CA1225145A - Television systems and subsystems therefore - Google Patents

Abstract

ABSTRACT
TELEVISION SYSTEMS AND SUBSYSTEMS THEREFOR
An image is scanned by a color camera (800-808) and the luminance representative signals (e.g. Green) of pairs of adjacent lines are summed and differenced in a processor 861. Color signals R,G,B and the sum signal (GS) are matrixed to form chrominance components and luminance components of a standard composite video signal (e.g. I,Q, YS for NTSC) in a matrix 812. One of the chrominance components (I) is comb filtered (1112) to remove portions of its frequency spectrum. The difference signal ( G .DELTA. ) is comb filtered (1122) to be inserted (1124) into the removed portions of the chrominance component (Fig 11).
A receiver (Fig 9) of such a composite signal comprises an adder (934) and a subtractor (935) together with a weighting circuit (935) for summing and differing the summed and differenced signals to reproduce the original luminance signals, which are then displayed on a display (921). In a compatible high definition system first ones (L1, L2) of the pairs of lines conform to a standard TV system (e.g. NTSC) and the second ones (L1A, L2A) are offset by e.g. ? of the standard interline spacing. In an example of the high definition system, the pairs of lines are sampled by a sinusoidal scanning path the samples from the lines being derived by a synchronous switch (618) (Fig. 6).
The difference signal (G .DELTA. ) is invisible on a conventional receiver but allows high vertical defintion on the receiver of the invention.

Description

Lowe According to one aspect of the invention specified in our co-pending Canadian Patent Application 408402, from which this application is divided, there is provided a television system including; image transducing means comprising means for producing signals representing the luminance of an image along scanning lines of a predetermined image scanning pattern; means for processing the luminance signals to produce signals repro-suntan thy difference in luminance between predetermined pairs of the lines and further luminance representative signals which, together with the difference signals, allow reproduction of the luminance signals of said pairs of lines;
and display means comprising means responsive to the difference signals and the further signals to reproduce the luminance signals of said pairs of lines and means for reproducing the image from said reproduced luminance signals An embodiment of at one aspect is concerned with a television system which provides increased vertical resolution and which is compatibly with a standard color television system such as NTSC or PAL. Standard NTSC
television for example skins lines per frame in the form of two sequential fields of 262 1/2 lines. The lines of each field interlace with the lines of the preceding and succeeding fields and the eye integrates these to reduce flicker. However, the line structure is still visible under certain circumstances, and is particularly visible on large-screen television displays viewed from a relatively close distance. The problem is made even more severe by the ultra-large pictures formed by projection-type television displays. The visibility of the line structure is surprising, considering that a composite NTSC signal actually comprises three simultaneous channels of information (one luminance, two chrominance) and therefore represents about 1500 lines per frame. The visibility results from the superposition of the R, G and B signals in triples. It is desirable to increase the effective vertical resolution or definition in a manner compatible with current standard television practice, so that broadcasting of high resolution signals cats begin ~225~

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immediately without seriously degrading the performance of standard television receivers currently in use, and yet be such that when processed by a receiver according to the invention they produce an improved high-resolution pucker In this embodiment of at one aspect the predetermined scanning pattern is such that corresponding first ones of the pairs of lines conform to the scanning pattern of a standard television system such as PAL or NTSC
10 both spatially and temporally.
The further luminance representative signals may be combined with color representative signals to form a standard composite video signal. Preferably a portion of the frequency spectrum of at least one of the chrominance 15 components of the composite signal is removed and the difference signal inserted into that potion.
According to the present invention there is provided d splay means for displaying an image represented by signals 20 representing the difference in luminance between predetermined pairs of lines of a predetermined image scanning pattern and further luminance representative signals, derived from signals representing the luminance of the pairs of lines and which together with the filter signals allow the reproduction of 25 the signals representing the luminance of the pairs of lines, the display means comprising means responsive to the differ-once signals and the further signals to reproduce the luminance signals of said pairs of lines and means for reproducing the image from said reproduced luminance signals.

