Hardware implementation of post-retinal processing using analog VLSI

Study of nature has always given us the path to do things in a smart and efficient way. In the field of image processing we feel that the retinal vision system might provide us with some insight. The visual cortex of the mammalian brain allows compact image coding and representation. On the basis of measured receptive field profiles and spatial frequency tuning characteristics of simple cortical cells, it can be concluded that the representation of an image in the visual cortex must involve both spatial and spatial frequency variables. These localized spatial and spatial frequency filters found in the visual cortex of the mammalian brain resemble Gabor filters. The hardware implementation of such filters was reported by A. Zakaria, T. Khondker and L.A. Akers (1997). These circuits could only be tested using simulated voltage inputs corresponding to the intensity of light. We have now developed a chip with photoreceptors interfaced to these filters. The design of these filters have also been simplified to increase the fill factor of the chip