Image processing integrated circuit

Claim 1

An image processing system for detecting the presence or absence of a marking in a cell location on a document comprising: an array of photosensitive cells for sensing the presence or absence of a marking in each cell location on the document; said array of photosensitive cells producing analog signals representing levels of black or white, corresponding to the presence or absence of a marking in each cell location; processing means for processing said analog signals to produce quantized black and white video signals; said processing means including first and second parallel processing channels; said first processing channel including filter means for receiving said analog signals and for performing edge enhancement to generate a filtered output signal; said first processing channel further including comparator means for comparing said filtered output signal with a fixed reference signal level and for producing a first logic signal when said filtered output signal exceeds said fixed reference signal level; said second processing channel including means for generating a variable reference signal level representing a print contrast ratio value from the cells surrounding a cell having a marking; said second processing channel further including comparator means for comparing said analog signals with said print contrast ratio value for producing a second logic signal when said analog signals exceed said print contrast ratio value; said first and second logic signals being synchronously produced with respect to said analog signals of said photosensitive cells; and said processing means further including means for logically combining said first and second logic signals to produce a quantized black and white video signals.