Patent GB-1064528-A (GB)
Title: Improvements in or relating to printing
IPC: G03F3/08
Filed: 1964-09-23
Abstract: 1,064,528. Copying by scanning. D. J. KYTE. Sept. 16, 1965 [Sept. 23, 1964], No. 38782/64. Heading H4F. Photographic reproduction equipment comprises a cathode-ray tube scanner 18 for scanning a transparency 20 in combination with conventional means for reproducing by exposing film 3 on a rotating drum 1, the movement of the light spot on the face of the cathode-ray tube being synchronized with the rotational movement of the drum, while the ratio of the height of the raster of the CRT and the height of the effective reproducing sweep on the drum is variable in order to enlarge or reduce the size of the reproduced transparency. Synchronization is achieved by mounting on the drum shaft a transparent disc 7, Fig. 2, the outer track of which contains a circular array of equallyspaced opaque radial lines 71 and an opaque area 72 which coincides with that part of the drum containing the clips for holding the ends of the film. The inner track is opaque except for one transparent radial slit 75 positioned near the right-hand edge of the opaque part 72 for clockwise rotation of the disc. A light source 8, Fig. 1, directs a beam of light through rotating disc 7 and a fixed aperture plate 11, Fig. 3, having transparent lines 112 and a transparent slit 111, as shown, and is picked up by photo-cells 12 and 13. The electrical pulses from the photo-cells 12, 13 are passed into circuits 14, 15 which amplify, shape and limit them, the number of pulses from photo-cells 12 and 13 per revolution being equal to the number of lines round the disc and one respectively. A start control connection is also provided from photo-cell 13 to circuit 15. The pulses from circuits 14 and 15 are fed to staircase function generators 16, 17, the stepped outputs of which deflect the light spot on the cathode-ray tube 18 in the Y and X direction respectively. By means of this arrangement the raster on the cathode-ray tube is produced in synchronism with the movement of the rotating exposure drum 1 and the exposure light source 4. Instead of using staircase generators linear sawtooth generators may be used, and instead of using a transparent timing disc a magnetically coated disc or phonic wheel may be used. The image of the raster on tube 18 is focused on to colour transparency 20 by lens 19 and passed to a triple beam splitter 22-24 and photocells 28-30 via colour filters 25-27. The resultant electrical signals are modified in computer 31 and the four outputs of the computer are switched in turn or simultaneously to four exposing means 4. The enlargement factor produced by the system depends on the ratio between the peripheral speed of the exposing drum and the speed of the image of the light spot produced on the transparency 20. Thus to obtain different degrees of enlargement or reduction the size of the raster on the face of the tube is altered by changing the amplitude of the output steps of the two staircase generators 16, 17; changing lens 19 for another of different focal length; or by changing the relative positions of lens 19 and the tube 18. In an alternative embodiment, Fig. 4 (not shown), the cathode-ray tube has a fibre optic face plate, lens 19 is dispensed with and the transparency is mounted in contact with the face of the tube, the enlargement factor being produced by altering the size of the raster. The Specification states that the functions of the cathode ray tube and rotatable drum are interchangeable.