| 摘要 |
PURPOSE:To shorten the scanning time of a scanning mirror to reduce the rotative quantity of a focus ring of an object lens, by making the driving speed of the scanning mirror higher than a corresponding driving speed of the focus ring in the range near the closest distance-side end and the infinity distance- side end. CONSTITUTION:Inclinations of parts 3a and 3b of a cam 3 beyond positions of the cam 3 which correspond to a distance, for example, 1.3m near the closest distance-side end and a distance, for example, 5m near the infinity distance-side end of an object lens 1 are made sharp; and though the focus ring and a scanning mirror 5 are operated in the range of 1.3-5m in a speed ratio where a focus curve F2 of the focus ring and a scanning curve M2 of the scanning mirror 5 correspond to each other accurately, the scanning mirror 5 is scanned up to a target distance in the distance closer than 1.3m more quickly than the object lens 1 is operated up to the target distance actually, and the presence or the absence of a desired object is detected, and the scanning mirror 5 is stopped before the object lens 1 is operated up to the object distance when the scanning mirror acquires the object. |
