| 摘要 |
PURPOSE:To read the image output of a photodetecting element CCD at a high speed with high precision by sampling and holding the image pickup output of the CCD with plural sampling pulses and converting the sample and held signal into a digital value. CONSTITUTION:When a start command is sent from a CPU to a control part 18, the control part 18 sends a signal to a storage time control part 16 to store charges in the CCD 11 for a specific storage time. The charges stored in the CCD 11 are outputted successively, passed through a sample holding circuit 12 operated with plural sampling pulses SM, and converted by an A/D converting circuit 13 into a digital signal, which is led to a comparator 17, so that it is checked whether the maximum value is within a predetermined range or not. When the maximum value is within the range, the control part 16 sends data on the charge storage time to a logarithmic converting circuit 14 every time image data is fetched from the CCD 11, and the data is converted logarithmically together with the output data of the CCD 11 and then stored in a memory 15.
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