AUTO-FOCUSING DEVICE FOR CAMERA

摘要

PURPOSE:To improve the light emission control of a light emitting body with a simple constitution by controlling the quantity of emitted light, the number of emitted light pulses, and the light emission start time of the light emitting body at the next time according as the quantity of emitted light is larger or smaller than a target. CONSTITUTION:The pulse light from an infrared LED which passes a light emission control circuit 21 is projected to an object 13 through a projection lens 12. The reflected light is made incident on an optical position detector 15 through a light receiving lens 14. Currents IA and IB outputted from the detector 15 are converted to voltage signals VA and VB by current-voltage converters 16 and 17. These signals VA and VB are added by an adder 18, and the output is compared with a target value V0 of the quantity of reception light by a comparator 19. A microcomputer 20 sends a control signal to the control circuit 21 on a basis of the control result to control the quantity of emitted light and the number of emitted light pulses of the LED 11.