A heterodyne detection FM-CW laser radar using a 10.6 µ Source

The feasibility of a heterodyne detection FM-CW laser radar capable of providing simultaneous range and velocity information was investigated. Linear triangular frequency modulation was accomplished with an acoustooptic modulator. Two separate optical configurations were investigated. Ranges to 2400 ± 30 yards were measured using a two-inch retro-reflector as a target, with a 7000-yard maximum predicted range. Velocities as low as .37 m/sec were easily measured, and the system was estimated to have a velocity resolution of approximately .05 m/sec. The measured receiver sensitivity was approximately 30 db below the theoretical limit. Possible causes and remedies for this reduced sensitivity are presented. An unexplained zero velocity return was observed from a moving target with the second optical configuration. A signal contamination of the local oscillator beam was also observed. Investigations of the cause of this contamination and possible explanations are presented. Simultaneous results of this project are reported in FM-CW Laser Radar at 10.6 Microns, a thesis by Lieutenant T. H. Chance [Ref. 7]http://archive.org/details/heterodynedetect00frauLieutenant, United States NavyApproved for public release; distribution is unlimited