collinear heterodyning

collinear heterodyning

[kə′lin·ē·ər ′hed·ə·rə‚dīn·iŋ]
(electronics)
An optical processing system in which the correlation function is developed from an ultrasonic light modulator; the output signal is derived from a reference beam in such a way that the two beams are collinear until they enter the detection aperture; variations in optical path length then modulate the phase of both signal and reference beams simultaneously, and phase differences cancel out in the heterodyning process.