1996 International Topical Meeting on Optical Computing, Sendai, Japan, April 21-26.
ion-implanted MQW structure is low ~ 0.1mW/cm2  and the
gratings for the high spatial frequency components in the input
image were saturated. In this case the carrier index gratings for
all the spatial frequency components have the same strength
which is equivalent to a thresholding operation on the power
spectrum. Additionally some hard clipping in the index variation
may be expected so that the device operates similar to the
thresholded and binarized JTC . Figure 3 shows the
correlation result for two identical circles of light in the input
image, the experimental result with the MQW device is shown
above the simulation result for the thresholded and binarized
We used a video-rate frame grabber card to capture the image from a CCD camera and combined this with a previously stored image using a scan converter. This was input to the SLM allowing the correlation output to be recorded as the input was changed in real time against a fixed reference image. Results will be presented showing that the system showed high discrimination between different face inputs. Figure 4 shows a result of changing facial expression in the input. The correlation output is influenced most strongly by the high spatial frequency
components in the input, i.e. its edges. A change in
facial expression still contains much of the original
edge information and a large correlation peak
results. Video input to the correlator allows
changes in the input to be tested simply, such as the
tolerance of the correlation signal to a few degrees
of rotation. We will report on the auto-correlation
and cross-correlation signals between different
The photorefractive MQW device has many advantages for a pattern matching system based on the JTC. It offers a low power and compact laser diode based system with diffraction limited resolution and high correlation rate. It has potential for high frame rate throughput for applications such as searching large data bases.
Acknowledgements. The semiconductor MQW device was grown by MBE, and the thin film layers deposited, at the Institute for Microstructural Sciences of NRC.
. A. Partovi, et. al., Appl. Phys. Lett. 62, 464 (1993). . A. Partovi, A. M. Glass, T. H. Chiu, D. T. H. Liu, Opt. Lett. 18, 906 (1993). . S. A. Boothroyd et. al. paper WJJ2, W. S. Rabinovich et. al. paper WX6, OSA annual meeting, Sept 10-15, Portland, Oregon 1995.
. A. M. Glass et. al., Opt. Lett. 15, 264 (1990). . B. Javidi, C. J. Kuo, Appl. Opts. 27, 663 (1988). . Video clips of the real-time face input tests will be available on the internet at http://alpha.ps.iit.nrc.ca.
Figure 3. Auto-correlation peaks for input of two identical circles of light. See text for details.
Figure 4. Auto- and cross-correlation peaks from the face recognition system.