Camera electronic flash appts. - has light intensity monitor and comparison circuit for reflected light to operate warning signal

摘要

The electron flash equipment includes a system of measuring the light reflected back from the subject so as to operate a visual or audible warning signal when the distance between the flash equipment and the subject is less than a required minimum distance. The slope of the flank of the reflected light is measured and compared with a predetermined flank angle to obtain the warning signal.4 The control circuit includes a light measuring section (2) and a timing stage (1). The measuring stage is connected to the positive input of a comparator (3) with a reference voltage applied to its negative input. Its output is connected to an AND gate (4) with its outer input connected to the output of the timing stage. The output of the gate is connected to the warning device (8). The measuring stage integrates a signal corresponding to the light intensity, and delivers it to the comparator.