GB909203A - Improvements in or relating to photographic type composing apparatus - Google Patents

Abstract

909,203. Photographic type - composing; lenses. FRANKEL, G. Nov. 7, 1959 [Nov. 8, 1957], No. 34958/57. Classes 97 (1), 98 (1) and 98 (2). Photographic type-composing apparatus comprises a keyboard for selecting characters for composition, means for producing a latent image of the selected character on a radiation-sensitive surface at an exposure station, developing means for rendering visible the latent image when it leaves the exposure station, and means for moving the radiation-sensitive material in succession through the exposure station and developing means to a viewing position where the developed images are visible to the operator shortly after the selection of the corresponding characters. As shown, selection of a character by operation of a keyboard 7 moves a font plate 14 to position the selected character image for projection by an objective 18 on to the photographic strip 19, operates the disc shutter 15 to effect exposure when the selected character is so positioned, and thereafter operates a driving roller 20 to move the strip in accordance with the width of the recorded image. The character plate is illuminated by means of a mercury arc lamp 10, a black filter 12 passing near ultra-violet, a moulded glass condenser lens 11 having a convex spherical surface towards the arc and a paraboloid surface remote from it to image the arc on the character matrix, and a heat absorbent screen 13. The objective 18 is a symmetrical four element system of borosilicate crown glass of refractive index 1.530 at 3655A and comprises outer concavoconvex lenses 30, 30<SP>1</SP> of radius - 21.3 &c. + 7.1 cms. and inner plano-convex lenses 31, 31<SP>1</SP> with a radius of +10.6 cms., the axial thickness of each lens being 0.2 cm. and the air-separation being 0.1 cm. For unit magnification the character plate-to-tape distance is 20.6 cms. The tape 19 is an ultra-violet sensitive film including a diazo material which yields a vesicular image after exposure when developed by heating, for which purpose the tape is passed over a shoe 21 heated to 255‹ F. and arranged so that the tape is in contact with it for at least 2 secs. If keyboard operation is interrupted so that the tape remains stationary, a timeswitch device will withdraw the shoe from the tape, the shoe being returned in contact with the tape on operation of a character key. Alternatively, a heated drum or radiant heat may be employed for development. The permanent record so produced is illuminated by means of a white light filament lamp 24 and condenser 25 and a projected image is formed by a lens 26 on a viewing screen 27 seen by the keyboard operator. If desired, the operator may be enabled to view the exposing image providing that the exposing beam contains some visible light. The strip 19 will be subsequently rephotographed on to a sheet of film or a plate to provide matter in page form. Reference is also made to the alternative use of a xerographic procedure as suitable for producing a rapidly developable image. The Provisional Specification describes also a shutterless exposure arrangement in which the light source is a flash lamp energized when the character plate has been positioned under keyboard control and the developed image is viewed directly. Instead of recording on a tape, a wide strip may be used so that recording is effected in page form so that interline spacing may be checked also.