| 摘要 |
<p>1,051,953. Modulating light. GRETAG A.G. Oct. 25, 1963 [Oct. 26, 1962], No. 42273/63. Addition to 861,408. Heading H4F. [Also in Division H1] In the reproduction of television pictures by means of a schlieren optical system containing a deformable film controlled by a scanning electron beam, the beam is controlled so that the charge pattern laid down along the picture lines varies in width across the lines pointby-point in accordance with the video signal, the width being greater the lower the brightness of the picture point. The variation in the width of the charge laid down is effected by varying the focus of, i.e. defocusing, the electron beam. In the present Specification a magnetic quadrupole lens is used to vary the beam focus, whereas in the parent Specification an electrostatic quadrupole lens is used. As shown, Fig. 4, the defocusing device 104-107, Fig. 2, is disposed between the anode 74 and the focusing coil 76 of the cathode-ray tube outside the vacuum. The defocusing device, i.e. the magnetic quadrupole lens comprises four current conductors 104-107, connected together or bent out of a single piece of wire, disposed parallel and symmetrical to the axis 75 of the electron beam, the picture signal being fed in'at opposite ends of conductors 104, 107, such that the current flow directions are opposite one another in neighbouring conductors and the magnetic axes lie in a plane normal to the beam axis 75 and interset the latter at the same point. In a further embodiment the defocusing device may comprise four identical coils disposed symmetrically to the axis of the electron beam with the current flow directions opposite to one another in neighbouring coils and the modulation signal fed to all four coils with identical ampere turns but with alternating directions.</p> |
