A digital pixel image sensor for real-time readout

An experimental digital image sensor that converts analog video signals int o 8-bit digital signals for each unit pixel, and reads out the signals at a n operating clock of standard TV has been de, eloped. Each pixel is equippe d with a photodiode, a 1-bit analog-to-digital converter (1-bit ADC), an 8- bit pulse counter, and a signal processing circuit, The sensor system displ ays a two-dimensional (2-D) image in real time. The 1-bit ADC has a dynamic range of 110 dB at an operating voltage of 1.3 V. "Knee" characteristics a nd the results of an investigation into random noise sources in the circuit are also described.