Patent GB-1125346-A (GB)
Title: Apparatus for generating electrical signals representative of visual images
Inventor: MOORE JAMES KENNETH
IPC: H01J31/28
Filed: 1966-06-30
Abstract: 1,125,346. Copying by scanning. COLUMBIA BROADCASTING SYSTEM, Inc. 30 June, 1966, No. 29483/66. Heading H4F. [Also in Division H1] A font 44 of characters (4 as illustrated but typically 256 in a practical arrangement) is illuminated by a source 40 to produce an image on the photo-cathode 46 of an image dissector tube which includes an anode 48 having a separate aperture 50 for each character. The electron image from the cathode is scanned over the anode in a sequence of horizontal and vertical movements corresponding to a television-type raster, the scan amplitudes being such that each character is traversed over only its associated aperture. Electron streams corresponding to all the characters are thus produced simultaneously through the apertures and a selected one is allowed to pass to a photomultiplier 54 to produce a signal output at anode 56 by the application of potentials to selected orthogonal elements in a grid structure 52. As illustrated the structure comprises two sets of fine wires with the wires divided into pairs connected to a single terminal and the intersections of the pairs defining rectangular areas aligned with the apertures 50. In another construction the pairs of wires may be replaced by perforated metal strips. Selecting potentials of smaller amplitude may be used in a first modification, Fig. 6 (not shown), in which the grid structure is located between the apertured anode and further electrode having a similar arrangement of apertures. The electron streams are allowed to pass through the grid and the potentials are merely required to be sufficient to deflect the streams so they are either intercepted by the further electrode or a desired one is allowed to pass through an aperture. In a second embodiment, Fig. 7 (not shown), the main anode is followed by another apertured electrode in which the apertures include secondary emitting elements. These function as transmission dynodes to produce current amplification and electron streams of reduced velocity which may be controlled by potentials of lower magnitude applied to the grid structure. The light source 40 may be replaced by a cathode-ray tube, Fig. 5 (not shown), which is controlled to illuminate with a spot of suitable 'size only the character which is to be scanned by the image dissector. The operation of the cathode-ray tube is synchronized with the means which applies the potential to the grid structure. With this arrangement electron images corresponding to the characters are produced oneat a time. The character signal generator may be incorporated in an apparatus, Fig. 4 (not shown), for displaying and recording information in response to the signal output from a computer. The signal from the character signal generator is applied to a cathode-ray display tube which is scanned in an identical fashion. The computer signals are decoded to derive "x" and "y" signals which are employed (1) to control the grid structure 52 to select the desired characters and (2) to position the scanned area in the display tube so that the displayed characters are assembled in a desired page or collumner form. Additional code marks associated with each character in font 44 are provided to signal to control circuits the size of the characters so as to establish proper spacing of the reproduced characters. The cathode-ray display tube is photographed as the first step in the production of a printing block and is also exposed to a rapid copying apparatus for producing copies of lower quality for proof reading.