Velocity interferometer for any reflector with variable sensitivity range and time resolution

Abstract

The present disclosure relates to a velocity interferometer. The interferometer described herein, comprises of two optical cells, one partially containing a liquid. The light entering the interferometer is amplitude split and made to propagate through the two cells in such a way that the apparent path lengths of the beams are equal, thereby fulfilling the condition necessary for obtaining single wide fringe in the interference pattern of the two beams. However, due to difference in the physical path traversed by the two beams, a finite delay time exists between them. The two beams, after reflection from end-mirrors or cube corner prisms in the two cells are recombined to form interference fringe patterns on active areas of multiple detectors. Doppler shifted light resulting from reflection of light from a moving projectile generate fringe shifts on the detector planes thereby producing voltage signals proportional to instantaneous velocity of fast moving projectile. The voltage signals are recorded with multi-channel digital oscilloscope and processed in a processor/controller of a computing unit to obtain velocity time history of the projectile. Controlled motion of the cube corner reflectors placed at the ends of two cells using stepper motors and piezoelectric actuators ensures that the time delay between the interfering beams is controlled accurately thereby changing the sensitivity range and time resolution of the velocity measurements.