collinear heterodyning [kǝ`lin·ē·ǝr `hed·ǝ·rǝ´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. |