Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a first lens and a filter.

Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a cemented lens and a positive lens component, and satisfies the following condition (1). 0.2<Dm/L<0.8??(1) where Dm is the widest of lens-to-lens spaces in the viewing optical system, and L is a distance of said viewing plane to a lens surface positioned in the viewing optical system and nearest to the eye point side.

Abstract: The present invention provides a viewfinder, characterized by comprising a reflection type display device on which an object image is displayed, an eyepiece optical system having a front group and a rear group, an illumination optical system for illuminating the reflection type display device and an optical device for putting an optical path taken by the illumination optical system over an optical path from said reflection type display device to the eyepiece optical system at a position of the widest of lens-to-lens spaces in the eyepiece optical system. The eyepiece optical system is located between the reflection type display device and an eye point, and satisfies the following condition (1): 0.1<Y/Dm<1??(1) where Dm is the widest lens-to-lens space, and Y is the length of the reflection type display device from the center to one side thereof.

Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a first lens group including a positive lens or a negative lens, a second lens group including a cemented lens in which at least one negative lens and at least one positive lens are cemented together, and a third lens group including a positive lens. Of lenses forming the first, second, and third lens groups, at least one lens surface is an aspheric surface.

Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a cemented lens in which at least one negative lens and at least one positive lens are cemented together and one positive lens, and satisfies the following condition (1). ?8<r3/f<?0.2??(1) Here r3 is the radius of curvature of the lens surface positioned in the cemented lens and nearest to the viewing plane side, and f is the focal length of the whole viewing optical system.