| 摘要 |
PURPOSE:To carry out the detection of focus with the high accuracy without any influence on the brightness of an object being photographed by controlling the light-receiving time of the photo-sensor alloy is accordance with the brightenss of the object. CONSTITUTION:The light of object from the focusing lens is received and stored by photo-sensor alloy 15 of charge store type scanned and driven by scanning pulse from the driver circuit 16. The charge resulting there-from is applied to the meter which gives the focusing lens a standard which makes the focusing lens move to the focusing position via sample hold circuit 17 and low-pass filter, etc., and also applied to comporator 28. Meanwhile reference voltage somewhat lower than the saturated level of the sensor 15 is set in the comparator 28, and the scanning- frequency of the alloy 15 is changed by the driver circuit 16 due to the inverse output of the comparator 28 via frequency change circuit 31 in which FF 29, 30, oscilator circuit 32 of predetermined frequency, and counter 33 which produces its frequency are provided. Therefore the light-receiving time of the alloy is controlled in accordance with the brightness of the object, and the focus is detected with the high accuracy without any influence on the brighteness of the object light higher than the saturated level of the alloy. |
