Patent ID: 6538699
Filing Date: 2003-03-25
Classification: G02B

Abstract:
A real-image finder comprising an objective optical system which forms an image of an object onto a primary image forming surface; an ocular optical system through which the object image formed on the primary image forming surface can be viewed; and an image erecting optical system which inverts the object image formed by the objective optical system, in the vertical and horizontal directions; said real-image finder comprising:a rectangular body which is comprised of a main frame having a generally U-shape section which is uniform in the optical axis direction, said main frame being provided with a pair of front and rear end openings in the optical axis direction and a side opening, and a separate cover which is adapted to close said side opening of the main frame; a field frame that is supported within said rectangular body on said primary image forming surface; a pair of transparent members which close said pair of front and rear end openings of the rectangular body; at least one sealing member for sealing a contact portion between the main frame and the cover, and for sealing a gap between the rectangular body and the transparent members; a field frame switching mechanism which mechanically switches the size of the field frame in the rectangular body, wherein said field frame switching mechanism comprises: a pair of U-shaped grooves which are provided on the side-opening side of said parallel wall portions of said main frame, said pair of U-shaped grooves lying in a line perpendicular to the optical axis; and a movable field frame member separate from said field frame, supported in said U-shaped grooves so as to rotate about rotation shafts between a lowered position, in which the movable field frame member is located on the optical axis in the close vicinity of the primary image forming surface, and a raised position, in which the movable field frame member is retracted from the optical axis; said U-shaped grooves intersecting linear grooves; said rotation shafts of said movable field frame member projecting above the bottom surfaces of the linear grooves to reduce the distance from the cover; and said at least one sealing member being inserted in the linear grooves and being located on top of the rotation shafts.