Patent Number: 6,253,033

Title: Eyepiece optical system for a single lens reflex camera

Abstract: An eyepiece optical system, which is used in a single lens reflex camera having a penta mirror, includes a negative first lens group, a positive second lens group, and a negative third lens group, in this order from the penta mirror; wherein the second lens group is a diopter adjustment lens group which is adjustable along the optical axis direction; and the following conditions are satisfied: wherein f.sub.1G designates the focal length of the first lens group; f.sub.2G designates the focal length of the second lens group; f.sub.3G designates the focal length of the third lens group; and f.sub.e designates the focal length of the entire eyepiece optical system when the diopter is -1.0.

Inventors: Hasushita; Sachio (Saitama, JP)

Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha

International Classification: G02B 15/177 (20060101); G02B 25/00 (20060101); G03B 13/06 (20060101); G03B 013/06 (); G02B 025/00 ()

Expiration Date: 06/26/2018