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6 October 1986 An Amplitude Modulated Laser System For Distance And Displacement Measurement
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A laser distance and displacement measurement system is being developed to monitor small displacements in large space structures for strain analysis and structural control. The laser is amplitude modulated at a variable frequency by a voltage controlled oscillator which also serves as a reference oscillator in a mixer. The reflected laser beam is focused on a detector and the detected signal is mixed with the reference. The dc error voltage from the mixer is maintained at null by shifting the modulating frequency. Small displacements are indicated by a change in modulation frequency which is adjusted to maintain quadrature between the received signal and the reference signal from the voltage controlled oscillator in a phase-locked-loop. Measurement of absolute distance is accomplished by sweeping the modulation frequency from a quadrature lock point to an adjacent lock point. A breadboard system has been tested with a laser diode and a resolution of a few ppm has been demonstrated.
© (1986) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Robert S Rogowski, Joseph S Heyman, and Milford S. Holben Jr. "An Amplitude Modulated Laser System For Distance And Displacement Measurement", Proc. SPIE 0663, Laser Radar Technology and Applications I, (6 October 1986);


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