Abstract: A reference jig for positioning and fixing a lens or lenses in a predetermined position on a lens support structure, the reference jig including for positioning and fixedly bonding a plural number of lens components on a lens mounting surface of the support structure: a plate-like main body having a predetermined thickness and detachably fixable on the lens mounting surface of the support structure; registration members provided contiguously to the main body and engageable with reference walls of the lens support structure to hold the main body in registered position relative to the lens support structure; and notched positioning wall portions each formed in the main body and abuttingly engageable with at least two transversely opposite corner portions of a lens component to hold same in a predetermined position on the lens support structure.

Abstract: A main lens carriage holding a main lens assembly is moved along the optical path by a cam cylinder. A supplemental lens element is operatively coupled with the main lens assembly at the proper position to attain the desired optical reduction ratio. When the main lens assembly deviates from the proper position, a main lens support frame is shifted along the optical path in and relative to the main lens carriage by a correcting mechanism so as to correct the deviation. A further supplemental lens element is provided, but does not move with the main lens assembly. Both supplemental lens elements swing into and out of the optical path under cam action; and further cam action is provided to ensure that the two swinging lens elements do not collide with each other. The main lens support frame is rapidly moved along the optical path by the cam action of a rotating cylinder having a cam groove having part-circular portions that define the desired dwell positions and having open ends.