Jo . . ,

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1 For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to thy accompanying drawings, in which:-1 FIGURES 1 and 2 illustrate, respectively, vertical and horizontal lines displayed by a raster, FIGURE 3 is a schematic diagram ox the optical portions of a color camera:
FIGURE 4 illustrates in more detail camera vidicons and circuit arrangements forming part of the camera of FIGURE 3;
FIGURE 5 is a schematic diagram showing pairs of raster lines:

FIGURE 6 is a schematic diagram of a portion of another camera:

FIGURE 7 is a block diagram of a circuit which Jay be used to process signals generated by the camera of FIGURE
I;
FIGURE 8 illustrates a system in which a convent tonal TV monitor receives signals generated by the arrange-mint of Figures 6 and 7 to produce a picture therefrom;

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1 FIGURE 9 illustrates a TV monitor adapted according to the invention for use in the arrangement of Figure 8 for producing improved pictures from signals generated by the arrangement of Figures 6 and 7;
FIGURE 10 illustrates time waveforms and frequency spectra useful in understanding certain aspects of signal burying;
FIGURE 11 is a block diagram of a color television 10 system in which high resolution signals are buried in the composite color signal, FIX E 12 is a block diagram of a color TV display monitor age-wording to toe invention useful in the system of Figure 11 for displaying images from composite color TV signals with buried high-1.5 definition components;
FIGURE 13 illustrates signal frequency spectra useful in understanding the arrangement ox FIGURE 12;
FIGURE 14 is a block diagram of yet another camera FIGURE 15 is a timing diagram aiding understanding of the camera of FIGURE 14;
; FIGURE 16 is a block diagram of a television monitor useful with the camera of Figure 14;
FIGURE 17 is a schematic block diagram of a 25 television broadcast receiver according to the invention;

FIGURE 18 is a block diagram of a television system according to a further aspect of the invention in which independent signals are multiplexed through fourth and fifth 30 signal channels within a composite color TV signal processing path; and FIGURE 19 is a receiver for signals generated in the arrangement of FIGURE 18.
.. .

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1 FIGURE 1 illustrates a raster having an aspect ratio with a height of three units and a width of fuller units.
The raster is scanned in the usual fashion by successive horizontal lines (not shown). Alternate light and dark vertical lines are displayed on the raster, The light and 5 dark lines are related to the frequency of the Sweeney being processed. The horizontal scanning time in NTSC is 63.5 microseconds of which approximately 10 microseconds is used for horizontal blanking, leaving approximately 53 micro-seconds as the duration of the active line scan. The 10 alternate light and dark lines formed on the raster in FIGURE 1 require positive- and negative-going signal excur-sons, the rate which is determined by the relative physical spacing of the lines. The luminance bandwidth of the television signal is effectively about 3 MHz as practiced in 15 receivers, and thus the highest frequency signal which cay pass through the band can go through a full cycle (one positive and one negative excursion of the luminance) in use. In 53 microseconds (eye duration of the active portion of one horizontal line) approximately 160 complete 20 cycles can take place. Thus, 160 black and 160 white lines can occur in one horizontal line, for a total of 320 television. lines in a complete horizontal scan. However, in accordance with standard television practice, the horizontal resolution must be multiplied by 3/4 in order to determine 25 the standard resolution (the resolution which would occur if the raster were square and had a width equal. to the height).
Thus, the horizontal resolution is about 240 television lines for a 3 MHz bandwidth, or approximately 80 television lines per megacycle. Using this criterion, the resolution in the 30 horizontal direction for a color signal component having a 1.5 MHz bandwidth is about 120 television lines.
In the vertical direction, each field consists of more than 250 scanned lines as suggested in FIGURE 2. The : color resolution in the vertical direction is much better 35 than in the horizontal direction, because the horizontal resolution is limited by the chrome channel bandwidth as :

