OPTICAL SYSTEM HAVING LENS AND TWO MOVABLE MIRRORS

摘要

An optical system for photocopiers to project an image from an object plane to an image plane is provided. The optical system includes a lens system and a two-mirror reflecting system embodying two mirrors preset to a given angle. This mirror system is so mounted as to head the light path into a direction perpendicular to the image plane. The lens system is mounted with its optical axis perpendicular with the object plane. The mounting of the two mirrors is such to permit the mirror system to move as a unit on a path bisecting the angle formed by the intersection of the perpendiculars to the object plane and image plane. This allows a presetting of the mirrors outside the machine and a focusing of the system in the machine by changing the length of the optical path without changing the angle and location of the optical axis with respect to the image plane. Also, the lens system is movable along the optical axis to adjust size ratio of the projected image to the subject matter on the object plane. With this arrangement it is discovered that image size determination and refined focusing can be achieved by simple translatory adjustments of the lens and of the two-mirror system, without shifting the image location in the process.