AUTOMATIC FOCUS CONTROL DEVICE AT MOVING LIMIT ON INFINITE SIDE OF LENS

摘要

PURPOSE:To avoid the anticipated overloading of a motor and driving system at the moving limit on the infinite side as far as possible by providing a limit switch at the moving limit on the infinite side and stopping the motor in a short time by monitoring the on of said switch. CONSTITUTION:A limit switch 514 which detects the arrival of a lens at the moving limit on the infinite point side of a lens and a motor is stopped when the switch 514 operates during driving of a motor while the output from an encoder is counted in accordance with the predicted value N for the extent of movement by a control circuit 6. The motor is run reverse by specified revolutions and a distance measuring circuit 2 is restarted. The automatic focusing of the lens is completed when the fresh predicted value N of the extent of the movement is within (N0+DELTAN0) slightly larger than the N0 exhibiting the permissible limit.