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1 mentioned above to abut 120 television lines, whereas the vertical color resolution is not determined by the channel bandwidth but rather by the number of horizontal lines by which the picture is sampled in the vertical direction.
Consequently, the color resolution in the vertical direction 5 such exceeds the color resolution in the horizontal direction, yet the horizontal color resolution is adequate. On the other hand ! as mentioned previously the vertical luminance resolution is not adequate since a line structure can be seen in large picture displays.
FIGURE 3 illustrates one embodiment of a high-resolution camera, In FIGURE 3, light from a scene illustrated as an arrow 301 passes through optics illustrated as a block 302 and into a color-splitting prism 304. Green light as is 15 known passes straight through the prism and through further optics 306 as required for focusing an image reflected by a half-silvered mirror 308 onto the faceplate of a camera tube or vidicon 12 and directly through mirror 30~ onto the faceplate of a vidicon 10. The red components of the light 20 from the scene are separated by prism 304 and are focused by optics 319 onto the faceplate of vidicon 310 through half-silvered mirror 311 and by way of reflection from the front surface of mirror 311 onto the faceplate of vidicon 312.
The blue light is similarly separated by prism 304, focused 25 by optics 314, and half-silvered mirror 316 reflects an image onto the faceplate of camera tube 318 and passes an image to the faceplate of camera tube 320. FIGURE 4 illustrates in more detail the circuitry associated with the vidicon 10 and 12, which are representative of any of the 30 pairs. In FIGURE 4, two matched vidicons or camera tubes -: 10 and 12 scan rasters 14 and 16 on the photosensitive faces thereof under the influence of a deflection drive circuit 18 which causes an alternating current through deflection windings illustrated as coils 20 and 22. Identical images 35 are formed on rasters 14, 16 by optical means such as described in conjunction with FIGURE 3 which may include a , .

I 1;;~2~ ; RCA ~7253 DIVE s 1 half-silvered mirror. A target supply voltage is applied through resistors 24 aureole 26 to the targets of tubes 10 and 12, respectively.
The signal from each target is coupled to a preamplifier. As described, identical video signals would be derived from each camera tube. As shown in FIGURE 4, a small fixed current is cay d to flow in a resistor 28 5 which is blocked from winding 20 by a capacitor 30, forcing the direct current to flow through winding 22. This small additional current is selected so as to offset the scanning lines of raster 14 slightly compared with the raster lines scanned by tube 12 on raster 16. The amount of current is selected to offset raster 14 vertically by 1/4 of 10 the distance between adjacent scan lines. FIGURE 5 shows the positions of the scan lines generated by tube 10 and 12 relative to the image being scanned. The image being scanned for purposes of this explanation may be considered to be the single rectangle 500, although the image actually occurs on two faceplates and may not be rectangular. Scan line 15 501 is produced by tube 10 simultaneously with scan line 502 produced by tube 12. Since the scan lines are in slightly diEferen~: positions relative to the image, the video produced during scanning of adjacent lines 501 and 502 may be different; although due to the physical proximity of the lines on tune image the video will often be the Syria. Tube 10 20 then scans line 503 simultaneously with the scanning by tube 12 of line 504. The separation between lines 502 and 503 is selected so that on the next field following the one shown, tube 10 can scan a raster line in the position shown by dotted line 506 and tube 12 can scan a raster line in the position shown by dotted line 40i3, thus providing interleaved 25 scanning or interlace over a frame (two-field) interval. Ibis 10 and 12 continue scanning across the identical images on their photosensitive screens with lines that are slightly offset until each produces 262 1/2 lines, whereupon the field ends and the next field begins. In all, 525 lines are scanned per field and 1050 lines are scanned per frame for the 30 apparatus of ElGt~RE 4. In the apparatus of FIGURE 3, the tubes 310, 10 and 320 are arranged to commonly scan ~iraSstter of 262l2 lines through tune image per field, whilst all the tubes 312, 12 and 318 are arranged to commonly scan a second raster of 262-~ lines through the image per field, the second Easter being offset from the first by ego 1 of the distance 35 between adjacent scan lines of the first raster. Thus the whole apparatus of FIGLlRE 3 also scans 1050 lines per frame.

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Resistor 28 and capacitor 30 illustrated in FIGURE 3 may be deleted from the circuit, provided that the images formed on the transparent faceplates of the vidicons are of set physically by a small amount so that identical raster scans can produce video from slightly different portions of the image offset by the amount described.
FIGURE 6 illustrates another embodiment of an arrangement for producing two simultaneous video signals representative of slightly different portions of .

