OPTICAL PROJECTION SYSTEM COMPRISING PLATE POSITIONING MEANS

摘要

In order to position a sensitized plate in the image plane of a projection lens, the optical projection system is provided with a set of extensible jacks placed in a circle around the lens, the desired image plane being defined by the ends of the jacks when they are in the outwardly displaced position. The plate can then be placed against the ends of the jacks by means of a spherical-bearing unit which is locked in position, whereupon the jacks are caused to withdraw and the plate can be displaced in the image plane while remaining at the focusing distance. The invention is well suited to the construction of photorepeaters.