Abstract

Moving objects are optically detected with real-time processing speed by comparing two time-continuous images. In the system, bipolar-operational spatial light modulators (BSLMs)¹ are the optical key devices, which are reflective-type ferroelectric SLMs developed at NTT Opto-Electronics Laboratories. First, one input image at time t−Δt was binarized as b(t−Δt) by using the thresholding property of the BSLM1, and b(t−Δt) was kept during the time period Δt. Next, another input image at the time t was binarized as b(t) by using the BSLM2. Background image elimination can be performed by subtracting b(t−Δt) from b(t), and the Exclusive-OR (XOR) operation between them is used for the subtraction. A He–Ne laser beam incident on the BSLM2 is reflected from it and illuminated onto BSLM1. The observed light from BSLM1 is the XOR image between b(t) and b(t−Δt). All of the BSLMs are controlled by one personal computer. The time period Δt is determined only by the processing speed of the BSLMs (a few milliseconds). Therefore, moving objects faster than the TV frame rate can be detected by using this system. Experimental results and system evaluations are presented.

© 1992 Optical Society of America