Patent GB-1517523-A (GB)
Title: Apparatus for the anamorphic transformation of images
IPC: A61B6/00
Filed: 1975-06-11
Abstract: 1517523 Cathode-ray tube circuits FRANCE MINISTRY OF POST & TELECOMMUNICATIONS 11 June 1975 [14 June 1974] 24957/75 Heading H4T The invention is directed to producing adjustable anamorphic transformation of televised images reproduced on a cathode-ray display tube and is particularly concerned with the production of the anamorphic transformation of neuro-radiological stereotaxis radiographic transparencies of the head although applications to the production of artistic effects in television or the cinema and to teaching are also envisaged. As shown in Fig. 3, the transparency 1 is illuminated by means 2 and analysed by a television camera 3 producing a video and synchsignal output. The latter is supplied over a cable terminated by a suitable means 33 to a video amplifier 9 the output of which is supplied either directly or via an inverter 10 to a video amplifier 12 of adjustable gain and thence via an impedance adaptor 13 and output 5 to the video signal input of a cathode-ray display tube 8. Additionally, the output of camera 3 is supplied to a synch-signal separator 14 providing respective horizontal and vertical synch-signal outputs 15, 16 for the control of respective horizontal and vertical sawtooth wave generators 17, 26, the outputs of which are supplied to respective sawtooth processing circuits 18, 27. The latter each provide two outputs of which 19, 28 supply sawtooth waveforms having slopes which may be adjusted by an operator and outputs 24, 31 supply signals from "intermediate" stages of the circuits 18, 27. The outputs 19, 28 comprising the slope adjustable waveforms are supplied via outputs 6 and 7 to the horizontal and vertical deflection inputs of the display tube 8 and are also fed via respective differentiators 20, 29 as inputs 21, 32 of a summer circuit 22 which also receives the outputs 24, 31 as inputs 25, 30. The output of the summer circuit 22 is fed to the gain control input of video amplifier 12, the components at inputs 21, 30 due to the differentiators 20, 29, operating to control the intensity of the display on tube 8 so as to ensure consistent intensity despite variations of deflection velocity due to changes in the slopes of the deflection waveforms and the components due to the inputs 25, 32 from the "intermediate" stages operating to cause the display of vertical and horizontal lines such as C1-C2, C5-C6, C7-C8 (Fig. 1) and C3-C4, C9-C10 (Fig. 2). Figs. 4 and 5 show details of the respective processing circuits 18 and 27 of Fig. 3. A horizontal frequency sawtooth wave a is supplied to an amplifier circuit 34 and a vertical frequency sawtooth wave is supplied to a similar amplifier circuit 64. The outputs of 34 and 64 comprising a symmetrical sawtooth wave as shown at b in respect of the horizontal circuit are supplied respectively to amplifier circuits 37, 39, 41 and 64, 65. The circuits 39, 41 and 64 act as threshold devices such that the "start" point of the sawtooth output such as shown by 72 in respect of the sawtooth output c of circuit 39 may be caused to occur at a position determined by adjustment of respective potentiometer 44, 46, 71. The output c of 39 is supplied to an "algebraic" amplifier 47 from which an output wave d is derived via potentiometer 51 and supplied to (summer) amplifier 37 to produce an output wave e determining the position of the first change in slope of the deflection waveform (f). In a similar manner an output from a second "algebraic" amplifier 54 determining the position of a second change in slope is combined with the output of summer 37 in a second summer amplifier 52 the output of which comprises the required horizontal deflection waveform f which is supplied to the display tube 8 via terminal 6. The vertical circuitry operates in similar manner to produce the required vertical deflection waveform g having only one change in slope and this waveform is supplied to the display tube 8 via terminal 7. The waveforms f and g are also supplied to respective differentiators 20, 29, the outputs of which comprise the inputs 21 and 30 to adder 22 of Fig. 3. Additionally, outputs derived from "intermediate" stages 39 and 41 are supplied to respective circuits 48, 55 to switch mono-stable circuits 60,. 62 (of similar time-constants) to their set state to provide the input 25 to adder 21 of Fig. 3, the output of threshold circuit 64 (Fig. 5) and mono-stable circuit 70 (of longer time-constant than that of the mono-stables 60, 62) acting in a similar manner to provide input 32 to adder 22.