comparative results of phase reconstruction between different fringe analysis algorithms will be demonstrated numerically and experimentally. And the electrocardiography (ECG) results will used as the reference for the validity of health monitoring potential of the non-contact arterial-induced skin vibration inspection system.

3D shape measurement of automotive glass by using a fringe reflection technique

NASA Astrophysics Data System (ADS)

Skydan, O. A.; Lalor, M. J.; Burton, D. R.

2007-01-01

In automotive and glass making industries, there is a need for accurately measuring the 3D shapes of reflective surfaces to speed up and ensure product development and manufacturing quality by using non-contact techniques. This paper describes a technique for the measurement of non-full-field reflective surfaces of automotive glass by using a fringe reflection technique. Physical properties of the measurement surfaces do not allow us to apply optical geometries used in existing techniques for surface measurement based upon direct fringe pattern illumination. However, this property of surface reflectivity can be used to implement similar ideas from existing techniques in a new improved method. In other words, the reflective surface can be used as a mirror to reflect illuminated fringe patterns onto a screen behind. It has been found that in the case of implementing the reflective fringe technique, the phase-shift distribution depends not only on the height of the object but also on the slope at each measurement point. This requires the solving of differential equations to find the surface slope and height distributions in the x and y directions and development of the additional height reconstruction algorithms. The main focus has been made on developing a mathematical model of the optical sub-system and discussing ways for its practical implementation including calibration procedures. A number of implemented image processing algorithms for system calibration and data analysis are discussed and two experimental results are given for automotive glass surfaces with different shapes and defects. The proposed technique showed the ability to provide accurate non-destructive measurement of 3D shapes of the reflective automotive glass surfaces and can be used as a key element for a glass shape quality control system on-line or in a laboratory environment.

Modeling of Dipole and Quadrupole Fringe-Field Effects for the Advanced Photon Source Upgrade Lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borland, M.; Lindberg, R.

2017-06-01

The proposed upgrade of the Advanced Photon Source (APS) to a multibend-achromat lattice requires shorter and much stronger quadrupole magnets than are present in the existing ring. This results in longitudinal gradient profiles that differ significantly from a hard-edge model. Additionally, the lattice assumes the use of five-segment longitudinal gradient dipoles. Under these circumstances, the effects of fringe fields and detailed field distributions are of interest. We evaluated the effect of soft-edge fringe fields on the linear optics and chromaticity, finding that compensation for these effects is readily accomplished. In addition, we evaluated the reliability of standard methods of simulatingmore » hardedge nonlinear fringe effects in quadrupoles.« less

Measurement of gradient index profiles by Babinet fringe analysis.

PubMed

Pandya, T P; Saxena, A K

1979-03-01

A theory for determining one-dimensional ray deflections with the help of distorted Babinet fringes has been developed. An approach for investigating two-dimensional ray deflections has been presented. Applications of the techniques for the study of gradient index glass have been described.

X-ray Moiré deflectometry using synthetic reference images

DOE PAGES

Stutman, Dan; Valdivia, Maria Pia; Finkenthal, Michael

2015-06-25

Moiré fringe deflectometry with grating interferometers is a technique that enables refraction-based x-ray imaging using a single exposure of an object. To obtain the refraction image, the method requires a reference fringe pattern (without the object). Our study shows that, in order to avoid artifacts, the reference pattern must be exactly matched in phase with the object fringe pattern. In experiments, however, it is difficult to produce a perfectly matched reference pattern due to unavoidable interferometer drifts. We present a simple method to obtain matched reference patterns using a phase-scan procedure to generate synthetic Moiré images. As a result, themore » method will enable deflectometric diagnostics of transient phenomena such as laser-produced plasmas and could improve the sensitivity and accuracy of medical phase-contrast imaging.« less

Real-time determination of fringe pattern frequencies: An application to pressure measurement

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Piroozan, Parham

2007-05-01

Retrieving information in real time from fringe patterns is a topic of a great deal of interest in scientific and engineering applications of optical methods. This paper presents a method for fringe frequency determination based on the capability of neural networks to recognize signals that are similar but not identical to signals used to train the neural network. Sampled patterns are generated by calibration and stored in memory. Incoming patterns are analyzed by a back-propagation neural network at the speed of the recording device, a CCD camera. This method of information retrieval is utilized to measure pressures on a boundary layer flow. The sensor combines optics and electronics to analyze dynamic pressure distributions and to feed information to a control system that is capable to preserve the stability of the flow.

Utilization characteristics and importance of woody biomass resources on the rural-urban fringe in botswana.

PubMed

Nkambwe, Musisi; Sekhwela, Mogodisheng B M

2006-02-01

This article examines the utilization characteristics and importance of woody biomass resources in the rural-urban fringe zones of Botswana. In the literature for Africa, attention has been given to the availability and utilization of biomass in either urban or rural environments, but the rural-urban fringe has been neglected. Within southern Africa, this neglect is not justified; the rural-urban fringe, not getting the full benefits available in urban environments in Botswana, has developed problems in woody biomass availability and utilization that require close attention. In this article, socioeconomic data on the importance of woody biomass in the Batlokwa Tribal Territory, on the rural-urban fringe of Gaborone, Botswana, were collected together with ecologic data that reveal the utilization characteristics and potential for regrowth of woody biomass. The analysis of these results show that local woody biomass is very important in the daily lives of communities in the rural-urban fringe zones and that there is a high level of harvesting. However, there is no effort in planning land use in the tribal territory to either conserve this resource or provide alternatives to its utilization. The future of woody biomass resources in Botswana's rural-urban fringe is uncertain. The investigators recommend that a comprehensive policy for the development of the rural-urban fringe consider the importance of this resource. The neglect of this resource will have far-reaching implications on the livelihoods of residents as well as the environment in this zone.

Passive shimming of the fringe field of a superconducting magnet for ultra-low field hyperpolarized noble gas MRI.

PubMed

Parra-Robles, Juan; Cross, Albert R; Santyr, Giles E

2005-05-01

Hyperpolarized noble gases (HNGs) provide exciting possibilities for MR imaging at ultra-low magnetic field strengths (<0.15 T) due to the extremely high polarizations available from optical pumping. The fringe field of many superconductive magnets used in clinical MR imaging can provide a stable magnetic field for this purpose. In addition to offering the benefit of HNG MR imaging alongside conventional high field proton MRI, this approach offers the other useful advantage of providing different field strengths at different distances from the magnet. However, the extremely strong field gradients associated with the fringe field present a major challenge for imaging since impractically high active shim currents would be required to achieve the necessary homogeneity. In this work, a simple passive shimming method based on the placement of a small number of ferromagnetic pieces is proposed to reduce the fringe field inhomogeneities to a level that can be corrected using standard active shims. The method explicitly takes into account the strong variations of the field over the volume of the ferromagnetic pieces used to shim. The method is used to obtain spectra in the fringe field of a high-field (1.89 T) superconducting magnet from hyperpolarized 129Xe gas samples at two different ultra-low field strengths (8.5 and 17 mT). The linewidths of spectra measured from imaging phantoms (30 Hz) indicate a homogeneity sufficient for MRI of the rat lung.

Holographic Moire Contouring

NASA Astrophysics Data System (ADS)

Sciammarella, C. A.; Sainov, Ventseslav; Simova, Eli

1990-04-01

Theoretical analysis and experimental results on holographic moire contouring (HMC) of difussely reflecting objects are presented. The sensitivity and application constraints of the method are discussed. A high signal-to-noise ratio and contrast of the fringes is achieved through the use of high quality silver halide holographic plates HP-650. A good agreement between theoretical and experimental results is observed.

Large-mirror testing facility at the National Optical Astronomy Observatories.

NASA Astrophysics Data System (ADS)

Barr, L. D.; Coudé du Foresto, V.; Fox, J.; Poczulp, G. A.; Richardson, J.; Roddier, C.; Roddier, F.

1991-09-01

A method for testing the surfaces of large mirrors has been developed to be used even when conditions of vibration and thermal turbulence in the light path cannot be eliminated. The full aperture of the mirror under test is examined by means of a scatterplate interferometer that has the property of being a quasi-common-path method, although any means for obtaining interference fringes will do. The method uses a remotely operated CCD camera system to record the fringe pattern from the workpiece. The typical test is done with a camera exposure of about a millisecond to "freeze" the fringe pattern on the detector. Averaging up to 10 separate exposures effectively eliminates the turbulence effects. The method described provides the optician with complete numerical information and visual plots for the surface under test and the diffracted image the method will produce, all within a few minutes, to an accuracy of 0.01 μm measured peak-to-valley.

Determination of displacements and their derivatives from 3D fringe patterns via extended monogenic phasor method

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Lamberti, Luciano

2018-05-01

For 1D signals, it is necessary to resort to a 2D abstract space because the concept of phase utilized in the retrieval of fringe pattern analysis information relies on the use of a vectorial function. Fourier and Hilbert transforms provide in-quadrature signals that lead to the very important basic concept of local phase. A 3D abstract space must hence be generated in order to analyze 2D signals. A 3D vector space in a Cartesian complex space is graphically represented by a Poincare sphere. In this study, the extension of the associated spaces is extended to 3D. A 4D hypersphere is defined for that purpose. The proposed approach is illustrated by determining the deformations of the heart left ventricle.

Effect of fringe-artifact correction on sub-tomogram averaging from Zernike phase-plate cryo-TEM

PubMed Central

Kishchenko, Gregory P.; Danev, Radostin; Fisher, Rebecca; He, Jie; Hsieh, Chyongere; Marko, Michael; Sui, Haixin

2015-01-01

Zernike phase-plate (ZPP) imaging greatly increases contrast in cryo-electron microscopy, however fringe artifacts appear in the images. A computational de-fringing method has been proposed, but it has not been widely employed, perhaps because the importance of de-fringing has not been clearly demonstrated. For testing purposes, we employed Zernike phase-plate imaging in a cryo-electron tomographic study of radial-spoke complexes attached to microtubule doublets. We found that the contrast enhancement by ZPP imaging made nonlinear denoising insensitive to the filtering parameters, such that simple low-frequency band-pass filtering made the same improvement in map quality. We employed sub-tomogram averaging, which compensates for the effect of the “missing wedge” and considerably improves map quality. We found that fringes (caused by the abrupt cut-on of the central hole in the phase plate) can lead to incorrect representation of a structure that is well-known from the literature. The expected structure was restored by amplitude scaling, as proposed in the literature. Our results show that de-fringing is an important part of image-processing for cryo-electron tomography of macromolecular complexes with ZPP imaging. PMID:26210582

Two-dimensional fringe probing of transient liquid temperatures in a mini space.

PubMed

Xue, Zhenlan; Qiu, Huihe

2011-05-01

A 2D fringe probing transient temperature measurement technique based on photothermal deflection theory was developed. It utilizes material's refractive index dependence on temperature gradient to obtain temperature information from laser deflection. Instead of single beam, this method applies multiple laser beams to obtain 2D temperature information. The laser fringe was generated with a Mach-Zehnder interferometer. A transient heating experiment was conducted using an electric wire to demonstrate this technique. Temperature field around a heating wire and variation with time was obtained utilizing the scattering fringe patterns. This technique provides non-invasive 2D temperature measurements with spatial and temporal resolutions of 3.5 μm and 4 ms, respectively. It is possible to achieve temporal resolution to 500 μs utilizing the existing high speed camera.

A new method for determining the plasma electron density using optical frequency comb interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arakawa, Hiroyuki, E-mail: arakawa@fmt.teikyo-u.ac.jp; Tojo, Hiroshi; Sasao, Hajime

2014-04-15

A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density.

Phase retrieval in digital speckle pattern interferometry by use of a smoothed space-frequency distribution.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2003-12-10

We evaluate the use of a smoothed space-frequency distribution (SSFD) to retrieve optical phase maps in digital speckle pattern interferometry (DSPI). The performance of this method is tested by use of computer-simulated DSPI fringes. Phase gradients are found along a pixel path from a single DSPI image, and the phase map is finally determined by integration. This technique does not need the application of a phase unwrapping algorithm or the introduction of carrier fringes in the interferometer. It is shown that a Wigner-Ville distribution with a smoothing Gaussian kernel gives more-accurate results than methods based on the continuous wavelet transform. We also discuss the influence of filtering on smoothing of the DSPI fringes and some additional limitations that emerge when this technique is applied. The performance of the SSFD method for processing experimental data is then illustrated.

Analysis of a multi-wavelength multi-camera phase-shifting profilometric system for real-time operation

NASA Astrophysics Data System (ADS)

Stoykova, Elena; Gotchev, Atanas; Sainov, Ventseslav

2011-01-01

Real-time accomplishment of a phase-shifting profilometry through simultaneous projection and recording of fringe patterns requires a reliable phase retrieval procedure. In the present work we consider a four-wavelength multi-camera system with four sinusoidal phase gratings for pattern projection that implements a four-step algorithm. Successful operation of the system depends on overcoming two challenges which stem out from the inherent limitations of the phase-shifting algorithm, namely the demand for a sinusoidal fringe profile and the necessity to ensure equal background and contrast of fringes in the recorded fringe patterns. As a first task, we analyze the systematic errors due to the combined influence of the higher harmonics and multi-wavelength illumination in the Fresnel diffraction zone considering the case when the modulation parameters of the four gratings are different. As a second task we simulate the system performance to evaluate the degrading effect of the speckle noise and the spatially varying fringe modulation at non-uniform illumination on the overall accuracy of the profilometric measurement. We consider the case of non-correlated speckle realizations in the recorded fringe patterns due to four-wavelength illumination. Finally, we apply a phase retrieval procedure which includes normalization, background removal and denoising of the recorded fringe patterns to both simulated and measured data obtained for a dome surface.

An approach for cell viability online detection based on the characteristics of lensfree cell diffraction fingerprint.

PubMed

Li, Guoxiao; Zhang, Rongbiao; Yang, Ning; Yin, Changsheng; Wei, Mingji; Zhang, Yecheng; Sun, Jian

2018-06-01

To overcome the drawbacks such as low automation and high cost, an approach for cell viability online detection is proposed, based on the extracted lensfree cell diffraction fingerprint characteristics. The cell fingerprints are acquired by a constructed large field-of-view (FOV) diffraction imaging platform without any lenses. The approach realizes distinguishing live and dead cells online and calculating cell viability index based on the number of live cells. With theoretical analysis and simulation, diffraction fingerprints of cells with different morphology are simulated and two characteristics are discovered to be able to reflect cell viability status effectively. Two parameters, fringe intensity contrast (FIC) and fringe dispersion (FD), are defined to quantify these two characteristics. They are verified to be reliable to identify live cells. In a cytotoxicity assay of different methyl mercury concentration on BRL cells, the proposed approach is used to detect cell viability. MTT method is also employed and the results of correlational analysis and Bland-Altman analysis prove the validity of the proposed approach. By comparison, it can be revealed that the proposed approach has some advantages over other present techniques. Therefore it may be widely used as a cell viability measurement method in drug screening, nutritional investigation and cell toxicology studies. Copyright © 2018 Elsevier B.V. All rights reserved.

Advanced technology development multi-color holography

NASA Technical Reports Server (NTRS)

Vikram, Chandra S.

1993-01-01

This is the final report of the Multi-color Holography project. The comprehensive study considers some strategic aspects of multi-color holography. First, various methods of available techniques for accurate fringe counting are reviewed. These are heterodyne interferometry, quasi-heterodyne interferometry, and phase-shifting interferometry. Phase-shifting interferometry was found to be the most suitable for multi-color holography. Details of experimentation with a sugar solution are also reported where better than 1/200 of a fringe order measurement capability was established. Rotating plate glass phase shifter was used for the experimentation. The report then describes the possible role of using more than two wavelengths with special reference-to-object beam intensity ratio needs in multicolor holography. Some specific two- and three-color cases are also described in detail. Then some new analysis methods of the reconstructed wavefront are considered. These are deflectometry, speckle metrology, confocal optical signal processing, and phase shifting technique related applications. Finally, design aspects of an experimental breadboard are presented.

Real-time electron density measurements from Cotton-Mouton effect in JET machine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brombin, M.; Electrical Engineering Department, Padova University, via Gradenigo 6-A, 35131 Padova; Boboc, A.

Real-time density profile measurements are essential for advanced fusion tokamak operation and interferometry is a proven method for this task. Nevertheless, as a consequence of edge localized modes, pellet injections, fast density increases, or disruptions, the interferometer is subject to fringe jumps, which produce loss of the signal preventing reliable use of the measured density in a real-time feedback controller. An alternative method to measure the density is polarimetry based on the Cotton-Mouton effect, which is proportional to the line-integrated electron density. A new analysis approach has been implemented and tested to verify the reliability of the Cotton-Mouton measurements formore » a wide range of plasma parameters and to compare the density evaluated from polarimetry with that from interferometry. The density measurements based on polarimetry are going to be integrated in the real-time control system of JET since the difference with the interferometry is within one fringe for more than 90% of the cases.« less

Review and New Results of Local Helioseismology

NASA Astrophysics Data System (ADS)

Chou, Dean-Yi

2011-10-01

We briefly review various methods used in local helioseismology, and discuss our recent results on the acoustic waves scattered by sunspots. We use a deconvolution method to obtain the 2-D wavefunction of the scattered wave from the cross correlations between the incident wave and the signal at various points on the surface. The wavefunctions of scattered waves associated with various incident waves could be used to probe the sunspot. The interference fringes between the scattered wave and the incident wave are detected because the coherent time of the incident wave is of the order of wave period. These interference fringes play the same role as a hologram in optics. We demonstrate that these interference fringes (hologram) can be used to reconstruct the 2-D scattered wavefield of the sunspot.

Optical holographic structural analysis of Kevlar rocket motor cases

NASA Astrophysics Data System (ADS)

Harris, W. J.

1981-05-01

The methodology of applying optical holography to evaluation of subscale Kevlar 49 composite pressure vessels is explored. The results and advantages of the holographic technique are discussed. The cases utilized were of similar design, but each had specific design features, the effects of which are reviewed. Burst testing results are presented in conjunction with the holographic fringe patterns obtained during progressive pressurization. Examples of quantitative data extracted by analysis of fringe fields are included.

Isogyres - Manifestation of Spin-orbit interaction in uniaxial crystal: A closed-fringe Fourier analysis of conoscopic interference

NASA Astrophysics Data System (ADS)

Samlan, C. T.; Naik, Dinesh N.; Viswanathan, Nirmal K.

2016-09-01

Discovered in 1813, the conoscopic interference pattern observed due to light propagating through a crystal, kept between crossed polarizers, shows isochromates and isogyres, respectively containing information about the dynamic and geometric phase acquired by the beam. We propose and demonstrate a closed-fringe Fourier analysis method to disentangle the isogyres from the isochromates, leading us to the azimuthally varying geometric phase and its manifestation as isogyres. This azimuthally varying geometric phase is shown to be the underlying mechanism for the spin-to-orbital angular momentum conversion observed in a diverging optical field propagating through a z-cut uniaxial crystal. We extend the formalism to study the optical activity mediated uniaxial-to-biaxial transformation due to a weak transverse electric field applied across the crystal. Closely associated with the phase and polarization singularities of the optical field, the formalism enables us to understand crystal optics in a new way, paving the way to anticipate several emerging phenomena.

Isogyres - Manifestation of Spin-orbit interaction in uniaxial crystal: A closed-fringe Fourier analysis of conoscopic interference.

PubMed

Samlan, C T; Naik, Dinesh N; Viswanathan, Nirmal K

2016-09-14

Discovered in 1813, the conoscopic interference pattern observed due to light propagating through a crystal, kept between crossed polarizers, shows isochromates and isogyres, respectively containing information about the dynamic and geometric phase acquired by the beam. We propose and demonstrate a closed-fringe Fourier analysis method to disentangle the isogyres from the isochromates, leading us to the azimuthally varying geometric phase and its manifestation as isogyres. This azimuthally varying geometric phase is shown to be the underlying mechanism for the spin-to-orbital angular momentum conversion observed in a diverging optical field propagating through a z-cut uniaxial crystal. We extend the formalism to study the optical activity mediated uniaxial-to-biaxial transformation due to a weak transverse electric field applied across the crystal. Closely associated with the phase and polarization singularities of the optical field, the formalism enables us to understand crystal optics in a new way, paving the way to anticipate several emerging phenomena.

Mode power distribution effect in white-light multimode fiber extrinsic Fabry-Perot interferometric sensor systems.

PubMed

Han, Ming; Wang, Anbo

2006-05-01

Theoretical and experimental results have shown that mode power distribution (MPD) variations could significantly vary the phase of spectral fringes from multimode fiber extrinsic Fabry-Perot interferometric (MMF-EFPI) sensor systems, owing to the fact that different modes introduce different extra phase shifts resulting from the coupling of modes reflected at the second surface to the lead-in fiber end. This dependence of fringe pattern on MPD could cause measurement errors in signal demodulation methods of white-light MMF-EFPI sensors that implement the phase information of the fringes.

A calibration method immune to the projector errors in fringe projection profilometry

NASA Astrophysics Data System (ADS)

Zhang, Ruihua; Guo, Hongwei

2017-08-01

In fringe projection technique, system calibration is a tedious task to establish the mapping relationship between the object depths and the fringe phases. Especially, it is not easy to accurately determine the parameters of the projector in this system, which may induce errors in the measurement results. To solve this problem, this paper proposes a new calibration by using the cross-ratio invariance in the system geometry for determining the phase-to-depth relations. In it, we analyze the epipolar eometry of the fringe projection system. On each epipolar plane, the depth variation along an incident ray induces the pixel movement along the epipolar line on the image plane of the camera. These depth variations and pixel movements can be connected by use of the projective transformations, under which condition the cross-ratio for each of them keeps invariant. Based on this fact, we suggest measuring the depth map by use of this cross-ratio invariance. Firstly, we shift the reference board in its perpendicular direction to three positions with known depths, and measure their phase maps as the reference phase maps; and secondly, when measuring an object, we calculate the object depth at each pixel by equating the cross-ratio of the depths to that of the corresponding pixels having the same phase on the image plane of the camera. This method is immune to the errors sourced from the projector, including the distortions both in the geometric shapes and in the intensity profiles of the projected fringe patterns.The experimental results demonstrate the proposed method to be feasible and valid.

Fringe Benefits Available to Public School Teachers in the Southeast. Research Report. Occasional Papers in Educational Policy Analysis.

ERIC Educational Resources Information Center

Mabry, Rodney H.; And Others

This project measured and evaluated the fringe benefit element of the teacher compensation package available in the 12 Southeastern Regional Council member states: Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virgina. Data were collected by contacting members…

Analysis of Professional Fringe Benefits, 1978-79. OMNI Report.

ERIC Educational Resources Information Center

Vater, James J.; Riddle, Richard A.

This report contains data collected from 275 Pennsylvania school districts for the 1978-79 school year. The data reflect policies and practices affecting fringe benefits for professional employees. The report is divided into three major sections. The first section presents comparative data for 30 variables on a statewide, size, and wealth basis.…

Analysis of Professional Fringe Benefits 1977-78. OMNI Report.

ERIC Educational Resources Information Center

Caldwell, William E.; Vater, James J.

This report contains data collected from 275 Pennsylvania school districts for the 1977-78 school year. The data reflect policies and practices affecting fringe benefits for professional employees. The report is divided into three major sections. The first section presents comparative data for 30 variables on a statewide, size, and wealth basis.…

Electro-optic fringe locking and photometric tuning using a two-stage Mach-Zehnder lithium niobate waveguide for high-contrast mid-infrared interferometry

NASA Astrophysics Data System (ADS)

Martin, Guillermo; Heidmann, Samuel; Rauch, Jean-Yves; Jocou, Laurent; Courjal, Nadège

2014-03-01

We present an optimization process to improve the rejection ratio in integrated beam combiners by locking the dark fringe and then monitoring its intensity. The method proposed here uses the electro-optic effect of lithium niobate in order to lock the dark fringe and to real-time balance the photometric flux by means of a two-stage Mach-Zehnder interferometer waveguide. By applying a control voltage on the output Y-junction, we are able to lock the phase and stay in the dark fringe, while an independent second voltage is applied on the first-stage intensity modulator, to finely balance the photometries. We have obtained a rejection ratio of 4600 (36.6 dB) at 3.39 μm in transverse electric polarization, corresponding to 99.98% fringe contrast, and shown that the system can compensate external phase perturbations (a piston variation of 100 nm) up to around 1 kHz. We also show the preliminary results of this process on wide-band modulation, where a contrast of 38% in 3.25- to 3.65-μm spectral range is obtained. These preliminary results on wide-band need to be optimized, in particular, for reducing scattered light of the device at the Y-junction. We expect this active method to be useful in high-contrast interferometry, in particular, for astronomical spatial projects actually under study.

Motion-oriented high speed 3-D measurements by binocular fringe projection using binary aperiodic patterns.

PubMed

Feng, Shijie; Chen, Qian; Zuo, Chao; Tao, Tianyang; Hu, Yan; Asundi, Anand

2017-01-23

Fringe projection is an extensively used technique for high speed three-dimensional (3-D) measurements of dynamic objects. To precisely retrieve a moving object at pixel level, researchers prefer to project a sequence of fringe images onto its surface. However, the motion often leads to artifacts in reconstructions due to the sequential recording of the set of patterns. In order to reduce the adverse impact of the movement, we present a novel high speed 3-D scanning technique combining the fringe projection and stereo. Firstly, promising measuring speed is achieved by modifying the traditional aperiodic sinusoidal patterns so that the fringe images can be cast at kilohertz with the widely used defocusing strategy. Next, a temporal intensity tracing algorithm is developed to further alleviate the influence of motion by accurately tracing the ideal intensity for stereo matching. Then, a combined cost measure is suggested to robustly estimate the cost for each pixel and lastly a three-step framework of refinement follows not only to eliminate outliers caused by the motion but also to obtain sub-pixel disparity results for 3-D reconstructions. In comparison with the traditional method where the effect of motion is not considered, experimental results show that the reconstruction accuracy for dynamic objects can be improved by an order of magnitude with the proposed method.

Iterated unscented Kalman filter for phase unwrapping of interferometric fringes.

PubMed

Xie, Xianming

2016-08-22

A fresh phase unwrapping algorithm based on iterated unscented Kalman filter is proposed to estimate unambiguous unwrapped phase of interferometric fringes. This method is the result of combining an iterated unscented Kalman filter with a robust phase gradient estimator based on amended matrix pencil model, and an efficient quality-guided strategy based on heap sort. The iterated unscented Kalman filter that is one of the most robust methods under the Bayesian theorem frame in non-linear signal processing so far, is applied to perform simultaneously noise suppression and phase unwrapping of interferometric fringes for the first time, which can simplify the complexity and the difficulty of pre-filtering procedure followed by phase unwrapping procedure, and even can remove the pre-filtering procedure. The robust phase gradient estimator is used to efficiently and accurately obtain phase gradient information from interferometric fringes, which is needed for the iterated unscented Kalman filtering phase unwrapping model. The efficient quality-guided strategy is able to ensure that the proposed method fast unwraps wrapped pixels along the path from the high-quality area to the low-quality area of wrapped phase images, which can greatly improve the efficiency of phase unwrapping. Results obtained from synthetic data and real data show that the proposed method can obtain better solutions with an acceptable time consumption, with respect to some of the most used algorithms.

Denoising in digital speckle pattern interferometry using wave atoms.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2007-05-15

We present an effective method for speckle noise removal in digital speckle pattern interferometry, which is based on a wave-atom thresholding technique. Wave atoms are a variant of 2D wavelet packets with a parabolic scaling relation and improve the sparse representation of fringe patterns when compared with traditional expansions. The performance of the denoising method is analyzed by using computer-simulated fringes, and the results are compared with those produced by wavelet and curvelet thresholding techniques. An application of the proposed method to reduce speckle noise in experimental data is also presented.

Phase accuracy evaluation for phase-shifting fringe projection profilometry based on uniform-phase coded image

NASA Astrophysics Data System (ADS)

Zhang, Chunwei; Zhao, Hong; Zhu, Qian; Zhou, Changquan; Qiao, Jiacheng; Zhang, Lu

2018-06-01

Phase-shifting fringe projection profilometry (PSFPP) is a three-dimensional (3D) measurement technique widely adopted in industry measurement. It recovers the 3D profile of measured objects with the aid of the fringe phase. The phase accuracy is among the dominant factors that determine the 3D measurement accuracy. Evaluation of the phase accuracy helps refine adjustable measurement parameters, contributes to evaluating the 3D measurement accuracy, and facilitates improvement of the measurement accuracy. Although PSFPP has been deeply researched, an effective, easy-to-use phase accuracy evaluation method remains to be explored. In this paper, methods based on the uniform-phase coded image (UCI) are presented to accomplish phase accuracy evaluation for PSFPP. These methods work on the principle that the phase value of a UCI can be manually set to be any value, and once the phase value of a UCI pixel is the same as that of a pixel of a corresponding sinusoidal fringe pattern, their phase accuracy values are approximate. The proposed methods provide feasible approaches to evaluating the phase accuracy for PSFPP. Furthermore, they can be used to experimentally research the property of the random and gamma phase errors in PSFPP without the aid of a mathematical model to express random phase error or a large-step phase-shifting algorithm. In this paper, some novel and interesting phenomena are experimentally uncovered with the aid of the proposed methods.

