Patent GB-1236971-A (GB)
Title: Information display systems incorporating multicolour cathode ray tubes
Inventor: BUDGEN RONALD PALLISTER
IPC: G06F3/0489
Filed: 1968-05-31
Abstract: 1,236,971. Electric digital calculators. FERRANTI Ltd. 29 May, 1969 [31 May, 1968], No. 26113/68. Heading G4A. [Also in Division H4] A multi-colour information display system comprises a standard colour T.V. tube 12 having a screen 13 of superimposed R.G.B. phosphor matrices scanned by electron beams from guns 14, 15, 16 through a conventional perforated shadow mask adjacent the screen. Frame and line scan generator 19 energizes deflection coils 18 to deflect the electron beams at a uniformly repetitive rate; the persistence time exceeding the sweep time, and an information signal source may comprise radar or sonar receiver or a simulator thereof, a light pen, a tracker ball, a manual keyboard or a computer; singly or in combination. A keyboard may supply two part interrelated digital signals of which colour defining signals C 1 , C 2  . . . C n  present singly are applied to colour/amplitude coder 20 (Fig. 2, not shown) to define n monochromatic displays on the screen by n signals of distinctive amplitudes referred to unity, which are passed over 21 to the grid 27 of the writing section 22 of a doubleended storage C.R.T. 23 whose beam position is controlled by deflection information signals XY synchronous with the colour defining signals, applied over D/A converters 26 to energize deflection coils 24. The beam intensity from gun 28 is controlled by grid 27 and is deflected across storage mesh 29 to establish variable amplitude charge patterns of long persistence corresponding to the input signals. A constant current electron beam from gun 31 scans the mesh 29 synchronously with the beams of the display tube 12 in response to deflection coils 32 energizes from generators 19 synchronized over leads 33, so that non-destructive read-out is effected simultaneously with, but at different rate to, the write-in, and the output signals are derived from a collector adjacent the storage mesh over lead 54, of amplitudes proportional to the charge pattern magnitude at the instantaneous position of the reading beam. These are decoded at 35 (Fig. 3) to energize guns 14, 15, 16 singly or in combination to reproduce the configurations of charge traces on mesh 29 in colour established by the magnitude of the charge. C/A coding is effected (Fig. 2, not shown) by n transistor current switches the amplitudes passed by which are established by corresponding emitter resistor loads and a tail voltage, while corresponding diodes are arranged so that the resistor current traverses either the transistor or the diode according to the value of the individual colour signal applied to the transistor base; one only of which is positive at any instant; the output voltage across a common collector load resistor then being inversely proportional to the appropriate emitter load resistor and thus defining the required colour. Amplitude/colour decoder 35 (Fig. 3) comprises n identical high-gain differential amplifier voltage comparators 1 to n, each of which receives signals readout from storage tube 23 over amplifier 42, and a corresponding incrementally varying reference voltage V 1  to V n  increasing in accordance with the respective colours to be defined. If the storage voltage is more positive than the reference voltage, transistor switch TC3 conducts to render output 1 to n positive and output #l to #n negative, and vice versa if reference voltage is more positive than storage voltage. The several comparator outputs are applied to respective double diode AND gates &1 to &n with the outputs 1, 2 to &1; 2, 3 to &2, &c. with output n and reference voltage + V applied to & n. An identical series of transistor switches T 1R  to T nR , T 1G  to T nG , T 1B  to T nB  is provided for each tube phosphor, with the output leads 36, 37, 38 connected to the B, G or R guns respectively, while the outputs of AND gates &1 to &n are conZected to the bases of transistors T 1  to T n  respectively, so that energizing signals are supplied to the appropriate guns to produce the required coded colour; the storage characteristics of tube 23 determining the available number of colours. For sonar or radar display the C/A coder 20 is omitted, and the amplitude contours of the signals are displayed in different colours, while markers from a manual keyboard may be interlacedly superimposed thereon; utilizing different colour sets. Inputs from pen-like devices may be applied to draw coloured traces; the colours being selected by computer or keyboard control. A tracker ball may be used wherein ball rotation in X and Y direction operates optical shutters whose impulses are digitally counted and applied to leads 25 to store the instantaneous ball position, whereby the path of the ball is drawn on the screen. Alternately a light pen may be used which comprises a photo-sensitive detector connected over a bundle of fibre optics to the pen tip, which is traced over a single colour raster displayed on screen 13 to develop pulses on illumination of the phosphor beneath the tip; the X co-ordinate of the pen being obtained by counting time movements between line time base commencement and the time of pulse generation, and the Y co-ordinate by counting lines from the start of a frame. Signals corresponding thereto are applied to inputs 25 to store the pen movement for future display.