Frame-rate displacement measurement system utilizing an ultra-high-speed shutter camera and an optical correlator

Abstract

A particle image velocimetry (PIV) system has been proposed for real-time (frame-rate) measurement and is composed of an ultra-high-speed shutter camera and an optical correlator. The ultra-high-speed shutter camera employed in this system has several functions such as optical amplification, high-speed shuttering and multishuttering for forming a double-exposure pattern of a moving object, in order to observe dimmer and high-speed phenomena. The optical correlator used in this system is a joint transform correlator (JTC) using two PAL-SLM's, which are optically addressed spatial light modulators with phase-only modulating function. By utilizing the optical correlator, a real-time fringe analysis of the double-exposure pattern was achieved. It is demonstrated that the system can measure velocity of random-dot patterns on a side of rotating disk with frame-rate response and good linearity at the rate of 10 m/s. We have studied an imaging condition such as ratio between exposure time and repetition time of double-exposure for suitable measurement. Also evaluated is effect of ion-feedback noise caused by an image intensifier in the ultra-high-speed shutter camera. The performance of the system is shown and discussed from a viewpoint of practical measurements. >