Characterization of depolarizing fringing fields of a liquid crystal spatial light modulator for laser beam steering

NASA Astrophysics Data System (ADS)

Haellstig, Emil J.; Martin, Torleif; Stigwall, Johan; Sjoqvist, Lars; Lindgren, Mikael

2004-02-01

A commercial linear one-dimensional, 1x4096 pixels, zero-twist nematic liquid crystal spatial light modulator (SLM), giving more than 2π phase modulation at λ = 850 nm, was evaluated for beam steering applications. The large ratio (7:1) between the liquid crystal layer thickness and pixel width gives rise to voltage leakage and fringing fields between pixels. Due to the fringing fields the ideal calculated phase patterns cannot be perfectly realized by the device. Losses in high frequency components in the phase patterns were found to limit the maximum deflection angle. The inhomogeneous optical anisotropy of the SLM was determined by modelling of the liquid crystal director distribution within the electrode-pixel structure. The effects of the fringing fields on the amplitude and phase modulation were studied by full vector finite-difference time-domain simulations. It was found that the fringing fields also resulted in coupling into an unwanted polarization mode. Measurements of how this mode coupling affects the beam steering quality were carried out and the results compared with calculated results. A method to compensate for the fringing field effects is discussed and it is shown how the usable steering range of the SLM can be extended to +/- 2 degrees.

Suppression of contrast-related artefacts in phase-measuring structured light techniques

NASA Astrophysics Data System (ADS)

Burke, Jan; Zhong, Liang

2017-06-01

Optical metrology using phase measurements has benefited significantly from the introduction of phase-shifting methods, first in interferometry, then also in fringe projection and fringe reflection. As opposed to interferometry, the latter two techniques generally use a spatiotemporal phase-shifting approach: A sequence of fringe patterns with varying spacing is used, and a phase map of each is generated by temporal phase shifting, to allow unique assignments of projector or screen pixels to camera pixels. One ubiquitous problem with phase-shifting structured-light techniques is that phase artefacts appear near regions of the image where the modulation amplitude of the projected or reflected fringes changes abruptly, e.g. near dirt/dust particles on the surface in deflectometry or bright-dark object colour transitions in fringe projection. Near the bright-dark boundaries, responses in the phase maps appear that are not plausible as actual surface features. The phenomenon has been known for a long time but is usually ignored because it does not compromise the overall reliability of results. In deflectometry, however, often the objective is to find and classify small defects, and of course it is then important to distinguish between bogus phase responses caused by fringe modulation changes, and actual surface defects. We present, for what we believe is the first time, an analytical derivation of the error terms, study the parameters influencing the phase artefacts (in particular the fringe period), and suggest some simple algorithms to minimise them.

Carbon Nanostructure Examined by Lattice Fringe Analysis of High Resolution Transmission Electron Microscopy Images

NASA Technical Reports Server (NTRS)

VanderWal, Randy L.; Tomasek, Aaron J.; Street, Kenneth; Thompson, William K.

2002-01-01

The dimensions of graphitic layer planes directly affect the reactivity of soot towards oxidation and growth. Quantification of graphitic structure could be used to develop and test correlations between the soot nanostructure and its reactivity. Based upon transmission electron microscopy images, this paper provides a demonstration of the robustness of a fringe image analysis code for determining the level of graphitic structure within nanoscale carbon, i.e. soot. Results, in the form of histograms of graphitic layer plane lengths, are compared to their determination through Raman analysis.

Carbon Nanostructure Examined by Lattice Fringe Analysis of High Resolution Transmission Electron Microscopy Images

NASA Technical Reports Server (NTRS)

VanderWal, Randy L.; Tomasek, Aaron J.; Street, Kenneth; Thompson, William K.; Hull, David R.

2003-01-01

The dimensions of graphitic layer planes directly affect the reactivity of soot towards oxidation and growth. Quantification of graphitic structure could be used to develop and test correlations between the soot nanostructure and its reactivity. Based upon transmission electron microscopy images, this paper provides a demonstration of the robustness of a fringe image analysis code for determining the level of graphitic structure within nanoscale carbon, i.e., soot. Results, in the form of histograms of graphitic layer plane lengths, are compared to their determination through Raman analysis.

Applicability of Neural Networks to Etalon Fringe Filtering in Laser Spectrometers

NASA Technical Reports Server (NTRS)

Nicely, J. M.; Hanisco, T. F.; Riris, H.

2018-01-01

We present a neural network algorithm for spectroscopic retrievals of concentrations of trace gases. Using synthetic data we demonstrate that a neural network is well suited for filtering etalon fringes and provides superior performance to conventional least squares minimization techniques. This novel method can improve the accuracy of atmospheric retrievals and minimize biases.

Applicability of neural networks to etalon fringe filtering in laser spectrometers

NASA Astrophysics Data System (ADS)

Nicely, J. M.; Hanisco, T. F.; Riris, H.

2018-05-01

We present a neural network algorithm for spectroscopic retrievals of concentrations of trace gases. Using synthetic data we demonstrate that a neural network is well suited for filtering etalon fringes and provides superior performance to conventional least squares minimization techniques. This novel method can improve the accuracy of atmospheric retrievals and minimize biases.

A multi-frequency inverse-phase error compensation method for projector nonlinear in 3D shape measurement

NASA Astrophysics Data System (ADS)

Mao, Cuili; Lu, Rongsheng; Liu, Zhijian

2018-07-01

In fringe projection profilometry, the phase errors caused by the nonlinear intensity response of digital projectors needs to be correctly compensated. In this paper, a multi-frequency inverse-phase method is proposed. The theoretical model of periodical phase errors is analyzed. The periodical phase errors can be adaptively compensated in the wrapped maps by using a set of fringe patterns. The compensated phase is then unwrapped with multi-frequency method. Compared with conventional methods, the proposed method can greatly reduce the periodical phase error without calibrating measurement system. Some simulation and experimental results are presented to demonstrate the validity of the proposed approach.

Nonlinear regression method for estimating neutral wind and temperature from Fabry-Perot interferometer data.

PubMed

Harding, Brian J; Gehrels, Thomas W; Makela, Jonathan J

2014-02-01

The Earth's thermosphere plays a critical role in driving electrodynamic processes in the ionosphere and in transferring solar energy to the atmosphere, yet measurements of thermospheric state parameters, such as wind and temperature, are sparse. One of the most popular techniques for measuring these parameters is to use a Fabry-Perot interferometer to monitor the Doppler width and breadth of naturally occurring airglow emissions in the thermosphere. In this work, we present a technique for estimating upper-atmospheric winds and temperatures from images of Fabry-Perot fringes captured by a CCD detector. We estimate instrument parameters from fringe patterns of a frequency-stabilized laser, and we use these parameters to estimate winds and temperatures from airglow fringe patterns. A unique feature of this technique is the model used for the laser and airglow fringe patterns, which fits all fringes simultaneously and attempts to model the effects of optical defects. This technique yields accurate estimates for winds, temperatures, and the associated uncertainties in these parameters, as we show with a Monte Carlo simulation.

Improved Goldstein Interferogram Filter Based on Local Fringe Frequency Estimation.

PubMed

Feng, Qingqing; Xu, Huaping; Wu, Zhefeng; You, Yanan; Liu, Wei; Ge, Shiqi

2016-11-23

The quality of an interferogram, which is limited by various phase noise, will greatly affect the further processes of InSAR, such as phase unwrapping. Interferometric SAR (InSAR) geophysical measurements', such as height or displacement, phase filtering is therefore an essential step. In this work, an improved Goldstein interferogram filter is proposed to suppress the phase noise while preserving the fringe edges. First, the proposed adaptive filter step, performed before frequency estimation, is employed to improve the estimation accuracy. Subsequently, to preserve the fringe characteristics, the estimated fringe frequency in each fixed filtering patch is removed from the original noisy phase. Then, the residual phase is smoothed based on the modified Goldstein filter with its parameter alpha dependent on both the coherence map and the residual phase frequency. Finally, the filtered residual phase and the removed fringe frequency are combined to generate the filtered interferogram, with the loss of signal minimized while reducing the noise level. The effectiveness of the proposed method is verified by experimental results based on both simulated and real data.

Improved Goldstein Interferogram Filter Based on Local Fringe Frequency Estimation

PubMed Central

Feng, Qingqing; Xu, Huaping; Wu, Zhefeng; You, Yanan; Liu, Wei; Ge, Shiqi

2016-01-01

The quality of an interferogram, which is limited by various phase noise, will greatly affect the further processes of InSAR, such as phase unwrapping. Interferometric SAR (InSAR) geophysical measurements’, such as height or displacement, phase filtering is therefore an essential step. In this work, an improved Goldstein interferogram filter is proposed to suppress the phase noise while preserving the fringe edges. First, the proposed adaptive filter step, performed before frequency estimation, is employed to improve the estimation accuracy. Subsequently, to preserve the fringe characteristics, the estimated fringe frequency in each fixed filtering patch is removed from the original noisy phase. Then, the residual phase is smoothed based on the modified Goldstein filter with its parameter alpha dependent on both the coherence map and the residual phase frequency. Finally, the filtered residual phase and the removed fringe frequency are combined to generate the filtered interferogram, with the loss of signal minimized while reducing the noise level. The effectiveness of the proposed method is verified by experimental results based on both simulated and real data. PMID:27886081

Space-based detection of wetlands' surface water level changes from L-band SAR interferometry

USGS Publications Warehouse

Wdowinski, S.; Kim, S.-W.; Amelung, F.; Dixon, T.H.; Miralles-Wilhelm, F.; Sonenshein, R.

2008-01-01

Interferometric processing of JERS-1 L-band Synthetic Aperture Radar (SAR) data acquired over south Florida during 1993-1996 reveals detectable surface changes in the Everglades wetlands. Although our study is limited to south Florida it has implication for other large-scale wetlands, because south Florida wetlands have diverse vegetation types and both managed and natural flow environments. Our analysis reveals that interferometric coherence level is sensitive to wetland vegetation type and to the interferogram time span. Interferograms with time spans less than six months maintain phase observations for all wetland types, allowing characterization of water level changes in different wetland environments. The most noticeable changes occur between the managed and the natural flow wetlands. In the managed wetlands, fringes are organized, follow patterns related to some of the managed water control structures and have high fringe-rate. In the natural flow areas, fringes are irregular and have a low fringe-rate. The high fringe rate in managed areas reflects dynamic water topography caused by high flow rate due to gate operation. Although this organized fringe pattern is not characteristic of most large-scale wetlands, the high level of water level change enables accurate estimation of the wetland InSAR technique, which lies in the range of 5-10??cm. The irregular and low rate fringe pattern in the natural flow area reflects uninterrupted flow that diffuses water efficiently and evenly. Most of the interferograms in the natural flow area show an elongated fringe located along the transitional zone between salt- and fresh-water wetlands, reflecting water level changes due to ocean tides. ?? 2007 Elsevier Inc. All rights reserved.

Three-dimensional shape measurement and calibration for fringe projection by considering unequal height of the projector and the camera

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu Feipeng; Shi Hongjian; Bai Pengxiang

In fringe projection, the CCD camera and the projector are often placed at equal height. In this paper, we will study the calibration of an unequal arrangement of the CCD camera and the projector. The principle of fringe projection with two-dimensional digital image correlation to acquire the profile of object surface is described in detail. By formula derivation and experiment, the linear relationship between the out-of-plane calibration coefficient and the y coordinate is clearly found. To acquire the three-dimensional (3D) information of an object correctly, this paper presents an effective calibration method with linear least-squares fitting, which is very simplemore » in principle and calibration. Experiments are implemented to validate the availability and reliability of the calibration method.« less

3D absolute shape measurement of live rabbit hearts with a superfast two-frequency phase-shifting technique

PubMed Central

Wang, Yajun; Laughner, Jacob I.; Efimov, Igor R.; Zhang, Song

2013-01-01

This paper presents a two-frequency binary phase-shifting technique to measure three-dimensional (3D) absolute shape of beating rabbit hearts. Due to the low contrast of the cardiac surface, the projector and the camera must remain focused, which poses challenges for any existing binary method where the measurement accuracy is low. To conquer this challenge, this paper proposes to utilize the optimal pulse width modulation (OPWM) technique to generate high-frequency fringe patterns, and the error-diffusion dithering technique to produce low-frequency fringe patterns. Furthermore, this paper will show that fringe patterns produced with blue light provide the best quality measurements compared to fringe patterns generated with red or green light; and the minimum data acquisition speed for high quality measurements is around 800 Hz for a rabbit heart beating at 180 beats per minute. PMID:23482151

Distance measurement using frequency scanning interferometry with mode-hoped laser

NASA Astrophysics Data System (ADS)

Medhat, M.; Sobee, M.; Hussein, H. M.; Terra, O.

2016-06-01

In this paper, frequency scanning interferometry is implemented to measure distances up to 5 m absolutely. The setup consists of a Michelson interferometer, an external cavity tunable diode laser, and an ultra-low expansion (ULE) Fabry-Pérot (FP) cavity to measure the frequency scanning range. The distance is measured by acquiring simultaneously the interference fringes from, the Michelson and the FP interferometers, while scanning the laser frequency. An online fringe processing technique is developed to calculate the distance from the fringe ratio while removing the parts result from the laser mode-hops without significantly affecting the measurement accuracy. This fringe processing method enables accurate distance measurements up to 5 m with measurements repeatability ±3.9×10-6 L. An accurate translation stage is used to find the FP cavity free-spectral-range and therefore allow accurate measurement. Finally, the setup is applied for the short distance calibration of a laser distance meter (LDM).

Optical Layout Analysis of Polarization Interference Imaging Spectrometer by Jones Calculus in View of both Optical Throughput and Interference Fringe Visibility

NASA Astrophysics Data System (ADS)

Zhang, Xuanni; Zhang, Chunmin

2013-01-01

A polarization interference imaging spectrometer based on Savart polariscope was presented. Its optical throughput was analyzed by Jones calculus. The throughput expression was given, and clearly showed that the optical throughput mainly depended on the intensity of incident light, transmissivity, refractive index and the layout of optical system. The simulation and analysis gave the optimum layout in view of both optical throughput and interference fringe visibility, and verified that the layout of our former design was optimum. The simulation showed that a small deviation from the optimum layout influenced interference fringe visibility little for the optimum one, but influenced severely for others, so a small deviation is admissible in the optimum, and this can mitigate the manufacture difficulty. These results pave the way for further research and engineering design.

SU-E-T-410: Fringe Stability and Phase Shift Measurements in a Michelson Interferometer for Optical Calorimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flores-Martinez, E; Malin, M; DeWerd, L

2014-06-01

Purpose: To identify the variables limiting the resolution of a Michelson interferometer used to measure phase shifts (PS) in water as part of a radiometric calorimeter. Methods: We investigated the output stability of a He-Ne laser and a laser diode. The short and long term stability of the fringe pattern in a Michelson interferometer was tested with different types of lasers, thermal insulation arrangements, damping systems and optical mounts to optimize system performance. PS were induced by electrically heating water in a 1 cm quartz cuvette located in one of the interferometer arms. The PS was calculated from fringe intensitymore » changes and compared to a calculated PS using thermocouple-measured temperature changes in the water. Results: The intensity of the laser diode is more stable, but the gas laser’s profile is more suitable for fringe analysis and has better temporal coherence. The laser requires a warm-up time of 4 hours before its output is stabilized (SNR>95). The fringe’s stability strongly depends on the thermal insulation. When the interferometer is exposed to ambient temperature swings of 0.7 K, it is not possible to stabilize the fringe pattern. Enclosing the system in a 2.5 cm-thick Styrofoam box improves the SNR, but further insulation will be needed to increase the SNR above 50. High frequency noise is significantly reduced by damping the system.Inducing a temperature rise in water, starting at 299 K, the average temperature increase for a 2π PS is 0.29 ± 0.02 K and the proportionality constant is -21.1 ± 0.8 radians/K. This is 5.8% lower than the calculated value using the thermocouple. Conclusion: Interferometric PS measurements of temperature may provide an alternative to thermistors for water calorimetry. The resolution of the current prototype is limited by ambient temperature stability. Calculated and measured thermally-induced PS in water agreed to within 5.8%.« less

Digital photoelastic analysis applied to implant dentistry

NASA Astrophysics Data System (ADS)

Ramesh, K.; Hariprasad, M. P.; Bhuvanewari, S.

2016-12-01

Development of improved designs of implant systems in dentistry have necessitated the study of stress fields in the implant regions of the mandible/maxilla for better understanding of the biomechanics involved. Photoelasticity has been used for various studies related to dental implants in view of whole field visualization of maximum shear stress in the form of isochromatic contours. The potential of digital photoelasticity has not been fully exploited in the field of implant dentistry. In this paper, the fringe field in the vicinity of the connected implants (All-On-Four® concept) is analyzed using recent advances in digital photoelasticity. Initially, a novel 3-D photoelastic model making procedure, to closely mimic all the anatomical features of the human mandible is proposed. By choosing appropriate orientation of the model with respect to the light path, the essential region of interest were sought to be analysed while keeping the model under live loading conditions. Need for a sophisticated software module to carefully identify the model domain has been brought out. For data extraction, five-step method is used and isochromatics are evaluated by twelve fringe photoelasticity. In addition to the isochromatic fringe field, whole field isoclinic data is also obtained for the first time in implant dentistry, which could throw important information in improving the structural stability of the implant systems. Analysis is carried out for the implant in the molar as well as the incisor region. In addition, the interaction effects of loaded molar implant on the incisor area are also studied.

Statistics of Data Fitting: Flaws and Fixes of Polynomial Analysis of Channeled Spectra

NASA Astrophysics Data System (ADS)

Karstens, William; Smith, David

2013-03-01

Starting from general statistical principles, we have critically examined Baumeister's procedure* for determining the refractive index of thin films from channeled spectra. Briefly, the method assumes that the index and interference fringe order may be approximated by polynomials quadratic and cubic in photon energy, respectively. The coefficients of the polynomials are related by differentiation, which is equivalent to comparing energy differences between fringes. However, we find that when the fringe order is calculated from the published IR index for silicon* and then analyzed with Baumeister's procedure, the results do not reproduce the original index. This problem has been traced to 1. Use of unphysical powers in the polynomials (e.g., time-reversal invariance requires that the index is an even function of photon energy), and 2. Use of insufficient terms of the correct parity. Exclusion of unphysical terms and addition of quartic and quintic terms to the index and order polynomials yields significantly better fits with fewer parameters. This represents a specific example of using statistics to determine if the assumed fitting model adequately captures the physics contained in experimental data. The use of analysis of variance (ANOVA) and the Durbin-Watson statistic to test criteria for the validity of least-squares fitting will be discussed. *D.F. Edwards and E. Ochoa, Appl. Opt. 19, 4130 (1980). Supported in part by the US Department of Energy, Office of Nuclear Physics under contract DE-AC02-06CH11357.

Deformation measurement for a rotating deformable lap based on inverse fringe projection

NASA Astrophysics Data System (ADS)

Liao, Min; Zhang, Qican

2015-03-01

The active deformable lap (also namely stressed lap) is an efficient polishing tool in optical manufacturing. To measure the dynamic deformation caused by outside force on a deformable lap is important and helpful to the opticians to ensure the performance of a deformable lap as expected. In this paper, a manual deformable lap was designed to simulate the dynamic deformation of an active stressed lap, and a measurement system was developed based on inverse projected fringe technique to restore the 3D shape. A redesigned inverse fringe has been projected onto the surface of the measured lap, and the deformations of the tested lap become much obvious and can be easily and quickly evaluated by Fourier fringe analysis. Compared with the conventional projection, this technique is more obvious, and it should be a promising one in the deformation measurement of the active stressed lap in optical manufacturing.

Extension of electronic speckle correlation interferometry to large deformations

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Sciammarella, Federico M.

1998-07-01

The process of fringe formation under simultaneous illumination in two orthogonal directions is analyzed. Procedures to extend the applicability of this technique to large deformation and high density of fringes are introduced. The proposed techniques are applied to a number of technical problems. Good agreement is obtained when the experimental results are compared with results obtained by other methods.

A bi-prism interferometer for hard x-ray photons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isakovic, A.F.; Siddons, D.; Stein, A.

2010-04-06

Micro-fabricated bi-prisms have been used to create an interference pattern from an incident hard X-ray beam, and the intensity of the pattern probed with fluorescence from a 30 nm-thick metal film. Maximum fringe visibility exceeded 0.9 owing to the nano-sized probe and the choice of single-crystal prism material. A full near-field analysis is necessary to describe the fringe field intensities, and the transverse coherence lengths were extracted at APS beamline 8-ID-I. It is also shown that the maximum number of fringes is dependent only on the complex refractive index of the prism material.

A fast point-cloud computing method based on spatial symmetry of Fresnel field

NASA Astrophysics Data System (ADS)

Wang, Xiangxiang; Zhang, Kai; Shen, Chuan; Zhu, Wenliang; Wei, Sui

2017-10-01

Aiming at the great challenge for Computer Generated Hologram (CGH) duo to the production of high spatial-bandwidth product (SBP) is required in the real-time holographic video display systems. The paper is based on point-cloud method and it takes advantage of the propagating reversibility of Fresnel diffraction in the propagating direction and the fringe pattern of a point source, known as Gabor zone plate has spatial symmetry, so it can be used as a basis for fast calculation of diffraction field in CGH. A fast Fresnel CGH method based on the novel look-up table (N-LUT) method is proposed, the principle fringe patterns (PFPs) at the virtual plane is pre-calculated by the acceleration algorithm and be stored. Secondly, the Fresnel diffraction fringe pattern at dummy plane can be obtained. Finally, the Fresnel propagation from dummy plan to hologram plane. The simulation experiments and optical experiments based on Liquid Crystal On Silicon (LCOS) is setup to demonstrate the validity of the proposed method under the premise of ensuring the quality of 3D reconstruction the method proposed in the paper can be applied to shorten the computational time and improve computational efficiency.

New approach for identifying the zero-order fringe in variable wavelength interferometry

NASA Astrophysics Data System (ADS)

Galas, Jacek; Litwin, Dariusz; Daszkiewicz, Marek

2016-12-01

The family of VAWI techniques (for transmitted and reflected light) is especially efficient for characterizing objects, when in the interference system the optical path difference exceeds a few wavelengths. The classical approach that consists in measuring the deflection of interference fringes fails because of strong edge effects. Broken continuity of interference fringes prevents from correct identification of the zero order fringe, which leads to significant errors. The family of these methods has been proposed originally by Professor Pluta in the 1980s but that time image processing facilities and computers were hardly available. Automated devices unfold a completely new approach to the classical measurement procedures. The Institute team has taken that new opportunity and transformed the technique into fully automated measurement devices offering commercial readiness of industry-grade quality. The method itself has been modified and new solutions and algorithms simultaneously have extended the field of application. This has concerned both construction aspects of the systems and software development in context of creating computerized instruments. The VAWI collection of instruments constitutes now the core of the Institute commercial offer. It is now practically applicable in industrial environment for measuring textile and optical fibers, strips of thin films, testing of wave plates and nonlinear affects in different materials. This paper describes new algorithms for identifying the zero order fringe, which increases the performance of the system as a whole and presents some examples of measurements of optical elements.

3-D surface profilometry based on modulation measurement by applying wavelet transform method

NASA Astrophysics Data System (ADS)

Zhong, Min; Chen, Feng; Xiao, Chao; Wei, Yongchao

2017-01-01

A new analysis of 3-D surface profilometry based on modulation measurement technique by the application of Wavelet Transform method is proposed. As a tool excelling for its multi-resolution and localization in the time and frequency domains, Wavelet Transform method with good localized time-frequency analysis ability and effective de-noizing capacity can extract the modulation distribution more accurately than Fourier Transform method. Especially for the analysis of complex object, more details of the measured object can be well remained. In this paper, the theoretical derivation of Wavelet Transform method that obtains the modulation values from a captured fringe pattern is given. Both computer simulation and elementary experiment are used to show the validity of the proposed method by making a comparison with the results of Fourier Transform method. The results show that the Wavelet Transform method has a better performance than the Fourier Transform method in modulation values retrieval.

3D fingerprint imaging system based on full-field fringe projection profilometry

NASA Astrophysics Data System (ADS)

Huang, Shujun; Zhang, Zonghua; Zhao, Yan; Dai, Jie; Chen, Chao; Xu, Yongjia; Zhang, E.; Xie, Lili

2014-01-01

As an unique, unchangeable and easily acquired biometrics, fingerprint has been widely studied in academics and applied in many fields over the years. The traditional fingerprint recognition methods are based on the obtained 2D feature of fingerprint. However, fingerprint is a 3D biological characteristic. The mapping from 3D to 2D loses 1D information and causes nonlinear distortion of the captured fingerprint. Therefore, it is becoming more and more important to obtain 3D fingerprint information for recognition. In this paper, a novel 3D fingerprint imaging system is presented based on fringe projection technique to obtain 3D features and the corresponding color texture information. A series of color sinusoidal fringe patterns with optimum three-fringe numbers are projected onto a finger surface. From another viewpoint, the fringe patterns are deformed by the finger surface and captured by a CCD camera. 3D shape data of the finger can be obtained from the captured fringe pattern images. This paper studies the prototype of the 3D fingerprint imaging system, including principle of 3D fingerprint acquisition, hardware design of the 3D imaging system, 3D calibration of the system, and software development. Some experiments are carried out by acquiring several 3D fingerprint data. The experimental results demonstrate the feasibility of the proposed 3D fingerprint imaging system.

On intrinsic nonlinear particle motion in compact synchrotrons

NASA Astrophysics Data System (ADS)

Hwang, Kyung Ryun

Due to the low energy and small curvature characteristics of compact synchrotrons, there can be unexpected features that were not present or negligible in high energy accelerators. Nonlinear kinetics, fringe field effect, and space charge effect are those features which become important for low energy and small curvature accelerators. Nonlinear kinematics can limit the dynamics aperture for compact machine even if it consists of all linear elements. The contribution of the nonlinear kinematics on nonlinear optics parameters are first derived. As the dipole bending radius become smaller, the dipole fringe field effect become stronger. Calculation of the Lie map generator and corresponding mapping equation of dipole fringe field is presented. It is found that the higher order nonlinear potential is inverse proportional to powers of fringe field extent and correction to focusing and low order nonlinear potential is proportional to powers of fringe field extent. The fringe field also found to cause large closed orbit deviation for compact synchrotrons. The 2:1 and 4:1 space charge resonances are known to cause beam loss, emittance growth and halo formation for low energy high intensity beams. By numerical simulations, we observe a higher order 6:2 space charge resonance, which can successfully be understood by the concatenation of 2:1 and 4:1 resonances via canonical perturbation. We also develop an explicit symplectic tracking method for compact electrostatic storage rings and explore the feasibility of electric dipole moment (EDM) measurements.

Bi-dimensional empirical mode decomposition based fringe-like pattern suppression in polarization interference imaging spectrometer

NASA Astrophysics Data System (ADS)

Ren, Wenyi; Cao, Qizhi; Wu, Dan; Jiang, Jiangang; Yang, Guoan; Xie, Yingge; Wang, Guodong; Zhang, Sheqi

2018-01-01

Many observers using interference imaging spectrometer were plagued by the fringe-like pattern(FP) that occurs for optical wavelengths in red and near-infrared region. It brings us more difficulties in the data processing such as the spectrum calibration, information retrieval, and so on. An adaptive method based on the bi-dimensional empirical mode decomposition was developed to suppress the nonlinear FP in polarization interference imaging spectrometer. The FP and corrected interferogram were separated effectively. Meanwhile, the stripes introduced by CCD mosaic was suppressed. The nonlinear interferogram background removal and the spectrum distortion correction were implemented as well. It provides us an alternative method to adaptively suppress the nonlinear FP without prior experimental data and knowledge. This approach potentially is a powerful tool in the fields of Fourier transform spectroscopy, holographic imaging, optical measurement based on moire fringe, etc.

Fast calculation method for computer-generated cylindrical holograms.

PubMed

Yamaguchi, Takeshi; Fujii, Tomohiko; Yoshikawa, Hiroshi

2008-07-01

Since a general flat hologram has a limited viewable area, we usually cannot see the other side of a reconstructed object. There are some holograms that can solve this problem. A cylindrical hologram is well known to be viewable in 360 deg. Most cylindrical holograms are optical holograms, but there are few reports of computer-generated cylindrical holograms. The lack of computer-generated cylindrical holograms is because the spatial resolution of output devices is not great enough; therefore, we have to make a large hologram or use a small object to fulfill the sampling theorem. In addition, in calculating the large fringe, the calculation amount increases in proportion to the hologram size. Therefore, we propose what we believe to be a new calculation method for fast calculation. Then, we print these fringes with our prototype fringe printer. As a result, we obtain a good reconstructed image from a computer-generated cylindrical hologram.

