GB1163919A - Device for Automatic Sequential Image Transposition and High Density Microfacsimile System - Google Patents

Abstract

1,163,919. Facsimile system. MINNESOTA MINING & MFG. CO. 9 Dec., 1966, No. 55361/66. Heading H4F. [Also in Division H1] The Specification describes a microfacsimile system, whereby engineering drawings, for example, scanned with a resolution of 1000 lines are directly recorded by one electron beam of 10 Á diameter with a resolution of 100 lines/mm. Means for producing such a sharp electron beam are described together with means for focusing it and checking for astigmatism. Only part of the available recording area may be used for any one reproduction, means determining the end of the recording of a first image and causing the movement of the electron beam to a different area of the recording area for the recording of a second image. The drawing &c. is scanned in a picture generator 101, Fig. 1, by a 1000 line raster and the resultant video signal is modulated on to a carrier at 104, redetected at 107 and used to amplitude modulate the flow of a stream of electrons from a cathode-ray tube cathode 10, Fig. 2. A first focus of the electron beam is obtained between grid 11 and anode 12, a second at 15 between magnetic lenses 16 and 17 and a third having the desired beam diameter of 10 Á in the plan of the scan-field 19. Astigmatism of the beam is controlled by a stigmater 20, comprising Fig. 3, a ring of electrostatically charged, mutually insulated rods 26 axially surrounding and parallel with the beam axis. To determine if the beam is in focus and free from astigmatism, the normal workpiece 19, on which the drawing is directly reproduced by the electron beam, is replaced by a focusing target 120, Fig. 4, comprising a vapour deposited gold cross 119 on an aluminium substrate. The cross has arms of less thickness than the beam width-i.e. less than 10 Á. As the target is scanned by the electron beam, secondary electrons are produced by the cross, which are fed to a T.V. monitor 122. Astigmatism or bad focusing of the beam will show in the arms of the displayed cross not being equal. A line counter 110 determines when one picture has been recorded and actuates device 111 for adjusting the bias on the deflection signals applied to the cathode-ray tube so as to shift the electron beam to its rear area.