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A CMOS image sensor with pixel level analog to digital conversion is presented. Each 13.8×13.8 μm2 pixel area contains a photodiode and a dynamic comparator using the maximum voltage swing available (0 V-1.8 V). The comparator does not need any bias current, is insensitive to fabrication process variations and the number of quantification levels provided could be programmed. A new method for scanning the columns of the pixel array is presented. Implemented with a self-timed circuit, it provides a faster readout while consuming less power. The system allows image captures at multiple exposure times, and the resulting values are delivered in floating digital format, offering the possibility to expand the intrascene dynamic range to more than 96 dB. The circuit was implemented in a CMOS 0.18 μm process.
Electrical and Computer Engineering, 2003. IEEE CCECE 2003. Canadian Conference on (Volume:1 )
Date of Conference: 4-7 May 2003