Dual-beam symmetric illumination-observation TV holography system for measurements
01 Dec 2001-Optical Engineering (International Society for Optics and Photonics)-Vol. 40, Iss: 12, pp 2780-2787
TL;DR: In this article, instead of observing along the optical axis, the scattered light along the direction of the illumination beams, and imaged it as two separate images onto the photo sensor of a CCD camera, was used for real-time evaluation of in-plane displacement components as well as surface shape.
Abstract: The Leendertz dual-beam symmetric illumination-normal ob- servation arrangement is widely employed for real time evaluation of in-plane displacement components as well as surface shape. Instead of observing along the optical axis, we have examined the Leendertz ar- rangement by observing the scattered light along the direction of the illumination beams, and imaged it as two separate images onto the photo sensor of a CCD camera. The interferometer is a combination of two channels, each of which measures independently and simulta- neously the information pertaining to either the in-plane displacement component of a deformation vector, or the surface relief variation of a three-dimensional object. In addition, a summary of possible measure- ments that can be carried out from the present arrangement is also high- lighted. Experimental results using a four-frame phase shifting technique are illustrated. © 2001 Society of Photo-Optical Instrumentation Engineers.
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TL;DR: This poster presents a poster presenting a probabilistic procedure to constrain the response of the immune system to chemotherapy-like injuries in mice.
Abstract: Reference IMAC-ARTICLE-2003-007View record in Web of Science Record created on 2007-06-13, modified on 2016-08-08
37 citations
Additional excerpts
...While the arrangement [14] senses the in-plane displacement with sensitivity proposed by Leendertz [2], the one described in [11,12] yields two-fold increase in sensitivity....
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TL;DR: In this paper, a reference beam is added to a dual-beam symmetric illumination electronic speckle pattern interferometry (ESPI) system and shared by the two illuminations.
Abstract: A method for three-dimensional (3D) displacement measurement by separating out-of-plane displacement from in-plane displacement is presented. A reference beam is added to a dual-beam symmetric illumination electronic speckle pattern interferometry (ESPI) system and shared by the two illuminations. The test object is illuminated by the two object beams, respectively. Two phase maps, which include out-of-plane and in-plane displacement, can be obtained by phase-shifting techniques. In order to decrease electronic noises in the phase maps, one of the phase maps is calculated by the reversed phase-shifting method presented. By using inverse phase distribution, out-of-plane displacement can be easily separated from in-plane displacement by subtraction and can greatly decrease electronic noises. The principle of the method is presented and proved by a typical three-point bending experiment. Experimental results are offered.
10 citations
28 Jul 2017
TL;DR: In this paper, a three-dimensional interference pattern formed by the interference of secondary, dephased wavelets scattered by an optical rough surface or transmitted through a scattered medium that imposes random phases of the wave.
Abstract: Speckle pattern is a three-dimensional (3D) interference pattern formed by the interference of secondary, dephased wavelets scattered by an optical rough surface or transmitted through a scattered medium that imposes random phases of the wave. The randomly coded pattern that carries the information about the object deformation provided to develop a wide range of methods, which can be classified into three broad categories: speckle photography, speckle interferometry, and speckle shear interferometry. Speckle photography is based on recording of objective or subjective speckle patterns, before and after the object is subjected to load. Digital speckle shear interferometry or digital shearography (DS) has been widely used for the measurement of the spatial derivatives of object deformation. The DS system has found a prominent application in aerospace industry for nondestructive testing of spacecraft structures. Microsystems such as micro-electro-mechanical systems and micro-opto-electromechanical systems combining micro-size electrical and mechanical mechanism are finding increasing applications in various fields.
3 citations
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TL;DR: In this article, the distribution of intensity in the resultant pattern depends on the relative phases of the component patterns, and by measuring the correlation between the resultant patterns at two different times a change of relative phase is detected.
Abstract: When a surface is illuminated with laser light it has a speckled appearance due to random interference. If two speckle patterns are superimposed the distribution of intensity in the resultant pattern depends on the relative phases of the component patterns. By measuring the correlation between the resultant patterns at two different times a change of relative phase is detected. This leads to a versatile method of measuring either the normal or in-plane components of displacement over the whole of a surface at one time.
461 citations
TL;DR: In this paper, a stereo imaging system was used to measure the 3D displacement field around the crack tip of a fracture specimen, and the measured displacement fields expressed in the world coordinates were converted, through coordinate transformations, to the displacement field expressed in specimen crack tip coordinates.
Abstract: Based on a pinhole camera model, camera model equations that account for the radial lens distortion are used to map three-dimensional (3-D) world coordinates to two-dimensional (2-D) computer image coordinates. Using two cameras to form a stereo vision, the 3-D information can be obtained. It is demonstrated that such stereo imaging systems can be used to measure the 3-D displacement field around the crack tip of a fracture specimen. To compare with the available 2-D theory of fracture mechanics, the measured displacement fields expressed in the world coordinates are converted, through coordinate transformations, to the displacement fields expressed in specimen crack tip coordinates. By using a smoothing technique, the in-plane displacement components are smoothed and the total strains are obtained. Rigid body motion is eliminated from the smoothed in-plane displacement components and unsmoothed out-of-plane displacement. Compared with the theoretical elastic-plastic field at a crack tip, the results appear to be consistent with expected trends, which indicates that the stereo imaging system is a viable tool for the 3-D deformation analysis of fracture specimens.
112 citations
TL;DR: The sensitivity and the orientation of the contour planes are analyzed and a novel method for tilting the planes of contours and experimental results incorporating phase shifting and fringe analysis are presented.
Abstract: In this paper we extend and study the method for generating contours of diffuse objects employing a dual beam illumination coupled with electronic speckle pattern interferometry. The sensitivity and the orientation of the contour planes are analyzed. A novel method for tilting the planes of contours and experimental results incorporating phase shifting and fringe analysis are also presented. The theoretical and the experimental results show good agreement.
77 citations
TL;DR: A technique for nondestructive testing based on phase shifting TV holography and digital image processing is presented, which calculates the phase modulation of the object light caused by object deformation and smoothed the resulting deformation phase image to obtain a better signal-to-noise ratio.
Abstract: We present a technique for nondestructive testing based on phase shifting TV holography and digital image processing With this technique we calculate the phase modulation of the object light caused by object deformation The resulting deformation phase image is smoothed to obtain a better signal-to-noise ratio Smoothing is done by a new low pass filtering procedure we call phase shifting convolution This procedure is based on smoothing of two phase images: the original phase image and a second image obtained by spatial phase shift of the original phase image By combining the two smoothed images we obtain an image without smoothing errors close to the 2π phase ambiguities in the deformation phase image To detect surface areas with local inhomogeneous deformations indicating material defects, we calculate and display the deformation phase gradients Examples with testing of composite materials are shown
69 citations
TL;DR: In this article, a TV system was developed for detecting and displaying a two-dimensional hologram image that permits concomitant (real-time) hologram interferometry, where a uniform reference field interferes at zero offset angle with a speckled image of an object.
Abstract: A TV system has been developed for detecting and displaying a two-dimensional hologram image that permits concomitant (real-time) hologram interferometry The optics employed are the same as for electronic speckle pattern interferometry (ESPI), wherein a uniform reference field interferes at zero offset angle with a speckled image of an object Rather than detecting spatial modulation to indicate interference, as in ESPI, this system modulates the phase of the reference beam by 120° between picture frames to vary speckle irradiance Each incoming frame is compared with the two previous frames, and only pixels that vary in brightness are passed as white pixels in the video output The use of binary-valued pixels allows inexpensive data processing at standard video rates
44 citations