Study on influence of vibration behavior of composite material damage by holography

NASA Astrophysics Data System (ADS)

Guo, Linfeng; Zhao, Zhimin; Gao, Mingjuan; Zhuang, Xianzhong

2006-01-01

Composite material has been applied widely in aeronautics, astronautics and some other fields due to their high strength, light weight and antifatigue and etc. But in the application, composite material may be destroyed or damaged, which may have impact on its further applications. Therefore, study on the influence of behavior of composite material damage becomes a hot research. In this paper, the common composite material for aircraft is used as the test object, and a study is conducted to investigate the influence of vibration behavior of composite material damage. The authors adopt the method of light-carrier wave and time-average holography. Compared the interference fringes of composite materials before and after damage, the width of the interference fringes of hologram of the damaged composite material is narrower than that of the fringes before. It means that the off-plane displacement of each point on the test object is larger than before. Based on the elastic mechanics theory, the off-plane displacement is inverse to the bending stiffness, and the bending stiffness of the test object will decrease after it is damaged. In other words, the vibration property of the composite material changes after damages occur. The research results of the paper show that the results accord with the analysis of theory.

Investigation on the properties of the formation and coherence of intense fringe near nonlinear medium slab

NASA Astrophysics Data System (ADS)

Hu, Yonghua; Qiu, Yaqiong; Li, Yang; Shi, Lin

2018-03-01

Near medium intense (NMI) fringe is a kind of intense fringe which can be formed near Kerr medium in high-power laser beam propagation. The formation properties of NMI fringe and the relations between NMI fringe and related important parameters are systematically investigated. It is found that it is the co-existence of two wirelike phase-typed scatterers in the incident beam spot which is mainly responsible for the high intensity of NMI fringe. From the viewpoint of coherent superposition, the formation process of NMI fringe is analyzed, and the mechanism that NMI fringe is formed by the coherent superposition of the localized bright fringes in the exit field of Kerr medium slab is demonstrated. The fluctuations of NMI fringe properties with beam wavelength, scatterer spacing and object distance are studied, the coherence of NMI fringe are revealed, and the approximate periodicity of the appearance of remarkable NMI fringe for these parameters are obtained. Especially, it is found that the intensity of NMI fringe is very sensitive to scatterer spacing. Besides, the laws about how NMI fringe properties will be changed by the modulation properties of scatterers and the medium thickness are demonstrated.

Examination of tear film smoothness on corneae after refractive surgeries using a noninvasive interferometric method

NASA Astrophysics Data System (ADS)

Szczesna, Dorota H.; Kulas, Zbigniew; Kasprzak, Henryk T.; Stenevi, Ulf

2009-11-01

A lateral shearing interferometer was used to examine the smoothness of the tear film. The information about the distribution and stability of the precorneal tear film is carried out by the wavefront reflected from the surface of tears and coded in interference fringes. Smooth and regular fringes indicate a smooth tear film surface. On corneae after laser in situ keratomileusis (LASIK) or radial keratotomy (RK) surgery, the interference fringes are seldom regular. The fringes are bent on bright lines, which are interpreted as tear film breakups. The high-intensity pattern seems to appear in similar location on the corneal surface after refractive surgery. Our purpose was to extract information about the pattern existing under the interference fringes and calculate its shape reproducibility over time and following eye blinks. A low-pass filter was applied and correlation coefficient was calculated to compare a selected fragment of the template image to each of the following frames in the recorded sequence. High values of the correlation coefficient suggest that irregularities of the corneal epithelium might influence tear film instability and that tear film breakup may be associated with local irregularities of the corneal topography created after the LASIK and RK surgeries.

Telecentric 3D profilometry based on phase-shifting fringe projection.

PubMed

Li, Dong; Liu, Chunyang; Tian, Jindong

2014-12-29

Three dimensional shape measurement in the microscopic range becomes increasingly important with the development of micro manufacturing technology. Microscopic fringe projection techniques offer a fast, robust, and full-field measurement for field sizes from approximately 1 mm² to several cm². However, the depth of field is very small due to the imaging of non-telecentric microscope, which is often not sufficient to measure the complete depth of a 3D-object. And the calibration of phase-to-depth conversion is complicated which need a precision translation stage and a reference plane. In this paper, we propose a novel telecentric phase-shifting projected fringe profilometry for small and thick objects. Telecentric imaging extends the depth of field approximately to millimeter order, which is much larger than that of microscopy. To avoid the complicated phase-to-depth conversion in microscopic fringe projection, we develop a new system calibration method of camera and projector based on telecentric imaging model. Based on these, a 3D reconstruction of telecentric imaging is presented with stereovision aided by fringe phase maps. Experiments demonstrated the feasibility and high measurement accuracy of the proposed system for thick object.

Dispersed Fringe Sensing Analysis - DFSA

NASA Technical Reports Server (NTRS)

Sigrist, Norbert; Shi, Fang; Redding, David C.; Basinger, Scott A.; Ohara, Catherine M.; Seo, Byoung-Joon; Bikkannavar, Siddarayappa A.; Spechler, Joshua A.

2012-01-01

Dispersed Fringe Sensing (DFS) is a technique for measuring and phasing segmented telescope mirrors using a dispersed broadband light image. DFS is capable of breaking the monochromatic light ambiguity, measuring absolute piston errors between segments of large segmented primary mirrors to tens of nanometers accuracy over a range of 100 micrometers or more. The DFSA software tool analyzes DFS images to extract DFS encoded segment piston errors, which can be used to measure piston distances between primary mirror segments of ground and space telescopes. This information is necessary to control mirror segments to establish a smooth, continuous primary figure needed to achieve high optical quality. The DFSA tool is versatile, allowing precise piston measurements from a variety of different optical configurations. DFSA technology may be used for measuring wavefront pistons from sub-apertures defined by adjacent segments (such as Keck Telescope), or from separated sub-apertures used for testing large optical systems (such as sub-aperture wavefront testing for large primary mirrors using auto-collimating flats). An experimental demonstration of the coarse-phasing technology with verification of DFSA was performed at the Keck Telescope. DFSA includes image processing, wavelength and source spectral calibration, fringe extraction line determination, dispersed fringe analysis, and wavefront piston sign determination. The code is robust against internal optical system aberrations and against spectral variations of the source. In addition to the DFSA tool, the software package contains a simple but sophisticated MATLAB model to generate dispersed fringe images of optical system configurations in order to quickly estimate the coarse phasing performance given the optical and operational design requirements. Combining MATLAB (a high-level language and interactive environment developed by MathWorks), MACOS (JPL s software package for Modeling and Analysis for Controlled Optical Systems), and DFSA provides a unique optical development, modeling and analysis package to study current and future approaches to coarse phasing controlled segmented optical systems.

Directly Measuring the Degree of Quantum Coherence using Interference Fringes

NASA Astrophysics Data System (ADS)

Wang, Yi-Tao; Tang, Jian-Shun; Wei, Zhi-Yuan; Yu, Shang; Ke, Zhi-Jin; Xu, Xiao-Ye; Li, Chuan-Feng; Guo, Guang-Can

2017-01-01

Quantum coherence is the most distinguished feature of quantum mechanics. It lies at the heart of the quantum-information technologies as the fundamental resource and is also related to other quantum resources, including entanglement. It plays a critical role in various fields, even in biology. Nevertheless, the rigorous and systematic resource-theoretic framework of coherence has just been developed recently, and several coherence measures are proposed. Experimentally, the usual method to measure coherence is to perform state tomography and use mathematical expressions. Here, we alternatively develop a method to measure coherence directly using its most essential behavior—the interference fringes. The ancilla states are mixed into the target state with various ratios, and the minimal ratio that makes the interference fringes of the "mixed state" vanish is taken as the quantity of coherence. We also use the witness observable to witness coherence, and the optimal witness constitutes another direct method to measure coherence. For comparison, we perform tomography and calculate l1 norm of coherence, which coincides with the results of the other two methods in our situation. Our methods are explicit and robust, providing a nice alternative to the tomographic technique.

Directly Measuring the Degree of Quantum Coherence using Interference Fringes.

PubMed

Wang, Yi-Tao; Tang, Jian-Shun; Wei, Zhi-Yuan; Yu, Shang; Ke, Zhi-Jin; Xu, Xiao-Ye; Li, Chuan-Feng; Guo, Guang-Can

2017-01-13

Quantum coherence is the most distinguished feature of quantum mechanics. It lies at the heart of the quantum-information technologies as the fundamental resource and is also related to other quantum resources, including entanglement. It plays a critical role in various fields, even in biology. Nevertheless, the rigorous and systematic resource-theoretic framework of coherence has just been developed recently, and several coherence measures are proposed. Experimentally, the usual method to measure coherence is to perform state tomography and use mathematical expressions. Here, we alternatively develop a method to measure coherence directly using its most essential behavior-the interference fringes. The ancilla states are mixed into the target state with various ratios, and the minimal ratio that makes the interference fringes of the "mixed state" vanish is taken as the quantity of coherence. We also use the witness observable to witness coherence, and the optimal witness constitutes another direct method to measure coherence. For comparison, we perform tomography and calculate l_{1} norm of coherence, which coincides with the results of the other two methods in our situation. Our methods are explicit and robust, providing a nice alternative to the tomographic technique.

Improving Spectral Results Using Row-by-Row Fourier Transform of Spatial Heterodyne Raman Spectrometer Interferogram.

PubMed

Barnett, Patrick D; Strange, K Alicia; Angel, S Michael

2017-06-01

This work describes a method of applying the Fourier transform to the two-dimensional Fizeau fringe patterns generated by the spatial heterodyne Raman spectrometer (SHRS), a dispersive interferometer, to correct the effects of certain types of optical alignment errors. In the SHRS, certain types of optical misalignments result in wavelength-dependent and wavelength-independent rotations of the fringe pattern on the detector. We describe here a simple correction technique that can be used in post-processing, by applying the Fourier transform in a row-by-row manner. This allows the user to be more forgiving of fringe alignment and allows for a reduction in the mechanical complexity of the SHRS.

Investigation to realize a computationally efficient implementation of the high-order instantaneous-moments-based fringe analysis method

NASA Astrophysics Data System (ADS)

Gorthi, Sai Siva; Rajshekhar, Gannavarpu; Rastogi, Pramod

2010-06-01

Recently, a high-order instantaneous moments (HIM)-operator-based method was proposed for accurate phase estimation in digital holographic interferometry. The method relies on piece-wise polynomial approximation of phase and subsequent evaluation of the polynomial coefficients from the HIM operator using single-tone frequency estimation. The work presents a comparative analysis of the performance of different single-tone frequency estimation techniques, like Fourier transform followed by optimization, estimation of signal parameters by rotational invariance technique (ESPRIT), multiple signal classification (MUSIC), and iterative frequency estimation by interpolation on Fourier coefficients (IFEIF) in HIM-operator-based methods for phase estimation. Simulation and experimental results demonstrate the potential of the IFEIF technique with respect to computational efficiency and estimation accuracy.

Diffraction contrast near heterostructure boundaries--its nature and its application.

PubMed

Bangert, U; Harvey, A J

1993-03-01

Two phenomena of diffraction contrast arising at or near III-V compound heterostructure boundaries are described and quantitatively analyzed. In the first observation alpha/delta-fringe contrast at boundaries inclined to the electron beam is discussed. Theoretical fringe profiles are generated according to the theory by Gevers et al. in 1964, which are then compared with experimental profiles. Applications to the characterization of AlGaAs/GaAs and InGaAsP/InP interfaces regarding composition, abruptness, and lattice tilt are presented. In the second study a new and very sensitive characterization technique for the direct determination of the strain in strained-layer structures is described. The method uses electron microscope images of 90 degrees-wedges, which exhibit a shift in the thickness contours due to strain relaxation at the edge, and compares these to images which are obtained theoretically by implementing finite element strain calculations in wedges in the dynamical theory of diffraction contrast. The considerable potential of this method is demonstrated on the strain analysis of strained GaInAs/GaAs structures.

Numerical analysis of double chirp effect in tapered and linearly chirped fiber Bragg gratings.

PubMed

Markowski, Konrad; Jedrzejewski, Kazimierz; Osuch, Tomasz

2016-06-10

In this paper, a theoretical analysis of recently developed tapered chirped fiber Bragg gratings (TCFBG) written in co-directional and counter-directional configurations is presented. In particular, the effects of the synthesis of chirps resulting from both a fused taper profile and a linearly chirped fringe pattern of the induced refractive index changes within the fiber core are extensively examined. For this purpose, a numerical model based on the transfer matrix method (TMM) and the coupled mode theory (CMT) was developed for such a grating. The impact of TCFBG parameters, such as grating length and steepness of the taper transition, as well as the effect of the fringe pattern chirp rate on the spectral properties of the resulting gratings, are presented. Results show that, by using the appropriate design process, TCFBGs with reduced or enhanced resulting chirp, and thus with widely tailored spectral responses, can be easily achieved. In turn, it reveals a great potential application of such structures. The presented numerical approach provides an excellent tool for TCFBG design.

JPL VLBI Analysis Center Report for 2012

NASA Technical Reports Server (NTRS)

Jacobs, Chris

2013-01-01

This report describes the activities of the JPL VLBI Analysis Center for the year 2012. The highlight of the year was the successful MSL rover Mars landing, which was supported by VLBI-based navigation using our combined spacecraft, celestial reference frame, terrestrial reference frame, earth orientation, and planetary ephemeris VLBI systems. We also supported several other missions with VLBI navigation measurements. A combined NASA-ESA network was demonstrated with first Ka-band fringes to ESA's Malargue, Argentina 35 m. We achieved first fringes with our new digital back end and Mark 5C recorders.

Development and Application of Optical Coherence Elastography for Detection of Mechanical Property Changes Occurring in Early Osteoarthritis

NASA Astrophysics Data System (ADS)

Hirota, Koji

We demonstrate a computationally-efficient method for optical coherence elastography (OCE) based on fringe washout method for a spectral-domain OCT (SD-OCT) system. By sending short pulses of mechanical perturbation with ultrasound or shock wave during the image acquisition of alternating depth profiles, we can extract cross-sectional mechanical assessment of tissue in real-time. This was achieved through a simple comparison of the intensity in adjacent depth profiles acquired during the states of perturbation and non-perturbation in order to quantify the degree of induced fringe washout. Although the results indicate that our OCE technique based on the fringe washout effect is sensitive enough to detect mechanical property changes in biological samples, there is some loss of sensitivity in comparison to previous techniques in order to achieve computationally efficiency and minimum modification in both hardware and software in the OCT system. The tissue phantom study was carried with various agar density samples to characterize our OCE technique. Young's modulus measurements were achieved with the atomic force microscopy (AFM) to correlate to our OCE assessment. Knee cartilage samples of monosodium iodoacetate (MIA) rat models were utilized to replicate cartilage damage of a human model. Our proposed OCE technique along with intensity and AFM measurements were applied to the MIA models to assess the damage. The results from both the phantom study and MIA model study demonstrated the strong capability to assess the changes in mechanical properties of the OCE technique. The correlation between the OCE measurements and the Young's modulus values demonstrated in the OCE data that the stiffer material had less magnitude of fringe washout effect. This result is attributed to the fringe washout effect caused by axial motion that the displacement of the scatterers in the stiffer samples in response to the external perturbation induces less fringe washout effect.

Four-quadrant gratings moiré fringe alignment measurement in proximity lithography.

PubMed

Zhu, Jiangping; Hu, Song; Yu, Junsheng; Zhou, Shaolin; Tang, Yan; Zhong, Min; Zhao, Lixin; Chen, Minyong; Li, Lanlan; He, Yu; Jiang, Wei

2013-02-11

This paper aims to deal with a four-quadrant gratings alignment method benefiting from phase demodulation for proximity lithography, which combines the advantages of interferometry with image processing. Both the mask alignment mark and the wafer alignment mark consist of four sets of gratings, which bring the convenience and simplification of realization for coarse alignment and fine alignment. Four sets of moiré fringes created by superposing the mask alignment mark and the wafer alignment mark are highly sensitive to the misalignment between them. And the misalignment can be easily determined through demodulating the phase of moiré fringe without any external reference. Especially, the period and phase distribution of moiré fringes are unaffected by the gap between the mask and the wafer, not excepting the wavelength of alignment illumination. Disturbance from the illumination can also be negligible, which enhances the technological adaptability. The experimental results bear out the feasibility and rationality of our designed approach.

Phase compensation with fiber optic surface profile acquisition and reconstruction system

NASA Astrophysics Data System (ADS)

Bo, En; Duan, Fajie; Feng, Fan; Lv, Changrong; Xiao, Fu; Huang, Tingting

2015-02-01

A fiber-optic sinusoidal phase modulating (SPM) interferometer was proposed for the acquisition and reconstruction of three-dimensional (3-D) surface profile. Sinusoidal phase modulation was induced by controlling the injection current of light source. The surface profile was constructed on the basis of fringe projection. Fringe patterns are vulnerable to external disturbances such as mechanical vibration and temperature fluctuation, which cause phase drift in the interference signal and decrease measuring accuracy. A closed-loop feedback phase compensation system was built. In the subsystem, the initial phase of the interference signal, which was caused by the initial optical path difference between interference arms, could be demodulated using phase generated carrier (PGC) method and counted out using coordinated rotation digital computer (CORDIC) , then a compensation voltage was generated for the PZT driver. The bias value of external disturbances superimposed on fringe patterns could be reduced to about 50 mrad, and the phase stability for interference fringes was less than 6 mrad. The feasibility for real-time profile measurement has been verified.

Ghost fringe removal techniques using Lissajous data presentation

DOE PAGES

Erskine, David J.; Eggert, J. H.; Celliers, P. M.; ...

2016-03-14

A VISAR (Velocity Interferometer System for Any Reflector) is a Dopplervelocity interferometer which is an important optical diagnostic in shockwave experiments at the national laboratories, used to measureequation of state(EOS) of materials under extreme conditions. Unwanted reflection of laser light from target windows can produce an additional component to the VISAR fringe record that can distort and obscure the true velocity signal. When accurately removing this so-called ghost artifact component is essential for achieving high accuracy EOSmeasurements, especially when the true light signal is only weakly reflected from the shock front. Independent of the choice of algorithm for processing themore » raw data into a complex fringe signal, we have found it beneficial to plot this signal as a Lissajous and seek the proper center of this path, even under time varying intensity which can shift the perceived center. Moreover, the ghost contribution is then solved by a simple translation in the complex plane that recenters the Lissajous path. For continuous velocity histories, we find that plotting the fringe magnitude vs nonfringing intensity and optimizing linearity is an invaluable tool for determining accurate ghost offsets. For discontinuous velocity histories, we have developed graphically inspired methods which relate the results of two VISARs having different velocity per fringe proportionalities or assumptions of constant fringe magnitude to find the ghost offset. The technique can also remove window reflection artifacts in generic interferometers, such as in the metrology of surfaces.« less

Communication: Development of standing evanescent-wave fluorescence correlation spectroscopy and its application to the lateral diffusion of lipids in a supported lipid bilayer

NASA Astrophysics Data System (ADS)

Otosu, Takuhiro; Yamaguchi, Shoichi

2017-07-01

We present standing evanescent-wave fluorescence correlation spectroscopy (SEW-FCS). This technique utilizes the interference of two evanescent waves which generates a standing evanescent-wave. Fringe-pattern illumination created by a standing evanescent-wave enables us to measure the diffusion coefficients of molecules with a super-resolution corresponding to one fringe width. Because the fringe width can be reliably estimated by a simple procedure, utilization of fringes is beneficial to quantitatively analyze the slow diffusion of molecules in a supported lipid bilayer (SLB), a model biomembrane formed on a solid substrate, with the timescale relevant for reliable FCS analysis. Furthermore, comparison of the data between SEW-FCS and conventional total-internal reflection FCS, which can also be performed by the SEW-FCS instrument, effectively eliminates the artifact due to afterpulsing of the photodiode detector. The versatility of SEW-FCS is demonstrated by its application to various SLBs.

Measurement of residual stresses by the moire method

NASA Astrophysics Data System (ADS)

Sciammarella, C. A.; Albertazzi, A., Jr.

Three different applications of the moire method to the determination of residual stresses and strains are presented. The three applications take advantage of the property of ratings to record the changes of the surface they are printed on. One of the applications deals with thermal residual stresses, another with contact residual stress and the third one is a generalization of the blind hole technique. This last application is based on a computer assisted moire technique and on the generalization of the quasi-heterodyne techniques of fringe pattern analysis.

Deforestation and Malaria on the Amazon Frontier: Larval Clustering of Anopheles darlingi (Diptera: Culicidae) Determines Focal Distribution of Malaria

PubMed Central

Barros, Fábio S. M.; Honório, Nildimar A.

2015-01-01

We performed bimonthly mosquito larval collections during 1 year, in an agricultural settlement in the Brazilian Amazon, as well as an analysis of malaria incidence in neighboring houses. Water collections located at forest fringes were more commonly positive for Anopheles darlingi larvae and Kulldorff spatial analysis pinpointed significant larval clusters at sites directly beneath forest fringes, which were called larval “hotspots.” Remote sensing identified 43 “potential” hotspots. Sampling of these areas revealed an 85.7% positivity rate for A. darlingi larvae. Malaria was correlated with shorter distances to potential hotpots and settlers living within 400 m of potential hotspots had a 2.60 higher risk of malaria. Recently arrived settlers, usually located closer to the tip of the triangularly shaped deforestation imprints of side roads, may be more exposed to malaria due to their proximity to the forest fringe. As deforestation progresses, transmission decreases. However, forest remnants inside deforested areas conferred an increased risk of malaria. We propose a model for explaining frontier malaria in the Amazon: because of adaptation of A. darlingi to the forest fringe ecotone, humans are exposed to an increased transmission risk when in proximity to these areas, especially when small dams are created on naturally running water collections. PMID:26416110

Experimental extractions of particle position from inline holograms using single coefficient of Wigner-Ville analysis

NASA Astrophysics Data System (ADS)

Widjaja, Joewono; Dawprateep, Saowaros; Chuamchaitrakool, Porntip

2017-07-01

Extractions of particle positions from inline holograms using a single coefficient of Wigner-Ville distribution (WVD) are experimentally verified. WVD analysis of holograms gives local variation of fringe frequency. Regardless of an axial position of particles, one of the WVD coefficients has the unique characteristics of having the lowest amplitude and being located on a line with a slope inversely proportional to the particle position. Experimental results obtained using two image sensors with different resolutions verify the feasibility of the present method.

High-speed high-accuracy three-dimensional shape measurement using digital binary defocusing method versus sinusoidal method

NASA Astrophysics Data System (ADS)

Hyun, Jae-Sang; Li, Beiwen; Zhang, Song

2017-07-01

This paper presents our research findings on high-speed high-accuracy three-dimensional shape measurement using digital light processing (DLP) technologies. In particular, we compare two different sinusoidal fringe generation techniques using the DLP projection devices: direct projection of computer-generated 8-bit sinusoidal patterns (a.k.a., the sinusoidal method), and the creation of sinusoidal patterns by defocusing binary patterns (a.k.a., the binary defocusing method). This paper mainly examines their performance on high-accuracy measurement applications under precisely controlled settings. Two different projection systems were tested in this study: a commercially available inexpensive projector and the DLP development kit. Experimental results demonstrated that the binary defocusing method always outperforms the sinusoidal method if a sufficient number of phase-shifted fringe patterns can be used.

High-speed 3D imaging using digital binary defocusing method vs sinusoidal method

NASA Astrophysics Data System (ADS)

Zhang, Song; Hyun, Jae-Sang; Li, Beiwen

2017-02-01

This paper presents our research findings on high-speed 3D imaging using digital light processing (DLP) technologies. In particular, we compare two different sinusoidal fringe generation techniques using the DLP projection devices: direct projection of 8-bit computer generated sinusoidal patterns (a.k.a, the sinusoidal method), and the creation of sinusoidal patterns by defocusing binary patterns (a.k.a., the binary defocusing method). This paper mainly examines their performance on high-accuracy measurement applications under precisely controlled settings. Two different projection systems were tested in this study: the commercially available inexpensive projector, and the DLP development kit. Experimental results demonstrated that the binary defocusing method always outperforms the sinusoidal method if a sufficient number of phase-shifted fringe patterns can be used.

Birefringence dispersion compensation demodulation algorithm for polarized low-coherence interferometry.

PubMed

Wang, Shuang; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Yin, Jinde; Wu, Fan

2013-08-15

A demodulation algorithm based on the birefringence dispersion characteristics for a polarized low-coherence interferometer is proposed. With the birefringence dispersion parameter taken into account, the mathematical model of the polarized low-coherence interference fringes is established and used to extract phase shift information between the measured coherence envelope center and the zero-order fringe, which eliminates the interferometric 2 π ambiguity of locating the zero-order fringe. A pressure measurement experiment using an optical fiber Fabry-Perot pressure sensor was carried out to verify the effectiveness of the proposed algorithm. The experiment result showed that the demodulation precision was 0.077 kPa in the range of 210 kPa, which was improved by 23 times compared to the traditional envelope detection method.

Measuring Close Binary Stars with Speckle Interferometry

DTIC Science & Technology

2014-09-01

extra effort to be measured. One method of observing such binary star systems is to use adaptive optics to correct the atmospheric blur in real-time...simplicity, and with no loss in generalization, this analysis will be reduced to one dimension . From equation (4), it can be seen that the frequency (u...the binary pair are systematically too large , due to the displacement of the minima of the fringes by the atmospheric OTF, when left uncorrected

An Experimental Study of Large Compressive Loads Upon Residual Strain Fields and the Interaction Between Surface Strain Fields Created by Coldworking Fastener Holes.

DTIC Science & Technology

1981-02-01

Strains" (J. of Basic Eng., Vol. 82, Series D, June 1960), pp, 426-434. 10. Morse, S., A.J. Durelli, and C.A. Sciammarella , "Geo- metry of Moire...grid Method, a Practical Moire Stress-analysis Tool" (Exp. Mech., Vol. 7, July 1967), pp. 19A-22A. 20. Sciammarella , C., "Moire-fringe Multiplication

Combined dispersive/interference spectroscopy for producing a vector spectrum

DOEpatents

Erskine, David J.

2002-01-01

A method of measuring the spectral properties of broadband waves that combines interferometry with a wavelength disperser having many spectral channels to produce a fringing spectrum. Spectral mapping, Doppler shifts, metrology of angles, distances and secondary effects such as temperature, pressure, and acceleration which change an interferometer cavity length can be measured accurately by a compact instrument using broadband illumination. Broadband illumination avoids the fringe skip ambiguities of monochromatic waves. The interferometer provides arbitrarily high spectral resolution, simple instrument response, compactness, low cost, high field of view and high efficiency. The inclusion of a disperser increases fringe visibility and signal to noise ratio over an interferometer used alone for broadband waves. The fringing spectrum is represented as a wavelength dependent 2-d vector, which describes the fringe amplitude and phase. Vector mathematics such as generalized dot products rapidly computes average broadband phase shifts to high accuracy. A Moire effect between the interferometer's sinusoidal transmission and the illumination heterodynes high resolution spectral detail to low spectral detail, allowing the use of a low resolution disperser. Multiple parallel interferometer cavities of fixed delay allow the instantaneous mapping of a spectrum, with an instrument more compact for the same spectral resolution than a conventional dispersive spectrometer, and not requiring a scanning delay.

Phase extraction based on iterative algorithm using five-frame crossed fringes in phase measuring deflectometry

NASA Astrophysics Data System (ADS)

Jin, Chengying; Li, Dahai; Kewei, E.; Li, Mengyang; Chen, Pengyu; Wang, Ruiyang; Xiong, Zhao

2018-06-01

In phase measuring deflectometry, two orthogonal sinusoidal fringe patterns are separately projected on the test surface and the distorted fringes reflected by the surface are recorded, each with a sequential phase shift. Then the two components of the local surface gradients are obtained by triangulation. It usually involves some complicated and time-consuming procedures (fringe projection in the orthogonal directions). In addition, the digital light devices (e.g. LCD screen and CCD camera) are not error free. There are quantization errors for each pixel of both LCD and CCD. Therefore, to avoid the complex process and improve the reliability of the phase distribution, a phase extraction algorithm with five-frame crossed fringes is presented in this paper. It is based on a least-squares iterative process. Using the proposed algorithm, phase distributions and phase shift amounts in two orthogonal directions can be simultaneously and successfully determined through an iterative procedure. Both a numerical simulation and a preliminary experiment are conducted to verify the validity and performance of this algorithm. Experimental results obtained by our method are shown, and comparisons between our experimental results and those obtained by the traditional 16-step phase-shifting algorithm and between our experimental results and those measured by the Fizeau interferometer are made.

Digital holographic microscope with low-frequency attenuation filter for position measurement of a nanoparticle.

PubMed

Pham, Quang Duc; Kusumi, Yuichi; Hasegawa, Satoshi; Hayasaki, Yoshio

2012-10-01

We propose a new method for three-dimensional (3D) position measurement of nanoparticles using an in-line digital holographic microscope. The method improves the signal-to-noise ratio of the amplitude of the interference fringes to achieve higher accuracy in the position measurement by increasing weak scattered light from a nanoparticle relative to the reference light by using a low spatial frequency attenuation filter. We demonstrated the improvements of signal-to-noise ratio of the optical system and contrast of the interference fringes, allowing the 3D positions of nanoparticles to be determined more precisely.

Separated Fringe Packet Observations with the CHARA Array. I. Methods and New Orbits for χ Draconis, HD 184467, and HD 198084

NASA Astrophysics Data System (ADS)

Farrington, C. D.; ten Brummelaar, T. A.; Mason, B. D.; Hartkopf, W. I.; McAlister, H. A.; Raghavan, D.; Turner, N. H.; Sturmann, L.; Sturmann, J.; Ridgway, S. T.

