Optical: systems and elements – Lens – Eyepiece
Patent
1995-09-28
1998-05-05
Nelms, David C.
Optical: systems and elements
Lens
Eyepiece
359687, 359646, G02B 1514, G02B 2500, G02B 300
Patent
active
057483817
ABSTRACT:
A real image type zoom finder optical system is constructed by an objective optical system, an erect orthoscopic optical system and an eyepiece optical system sequentially arranged from an object side. The objective optical system is composed of first to fourth lens groups each constructed by a single lens. The erect orthoscopic image optical system is composed of two erect prisms. The eyepiece optical system is composed of one lens group. A front face of the second lens group is constructed by an aspherical surface such that the first, second, third and fourth lens groups respectively have positive, negative, positive and positive refracting powers. A real image formed by the objective optical system is focused and formed within the erect orthoscopic image optical system. A zooming operation is performed by moving the second lens group from the object side to an eyepiece side on an optical axis of the finder optical system. A change in diopter of a finder caused by this zooming operation is corrected by an axial movement of the fourth lens group.
REFERENCES:
patent: 5136427 (1992-08-01), Sugawara
patent: 5193030 (1993-03-01), Nozaki et al.
patent: 5448400 (1995-09-01), Kikuchi et al.
patent: 5489965 (1996-02-01), Mukai et al.
Cornely John P.
Nelms David C.
Ricoh & Company, Ltd.
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