CMOS Image Sensor with Dual-Sensitivity Photodiodes and Switching Circuit for Wide Dynamic Range Operation
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초록
Conventional CMOS image sensors (CISs) have a trade-off relationship between dynamic range and sensitivity. In addition, their sen- sitivity is determined by the photodiode capacitance. In this paper, CISs that consist of dual-sensitivity photodiodes in a unit pixel areproposed for achieving wide dynamic ranges. In the proposed CIS, signal charges are generated in the dual photodiodes during inte-gration, and these generated signal charges are accumulated in the floating-diffusion node. The signal charges generated in the high-sen-sitivity photodiodes are transferred to the input of the comparator through an additional source follower, and the signal voltages converted by the source follower are compared with a reference voltage in the comparator. The output voltage of the comparator deter- mines which photodiode is selected. Therefore, the proposed CIS composed of dual-sensitivity photodiodes extends the dynamic rangeaccording to the intensity of light. A 94 × 150 pixel array image sensor was designed using a conventional 0.18 µm CMOS processand its performance was simulated.
Abstract
Conventional CMOS image sensors (CISs) have a trade-off relationship between dynamic range and sensitivity. In addition, their sen- sitivity is determined by the photodiode capacitance. In this paper, CISs that consist of dual-sensitivity photodiodes in a unit pixel areproposed for achieving wide dynamic ranges. In the proposed CIS, signal charges are generated in the dual photodiodes during inte-gration, and these generated signal charges are accumulated in the floating-diffusion node. The signal charges generated in the high-sen-sitivity photodiodes are transferred to the input of the comparator through an additional source follower, and the signal voltages converted by the source follower are compared with a reference voltage in the comparator. The output voltage of the comparator deter- mines which photodiode is selected. Therefore, the proposed CIS composed of dual-sensitivity photodiodes extends the dynamic rangeaccording to the intensity of light. A 94 × 150 pixel array image sensor was designed using a conventional 0.18 µm CMOS processand its performance was simulated.
참고문헌 (15)
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