Abstract: A stabilized local oscillator frequency for heterodyne laser sensors comped of an acousto-optic crystal which provides a constant frequency offset f.sub.1, to a portion of laser transmitter power at frequency f.sub.0, for injection locking a separate local oscillator connected to a detector which simultaneously mixes f.sub.1 with the return signal f.sub.0 from a target. The detector outputs the difference frequency between f.sub.0 -f.sub.1 which is processed for the desired information. Proper local oscillator tuning is maintained through the use of a piezo-electric translator regulating the axial length of the local oscillator.