Patent ID: 6178052
Filing Date: 2001-01-23
Classification: G02B

Abstract:
A single image formation type finder optical system comprising:an objective lens-acting surface which forms an object image;an image inversion optical subsystem which erects the object image; andan eyepiece lens-acting surface which guides the object image to a location where it may be observed,wherein the image inversion optical subsystem comprises in order from an object side thereof,a first prism, anda second prism,the second prism comprising,a first surface through which light enters the second prism after having exited the first prism,a second surface which reflects light incident from the first surface,a third surface which reflects light incident from the second surface, anda fourth surface through which light incident from the third surface exits said fourth surface on a pupil plane side thereof,the first prism comprising,a fifth surface through which light enters the first prism from an object side thereof,a sixth surface which reflects light incident from the fifth surface,a seventh surface through which light incident from the sixth surface exits the second prism,the second prism constructed and arranged such that an optical path connecting the first surface to the second surface crosses over an optical path connecting the third surface to the fourth surface, andat least one of the second surface and the third surface having a power and having a rotationally asymmetric surface.