GB356760A - Improvements in the electrical reception and transmission of pictures - Google Patents

Abstract

356,760. Television. BRONK, 0. VON, 12, Hallesches Ufer, Berlin. March 11, 1930, No. 7849. [Classes 39 (i) and 40 (iii).] A television transmitter or receiver comprises a screen made up of a set of linear glow lamps which light up in succession under the control of voltages applied through time-lag circuits in the manner described in Specification 277,761, [Class 40 (iii) Telegraphs, Electric]. Thus at the transmitting station, Fig. 4, the light from a battery of successively ignited vertical discharge tubes 1 may fall upon a transparent picture 2, after leaving which it is focused on a light-resistance cell 4. Scanning in the vertical dimension may be obtained by means of a slot 5 in a moving screen (Fig. 1, not shown, and Fig. 4), or by movement of the object where this is a kinematograph film. The light may in this case be focused by means of cylindrical lenses (Fig. 2, not shown), or the tubes may be end-on to the film (Fig. 3, not shown). In the arrangement shown in Fig. 4 voltage impulses are applied, in parallel with a condenser and with a source of primary voltage 14, by an induction coil 16 to a number (such as a hundred) of discharge tubes 1 through a tapped inductive resistance 18 which produces a differential phase-lag so that the tubes light up in succession and effect scanning in the horizontal dimension, while the slot 5 (which may be a radial slot in a revolving disc, Fig. 5, not shown) effects scanning in the vertical dimension. The wireless transmitter 24 is modulated by picture current from the photo-electric cell 4, and in addition it is modulated at the spark frequency, such as 1000 #, of coil 16 by way of transformer 22. At the receiver (Fig. 5, not shown) the arrangement is similar; the spark-frequency impulses applied to the discharge tubes are superimposed on the picture-current voltage and have a priming effect, so that those tubes light up in which the resultant voltage is sufficiently high. The speed of the slot 5 at the receiver is controlled by a local motor. In a modification a rotating mirror may be used instead of the moving slot 5. Shape of apertures. The number of the tubes 1 may be reduced, so that the shape of the " apertures " becomes rectangular, the width of the slit 5 being less than that of the tubes 1. Transmission of opaque figures. In the modification shown in Fig. 6 the tubes 1 at the transmitter are arranged end-on to an oscillating mirror 43 and the light, after being focused by a cylindrical lens 41, is reflected by the mirror on to an opaque object 44 and thence via a paraboloidal mirror 45 to a light-sensitive cell 46. Vacuum apparatus. A glow lamp for use as a reproducing screen for a television receiver comprises a number of cathodes 52, Fig. 7, associated with separate anodes a and a common control electrode 51. Signals are applied to the electrode 51 directly through a transformer T and to the anode a through time-lag circuits 63 having different time-constants.