A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

We first provide an overview of 3-D shape measurement us- ing various optical methods. Then we focus on structured light tech- niques where various optical configurations, image acquisition tech- niques, data postprocessing and analysis methods and advantages and limitations are presented. Several industrial application examples are presented. Important areas requiring further R&D are discussed. Finally, a comprehensive bibliography on 3-D shape measurement is included, although it is not intended to be exhaustive. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00101-X)

Overview of three-dimensional shape measurement using optical methods

Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

http://ieeexplore.ieee.org/iel5/3/23094/01073023.pdf

Statistical optics

A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

/pdf/heat-and-mass-transfer-1yaijfx8vp.pdf

Heat and Mass Transfer

The problems connected with experimental and numerical controlling of laser beam welds are described. The methodology and instrumentation for determination of laser weldment properties based on automated grating interferometry are presented. The experimental procedure which includes the measurement of displacement/strain fields induced by residual stress released by cutting and the determination of local material properties in a weld under tensile load are shown. The experimental results have shown Poisson's ratio variations in a weld cross-section and the strain distributions at the surface of specimen after stress releasing in the weld and distant regions.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Determination of laser beam weldment properties by grating interferometry method

Limited angle optical diffraction tomography (ODT) is a 3D quantitative phase imaging method that allows to retrieve information about 3D refractive index (RI) distribution of live, unlabeled biosamples. The main limitation of this method is that its common transmission configuration results in very low axial resolution. On the other hand, optical coherence tomography (OCT), working in its most popular reflection configuration retrieves information about the gradient of the RI of investigated samples. However, the results are of qualitative nature. Moreover, due to low numerical aperture of the objective lens typically used in OCT systems, the resolution is high in the axial direction and relatively low in transverse direction. From the point of view of K-space filling, these two imaging modalities are complementary. Here we present a method of combining ODT projections with OCT scans. The combined technique, called optical coherence diffraction tomography (OCDT) operates in transflective mode, where ODT is captured in transmission and OCT in reflection. Theory behind conversion of OCT scans into ODT projections is given. With the use of numerical simulations we show what enhancement can be obtained when OCT and ODT data are combined directly. Also, experimental verification is presented.

Enhanced QPI functionality by combining OCT and ODT methods

Instrumentation and data postprocessing problems connected with local measurements of high gradient in-plane displacement/strain fields by automated grating interferometer are considered A new version of waveguide grating microinterferometer is proposed Various paths of postprocessing are investigated and data reduction and interpolation technique with adaptive size of elementary sampling area is recommended for strain and local material constant determination The usefulness of the technique is shown on the base of ceramic-to-metal joint investigation

Local measurements of high-gradient in-plane displacement/strain fields by automated grating interferometry

The creation of a virtual object for CAD/CAM and computer graphics on the base of data gathered by full-field optical measurement of 3D object is presented. The experimental co- ordinates are alternatively obtained by combined fringe projection/photogrammetry based system or fringe projection/virtual markers setup. The new and fully automatic procedure which process the cloud of measured points into triangular mesh accepted by CAD/CAM and computer graphics systems is presented. Its applicability for various classes of objects is tested including the error analysis of virtual objects generated. The usefulness of the method is proved by applying the virtual object in rapid prototyping system and in computer graphics environment.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

3D object optonumerical acquisition methods for CAD/CAM and computer graphics systems

Optomechatronics cameras based on digital holography and grating interferometry are presented. Their compact design, “black box” operational approach and interferometric data processing are described. The representative examples of applications in experimental mechanics, microelements testing and outdoor engineering measurements are presented.

Malgorzata Kujawinska

Papers

Determination of laser beam weldment properties by grating interferometry method

Enhanced QPI functionality by combining OCT and ODT methods

Local measurements of high-gradient in-plane displacement/strain fields by automated grating interferometry

3D object optonumerical acquisition methods for CAD/CAM and computer graphics systems

Optomechatronics cameras for full-field, remote monitoring and measurements of mechanical parts