: 25 : 30 . I:

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1 . . I ARC 77,253 MY B
monochromatic image. The arrangement ox FIGURE 6 may be used three times in conjunction with a color splitting prism to form simultaneous I, G and B signals. In FIGURE
6, a vidicon 600 has a faceplate-602 onto which an image is focused by optics, not shown. Vertical and horizontal deflection windings designated generally as 604 and driven by suitable deflection circuits cause the electron beam of . the vidicon to scan a raster at a high horizontal rate such as 15, 750 Ho and to scan vertically at a slower rate such as 60 Ho. An auxiliary deflection winding 606 is coupled to a wobble clock generator 614 and is oriented to ; produce vertical deflection of the electron beam. Wobble : generator 608 produces a signal at a rate which is high (substantially higher than the highest video frequency) relative to the horizontal deflection rate and of sufficient amplitude to cause a pealc-to-peak vertical deflection equal to 1/4 of the separation between lines.
As described in conjunction with FIGURE 5, this allows for interlaced scanning with the lines of the preceding and succeeding fields. The vertical deflection caused by the auxiliary windings is illustrated by dotted line 257, aye on the face of kinescope 600. Thus, each scan line traces a sinuous path across the raster. The upper excursions of each path are labeled with the line number (e.g. Lo, Lo...) and the lower extremity of each path is labeled with the line number and the suffix "A". Video signal is continuously produced at target contact 604 during scan and is coupled to synchronous detectors 606 and 608.
Synchronous detectors 606 and 608 can be represented as controllable mechanical switches 606 and 608 controlled by the clock signal generator. The wobble clock signal applied to detector 608 is phase inverted so that switches 606 and 608 close alternately. Switch 606 closes during the upward excursion of the sinuously deflected scan path, and switch 608 closes during the downward excursions of the sinuous path. The video signal received at target 604 during the upward excursions appears at the output of switch 606, and the video signal .. . .