2010-06-01

We present the modification of the orbits of χ Draconis and HD 184467, and a completely new orbit for HD 198084, including data taken at the Center for High Angular Resolution Astronomy (CHARA) Array. These data were obtained using a modification of the technique of separated fringe packets (SFPs). The accuracy of the SFP data surpasses that of data taken by speckle, but the technique is much more time and labor intensive. Additionally, using SFPs with the CHARA Array, it is possible to obtain separations below the detection range of speckle interferometry (>=30 mas) above the range in "classic" long-baseline interferometry where fringes from a binary overlap are no longer separated (<=10 mas). Using spectroscopic binary systems with published speckle orbits, we are able to test our new measurements against their ephemerides to calibrate the method as well as produce entirely new orbits for systems with no current astrometric observations.

Fast 3D shape measurements with reduced motion artifacts

NASA Astrophysics Data System (ADS)

Feng, Shijie; Zuo, Chao; Chen, Qian; Gu, Guohua

2017-10-01

Fringe projection is an extensively used technique for high speed three-dimensional (3D) measurements of dynamic objects. However, the motion often leads to artifacts in reconstructions due to the sequential recording of the set of patterns. In order to reduce the adverse impact of the movement, we present a novel high speed 3D scanning technique combining the fringe projection and stereo. Firstly, promising measuring speed is achieved by modifying the traditional aperiodic sinusoidal patterns so that the fringe images can be cast at kilohertz with the widely used defocusing strategy. Next, a temporal intensity tracing algorithm is developed to further alleviate the influence of motion by accurately tracing the ideal intensity for stereo matching. Then, a combined cost measure is suggested to robustly estimate the cost for each pixel. In comparison with the traditional method where the effect of motion is not considered, experimental results show that the reconstruction accuracy for dynamic objects can be improved by an order of magnitude with the proposed method.

A method of reducing background fluctuation in tunable diode laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Yang, Rendi; Dong, Xiaozhou; Bi, Yunfeng; Lv, Tieliang

2018-03-01

Optical interference fringe is the main factor that leads to background fluctuation in gas concentration detection based on tunable diode laser absorption spectroscopy. The interference fringes are generated by multiple reflections or scatterings upon optical surfaces in optical path and make the background signal present an approximated sinusoidal oscillation. To reduce the fluctuation of the background, a method that combines dual tone modulation (DTM) with vibration reflector (VR) is proposed in this paper. The combination of DTM and VR can make the unwanted periodic interference fringes to be averaged out and the effectiveness of the method in reducing background fluctuation has been verified by simulation and real experiments in this paper. In the detection system based on the proposed method, the standard deviation (STD) value of the background signal is decreased to 0.0924 parts per million (ppm), which is reduced by a factor of 16 compared with that of wavelength modulation spectroscopy. The STD value of 0.0924 ppm corresponds to the absorption of 4 . 328 × 10-6Hz - 1 / 2 (with effective optical path length of 4 m and integral time of 0.1 s). Moreover, the proposed method presents a better stable performance in reducing background fluctuation in long time experiments.

49 CFR 25.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 1 2010-10-01 2010-10-01 false Fringe benefits. 25.525 Section 25.525... Employment in Education Programs or Activities Prohibited § 25.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

49 CFR 25.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 1 2012-10-01 2012-10-01 false Fringe benefits. 25.525 Section 25.525... Employment in Education Programs or Activities Prohibited § 25.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

49 CFR 25.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 1 2011-10-01 2011-10-01 false Fringe benefits. 25.525 Section 25.525... Employment in Education Programs or Activities Prohibited § 25.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

49 CFR 25.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 1 2014-10-01 2014-10-01 false Fringe benefits. 25.525 Section 25.525... Employment in Education Programs or Activities Prohibited § 25.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

Dual-sensitivity profilometry with defocused projection of binary fringes.

PubMed

Garnica, G; Padilla, M; Servin, M

2017-10-01

A dual-sensitivity profilometry technique based on defocused projection of binary fringes is presented. Here, two sets of fringe patterns with a sinusoidal profile are produced by applying the same analog low-pass filter (projector defocusing) to binary fringes with a high- and low-frequency spatial carrier. The high-frequency fringes have a binary square-wave profile, while the low-frequency binary fringes are produced with error-diffusion dithering. The binary nature of the binary fringes removes the need for calibration of the projector's nonlinear gamma. Working with high-frequency carrier fringes, we obtain a high-quality wrapped phase. On the other hand, working with low-frequency carrier fringes we found a lower-quality, nonwrapped phase map. The nonwrapped estimation is used as stepping stone for dual-sensitivity temporal phase unwrapping, extending the applicability of the technique to discontinuous (piecewise continuous) surfaces. We are proposing a single defocusing level for faster high- and low-frequency fringe data acquisition. The proposed technique is validated with experimental results.

Quantifying the ozone "weekend effect" at various locations in Phoenix, Arizona

NASA Astrophysics Data System (ADS)

Atkinson-Palombo, Carol M.; Miller, James A.; Balling, Robert C.

Analysis of pollution data from a network of monitors in Maricopa County, Arizona, reveals considerable variation in the magnitude of the ozone "weekend effect" depending on how and where it is measured. We used four separate methods to calculate the weekend effect, all of which showed that the phenomenon is stronger in the urban core, where ozone is produced. Spatial linear regressions show that the magnitude of the weekend effect and the goodness of fit of weekly harmonic cycles in ozone is a function of urbanization, described quantitatively using an index of traffic counts, population, and employment within a 4 km buffer zone of monitoring sites. Analysis of diurnal patterns of ozone as well as oxides of nitrogen (NO x) at a representative site in the urban core supports the hypothesis that lower levels of NO x on Sundays reduce the degree to which ozone is titrated, resulting in a higher minimum and hence mean for that day of the week (DOW). Fringe sites, where ozone concentrations are higher in absolute terms than in the urban core, show almost no "weekend effect," regardless of which of the four individual methods we used. Alternative quantification methods show statistically significant DOW differences in ozone levels in urban fringe locations, albeit out of phase with the weekly cycling of ozone in the urban core. Our findings suggest that multiple metrics need to be used to test for the weekend effect and that the causes of DOW differences in ozone concentrations may be location specific.

10 CFR 1042.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 4 2013-01-01 2013-01-01 false Fringe benefits. 1042.525 Section 1042.525 Energy... Education Programs or Activities Prohibited § 1042.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life...

36 CFR 1211.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Fringe benefits. 1211.525... Prohibited § 1211.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

22 CFR 146.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Fringe benefits. 146.525 Section 146.525... Employment in Education Programs or Activities Prohibited § 146.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

44 CFR 19.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 44 Emergency Management and Assistance 1 2013-10-01 2013-10-01 false Fringe benefits. 19.525... Programs or Activities Prohibited § 19.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or...

22 CFR 146.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Fringe benefits. 146.525 Section 146.525... Employment in Education Programs or Activities Prohibited § 146.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

22 CFR 229.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Fringe benefits. 229.525 Section 229.525... Employment in Education Programs or Activities Prohibited § 229.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

22 CFR 229.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Fringe benefits. 229.525 Section 229.525... Employment in Education Programs or Activities Prohibited § 229.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

44 CFR 19.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 44 Emergency Management and Assistance 1 2010-10-01 2010-10-01 false Fringe benefits. 19.525... Programs or Activities Prohibited § 19.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or...

36 CFR 1211.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 36 Parks, Forests, and Public Property 3 2012-07-01 2012-07-01 false Fringe benefits. 1211.525... Prohibited § 1211.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

44 CFR 19.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 44 Emergency Management and Assistance 1 2012-10-01 2011-10-01 true Fringe benefits. 19.525... Programs or Activities Prohibited § 19.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or...

36 CFR 1211.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Fringe benefits. 1211.525... Prohibited § 1211.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

28 CFR 54.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Fringe benefits. 54.525 Section 54.525... in Employment in Education Programs or Activities Prohibited § 54.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

10 CFR 1042.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 4 2014-01-01 2014-01-01 false Fringe benefits. 1042.525 Section 1042.525 Energy... Education Programs or Activities Prohibited § 1042.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life...

32 CFR 196.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 32 National Defense 2 2012-07-01 2012-07-01 false Fringe benefits. 196.525 Section 196.525... Prohibited § 196.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

22 CFR 229.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Fringe benefits. 229.525 Section 229.525... Employment in Education Programs or Activities Prohibited § 229.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

22 CFR 229.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Fringe benefits. 229.525 Section 229.525... Employment in Education Programs or Activities Prohibited § 229.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

32 CFR 196.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 32 National Defense 2 2011-07-01 2011-07-01 false Fringe benefits. 196.525 Section 196.525... Prohibited § 196.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

36 CFR 1211.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 36 Parks, Forests, and Public Property 3 2014-07-01 2014-07-01 false Fringe benefits. 1211.525... Prohibited § 1211.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

22 CFR 146.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Fringe benefits. 146.525 Section 146.525... Employment in Education Programs or Activities Prohibited § 146.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

28 CFR 54.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Fringe benefits. 54.525 Section 54.525... in Employment in Education Programs or Activities Prohibited § 54.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

44 CFR 19.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 44 Emergency Management and Assistance 1 2014-10-01 2014-10-01 false Fringe benefits. 19.525... Programs or Activities Prohibited § 19.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or...

32 CFR 196.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 32 National Defense 2 2010-07-01 2010-07-01 false Fringe benefits. 196.525 Section 196.525... Prohibited § 196.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

28 CFR 54.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Fringe benefits. 54.525 Section 54.525... in Employment in Education Programs or Activities Prohibited § 54.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

22 CFR 146.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Fringe benefits. 146.525 Section 146.525... Employment in Education Programs or Activities Prohibited § 146.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

22 CFR 229.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Fringe benefits. 229.525 Section 229.525... Employment in Education Programs or Activities Prohibited § 229.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

32 CFR 196.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 32 National Defense 2 2014-07-01 2014-07-01 false Fringe benefits. 196.525 Section 196.525... Prohibited § 196.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

28 CFR 54.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 28 Judicial Administration 2 2011-07-01 2011-07-01 false Fringe benefits. 54.525 Section 54.525... in Employment in Education Programs or Activities Prohibited § 54.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

10 CFR 1042.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 4 2012-01-01 2012-01-01 false Fringe benefits. 1042.525 Section 1042.525 Energy... Education Programs or Activities Prohibited § 1042.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life...

22 CFR 146.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Fringe benefits. 146.525 Section 146.525... Employment in Education Programs or Activities Prohibited § 146.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

32 CFR 196.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 32 National Defense 2 2013-07-01 2013-07-01 false Fringe benefits. 196.525 Section 196.525... Prohibited § 196.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

44 CFR 19.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 44 Emergency Management and Assistance 1 2011-10-01 2011-10-01 false Fringe benefits. 19.525... Programs or Activities Prohibited § 19.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or...

10 CFR 1042.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 4 2011-01-01 2011-01-01 false Fringe benefits. 1042.525 Section 1042.525 Energy... Education Programs or Activities Prohibited § 1042.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life...

10 CFR 1042.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Fringe benefits. 1042.525 Section 1042.525 Energy... Education Programs or Activities Prohibited § 1042.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life...

Apparatus for direct-to-digital spatially-heterodyned holography

DOEpatents

Thomas, Clarence E.; Hanson, Gregory R.

2006-12-12

An apparatus operable to record a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis includes: a laser; a beamsplitter optically coupled to the laser; an object optically coupled to the beamsplitter; a focusing lens optically coupled to both the beamsplitter and the object; a digital recorder optically coupled to the focusing lens; and a computer that performs a Fourier transform, applies a digital filter, and performs an inverse Fourier transform. A reference beam and an object beam are focused by the focusing lens at a focal plane of the digital recorder to form a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis which is recorded by the digital recorder, and the computer transforms the recorded spatially low-frequency heterodyne hologram including spatially heterodyne fringes and shifts axes in Fourier space to sit on top of a heterodyne carrier frequency defined by an angle between the reference beam and the object beam and cuts off signals around an original origin before performing the inverse Fourier transform.

A Moire Fringing Spectrometer for Extra-Solar Planet Searches

NASA Astrophysics Data System (ADS)

van Eyken, J. C.; Ge, J.; Mahadevan, S.; De Witt, C.; Ramsey, L. W.; Berger, D.; Shaklan, S.; Pan, X.

2001-12-01

We have developed a prototype moire fringing spectrometer for high precision radial velocity measurements for the detection of extra-solar planets. This combination of Michelson interferometer and spectrograph overlays an interferometer comb on a medium resolution stellar spectrum, producing Moire patterns. Small changes in the doppler shift of the spectrum lead to corresponding large shifts in the Moire pattern (Moire magnification). The sinusoidal shape of the Moire fringes enables much simpler measurement of these shifts than in standard echelle spectrograph techniques, facilitating high precision measurements with a low cost instrument. Current data analysis software we have developed has produced short-term repeatability (over a few hours) to 5-10m/s, and future planned improvements based on previous experiments should reduce this significantly. We plan eventually to carry out large scale surveys for low mass companions around other stars. This poster will present new results obtained in the lab and at the HET and Palomar 5m telescopes, the theory of the instrument, and data analysis techniques.

31 CFR 28.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 31 Money and Finance: Treasury 1 2014-07-01 2014-07-01 false Fringe benefits. 28.525 Section 28... the Basis of Sex in Employment in Education Programs or Activities Prohibited § 28.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any...

6 CFR 17.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 6 Domestic Security 1 2014-01-01 2014-01-01 false Fringe benefits. 17.525 Section 17.525 Domestic... in Employment in Education Programs or Activities Prohibited § 17.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, the term fringe benefits means any medical...

40 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 1 2012-07-01 2012-07-01 false Fringe benefits. 5.525 Section 5.525... in Employment in Education Programs or Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

29 CFR 36.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 1 2010-07-01 2010-07-01 true Fringe benefits. 36.525 Section 36.525 Labor Office of the... Activities Prohibited § 36.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

41 CFR 101-4.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 41 Public Contracts and Property Management 2 2013-07-01 2012-07-01 true Fringe benefits. 101-4... in Employment in Education Programs or Activities Prohibited § 101-4.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

43 CFR 41.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Fringe benefits. 41.525 Section 41.525... in Employment in Education Programs or Activities Prohibited § 41.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

43 CFR 41.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Fringe benefits. 41.525 Section 41.525... in Employment in Education Programs or Activities Prohibited § 41.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

14 CFR 1253.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Fringe benefits. 1253.525 Section 1253.525... in Employment in Education Programs or Activities Prohibited § 1253.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

41 CFR 101-4.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 41 Public Contracts and Property Management 2 2012-07-01 2012-07-01 false Fringe benefits. 101-4... in Employment in Education Programs or Activities Prohibited § 101-4.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

31 CFR 28.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 31 Money and Finance: Treasury 1 2012-07-01 2012-07-01 false Fringe benefits. 28.525 Section 28... the Basis of Sex in Employment in Education Programs or Activities Prohibited § 28.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any...

10 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 1 2011-01-01 2011-01-01 false Fringe benefits. 5.525 Section 5.525 Energy NUCLEAR... Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

31 CFR 28.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 31 Money and Finance: Treasury 1 2011-07-01 2011-07-01 false Fringe benefits. 28.525 Section 28... the Basis of Sex in Employment in Education Programs or Activities Prohibited § 28.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any...

45 CFR 86.56 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 45 Public Welfare 1 2014-10-01 2014-10-01 false Fringe benefits. 86.56 Section 86.56 Public... Basis of Sex in Employment in Education Programs or Activities Prohibited § 86.56 Fringe benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital...

40 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 1 2011-07-01 2011-07-01 false Fringe benefits. 5.525 Section 5.525... in Employment in Education Programs or Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

41 CFR 101-4.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 41 Public Contracts and Property Management 2 2010-07-01 2010-07-01 true Fringe benefits. 101-4... in Employment in Education Programs or Activities Prohibited § 101-4.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

45 CFR 86.56 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 45 Public Welfare 1 2012-10-01 2012-10-01 false Fringe benefits. 86.56 Section 86.56 Public... Basis of Sex in Employment in Education Programs or Activities Prohibited § 86.56 Fringe benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital...

45 CFR 86.56 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 45 Public Welfare 1 2011-10-01 2011-10-01 false Fringe benefits. 86.56 Section 86.56 Public... Basis of Sex in Employment in Education Programs or Activities Prohibited § 86.56 Fringe benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital...

29 CFR 36.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 1 2013-07-01 2013-07-01 false Fringe benefits. 36.525 Section 36.525 Labor Office of the... Activities Prohibited § 36.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

41 CFR 101-4.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 41 Public Contracts and Property Management 2 2014-07-01 2012-07-01 true Fringe benefits. 101-4... in Employment in Education Programs or Activities Prohibited § 101-4.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

10 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 1 2010-01-01 2010-01-01 false Fringe benefits. 5.525 Section 5.525 Energy NUCLEAR... Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

45 CFR 86.56 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 45 Public Welfare 1 2013-10-01 2013-10-01 false Fringe benefits. 86.56 Section 86.56 Public... Basis of Sex in Employment in Education Programs or Activities Prohibited § 86.56 Fringe benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital...

36 CFR § 1211.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 36 Parks, Forests, and Public Property 3 2013-07-01 2012-07-01 true Fringe benefits. § 1211.525... Prohibited § 1211.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

10 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 1 2013-01-01 2013-01-01 false Fringe benefits. 5.525 Section 5.525 Energy NUCLEAR... Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

31 CFR 28.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Fringe benefits. 28.525 Section 28... the Basis of Sex in Employment in Education Programs or Activities Prohibited § 28.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any...

10 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 1 2012-01-01 2012-01-01 false Fringe benefits. 5.525 Section 5.525 Energy NUCLEAR... Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

14 CFR 1253.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Fringe benefits. 1253.525 Section 1253.525... in Employment in Education Programs or Activities Prohibited § 1253.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

31 CFR 28.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 31 Money and Finance: Treasury 1 2013-07-01 2013-07-01 false Fringe benefits. 28.525 Section 28... the Basis of Sex in Employment in Education Programs or Activities Prohibited § 28.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any...

29 CFR 36.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 1 2014-07-01 2013-07-01 true Fringe benefits. 36.525 Section 36.525 Labor Office of the... Activities Prohibited § 36.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

6 CFR 17.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 6 Domestic Security 1 2011-01-01 2011-01-01 false Fringe benefits. 17.525 Section 17.525 Domestic... in Employment in Education Programs or Activities Prohibited § 17.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, the term fringe benefits means any medical...

14 CFR 1253.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Fringe benefits. 1253.525 Section 1253.525... in Employment in Education Programs or Activities Prohibited § 1253.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

10 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 1 2014-01-01 2014-01-01 false Fringe benefits. 5.525 Section 5.525 Energy NUCLEAR... Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit...

45 CFR 86.56 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 45 Public Welfare 1 2010-10-01 2010-10-01 false Fringe benefits. 86.56 Section 86.56 Public... Basis of Sex in Employment in Education Programs or Activities Prohibited § 86.56 Fringe benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital...

43 CFR 41.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Fringe benefits. 41.525 Section 41.525... in Employment in Education Programs or Activities Prohibited § 41.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

14 CFR 1253.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Fringe benefits. 1253.525 Section 1253.525... in Employment in Education Programs or Activities Prohibited § 1253.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

40 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 1 2013-07-01 2013-07-01 false Fringe benefits. 5.525 Section 5.525... in Employment in Education Programs or Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

6 CFR 17.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 6 Domestic Security 1 2013-01-01 2013-01-01 false Fringe benefits. 17.525 Section 17.525 Domestic... in Employment in Education Programs or Activities Prohibited § 17.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, the term fringe benefits means any medical...

6 CFR 17.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 6 Domestic Security 1 2010-01-01 2010-01-01 false Fringe benefits. 17.525 Section 17.525 Domestic... in Employment in Education Programs or Activities Prohibited § 17.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, the term fringe benefits means any medical...

6 CFR 17.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 6 Domestic Security 1 2012-01-01 2012-01-01 false Fringe benefits. 17.525 Section 17.525 Domestic... in Employment in Education Programs or Activities Prohibited § 17.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, the term fringe benefits means any medical...

43 CFR 41.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Fringe benefits. 41.525 Section 41.525... in Employment in Education Programs or Activities Prohibited § 41.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

41 CFR 101-4.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 41 Public Contracts and Property Management 2 2011-07-01 2007-07-01 true Fringe benefits. 101-4... in Employment in Education Programs or Activities Prohibited § 101-4.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

43 CFR 41.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Fringe benefits. 41.525 Section 41.525... in Employment in Education Programs or Activities Prohibited § 41.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

40 CFR 5.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 1 2014-07-01 2014-07-01 false Fringe benefits. 5.525 Section 5.525... in Employment in Education Programs or Activities Prohibited § 5.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

Cryogenic mirror analysis

NASA Technical Reports Server (NTRS)

Nagy, S.

1988-01-01

Due to extraordinary distances scanned by modern telescopes, optical surfaces in such telescopes must be manufactured to unimaginable standards of perfection of a few thousandths of a centimeter. The detection of imperfections of less than 1/20 of a wavelength of light, for application in the building of the mirror for the Space Infrared Telescope Facility, was undertaken. Because the mirror must be kept very cold while in space, another factor comes into effect: cryogenics. The process to test a specific morror under cryogenic conditions is described; including the follow-up analysis accomplished through computer work. To better illustrate the process and analysis, a Pyrex Hex-Core mirror is followed through the process from the laser interferometry in the lab, to computer analysis via a computer program called FRINGE. This analysis via FRINGE is detailed.

15 CFR 8a.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 15 Commerce and Foreign Trade 1 2012-01-01 2012-01-01 false Fringe benefits. 8a.525 Section 8a.525... in Employment in Education Programs or Activities Prohibited § 8a.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

29 CFR 5.29 - Specific fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 1 2014-07-01 2013-07-01 true Specific fringe benefits. 5.29 Section 5.29 Labor Office of... SUBJECT TO THE CONTRACT WORK HOURS AND SAFETY STANDARDS ACT) Interpretation of the Fringe Benefits Provisions of the Davis-Bacon Act § 5.29 Specific fringe benefits. (a) The act lists all types of fringe...

15 CFR 8a.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 15 Commerce and Foreign Trade 1 2013-01-01 2013-01-01 false Fringe benefits. 8a.525 Section 8a.525... in Employment in Education Programs or Activities Prohibited § 8a.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

15 CFR 8a.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 15 Commerce and Foreign Trade 1 2014-01-01 2014-01-01 false Fringe benefits. 8a.525 Section 8a.525... in Employment in Education Programs or Activities Prohibited § 8a.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

26 CFR 1.61-21 - Taxation of fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 2 2013-04-01 2013-04-01 false Taxation of fringe benefits. 1.61-21 Section 1... § 1.61-21 Taxation of fringe benefits. (a) Fringe benefits—(1) In general. Section 61(a)(1) provides... includes compensation for services, including fees, commissions, fringe benefits, and similar items. For an...

15 CFR 8a.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 1 2011-01-01 2011-01-01 false Fringe benefits. 8a.525 Section 8a.525... in Employment in Education Programs or Activities Prohibited § 8a.525 Fringe benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital...

High resolution x-ray diffraction analysis of annealed low-temperature gallium arsenide

NASA Astrophysics Data System (ADS)

Matyi, R. J.; Melloch, M. R.; Woodall, J. M.

1992-05-01

High resolution x-ray diffraction methods have been used to characterize GaAs grown at low substrate temperatures by molecular beam epitaxy and to examine the effects of post-growth annealing on the structure of the layers. Double crystal rocking curves from the as-deposited epitaxial layer show well-defined interference fringes, indicating a high level of structural perfection despite the presence of excess arsenic. Annealing at temperatures from 700 to 900 °C resulted in a decrease in the perpendicular lattice mismatch between the GaAs grown at low temperature and the substrate from 0.133% to 0.016% and a decrease (but not total elimination) of the visibility of the interference fringes. Triple-crystal diffraction scans around the 004 point in reciprocal space exhibited an increase in the apparent mosaic spread of the epitaxial layer with increasing anneal temperature. The observations are explained in terms of the growth of arsenic precipitates in the epitaxial layer.

Analysis and testing of a new method for drop size measurement using laser scatter interferometry

NASA Technical Reports Server (NTRS)

Bachalo, W. D.; Houser, M. J.

1984-01-01

Research was conducted on a laser light scatter detection method for measuring the size and velocity of spherical particles. The method is based upon the measurement of the interference fringe pattern produced by spheres passing through the intersection of two laser beams. A theoretical analysis of the method was carried out using the geometrical optics theory. Experimental verification of the theory was obtained by using monodisperse droplet streams. Several optical configurations were tested to identify all of the parametric effects upon the size measurements. Both off-axis forward and backscatter light detection were utilized. Simulated spray environments and fuel spray nozzles were used in the evaluation of the method. The measurements of the monodisperse drops showed complete agreement with the theoretical predictions. The method was demonstrated to be independent of the beam intensity and extinction resulting from the surrounding drops. Signal processing concepts were considered and a method was selected for development.

3D mouse shape reconstruction based on phase-shifting algorithm for fluorescence molecular tomography imaging system.

PubMed

Zhao, Yue; Zhu, Dianwen; Baikejiang, Reheman; Li, Changqing

2015-11-10

This work introduces a fast, low-cost, robust method based on fringe pattern and phase shifting to obtain three-dimensional (3D) mouse surface geometry for fluorescence molecular tomography (FMT) imaging. We used two pico projector/webcam pairs to project and capture fringe patterns from different views. We first calibrated the pico projectors and the webcams to obtain their system parameters. Each pico projector/webcam pair had its own coordinate system. We used a cylindrical calibration bar to calculate the transformation matrix between these two coordinate systems. After that, the pico projectors projected nine fringe patterns with a phase-shifting step of 2π/9 onto the surface of a mouse-shaped phantom. The deformed fringe patterns were captured by the corresponding webcam respectively, and then were used to construct two phase maps, which were further converted to two 3D surfaces composed of scattered points. The two 3D point clouds were further merged into one with the transformation matrix. The surface extraction process took less than 30 seconds. Finally, we applied the Digiwarp method to warp a standard Digimouse into the measured surface. The proposed method can reconstruct the surface of a mouse-sized object with an accuracy of 0.5 mm, which we believe is sufficient to obtain a finite element mesh for FMT imaging. We performed an FMT experiment using a mouse-shaped phantom with one embedded fluorescence capillary target. With the warped finite element mesh, we successfully reconstructed the target, which validated our surface extraction approach.

Bricolage: Re-Discovering History through Intermediality and Performance. A Report on the UCT/CityVarsity Production of "A Day, Across" at the Cape Town Fringe 2014

ERIC Educational Resources Information Center

Muftic, Sanjin

2016-01-01

"A Day, Across," performed by the CityVarsity School of Creative Arts at the Cape Town Fringe 2014, was a student production that investigated the link between the youth of South Africa and the centennial of the start of World War I. This paper presents a brief analysis of the rehearsal process as well as certain performance sequences in…

Mathematical expressions using fringe projections for transparent objects

NASA Astrophysics Data System (ADS)

Su, Wei-Hung; Cheng, Chau-Jern

2017-08-01

A setup using fringe projection techniques to perform 3D profile measurements for transparent objects is presented. The related mathematical equations are derived as well. A fringe pattern is illuminated onto the transparent object. Fringes passing through the inspected object are then projected onto a screen. A CCD camera is employed to record the transmitted fringes on the screen. Fringe on the screen are deformed by the refractive index and the surface structure, and therefore are desirable to describe the shape of the inspected sample.

Automated collimation testing by determining the statistical correlation coefficient of Talbot self-images.

PubMed

Rana, Santosh; Dhanotia, Jitendra; Bhatia, Vimal; Prakash, Shashi

2018-04-01

In this paper, we propose a simple, fast, and accurate technique for detection of collimation position of an optical beam using the self-imaging phenomenon and correlation analysis. Herrera-Fernandez et al. [J. Opt.18, 075608 (2016)JOOPDB0150-536X10.1088/2040-8978/18/7/075608] proposed an experimental arrangement for collimation testing by comparing the period of two different self-images produced by a single diffraction grating. Following their approach, we propose a testing procedure based on correlation coefficient (CC) for efficient detection of variation in the size and fringe width of the Talbot self-images and thereby the collimation position. When the beam is collimated, the physical properties of the self-images of the grating, such as its size and fringe width, do not vary from one Talbot plane to the other and are identical; the CC is maximum in such a situation. For the de-collimated position, the size and fringe width of the self-images vary, and correspondingly the CC decreases. Hence, the magnitude of CC is a measure of degree of collimation. Using the method, we could set the collimation position to a resolution of 1 μm, which relates to ±0.25   μ    radians in terms of collimation angle (for testing a collimating lens of diameter 46 mm and focal length 300 mm). In contrast to most collimation techniques reported to date, the proposed technique does not require a translation/rotation of the grating, use of complicated phase evaluation algorithms, or an intricate method for determination of period of the grating or its self-images. The technique is fully automated and provides high resolution and precision.

