Abstract: A viewfinder optical system has a relay optical system and an eyepiece optical system. The relay optical system has a first, a second, and a third relay lens. The eyepiece optical system has a first and a second eyepiece lens. The first eyepiece lens, which is disposed closest to a secondary-image plane formed by the relay optical system has an aspherical surface on its secondary-image plane side.

Abstract: In a lens barrel of a zoom lens, a luminous flux is divided or its path is switched so that the same luminous flux is directed to both a taking optical system and a finer optical system. Focusing and camera shake compensation are performed before division of the luminous flux or switching of its path so that images observed through a finder are already in focus and compensated for camera shakes. The lens barrel has multiple movable segments to allow the taking optical system and the finder optical system to be moved out simultaneously. To achieve zooming, a holding member for holding both a focusing lens unit and other lens units is moved so that all these lens units are moved simultaneously. Adjustment of the focusing lens unit, necessitated as a result of zooming, is achieved by moving a part of the focusing lens unit within the holding member.

Abstract: A finder display apparatus provides a display of information associated with the photographing within a finder field. The finder display apparatus has a reflecting surface, a polarizing plate and an electro-optical display device constituted by a twisted nematic liquid crystal arranged between the reflecting surface and the polarizing plate. The reflecting plate is provided to a Porro prism and has a polarization characteristic different by 90.degree. from the polarization characteristic of the polarizing plate.

Abstract: The present invention provides a variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; condenser lens group of a positive refractive power; and eyepiece lens group of a negative refractive power; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group; and wherein the optical system fulfills the following conditions;-0.09/mm<1/f.sub.1 <-0.03/mm0.04/mm<1/f.sub.2 <0.11/mm-0.1/mm<fe/(f.sub.1 .multidot.f.sub.2)<-0.035/mmwherein: f.sub.1 represents focal length of the first lens unit of the objective lens group in millimeters; f.sub.

Abstract: The present invention provides a viewfinder optical system of inverted Galilean type which has a great magnification relative to the diameter of the objective lens without increasing the number of parts. The viewfinder optical system consists of, from the object side to the eye side, an objective lens component having a negative refractive power and an eyepiece lens component having a positive refractive power. The eyepiece lens component has a convex surface at the eye side. The viewfinder optical system fulfills the following conditions:0.4L<d.sub.3 <0.85L-1.4<L/R.sub.4 <-0.8 R.sub.4 <00.35<.vertline.R.sub.2 /R.sub.4 .vertline.<0.65wherein:L represents the total length of the whole viewfinder optical system;d.sub.3 represents the axial thickness of the eyepiece lens component;R.sub.2 represents the radius of curvature of the eye side surface of the objective lens component; andR.sub.4 represents the radius of curvature of the eye side surface of the eyepiece lens component.

Abstract: An albada finder optical system of inverted Galilean type, comprising from the object side to the eye side: an objective lens component of a negative refractive power; and an eyepiece lens component of a positive refractive power having a reflecting surface at the object side.

Abstract: An improved eyepiece for a viewfinder of a single lens reflex camera is provided. This improved eyepiece includes a negative first lens element and a positive second lens element with an air space formed between the first and second lens elements. The second lens element has an aspheric surface at its object side. The configuration of the aspheric surface is a hyperboloid of revolution.