| 摘要 |
PURPOSE:To improve the operability by controlling the speed of power varying operation in a power variation area to an almost constant speed wherever in a focusing area the focusing position of a group of focusing lenses is. CONSTITUTION:Wherever in the focusing area the focusing position is, the speed of the power varying operation in the power variation area is controlled to the almost constant speed to correct a position shift in image formation position due to the update of the overall focal length automatically. Therefore, although a vari-focal lens which is an inexpensive, small-sized, and simple optical system is used, the image formation shift characteristic to the group of vari-focal lenses when the overall focal length is varied from 1st optical focal length to 2nd focal length between the shortest focal length and longest focal length after the group of focusing lenses is placed in focusing operation temporarily can be corrected automatically. Consequently, the power varying operation is performed at a uniform operation speed and a lens controller superior in operability is obtained. |