DSPI technique for nanometer vibration mode measurement

NASA Astrophysics Data System (ADS)

Yue, Kaiduan; Jia, Shuhai; Tan, Yushan

2000-05-01

A time-average DSPI method for nanometer vibration mode measurement is presented in this paper. The phase continuous scan technique is combined with the Bessel fringe-shifting technique to quantitatively analyze the vibration mode by time-average DSPI is used in measurement system. Through the phase continuous scan, the background and speckle items are completely eliminated, which improves the fringe quality and enhances the signal-to-noise ratio of interferogram. There is no need to calibrate the optical phase-shifter exactly in this method. The anti-disturbance capability of this method is higher than that of the phase-stepping technique, so it is robust and easy to be used. In the vibration measurement system, the speckle average technology is used, so the high quality measuring results are obtained.

29 CFR 4.171 - “Bona fide” fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 1 2014-07-01 2013-07-01 true âBona fideâ fringe benefits. 4.171 Section 4.171 Labor... Compliance with Compensation Standards § 4.171 “Bona fide” fringe benefits. (a) To be considered a “bona fide” fringe benefit for purposes of the Act, a fringe benefit plan, fund, or program must constitute a legally...

On-Line Fringe Tracking and Prediction at IOTA

NASA Technical Reports Server (NTRS)

Wilson, Edward; Mah, Robert; Lau, Sonie (Technical Monitor)

1999-01-01

The Infrared/Optical Telescope Array (IOTA) is a multi-aperture Michelson interferometer located on Mt. Hopkins near Tucson, Arizona. To enable viewing of fainter targets, an on-line fringe tracking system is presently under development at NASA Ames Research Center. The system has been developed off-line using actual data from IOTA, and is presently undergoing on-line implementation at IOTA. The system has two parts: (1) a fringe tracking system that identifies the center of a fringe packet by fitting a parametric model to the data; and (2) a fringe packet motion prediction system that uses characteristics of past fringe packets to predict fringe packet motion. Combined, this information will be used to optimize on-line the scanning trajectory, resulting in improved visibility of faint targets. Fringe packet identification is highly accurate and robust (99% of the 4000 fringe packets were identified correctly, the remaining 1% were either out of the scan range or too noisy to be seen) and is performed in 30-90 milliseconds on a Pentium II-based computer. Fringe packet prediction, currently performed using an adaptive linear predictor, delivers a 10% improvement over the baseline of predicting no motion.

Single shot white light interference microscopy with colour fringe analysis for quantitative phase imaging of biological cells

NASA Astrophysics Data System (ADS)

Srivastava, Vishal; Mehta, D. S.

2013-02-01

To quantitatively obtain the phase map of Onion and human red blood cell (RBC) from white light interferogram we used Hilbert transform color fringe analysis technique. The three Red, Blue and Green color components are decomposed from single white light interferogram and Refractive index profile for Red, Blue and Green colour were computed in a completely non-invasive manner for Onion and human RBC. The present technique might be useful for non-invasive determination of the refractive index variation within cells and tissues and morphological features of sample with ease of operation and low cost.

An Extrinsic Fabry-Perot Interferometric Sensor using Intermodal Phase Shifting and Demultiplexing of the Propagating Modes in a Few-Mode Fiber

NASA Astrophysics Data System (ADS)

Chatterjee, Julius

This dissertation demonstrates a fiber-optic phase shifted Fabry-Perot interferometer (PS-FPI) as a sensor using modal demultiplexing. Single wavelength Fabry-Perot interferometers suffer from fringe ambiguity and loss of sensitivity at fringe extremes. These hindrances cause it to be a secondary choice when being selected for a measurement task at hand, and more often than not, white light based sensors are selected in favor of the single wavelength Fabry-Perot sensors. This work aims to introduce a technique involving the demultiplexing of the propagating linearly polarized (LP) modes in few mode fibers to obtain two fringe systems from the same sensing cavity. This results in a few-mode interferometer that effectively has two to three orders of magnitude higher perturbation sensitivity than a conventional few mode interferometer for the same sensing region. In this work, two different modal demultiplexing techniques (MD) are used to demodulate the propagating modes and to obtain two fringe sets. These output fringe sets are shifted in phase with respect to each other by a phase shift due to the propagation of the modes in the fiber-optic layout. A method of controlling this phase shift by straining a length of a two mode fiber located separate from the PS-FPI cavity is demonstrated and corresponding changes in phase shifts are shown. The results show a controllable phase shift for both the MD techniques, which is useful in sensing by permitting quadrature demodulation of interferometric fringes and also results in a novel few-mode sensing system having more than two orders of magnitude sensitivity than conventional few-mode devices.

Use of Holographic Fringe Linearization Interferometry (FLI) for Detection of Defects.

DTIC Science & Technology

1985-11-01

ei FINAL REPORT on Contract F49620-82-C-0001 USE OF HOLOGRAPHIC FRINGE LINEARIZATION INTERFEROMETRY (FLI) FOR DETECTION OF DEFECTS...TECHNICAL RESULTS OF RESEARCH EFFORT ADDITIONAL TO THOSE IN APPENDIXES A THROUGH EI , •5.1 FINITE ELEMENT ANALYSIS OF FLI EXPERIMENTS Throughout this...between exposures in holographic F1.1 appear to and f(x’,t) = ei k,1(x") in Eq. (4). The revised image of Eq. (5) be localized in the space on and about

High-speed three-dimensional shape measurement for dynamic scenes using bi-frequency tripolar pulse-width-modulation fringe projection

NASA Astrophysics Data System (ADS)

Zuo, Chao; Chen, Qian; Gu, Guohua; Feng, Shijie; Feng, Fangxiaoyu; Li, Rubin; Shen, Guochen

2013-08-01

This paper introduces a high-speed three-dimensional (3-D) shape measurement technique for dynamic scenes by using bi-frequency tripolar pulse-width-modulation (TPWM) fringe projection. Two wrapped phase maps with different wavelengths can be obtained simultaneously by our bi-frequency phase-shifting algorithm. Then the two phase maps are unwrapped using a simple look-up-table based number-theoretical approach. To guarantee the robustness of phase unwrapping as well as the high sinusoidality of projected patterns, TPWM technique is employed to generate ideal fringe patterns with slight defocus. We detailed our technique, including its principle, pattern design, and system setup. Several experiments on dynamic scenes were performed, verifying that our method can achieve a speed of 1250 frames per second for fast, dense, and accurate 3-D measurements.

3D-shape of objects with straight line-motion by simultaneous projection of color coded patterns

NASA Astrophysics Data System (ADS)

Flores, Jorge L.; Ayubi, Gaston A.; Di Martino, J. Matías; Castillo, Oscar E.; Ferrari, Jose A.

2018-05-01

In this work, we propose a novel technique to retrieve the 3D shape of dynamic objects by the simultaneous projection of a fringe pattern and a homogeneous light pattern which are both coded in two of the color channels of a RGB image. The fringe pattern, red channel, is used to retrieve the phase by phase-shift algorithms with arbitrary phase-step, while the homogeneous pattern, blue channel, is used to match pixels from the test object in consecutive images, which are acquired at different positions, and thus, to determine the speed of the object. The proposed method successfully overcomes the standard requirement of projecting fringes of two different frequencies; one frequency to extract object information and the other one to retrieve the phase. Validation experiments are presented.

Do Penaeid Shrimps have a Preference for Mangrove Habitats? Distribution Pattern Analysis on Inhaca Island, Mozambique

NASA Astrophysics Data System (ADS)

Rönnbäck, P.; Macia, A.; Almqvist, G.; Schultz, L.; Troell, M.

2002-09-01

Scientific information on how penaeid shrimps are distributed within mangrove ecosystems is scarce, which presents an obstacle for fisheries as well as mangrove management. This study investigated the prime nursery microhabitats for the two major commercial species in Mozambique-Penaeus indicus and Metapenaeus monoceros. Stake net enclosures were used to sample shrimps living among unvegetated shallows and mangroves at Inhaca Island, Mozambique, during three consecutive spring tide periods. Four microhabitats were sampled: (1) sand flat; (2) fringe Avicennia marina on sandy substrate; (3) fringe A. marina on muddy substrate; and (4) interior A. marina adjacent to the supratidal terrestrial margin. P. indicus had a significant preference for fringe mangroves over the adjacent sand flat (P<0·001 and P=0·05). Postlarval shrimps only occupied the sand flat, whereas the mangrove was utilized by postlarval, juvenile and sub-adult life stages. Within the fringe mangrove, there was no correlation between shrimp abundance and organic content of sediment (5·7-11·6 shrimps m-2). Shrimps utilized the most interior margin of the mangroves (0·35 shrimps m-2), although catch rates were significantly lower than in the mangrove fringe (P<0·001). M. monoceros was significantly (P<0·01), more abundant in the sand flat (0·44-2·1 shrimps m-2) than in the mangrove fringe (0·04-0·61 shrimps m-2), although this habitat preference was not evident for juvenile and sub-adult life stages. The results demonstrate the extensive use of mangrove habitats by penaeid shrimps. The confinement to mangroves for P. indicus, but not for M. monoceros, is discussed in the context of habitat characteristics and predation avoidance behaviour. Methodological considerations of the stake net technique are also outlined.

48 CFR 731.372 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Fringe benefits. 731.372 Section 731.372 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT GENERAL....372 Fringe benefits. USAID's policies on certain fringe benefits related to overseas service...

48 CFR 731.372 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Fringe benefits. 731.372 Section 731.372 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT GENERAL....372 Fringe benefits. USAID's policies on certain fringe benefits related to overseas service...

48 CFR 731.372 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Fringe benefits. 731.372 Section 731.372 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT GENERAL....372 Fringe benefits. USAID's policies on certain fringe benefits related to overseas service...

48 CFR 731.372 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 5 2011-10-01 2011-10-01 false Fringe benefits. 731.372 Section 731.372 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT GENERAL....372 Fringe benefits. USAID's policies on certain fringe benefits related to overseas service...

48 CFR 731.372 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Fringe benefits. 731.372 Section 731.372 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT GENERAL....372 Fringe benefits. USAID's policies on certain fringe benefits related to overseas service...

Measurement Of The Deformation Of Rail Track Fastening Clips By Holographic Interferometry

NASA Astrophysics Data System (ADS)

Ennos, A. E.

1985-01-01

One method of attaching railway rails to the sleepers (ties) is to use spring steel clips, mounted on either side of the rail, that exert a downward force on the foot of the rail. In service these will flex with the passing of a train. Holographic interferometry has been used to measure quantitatively the manner in which the spring clips deform when the rail is given a displacement in a prescribed direction. The information can be used both to provide data on the bending and torsion of the clip, and as a means of testing the validity of finite element analysis calculations. Measurements on three different designs of commercial clip were carried out on a section of sleeper holding a short length of rail. A controlled upward displacement of the rail was achieved pneumatically by means of plastic pipes interposed between rail and concrete sleeper. Double exposure holograms were recorded on large photographic plates, allowing views of the fringe patterns from widely spaced directions. The three components of displacement at points along the length of the clip were calculated from fringe information taken from nine directions, using least squares fit to obtain increased accuracy. Rotations of the surface were calculated from the fringe directions and spacings. In addition to deformation measurements of the clip under service conditions, information on local yielding of the clip under increasing stress was also obtained by means of real-time interferometry, using an instant hologram camera.

On the use of video projectors for three-dimensional scanning

NASA Astrophysics Data System (ADS)

Juarez-Salazar, Rigoberto; Diaz-Ramirez, Victor H.; Robledo-Sanchez, Carlos; Diaz-Gonzalez, Gerardo

2017-08-01

Structured light projection is one of the most useful methods for accurate three-dimensional scanning. Video projectors are typically used as the illumination source. However, because video projectors are not designed for structured light systems, some considerations such as gamma calibration must be taken into account. In this work, we present a simple method for gamma calibration of video projectors. First, the experimental fringe patterns are normalized. Then, the samples of the fringe patterns are sorted in ascending order. The sample sorting leads to a simple three-parameter sine curve that is fitted using the Gauss-Newton algorithm. The novelty of this method is that the sorting process removes the effect of the unknown phase. Thus, the resulting gamma calibration algorithm is significantly simplified. The feasibility of the proposed method is illustrated in a three-dimensional scanning experiment.

Control of the coherence behavior in a SFG interferometer through the multipump phases command.

PubMed

Darré, P; Lehmann, L; Grossard, L; Delage, L; Reynaud, F

2018-03-19

In this paper, we report on a novel method to control the coherence behavior in a sum frequency generation interferometer powered by two independent pump lines. At the output of the interferometer, the two incoherent fringe patterns must be superimposed to maximize the contrast. The first step consists in canceling the differential group delay. The second one uses the phase control on one pump to synchronize the fringe patterns. This innovative method is experimentally demonstrated with a setup involving a 1544 nm signal and two pump lines around 1064 nm leading to a converted signal around 630 nm. It can be easily extended to a greater number of pump lines.

Color moiré simulations in contact-type 3-D displays.

PubMed

Lee, B-R; Son, J-Y; Chernyshov, O O; Lee, H; Jeong, I-K

2015-06-01

A new method of color moiré fringe simulation in the contact-type 3-D displays is introduced. The method allows simulating color moirés appearing in the displays, which cannot be approximated by conventional cosine approximation of a line grating. The color moirés are mainly introduced by the line width of the boundary lines between the elemental optics in and plate thickness of viewing zone forming optics. This is because the lines are hiding some parts of pixels under the viewing zone forming optics, and the plate thickness induces a virtual contraction of the pixels. The simulated color moiré fringes are closely matched with those appearing at the displays.

Real-Time and High-Resolution 3D Face Measurement via a Smart Active Optical Sensor.

PubMed

You, Yong; Shen, Yang; Zhang, Guocai; Xing, Xiuwen

2017-03-31

The 3D measuring range and accuracy in traditional active optical sensing, such as Fourier transform profilometry, are influenced by the zero frequency of the captured patterns. The phase-shifting technique is commonly applied to remove the zero component. However, this phase-shifting method must capture several fringe patterns with phase difference, thereby influencing the real-time performance. This study introduces a smart active optical sensor, in which a composite pattern is utilized. The composite pattern efficiently combines several phase-shifting fringes and carrier frequencies. The method can remove zero frequency by using only one pattern. Model face reconstruction and human face measurement were employed to study the validity and feasibility of this method. Results show no distinct decrease in the precision of the novel method unlike the traditional phase-shifting method. The texture mapping technique was utilized to reconstruct a nature-appearance 3D digital face.

Real-Time and High-Resolution 3D Face Measurement via a Smart Active Optical Sensor

PubMed Central

You, Yong; Shen, Yang; Zhang, Guocai; Xing, Xiuwen

2017-01-01

The 3D measuring range and accuracy in traditional active optical sensing, such as Fourier transform profilometry, are influenced by the zero frequency of the captured patterns. The phase-shifting technique is commonly applied to remove the zero component. However, this phase-shifting method must capture several fringe patterns with phase difference, thereby influencing the real-time performance. This study introduces a smart active optical sensor, in which a composite pattern is utilized. The composite pattern efficiently combines several phase-shifting fringes and carrier frequencies. The method can remove zero frequency by using only one pattern. Model face reconstruction and human face measurement were employed to study the validity and feasibility of this method. Results show no distinct decrease in the precision of the novel method unlike the traditional phase-shifting method. The texture mapping technique was utilized to reconstruct a nature-appearance 3D digital face. PMID:28362349

3D measurement using combined Gray code and dual-frequency phase-shifting approach

NASA Astrophysics Data System (ADS)

Yu, Shuang; Zhang, Jing; Yu, Xiaoyang; Sun, Xiaoming; Wu, Haibin; Liu, Xin

2018-04-01

The combined Gray code and phase-shifting approach is a commonly used 3D measurement technique. In this technique, an error that equals integer multiples of the phase-shifted fringe period, i.e. period jump error, often exists in the absolute analog code, which can lead to gross measurement errors. To overcome this problem, the present paper proposes 3D measurement using a combined Gray code and dual-frequency phase-shifting approach. Based on 3D measurement using the combined Gray code and phase-shifting approach, one set of low-frequency phase-shifted fringe patterns with an odd-numbered multiple of the original phase-shifted fringe period is added. Thus, the absolute analog code measured value can be obtained by the combined Gray code and phase-shifting approach, and the low-frequency absolute analog code measured value can also be obtained by adding low-frequency phase-shifted fringe patterns. Then, the corrected absolute analog code measured value can be obtained by correcting the former by the latter, and the period jump errors can be eliminated, resulting in reliable analog code unwrapping. For the proposed approach, we established its measurement model, analyzed its measurement principle, expounded the mechanism of eliminating period jump errors by error analysis, and determined its applicable conditions. Theoretical analysis and experimental results show that the proposed approach can effectively eliminate period jump errors, reliably perform analog code unwrapping, and improve the measurement accuracy.

Planning criteria for express bus-fringe parking operations : volume I of express bus-fringe parking planning methodology.

DOT National Transportation Integrated Search

1975-01-01

Tripmaker reactions to two recent express bus-fringe parking operations in Richmond and Norfolk-Virginia Beach Virginia are examined. This travel behavior's interpreted to establish planning and design guidelines for locating and designing fringe lot...

Undersampled digital holographic interferometry

NASA Astrophysics Data System (ADS)

Halaq, H.; Demoli, N.; Sović, I.; Šariri, K.; Torzynski, M.; Vukičević, D.

2008-04-01

In digital holography, primary holographic fringes are recorded using a matricial CCD sensor. Because of the low spatial resolution of currently available CCD arrays, the angle between the reference and object beams must be limited to a few degrees. Namely, due to the digitization involved, the Shannon's criterion imposes that the Nyquist sampling frequency be at least twice the highest signal frequency. This means that, in the case of the recording of an interference fringe pattern by a CCD sensor, the inter-fringe distance must be larger than twice the pixel period. This in turn limits the angle between the object and the reference beams. If this angle, in a practical holographic interferometry measuring setup, cannot be limited to the required value, aliasing will occur in the reconstructed image. In this work, we demonstrate that the low spatial frequency metrology data could nevertheless be efficiently extracted by careful choice of twofold, and even threefold, undersampling of the object field. By combining the time-averaged recording with subtraction digital holography method, we present results for a loudspeaker membrane interferometric study obtained under strong aliasing conditions. High-contrast fringes, as a consequence of the vibration modes of the membrane, are obtained.

Fringe-shifting single-projector moiré topography application for cotyle implantate abrasion measurement

NASA Astrophysics Data System (ADS)

Rössler, Tomáš; Hrabovský, Miroslav; Pluháček, František

2005-08-01

The cotyle implantate is abraded in the body of patient and its shape changes. Information about the magnitude of abrasion is contained in the result contour map of the implantate. The locations and dimensions of abraded areas can be computed from the contours deformation. The method called the single-projector moire topography was used for the contour lines determination. The theoretical description of method is given at first. The design of the experimental set-up follows. The light grating projector was developed to realize the periodic structure on the measured surface. The method of fringe-shifting was carried out to increase the data quantity. The description of digital processing applied to the moire grating images is introduced at the end together with the examples of processed images.

Image processing enhancement of high-resolution TEM micrographs of nanometer-size metal particles

NASA Technical Reports Server (NTRS)

Artal, P.; Avalos-Borja, M.; Soria, F.; Poppa, H.; Heinemann, K.

1989-01-01

The high-resolution TEM detectability of lattice fringes from metal particles supported on substrates is impeded by the substrate itself. Single value decomposition (SVD) and Fourier filtering (FFT) methods were applied to standard high resolution micrographs to enhance lattice resolution from particles as well as from crystalline substrates. SVD produced good results for one direction of fringes, and it can be implemented as a real-time process. Fourier methods are independent of azimuthal directions and allow separation of particle lattice planes from those pertaining to the substrate, which makes it feasible to detect possible substrate distortions produced by the supported particle. This method, on the other hand, is more elaborate, requires more computer time than SVD and is, therefore, less likely to be used in real-time image processing applications.

Localization of Interference Fringes.

ERIC Educational Resources Information Center

Simon, J. M.; Comastri, Silvia A.

1980-01-01

Discusses a proof for determining the localized fringes position arrived at when one considers the interference of two extended sources when one is able to observe fringes only at certain points in space. Shows how the localized fringes may be found in a device used to observe Newton's rings. (Author/CS)

18 CFR 1317.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 18 Conservation of Power and Water Resources 2 2011-04-01 2011-04-01 false Fringe benefits. 1317... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

24 CFR 3.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 24 Housing and Urban Development 1 2013-04-01 2013-04-01 false Fringe benefits. 3.525 Section 3... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

24 CFR 3.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 24 Housing and Urban Development 1 2014-04-01 2014-04-01 false Fringe benefits. 3.525 Section 3... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

45 CFR 2555.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 45 Public Welfare 4 2011-10-01 2011-10-01 false Fringe benefits. 2555.525 Section 2555.525 Public... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

13 CFR 113.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 13 Business Credit and Assistance 1 2013-01-01 2013-01-01 false Fringe benefits. 113.525 Section... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

34 CFR 106.56 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 34 Education 1 2014-07-01 2014-07-01 false Fringe benefits. 106.56 Section 106.56 Education... benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital, accident, life insurance or retirement benefit, service, policy or plan, any profit-sharing or...

24 CFR 3.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 24 Housing and Urban Development 1 2012-04-01 2012-04-01 false Fringe benefits. 3.525 Section 3... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

38 CFR 23.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2014-07-01 2014-07-01 false Fringe benefits. 23.525... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

13 CFR 113.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Fringe benefits. 113.525 Section... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

34 CFR 106.56 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 34 Education 1 2013-07-01 2013-07-01 false Fringe benefits. 106.56 Section 106.56 Education... benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital, accident, life insurance or retirement benefit, service, policy or plan, any profit-sharing or...

45 CFR 2555.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 45 Public Welfare 4 2012-10-01 2012-10-01 false Fringe benefits. 2555.525 Section 2555.525 Public... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

34 CFR 106.56 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 34 Education 1 2012-07-01 2012-07-01 false Fringe benefits. 106.56 Section 106.56 Education... benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital, accident, life insurance or retirement benefit, service, policy or plan, any profit-sharing or...

18 CFR 1317.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 18 Conservation of Power and Water Resources 2 2012-04-01 2012-04-01 false Fringe benefits. 1317... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

13 CFR 113.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Fringe benefits. 113.525 Section... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

18 CFR 1317.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 18 Conservation of Power and Water Resources 2 2013-04-01 2012-04-01 true Fringe benefits. 1317... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

18 CFR 1317.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 18 Conservation of Power and Water Resources 2 2014-04-01 2014-04-01 false Fringe benefits. 1317... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

24 CFR 3.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Fringe benefits. 3.525 Section 3... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

34 CFR 106.56 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 34 Education 1 2011-07-01 2011-07-01 false Fringe benefits. 106.56 Section 106.56 Education... benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital, accident, life insurance or retirement benefit, service, policy or plan, any profit-sharing or...

34 CFR 106.56 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 34 Education 1 2010-07-01 2010-07-01 false Fringe benefits. 106.56 Section 106.56 Education... benefits. (a) Fringe benefits defined. For purposes of this part, fringe benefits means: Any medical, hospital, accident, life insurance or retirement benefit, service, policy or plan, any profit-sharing or...

38 CFR 23.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2011-07-01 2011-07-01 false Fringe benefits. 23.525... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

45 CFR 2555.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 45 Public Welfare 4 2010-10-01 2010-10-01 false Fringe benefits. 2555.525 Section 2555.525 Public... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

45 CFR 2555.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 45 Public Welfare 4 2013-10-01 2013-10-01 false Fringe benefits. 2555.525 Section 2555.525 Public... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

24 CFR 3.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Fringe benefits. 3.525 Section 3... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

38 CFR 23.525 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2013-07-01 2013-07-01 false Fringe benefits. 23.525... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

18 CFR 1317.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 18 Conservation of Power and Water Resources 2 2010-04-01 2010-04-01 false Fringe benefits. 1317... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

13 CFR 113.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 13 Business Credit and Assistance 1 2014-01-01 2014-01-01 false Fringe benefits. 113.525 Section... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

38 CFR 23.525 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2012-07-01 2012-07-01 false Fringe benefits. 23.525... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

13 CFR 113.525 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Fringe benefits. 113.525 Section... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

38 CFR 23.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2010-07-01 2010-07-01 false Fringe benefits. 23.525... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

45 CFR 2555.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 45 Public Welfare 4 2014-10-01 2014-10-01 false Fringe benefits. 2555.525 Section 2555.525 Public... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

High-speed three-dimensional measurements with a fringe projection-based optical sensor

NASA Astrophysics Data System (ADS)

Bräuer-Burchardt, Christian; Breitbarth, Andreas; Kühmstedt, Peter; Notni, Gunther

2014-11-01

An optical three-dimensional (3-D) sensor based on a fringe projection technique that realizes the acquisition of the surface geometry of small objects was developed for highly resolved and ultrafast measurements. It realizes a data acquisition rate up to 60 high-resolution 3-D datasets per second. The high measurement velocity was achieved by consequent fringe code reduction and parallel data processing. The reduction of the length of the fringe image sequence was obtained by omission of the Gray code sequence using the geometric restrictions of the measurement objects and the geometric constraints of the sensor arrangement. The sensor covers three different measurement fields between 20 mm×20 mm and 40 mm×40 mm with a spatial resolution between 10 and 20 μm, respectively. In order to obtain a robust and fast recalibration of the sensor after change of the measurement field, a calibration procedure based on single shot analysis of a special test object was applied which works with low effort and time. The sensor may be used, e.g., for quality inspection of conductor boards or plugs in real-time industrial applications.

Micro/Nano-scale Strain Distribution Measurement from Sampling Moiré Fringes.

PubMed

Wang, Qinghua; Ri, Shien; Tsuda, Hiroshi

2017-05-23

This work describes the measurement procedure and principles of a sampling moiré technique for full-field micro/nano-scale deformation measurements. The developed technique can be performed in two ways: using the reconstructed multiplication moiré method or the spatial phase-shifting sampling moiré method. When the specimen grid pitch is around 2 pixels, 2-pixel sampling moiré fringes are generated to reconstruct a multiplication moiré pattern for a deformation measurement. Both the displacement and strain sensitivities are twice as high as in the traditional scanning moiré method in the same wide field of view. When the specimen grid pitch is around or greater than 3 pixels, multi-pixel sampling moiré fringes are generated, and a spatial phase-shifting technique is combined for a full-field deformation measurement. The strain measurement accuracy is significantly improved, and automatic batch measurement is easily achievable. Both methods can measure the two-dimensional (2D) strain distributions from a single-shot grid image without rotating the specimen or scanning lines, as in traditional moiré techniques. As examples, the 2D displacement and strain distributions, including the shear strains of two carbon fiber-reinforced plastic specimens, were measured in three-point bending tests. The proposed technique is expected to play an important role in the non-destructive quantitative evaluations of mechanical properties, crack occurrences, and residual stresses of a variety of materials.

Performance of Dispersed Fringe Sensor in the Presence of Segmented Mirror Aberrations: Modeling and Simulation

NASA Technical Reports Server (NTRS)

Shi, Fang; Basinger, Scott A.; Redding, David C.

2006-01-01

Dispersed Fringe Sensing (DFS) is an efficient and robust method for coarse phasing of a segmented primary mirror such as the James Webb Space Telescope (JWST). In this paper, modeling and simulations are used to study the effect of segmented mirror aberrations on the fringe image, DFS signals and DFS detection accuracy. The study has shown due to the pixilation spatial filter effect from DFS signal extraction the effect of wavefront error is reduced and DFS algorithm will be more robust against wavefront aberration by using multi-trace DFS approach. We also studied the JWST Dispersed Hartmann Sensor (DHS) performance in presence of wavefront aberrations caused by the gravity sag and we use the scaled gravity sag to explore the JWST DHS performance relationship with the level of the wavefront aberration. This also includes the effect from line-of-sight jitter.

Essential features of residual stress determination in thin-walled plane structures in a base of whole field interferometric measurements

NASA Astrophysics Data System (ADS)

Pisarev, Vladimir S.; Odintsev, I.; Balalov, V.; Apalkov, A.

2003-05-01

Sophisticated technique for reliable quantitative deriving residual stress values from initial experimental data, which are inherent in combined implementing the hole drilling method with both holographic and speckle interferometry, is described in detail. The approach developed includes both possible ways of obtaining initial experimental information. The first of them consists of recording a set of required interference fringe patterns, which are resulted from residual stress energy release after through hole drilling, in two orthogonal directions that coincide with principal strain directions. The second way is obtaining a series of interrelated fringe patterns when a direction of either observation in reflection hologram interferometry or dual-beam illumination in speckle interferometry lies arbitrary with respect to definite principal strain direction. A set of the most typical both actual and analogous reference fringe patterns, which are related to both reflection hologram and dual-beam speckle interferometry, are presented.

The role of photographic parameters in laser speckle or particle image displacement velocimetry

NASA Technical Reports Server (NTRS)

Lourenco, L.; Krothapalli, A.

1987-01-01

The parameters involved in obtaining the multiple exposure photographs in the laser speckle velocimetry method (to record the light scattering by the seeding particles) were optimized. The effects of the type, concentration, and dimensions of the tracer, the exposure conditions (time between exposures, exposure time, and number of exposures), and the sensitivity and resolution of the film on the quality of the final results were investigated, photographing an experimental flow behind an impulsively started circular cylinder. The velocity data were acquired by digital processing of Young's fringes, produced by point-by-point scanning of a photographic negative. Using the optimal photographing conditions, the errors involved in the estimation of the fringe angle and spacing were of the order of 1 percent for the spacing and +/1 deg for the fringe orientation. The resulting accuracy in the velocity was of the order of 2-3 percent of the maximum velocity in the field.

