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January 2011


Comp-lementary metal oxide semiconductors, Charge coupled devices


We present an analysis of dark current from a complementary metal?oxide?semiconductor (CMOS) active pixels sensor with global shutter. The presence of two sources of dark current, one within the collection area of the pixel and another within the sense node, present complications to correction of the dark current. The two sources are shown to generate unique and characteristic dark current behavior with respect to varying exposure time, temperature, and/or frame rate. In particular, a pixel with storage time in the sense node will show a dark current dependence on frame rate and the appearance of being a ?stuck pixel? with values independent of exposure time. On the other hand, a pixel with an impurity located within the collection area will show no frame rate dependence, but rather a linear dependence on exposure time. A method of computing dark frames based on past dark current behavior of the sensor is presented and shown to intrinsically compensate for the two different and unique sources. In addition, dark frames requiring subtraction of negative values, arising from the option to modify the bias offset, are shown to be appropriate and possible using the computational method.


Copyright 2011 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

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