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16 June 1995 Topographical analysis with time-modulated structured light
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We present a range-finding method for determining surface topography by using time modulated structured light illumination. By illuminating a surface with a time-modulated light structure of several transmitters and triangulating relflected light onto a single point receiver, we are able to determine the surface height at a point by determining which light source intersects the surface at that point. In essence, the surface height acts to multiplex the projected signals onto the receiver. We increase the system resolution beyond the number of light sources by overlapping the image intensity of the light sources. The resulting signature allows for sub-pixel resolution. Time modulating the structurted light allows for demodulation with a high signal-to-noise ratio without the use of high intensity light sources thereby reducing system cost and complexity. This method of topographical analysis can be scaled to high end systems capable of real-time, high-resolution imaging. In addition to system geometry and resolution capacity, we discuss the advantages and disadvantages of various modulation and coding schemes that can be applied to this approach.
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Raymond C. Daley, Laurence G. Hassebrook, Stanley C. Tungate Jr., John M. Jones, Hadley T. Reisig, Timothy A. Reed, Bryan K. Williams, Jerry S. Daugherty, and Mark Bond "Topographical analysis with time-modulated structured light", Proc. SPIE 2488, Visual Information Processing IV, (16 June 1995);

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