GB321441A - Improvements in or relating to television apparatus and the like - Google Patents

Abstract

321,441. Baird, J. L., and Television, Ltd. July 11, 1928. Television.-In an apparatus for stereoscopic television, two aspects of an object or scene are transmitted successively through a single communication-channel and reproduced in juxtaposition, at such a rate as to be within the persistence of vision of the observer, which involves the transmission of some 12 images of each aspect per second. The scanning disc 14, Figs. 2 and 3 is provided with two sets of holes 10, 11, Fig. 1, lying on spirals whose " operative points " are 12 and 13 respectively, and which are spaced any desired distance apart, e.g. the spacing of human eyes. In the transmitter, Fig. 2, the light sources 17, 18 scan the object 21 alternately, and from a different angle, through the spirals 10, 11, whose fields are represented as 15 and 16 respectively, and light from the sources, reflected from the object, is received by the light-sensitive cells 22, 23 respectively. At the receiver Fig. 3, glow discharge lamps 24, 25 in conjunction with an identical scanning disc 14, produce two images in alternation which are in juxtaposition and are viewed by a stereoscope 26. Exaggerated stereoscopic effects may be obtained by using scanning discs of the type shown in Fig. 4, in which 30, 31 are the widely spaced " operative points " of the spirals 28, 29 respectively. Colour effects may be obtained by reproducing one picture in red and the other in blue by using a filter of appropriate colour with each spiral on both scanning discs. For a three-colour process the disc 32, Fig. 5, is preferably used in which the three outer spirals 33, 34, 35 have an " operative point " 39, and the three inner spirals 36, 37, 38 have an " operative point " 40, the spirals of each group being provided with blue, green, and red colour filters respectively, arranged in any desired sequence. An alternative scanning scheme employs a disc 41, Fig. 6, having two spirals 42, 43 extending substantially all round the disc, having " operative points " 44, 45, respectively, and whose corresponding light-apertures are on different but adjacent radii so that at any given time one band only of one of the pictures is being explored, and the transmission consists of a series of intercalated bands from the two images. The light-apertures in the scanning discs may be replaced by lenses, mirrors, or the equivalents. Specification 266,564 is referred to.