Wavefront division digital holography

NASA Astrophysics Data System (ADS)

Zhang, Wenhui; Cao, Liangcai; Li, Rujia; Zhang, Hua; Zhang, Hao; Jiang, Qiang; Jin, Guofan

2018-05-01

Digital holography (DH), mostly Mach-Zehnder configuration based, belongs to non-common path amplitude splitting interference imaging whose stability and fringe contrast are environmental sensitive. This paper presents a wavefront division DH configuration with both high stability and high-contrast fringes benefitting from quasi common path wavefront-splitting interference. In our proposal, two spherical waves with similar curvature coming from the same wavefront are used, which makes full use of the physical sampling capacity of the detectors. The interference fringe spacing can be adjusted flexibly for both in-line and off-axis mode due to the independent modulation to these two waves. Only a few optical elements, including the mirror-beam splitter interference component, are used without strict alignments, which makes it robust and easy-to-implement. The proposed wavefront division DH promotes interference imaging physics into the practical and miniaturized a step forward. The feasibility of this method is proved by the imaging of a resolution target and a water flea.

Fringing-field dielectrophoretic assembly of ultrahigh-density semiconducting nanotube arrays with a self-limited pitch

NASA Astrophysics Data System (ADS)

Cao, Qing; Han, Shu-Jen; Tulevski, George S.

2014-09-01

One key challenge of realizing practical high-performance electronic devices based on single-walled carbon nanotubes is to produce electronically pure nanotube arrays with both a minuscule and uniform inter-tube pitch for sufficient device-packing density and homogeneity. Here we develop a method in which the alternating voltage-fringing electric field formed between surface microelectrodes and the substrate is utilized to assemble semiconducting nanotubes into well-aligned, ultrahigh-density and submonolayered arrays, with a consistent pitch as small as 21±6 nm determined by a self-limiting mechanism, based on the unique field focusing and screening effects of the fringing field. Field-effect transistors based on such nanotube arrays exhibit record high device transconductance (>50 μS μm-1) and decent on current per nanotube (~1 μA per tube) together with high on/off ratios at a drain bias of -1 V.

A wavelet ridge extraction method employing a novel cost function in two-dimensional wavelet transform profilometry

NASA Astrophysics Data System (ADS)

Wang, Jianhua; Yang, Yanxi

2018-05-01

We present a new wavelet ridge extraction method employing a novel cost function in two-dimensional wavelet transform profilometry (2-D WTP). First of all, the maximum value point is extracted from two-dimensional wavelet transform coefficient modulus, and the local extreme value points over 90% of maximum value are also obtained, they both constitute wavelet ridge candidates. Then, the gradient of rotate factor is introduced into the Abid's cost function, and the logarithmic Logistic model is used to adjust and improve the cost function weights so as to obtain more reasonable value estimation. At last, the dynamic programming method is used to accurately find the optimal wavelet ridge, and the wrapped phase can be obtained by extracting the phase at the ridge. Its advantage is that, the fringe pattern with low signal-to-noise ratio can be demodulated accurately, and its noise immunity will be better. Meanwhile, only one fringe pattern is needed to projected to measured object, so dynamic three-dimensional (3-D) measurement in harsh environment can be realized. Computer simulation and experimental results show that, for the fringe pattern with noise pollution, the 3-D surface recovery accuracy by the proposed algorithm is increased. In addition, the demodulation phase accuracy of Morlet, Fan and Cauchy mother wavelets are compared.

Sparse recovery of undersampled intensity patterns for coherent diffraction imaging at high X-ray energies

DOE PAGES

Maddali, S.; Calvo-Almazan, I.; Almer, J.; ...

2018-03-21

Coherent X-ray photons with energies higher than 50 keV offer new possibilities for imaging nanoscale lattice distortions in bulk crystalline materials using Bragg peak phase retrieval methods. However, the compression of reciprocal space at high energies typically results in poorly resolved fringes on an area detector, rendering the diffraction data unsuitable for the three-dimensional reconstruction of compact crystals. To address this problem, we propose a method by which to recover fine fringe detail in the scattered intensity. This recovery is achieved in two steps: multiple undersampled measurements are made by in-plane sub-pixel motion of the area detector, then this datamore » set is passed to a sparsity-based numerical solver that recovers fringe detail suitable for standard Bragg coherent diffraction imaging (BCDI) reconstruction methods of compact single crystals. The key insight of this paper is that sparsity in a BCDI data set can be enforced by recognising that the signal in the detector, though poorly resolved, is band-limited. This requires fewer in-plane detector translations for complete signal recovery, while adhering to information theory limits. Lastly, we use simulated BCDI data sets to demonstrate the approach, outline our sparse recovery strategy, and comment on future opportunities.« less

Sparse recovery of undersampled intensity patterns for coherent diffraction imaging at high X-ray energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maddali, S.; Calvo-Almazan, I.; Almer, J.

Coherent X-ray photons with energies higher than 50 keV offer new possibilities for imaging nanoscale lattice distortions in bulk crystalline materials using Bragg peak phase retrieval methods. However, the compression of reciprocal space at high energies typically results in poorly resolved fringes on an area detector, rendering the diffraction data unsuitable for the three-dimensional reconstruction of compact crystals. To address this problem, we propose a method by which to recover fine fringe detail in the scattered intensity. This recovery is achieved in two steps: multiple undersampled measurements are made by in-plane sub-pixel motion of the area detector, then this datamore » set is passed to a sparsity-based numerical solver that recovers fringe detail suitable for standard Bragg coherent diffraction imaging (BCDI) reconstruction methods of compact single crystals. The key insight of this paper is that sparsity in a BCDI data set can be enforced by recognising that the signal in the detector, though poorly resolved, is band-limited. This requires fewer in-plane detector translations for complete signal recovery, while adhering to information theory limits. Lastly, we use simulated BCDI data sets to demonstrate the approach, outline our sparse recovery strategy, and comment on future opportunities.« less

Sparse recovery of undersampled intensity patterns for coherent diffraction imaging at high X-ray energies.

PubMed

Maddali, S; Calvo-Almazan, I; Almer, J; Kenesei, P; Park, J-S; Harder, R; Nashed, Y; Hruszkewycz, S O

2018-03-21

Coherent X-ray photons with energies higher than 50 keV offer new possibilities for imaging nanoscale lattice distortions in bulk crystalline materials using Bragg peak phase retrieval methods. However, the compression of reciprocal space at high energies typically results in poorly resolved fringes on an area detector, rendering the diffraction data unsuitable for the three-dimensional reconstruction of compact crystals. To address this problem, we propose a method by which to recover fine fringe detail in the scattered intensity. This recovery is achieved in two steps: multiple undersampled measurements are made by in-plane sub-pixel motion of the area detector, then this data set is passed to a sparsity-based numerical solver that recovers fringe detail suitable for standard Bragg coherent diffraction imaging (BCDI) reconstruction methods of compact single crystals. The key insight of this paper is that sparsity in a BCDI data set can be enforced by recognising that the signal in the detector, though poorly resolved, is band-limited. This requires fewer in-plane detector translations for complete signal recovery, while adhering to information theory limits. We use simulated BCDI data sets to demonstrate the approach, outline our sparse recovery strategy, and comment on future opportunities.

7 CFR 15a.56 - Fringe benefits.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 1 2011-01-01 2011-01-01 false Fringe benefits. 15a.56 Section 15a.56 Agriculture Office of the Secretary of Agriculture EDUCATION PROGRAMS OR ACTIVITIES RECEIVING OR BENEFITTING FROM... Activities Prohibited § 15a.56 Fringe benefits. (a) “Fringe benefits” defined. For purposes of this part...

7 CFR 15a.56 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 1 2014-01-01 2014-01-01 false Fringe benefits. 15a.56 Section 15a.56 Agriculture Office of the Secretary of Agriculture EDUCATION PROGRAMS OR ACTIVITIES RECEIVING OR BENEFITTING FROM... Activities Prohibited § 15a.56 Fringe benefits. (a) “Fringe benefits” defined. For purposes of this part...

14 CFR § 1253.525 - Fringe benefits.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 5 2014-01-01 2014-01-01 false Fringe benefits. § 1253.525 Section Â... benefits. (a) “Fringe benefits” defined. For purposes of these Title IX regulations, fringe benefits means: Any medical, hospital, accident, life insurance, or retirement benefit, service, policy or plan, any...

7 CFR 15a.56 - Fringe benefits.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 1 2013-01-01 2013-01-01 false Fringe benefits. 15a.56 Section 15a.56 Agriculture Office of the Secretary of Agriculture EDUCATION PROGRAMS OR ACTIVITIES RECEIVING OR BENEFITTING FROM... Activities Prohibited § 15a.56 Fringe benefits. (a) “Fringe benefits” defined. For purposes of this part...

7 CFR 15a.56 - Fringe benefits.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 1 2012-01-01 2012-01-01 false Fringe benefits. 15a.56 Section 15a.56 Agriculture Office of the Secretary of Agriculture EDUCATION PROGRAMS OR ACTIVITIES RECEIVING OR BENEFITTING FROM... Activities Prohibited § 15a.56 Fringe benefits. (a) “Fringe benefits” defined. For purposes of this part...

77 FR 50211 - Proposed Collection; Comment Request for Regulation Project

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-20

... taxation of fringe benefits and exclusions from gross income for certain fringe Benefits, listed property...-63-88 (Final and temporary regulations) Taxation of Fringe Benefits and Exclusions From Gross Income... Code section 274(d). The regulation also provides guidance on the taxation of fringe benefits and...

44 CFR 208.40 - Reimbursement of fringe benefit costs during Activation.

Code of Federal Regulations, 2010 CFR

2010-10-01

... reimbursement sought from DHS. (c) DHS will not reimburse the Sponsoring Agency for fringe benefit costs for... 44 Emergency Management and Assistance 1 2010-10-01 2010-10-01 false Reimbursement of fringe... RESCUE RESPONSE SYSTEM Response Cooperative Agreements § 208.40 Reimbursement of fringe benefit costs...

Recording multiple spatially-heterodyned direct to digital holograms in one digital image

DOEpatents

Hanson, Gregory R [Clinton, TN; Bingham, Philip R [Knoxville, TN

2008-03-25

Systems and methods are described for recording multiple spatially-heterodyned direct to digital holograms in one digital image. A method includes digitally recording, at a first reference beam-object beam angle, a first spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded first spatially-heterodyned hologram by shifting a first original origin of the recorded first spatially-heterodyned hologram to sit on top of a first spatial-heterodyne carrier frequency defined by the first reference beam-object beam angle; digitally recording, at a second reference beam-object beam angle, a second spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis; Fourier analyzing the recorded second spatially-heterodyned hologram by shifting a second original origin of the recorded second spatially-heterodyned hologram to sit on top of a second spatial-heterodyne carrier frequency defined by the second reference beam-object beam angle; applying a first digital filter to cut off signals around the first original origin and define a first result; performing a first inverse Fourier transform on the first result; applying a second digital filter to cut off signals around the second original origin and define a second result; and performing a second inverse Fourier transform on the second result, wherein the first reference beam-object beam angle is not equal to the second reference beam-object beam angle and a single digital image includes both the first spatially-heterodyned hologram and the second spatially-heterodyned hologram.

Multiple rotation assessment through isothetic fringes in speckle photography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Angel, Luciano; Tebaldi, Myrian; Bolognini, Nestor

2007-05-10

The use of different pupils for storing each speckled image in speckle photography is employed to determine multiple in-plane rotations. The method consists of recording a four-exposure specklegram where the rotations are done between exposures. This specklegram is then optically processed in a whole field approach rendering isothetic fringes, which give detailed information about the multiple rotations. It is experimentally demonstrated that the proposed arrangement permits the depiction of six isothetics in order to measure either six different angles or three nonparallel components for two local general in-plane displacements.

Optics in engineering measurement; Proceedings of the Meeting, Cannes, France, December 3-6, 1985

NASA Technical Reports Server (NTRS)

Fagan, William F. (Editor)

1986-01-01

The present conference on optical measurement systems considers topics in the fields of holographic interferometry, speckle techniques, moire fringe and grating methods, optical surface gaging, laser- and fiber-optics-based measurement systems, and optics for engineering data evaluation. Specific attention is given to holographic NDE for aerospace composites, holographic interferometry of rotating components, new developments in computer-aided holography, electronic speckle pattern interferometry, mass transfer measurements using projected fringes, nuclear reactor photogrammetric inspection, a laser Doppler vibrometer, and optoelectronic measurements of the yaw angle of projectiles.

Imaging the Localized Plasmon Resonance Modes in Graphene Nanoribbons

DOE PAGES

Hu, F.; Luan, Y.; Fei, Z.; ...

2017-08-14

Here, we report a nanoinfrared (IR) imaging study of the localized plasmon resonance modes of graphene nanoribbons (GNRs) using a scattering-type scanning near-field optical microscope (s-SNOM). By comparing the imaging data of GNRs that are aligned parallel and perpendicular to the in-plane component of the excitation laser field, we observed symmetric and asymmetric plasmonic interference fringes, respectively. Theoretical analysis indicates that the asymmetric fringes are formed due to the interplay between the localized surface plasmon resonance (SPR) mode excited by the GNRs and the propagative surface plasmon polariton (SPP) mode launched by the s-SNOM tip. And with rigorous simulations, wemore » reproduce the observed fringe patterns and address quantitatively the role of the s-SNOM tip on both the SPR and SPP modes. Moreover, we have seen real-space signatures of both the dipole and higher-order SPR modes by varying the ribbon width.« less

Optically phase-locked electronic speckle pattern interferometer system performance for vibration measurement in random displacement fields

NASA Astrophysics Data System (ADS)

Moran, Steve E.; Lugannani, Robert; Craig, Peter N.; Law, Robert L.

1989-02-01

An analysis is made of the performance of an optically phase-locked electronic speckle pattern interferometer in the presence of random noise displacements. Expressions for the phase-locked speckle contrast for single-frame imagery and the composite rms exposure for two sequentially subtracted frames are obtained in terms of the phase-locked composite and single-frame fringe functions. The noise fringe functions are evaluated for stationary, coherence-separable noise displacements obeying Gauss-Markov temporal statistics. The theoretical findings presented here are qualitatively supported by experimental results.

Computerized lateral-shear interferometer

NASA Astrophysics Data System (ADS)

Hasegan, Sorin A.; Jianu, Angela; Vlad, Valentin I.

1998-07-01

A lateral-shear interferometer, coupled with a computer for laser wavefront analysis, is described. A CCD camera is used to transfer the fringe images through a frame-grabber into a PC. 3D phase maps are obtained by fringe pattern processing using a new algorithm for direct spatial reconstruction of the optical phase. The program describes phase maps by Zernike polynomials yielding an analytical description of the wavefront aberration. A compact lateral-shear interferometer has been built using a laser diode as light source, a CCD camera and a rechargeable battery supply, which allows measurements in-situ, if necessary.

20 CFR 641.565 - What policies govern the provision of wages and fringe benefits to participants?

Code of Federal Regulations, 2010 CFR

2010-04-01

... covered employment. (2) Allowable fringe benefit costs. Grantees may provide the following fringe benefits... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false What policies govern the provision of wages and fringe benefits to participants? 641.565 Section 641.565 Employees' Benefits EMPLOYMENT AND...

15 CFR 8a.525 - Fringe benefits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Fringe benefits. 8a.525 Section 8a.525 Commerce and Foreign Trade Office of the Secretary of Commerce NONDISCRIMINATION ON THE BASIS OF SEX IN... in Employment in Education Programs or Activities Prohibited § 8a.525 Fringe benefits. (a) “Fringe...

26 CFR 1.132-9 - Qualified transportation fringes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 26 Internal Revenue 2 2012-04-01 2012-04-01 false Qualified transportation fringes. 1.132-9... Qualified transportation fringes. (a) Table of contents. This section contains a list of the questions and answers in § 1.132-9. (1) General rules. Q-1. What is a qualified transportation fringe? Q-2. What is...

26 CFR 1.132-9 - Qualified transportation fringes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 26 Internal Revenue 2 2014-04-01 2014-04-01 false Qualified transportation fringes. 1.132-9... Qualified transportation fringes. (a) Table of contents. This section contains a list of the questions and answers in § 1.132-9. (1) General rules. Q-1. What is a qualified transportation fringe? Q-2. What is...

26 CFR 1.132-9 - Qualified transportation fringes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 2 2013-04-01 2013-04-01 false Qualified transportation fringes. 1.132-9... Qualified transportation fringes. (a) Table of contents. This section contains a list of the questions and answers in § 1.132-9. (1) General rules. Q-1. What is a qualified transportation fringe? Q-2. What is...

Digital algorithms for parallel pipelined single-detector homodyne fringe counting in laser interferometry

NASA Astrophysics Data System (ADS)

Rerucha, Simon; Sarbort, Martin; Hola, Miroslava; Cizek, Martin; Hucl, Vaclav; Cip, Ondrej; Lazar, Josef

2016-12-01

The homodyne detection with only a single detector represents a promising approach in the interferometric application which enables a significant reduction of the optical system complexity while preserving the fundamental resolution and dynamic range of the single frequency laser interferometers. We present the design, implementation and analysis of algorithmic methods for computational processing of the single-detector interference signal based on parallel pipelined processing suitable for real time implementation on a programmable hardware platform (e.g. the FPGA - Field Programmable Gate Arrays or the SoC - System on Chip). The algorithmic methods incorporate (a) the single detector signal (sine) scaling, filtering, demodulations and mixing necessary for the second (cosine) quadrature signal reconstruction followed by a conic section projection in Cartesian plane as well as (a) the phase unwrapping together with the goniometric and linear transformations needed for the scale linearization and periodic error correction. The digital computing scheme was designed for bandwidths up to tens of megahertz which would allow to measure the displacements at the velocities around half metre per second. The algorithmic methods were tested in real-time operation with a PC-based reference implementation that employed the advantage pipelined processing by balancing the computational load among multiple processor cores. The results indicate that the algorithmic methods are suitable for a wide range of applications [3] and that they are bringing the fringe counting interferometry closer to the industrial applications due to their optical setup simplicity and robustness, computational stability, scalability and also a cost-effectiveness.

DLP-based 3D metrology by structured light or projected fringe technology for life sciences and industrial metrology

NASA Astrophysics Data System (ADS)

Frankowski, G.; Hainich, R.

2009-02-01

Since the mid-eighties, a fundamental idea for achieving measuring accuracy in projected fringe technology was to consider the projected fringe pattern as an interferogram and evaluate it on the basis of advanced algorithms widely used for phase measuring in real-time interferometry. A fundamental requirement for obtaining a sufficiently high degree of measuring accuracy with this so-called "phase measuring projected fringe technology" is that the projected fringes, analogous to interference fringes, must have a cos2-shaped intensity distribution. Until the mid-nineties, this requirement for the projected fringe pattern measurement technology presented a basic handicap for its wide application in 3D metrology. This situation changed abruptly, when in the nineties Texas Instruments introduced to the market advanced digital light projection on the basis of micro mirror based projection systems, socalled DLP technology, which also facilitated the generation and projection of cos2-shaped intensity and/or fringe patterns. With this DLP technology, which from its original approach was actually oriented towards completely different applications such as multimedia projection, Texas Instruments boosted phase-measuring fringe projection in optical 3D metrology to a worldwide breakthrough both for medical as well as industrial applications. A subject matter of the lecture will be to present the fundamental principles and the resulting advantages of optical 3D metrology based on phase-measuring fringe projection using DLP technology. Further will be presented and discussed applications of the measurement technology in medical engineering and industrial metrology.

A comparison of electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry for flow measurements

NASA Technical Reports Server (NTRS)

Decker, A. J.; Stricker, J.

1985-01-01

Electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry are compared as methods for the accurate measurement of refractive index and density change distributions of phase objects. Experimental results are presented to show that the two methods have comparable accuracy for measuring the first derivative of the interferometric fringe shift. The phase object for the measurements is a large crystal of KD*P, whose refractive index distribution can be changed accurately and repeatably for the comparison. Although the refractive index change causes only about one interferometric fringe shift over the entire crystal, the derivative shows considerable detail for the comparison. As electronic phase measurement methods, both methods are very accurate and are intrinsically compatible with computer controlled readout and data processing. Heterodyne moire is relatively inexpensive and has high variable sensitivity. Heterodyne holographic interferometry is better developed, and can be used with poor quality optical access to the experiment.

Fringe chasing by three-point spatial phase shifting for discrimination of the motion direction in the long-range homodyne laser Doppler vibrometry

NASA Astrophysics Data System (ADS)

Daemi, Mohammad Hossein; Rasouli, Saifollah

2018-07-01

In this work, a three-point spatial phase shifting (SPS) method is implemented for chasing of the moving interference fringes in the homodyne laser Doppler vibrometry (HoLDV). By the use of SPS method, we remove disability of the HoLDV in the discrimination of the motion direction for long-range displacements. From the phase increments histogram, phase unwrapping tolerance value is selected, and adequacy of the data acquisition rate and required bandwidth limit are determined. Also in this paper, a detailed investigation on the effect of detectors positioning errors and influence of the Gaussian profile of the interfering beams on the measurements are presented. Performance of the method is verified by measuring a given harmonic vibration produced by a loudspeaker. Also, by the proposed method, vibration of mounting system of a disk laser gain medium is characterized.

Deformation measurements of composite multi-span beam shear specimens by Moire interferometry

NASA Technical Reports Server (NTRS)

Post, D.; Czarnek, R.; Joh, D.; Wood, J.

1984-01-01

Experimental analyses were performed for determination of in plane deformations and shear strains in unidirectional and quasi-isotropic graphite-epoxy beams. Forty-eight ply beams were subjected to 5 point and 3 point flexure. Whole field measurements were recorded at load levels from about 20% to more than 90% of failure loads. Contour maps of U and W displacement fields were obtained by moire interferometry, using reference gratings of 2400 lines/mm. Clearly defined fringes with fringe orders exceeding 1000 were obtained. Whole field contour maps of shear strains were obtained by a method developed for these tests. Various anomalous effects were detected in the displacement fields. Their analysis indicated excess shear strains in resin rich zones in regions of shear tractions; free edge shear strains in quasi-isotropic specimens in regions of normal stresses; and shear stresses associated with cyclic shear compliances of quasi-isotropic plies in regions of shear tractions. Their contributions could occur independently or in superposition. Qualitative analyses addressed questions of relaxation; influence of contact stress distribution; specimen failure; effect of specimen overhang; nonlinearity; and qualities of 5 and 3 point flexure tests.

Phase unwrapping algorithm using polynomial phase approximation and linear Kalman filter.

PubMed

Kulkarni, Rishikesh; Rastogi, Pramod

2018-02-01

A noise-robust phase unwrapping algorithm is proposed based on state space analysis and polynomial phase approximation using wrapped phase measurement. The true phase is approximated as a two-dimensional first order polynomial function within a small sized window around each pixel. The estimates of polynomial coefficients provide the measurement of phase and local fringe frequencies. A state space representation of spatial phase evolution and the wrapped phase measurement is considered with the state vector consisting of polynomial coefficients as its elements. Instead of using the traditional nonlinear Kalman filter for the purpose of state estimation, we propose to use the linear Kalman filter operating directly with the wrapped phase measurement. The adaptive window width is selected at each pixel based on the local fringe density to strike a balance between the computation time and the noise robustness. In order to retrieve the unwrapped phase, either a line-scanning approach or a quality guided strategy of pixel selection is used depending on the underlying continuous or discontinuous phase distribution, respectively. Simulation and experimental results are provided to demonstrate the applicability of the proposed method.

Detailed analysis of an optimized FPP-based 3D imaging system

NASA Astrophysics Data System (ADS)

Tran, Dat; Thai, Anh; Duong, Kiet; Nguyen, Thanh; Nehmetallah, Georges

2016-05-01

In this paper, we present detail analysis and a step-by-step implementation of an optimized fringe projection profilometry (FPP) based 3D shape measurement system. First, we propose a multi-frequency and multi-phase shifting sinusoidal fringe pattern reconstruction approach to increase accuracy and sensitivity of the system. Second, phase error compensation caused by the nonlinear transfer function of the projector and camera is performed through polynomial approximation. Third, phase unwrapping is performed using spatial and temporal techniques and the tradeoff between processing speed and high accuracy is discussed in details. Fourth, generalized camera and system calibration are developed for phase to real world coordinate transformation. The calibration coefficients are estimated accurately using a reference plane and several gauge blocks with precisely known heights and by employing a nonlinear least square fitting method. Fifth, a texture will be attached to the height profile by registering a 2D real photo to the 3D height map. The last step is to perform 3D image fusion and registration using an iterative closest point (ICP) algorithm for a full field of view reconstruction. The system is experimentally constructed using compact, portable, and low cost off-the-shelf components. A MATLAB® based GUI is developed to control and synchronize the whole system.

Interferometric Near-Infrared Spectroscopy (iNIRS) for determination of optical and dynamical properties of turbid media

PubMed Central

Borycki, Dawid; Kholiqov, Oybek; Chong, Shau Poh; Srinivasan, Vivek J.

2016-01-01

We introduce and implement interferometric near-infrared spectroscopy (iNIRS), which simultaneously extracts optical and dynamical properties of turbid media through analysis of a spectral interference fringe pattern. The spectral interference fringe pattern is measured using a Mach-Zehnder interferometer with a frequency-swept narrow linewidth laser. Fourier analysis of the detected signal is used to determine time-of-flight (TOF)-resolved intensity, which is then analyzed over time to yield TOF-resolved intensity autocorrelations. This approach enables quantification of optical properties, which is not possible in conventional, continuous-wave near-infrared spectroscopy (NIRS). Furthermore, iNIRS quantifies scatterer motion based on TOF-resolved autocorrelations, which is a feature inaccessible by well-established diffuse correlation spectroscopy (DCS) techniques. We prove this by determining TOF-resolved intensity and temporal autocorrelations for light transmitted through diffusive fluid phantoms with optical thicknesses of up to 55 reduced mean free paths (approximately 120 scattering events). The TOF-resolved intensity is used to determine optical properties with time-resolved diffusion theory, while the TOF-resolved intensity autocorrelations are used to determine dynamics with diffusing wave spectroscopy. iNIRS advances the capabilities of diffuse optical methods and is suitable for in vivo tissue characterization. Moreover, iNIRS combines NIRS and DCS capabilities into a single modality. PMID:26832264

Comparative analysis of stress in a new proposal of dental implants.

PubMed

Valente, Mariana Lima da Costa; de Castro, Denise Tornavoi; Macedo, Ana Paula; Shimano, Antonio Carlos; Dos Reis, Andréa Cândido

2017-08-01

The purpose of this study was to compare, through photoelastic analysis, the stress distribution around conventional and modified external hexagon (EH) and morse taper (MT) dental implant connections. Four photoelastic models were prepared (n=1): Model 1 - conventional EH cylindrical implant (Ø 4.0mm×11mm - Neodent®), Model 2 - modified EH cylindrical implant, Model 3 - conventional MT Conical implant (Ø 4.3mm×10mm - Neodent®) and Model 4 - modified MT conical implant. 100 and 150N axial and oblique loads (30° tilt) were applied in the devices coupled to the implants. A plane transmission polariscope was used in the analysis of fringes and each position of interest was recorded by a digital camera. The Tardy method was used to quantify the fringe order (n), that calculates the maximum shear stress (τ) value in each selected point. The results showed lower stress concentration in the modified cylindrical implant (EH) compared to the conventional model, with application of 150N axial and 100N oblique loads. Lower stress was observed for the modified conical (MT) implant with the application of 100 and 150N oblique loads, which was not observed for the conventional implant model. The comparative analysis of the models showed that the new design proposal generates good stress distribution, especially in the cervical third, suggesting the preservation of bone tissue in the bone crest region. Copyright © 2017 Elsevier B.V. All rights reserved.

Measurement of instantaneous rotational speed using double-sine-varying-density fringe pattern

NASA Astrophysics Data System (ADS)

Zhong, Jianfeng; Zhong, Shuncong; Zhang, Qiukun; Peng, Zhike

2018-03-01

Fast and accurate rotational speed measurement is required both for condition monitoring and faults diagnose of rotating machineries. A vision- and fringe pattern-based rotational speed measurement system was proposed to measure the instantaneous rotational speed (IRS) with high accuracy and reliability. A special double-sine-varying-density fringe pattern (DSVD-FP) was designed and pasted around the shaft surface completely and worked as primary angular sensor. The rotational angle could be correctly obtained from the left and right fringe period densities (FPDs) of the DSVD-FP image sequence recorded by a high-speed camera. The instantaneous angular speed (IAS) between two adjacent frames could be calculated from the real-time rotational angle curves, thus, the IRS also could be obtained accurately and efficiently. Both the measurement principle and system design of the novel method have been presented. The influence factors on the sensing characteristics and measurement accuracy of the novel system, including the spectral centrobaric correction method (SCCM) on the FPD calculation, the noise sources introduce by the image sensor, the exposure time and the vibration of the shaft, were investigated through simulations and experiments. The sampling rate of the high speed camera could be up to 5000 Hz, thus, the measurement becomes very fast and the change in rotational speed was sensed within 0.2 ms. The experimental results for different IRS measurements and characterization of the response property of a servo motor demonstrated the high accuracy and fast measurement of the proposed technique, making it attractive for condition monitoring and faults diagnosis of rotating machineries.

