AUTOMATIC LIGHT CONTROL DEVICE

PROBLEM TO BE SOLVED: To perform the most suitable automatic lighting on/off control by correcting the products variation of an illuminance sensor such as a photo diode without using adjustment circuit. SOLUTION: When a previously set prescribed time arrives, a new zero point voltage Vzn corresponding to the illuminance zero is calculated based on the sensor voltage Vtn obtained by the output signal by the illuminance sensor 20 and the reference illuminance Lt memorized by the fixed time reference illuminance memory part 13. The correction zero point voltage Vzcn corresponding to the illuminance zero is calculated based on the new zero point voltage Vzn and a presently used zero point voltage Vzr. The voltage-illuminance characteristic is changed by making the calculated correction zero point voltage Vzcn as the new zero point sensor voltage. Subsequently, the illuminance is calculated by the voltage-illuminance characteristic. COPYRIGHT: (C)2005,JPO&NCIPI