Patent GB-253957-A (GB)
Title: Improvements in apparatus for transmitting views to a distance
IPC: H04N3/04
Filed: 1925-01-01
Abstract: 253,957. Baird, J. L. Jan. 1, 1925. Television apparatus.-A series of lenses is so arranged on a support in front of the scene or image to be transmitted that as the support is rotated there is effected a translational movement of the image-beams over one or more lightsensitive cells. The lenses may be arranged on a disc 1 carried by a rotatable shaft 16, either spirally, as shown at 2 - - 12, 12<1>, Fig. 1, or in staggered formation, or in a circle concentric with the shaft, in which case the shaft is reciprocated at right angles to its length during the rotation. Alternatively, the support for the lenses may be a rotatable cylinder or truncated cone. To obtain a finer subdivision of the image or scene 13 during its exploration by the lenses means may be provided for effecting an additional translational movement of the image-beams over the cell 14. In the arrangement of Fig. 1 this additional movement is obtained by reciprocating the shaft 16 at right angles to its length, the shaft being mounted for this purpose in a frame 17 which is rocked about an axis 17', 18<1> against spring action by a cam 18 on a countershaft 20. The additional movement may also be obtained by a similar reciprocation of the cell 14 with its aperture 15, or of the aperture only, or by arranging between the rotary disc and the cell a rotary or reciprocating shutter, or an additional series of lenses on a rotatable support, or a vibrating mirror. A rotary shutter for this purpose mav be constituted by an opaque disc, e.g. of celluloid or like material painted black, provided with a spiral or heart-shaped, clear space or slot. Fig. 10 shows an arrangement in which the light passes to the cell 75 from an aperture 75<1>, reciprocated in the plane of the image, along a rod 71 of glass or silica mounted on pivots 73. 74 adjacent to the cell. Figs. 4 and 5 show shutters with clear spaces or slots arranged to expose successively each of three cells 43, 44, 45. Such cells may be connected in parallel, a twoelectrode thermionic valve oeing arranged in series with each cell to prevent the shortcircuiting of one cell by another. An arrangement for amplifying the current from the cell 14 is indicated in Fig. 1. An intermittent current in the cell circuit 95, 96 is obtained by the use of a shutter to interrupt the light incident on the cell, or by the use in the circuit of a neon tube in parallel with a condenser, and this circuit is connected through transformers and a tuned circuit comprising coils 100, 101, and a condenser 102 to the filament-grid circuit of a valve with output terminals 106, 107. The receiving apparatus is similar to and is moved synchronously with the transmitting apparatus, the reproducing screen replacing the image 13, and one or more sources of light, varied in intensity in accordance with the received currents, replacing the cell or cells 14. The received potential may be applied 'to a pair of plates or grids immersed in carbon bisulphide to control a beam of light passing through the liquid between Nicol prisms. Specification 230,576 is referred to.