24 CFR 3280.504 - Condensation control and installation of vapor retarders.

Code of Federal Regulations, 2011 CFR

2011-04-01

... these cavities; or (4) Homes manufactured to be sited in “humid climates” or “fringe climates” as shown on the Humid and Fringe Climate Map in this paragraph are permitted to have a vapor retarder... the humid and fringe climate areas shown on the Humid and Fringe Climate Map in paragraph (b)(4) of...

24 CFR 3280.504 - Condensation control and installation of vapor retarders.

Code of Federal Regulations, 2013 CFR

2013-04-01

... these cavities; or (4) Homes manufactured to be sited in “humid climates” or “fringe climates” as shown on the Humid and Fringe Climate Map in this paragraph are permitted to have a vapor retarder... the humid and fringe climate areas shown on the Humid and Fringe Climate Map in paragraph (b)(4) of...

24 CFR 3280.504 - Condensation control and installation of vapor retarders.

Code of Federal Regulations, 2014 CFR

2014-04-01

... be sited in “humid climates” or “fringe climates” as shown on the Humid and Fringe Climate Map in... specified), listed by state are deemed to be within the humid and fringe climate areas shown on the Humid and Fringe Climate Map in paragraph (b)(4) of this section, and the vapor retarder or construction...

24 CFR 3280.504 - Condensation control and installation of vapor retarders.

Code of Federal Regulations, 2012 CFR

2012-04-01

... these cavities; or (4) Homes manufactured to be sited in “humid climates” or “fringe climates” as shown on the Humid and Fringe Climate Map in this paragraph are permitted to have a vapor retarder... the humid and fringe climate areas shown on the Humid and Fringe Climate Map in paragraph (b)(4) of...

24 CFR 3280.504 - Condensation control and installation of vapor retarders.

Code of Federal Regulations, 2010 CFR

2010-04-01

... these cavities; or (4) Homes manufactured to be sited in “humid climates” or “fringe climates” as shown on the Humid and Fringe Climate Map in this paragraph are permitted to have a vapor retarder... the humid and fringe climate areas shown on the Humid and Fringe Climate Map in paragraph (b)(4) of...

29 CFR 4.50 - Types of wage and fringe benefit determinations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 1 2010-07-01 2010-07-01 true Types of wage and fringe benefit determinations. 4.50... Determination Procedures § 4.50 Types of wage and fringe benefit determinations. The Administrator specifies the minimum monetary wages and fringe benefits to be paid as required under the Act in two types of...

Fringe Benefits and the Value of Summer Leisure for Public School Teachers in the Southeast.

ERIC Educational Resources Information Center

Mabry, Rodney H.; And Others

This report focuses on the fringe benefit element of total compensation for teachers in the Southeast. Study objectives include the following: (1) identifying teachers' fringe benefits in 12 Southeastern States; (2) examining the variation in fringe benefits within the region; (3) examining whether summer free time is a benefit or detriment; and…

26 CFR 1.132-6 - De minimis fringes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 26 Internal Revenue 2 2014-04-01 2014-04-01 false De minimis fringes. 1.132-6 Section 1.132-6...) INCOME TAXES (CONTINUED) Items Specifically Excluded from Gross Income § 1.132-6 De minimis fringes. (a... the Internal Revenue Code of 1986 other than section 132(a)(4), the value of any fringe benefit that...

26 CFR 1.132-6 - De minimis fringes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 26 Internal Revenue 2 2012-04-01 2012-04-01 false De minimis fringes. 1.132-6 Section 1.132-6...) INCOME TAXES (CONTINUED) Items Specifically Excluded from Gross Income § 1.132-6 De minimis fringes. (a... the Internal Revenue Code of 1986 other than section 132(a)(4), the value of any fringe benefit that...

26 CFR 1.132-6 - De minimis fringes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 2 2013-04-01 2013-04-01 false De minimis fringes. 1.132-6 Section 1.132-6...) INCOME TAXES (CONTINUED) Items Specifically Excluded from Gross Income § 1.132-6 De minimis fringes. (a... the Internal Revenue Code of 1986 other than section 132(a)(4), the value of any fringe benefit that...

14 CFR 93.345 - VFR outbound procedures for fringe airports.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 2 2012-01-01 2012-01-01 false VFR outbound procedures for fringe airports... Metropolitan Area Special Flight Rules Area § 93.345 VFR outbound procedures for fringe airports. (a) A pilot may depart from a fringe airport as defined in § 93.335 without filing a flight plan or communicating...

14 CFR 93.345 - VFR outbound procedures for fringe airports.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false VFR outbound procedures for fringe airports... Metropolitan Area Special Flight Rules Area § 93.345 VFR outbound procedures for fringe airports. (a) A pilot may depart from a fringe airport as defined in § 93.335 without filing a flight plan or communicating...

14 CFR 93.345 - VFR outbound procedures for fringe airports.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false VFR outbound procedures for fringe airports... Metropolitan Area Special Flight Rules Area § 93.345 VFR outbound procedures for fringe airports. (a) A pilot may depart from a fringe airport as defined in § 93.335 without filing a flight plan or communicating...

14 CFR 93.345 - VFR outbound procedures for fringe airports.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 2 2014-01-01 2014-01-01 false VFR outbound procedures for fringe airports... Metropolitan Area Special Flight Rules Area § 93.345 VFR outbound procedures for fringe airports. (a) A pilot may depart from a fringe airport as defined in § 93.335 without filing a flight plan or communicating...

14 CFR 93.345 - VFR outbound procedures for fringe airports.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 2 2013-01-01 2013-01-01 false VFR outbound procedures for fringe airports... Metropolitan Area Special Flight Rules Area § 93.345 VFR outbound procedures for fringe airports. (a) A pilot may depart from a fringe airport as defined in § 93.335 without filing a flight plan or communicating...

Fringe stabilizers and their application to telecommunication device manufacturing

NASA Astrophysics Data System (ADS)

Odhner, Jefferson E.

2000-10-01

The ability to create stable holographic grating is an important part of the production of many telecommunication products. The stability problem is increased by the need to use ultra-violet light for close fringe spacing and long exposure times on phot-resist - a relatively low sensitivity material. Active fringe locking increases the modulation depth and efficiency of these holographic gratings. A discussion of how fringe lockers work and how they can be incorporated into a manufacturing set-up is followed by results of using fringe lockers in the manufacturing of some telecommunication devices.

Dynamic tracking down-conversion signal processing method based on reference signal for grating heterodyne interferometer

NASA Astrophysics Data System (ADS)

Wang, Guochao; Yan, Shuhua; Zhou, Weihong; Gu, Chenhui

2012-08-01

Traditional displacement measurement systems by grating, which purely make use of fringe intensity to implement fringe count and subdivision, have rigid demands for signal quality and measurement condition, so they are not easy to realize measurement with nanometer precision. Displacement measurement with the dual-wavelength and single-grating design takes advantage of the single grating diffraction theory and the heterodyne interference theory, solving quite well the contradiction between large range and high precision in grating displacement measurement. To obtain nanometer resolution and nanometer precision, high-power subdivision of interference fringes must be realized accurately. A dynamic tracking down-conversion signal processing method based on the reference signal is proposed. Accordingly, a digital phase measurement module to realize high-power subdivision on field programmable gate array (FPGA) was designed, as well as a dynamic tracking down-conversion module using phase-locked loop (PLL). Experiments validated that a carrier signal after down-conversion can constantly maintain close to 100 kHz, and the phase-measurement resolution and phase precision are more than 0.05 and 0.2 deg, respectively. The displacement resolution and the displacement precision, corresponding to the phase results, are 0.139 and 0.556 nm, respectively.

In vivo visualization method by absolute blood flow velocity based on speckle and fringe pattern using two-beam multipoint laser Doppler velocimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyoden, Tomoaki, E-mail: kyouden@nc-toyama.ac.jp; Naruki, Shoji; Akiguchi, Shunsuke

Two-beam multipoint laser Doppler velocimetry (two-beam MLDV) is a non-invasive imaging technique able to provide an image of two-dimensional blood flow and has potential for observing cancer as previously demonstrated in a mouse model. In two-beam MLDV, the blood flow velocity can be estimated from red blood cells passing through a fringe pattern generated in the skin. The fringe pattern is created at the intersection of two beams in conventional LDV and two-beam MLDV. Being able to choose the depth position is an advantage of two-beam MLDV, and the position of a blood vessel can be identified in a three-dimensionalmore » space using this technique. Initially, we observed the fringe pattern in the skin, and the undeveloped or developed speckle pattern generated in a deeper position of the skin. The validity of the absolute velocity value detected by two-beam MLDV was verified while changing the number of layers of skin around a transparent flow channel. The absolute velocity value independent of direction was detected using the developed speckle pattern, which is created by the skin construct and two beams in the flow channel. Finally, we showed the relationship between the signal intensity and the fringe pattern, undeveloped speckle, or developed speckle pattern based on the skin depth. The Doppler signals were not detected at deeper positions in the skin, which qualitatively indicates the depth limit for two-beam MLDV.« less

Hydrodynamics of a bathymetrically complex fringing coral reef embayment: Wave climate, in situ observations, and wave prediction

USGS Publications Warehouse

Hoeke, R.; Storlazzi, C.; Ridd, P.

2011-01-01

This paper examines the relationship between offshore wave climate and nearshore waves and currents at Hanalei Bay, Hawaii, an exposed bay fringed with coral reefs. Analysis of both offshore in situ data and numerical hindcasts identify the predominance of two wave conditions: a mode associated with local trade winds and an episodic pattern associated with distant source long-period swells. Analysis of 10 months of in situ data within the bay show that current velocities are up to an order of magnitude greater during long-period swell episodes than during trade wind conditions; overall circulation patterns are also fundamentally different. The current velocities are highly correlated with incident wave heights during the swell episodes, while they are not during the modal trade wind conditions. A phase-averaged wave model was implemented with the dual purpose of evaluating application to bathymetrically complex fringing reefs and to examine the propagation of waves into the nearshore in an effort to better explain the large difference in observed circulation during the two offshore wave conditions. The prediction quality of this model was poorer for the episodic condition than for the lower-energy mode, however, it illustrated how longer-period swells are preferentially refracted into the bay and make available far more nearshore wave energy to drive currents compared to waves during modal conditions. The highly episodic circulation, the nature of which is dependent on complex refraction patterns of episodic, long-period swell has implications for flushing and sediment dynamics for incised fringing reef-lined bays that characterize many high islands at low latitudes around the world.

Laser fringe anemometry for aero engine components

NASA Technical Reports Server (NTRS)

Strazisar, A. J.

1986-01-01

Advances in flow measurement techniques in turbomachinery continue to be paced by the need to obtain detailed data for use in validating numerical predictions of the flowfield and for use in the development of empirical models for those flow features which cannot be readily modelled numerically. The use of laser anemometry in turbomachinery research has grown over the last 14 years in response to these needs. Based on past applications and current developments, this paper reviews the key issues which are involved when considering the application of laser anemometry to the measurement of turbomachinery flowfields. Aspects of laser fringe anemometer optical design which are applicable to turbomachinery research are briefly reviewed. Application problems which are common to both laser fringe anemometry (LFA) and laser transit anemometry (LTA) such as seed particle injection, optical access to the flowfield, and measurement of rotor rotational position are covered. The efficiency of various data acquisition schemes is analyzed and issues related to data integrity and error estimation are addressed. Real-time data analysis techniques aimed at capturing flow physics in real time are discussed. Finally, data reduction and analysis techniques are discussed and illustrated using examples taken from several LFA turbomachinery applications.

26 CFR 1.61-2T - Taxation of fringe benefits-1985 through 1988 (temporary).

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Taxation of fringe benefits-1985 through 1988 (temporary). 1.61-2T Section 1.61-2T Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY..., and Taxable Income § 1.61-2T Taxation of fringe benefits—1985 through 1988 (temporary). (a) Fringe...

Optimized Beam Sculpting with Generalized Fringe-rate Filters

NASA Astrophysics Data System (ADS)

Parsons, Aaron R.; Liu, Adrian; Ali, Zaki S.; Cheng, Carina

2016-03-01

We generalize the technique of fringe-rate filtering, whereby visibilities measured by a radio interferometer are re-weighted according to their temporal variation. As the Earth rotates, radio sources traverse through an interferometer’s fringe pattern at rates that depend on their position on the sky. Capitalizing on this geometric interpretation of fringe rates, we employ time-domain convolution kernels to enact fringe-rate filters that sculpt the effective primary beam of antennas in an interferometer. As we show, beam sculpting through fringe-rate filtering can be used to optimize measurements for a variety of applications, including mapmaking, minimizing polarization leakage, suppressing instrumental systematics, and enhancing the sensitivity of power-spectrum measurements. We show that fringe-rate filtering arises naturally in minimum variance treatments of many of these problems, enabling optimal visibility-based approaches to analyses of interferometric data that avoid systematics potentially introduced by traditional approaches such as imaging. Our techniques have recently been demonstrated in Ali et al., where new upper limits were placed on the 21 {cm} power spectrum from reionization, showcasing the ability of fringe-rate filtering to successfully boost sensitivity and reduce the impact of systematics in deep observations.

Interference Fringes of Solar Acoustic Waves around Sunspots

NASA Astrophysics Data System (ADS)

Chou, Dean-Yi; Zhao, Hui; Yang, Ming-Hsu; Liang, Zhi-Chao

2012-10-01

Solar acoustic waves are scattered by a sunspot due to the interaction between the acoustic waves and the sunspot. The sunspot, excited by the incident wave, generates the scattered wave. The scattered wave is added to the incident wave to form the total wave around the sunspot. The interference fringes between the scattered wave and the incident wave are visible in the intensity of the total wave because the coherent time of the incident wave is of the order of a wave period. The strength of the interference fringes anti-correlates with the width of temporal spectra of the incident wave. The separation between neighboring fringes increases with the incident wavelength and the sunspot size. The strength of the fringes increases with the radial order n of the incident wave from n = 0 to n = 2, and then decreases from n = 2 to n = 5. The interference fringes play a role analogous to holograms in optics. This study suggests the feasibility of using the interference fringes to reconstruct the scattered wavefields of the sunspot, although the quality of the reconstructed wavefields is sensitive to the noise and errors in the interference fringes.

Intracore and extracore examination of fiber gratings with coherent detection

NASA Astrophysics Data System (ADS)

Froggatt, Mark Earl

2001-06-01

This thesis introduces several new methods of measurement to aid in the production and evaluation of Bragg gratings in optical fiber. Five measurements are described: UV fringe visualization for grating production, weak grating measurement for distributed sensing, strong grating measurement for telecommunication applications, second harmonic grating measurement for grating chirp assessment, and grating visualization using radiation diffraction from strong Bragg gratings. The weak grating measurement for distributed strain sensing is a summary of work published prior to beginning the thesis research, and is provided for background purposes. The UV fringe visualization is accomplished by using a phase mask very close to the plane of the fiber to diffract the incoming beams used to write the Bragg grating into nearly parallel alignment, leading to macroscopic fringes indicative of the phase, frequency, amplitude, and contrast of the microscopic fringes incident on the fiber. The weak grating measurement uses Optical Frequency Domain Reflectometry (OFDR) to measure the spatial distribution of the coupling strength of weak gratings. Included in the description of the OFDR technique are recent advances in the precision monitoring of the emission wavelength of tunable lasers. The precise monitoring of wavelength is critical to the functioning of OFDR. The strong grating measurement is based on a modified form of OFDR and an analysis of the problem in the time and frequency domains to produce accurate measurements of both the reflection and transmission Transfer Functions for Bragg gratings. This measurement technique is also applicable to a wide variety of optical fiber devices, and is shown to be scalable to multiple port devices. The second-harmonic measurement for grating chirp analysis is similar to the weak grating measurement, but it was done at a wavelength resonant with the second- harmonic grating in the fiber-780 nm for 1550 nm reflection gratings. The second-harmonic grating results from nonlinearities in the grating growth process and, due to the great sensitivity of OFDR, is detectable for almost all fiber gratings. The grating visualization also uses half-wavelength (780 nm) illumination of the grating through the core. This technique uses the diffraction of light into the radiation modes to make the grating in the fiber externally visible. By operating near the perpendicular radiation condition, and introducing coherent counter- propagating light, the spatial frequency and the amplitude of the grating as functions of distance along the fiber can be measured. To better understand the radiation from Bragg gratings, a technique known as the Volume Current Method (VCM) was used to derive an expression for the radiation from a Bragg grating for all of the LP fiber modes.

Mangrove removal in the belize cays: effects on mangrove-associated fish assemblages in the intertidal and subtidal

USGS Publications Warehouse

Taylor, D.S.; Reyier, E.A.; Davis, W.P.; McIvor, C.C.

2007-01-01

We investigated the effects of mangrove cutting on fish assemblages in Twin Cays, Belize, in two habitat types. We conducted visual censuses at two sites in adjoining undisturbed/disturbed (30%–70% of shoreline fringe removed) sub-tidal fringing Rhizophora mangle Linnaeus, 1753. Observers recorded significantly more species and individuals in undisturbed sites, especially among smaller, schooling species (e.g., atherinids, clupeids), where densities were up to 200 times greater in undisturbed habitat. Multivariate analyses showed distinct species assemblages between habitats at both sites. In addition, extensive trapping with wire minnow traps within the intertidal zone in both undisturbed and disturbed fringing and transition (landward) mangrove forests was conducted. Catch rates were low: 638 individuals from 24 species over 563 trap-nights. Trap data, however, indicated that mangrove disturbance had minimal effect on species composition in either forest type (fringe/transition). Different results from the two methods (and habitat types) may be explained by two factors: (1) a larger and more detectable species pool in the subtidal habitat, with visual "access" to all species, and (2) the selective nature of trapping. Our data indicate that even partial clearing of shoreline and more landward mangroves can have a significant impact on local fish assemblages.

Phase-stepped fringe projection by rotation about the camera's perspective center.

PubMed

Huddart, Y R; Valera, J D; Weston, N J; Featherstone, T C; Moore, A J

2011-09-12

A technique to produce phase steps in a fringe projection system for shape measurement is presented. Phase steps are produced by introducing relative rotation between the object and the fringe projection probe (comprising a projector and camera) about the camera's perspective center. Relative motion of the object in the camera image can be compensated, because it is independent of the distance of the object from the camera, whilst the phase of the projected fringes is stepped due to the motion of the projector with respect to the object. The technique was validated with a static fringe projection system by moving an object on a coordinate measuring machine (CMM). The alternative approach, of rotating a lightweight and robust CMM-mounted fringe projection probe, is discussed. An experimental accuracy of approximately 1.5% of the projected fringe pitch was achieved, limited by the standard phase-stepping algorithms used rather than by the accuracy of the phase steps produced by the new technique.

Metacognition and Mindfulness: the Role of Fringe Consciousness.

PubMed

Norman, Elisabeth

2017-01-01

The involvement of metacognition in mindfulness is already acknowledged in recent mindfulness models. The focus of the current paper is on how mindfulness may be seen to involve a particular subcategory of metacognitive feeling referred to as fringe consciousness . Fringe feelings are in themselves consciously experienced but have been demonstrated to reflect nonconscious context information and are assumed to play a functional role in metacognitive monitoring and behavioral control. I first address ways in which metaexperiences during mindfulness may be seen as a variety of fringe consciousness. I then turn to how mindfulness practice may change a person's attitude to fringe feelings, which in turn may influence the ease with which currently unconscious cognitive content may be retrieved. Finally, I specifically discuss how feelings of novelty , described by many as characteristic of a mindful state, may be understood within the fringe consciousness framework. I propose that fringe consciousness may be a useful framework for understanding the relationship between cognition and certain forms of subjective feelings during mindfulness.

Mapping Sites of O-Glycosylation and Fringe Elongation on Drosophila Notch*

PubMed Central

Harvey, Beth M.; Rana, Nadia A.; Moss, Hillary; Leonardi, Jessica; Jafar-Nejad, Hamed; Haltiwanger, Robert S.

2016-01-01

Glycosylation of the Notch receptor is essential for its activity and serves as an important modulator of signaling. Three major forms of O-glycosylation are predicted to occur at consensus sites within the epidermal growth factor-like repeats in the extracellular domain of the receptor: O-fucosylation, O-glucosylation, and O-GlcNAcylation. We have performed comprehensive mass spectral analyses of these three types of O-glycosylation on Drosophila Notch produced in S2 cells and identified peptides containing all 22 predicted O-fucose sites, all 18 predicted O-glucose sites, and all 18 putative O-GlcNAc sites. Using semiquantitative mass spectral methods, we have evaluated the occupancy and relative amounts of glycans at each site. The majority of the O-fucose sites were modified to high stoichiometries. Upon expression of the β3-N-acetylglucosaminyltransferase Fringe with Notch, we observed varying degrees of elongation beyond O-fucose monosaccharide, indicating that Fringe preferentially modifies certain sites more than others. Rumi modified O-glucose sites to high stoichiometries, although elongation of the O-glucose was site-specific. Although the current putative consensus sequence for O-GlcNAcylation predicts 18 O-GlcNAc sites on Notch, we only observed apparent O-GlcNAc modification at five sites. In addition, we performed mass spectral analysis on endogenous Notch purified from Drosophila embryos and found that the glycosylation states were similar to those found on Notch from S2 cells. These data provide foundational information for future studies investigating the mechanisms of how O-glycosylation regulates Notch activity. PMID:27268051

Isochromatic photoelasticity fringe patterns of PMMA in various shapes and stress applications

NASA Astrophysics Data System (ADS)

Manjit, Y.; Limpichaipanit, A.; Ngamjarurojana, A.

2018-03-01

The research focuses on isochromatic photoelastic fringe patterns in solid materials by using reflection mode in dark field polariscope. The optical setup consists of light source, polarizers, quarter wave plates, 577 nm optical pass filter, compensator and digital camera system. The fringe patterns were produced on the sample and fractional / integer number of fringe order was observed using Babinet compensator and digital camera system. The samples were circular and rectangular shape of PMMA coated with silver spray and compressed by hydraulic system at the top and the bottom. The results of the isochromatic fringe pattern were analyzed in horizontal and vertical positions. It was found that force and the number of isochromatic photoelastic fringe order depended on shape of sample, which reflects stress distribution behavior.

Constructing a dispersed fringe sensor prototype for the Giant Magellan Telescope

NASA Astrophysics Data System (ADS)

Frostig, Danielle; McLeod, Brian; AGWS Team

2018-01-01

The Giant Magellan Telescope (GMT) will be the world’s largest telescope upon completion. The GMT employs seven 8 m primary mirror segments and seven 1 m secondary mirror segments. One challenge of the GMT is keeping the seven pairs of mirror segments on the GMT in phase. In this project, we developed and began assembly on a design for a dispersed fringe sensor prototype consisting of an optical and basic mechanical layout. The prototype design will be tested on the Magellan Clay Telescope as an experiment for future phasing methods to be used on the GMT.

Design and verification of the miniature optical system for small object surface profile fast scanning

NASA Astrophysics Data System (ADS)

Chi, Sheng; Lee, Shu-Sheng; Huang, Jen, Jen-Yu; Lai, Ti-Yu; Jan, Chia-Ming; Hu, Po-Chi

2016-04-01

As the progress of optical technologies, different commercial 3D surface contour scanners are on the market nowadays. Most of them are used for reconstructing the surface profile of mold or mechanical objects which are larger than 50 mm×50 mm× 50 mm, and the scanning system size is about 300 mm×300 mm×100 mm. There are seldom optical systems commercialized for surface profile fast scanning for small object size less than 10 mm×10 mm×10 mm. Therefore, a miniature optical system has been designed and developed in this research work for this purpose. Since the most used scanning method of such system is line scan technology, we have developed pseudo-phase shifting digital projection technology by adopting projecting fringes and phase reconstruction method. A projector was used to project a digital fringe patterns on the object, and the fringes intensity images of the reference plane and of the sample object were recorded by a CMOS camera. The phase difference between the plane and object can be calculated from the fringes images, and the surface profile of the object was reconstructed by using the phase differences. The traditional phase shifting method was accomplished by using PZT actuator or precisely controlled motor to adjust the light source or grating and this is one of the limitations for high speed scanning. Compared with the traditional optical setup, we utilized a micro projector to project the digital fringe patterns on the sample. This diminished the phase shifting processing time and the controlled phase differences between the shifted phases become more precise. Besides, the optical path design based on a portable device scanning system was used to minimize the size and reduce the number of the system components. A screwdriver section about 7mm×5mm×5mm has been scanned and its surface profile was successfully restored. The experimental results showed that the measurement area of our system can be smaller than 10mm×10mm, the precision reached to +/-10μm, and the scanning time for each surface of an object was less than 15 seconds. This has proved that our system own the potential to be a fast scanning scanner for small object surface profile scanning.

Fringe Formation in Dual-Hologram Interferometry

NASA Technical Reports Server (NTRS)

Burner, A. W.

1989-01-01

A first order geometrical optics treatment of holograms combined with the generation of interference fringes by two point sources is used to describe reference fringe formation in non-diffuse dual-hologram interferometry.

A Fast Radio Burst Search Method for VLBI Observation

NASA Astrophysics Data System (ADS)

Liu, Lei; Tong, Fengxian; Zheng, Weimin; Zhang, Juan; Tong, Li

2018-02-01

We introduce the cross-spectrum-based fast radio burst (FRB) search method for Very Long Baseline Interferometer (VLBI) observation. This method optimizes the fringe fitting scheme in geodetic VLBI data post-processing, which fully utilizes the cross-spectrum fringe phase information and therefore maximizes the power of single-pulse signals. Working with cross-spectrum greatly reduces the effect of radio frequency interference compared with using auto-power spectrum. Single-pulse detection confidence increases by cross-identifying detections from multiple baselines. By combining the power of multiple baselines, we may improve the detection sensitivity. Our method is similar to that of coherent beam forming, but without the computational expense to form a great number of beams to cover the whole field of view of our telescopes. The data processing pipeline designed for this method is easy to implement and parallelize, which can be deployed in various kinds of VLBI observations. In particular, we point out that VGOS observations are very suitable for FRB search.

Method and apparatus for white-light dispersed-fringe interferometric measurement of corneal topography

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor); Baroth, Edmund C. (Inventor)

1994-01-01

An novel interferometric apparatus and method for measuring the topography of aspheric surfaces, without requiring any form of scanning or phase shifting. The apparatus and method of the present invention utilize a white-light interferometer, such as a white-light Twyman-Green interferometer, combined with a means for dispersing a polychromatic interference pattern, using a fiber-optic bundle and a disperser such as a prism for determining the monochromatic spectral intensities of the polychromatic interference pattern which intensities uniquely define the optical path differences or OPD between the surface under test and a reference surface such as a reference sphere. Consequently, the present invention comprises a snapshot approach to measuring aspheric surface topographies such as the human cornea, thereby obviating vibration sensitive scanning which would otherwise reduce the accuracy of the measurement. The invention utilizes a polychromatic interference pattern in the pupil image plane, which is dispersed on a point-wise basis, by using a special area-to-line fiber-optic manifold, onto a CCD or other type detector comprising a plurality of columns of pixels. Each such column is dedicated to a single point of the fringe pattern for enabling determination of the spectral content of the pattern. The auto-correlation of the dispersed spectrum of the fringe pattern is uniquely characteristic of a particular optical path difference between the surface under test and a reference surface.

Interferometric measurements of the tear film irregularities on the human cornea

NASA Astrophysics Data System (ADS)

Szczesna, Dorota H.; Jaronski, Jaroslaw; Kasprzak, Henryk T.; Stenevi, Ulf

2005-09-01

The pre-ocular tear film is the most anterior refractive surface of the eye. Its stability plays an important role in the condition of vision from the optical and physiological point of view. If the eye is opened for a significantly long time or suffers from an anormalities in tear production, there appear isolated dry islands - break-ups - with a random distribution in the continuous lacrimal film. We applied an interferometric method - Lateral Shearing Technique for investigating the tear film stability and the smoothness of the tear film surface. This method is non-invasive and it is characterised by the high accuracy and sensitivity. Interferometry allows dynamic measurements of the tear film stability in real time by observation of interference fringes. The evaporation of tears and appearance of the breakups causes changes in the fringe geometry. Fast Fourier Transform has been used for quantitative assessment of the fringe smoothness and as a consequence of the tear film surface geometry. This paper presents the method used for quantitative evaluation of the tear film distribution on the cornea. Examples of interferograms recorded on eyes of patients with healthy eyes, suffering from dry eye syndrome and wearing contact lenses are also given. With our technique we were able to observe distinct differences in stability of the tear film between healthy and dry eyes, and the tear film on contact lenses.

