Abstract
In this paper, a wide dynamic range (WDR) CMOS image sensor (CIS) with a charge splitting gate (SG) and two storage diodes (SDs) is presented. By using single-gate on/off control with the SG, photocurrent path to the first (SD1) or second storage diodes (SD2) is switched alternatively and periodically during exposure and signal electrons generated in a photodiode (PD) are transferred to and accumulated in the SD1 or SD2. By setting a large ratio of the off-time to on-time of the SG, two different sensitivity signals, which are originated by the same photodiode, are generated and a WDR image signal is obtained. This technique has a distinct advantage on mitigating the problem of motion artifact in WDR imaging with high and low sensitivity signals and flexible dynamic control of the dynamic range. An experimental WDR CMOS image sensor with 280 (H) × 406 (V)-pixel array consisting of 14 sub-arrays, each of which have 20 (H) × 406 (V) pixels, was implemented and tested. For the SG on/off-time ratio of 30 and 279, the DR of 93 dB and 104 dB, respectively, was demonstrated. The effect of the proposed WDR imaging operation on the reduced motion artifact was experimentally confirmed.
Highlights
Wide dynamic range (WDR) image sensors are recently required for a variety of applications including security systems and automobiles
Many techniques for extending their dynamic range based on CMOS image sensor (CIS) technology have been reported [1,2,3,4,5,6,7,8,9,10,11,12]
Toward the goal for developing practically-advantageous wide dynamic range (WDR) image sensors, the WDR technique used in the designed image sensors should maintain important imaging quality factors and functions such as low noise, high sensitivity, high spatial resolution, less motion artifact, wide linear response and flexible control of the dynamic range below its attainable dynamic range
Summary
Wide dynamic range (WDR) image sensors are recently required for a variety of applications including security systems and automobiles. It requires reading long and short accumulation signals from the pixel Fundamental imaging performances such as low noise, high sensitivity and good linearity are maintained and the dynamic range control is very flexible. This paper proposes a new technique for WDR image sensors with sufficient imaging quality factors, a function of flexible control of the attainable dynamic range and mitigating the problem of motion artifact. WDR pixel has two storage diodes (SDs) for storing high and low sensitivity signals, related to short and long charge accumulations It has a charge splitting gate (SG) for switching alternatively and periodically the photo-current flow to the two SDs. It has a charge splitting gate (SG) for switching alternatively and periodically the photo-current flow to the two SDs This operation is effective for mitigating the problem of motion artifact in the reproduced WDR image.
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