Automatic focusing device for zoom lens

Abstract

Abstract PURPOSE:To reduce the effect of errors caused in a manufacturing process by setting proper correction factors to individual zoom lenses and calculating the moving quantity of a variable magnification lens group. CONSTITUTION:In case of a front focus, a correction factor alpha1 set by a potentiometer 82 is incorporated and in case of a rear focus, a correction factor alpha2 set by a potentiometer 84 is incorporated in a focus controller 78 through an analog switch 88 and an A/D converter 86, in a non-focusing state. The focusing controller 7 obtains the data of the magnification (m) and the focal distance (fe) of a variable magnification lens group from the focus (fz) of the zoom lens obtained from a zoom detection part 46 by retrieving the table of a ROM and also operates the moving quantity DELTAX of a focus lens group 2 by setting the correction factor of the magnification (m) as alpha=alpha1 or alpha=alpha2. The moving quantity DELTAX is converted into the driving current value of a DC motor 52 which drives a lens group 2 and control signals supplied to the DC motor 52 from a motor driving circuit 68 are outputted from the focusing controller 78 to the circuit 68, so that automatic focusing can be executed.

Inventors

• 👤 Kazumasa Tamada
• 👤 Mineo Kubota
• 👤 Hiroshi Saito
• 👤 Tsuneo Yokoyama
• 👤 Satoshi Mikajiri

Bibliographic Details