Experiments using Liquid Crystal Televisions (LCTVs) as spatial light modulators for optical correlators, and optical input devices, have been reported upon widely. Moreover, applications of these devices for target recognition and automatic inspection systems are well documented. These systems often require the implementation of computer pre-and postprocessing for image filtering and target recognition which handicaps real-time optical processing applications.It is possible to construct custom reference gratings that form a desired moire pattern when mixed with images of structurally illuminated targets. The moire patterns can be in any form, from equal depth contours, to error maps, to any arbitrary pattern desired. We have demonstrated video methods to generate such error maps in real-time. Furthermore, we have removed restrictions on the shape of the output moire contours, thus, developing a real-time automated inspection system based on the optical processing of arbitrary moire contours. We chose the moire pattern to be in the form of a Fresnel zone plate which is sent to an LCTV. Illumination of this zone plate with parallel coherent light results in a diffracted beam which produces a focused line on a detector. The result is a mixed video-optical processing system that could be used for real-time quality level sorting or other automated inspection requirements.
We have developed a system which confirms the identity of an object based on its three-dimensional surface shape. The system's two key elements are a computer routine which manipulates a desired two-dimensional output pattern and a light projector which illuminates test objects with this pattern.The operation of the system is based on prior knowledge of the surface shape for the object of interest, as determined by a previously developed machine vision system. A projection pattern is chosen to be the identifying cue to the observer for that object. For example, a set of parallel lines, a circle, or the word "pass" could all be used to signify that a particular object is being examined. This pattern is then distorted by the computer in a way which is determined by the surface shape data and projection and viewing angles for the system. This new pattern is, in a sense, an encrypted form of the original pattern. Only the original object holds the key to "undistorting" this projection pattern so that it may take on its original form. Any other object placed into the system to be examined only further distorts the pattern. Thus, by examining the projected patterns on objects being inspected, an object of interest can be distinguished from others.The simplicity of this system gives it potential for inspection and security applications in which the key issue may not be the actual surface shape, but rather a quick verification of an object's or person's identity.
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