| 摘要 |
PURPOSE:To enable to enlarge the dynamic range of the image signal and to eliminate the deficit of information as well, by analogically processing the corrective operation by a method wherein the background processing, the illuminance unevenness and so forth are judged by the CPU and are removed for a correction value by an analog operation processing from the image signal. CONSTITUTION:An image signal A passes a DC fixed circuit 41 and a voltage clamping circuit 42, passing through an arithmetic unit 21 and an analog multiplier 22, is converted into a digital siganl by an A/D converter 43 and taken in a frame memory 44. Then signals other than the patterns to be measured, such as the illumination unevenness and the background, are extracted; and the image signal is written in an internal memory 26 in a correcting circuit 25 as an average level signal. At the same time, the maxium value in the screen is extracted by a peak holder circuit 27 in the correcting circuit 25 and the maximum value is temporarily stored in an internal memory 28 in the correcting circuit 25. The image signal A is optimally amplified in accordance with the full scale of the A/D converter 43 after removing the unnecessary bias component thereof and before the image signal is converted into a digital signal. The corrective operation of the patterns to be metered, such as the illumination unevenness and the background, is analogically processed. As a result, the deficit of the information is substantially not caused. |
