Photography – With viewfinder – Lens detail
Reexamination Certificate
2001-09-06
2002-08-27
Adams, Russell (Department: 2851)
Photography
With viewfinder
Lens detail
C396S384000
Reexamination Certificate
active
06442351
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a view finder that is used in a camera, a lens-fitted photo film unit and the like, more particularly relates to a view finder in which a frame of visual field can be observed.
2. Explanations of the Prior Arts
An Albada-type inverse Galilean view finder (hereinafter it is referred to Albada finder) has been widely used for a compact camera and a lens-fitted photo film unit for its simple structure and low cost. An Albada finder with easiest structure consists of an object lens and an eyepiece lens. The object lens is a concave lens while the eyepiece lens is a convex lens. A quadrilateral frame is formed in the front (object side) of the eyepiece lens. A half-mirror is formed in the rear (image side) of the object lens. The half-mirror of the object lens has two types: one is that the half-mirror is formed on the whole surface of the rear, while the other is formed on a part of the rear. A finder field frame showing the field of photography is displayed in the view finder. The half-mirror on the object lens and the frame line of the eyepiece lens are formed by treating metal a vacuum vapor deposition. Since the vacuum vapor deposition requires highly pure metal and takes a long time. That decreases productivity of the finder lens (object lens and eyepiece lens), resulting in cost increase.
Japanese Laid-open Patent Application No.6-301082discloses a view finder using prisms in place of the half-mirror of the object lens. This view finder has almost triangular pyramid roof-type prisms that are arranged on the periphery of the object lens and prisms of square section that are arranged in a frame on the eyepiece lens. A bright view finder frame forms the prisms is displayed in the view finder.
However, this view finder has a problem. When an eye of a photographer is off from an optical axis, light from one reflective surface gets weakened of two reflective surfaces of the roof-type prisms, because each prism formed on the periphery of the object lens takes the shape of roughly triangular pyramid. As a result, the finder field frame becomes an alternate striped pattern of light parts and dark parts.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide a view finder that does not form a stripe pattern on a finder field frame.
Another object of the present invention is to provide a view finder that is manufactured in a low cost.
To attain the above object and the other object, a view finder of the present invention includes a first reflective portion that is arranged on an eyepiece lens, and a second reflective portion that is arranged on the object lens, the second reflective portion being constituted of corner cube prisms. The corner cube prisms are integrally formed with the object lens. Further, the corner cube prisms can be used as first reflective portion, too.
According to the present invention, it is possible to obtain a bright visual field of view finder since the corner cube prisms that are arranged in a frame are used as a reflective portion of the object lens. And a bright and stable frame of visual field a finder field frame can be displayed because the finder field frame is formed by the self-reflective properties of the corner cube prism. Moreover, the view finder is integrally formed with corner cube prisms, therefore the cost of a finder lens can be manufactured at a low cost.
REFERENCES:
patent: 3602085 (1971-08-01), Wagner
patent: 5053803 (1991-10-01), Suda et al.
patent: 5475458 (1995-12-01), Arai
patent: 5640632 (1997-06-01), Koyama et al.
patent: 5664244 (1997-09-01), Yamamura et al.
patent: 5774747 (1998-06-01), Ishihara et al.
patent: 6-301082 (1994-10-01), None
Adams Russell
Nguyen Michelle
Young & Thompson
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