Patent ID: 6362924
Filing Date: 2002-03-26
Classification: G02B

Abstract:
A real-image-type zoom finder formed of an objective optical system and an erecting eyepiece, as follows:the objective optical system consisting of, in order from the object side, a first lens element having negative refractive power with a concave surface on the object side, a second lens element having positive refractive power, and a third lens element that is a positive meniscus lens with its convex surface on the object side; the erecting eyepiece formed of an erecting prism having refractive surfaces integrally formed on the input end and output end of the erecting prism; whereinthe magnification of the finder is changed by moving the second lens element along the optical axis, and the third lens element is moved along the optical axis in order to adjust for what would otherwise be a shifting of image surface position with the change in magnification, and the following conditions are satisfied: 0.32/ft<0.6 1.04/D8<1.3 wheref2 is the focal length of the second lens element, ft is the focal length of the objective optical system at the telephoto end, f4 is the focal length of the erecting eyepiece, and D8 is the distance from surface of the erecting prism nearest the eye side to the eye position.