Patent GB-1380188-A (GB)
Title: Visual display system
IPC: G09B9/30
Filed: 1972-07-17
Abstract: 1380188 Television SINGER CO 17 July 1972 [21 July 1971] 33315/72 Heading H4F In a visual display system, in which a television picture signal generator is used to produce a picture on any part of a wide-angle display device, including a plurality of side-byside narrow-angle display units which receive horizontal sync. signals provided by a set of relatively phase displaced pulse trains so that a horizontal scan appears continuous across the wide-angle display, and the generator receives horizontal sync. signals provided by a further pulse train, the relative timing of the pulses in the set of pulse trains, on the one hand, and the further pulse train, on the other hand, is controlled by an input signal applied to a digital phalse shifter. The system is used in an aircraft simulator for pilot training. In Fig. 5a, W22, W23, W32, W33 represent display windows corresponding to separate CRT displays. Windows W11-W13, W21, W31 are "phantom" windows shown for explanation. The picture 51 may be positioned anywhere in the 1365 line matrix W11-W33. Fig. 4 shows the system in which are produced the appropriately related horizontal and vertical sync. and blanking signals for the camera and the display, and the video signals for controlling the position 81 at which the picture display starts. Clock 11 supplies 55À2825 MHz pulses to a counter 10, which produces an output and resets after 675 pulses (i.e. an 81À9 KHz pulse train), and to block 45 which includes a 1350 count counter and two sets of gates. Every second output pulse from counter 10 is applied on line 49 through the gates to the counter of block 45, the gates being selectively enabled by computer 41 so that each pulse on line 49 presets the counter to a count determined by computer 41 and corresponding to the horizontal position in the windows W11-W33 at which the picture display is required to begin. The counter in block 45 produces outputs on lines 61, 63 at counts of 540 and 1080, respectively, and these signals appear on lines 66, 68 as display horizontal sync. signals for the matrix columns W22, W32 and W23, W33, respectively. The 81À9 KHz output from counter 10 is applied to camera sync. generator 39 which produces the horizontal and vertical camera sync. signals. The 81À9 KHz signals are also applied to block 73, which is similar to block 45, and which counts these pulses to produce outputs on 77, 79 at positions appropriate to the production of a continuous vertical scan in the display matrix. The camera vertical sync. signals act through line 74 to reset the counter to the value preset by computer 41 corresponding to the vertical positioning of the display. The computer also produces information relating to the vertical and horizontal co-ordinates of the window (real or phantom) in which the picture begins, these being supplied on lines 83 to window decoder 85. Block 65 is a pulse shaping and translating circuit for making the high speed logic associated with counter 10 compatible with the logic used in the rest of the system. Video switching logic.-Fig. 7 shows the portion of blocks 85, 87 which relates to windows W12 and W22. To switch the video to phantom window W12, if the picture starts in that window, the display vertical sync. for row 1, camera vertical sync, and W12 selected signals are applied as inputs to NAND gate 95, causing bi-stable device 103 to switch. If the camera vertical sweep is in its active region and camera horizontal sync. pulses are present NAND gate 104 is enabled. This causes bi-stable device 113 to be set and produces the W12 video gating signal at 115, which is not used since W12 is a phantom window. Device 113 is reset by either the camera or the window horizontal blanking signal. It is also necessary for the video signals to be switch to W12 if W11 has just been active. This is achieved by pressure of W11 select, and horizontal sync. column 2, signals on lines 127, 129. Similarly the W22 video switching signal is produced if the picture starts in W22 or was present in W21. In addition the W22 signal is required if the picture was present in W12. This is achieved by taking the inverted output of device 113 and the W12 selected signals to produce an output from gate 133. If this coincides with a vertical sync. row 2 signal bi-stable device 139 is switched which has the same effect as switching 103A.