| 摘要 |
PURPOSE:To always control the exposure to a correct value by controlling the exposure so that the output signal of an image sensor is within the range between maximum and minimum values and multiplying the contrast signal, which is obtained in accordance with the variation of this exposure, by a correction coefficient to correct the exposure. CONSTITUTION:A CPU 76 commands the driving pulse frequency (f) of a CCD driver 64 to start scanning of a line sensor 56. The maximum value (M) and the minimum value (m) of an output signal V are preliminarily set within such range by setters 92 and 94 that the linearity of the output signal V of the line sensor 56 can be obtained. In case of V(m)<V<V(M), a contrast signal C stored in a peak holding circuit 70 is read into the CPU 76 and is stored as (C,X) in a RAM 80 together with the position X of a projection lens 20 in this time. The position X of the projection lens 20 where the contrast signal C is maximum is obtained. When the exposure is changed, the projection lens 20 is moved simultaneously with the correction of the contrast signal C to obtain the lens position, and it is determined as the in-focus position. |
