Patent GB-1262507-A (GB)
Title: Method and system of sequential color television pickup and transmission
Inventor: STEPHENS KENNETH DEAN JR
IPC: H04N11/08
Filed: 1969-06-19
Abstract: 1,262,507. Television. ELECTRONIC RESEARCH CORP. 19 June, 1969, No. 31185/69. Heading H4F. A colour television system is described in which a plurality of dichroic reflectors, e.g. plane mirrors, or prisms, Figs. 5 and 6 (not shown), produce from a single polychromate image input an array of at least three primary colour images on the face of a single vidicon, entire images being scanned in turn to pruduce field sequential colour signals for transmission to a display device. The array may comprise four images in rectangular disposition, each column of two images being scanned alternately, Fig. 4 (not shown), but the system is described mainly in terms of three vertically stacked images. The vertical scanning frequency of the camera and/or the display device must be modified, e.g. 60 and 180 Hz respectively reducing the lines per colour field by one-third, or 20Hz and 60Hz, for the normal number of lines per field. If the colour signals are to be transmitted by wire, together with sync. signals from the camera, it is possible to separate the different colour fields at the camera for transmission along different wires connected to the respective inputs, e.g. of a monitor cathode-ray tube. Thus Fig. 7 (not shown), illustrates a camera sync. generator, signals from which also control three double diode gates disposed between a single video input and three output lines. If single wire or aerial transmission is desired, a pulse is added to identify a particular field, e.g. before every green field, coincident with the vertical sync. pulse, Fig. 9 (not shown). At the receiver, pulses at vertical sync. frequency are separated and differentiated, and the tips only of the larger pulses due to the combination of a vertical sync. pulse and an identification pulse are clamped, Fig. 12 (not shown), to provide pulses which determine the initial state of a divide by three counter actuated by vertical sync. pulses and controlling the switching of the video signal to the three inputs of a colour cathode-ray tube, Fig. 11 (not shown). The colour switching arrangement shown in Fig. 7 (for the camera) may be substituted for that shown in Fig. 11. Fig. 10a (not shown) and Fig. 11 show a switching arrangement for actuating the vertical hold and vertical size circuits of a receiver, together with the colour switching circuit, when it is desired to also receive other (NTSC) colour signals. In Fig. 14 (not shown), a remote camera receives the array of primary images, which are reproduced on a conventional black and white monitor. The monitor is viewed by a further camera to give signals which are supplied to a colour monitor. The signals may be separated into component R, G and B signals, which are fed to duty cycle extending devices to give simultaneous signals which may be used to form, e.g. an NTSC signal. Fig. 15 (not shown) illustrates a means of controlling the camera scans to compensate for misalignment of the images by adding bias voltages varying at colour field frequency to the vertical and horizontal yokes.