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Analog Encoding Voltage—A Key to Ultra-Wide Dynamic Range and Low Power CMOS Image Sensor
The VLSI Systems Center, LPCAS, Ben-Gurion University, P.O.B. 653, Be'er-Sheva 84105, Israel
Department of Electrical and Computer Engineering, Bar Ilan University, Ramat Gan, 52100, Israel
Department of Electrical Engineering, University of Calgary, Alberta T2N 1N4, Canada
* Author to whom correspondence should be addressed.
Received: 22 November 2012; in revised form: 29 January 2013 / Accepted: 22 February 2013 / Published: 22 March 2013
Abstract: Usually Wide Dynamic Range (WDR) sensors that autonomously adjust their integration time to fit intra-scene illumination levels use a separate digital memory unit. This memory contains the data needed for the dynamic range. Motivated by the demands for low power and chip area reduction, we propose a different implementation of the aforementioned WDR algorithm by replacing the external digital memory with an analog in-pixel memory. This memory holds the effective integration time represented by analog encoding voltage (AEV). In addition, we present a “ranging” scheme of configuring the pixel integration time in which the effective integration time is configured at the first half of the frame. This enables a substantial simplification of the pixel control during the rest of the frame and thus allows for a significantly more remarkable DR extension. Furthermore, we present the implementation of “ranging” and AEV concepts on two different designs, which are targeted to reach five and eight decades of DR, respectively. We describe in detail the operation of both systems and provide the post-layout simulation results for the second solution. The simulations show that the second design reaches DR up to 170 dBs. We also provide a comparative analysis in terms of the number of operations per pixel required by our solution and by other widespread WDR algorithms. Based on the calculated results, we conclude that the proposed two designs, using “ranging” and AEV concepts, are attractive, since they obtain a wide dynamic range at high operation speed and low power consumption.
Keywords: CMOS; image sensor; low power; rolling shutter; snapshot; SNR; wide dynamic range
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Spivak, A.; Belenky, A.; Fish, A.; Yadid-Pecht, O. Analog Encoding Voltage—A Key to Ultra-Wide Dynamic Range and Low Power CMOS Image Sensor. J. Low Power Electron. Appl. 2013, 3, 27-53.
Spivak A, Belenky A, Fish A, Yadid-Pecht O. Analog Encoding Voltage—A Key to Ultra-Wide Dynamic Range and Low Power CMOS Image Sensor. Journal of Low Power Electronics and Applications. 2013; 3(1):27-53.
Spivak, Arthur; Belenky, Alexander; Fish, Alexander; Yadid-Pecht, Orly. 2013. "Analog Encoding Voltage—A Key to Ultra-Wide Dynamic Range and Low Power CMOS Image Sensor." J. Low Power Electron. Appl. 3, no. 1: 27-53.