Patent GB-289307-A (GB)
Title: Improvements in or relating to television and like systems
IPC: H04N3/04
Filed: 1926-10-15
Abstract: 289,307. Television, Ltd., and Baird, J. L. Oct. 15, 1926. Divided on 289,104. Television.-In a system for effecting exploration of the image or screen along parallel strips by the use of one or more rotating discs provided with slots, holes, lenses, or mirrors, the component of exploration laterally of the strips may be periodically changed in direction, e.g. may be reversed for each successive transversal, or the inclination to a datum line of the strips may be changed for different, e.g. successive, traversals, or images produced by simultaneous explorations in different directions may be superposed. Fig. 1 shows an arrangement for exploring an image 17 by two sets of holes in a rotary disc 10, the sets being arranged along spirals 13, 15 of opposite pitch so that the lateral components of successive traversals are reversed i.e. from left to right and vice versa. Fig. 2 shows a modification in which one set of holes aranged along a spiral 22 effects an exploration having its lateral component from right to left simultaneously with an exploration having its lateral component from left to right effected by another set of holes arranged along a spiral 24. The strips in each such exploration may together constitute a complete image, or the strips of one exploration may alternate with those of the other. In a further modification simultaneous explorations with oppositely-directed lateral components as in Fig. 2 are effected by two sets of holes, each set being arranged along two spirals of opposite pitch as in Fig. 1. Fig. 4 shows an arrangement in which the directions of the strips in successive traversals are at right angles. Two discs 33, 38 rotating at equal speeds about parallel axes are employed, having holes arranged along spirals 35, 39 for exploring the image in vertical and horizontal strips respectively. These explorations are effected alternately, one half of each disc being slotted at 43, 44 to expose the image to the other disc. In another arrangement, employing two overlapping slotted discs rotating at different speeds about parallel axes, the slots in the faster disc are radial, and alternate slots in the slower disc are inclined to the radius in opposite directions. In the arrangement of Fig. 6 an image 55 is explored by holes in overlapping discs 49, 50 rotated in the same direction and at the same speed about parallel axes, slots being provided in each disc to exposethe holes in the other disc. The holes in each disc are arranged along a pair of spirals 51, 52 and 53, 54 and the holes of each spiral explore alternate strips of one half of the image. In the arrangement of Fig. 7 holes arranged along a spiral in one disc explore the image along strips at right angles to the strips similarly traced by holes arranged along a spiral in the other disc. Alternatively two separate images of the scene may be employed each with its own light-sensitive cell, and transmission channel, the strips of exploration of one image being at right angles to the strips of exploration of the other. In all cases requiring the rotation of two discs at equal speeds the discs may be driven through a triangular connecting member or through two coupling- rods each connecting a pair of cranks arranged at an angle to the cranks of the other pair. In a further modified exploring arrangement the direction of exploration is varied by causing theimage to rotate in relation to the exploring devices, e.g. by the use of mirrors 67, 68, 69, Fig. 12, or of a total reflection prism 70, Fig. 13, rotating about the axis 71, a similar arrangement being used for reconstituting the image at the receiving station.