Compensation for Process and Temperature Dependency in a CMOS Image Sensor
Shuang Xie (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Albert Theuwissen (TU Delft - Electrical Engineering, Mathematics and Computer Science, Harvest Imaging)
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Abstract
This paper analyzes and compensates for process and temperature dependency among a (Complementary Metal Oxide Semiconductor) CMOS image sensor (CIS) array. Both the analysis and compensation are supported with experimental results on the CIS’s dark current, dark signal non-uniformity (DSNU), and conversion gain (CG). To model and to compensate for process variations, process sensors based on pixel source follower (SF)’s transconductance g m,SF have been proposed to model and to be compared against the measurement results of SF gain A SF . In addition, A SF ’s thermal dependency has been analyzed in detail. To provide thermal information required for temperature compensation, six scattered bipolar junction transistor (BJT)-based temperature sensors replace six image pixels inside the array. They are measured to have an untrimmed inaccuracy within ±0.5 ⁰C. Dark signal and CG’s thermal dependencies are compensated using the on-chip temperature sensors by at least 79% and 87%, respectively.
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