| 摘要 |
<p>PURPOSE:To obtain information of broad range with high accuracy, by subtracting a minimum value of a picture signal after A/D conversion from a video signal, and inputting this signal to an amplifier which uses the ratio of the difference between the maximum and minimum values of the signal to the input range of the A/D converter, as a gain set input. CONSTITUTION:A calibration start signal 11 clears a register 8, makes an output of a D/A converter 10 zero, 1 is set to a register 9 and makes the gain of a programmable gain amplifier 5 to 1. A timing circuit 12 is started with the signal 11, a transfer clock from a clock generator 2 is timed and gives an instruction of the start of conversion to an A/D converter 6 and stores all the picture elements to a computer 7. After the end of storage, a maximum value V'max and a minimum value V'min are retrieved from the data, and the V'min is set to a register 8. The ratio G of the difference between the V'max and the V'min to the input range R of the A/D converter 6 is calcurated and set to a register 9. The V'min is subtracted from a Vi to exclude background component.</p> |
