GB1291501A - Thin-window image pick-up and recording tube - Google Patents

Abstract

1291501 Facsimile system MATSUSHITA ELECTRIC INDUSTRIAL CO. Ltd 21 July 1970 [23 July 1969 (2) 28 July 1969 (4)] 35221/70 Heading H4F [Also in Division H1] A cathode-ray tube adapted for pick-up or recording in a facsimile transmission system comprises a luminescent strip screen 19 disposed in a slit in the end wall of the envelope 11 adjacent a thin window 18. In the recording mode the modulated light from the screen exposes photo-sensitive material disposed adjacent the window. In the pick-up mode the copy 22 is illuminated by unmodulated light from the screen, and light 23 reflected from the copy is reflected at the surface 24 of the envelope 11 and passes sideways out of the envelope to a photo-sensitive detector. The surface 24 may be coated with aluminium, gold or nickel, and the phosphor 19 may be provided with a metal backing 25. There may be a gap 26 between the window 18 and the envelope 11 so that rays 23 at greater than the critical angle do not pass to the output; this increases the signal/ noise ratio. The window 18 may be joined to the envelope 11. The surface 24 may be parabolic or elliptical (Fig. 5, not shown). The detector may comprise photo-conductive material (27, Fig. 6a, not shown) coated directly or through an intermediate layer or to the envelope. Alternatively the light emerging from the sides of the envelope may be focused by a convex lens or a Fresnel lens or to one or more photo-multipliers (Figs. 6b-6d, not shown). Operating circuit, Fig. 7.-In the pick-up mode, signals from the detectors 29 on each side of the window assembly 13 are fed through respective amplifiers to a comparator 39 which controls the deflection coils 16 so that the beam is maintained in the centre of the slit target. The signal output is fed to a mixer 41 where synchronizing signals from unit 42 are added, and the mixer controls the modulator 43. In the receive mode the signals from the amplifier 36 and detector 35 are fed to the amplifier 32 controlling the electron gun and to the deflection control circuit 33.