| 摘要 |
PURPOSE:To inhibit the operation for controlling focus and to prevent the wasteful operation of a focus control system by detecting the drop of at least one of the source voltages to be applied at different voltage levels to an automatic exposure control system and the focus control system down to the lower limit voltage level or below. CONSTITUTION:A detection circuit 6 for focusing direction of a semi-automatic focus control system 5 outputs a signal of a high level to an NAND gate 7 or 8 according to the focusing direction when the focus is not matched, so as to light a light emitting diode 9 or 10 for displaying the focusing direction. Said circuit puts out both diodes 9 and 10 when the focus is matched. A detection circuit 11 for the drop of source voltage in an automatic exposure control system 3 consists of two comparators 12, 13 and a negative logical AND gate 14. When either one of a battery voltage V1 and an increase voltage V2 falls down to lower limit voltage levels Vs1, Vs2 or below, the output of the gate 14 goes to a low level, thereby inhibiting the lighting of the diodes 9 and 10. |
