Patent ID: 6115182
Filing Date: 2000-09-05
Classification: G02B

Abstract:
A real-image finder optical system comprising:an objective optical system having positive power;an image-erecting optical system which erects an inverted image formed by said objective optical system; andan eyepiece optical system for viewing said erect image formed by said image-erecting optical system, in this order from an object;wherein said image-erecting optical system comprises:a pattern display surface having a reflective pattern thereon, said pattern display surface being provided on the side of said eyepiece optical system behind an image forming plane of said objective optical system;a half mirror surface being provided on the side of the object with respect to said pattern display surface, said half mirror surface being arranged to transmit a portion of light rays incident from the object, and reflect light rays which have been reflected by said pattern display surface; andwherein said real-image finder optical system is arranged to provide a real image of the object formed through said objective optical system and a virtual image of a pattern on said pattern display surface formed by an optical system including said half mirror surface so that an operator can simultaneously view both said real image of the object and said virtual image of said pattern on said pattern display surface through said eyepiece optical system; said real-image finder optical system satisfies the following condition:whereind.sub.1 designates the equivalent air thickness along the optical axis from said pattern display surface to the surface of said eyepiece optical system closest to the object; andf.sub.e designates the focal length of said eyepiece optical lens system.