| 摘要 |
PURPOSE:To allow a focus to follow automatically distances from a long distance to a short distance or from a short distance to a long distance, by providing a means which sets variably the focusing speed of a photographic optical system. CONSTITUTION:When a positive voltage is inputted from a speed setting means 3 consisting of resistances 4 and 6, a variable resistance 5 and an operational amplifier 7 by a focus detection signal from a signal processing circuit 2 for auto-focus, a servo motor 8 moves a photographic lens 10 to the long-distance side through a driving mechanism 9. If an object which is in focus in a short distance is moved rapidly to the long-distance side, a lens 10 responds to it quickly to move to the long-distance side and is focused on the object. Consequently, the lens is focused on an object different from the current object in a preliminarily set auto-focusing speed to realize artistic photography, and photography on a stable screen is possible without the hindrance due to a car or the like which transverses the front of the object. |
