A comparison of real-time optical correlators for pattern recognition
Abstract
Two types of optical correlators were built to investigate real time pattern recognition. The first employs 1-D devices to perform the two dimensional correlation in real time. This architecture uses an array of light emitting diodes (LED's) to input an electronically stored reference image into the processor in parallel. The input scene data is introduced into the processor one line at a time using an acousto-optic device (AOD). Multichannel time integrating correlations are performed in the row direction using the AOD and in the column direction using a charge coupled device (CCD) operating in the time delay and integrate mode. A processor was built using this technology which correlates a 64 x 44 pixel binary reference image with a 256 x 232 input scene at video rates. The second correlator is a space integrating Fourier transform based correlator. A magneto optic-device (MOD) is used at the Fourier transform plane to rapidly change filter functions. The binary nature of the MOD device necessitates using either a binary phase or binary amplitude representation of the desired complex filter function. For this reason, several types of Binary Phase-Only Filter (BPOF) representations were analyzed and experimentally investigated. Experimental correlation results were obtained using both the Hartley BPOF and a newly developed class of complex binary filters, called Quad-Phase-Only Filters (QPOF). The performance of the two systems are compared on the basis of processing speed, space bandwidth product, processor size and light efficiency. The inherent differences between incoherent and coherent processing and their implications for filter design are also discussed. Finally, estimates of future performance are presented.
- Publication:
-
Presented at the International Congress on Optical Science and Engineering
- Pub Date:
- 1989
- Bibcode:
- 1989ose..cong...24S
- Keywords:
-
- Architecture (Computers);
- Correlators;
- Image Processing;
- Pattern Recognition;
- Real Time Operation;
- Acousto-Optics;
- Charge Coupled Devices;
- Fourier Transformation;
- Light Emitting Diodes;
- Optical Data Processing;
- Optical Equipment;
- Optics