CMOS rotation-invariant pattern recognition system

A new rotation-invariant pattern recognition system is proposed and analyzed. In this system, silicon retina cells capable of image sensing and edge extraction are used so that the system can directly process images from the real world without an extra edge detector. The rotation-invariant discrete correlation function is modified and implemented in the silicon retina structure by using the current summation. Simulation results have verified the correct function of the proposed system. Moreover, an experimental chip to implement the proposed system with 32x32 cell array has been designed and fabricated in 0.8 mu m N-well CMOS process. Experimental results have successfully shown that the system works well for the arbitrary orientation pattern recognition.