Minolta Camera Kabushiki Kaisha

Minolta Camera Co., Ltd.

Masahide Tanaka

Toshinobu Ogura

Takanobu Omaki

Akiyoshi Nakamura

Mitsuo Yasukuni

The present invention is directed to a compact lens system equally operable in both air and water, comprising a first lens group having a front surface directly facing the air or water medium, the center of the curvature of the front surface being located approximately at the entrance pupil of the lens system, and a second lens group located at the image side of the first lens group with an air space formed between the first and second lens groups. The air space and design parameters being selected in the lens system so that the field curvature of the lens system is mainly changed without any substantial change in other aberrations when the air space is changed, wherein the air space is changeable by a predetermined value in response to the change between use in air and use under water for maintaining a relatively flat image surface.

Compact lens system operable in different mediums

A constant magnification zoom lens system is provided that has the capability of permitting a predetermined desired constant magnification of an image during a zoom operation. A variator lens group for varying the focal length of the lens system and a compensator lens group for controlling the position of an image formed by the lens system is provided. Pairs of cam and follower assemblies can be provided in the barrel mechanism to control the movement of the respective compensator lens group and variator lens group so that the position of an image of a fixed object is maintained within a predetermined depth of focus in a normal zooming mode of operation and also the position of an image of a moving object can be maintained within a predetermined depth of focus in response to any variation of focal length to provide a constant magnification photography mode.

Growing community of inventors

Toyonaka, Japan

Masahide Tanaka