Autofocusing device

Abstract

Abstract PURPOSE:To obtain an autofocusing device which detects the front focus, the just focus, and the rear focus in an optional position without moving an image- forming lens. CONSTITUTION:A nonscanning type position sensor (PSD) 52 is arranged orthogonally to an optical axis L of an image-forming lens 3, and a sector 53 notched at 120 deg. is provided freely rotatably in front of this sensor 52. When the sector 53 is placed in a positionIwhere the sector 53 screens the lower half of the lens 3, the light passing the upper half of the lens 3 is incident to the PSD 52. When the sector 53 is placed in a position II, the light passing the lower half of the lens 3 is incident to the PSD 52. The luminous flux for the just focus, the luminous flux for the front focus, and the luminous flux for the rear focus are indicated by solid lines, dotted line, and two-dotted lines respectively in figure. A reference voltage source 55 is connected to the substrate of the PSD 52, and electrodes in both ends of a resistance layer are connected to one input terminals of operational amplifiers 56 and 57, and an AC signal corresponding to the focusing state of the lens 3 is obtained through a differential amplifier 58.

Inventors

• 👤 Saburo Numata
• 👤 沼田　三郎

Bibliographic Details