GB973041A - - Google Patents

Abstract

973, 041. Photographic printing apparatus. AGFA A.G. Feb. 20, 1962 [Feb. 25,1961], No. 6594/62. Heading G2A. A projection printing apparatus has a fixed negative stage, an adjustable positive easel, and a fixed focusing screen separate from the positive stage, means being provided for producing an image on the screen which automatically remains optically equivalent to that produced on the positive easel whatever the position of the latter. In the form shown, light from a source 4 passes through a system of optical elements 5, 6, 7, 8 to pass through the negative at 10. After passing through the objective 11, which is housed in a vertical guide 12, the light beam falls on the positive easel 14. This is housed in a box-like carrier 13 which can be moved vertically along a threaded spindle 20, its two extreme positions being shown in full lines and broken lines. Also housed in carrier 13 is an inclined partly transparent mirror 16 which reflects some of the light to a measuring device 18, 19. Just above the objective 11 is another inclined mirror 37, which, together with two further inclined mirrors 35, 36, constitute a system for reflecting part or all of the printing light beam on to a fixed inspection screen 38. The mirrors 35, 36 are mounted in a carriage 33 which can be moved horizontally by means of a threaded spindle 27. Spindles 27 and 20 are coupled together by bevel gears 30, 31 so that both spindles rotate together when driven by motor 23. The relative pitch of spindles 20, 27 is such that the distance a moved through by carrier 13 is twice the distance b moved through by carriage 33. Thus the light path between negative plane 10 and positive plane 14 is always equal to the light path between negative plane 10 and screen 38, whatever the position of plane 14. Focusing of the objective 11 may be effected by attaching a bracket 42 to the objective, a pin 41 at the end of the bracket riding on a cam surface 40 on a plate 39 fixed to the carriage 33.