Patent GB-967286-A (GB)
Title: Composite display system
IPC: H04N3/30
Filed: 1962-12-11
Abstract: 967,286. Radar; television. RAYTHEON CO. Dec. 11, 1962 [Dec. 29, 1961], No. 46792/62. Headings H4D and H4F. Alpha-numeric characters and/or other symbols are produced on a line scanned raster display (which is also modulated by conventional video signals) by means of appropriately timed scan intensity-modifying pulses controlled by the raster synchronizing pulses. The invention is described in connection with an airport surveillance radar system in which video signals producing a P.P.I. display 24 (Fig. 1) are supplied via a scan converter 26 to a rectangular raster display device 30 on which identification symbols &c. for each target are also displayed. The scan intensity-modifying pulses are produced by a generator 32 and the position in the rectangular raster in which the symbols are produced is controlled by a device 34. Fig. 2 shows the arrangement for the production of the letter F which, as shown in Fig. 7, requires a maximum of seven brightening pulses A to G in the first line scan and a maximum of twelve brightening pulses over a vertical height of twelve lines (six in each " odd " field and six in each " even " field). As shown, an " OR " gate 48 responsive to the positively going portion of a pulse 47 derived from the vertical positioning pulse 33 (the time occurrence of which may be adjusted by the device 34 feeds a counter 52 and produces, via AND gate 66, a " start " pulse which together with the horizontal synchronizing pulses 43 of the rectangular raster display opens AND gate 50. Successive pulses 43 are then fed to counter 52, the output from the various stages of which are fed to AND gates 54, 56, 58, 60, 62, 64. Gate 54 responds to the first pulse 43 and supplies a pulse to OR gate 68, the output of which is fed via OR gate 72 to AND gate 92 and conditions the latter to supply an output, in response to a second input comprising a horizontal position pulse 35 (the time occurrence of which may also be adjusted by device 34) to the display device 30 which, act as a beam brightening pulse producing the spot A of Fig. 7. Also during the first horizontal line of the " odd " field, gate 54 supplies a pulse to AND gate 70 which is conditioned during the " odd " fields by rectangular wave 37 derived from the vertical synchronizing pulses 41 to pass a pulse to AND gates 80, 82, 84 and, via connection 75 and OR gate 76, to pass a pulse to AND gates 86, 88, 90. These gates then pass the horizontal position pulses 35 with suitable delays as determined by line 78 to display device 30 to produce the brightening pulses for positions B to G (Fig. 7). For the remaining six lines of the " odd " field gate 66 operates to hold gate 50 open so that during the occurrence of the next five successive horizontal synchronizing pulses 43 gates 56 to 64 operate successively to pass beam brightening control pulses to AND gate 92 which thus produces the vertical row of bright spots A (Fig. 7) on the " odd " lines, the pulse from gate 58 being unable to pass gate 74 since the latter is held off during the " odd " fields by waveform 39. On the occurrence of the next (seventh) horizontal synchronizing pulse 43 gate 66 operates to inhibit gate 50 and prevents further pulses 43 from being passed to counter 52 until the occurrence of the next vertical position pulse 33 which then starts the counting process for the " even " field. This repeats the procedure described above to produce brightening pulses for the spot A on " even " lines 1-E, 2-E and 4-E, 5-E, 6-E (Fig. 7). In the case of line 3-E additional spots in the positions B, C and D are required and these are produced by means of the output of gate 58 operating in response to the third " even " horizontal pulse 43 to produce a pulse which is fed via gate 74 (conditioned to conduct during " even " fields by waveform 39) and gate 76 to condition gates 86, 88, 90 to pass appropriately delayed pulses 35 to the display device.