| 摘要 |
PURPOSE:To hold the time necessary for focusing, i.e. follow-up characteristics excellent even when the focal length of a zoom lens is varied by varying the driving speed of an optical focusing system within a near-focusing range according to a focal length signal. CONSTITUTION:A brush 78 is fitted in a zooming operation ring 72 and a resistance body 79 is fitted at a position corresponding to the brush 78 of a fixed lens barrel 71; when the operation ring 72 is rotated for zooming, the brush 78 slides on the resistance body 79, whose detected resistance value varies. This resistance value is used as zoom ratio information, and a lens driving control circuit 67 varies the rotating speed of a motor 68 within a correlation zone according to the zoom ratio information. Namely, the rotating speed of the motor 68 is set higher and higher as the focal length is shorter and shorter, moving a focusing lens group 54 speedily. Consequently, the apparent focusing follow-up speed is made constant regardless of the focal length. |
