| 摘要 |
PURPOSE:To ensure the white balance with no error and over a considerably wide range of the intensity of the input light, by giving the control to the channel gain via the control signal which is obtained through the conversion with the ratio of the illumination light sensor output used for the logarithm ratio. CONSTITUTION:Conversion output E1 and E2 are applied to voltage comparators 11 and 12 from photoelectric conversion parts 1 and 2 possessing the spectral sensitivity characteristics which corresponds to R and G channels of each camera. On the other hand, signal E0 featuring the reduction in the exponent function way is applied to comparators 11 and 12 from exponent function signal producing part 10. Thus pulse duration modulated PWM signal of negative directional amplitude E0-E1 is obtained from comparator 11; while the positive directional PWM signal is obtained from comparator 12 each. These two signals are then supplied to AND circuit 13, and the PWM signal proportional to the value which received the logarithm conversion of the ratio between output E1 and E2 is obtained from circuit 13. This PWM signal is sent to time-voltage converting part 14 to be converted into the voltage, and then applied to gain control amplifier 15. As a result, both the R and G channel outputs of the camera can always be held constant. |
