PURPOSE: To execute an arithmetic conversion of a high luminance of an image sensor output, and to obtain a good image signal extending over a wide dynamic range, by setting an average value of every picture element of a dark current at the time of light-shielding of the image sensor, as a reference voltage value of a logarithmic conversion.
CONSTITUTION: First of all, an image sensor IS is set to a light-shielding state, a dark current signal of an effective photosensitive picture element is read out plural times by a sensor driving controlling circuit DV and AD/converted by an ADC converter, and based on an obtained digital dark current signal, an average value of a dark current is calculated digitally at every picture element by an arithmetic circuit CPU, dark current information of every picture element of this result of operation is DA/converted by a DA converter DAC, and this converted data inputted as reference voltage information to a non- inversion input side of a logarithmic conversion use operational amplifier OP2. In such a way, even if a dark current of the sensor IS is uneven, the corresponding dark current can be set, and a logarithmic conversion output having a high accuracy can be obtained. Also, an influence of random noise of the sensor IS can be lowered remarkably.
SATO YUICHI
HIRAMATSU AKIRA
KATSUMA MAKOTO
YAMADA SHIGEKI
KOBAYASHI TAKESHI
| JPS60189372A | 1985-09-26 | |||
| JP55124868B |