| 摘要 |
PURPOSE:To correct automatically an image formation position shift which is characteristic to a varifocal lens by controlling automatically the correction of the image formation position shift, pertaining to the update of the overall focal length of a variable power optical system, while a variable power lens group is moved for power variation. CONSTITUTION:A focusing correction quantity arithmetic means 11b calculates the image formation position shift, pertaining to the power variation movement of the variable power lens group 2, with respective pieces of position information outputted from focusing lens group position detecting means 6 and 7 and a variable power position lens group position detecting means 8, as a correction quantity, operates estimatedly the focusing correction time which performs the focusing correction of quantity equivalent to correction by a focusing lens group 3, operates a defocusing correction quantity in consideration of the power variation movement quantity of the variable power lens group 2 during a focusing correction period, and calculates a focusing correction controlled variable by adding the correction quantity and defocusing correction quantity. A focusing correction control means 12 drives the lens group 3 to a focusing position of focal length when a focusing correction time is elapsed. |
