A 1.5 GOPS analog CMOS array processor with integrated optical image acquisition for position encoding applications

An analog CMOS IC performs 2-D image cross-correlations to facilitate optical navigation across low contrast surfaces, such as paper. The chip includes a 25 K frames/second 34/spl times/68 active pixel photo-receiver array for capture of optical navigation reference images. Each active pixel utilizes an embedded feedback loop to maintain adequate transient response. Low spatial frequency illumination and photocell sensitivity variations are removed from the image data with local difference computation circuits as each row of image data is transferred out of the photo-receiver array. The captured images are transferred to a 32/spl times/64 array of analog signal processing cells which perform a series of nearest-neighbor 2-D cross-correlations between a previously stored image and the most recently acquired comparison image. The computation array also includes means for moving a stored reference image within the array to improve long range encoding accuracy. The correlation results are passed to an off-chip controller for translation into relative motion data.