The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 29, 1997
Filed:
Feb. 21, 1995
Masamitsu Ozawa, Kanagawa-ken, JP;
Nikon Corporation, Tokyo, JP;
Abstract
A focus state detection device includes focus state detection optical systems having focus state detection regions off the optical axis of the object lens (in the lateral areas of the field) that extend in a radial direction relative to the optical axis of the shooting lens. In each focus state detection optical system, images from the object lens are composed into secondary images on a pair of rows of photosensitive elements, and the focussing state of the object lens is detected from the positional relationship between these secondary images. The focus state detection optical systems have a first focus state detection region located on the optical axis of the predicted focussing plane of the object lens, and a second focus state detection region located off the optical axis of the predicted focussing plane and along a radial direction relative to the optical axis. The distance between outer edges of the pair of apertures of the diaphragm mask corresponding to the second focus state detection region is established so as to be smaller than the distance between outer edges of the pair of apertures of the diaphragm mask corresponding to the first focus state detection region. Such structure provides a focus state detection device having a high degree of focus state detection precision without the problems of eclipsing of focus state detection light rays caused by exit pupils of the shooting lens.