| 摘要 |
PURPOSE:To prevent an automatic focus detecting device from malfunctionining by starting a motor for lens driving at the start of focusing detection control and moving a lens from its start point, and inhibiting discrimination operation for focusing until the motor reaches a specific rotating speed. CONSTITUTION:A power source 1 is connected to an automatic focus circuit 3 with a changeover switch 2, a ligth emitting element 5 is activated, and reflected light from an object is photodetected 6 to output an L signal S0 until focusing is detected. A signal S1 is H and the output S7 of a NAND circuit 9 which constitutes an R-SFF is H. Transistor TRs 7, 19 and 22 turn on when the signal S7 is H to rotate the motor 23 forward. A signal from a encoder which is not shown in figure is inputted to a preliminary run section setting circuit 12 and the signal S6 is L until the motor reaches the normal rotating speed. When the motor 23 rotates forward and fucusing is obtained, the signals S5 and S6 go up to H and the signal S7 is inverted to L. One-shot multivibrator circuits 14 and 15 and an OR circuit 18 cooperate to turn off the TRs 19 and 22 and turn on TRs 20 and 1 for a specific time, braking the motor 23 electrically. Thus, malfunction is prevented and focusing precision is improved. |
