| 摘要 |
PURPOSE:To prevent malfunction due to noise and to make an accurate and stable focus adjustment with small power consumption by shortening the longest time of one measurement period when the movement of an optical system to an infinite distance end is detected. CONSTITUTION:When a lens barrel moves to the infinite distance end and a switch 3Q is turned on, AND gates 85 and 88 are closed and AND gates 86 and 87 are opened. Then, the output Q1 of a counter 12 and the output Qh of a counter 15 are used instead of normal outputs Qn and Qm. Therefore, the longest integral time is short when the switch 3Q is on and an integration and a light emission stop period becomes long. Consequently, such malfunction that flip-flops 91 and 92 are triggered with a noise component and the lens barrel moves is prevented and the occurrence probability of malfunction per unit time is lowered because of the prolongation of the integration and light emission stop period. Simultaneously, energy saving effect is improved more in an area close to the limit of distance measurement as a result of the shortening of the measurement time and the extension of the light emission stop. |