Grating-dot two-dimensional barcode patterns with extra binary data for encoding secret information

NASA Astrophysics Data System (ADS)

Lih Yeh, Sheng; Lin, Shyh Tsong

2013-02-01

The usual two-dimensional (2D) barcode patterns do not encrypt secret information. However, secret information is sometimes needed to increase the security features of barcode patterns. Therefore, this paper proposes 2D barcode patterns created by two-beam writers to encrypt extra binary data for encoding secret information. The proposed 2D barcode patterns are composed of many grating dots and the fringes of the grating dots are classified into four types. The first type of fringe possesses a pitch of 1.1 μm and an orientation of -45°, the second type of fringe possesses a pitch of 1.2 μm and an orientation of -45°, the third type of fringe possesses a pitch of 1.1 μm and an orientation of 45°and the fourth type of fringe possesses a pitch of 1.2 μm and an orientation of 45°. All the fringes with a 1.1 μm pitch can show a color and all the fringes with a 1.2 μm pitch can show another color when a microscope is used to inspect them. Therefore, extra binary data for encoding secret information can be formed with the two pitches. On the other hand, all the fringes with a -45° orientation can become bright for a viewing direction and all the fringes with a 45° orientation can become bright for another viewing direction when one looks at them. Therefore, the grating dots with the -45° fringe orientation and the grating dots with the 45° fringe orientation can be used to show a positive barcode image and a negative barcode image, respectively. Both the positive and negative barcode images can be used to derive the barcode data. The experiment shows that the proposed barcode patterns can be used conveniently and correctly.

Code comparison for accelerator design and analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsa, Z.

1988-01-01

We present a comparison between results obtained from standard accelerator physics codes used for the design and analysis of synchrotrons and storage rings, with programs SYNCH, MAD, HARMON, PATRICIA, PATPET, BETA, DIMAD, MARYLIE and RACE-TRACK. In our analysis we have considered 5 (various size) lattices with large and small angles including AGS Booster (10/degree/ bend), RHIC (2.24/degree/), SXLS, XLS (XUV ring with 45/degree/ bend) and X-RAY rings. The differences in the integration methods used and the treatment of the fringe fields in these codes could lead to different results. The inclusion of nonlinear (e.g., dipole) terms may be necessary inmore » these calculations specially for a small ring. 12 refs., 6 figs., 10 tabs.« less

Phase unwrapping using region-based markov random field model.

PubMed

Dong, Ying; Ji, Jim

2010-01-01

Phase unwrapping is a classical problem in Magnetic Resonance Imaging (MRI), Interferometric Synthetic Aperture Radar and Sonar (InSAR/InSAS), fringe pattern analysis, and spectroscopy. Although many methods have been proposed to address this problem, robust and effective phase unwrapping remains a challenge. This paper presents a novel phase unwrapping method using a region-based Markov Random Field (MRF) model. Specifically, the phase image is segmented into regions within which the phase is not wrapped. Then, the phase image is unwrapped between different regions using an improved Highest Confidence First (HCF) algorithm to optimize the MRF model. The proposed method has desirable theoretical properties as well as an efficient implementation. Simulations and experimental results on MRI images show that the proposed method provides similar or improved phase unwrapping than Phase Unwrapping MAx-flow/min-cut (PUMA) method and ZpM method.

3D palmprint data fast acquisition and recognition

NASA Astrophysics Data System (ADS)

Wang, Xiaoxu; Huang, Shujun; Gao, Nan; Zhang, Zonghua

2014-11-01

This paper presents a fast 3D (Three-Dimension) palmprint capturing system and develops an efficient 3D palmprint feature extraction and recognition method. In order to fast acquire accurate 3D shape and texture of palmprint, a DLP projector triggers a CCD camera to realize synchronization. By generating and projecting green fringe pattern images onto the measured palm surface, 3D palmprint data are calculated from the fringe pattern images. The periodic feature vector can be derived from the calculated 3D palmprint data, so undistorted 3D biometrics is obtained. Using the obtained 3D palmprint data, feature matching test have been carried out by Gabor filter, competition rules and the mean curvature. Experimental results on capturing 3D palmprint show that the proposed acquisition method can fast get 3D shape information of palmprint. Some initial experiments on recognition show the proposed method is efficient by using 3D palmprint data.

Measurement potential of laser speckle velocimetry

NASA Technical Reports Server (NTRS)

Adrian, R. J.

1982-01-01

Laser speckle velocimetry, the measurement of fluid velocity by measuring the translation of speckle pattern or individual particles that are moving with the fluid, is described. The measurement is accomplished by illuminating the fluid with consecutive pulses of Laser Light and recording the images of the particles or the speckles on a double exposed photographic plate. The plate contains flow information throughout the image plane so that a single double exposure may provide data at hundreds or thousands of points in the illuminated region of the fluid. Conventional interrogation of the specklegram involves illuminating the plate to form Young's fringes, whose spacing is inversely proportional to the speckle separation. Subsequently the fringes are digitized and analyzed in a computer to determine their frequency and orientation, yielding the velocity magnitude and orientation. The Young's fringe technique is equivalent to performing a 2-D spatial correlation of the double exposed specklegram intensity pattern, and this observation suggests that correlation should be considered as an alternative processing method. The principle of the correlation technique is examined.

Computationally-efficient optical coherence elastography to assess degenerative osteoarthritis based on ultrasound-induced fringe washout (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tong, Minh Q.; Hasan, M. Monirul; Gregory, Patrick D.; Shah, Jasmine; Park, B. Hyle; Hirota, Koji; Liu, Junze; Choi, Andy; Low, Karen; Nam, Jin

2017-02-01

We demonstrate a computationally-efficient optical coherence elastography (OCE) method based on fringe washout. By introducing ultrasound in alternating depth profile, we can obtain information on the mechanical properties of a sample within acquisition of a single image. This can be achieved by simply comparing the intensity in adjacent depth profiles in order to quantify the degree of fringe washout. Phantom agar samples with various densities were measured and quantified by our OCE technique, the correlation to Young's modulus measurement by atomic force micrscopy (AFM) were observed. Knee cartilage samples of monoiodo acetate-induced arthiritis (MIA) rat models were utilized to replicate cartilage damages where our proposed OCE technique along with intensity and birefringence analyses and AFM measurements were applied. The results indicate that our OCE technique shows a correlation to the techniques as polarization-sensitive OCT, AFM Young's modulus measurements and histology were promising. Our OCE is applicable to any of existing OCT systems and demonstrated to be computationally-efficient.

Pixel-by-pixel absolute phase retrieval using three phase-shifted fringe patterns without markers

NASA Astrophysics Data System (ADS)

Jiang, Chufan; Li, Beiwen; Zhang, Song

2017-04-01

This paper presents a method that can recover absolute phase pixel by pixel without embedding markers on three phase-shifted fringe patterns, acquiring additional images, or introducing additional hardware component(s). The proposed three-dimensional (3D) absolute shape measurement technique includes the following major steps: (1) segment the measured object into different regions using rough priori knowledge of surface geometry; (2) artificially create phase maps at different z planes using geometric constraints of structured light system; (3) unwrap the phase pixel by pixel for each region by properly referring to the artificially created phase map; and (4) merge unwrapped phases from all regions into a complete absolute phase map for 3D reconstruction. We demonstrate that conventional three-step phase-shifted fringe patterns can be used to create absolute phase map pixel by pixel even for large depth range objects. We have successfully implemented our proposed computational framework to achieve absolute 3D shape measurement at 40 Hz.

Phase shifting interferometry based on a vibration sensor - feasibility study on elimination of the depth degeneracy

NASA Astrophysics Data System (ADS)

Lee, Seung Seok; Kim, Ju Ha; Choi, Eun Seo

2017-04-01

We proposed novel phase-shifting interferometry using a fiber-optic vibration sensor. The Doppler shift in the coiled fiber caused by vibrations can be used to detect the vibrations by using a fiber-optic interferometer. The principle can be applied to induce phase shifts. While applying vibrations to the coiled fiber at various vibration frequencies, we recorded the variations in the interference fringes. The interference fringe moved to longer wavelengths when a vibration frequency was increased from 38.00 to 38.40 kHz. Phase variations of 3.59 rad/kHz were obtained. The ability to accurately control the phase by using the vibrations in the coiled fiber was demonstrated by the elimination of the depth degeneracy using the complex signal generated by the phase-shifted interference fringes. Using vibrations to control phase shifting can be an acceptable alternative to conventional methods and can be applied to resolve the depth ambiguity in Fourier domain optical coherence tomography.

A novel design measuring method based on linearly polarized laser interference

NASA Astrophysics Data System (ADS)

Cao, Yanbo; Ai, Hua; Zhao, Nan

2013-09-01

The interferometric method is widely used in the precision measurement, including the surface quality of the large-aperture mirror. The laser interference technology has been developing rapidly as the laser sources become more and more mature and reliable. We adopted the laser diode as the source for the sake of the short coherent wavelength of it for the optical path difference of the system is quite shorter as several wavelengths, and the power of laser diode is sufficient for measurement and safe to human eye. The 673nm linearly laser was selected and we construct a novel form of interferometric system as we called `Closed Loop', comprised of polarizing optical components, such as polarizing prism and quartz wave plate, the light from the source split by which into measuring beam and referencing beam, they've both reflected by the measuring mirror, after the two beams transforming into circular polarization and spinning in the opposite directions we induced the polarized light synchronous phase shift interference technology to get the detecting fringes, which transfers the phase shifting in time domain to space, so that we did not need to consider the precise-controlled shift of optical path difference, which will introduce the disturbance of the air current and vibration. We got the interference fringes from four different CCD cameras well-alignment, and the fringes are shifted into four different phases of 0, π/2, π, and 3π/2 in time. After obtaining the images from the CCD cameras, we need to align the interference fringes pixel to pixel from different CCD cameras, and synthesis the rough morphology, after getting rid of systematic error, we could calculate the surface accuracy of the measuring mirror. This novel design detecting method could be applied into measuring the optical system aberration, and it would develop into the setup of the portable structural interferometer and widely used in different measuring circumstances.

Real-time vibration measurement by a spatial phase-shifting technique with a tilted holographic interferogram.

PubMed

Nakadate, S; Isshiki, M

1997-01-01

Real-time vibration measurement by a tilted holographic interferogram is presented that utilizes the real-time digital fringe processor of a video signal. Three intensity data sampled at every one-third of the fringe spacing of the tilted fringes are used to calculate the modulation term of the fringe that is a function of a vibration amplitude. A three-dimensional lookup table performs the calculation in a TV repetition rate to give a new fringe profile that contours the vibration amplitude. Vibration modes at the resonant frequencies of a flat speaker were displayed on a monitor as changing the exciting frequency of vibration.

FIELD SAMPLING OF RESIDUAL AVIATION GASOLINE IN SANDY SOIL

EPA Science Inventory

Two complimentary field sampling methods for the determination of residual aviation gasoline content in the contaminated capillary fringe of a fine, uniform, sandy soil were investigated. The first method featured filed extrusion of core barrels into pint size Mason jars, while ...

Edge detection based on adaptive threshold b-spline wavelet for optical sub-aperture measuring

NASA Astrophysics Data System (ADS)

Zhang, Shiqi; Hui, Mei; Liu, Ming; Zhao, Zhu; Dong, Liquan; Liu, Xiaohua; Zhao, Yuejin

2015-08-01

In the research of optical synthetic aperture imaging system, phase congruency is the main problem and it is necessary to detect sub-aperture phase. The edge of the sub-aperture system is more complex than that in the traditional optical imaging system. And with the existence of steep slope for large-aperture optical component, interference fringe may be quite dense when interference imaging. Deep phase gradient may cause a loss of phase information. Therefore, it's urgent to search for an efficient edge detection method. Wavelet analysis as a powerful tool is widely used in the fields of image processing. Based on its properties of multi-scale transform, edge region is detected with high precision in small scale. Longing with the increase of scale, noise is reduced in contrary. So it has a certain suppression effect on noise. Otherwise, adaptive threshold method which sets different thresholds in various regions can detect edge points from noise. Firstly, fringe pattern is obtained and cubic b-spline wavelet is adopted as the smoothing function. After the multi-scale wavelet decomposition of the whole image, we figure out the local modulus maxima in gradient directions. However, it also contains noise, and thus adaptive threshold method is used to select the modulus maxima. The point which greater than threshold value is boundary point. Finally, we use corrosion and expansion deal with the resulting image to get the consecutive boundary of image.

[Research on improving spectrum resolution of optimized Wollaston prism array].

PubMed

Zhang, Peng; Wang, Jian-Rong; Zhang, Guo-Chen; Hou, Wen

2011-11-01

In order to not affect the image quality of interference fringes on the basis of the structure by increasing the structure angle of Wollaston prism to improve spectrum resolution, the authors optimized the structure of Wollaston prism. Calculating the function of the splitting angle and the structure angle, analysis indicated that taking the isosceles triangle prism with the same nature of the second wedge-shaped prism after the Wollaston prism, which makes the o and e light parallel to the optical axis, and alpha=0 degrees, the imaging interference fringes are no longer affected by changes in the splitting angle. Several optimized Wollaston prisms were made as an array to improve the spectral resolution. Experiments used traditional and optimized Wollaston prism array to detect the spectrum of the 980 nm laser. Experimental data showed that using optimized Wollaston prism array gets a clearer contrast of interference fringes, and the spectral data with Fourier transform are more accurate with DSP.

Mitigating fringing in discrete frequency infrared imaging using time-delayed integration

PubMed Central

Ran, Shihao; Berisha, Sebastian; Mankar, Rupali; Shih, Wei-Chuan; Mayerich, David

2018-01-01

Infrared (IR) spectroscopic microscopes provide the potential for label-free quantitative molecular imaging of biological samples, which can be used to aid in histology, forensics, and pharmaceutical analysis. Most IR imaging systems use broadband illumination combined with a spectrometer to separate the signal into spectral components. This technique is currently too slow for many biomedical applications such as clinical diagnosis, primarily due to the availability of bright mid-infrared sources and sensitive MCT detectors. There has been a recent push to increase throughput using coherent light sources, such as synchrotron radiation and quantum cascade lasers. While these sources provide a significant increase in intensity, the coherence introduces fringing artifacts in the final image. We demonstrate that applying time-delayed integration in one dimension can dramatically reduce fringing artifacts with minimal alterations to the standard infrared imaging pipeline. The proposed technique also offers the potential for less expensive focal plane array detectors, since linear arrays can be more readily incorporated into the proposed framework. PMID:29552416

Interferometric visualization and demodulation method for measuring quasi-static strain in fiber Bragg grating sensors by a simple rotating etalon filter

NASA Astrophysics Data System (ADS)

Rocco, Alessandra S.; Coppola, Giuseppe; Ferraro, Pietro; Foti, Giuseppe; Iodice, Mario

2004-09-01

Optical fiber sensors are the ideal system to monitor "smart structures" and on-site/real time stress measurements: they can be in fact easily embedded or attached to the structures under test and are not affected by electro- magnetic noise. In particular a signal from a Fiber Bragg grating sensor (FBG) may be processed such that its information remains immune to optical power fluctuations. Different interrogation methods can be used for reading out Bragg wavelength shifts. In this paper we propose a very simple interferometric method for interrogating FBG sensors, based on bi-polished silicon sample acting like an etalon tuneable filter (ETF). The Bragg wavelength shift can be evaluated by analyzing the spectral response of signal reflected by the FBG sensor and filtered by the ETF that is continuously and rapidly tuned. Tuning was obtained by rotating the ETF. Variation in the strain at the FBG causes a phase shift in the analyzed signal. The overall spectral signal, collected with time, consists in an interferometric figure which finesse and fringe contrast depending on the geometrical sizes and facets reflectivity of the silicon sample. The fringe pattern, expressed by the Airy's formula, depends on the wavelength l of the incident radiation and on the angle of incidence. The phase of fringe pattern can be retrieved by a standard FFT method giving quantitative measurements of the quasi-static strain variation sensed by the FBG. In this way, the method allows a valuable visualization of the time-evolution of the incremental strain applied to the FBG. Principle of functioning of this method is described and first results obtained employing such configuration, are reported.

Effects of the Tax Treatment of Fringe Benefits on Labor Market Segmentation.

ERIC Educational Resources Information Center

Scott, Frank A.; And Others

1989-01-01

Argues that the provision of the same fringe benefits for all workers promotes labor market segmentation by inducing workers to sort themselves across the economy according to their demand for fringe benefits. (JOW)

Fringe formation in dual-hologram interferometry

NASA Technical Reports Server (NTRS)

Burner, A. W.

1990-01-01

Reference-fringe formation in nondiffuse dual-hologram interferometry is described by combining a first-order geometrical hologram treatment with interference fringes generated by two point sources. The first-order imaging relationships can be used to describe reference-fringe patterns for the geometry of the dual-hologram interferometry. The process can be completed without adjusting the two holograms when the reconstructing wavelength is less than the exposing wavelength, and the process is found to facilitate basic intereferometer adjustments.

Interferogram conditioning for improved Fourier analysis and application to X-ray phase imaging by grating interferometry.

PubMed

Montaux-Lambert, Antoine; Mercère, Pascal; Primot, Jérôme

2015-11-02

An interferogram conditioning procedure, for subsequent phase retrieval by Fourier demodulation, is presented here as a fast iterative approach aiming at fulfilling the classical boundary conditions imposed by Fourier transform techniques. Interference fringe patterns with typical edge discontinuities were simulated in order to reveal the edge artifacts that classically appear in traditional Fourier analysis, and were consecutively used to demonstrate the correction efficiency of the proposed conditioning technique. Optimization of the algorithm parameters is also presented and discussed. Finally, the procedure was applied to grating-based interferometric measurements performed in the hard X-ray regime. The proposed algorithm enables nearly edge-artifact-free retrieval of the phase derivatives. A similar enhancement of the retrieved absorption and fringe visibility images is also achieved.

Flow-dependent porosity and other biomechanical properties of mysticete baleen.

PubMed

Werth, Alexander J

2013-04-01

Despite its vital function in a highly dynamic environment, baleen is typically assumed to be a static material. Its biomechanical and material properties have not previously been explored. Thus I tested sections of baleen from bowhead whales, Balaena mysticetus, and humpback whales, Megaptera novaeangliae, alone or in groups representing miniature 'racks', in a flow tank through which water and buoyant particles circulated with variable flow velocity. Kinematic sequences were recorded through an endoscopic camera or viewing window. One set of experiments investigated particle capture; another series analyzed biomechanical behavior, including fringe spacing, movement and interaction. Baleen fringe porosity directly correlates, in a mostly linear fashion, with velocity of incident water flow. However, undulation and interaction of fringes (especially of bowheads) at higher flow velocities can decrease porosity. Fringe porosity depends on distance from the baleen plate. Porosity also varies, with fringe length, by position along the length of an individual plate. Plate orientation, which varied from 0 to 90 deg relative to water flow, is crucial in fringe spacing and particle capture. At all flow velocities, porosity is lowest with plates aligned parallel to water flow. Turbulence introduced when plates rotate perpendicular to flow (as in cross-flow filtration) increases fringe interaction, so that particles more easily strike fringes yet more readily dislodge. Baleen of bowhead whales, which feed by continuous ram filtration, differs biomechanically from that of humpbacks, which use intermittent lunge filtration. The longer, finer fringes of bowhead baleen readily form a mesh-like mat, especially at higher flow velocities, to trap tiny particles.

Modulation transfer function measurement of microbolometer focal plane array by Lloyd's mirror method

NASA Astrophysics Data System (ADS)

Druart, Guillaume; Rommeluere, Sylvain; Viale, Thibault; Guerineau, Nicolas; Ribet-Mohamed, Isabelle; Crastes, Arnaud; Durand, Alain; Taboury, Jean

2014-05-01

Today, both military and civilian applications require miniaturized and cheap optical systems. One way to achieve this trend consists in decreasing the pixel pitch of focal plane arrays (FPA). In order to evaluate the performance of the overall optical systems, it is necessary to measure the modulation transfer function (MTF) of these pixels. However, small pixels lead to higher cut-off frequencies and therefore, original MTF measurements that are able to extract frequencies up to these high cut-off frequencies, are needed. In this paper, we will present a way to extract 1D MTF at high frequencies by projecting fringes on the FPA. The device uses a Lloyd mirror placed near and perpendicular to the focal plane array. Consequently, an interference pattern of fringes can be projected on the detector. By varying the angle of incidence of the light beam, we can tune the period of the interference fringes and, thus, explore a wide range of spatial frequencies, and mainly around the cut-off frequency of the pixel which is one of the most interesting area. Illustration of this method will be applied to a 640×480 microbolometer focal plane array with a pixel pitch of 17µm in the LWIR spectral region.

Reconstruction method for fringe projection profilometry based on light beams.

PubMed

Li, Xuexing; Zhang, Zhijiang; Yang, Chen

2016-12-01

A novel reconstruction method for fringe projection profilometry, based on light beams, is proposed and verified by experiments. Commonly used calibration techniques require the parameters of projector calibration or the reference planes placed in many known positions. Obviously, introducing the projector calibration can reduce the accuracy of the reconstruction result, and setting the reference planes to many known positions is a time-consuming process. Therefore, in this paper, a reconstruction method without projector's parameters is proposed and only two reference planes are introduced. A series of light beams determined by the subpixel point-to-point map on the two reference planes combined with their reflected light beams determined by the camera model are used to calculate the 3D coordinates of reconstruction points. Furthermore, the bundle adjustment strategy and the complementary gray-code phase-shifting method are utilized to ensure the accuracy and stability. Qualitative and quantitative comparisons as well as experimental tests demonstrate the performance of our proposed approach, and the measurement accuracy can reach about 0.0454 mm.

A systematic desaturation method for images from the Atmospheric Imaging Assembly in the Solar Dynamics Observatory.

NASA Astrophysics Data System (ADS)

Torre, Gabriele; Schwartz, Richard; Piana, Michele; Massone, Anna Maria; Benvenuto, Federico

2016-05-01

The fine spatial resolution of the SDO AIA CCD's is often destroyed by the charge in saturated pixels overflowing into a swath of neighboring cells during fast rising solar flares. Automated exposure control can only mitigate this issue to a degree and it has other deleterious effects. Our method addresses the desaturation problem for AIA images as an image reconstruction problem in which the information content of the diffraction fringes, generated by the interaction between the incoming radiation and the hardware of the spacecraft, is exploited to recover the true image intensities within the primary saturated core of the image. This methodology takes advantage of some well defined techniques like cross-correlation and the Expectation Maximization method to invert the direct relation between the diffraction fringes intensities and the true flux intensities. During this talk a complete overview on the structure of the method will be provided, besides some reliability tests obtained by its application against synthetic and real data.

Moire-Fringe Images of Twin Boundaries in Chemical Vapor Deposited Diamond

DTIC Science & Technology

1992-07-10

Moire-Fringe Images of Twin Boundaries in Chemical Vapor Deposited Diamond IJ PERSONAL AUITHOR(S) - D. Shechtman. A. Fldman, M.D. Vaudin, and J.L...micrographs of chemical vapor deposited diamond can be interprete as Moire fringes that occur when viewing twin boundaries that are inclined to the electron...Dist J Special TECHNICAL REPORT No. 14 eca MOIRE-FRINGE IMAGES OF TWIN BOUNDARIES IN CHEMICAL VAPOR DEPOSITED DIAMOND D. Shechtman, A. Feldman, M.D

Advanced Dispersed Fringe Sensing Algorithm for Coarse Phasing Segmented Mirror Telescopes

NASA Technical Reports Server (NTRS)

Spechler, Joshua A.; Hoppe, Daniel J.; Sigrist, Norbert; Shi, Fang; Seo, Byoung-Joon; Bikkannavar, Siddarayappa A.

2013-01-01

Segment mirror phasing, a critical step of segment mirror alignment, requires the ability to sense and correct the relative pistons between segments from up to a few hundred microns to a fraction of wavelength in order to bring the mirror system to its full diffraction capability. When sampling the aperture of a telescope, using auto-collimating flats (ACFs) is more economical. The performance of a telescope with a segmented primary mirror strongly depends on how well those primary mirror segments can be phased. One such process to phase primary mirror segments in the axial piston direction is dispersed fringe sensing (DFS). DFS technology can be used to co-phase the ACFs. DFS is essentially a signal fitting and processing operation. It is an elegant method of coarse phasing segmented mirrors. DFS performance accuracy is dependent upon careful calibration of the system as well as other factors such as internal optical alignment, system wavefront errors, and detector quality. Novel improvements to the algorithm have led to substantial enhancements in DFS performance. The Advanced Dispersed Fringe Sensing (ADFS) Algorithm is designed to reduce the sensitivity to calibration errors by determining the optimal fringe extraction line. Applying an angular extraction line dithering procedure and combining this dithering process with an error function while minimizing the phase term of the fitted signal, defines in essence the ADFS algorithm.

Continuous flow Overhauser dynamic nuclear polarization of water in the fringe field of a clinical magnetic resonance imaging system for authentic image contrast

PubMed Central

Lingwood, Mark D.; Siaw, Ting Ann; Sailasuta, Napapon; Ross, Brian D.; Bhattacharya, Pratip; Han, Songi

2016-01-01

We describe and demonstrate a system to generate hyperpolarized water in the 0.35 T fringe field of a clinical 1.5 T whole-body magnetic resonance imaging (MRI) magnet. Once generated, the hyperpolarized water is quickly and continuously transferred from the 0.35 T fringe to the 1.5 T center field of the same magnet for image acquisition using standard MRI equipment. The hyperpolarization is based on Overhauser dynamic nuclear polarization (DNP), which effectively and quickly transfers the higher spin polarization of free radicals to nuclear spins at ambient temperatures. We visualize the dispersion of hyperpolarized water as it flows through water-saturated systems by utilizing an observed −15 fold DNP signal enhancement with respect to the unenhanced 1H MRI signal of water at 1.5 T. The experimental DNP apparatus presented here is readily portable and can be brought to and used with any conventional unshielded MRI system. A new method of immobilizing radicals to gel beads via polyelectrolyte linker arms is described, which led to superior flow Overhauser DNP performance compared to previously presented gels. We discuss the general applicability of Overhauser DNP hyperpolarization of water and aqueous solutions in the fringe field of commercially available magnets with central fields up to 4.7 Tesla. PMID:20541445

Investigation on the impact of irregular fringe patterns of a single-fiber Mach-Zehnder interferometer on its sensing capabilities

NASA Astrophysics Data System (ADS)

Kumar, Naveen; Kumar, Ashish

2018-07-01

A novel single-mode single-fiber (SMSF) MZI formed by cascading of two non-adiabatic fiber tapers, with stable and repeatable spectrum, has been found to be useful in sensing applications in recent times. A multimode interference based novel simulation approach is proposed to predict the sensing characteristics of SMSF-MZI and is validated with experimental observation. The proposed method includes solving of simultaneous non-homogenous equations for determining the amplitudes of the interfering modes excited in the tapered section of the interferometer. The simulated fringe pattern and the experimental spectral response converge to some important comprehension reported for the first time. A linear shift in output spectral response, of SMSF-MZI, due to change in optical path length induced by temperature/strain etc., is likely to be characterized by three modes interference occurring in the interference region of the interferometer. Whereas if the spectral shift starts saturating at moderately higher temperature/strain, then the formation of interference fringes are possibly governed by two modes interference. Further, it was also explained that a SMSF-MZI with variable fringe widths in its spectral pattern exhibits higher sensitivity than that of the SMSF-MZI having wavelength spectrum with uniform free spectral range. These findings are useful in selecting and predicting the sensitivity of a given SMSF-MZI, based on its spectrum, for sensing applications.

Pulsed coherent population trapping with repeated queries for producing single-peaked high contrast Ramsey interference

NASA Astrophysics Data System (ADS)

Warren, Z.; Shahriar, M. S.; Tripathi, R.; Pati, G. S.

2018-02-01

A repeated query technique has been demonstrated as a new interrogation method in pulsed coherent population trapping for producing single-peaked Ramsey interference with high contrast. This technique enhances the contrast of the central Ramsey fringe by nearly 1.5 times and significantly suppresses the side fringes by using more query pulses ( >10) in the pulse cycle. Theoretical models have been developed to simulate Ramsey interference and analyze the characteristics of the Ramsey spectrum produced by the repeated query technique. Experiments have also been carried out employing a repeated query technique in a prototype rubidium clock to study its frequency stability performance.

Geometrical optics modeling of the grating-slit test.

PubMed

Liang, Chao-Wen; Sasian, Jose

2007-02-19

A novel optical testing method termed the grating-slit test is discussed. This test uses a grating and a slit, as in the Ronchi test, but the grating-slit test is different in that the grating is used as the incoherent illuminating object instead of the spatial filter. The slit is located at the plane of the image of a sinusoidal intensity grating. An insightful geometrical-optics model for the grating-slit test is presented and the fringe contrast ratio with respect to the slit width and object-grating period is obtained. The concept of spatial bucket integration is used to obtain the fringe contrast ratio.

Holographic Moire, An Optical Tool For The Determination Of Displacements, Strains, Contours, And Slopes Of Surfaces

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.

1982-06-01

In conventional holographic interferometry, the observed fringe patterns are determined by the object displacement and deformation, and by the illumination and observation configurations. The obtained information may not be in the most convenient form for further data processing. To overcome this problem, and to create new possibilities, holographic fringe patterns can be changed by modifying the optical setup. As a result of these modifications, well-known procedures of the moire method can be applied to holographic interferometry. Components of displacement and components of the strain tensor can be isolated and measured separately. Surface contours and slopes can also be determined.