Abstract

An apparatus is provided for use in optically determining distance and velocity relating to an object. The apparatus includes an optical radiation source that emits a first optical radiation signal of a modulating amplitude. The amplitude modulation of the first optical radiation signal is swept over a predetermined frequency range in a predetermined time period. Common optical components are employed to direct the first optical radiation signal towards the object, and to receive a portion of the first optical radiation signal that reflects off of the object. A portion of the first optical radiation signal is internally reflected by one of the common optical components to obtain a second optical radiation signal. An optical heterodyne detector optically mixes the received first and second optical radiation signals to produce an electrical output signal. The frequency of the electrical output signal is measured, and the frequency measurements are used to determine first and second frequency components. The first frequency component and the aforementioned predetermined frequency sweep time period are used to determine the distance of the object relative to the apparatus, and the second frequency component, which represents a Doppler shift, is employed to determine the velocity of the object.

Other References

• Hulme, Collins, Constant, Pinson; "A CO₂ Laser Rangefinder Using Heterodyne Detection and Chirp Pulse Compression"; Opt. Quantum Electronics (1981)