| 摘要 |
PURPOSE:To realize an exact focusing without being influenced by a disturbance by continuing the focusing while focus voltage, which is taken out several times after the level of the focus voltage falls suddenly by more than the prescribed level, is neglected. CONSTITUTION:When, for instance, a man passes in front of a camera, the focus voltage E falls suddenly as shown by an alternate long and short dash line, and as a differential voltage DELTAE comes steeply large, a sign alters. Then, a fact that the disturbance has arisen is detected by the largeness of the level change of the differential voltage DELTAE. Namely, when the level Ln of the differential voltage DELTAE is >=six times, for instance, of the level Ln-1 of the differential voltage DELTAE, calculated just before it, it is decided that the focus voltage E is fluctuated by the disturbance. In this case, considering the influence of the disturbance to exist, the focus voltage through the several times of sampling after it, is neglected, and a focus lens is made to move as it does, by keeping the state before the disturbance arose. |