., I
--lo- RCA 77,253 DIVE s occurring during the downward excursions appears at the output of switch 608. The switching signal is filtered by low-pass filters 610 and 612 to produce filtered signals S Lo, Lo, Lo... at output terminal 614 and Lie, Lea, Lea... at output terminal 616. Thus, simultaneous lines of information are available representing scans of the image displaced by 1/4 of the interline separation. These simultaneous lines Lo, Lea; Lo, L2A...correspond to lines I 501, 502; 503, 504..... illustrated in FIGURE 5 and the filtered video at output terminals 614, 616 is essentially indistinguishable from that produced in the arrangement of FIGURE 7 illustrates circuitry for producing lo from the video from simultaneously occurring horizontal scan lines separated by a small vertical distance, however they may be generated, a signal representative of the sum (s) or average of two adjacent scan lines and another signal (~) representative of the difference. In FIGURE: 7, input terminal 702 is adapted to be coupled for example to terminal 614 of the arrangement of FIGURE 6 for receiving video from one scan line, while terminal 704 is adapted to be coupled to terminal 616 for receiving video from a proximate scan line. Terminal 702 is coupled to the non-inverting nuts of an adder 706 and a subtracter ordifferencing circuit 708. Terminal 704 is coupled to another non inverting input of adder 706 and to an inverting input of subtracter 708. The output of adder 706 is a signal having approximately twice the amplitude of either input signal, and therefore a divide-hy-two attenuator 710 is coupled to the output to normalize the output signal of adder 706 to produce at output terminal 712 of the attenuator an averaged signal (S) substantially equivalent to the signal which would have been produced by a single scan line physically located between lines Lo, Lea; Lo, LEA... Subtracter 708 subtracts the values of the two signals to produce at terminal 714 a difference signal (~) representative only of the high-frequency vertical resolution. For example, if lines Lo and Lea are I
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identical, subtracter 708 produces no output signal. This indicates that there is no change in the signal between s Lo and Lea and therefore indicates that the available vertical resolution is not being used.
Similarly, to existence of difference signal at the Output of subtracter 708 indicates that the resolution is being used by a vertical transition Okay in somewhere between the line pairs. The average signal S thus produced is totally equivalent to the signal produced by a conventional monochrome camera viewing the same scene.
The arrangement of FIGURES 6 and 7 together differs from the arrangement of a vertical aperture corrector in that the slim and difference signals are derived from independent pairs of lines (i.e., Lo, Lea, Lo, LEA...) whereas in aperture correctors the lines are processed in sequential pairs including a previously processed line ill, Lea; Lea, Lo; Lo ha...). FIGURE 8 depicts a color television system in which a conventional 525 lines-per-frame display unit receives signals generated by the arrangement of FIGURE 6. In FIGURE 8, light from an object not shown passes through optics ~00 at the left of the FIGURE and is split in-to red, green and blue components by a color splitting prism 802. The red and blue components fall upon the faceplates of conventional single vidicons 806 and 808, respectively, which in turn produce 525 line-per-frame red and blue signals. The green light from prism 802 falls upon the faceplate of a vidicon 600. Vidicon 600 is operated in a manner described in conjunction with FIGURE 6, with an auxiliary deflection winding 606 driven by a clock signal generator 614 to produce video which is applied to a synchronous demodulator and processor 618 of signal processor 861 for demodulation into Lo, Lo, Lyon one output conductor and into Lea, LEA, Lyon another output conductor. The demodulated output signals are coupled to a summing and differencing circuit 700 of processor ~61 for generation f green sum GO and green difference (Go) signals. The green sum signal GO and the red and blue signals are :~2Z~ 5 -12- RCA 77,253 DIVE B
applied to a matrix 812. As mentioned, the sum green signal is equivalent to the Green signal produced by a conventionally operated vidicon, and therefore matrix 812 produces a luminance sum signal YE which is applied to an input terminal of an adder 814, and also produces I and Q chrominance signals which are applied as is known to a quadrature muddler 816 for amplitude modulation of the creaminess signals in a quadrature manner onto a color I sub carrier signal applied from a generator 818.
Modtllated chrominance information is applied to a second input of adder 814 to form a sum composite video signal (YS+C ) .
The clock signals from generator 614 are applied to a sync and blanking signal generator 616 which produces standard sync and blanking signals which are applied to a block 818 for controlling the time of insertion of the appropriate sync and blanking voltages into the sum composite video signal. At the output of block 8:L8, a complete composite color television signal is available which may be applied to a conventional color monitor 820 for use in the usual manner. It should be noted that the (delta) signal produced by processor 618 was not necessary for this normal operation. Thus, even if the signal were coupled to color monitor 820 as by a conductor illustrated as dotted line 822, monitor 820 having no means for processing the additional information would simply ignore it and produce a standard-resolution signal in the usual manner.
In accordance with the invention, a color monitor operated in a system such as that illustrated in FIGURE 8 may be modified to utilize the difference signal GO to produce a high-resolution signal.
In FIGURE 9, a monitor receives composite color television signals at an input terminal 900 and difference signals Go derived from the green-representative video at an input terminal 902. The composite signal is applied to a sync separator 904 which produces vertical and horizontal sync signals. The horizontal sync signals are I
.. . .

I
1 -13- RCA 77,253 DIVE By applied to a phase comparator 906 together with horizorltal oscillator signals from a horizontal vacillator 9Q8 of a phas~-locked loop (PLY 910 including a loop filter 912.
5 PULL 910 locks the horiæontal-rate signals of. oscillator Tao the horizontal sync signals extracted from the composite video. A vertical-rate signal is produced by 'a vertical deflection portion' of deflection block 916 which for' this purpose may receive vertical signals from a 10 vertical count-down circuit 924 driven by horizontal-rate signals from oscillator 908 (60Hz in this particular embodiment) which may be locked to the horizontal rate.
The separated vertical sync signal is applied to count-down 914 to lock the phase of the vertical-rate signal applied to deflection circuit 916. Vertical and horizontal deflection circuit 916 is coupled in known fashion by a deflection yoke (not Sheehan) to a kinescope g21 .
A wobble clock generator 924 is coupled in a PULL
918 including a phase comparator 920 coupled to horizontal oscillator 908 and producing control signals filtered by loop filter 922. PULL 918 also includes a frequency divider 926 for dividing the wobble clock frequency into the range of the horizontal oscillator frequency so that US the wobble cluck frequency is locked to a multiple of the horizontal oscillator frequency. The wobble clock signal is applied to' an auxiliary deflection winding 928 coupled to kinescope 921 to provide a small amount of vertical 'deflection in a manner similar to that described in conjunction, with FIGURE 6. The wobble clock signal is also applied to synchronous demodulator 938 to control the operation of synchronous switch 940. It should be noted that wobble clock 924 need not be locked to the horizontal oscillator frequency and need bear no special relationship to the original wobble clock signal. So long as the .
phasing of the synchronous demodulator and the polarity of the scanned deviation caused by the monitor wobble clock are proE)erly.established when the monitor is manufactured, no further synchronization is required However, in order .

