Laser interferometer for measuring high velocities of any reflecting surface

A laser velocity interferometer instrumentation system has been developed which can measure the velocity history of either spectrally or diffusely reflecting surfaces. The system provides two interferometer fringe signals in quadrature to improve resolution and to distinguish between acceleration and deceleration. Accuracies of 2% or better are attainable for peak surface velocities of 0.2 mm/μsec or more. The system has been applied to the measurement of free surface motion in plate-impact experiments, and to the measurement of the velocity history of a projectile during its acceleration down a long gun barrel.