Since the seventies

laser Doppler technique for measuring velocity has a new development: wide range and high resolution as researching shock wave of solid materials. The displacement interferometer was first used as researching shock wave. But the mea-surd velocity has a practical upper limit of about 200m/sec. To widen range of the interferometer velocity interferometer was later developed and the method of high velocity measurement was found out. However

velocity interferometer has a requirement of polished surface for measurd velocity body. This limits its practical application. Solved method is to introduce Wide-Angle Michelson Interferometer so as to utilize the diffuse light reflected from natural surface of a body: This is Velocity Interferometer System for any reflector

that is VISAR. VISAR is the best typical kind of laser Doppler velocity interferometer at present and is focal point in this paper.