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Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique
Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Nakaku, Hamamatsu 432-8011, Japan
* Author to whom correspondence should be addressed.
Received: 22 September 2009; in revised form: 27 October 2009 / Accepted: 4 November 2009 / Published: 26 November 2009
Abstract: The partial charge transfer technique can expand the dynamic range of a CMOS image sensor by synthesizing two types of signal, namely the long and short accumulation time signals. However the short accumulation time signal obtained from partial transfer operation suffers of non-linearity with respect to the incident light. In this paper, an analysis of the non-linearity in partial charge transfer technique has been carried, and the relationship between dynamic range and the non-linearity is studied. The results show that the non-linearity is caused by two factors, namely the current diffusion, which has an exponential relation with the potential barrier, and the initial condition of photodiodes in which it shows that the error in the high illumination region increases as the ratio of the long to the short accumulation time raises. Moreover, the increment of the saturation level of photodiodes also increases the error in the high illumination region.
Keywords: electronic imaging; CMOS image sensor; wide dynamic range; partial charge transfer; non-linearity
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Shafie, S.; Kawahito, S.; Halin, I.A.; Hasan, W.Z.W. Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique. Sensors 2009, 9, 9452-9467.
Shafie S, Kawahito S, Halin IA, Hasan WZW. Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique. Sensors. 2009; 9(12):9452-9467.
Shafie, Suhaidi; Kawahito, Shoji; Halin, Izhal Abdul; Hasan, Wan Zuha Wan. 2009. "Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique." Sensors 9, no. 12: 9452-9467.