Abstract: The present invention provides a range finding system which utilizes feedback to induce mode hopping in a standing wave generator and which determines the range, direction and velocity of an object with respect to the range finding system based on the mode hop rate. The present invention provides a novel sampling technique which prevents aliasing by modulating the standing wave generator at a frequency equal to or greater than .pi. times the frequency at which the optical path between the object and the standing wave generator is oscillating or vibrating. In order to account for Doppler effect, the standing wave interference coupling is analyzed over one period of the frequency modulation rate of the standing wave generator. A spectral analysis algorithm is implemented which determines the mode hop rate of the standing wave generator and the range, direction and velocity of the object with respect to the range finding system based on the determined mode hop rate.