| 摘要 |
The semiconductor device includes a plurality of photosensors arranged in matrix. The photosensors each include a photoelectric conversion element and an amplifier circuit. A backlight is turned on, an object to be detected is irradiated with light, and the photosensor in a p-th row performs the reset operation and the storage operation. After that, the backlight is turned off, and the photosensor in a (p+1)th row performs the reset operation and the storage operation. Then, the photosensors in all the rows sequentially perform the selection operation. A difference between output signals obtained from the photosensors in adjacent rows is obtained. Using the difference, a captured image of the object is generated and a region where the object exists is detected. The amplifier circuit includes a transistor for holding stored electric charge, in which a channel is formed in an oxide semiconductor layer.
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