GB886087A - Apparatus for controlling television signals - Google Patents

Abstract

886,087. Television. FERNSEH G.m.b.H Nov. 5, 1959 [Nov. 5, 1958], No. 29064/61. Divided out of 886,086. Class 40(3). Relates to apparatus, Fig. 2, for controlling television signals comprising means for applying television signals from each of two television scanners 1, 2 to a combining circuit 5 by way of gate circuits 3, 4 which are opened alternately by the action of a keying signal produced by scanning a master pattern 7 by means of a third television scanner 8. The signal from the combining circuit represents a composite image in which the scene viewed by the first of two scanners is replaced by the scene viewed by the second of the two scanners over an area determined by the master pattern scanned by the third scanner. In accordance with the invention the phase of the keying signal relative to the gated televisionsignals is arranged to -be varied, in order to permit the position of the area to be adjusted by applying synchronising impulses from source 35 to trigger the scans in the third scanner via adjustable delay means 36. In one arrangement, Fig. 3, the original synchronizing signals are applied to generate a sawtooth wave -M which is limited at an adjustable level 37 to generate a square wave N. Differentiation as at O and selection of the positive-going pulses P enables delayed blanking and synchronizing pulses Q and R to be developed. The amount of delay is varied by adjustment of limiting level 37. Similar arrangements are provided for line and frame synchronization. The two delay adjustments are preferably controlled by a common "joy-stick" type of control. An impulse generator 22, mixer 23 and limiter stage 25 are provided to introduce reference level pulses into the keying signal during the blanking intervals which function to set the trigger level of a phase-splitting stage 10 which provides oppositely phased versions of the keying signal for control of the gate 'circuits 3, 4. The size of the inlay area may be varied by controlling the amplitudes of the scan signals in scanner 8. As an alternative to varying the area size by variation of raster size, the size of the image of the master patternpresented to the third scanner may be varied either by varying the distance of the pattern from the scanner or by use of a lens system of variable magnification. Reference is made to the rotation of the area, this being brought about either by rotating the pattern in a plane perpendicular to the optical axis of the: third scanner, or by the use in the scanner of a pick-up tube including an image section in which the electron image may be rotated. Preferably a number of different master patterns may be provided which may be carried by suitable members to permit their introduction into the optical path of the third scanner when required.