<title>Design of arbitrary projection patterns for object recognition</title>

Abstract

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.