Patent ID: 8195421

Claim:
A method of determining the velocity and direction at micron or sub micron scale of a moving object comprising the steps of: generating an incident beam of coherent light, wherein the incident light beam comprises a pair of beams of coherent light, one beam being polarized with respect to the other beam, the pair of beams being caused to converge at a point through which the moving object passes; receiving reflected light reflected from a moving object passing through the incident light beam and forming from the reflected light a magnified image of the moving object; projecting the magnified image through a first optical mask having a first region of alternating opaque and non-opaque areas having a first spacing and second region of alternating opaque and non-opaque areas having a second spacing different from the first spacing; detecting the light signal transmitted through the optical mask, the light signal comprising a series of pulses, and calculating the velocity and direction of the moving object as a function of frequency of the signal and the first and second spacing of the opaque areas.