| 摘要 |
PURPOSE:To judge whether the subject is of the luminance suited for automatic focusing operation or not by comparing the change rate of the absolute value of the detected two signals difference for distance measurement with a set value and judging the suitability of the luminance. CONSTITUTION:The two detection signals for focusing detected by two sets of photoelectric transducers 7, 8 is applied via difference detecting circuit to an absolute value circuit 11. The differential absolute value is differentiated by a differentiating circuit 12 and the change rate of the differential absoulte value voltage with time is compared with a set voltage in a voltage comparator 12. When the subject luminance is above the specified value and the differentiated output of the absolute value difference is more than the set value, an FF17 is set by the comparing output of the circuit 15, by which an FF18 is set. While the subject luminance is high, a display lamp 22 is lighted by the high level set output of the FF18. When the subject luminance is low, the low level output of the FF18 lights a warning indicator lamp 21 to warn that the subject luminance is inadequate for automatic focusing operation. Hence, the operation of automatic focusing, etc. of large errors by the low luminance subject may be stopped. |
