A wide-angle variable magnification viewfinder comprises from an object side: an objective lens group of a positive refractive power, including a fixed first lens unit of a negative refractive power, a movable second lens unit of a negative refractive power for compensating the change of a view angle, a movable third lens unit of a positive refractive power for changing the magnification of the optical system, a prism for erecting an image, a fixed fourth lens unit of a positive refractive power; and an eyepiece lens group of a positive refractive power; wherein the objective lens group forms an actual image of an object and the actual image can be observed through the eyepiece lens group; and wherein -1.20<L.sub.t /f.sub.1 <-0.75, 0.04<m2w.times.m2.sub.t <0.13; where f.sub.1 represents a focal length of the first lens unit of the objective lens group, L.sub.t represents a distance from the first lens surface of the objective group to a focal point of the objective lens group, m2w represents the magnification of the second lens unit of the objective lens group at a wide-angle position, and m2.sub.T represents a magnification of the second lens unit of the objective lens group at a telephoto position.
A real image type finder optical system is provided with an objective optical system having a positive power, an erecting optical system for erecting a real image formed by the objective optical system and an eyepiece optical system for observing the real image formed by the objective optical system and erected by the erecting optical system. An information display surface provided in the eyepiece optical system, the information display surface displaying information to be observed in a field of view of the finder optical system. A partial mirror surface is provided within the eyepiece optical system, on an object side with respect to the information display surface. The partial mirror surface allows a part of light incident from the object to pass therethrough, and reflects light incident from the information display surface towards the eye side.
A real image mode variable magnification finder has an objective optical system with positive refracting power, an image erecting optical system, and an ocular optical system with positive refracting power. The objective optical system has a first lens unit with negative refracting power, a second lens unit with negative refracting power, a third lens unit with positive refracting power, and a fourth lens unit with negative refracting power. When the magnification of the finder is changed, a plurality of lens units including the third lens unit are moved. In this way, the total length of the objective optical system can be reduced, and thus a compact finder is obtained.
A real image mode variable magnification finder has an objective optical system with positive refracting power, an image erecting optical system, and an ocular optical system with positive refracting power. The objective optical system has a first lens unit with negative refracting power, a second lens unit with negative refracting power, a third lens unit with positive refracting power, and a fourth lens unit with negative refracting power. When the magnification of the finder is changed, at least one lens unit, namely the third lens unit is moved. In this way, the total length of the objective optical system can be reduced, and thus a compact finder is obtained.
A real image mode variable magnification finder has an objective optical system with positive refracting power, an image erecting optical system, and an ocular optical system with positive refracting power. The objective optical system has a first lens unit with negative refracting power, a second lens unit with negative refracting power, a third lens unit with positive refracting power, and a fourth lens unit with negative refracting power. When the magnification of the finder is changed, at least one lens unit, namely the third lens unit is moved. In this way, the total length of the objective optical system can be reduced, and thus a compact finder is obtained.
The present invention relates to a variable magnification finder comprising an objective lens group having a positive refractive power for enabling a wide angle view of an object. The objective lens group includes a first lens sub-group having either a negative or a positive refractive power; a second lens sub-group having a negative refractive power; a third lens sub-group having a positive refractive power and having a cemented lens with at least two pieces; and a fourth lens sub-group having a positive refractive power. The third lens sub-group is movable for magnifying the image, and the second lens sub-group is movable for compensating the focus of the magnified image. The finder further comprises an eyepiece lens group having a positive refractive power for viewing the image.
