GB326603A - Improvements relating to television and the like - Google Patents

Abstract

326,603. Harries, J. H. O. Jan. 19, 1929. Television.-A selected portion of the field of view is more finely scanned than the remainder, so as to produce an economy in the frequency -band -width of the transmitted signals, and the arrangement is such that two or more separate images are scanned so that the fine-scanning apertures need not be greatly reduced. In the arrangement shown in Fig. 1 an optical system 2 having a wide field of view projects an image 4 of the background of the film or object 5 on to a scanning apparatus 7, while a second optical system 1 having a narrow field of view projects an image 3 of a selected portion of the object that part of the first image which coincides with the second image being masked out by an opaque screen 17. Signals corresponding to the two parts of the picture are transmitted over channels 8, 9 to the receiver, whence the composite picture is projected on to the screen 16, which may be in two parts lying in parallel planes to accommodate the differing projective properties of the optical systems 14, 15. The scanning apparatus for the two channels are preferably coupled together at 18, 19. The area 23 of the object which is finely scanned may be moved about at the transmitter, and corresponding movements may be made at the receiver by hand or by means of a remote-control system. The two images may be used as the components of a stereoscopic object or of a coloured picture. In a modification, Fig. 2, the wide and narrow images may be projected on to the scanning apparatus 21 by reflectors 20, 21 respectively; the light forming the narrow image passes through the aperture 22. The relative positions of the wide and narrow images are adjusted by movement of the reflectors 20, 21 in the direction of the arrows.