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1 December 1991 Linear position sensing by light exchange between two lossy waveguides
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A new version of a contactless opticl position sensor is presented. The basic sensing mechanism in both the original and the new sensors consists of injecting a light signal into a lossy optical waveguide, and detecting the attenuated guided waves at the extremities of the guide. While the original approach uses a moving point source located at the position to be sensed, the new approach utilizes a stationary, extended light source that illuminates the whole extent of the detecting waveguide. A blocking screen moves with the moving object and blocks part of the light between the source and the detector. The amount of light detected is the integral over the unblocked portion of the light coupled into and transmitted through the sensing waveguide. It is demonstrated both theoretically and experimentally that the detected light is a linear function of the position of the screen, for the case of an exponentially decaying light source with similar attenuation characteristics as those of the sensing waveguide. This approach is a lower cost version of the original approach where a logarithmic amplifier is needed for linearizing the response.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michel F. Sultan "Linear position sensing by light exchange between two lossy waveguides", Proc. SPIE 1584, Fiber Optic and Laser Sensors IX, (1 December 1991);

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