The output of an optical correlator is sensitive to rotations of the input object. However, the correlator cannot distinguish the direction of this rotation (clockwise or counterclockwise). We introduce a rotation-ally sensitive multiplexed filter that senses both the direction and amount of rotation of the input object without employing iterative filter techniques. Our filter simultaneously forms three correlation outputs at three different spatial locations. Each output represents the correlation of the input object with a different rotated version of the reference object. Comparison of the three correlation outputs enables the direction and amount of rotation to be determined. This approach is insensitive to changes in the input object intensity because the various correlation peaks are formed simultaneously. Experimental results show an angular sensitivity of less than 0.5 deg. # 1998 Society of Photo-Optical Instrumentation Engineers.S0091-3286(98)00401-2 Subject terms: recognition techniques; alignment; correlators; filters; pattern recognition. Paper ART-108 received May 27, 1997; revised manuscript received Aug. 11, 1997; accepted for publication Aug. 11, 1997.
展开▼
