| 摘要 |
PROBLEM TO BE SOLVED: To realize a small electric power consumption and restraint of a quantization noise when a high gain is required. SOLUTION: An analog signal from a sensor 2 is amplified by an AGC circuit 3, amplified by an AGC circuit 5 and processed by a signal processing circuit 6, after converted into a digital signal by an A/D converter 4. A level of an output brightness signal Y of the signal processing circuit 6 is detected in a level detection circuit 9. A microcomputer 7 compares the detection value with a reference value, and in response to the result, generates an aperture control signal of an iris 1, a gain control signal 73 of the AGC circuit 3 and a gain control signal 75 of an AGC 5. At a low degree of illumination, gains of AGC circuits 3 and 5 are made into minimum, and a detection value is made matched to a reference value by controlling amount of the aperture of the iris 1. At a medium degree of illumination, the iris 1 is fully opened, a gain of the AGC circuit 5 is made into minimum, and the detection value is made matched to the reference value by a gain control of the AGC circuit 3. At a high degree of illumination, the iris 1 is opened fully, the gain of the AGC circuit 3 is made into maximum, and the detection value is made matched to the reference value by a gain control of the AGC circuit 5. COPYRIGHT: (C)2004,JPO&NCIPI
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