Real-time displacement measurement using a pattern correlation system incorporating an ultra-high-speed shutter camera and parallel aligned nematic liquid crystal spatial light modulators (PAL-SLMs)

PIV (Particle Image Velocimetry) system has been composed of an ultra-high-speed shutter camera and optical correlator for real-time (frame-rate) operation. The ultra-high-speed shutter camera has several functions such as optical amplification (typically ×10⁴), high speed shuttering (100 nsec-1 msec), and multi-shuttering (1, 2, 4, and 8 times) for forming a double-exposure pattern of an object image, in order to measure the displacement of the flow. The optical correlator is a joint transform correlator (JTC) using two PAL-SLMs, which are optically addressed spatial light modulators with phase only modulating function, for real-time analysis of the double-exposure pattern. It is demonstrated that the system can measure velocity of a random-dot pattern on a side of a rotating disk with frame-rate response. The performance of the system is shown and discussed