GB994977A - Improvements in or relating to photographic cameras - Google Patents

Abstract

994,977. Photolithographic camera; optical apparatus. C. P. GOERZ AMERICAN OPTICAL CO. Sept. 11,1961, No. 32558/61. Headings G2A and G2J. A projection unit for forming a laterally reversed image of an object, e.g. in a photolithographic camera, comprises a housing formed by a pair of half shells which mate along a central vertical plane and are releasably held in contact as by bolts or screws 5 passing through lugs 6, 7, 8, 9 to form an upper chamber 2 having a vertical front opening 11 and enclosing a roof prism 12, a lower chamber 3 having a vertical rear opening 22 and enclosing a mirror 19, and a tubular neck 4 connecting the chambers and containing an interchangeable objective 18 which is clamped in position by the assembly of the half shells, the roof prism having a vertical inlet surface 13 toward the front opening 11, asymmetrical roof surface 14 having the roof edge in the central vertical plane and inclined at an angle of 30 degrees to 40 degrees to the inlet surface and an exit face 15 adjacent the objective. As shown, for the purpose of producing slight overlap of lines in the lithograph picture, especially to produce agreement between colour separation records taken through different colour filters, the roof prism is supported by a cardan suspension comprising an inner ring 29 holding the prism, an outer concentric ring 31, a first axle 32 pivotally connecting the rings and a second axle 33 pivotally connecting the outer ring to the housing and at right angles to the first axle, and a part 36 fixed to the prism has a recess engaged by an eccentric cam 35 on a rotatable shaft 34 inclined to both axles so as to impart a rocking movement to the prism during exposure. A shutter 42 is pivotally mounted in the housing and is movable to cover the exit face of the objective by means of a solenoid 44 having a movable core 45 connected to the shutter and the objective is provided with an iris diaphragm 37 controlled by a pin 38 adjusted by a micrometer screw. The mirror 19 is carried by a support 23 pivoted at 24 and adjusted in position by a screw 25. The roof prism is preferably made of glass of refractive index of at least 1. 60 and the lenses and the prism are made of glasses having about the same dispersion coefficient.