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to reduce Owe visibility of beats which Jay occur lbet~een low-level distortion introduced by the synchr~rlous modulators and demodulator, it sway Ire advant~qeous to 6 lock the wobble clock it the receiver to the wobble clock at the transmitter by relatillg the receiver wobble frequency to the horizontal oscillator frequency as illustrated in FIGURE 9, and also similarly locking the source Diablo clock or possibly by locking to other system 10 rates icky as the color ~;ubcarricr rate.
The composite color television signal from which the sync has been removed is applied to a lurker plotting filter 930 of known type wow separates the luminance information from the chrominance information.
15 The chrominance information is applied by conventional color signal processing circuit 931 to an input of a video drive circuit 932, the output of which is coupled to the control electrodes of kinescope 92.l~ Ike luminance information YE representing the averaged signal S = ill Lea) /2 (Lo ALLEN LNA)/2.. is coupled to the non-inverting inputs of a summer 934 and a subtracter circuit 936 of a synchronous demodulator 938. The difference signal Go representing LO - LEA) generated at the difference output 714 of the summing differencing circuit 700 of Figure 7 or of Figure 8 is applied by way of terminal 902 and divide by 2 the attenuator 935 to the non-inverting input terminal of summing circuit 934 and to the inverting input terminal of differencing circuit 936. m e output of summing circuit 934 is the sum of two 3b video signals YE Go /2 and represents luminance of line Lo, L2,LN, and is applied to a terminal of single pole, double throw switch 940 corltrolled at the wobble clock rate. The differencing circuit produces signals Yoga I
representing luminance of lines Lea, LILLIAN and is applied to the other terminal of switch 940. The signal at the output of White 940 is a recreation of the high definition I- luminance signal LO, LEA derived from the original scanning by vidicon 600 in its sinus manner.

., --15- RCA 77 I DIVE Jo lye reconstituted YE high definition signal is applied to further luminance processing illu~tr~ed as A bloc 94~ and is then applies to the second input of video drive circuit 932 fox matrixing with 5 the hrominal~ce signal from filter 930 to produce the signal for display on kinescope I
In operation, the high-res~lution monitor of the arrangement of IRE 9 reconstitutes thy hoarsely n signal from the composite color television signal derived 10 from ye YE signal together wit ye Go signal produce on a separate channel to generate a signal hiving 5~5 lines per field and 1050 lines per frame.
As so far described, the high-resoluti~rl system requires four independent input channels; the luminance, 15 sync and blanking signals at baseb~nd constitute a first channel; the I signal frequency-interleaved with the luminance is a second channel; the Q signal also interleaved with luminance jut in phase quadrature with the I signal constitutes a third channel; and the I difference signal on a separate conductor is the fourth channel. While such an arrangement may be perfectly : satisfactory in a studio, the extra conductor for carrying the difference signal is not suitable for ordinary broadcast use as for broadcast service to multitudes 25 standard NTSC broadcast receivers.
overcome that problem the diaphanous signal is inserted into or hidden within (multiplexed into) a portion of the chrominance signal. It is ordinarily true aye a color transition is accompanied by a luminance 30 transition. Subjectively, the luminance component of the transition is more important than the chrominance component. Consequently, some chrominance errors are acceptable in regions of rapid luminance changes.
Advantage is taken of this subjective effect to form a 35 fourth channel within a standard three-channel composite television signal such as an NTSC or PAL signal through which the luminance difference signal can be transmitter in a compatible manner.
Jo ' .

