| 摘要 |
PURPOSE:To make it possible to read an image at high accuracy using a simple constitution by providing two transmitting and reading systems, one for image data measuring and another for dynamic range measuring, and switching selectively the quantity of beam or the sensitivity of reading of the transmitting and the reading system for picture data measuring from the dynamic range of a signal read beforehand by the transmitting and reading system for dynamic range measuring. CONSTITUTION:A signal from a pre-amplifier 10b for picture data measuring is digitalized by an A/D convertor 1b and sent to a gain correcting circuit 16, and gain-corrected to become similar signal value to the value obtained by amplifying the output signal of a photodetector 9b by above-mentioned pre- amplifier 10b by a common gain. For instance, the pre-amplifier 10b is gain-set to read by gain G2 when the level of the signal for dynamic range measuring is between L1 and L2, by gain G3 when the level is <=L2 and by gain G1 when the level is >=L1. The calculation of the value of gain for setting gain is made by a gain calculating circuit 12, and the result is stored in a memory 13, and final gain correction is made by the stored gain value. |
