| 摘要 |
PURPOSE:To improve S/N and the accuracy by executing pseudo read processing at a timing corresponding to the quantity of light without saturating an accumulative type image sensor. CONSTITUTION:Light radiated from a light source 1 reflects at the surface 2 of an original, and is converged by an optical system lens 3, and an image is formed on the accumulative type image sensor 4. A photoelectric conventing means 5 drives the sensor 4, and simultaneously quantize its output and outputs it to an external section. A light quantity detection means 6 detects at all time the light-quantity from the light source 1, and according to the result of this detection, a charge sweeping means 7 determines at which one of the plural times of reading timings preliminarily set within one time read scanning period is the pseudo read processing to be executed in order not to saturate the sensor, and outputs the timing signal of the pseudo read processing to the means 5. Accordingly, the exposure time of the sensor 4 is relatively shortened, hence it does not go to a saturated status. As a result, an output in sufficient dynamic range can be obtained, and the S/N and the accuracy can be improved.
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