ELECTRONIC CAMERA WITH AUTOMATIC BATTERY SHUTDOWN

摘要

An electronic timing circuit to be used in conjunction with photographic cameras using electronic exposure sensing and electrically actuated signal lights responsive to the exposure sensing causes automatic total electrical power shutdown if the camera is left unattended. No separate manual operation is necessary, the shutdown occurring within approximately half a minute after releasing the exposure button. Rundown of the camera battery via inadvertent failure of the operator to turn off the system is eliminated. The timer is turned on and system loads are connected in a latched state to the camera battery by partial depression of the exposure button. Adequate ambient illumination of the subject scene causes a photosensor to actuate a green signal light. Inadequate ambient illumination causes the photosensor to automatically actuate instead a red warning light and a flash tube charging circuit for a built-in flash tube, full charge being evidenced by reappearance of the green light. If the camera is pointed at a new scene of adequate ambient illumination during or after the charging process, charging stops automatically, and the flash trigger circuit is automatically disabled. An inexpensive trigger disabling circuit is disclosed. Two versions of the system are disclosed, one using bipolar comparators and capable of operation from a battery voltage of three volts, the other using CMOS comparators and requiring six volts. Both versions, in the shut-down state, place a total load of less than one microampere on the system battery, resulting in a battery life equal the shelf life if the camera is not used.