Patent GB-1285554-A (GB)
Title: Display means
Inventor: APPLEBY ROBERT MILSON
IPC: G09G1/18
Filed: 1968-07-08
Abstract: 1285554 Cathode-ray tube displays; television NATIONAL RESEARCH DEVELOPMENT CORP 8 Oct 1969 [8 July 1968] 32578/68 Headings H4F and H4T A controlled distortion of a cathode-ray tube television display is produced by modification of the line and frame deflection waveforms. The modification may include introducing different types and degrees of non-linearity, varying the amplitude and adding "shift" voltages to vary the position of the resulting trace on the screen. The invention is described in connection with a system for comparing different but related objects (e.g. human skulls, fossils &c. from different periods of time) and operates by producing a television picture of such object and comparing this visually with a photographic transparency of a related object placed in front of the displayed picture whilst calibrated controls are manually adjusted to modify the deflection waveforms until the distorted displayed object matches the transparency. The display may also include an electronically generated rectilinear grid (which is also distorted by the scan modification) and the grid alone or the pisture plus grid may be photographed to form a permanent record. The overall system is shown in Figs, 1 and 1a and includes line and frame deflection modification circuitry. Referring to the line circuitry, a linear sawtooth time base generator 1 supplies three function generators 50, 52, 54, the outputs of which are selected by a function selector 64 and fed, together with the output of the time base generator, to the Linearity Modifier 42. The function generators may, e.g., produce sinusoidal and semi-sinusoidal waves of various frequencies locked to line frequency and the selected function is subtracted from the line sawtooth in difference amplifier 66 and the result of the subtration fed to a multiplier 68 in which it is multiplied by the output of a control amplifier 70 supplied from a function generator 56 looked to the frame sawtooth deflection generator 48a. The function generator 56 may supply zero voltage, a constant voltage or a variable voltage and the output of the multiplier 68 (if any) is summed in amplifier 74 with the line sawtooth. Amplifier 74 then supplies a time-base waveform the linearity of which may be varied in a controlled manner but which does not vary in duration or amplitude. The output from amplifier 74 is then fed to the Amplitude Modifier 44 in which it is multiplied in multiplier 76 by the output of a control amplifier 78 supplied from a frame locked function generator 58 the output of which may be zero, a constant or a variable and the result of such multiplication (if any) is then fed to a summing amplifier 82 in the Position Modifier 46. Amplifier 82 has, as second input, the output of a multiplier 84 in which the output of a frame locked function generator 60 is multiplied by the output of a control amplifier 86 supplied with an input from a frame locked function generator 62 and the output of amplifier is then fed to the deflection amplifier 34. The latter thus provides a line deflection waveform the linearity of which is controllable by amplifier 70, the amplitude, by amplifier 78 and the position (shift) by amplifier 86, in conjunction with function selector 64 external control inputs being provided to each of the amplifiers for this purpose. Other function generators may be "switched-in" to replace the function generators described above in both the line and the (identically operating) frame deflection circuits. The display is produced from either a received television transmission or from video signals produced by a camera 20 "viewing" the object or a picture thereof. As shown, the output signals from camera 20, in addition to being fed to a monitor 22 are supplied via a video amplifier 26, in which they are combined with signals from the marker generator 28, producing the rectilinear grid, and via a further video amplifier 30 to the display tube 32 in front of which a photographic transparency of a related object is positioned. Figs. 5 to 10 illustrate the application of the invention to comparison of types of fish by distorting the display of first fish (Figs. 5, 7 and 9) to fit them to second fish, Figs. 6, 8 and 10, respectively.