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Proceedings Paper

An Amplitude Modulated Laser System For Distance And Displacement Measurement
Author(s): Robert S Rogowski; Joseph S Heyman; Milford S. Holben Jr.
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Paper Abstract

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.

Paper Details

Date Published: 6 October 1986
PDF: 4 pages
Proc. SPIE 0663, Laser Radar Technology and Applications I, (6 October 1986); doi: 10.1117/12.938659
Show Author Affiliations
Robert S Rogowski, NASA Langley Research Center (United States)
Joseph S Heyman, NASA Langley Research Center (United States)
Milford S. Holben Jr., PRC Kentron (United States)

Published in SPIE Proceedings Vol. 0663:
Laser Radar Technology and Applications I
James M. Cruickshank; Robert C. Harney, Editor(s)

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