Retina for pattern matching in standard 0.6-µm complementary metal oxide semiconductor technology

We present a silicon retina fabricated in standard CMOS 0.6-µm technology. The goal of the sensor is to determine whether or not two images are similar. An image known as the reference image is first used during a programming phase to classify the pixels into two zones that correspond to, respectively, the bright and dark pixels of the reference image. Next, an image is analyzed and the values of the pixels of each zone are summed to produce two signals denoted by Sn and Sb at the outputs of the circuit. If the image under analysis is different from the reference image, then the values of these two signals will also be different from those obtained with the reference image. Our circuit thus implements a pattern matching operation that allows us to determine the similarity between two images using the Sb/Sn plane. The architecture of the sensor is described, and both the simulation and the experimental results are given. Moreover, our pattern-matching operator is compared to the normalized correlation operator commonly used in pattern matching, and its performance is discussed. Finally, we present an example of the application of the sensor.