Patent GB-289416-A (GB)
Title: Improvements in television methods and apparatus
IPC: G02F1/07
Filed: 1928-04-26
Abstract: 289,416. Chilowsky, C., and Guerbilsky, A. April 26, 1927, [Convention date]. Television; synchronous movements. - In a wireless television system, the amplitude of the transmitted wave is varied in accordance with the light-intensity of successive elements of the image to be transmitted, and the frequency of the same or another wave is varied in accordance with the position of the element under examination. The rotating mirror or other exploring device may be coupled to a variable condenser in the valve generator in such a way that for each complete cycle of the exploring device the frequency generated is varied through a corresponding cycle, or alternatively two frequencies may be used on a co-ordinate basis. one varying slowly to determine a group of elements and the other quickly to determine a particular element in that group. At the receiving station, the current of varying frequency may render operative in succession a series of piezo-electric crystals, equal in number to the elements of the image, or alternatively if two frequencies are used each may control a smaller number of crystal units. A piezo-electric device may be controlled by one frequency and a rotating mirror or other mechanical device by the other frequency. The mirror may be driven by a motor kept in synchronism by piezo-electric means. Alternatively the currents of varying frequency may control a corresponding series of tuned oscillating circuits, each controlling neon tubes or Kerr cells. In the transmitting system shown in Fig. 5, a rotating wheel R carrying mirrors projects the image on a photo-electric ceil c controlling the amplitude of oscillations radiated by an aerial 63, and a condenser C on the wheel R continuously varies the frequency of oscillations radiated by the aerial 61. In a modification (Fig. 1 not shown) the photo-electric cell and the condenser control respectively the amplitude and the frequency of the oscillation generated by a single valve. In the receiving system shown in Fig. 2, a series of piezo-electric laminae Q of different natural frequencies is arranged between a polarizer P and analyzer A and the associated electrodes of each laminae are connected in parallel across a circuit 3 coupled to the receiving aerial 4<1> by circuits which give broad tuning so as to cover the variable frequency band. The series of piezo-electric laminae may be replaced by a single unit the thickness of which varies from point to point, as shown in Fig. 4, or, as shown in Fig. 9, by two units 31. 32 of trapezoidal section, this section of unit 31 being in the plane of the paper and of unit 32 being perpendicular to the plane of the Figure. The two units are controlled by separate wireless receivers 37, 38 and determine the luminous point on a co-ordinate basis. In the receiving system shown in Fig. 6, the oscillations of constant frequency but variable amplitude are received at 82 and control a source of light 73, and the oscillations of varying frequency are received at 71 and influence the crystal Q controlling the position of the luminous point. In a modification, the series of crystal laminae (such as Q, Fig. 2) has two pairs of electrodes, one pair 45, 46, Fig. 8, being included in the circuit 3, Fig. 2, so as to determine the position of the luminous point, and the other pair 39, 40, Fig. 8, being included in the anode circuit of a valve connected to an aerial 82 receiving the constantfrequency oscillation. In the system shown in Fig. 12, the polarized beam passes through a crystal 31 and is reflected by a mirror m rotated by a motor, the combined effect of the crystal and the mirror determining the luminous point at any instant. The electrodes of the crystal may consist of liquid conductors in glass containers, thus permitting the passage of light through the electrode. The motor driving the mirror may be synchronized by piezo-electric means, a member on the rotating shaft having its ends arranged to pass near a series of crystals &c. designed to oscillate one after the other in response to the varying frequency of the received current, and to influence the member either by direct contact or air vibrations. The member may be replaced by a toothed disc co-operating with several series of crystals. An alternative receiving system (Fig. 14, not shown), comprises a series of oscillating circuits tuned to different frequencies and corresponding in number to the elements of the image to be transmitted, and a flattened neon tube hav. ing on one, wall a corresponding number of electrodes connected respectively to the several oscillating circuits, the other wall having a transparent metallic coating connected to all the oscillating circuits. The single tube may be replaced by a series of neon tubes, each connected to an oscillating circuit, stabilized by a piezo-electric crystal. Ultra-violet radiations may be used at the transmitting or receiving station. Monochromatic light may be used at the receiver. Specification 277,761 is referred to.