A Digital Pixel Sensor Array With Programmable Dynamic Range.pdf

IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 52, NO. 12, DECEMBER 2005 2591 A Digital Pixel Sensor Array With Programmable Dynamic Range Alistair Kitchen, Student Member, IEEE, Amine Bermak, Senior Member, IEEE, and Abdesselam Bouzerdoum, Senior Member, IEEE Abstract— This paper presents a digital pixel sensor (DPS) array level of parallelism is obtained using ADCs operating at only employing a time domain analogue-to-digital conversion (ADC) tens of samples per second [3], [4]. An efficient exploitation technique featuring adaptive dynamic range and programmable of the parallelism can reduce global power consumption and pixel response. The digital pixel comprises a photodiode, a voltage comparator, and an 8-bit static memory. The conversion character- speed-up data conversion, thus increasing the frame rate of the istics of the ADC are determined by an array-based digital control imager [3], [5]. Additional benefits are also found in DPSs as circuit, which linearizes the pixel response, and sets the conversion driving a large data bus using small on-pixel buffers is avoided range. The ADC response is adapted to different lighting condi- by the use of local on-pixel data-converters. While on-pixel tions by setting a single clock frequency. Dynamic range compres- data conversion provides a number of advantages, there are still sion was also experimentally demonstrated. This clearly shows the potential of the proposed technique in overcoming the limited dy- many challenges and issues that remain to be solved. Indeed, namic range typically imposed by the number of bits in a DPS. A since