Image pickup apparatus and method for controlling the exposure time of the image pickup apparatus

摘要

This is a division out of EP-(A)- 0 393 401. The figure shows a block diagram of a video camera in which automatic exposure (AE) functions can be attained such as "Iris Priority AE Mode" (light quantity controlled by the shutter speed) and "Shutter Priority AE Mode" (light quantity controlled by the iris). The video camera includes a circuit (12) for providing a voltage corresponding to a current value of the iris, a circuit (16, 19, 20) for generating a voltage corresponding to a desired iris value, a circuit (18) for comparing the two voltages, and a circuit (7) for controlling the iris based on the result of the comparison so as to keep the iris at the desired value. The output signal of the image pickup device (1) is amplified (2) and the signal quantity is determined (4) before it is compared (17) with a reference voltage (5). The output of the comparator (17) is connected to the circuit (16) setting the desired iris value, and is also connected to an exposure time changing circuit (21) which controls the exposure time to be established by the image pickup driver (22). This driver (22) serves to change signal sweep-out timing in increments/decrements of one horizontal scanning period (1H) to set the exposure start time. The exposure end time is changeable in increments/decrements of shorter than 1H (fine tuning < 1H ) so that the exposure time can be selected in an increment/decrement finer than 1H. <IMAGE>