Scan control and sensor sampling system for self-scanned photosensor

Abstract

A method and system is provided for driving a self-scanned photosensor array at high sensor cell scan rates, and sampling the sensor cells serially addressed by the array without comprising either image integrity or array frame rate. End of line (EOL) and end of frame (EOF) timing signals generated by the array are sensed and operated upon to limit the voltage amplitude swings of the signals, and to reduce noise modulation in the output video signal. A single synchronization signal is formed from the timing signals to accurately identify the last cell of a frame to be scanned, and to synchronize a row counter driving one of two flip-flops providing biphase array clock signals as the flip-flops have minimal pulse skew between complementary outputs, the effects of fixed pattern odd/even noise in the output video signal are substantially reduced. Further, the flip-flops uniquely provide large voltage amplitude swings without attendant heat generation problems. The sensor cells are serially selected to a wideband, high gain, integrated circuit transresistance video amplifier which converts the recharge current of the sensor cells to a voltage waveform. The amplifier further presents an apparent low input impedance to the array at the operating frequencies, thereby accommodating the recharging of a selected sensor cell in a time period small compared to the cell scan period.