2 July 1999 Improved position and velocity encoder resolution using an electro-optic beam scanner
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Optical encoders are the most common means for measuring linear or rotary position. A photodetector senses the occlusion, reflection, or diffraction of light by a structure that moves linearly or rotates relative to a fixed light source. Counting the switching between `on' and `off' gives a measure of position, and velocity is determined through numerical differentiation. This paper proposes the use of an electrooptic beam scanner to improve the accuracy of the detection of both position and velocity, by scanning the light source across the moving structure and comparing the phase of the photodetector signal to the phase of the scan. The Doppler effect between the forward and backward scan can provide velocity information without numerical differentiation. A simple experiment for detecting the position of a razor edge demonstrates the concept for position.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
William C. Messner, Tuviah E. Schlesinger, Daniel D. Stancil, "Improved position and velocity encoder resolution using an electro-optic beam scanner", Proc. SPIE 3787, Optical Scanning: Design and Application, (2 July 1999); doi: 10.1117/12.351646; https://doi.org/10.1117/12.351646

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