| 摘要 |
PURPOSE:To eliminate the influence of the sensitivity dispersion of a photoelectric converter by carrying out white level pursuit in vertical direction to the scanning direction of the photoelectric converter, and by providing a correction circuit and storage circuit to perform the level pursuit in the vertical direction. CONSTITUTION:A storage circuit 2 is provided with an address corresponding to the picture element unit of a photoelectric converter to perform level pursuit in direction vertical to scanning direction, and a value corrected by a correction circuit 4 is written to it. At first, the value of the circuit 2 is initialized to the threshold of white level, and, if the output of the photoelectric converter in a storage circuit 1 exceeds the value, the pursuit of the white level is started. At this moment, a normalization circuit 3 performs division to obtain a normalized output and supplies the normalized output to the circuit 4, which performs multiplication for obtaining a corrected value to write it in the circuit 2. Such process is carried out for every picture element of the photoelectric converter, and, as a result, the newest level of white level of each picture element is stored in the circuit 2. Namely, the reference white level independently performs the pursuit of black level for every picture element of the photoelectric converter. |
