Finder optical system for a single-lens reflex camera

Details Finder optical system for a single-lens reflex camera Finder optical system for a single-lens reflex camera

2008-06-18

2009-06-02

Perkey, W. B. (Department: 2862)

Photography

With viewfinder

With reflector

C396S382000, C396S084000, C396S148000, C396S373000, C396S378000, C359S643000, C359S644000, C359S771000, C359S772000, C359S773000

Reexamination Certificate

active

07542670

ABSTRACT:
An eyepiece includes, in order from the object side, a first lens with positive power, a second lens with positive power, and a third lens with negative power. The first lens is a positive meniscus lens with a convex surface facing the object side, and the eyepiece fails to have a fourth lens. The eyepiece satisfies the following conditions:in-line-formulae description="In-line Formulae" end="lead"?0.6<f1/f<1.2in-line-formulae description="In-line Formulae" end="tail"?in-line-formulae description="In-line Formulae" end="lead"?−2.0<f1-2/f3<−1.0in-line-formulae description="In-line Formulae" end="tail"?in-line-formulae description="In-line Formulae" end="lead"?−0.45<f3/f<−0.25in-line-formulae description="In-line Formulae" end="tail"?where f1 is the focal length of the first lens; f1-2 is a combined focal length of the first and second lenses and is a focal length where a diopter is −1 m−1when the focal length of the eyepiece is changed; f3 is the focal length of the third lens; and f is the focal length of the entire system of the eyepiece and is a focal length where a diopter is −1 m−1when the focal length of the eyepiece is changed.

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