| 摘要 |
PURPOSE:To raise the probability of bringing an object into focus without increasing the content of stored data by moving a focus lens to a position which is previously set without depending on the information on a focal distance when the distance information of the object cannot be detected. CONSTITUTION:When the distance information of the object cannot be detected by a focus detection means 11, the focus lens 3 is moved to the position which is previously set from an initial position without depending on the focal distance information of a variable power lens 2. By a CPU 12, the actual extending quantity of a focus lens group 3, for example, the number of extending pulse is calculated based on zoom positional information (focal distance information) from a position detection means 8, the inverse information of the distance of the object from the detection device 11 and coefficient data from a storage means 14. Thus, an optical instrument provided with a rear focus system zoom lens whose focusing accuracy and focusing speed are excellent and which can be focused on the distant object is obtained. |
