| 摘要 |
To remove, from pixel signals, dark current components, which varies with temperature, without degrading the resolution during A/D conversion. A D/A converter (11) generates a reference signal that increases from a predetermined initial signal level at a constant gradient. A comparator (12) compares a pixel signal with the reference signal. A counter (13) performs a counting in synchronization with the increase of the reference signal. A latch circuit (14) holds as a quantized value of the pixel signal. An average value calculating part (15) calculates an average value of the quantized values of the pixel signals read from a plurality of light-shielded pixels. A reference signal adjusting part (16) establishes, based on the average value, the initial signal level of the reference signal to be compared with the pixel signals read from light-receiving pixels.
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