Patent GB-218766-A (GB)
Title: Improvements relating to apparatus for transmitting electrically scenes or representations to a distance
IPC: H04N3/02
Filed: 1923-04-18
Abstract: 218,766. Stephenson, W. S., and Walton, G. W. April 18, 1923. Copying - telegraphs; television apparatus. - In picture-transmission apparatus of the type embodying at the transmitting station two members moved continuously to cause light from successive areas of the picture to be directed in rapid succession on one or more light-sensitive elements, or embodying at the receiving station two members similarly moved to cause a source of light to illuminate successively each area of the recording surface or viewing screen, (1) either member may be adjusted in relation to the other to ensure correct framing of the picture i.e. correct arrangement of the areas of the received picture to correspond with those of the transmitted picture, (2) when the members are rotating discs provided with narrow continuous slits, such slits are so shaped and inclined to each other that the picture is explored in successive parallel lines at the same speed in all parts of the picture. An image of the picture 1, Fig. 1, to be transmitted is focused by a lens 2 on the plane of the rotating discs 3, 4 as shown at 9, Fig. 2, and the light passing the discs is focused by a lens 5 on a light-sensitive element 6. One disc may be driven at a much higher speed than the other, or if driven at the same speed as shown, one disc is provided with more slits than the other. The framing adjustments are effected while the discs are rotating by sliding one or the other or both of the worms 15, 16 in keyways on the driving shaft 14. In a modification each disc is driven from the same source of power through a separate differential gearing of which the carrier for the planet wheels' may be adjusted while the discs are rotating. The discs may be variously arranged to provide successive traverses of the image in the'same direction or alternate traverses in opposite directions and the discs may be arranged concentrically instead of eccentrically. The slits may also be so arranged that successive traverses are separated by areas which are traversed subsequently, the order of successive traverses being, for example, as shown at 1 - - 12, Fig. 13. Polyhedral mirrors may be used in known manner to explore the picture in place of the slitted discs, or one such mirror may be used in conjunction with one slitted disc. The transmission and the synchronizing of the moving members at the two stations may be effected wirelessly or by wired-wireless as described in Specification 213,654. Figs. 17 and 18 show arrangements at the transmitting and receiving stations respectively for reproducing pictures in colour. The lens 5, Fig. 17, concentrates the light passing the discs 3, 4 on a prism 48 to form a spectrum 49. Lenses 50, 51, 52 focus the blue, green, and red rays on light-sensitive elements 6<a>, 6<b>, 6<c> respectively. Each such element is arranged to modulate the continuous wireless or wired-wireless wave with a current of a definite low frequency to control a corresponding Einthoven or like galvanometer 53<a>, 53b, or 53<c>, Fig, 18, at the receiving station. A lens system 56 concentrates white light from a source 54 on a prism 57 to produce a spectrum 55 of which the blue green, and red rays are focused by lenses 58, 59, 60 respectively on to the galvanometers 53<a>, 53<b>, 53<c> which each allows an amount of coloured light to pass in accordance with the illumination of the corresponding element 6<a>, 6<b>, or 6<c>. This light is focused by lenses 61, 62, 63 on a collecting prism 64 and passes through lens 66, and slitted discs 67, 68, and a second lens 69 to the viewing screen.