| 摘要 |
A CMOS image sensor uses a special exposure control circuit to independently adjust the photodiode exposure (integration) time for each pixel in a pixel array to obtain non-saturated photodiode charges for each pixel. Exposure time adjustment involves extrapolating a pixel's final photodiode charge using an intermediate photodiode charge measured after a predetermined portion of an exposure frame period. If the intermediate photodiode charge is, e.g., over 50% of the photodiode's full-well capacity after half of the exposure frame period, then saturation is likely and the photodiode is reset to integrate only during the remaining time. If not, then the photodiode integrates over the allotted exposure frame period. Data indicating the length of the exposure portion is stored as analog data on the memory node of each pixel, and readout of the final photodiode charge is performed using Correlated Double Sampling (CDS) techniques.
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