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Flogger lo illustrates a time-domain base band luminance signal 1000 representing recurrent lines of information having horizontal blanking intervals T0-Tl, T2-T3. Instead of luminance signal 1000 may be a base band color difference signal. During the active line interval, a sinusoidal signal lD01 occurs which is in-phase from line to line. The signal illustrated has five complete sinusoidal cycles during the active portion of the line and would result in a raster display of five vertical black lines interleaved with five vertical white lines five vertical patterns of alternating or different color in the case of color difference signals. The frequency NfH of such a sine wave would be approximately 2 M~lz. FIGURE lob illustrates the spectral composition of the video 'signal 1000. As illustrated, the spectrum includes a single major spectral line 1002 at frequency NO together with minor size lobes (N-l) oh and Null at 15 Countervails from I FIGURE lo illustrate a video waveform 1004 similar to signal 1000 in which the sine wave is out-of-phase from line to line. This is in effect a suppressed-carrier signal, in which the carrier at frequency NFH is suppressed as illustrated by the dotted line in FIGURE lode and the spectral energy appears in the I form of the 15 Claus sidebands. When a camera views a vertical pattern such as a picket fence and a zoom lens is used to change the number of cycles in the pattern being viewed, the number of pickets in the pattern changes continuously from one whole number to another, but the spectral energy does not change frequency smoothly with changes in the number of cycles in the recurrent pattern.
Rather, as a result of the recurrent sampling at the horizontal rate, energy appears only at multiples of the horizontal frequency, with one spectral line decreasing if I energy while another increases as the nurser of cycles in the recurrent pattern is changed. FIGURE lye illustrates a spectral line 1008 resulting from a raster pattern which in the vertical direction consists of alternate light and dark horizontal lines. As the number of lines in the . .:

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1 raster increases, spectral line 1008 moves to the right, Jo a position representative of a higher frequency.
Because of the horizontal-rate sampling of the raster, spectral line 1008 also appears as sidebands of horizontal-rate carriers. Thus, spectral lines 1010 and 1012 are the lower and upper sidebands, respectively, of OH which correspond to spectral line 1008. As can be seen, the high-definition high frequency vertical-direction signal is concentrated around multiples 10 of half the line rate; that is, interspersed between multiples of the line rate as illustrated by the regions OH illustrated in FIGURE 10f. Ordinary pictures do not consist only of single vertical or horizontal patterns.
Rather, they contain signals at many frequencies resulting from vertical and horizontal characteristics of the scene being viewed. FIGURE 10f also shows the usual spectral energy pattern in an average picture.
As mentioned, -the vertical color resolution in a standard NTSC picture exceeds the horizontal color resolution. Consequently, in the vertical direction there lo excess color resolution which is not necessary for display of an acceptable picture.
The excess vertical resolution is removed from a color signal and the region thus cleared in the spectrum is used for a fourth channel through which the high-definition luminance-related signal may be transmitted. The excess vertical color resolution is removed by removing signal from the region OH illustrated in FIGURE 10f.
FIGURE 11 illustrates in block diagram form an arrangement for creating a fourth channel within an NTSC signal processing channel through which additional information can be transmitted.
In the particular embodiment shown, the additional information is the high definition luminance-related difference signal Go derived from successive green lines.
The arrangement of Figure 11 is generally similar to the arrangement of FIGURE 8, and elements corresponding to . .

SLY
1 ' -18- RCA 77,253 DIVE s those in FIGURE B are designated by the same reference numeral. The YE signal from matrix 812 in the center of the FIGURE 11 is applied to summing circuit 814 through an additional delay circuit 1102 for the purpose of causing the YE signal to arrive at summer 814 at the same time as the modulated chrominance signal. Similarly, the Q signal from matrix 8i2 is applied to a modulator 1104 of quadrature modulator 816 (lower right of FIGURE) by way of a conventional 0.5 MHz low-pass filter 1106 end a delay circuit 1108. Delay 1108 is selected to cause the modulated Q signal to arrive at a summing circuit 1110 (part of quadrature modulator) simultaneously with the modulated I signal.
The I signal produced by matrix 812 in pa conventional manner from R, GO and B signals is applied directly -to the input terminals of a summing circuit 1114 and to another input of summing circuit 1114 by way of a lo delay 1116. Summer 1114 and delay 1116 together constitute a comb filter 1112. The transmission characteristic of filter 1112 is illustrated by solid line 1014 of FIGURE log It will be noted that response 1014 is a maximum at zero frequency and therefore filter 112 is a low-pass comb filter. Nulls occur in response 1014 at frequencies corresponding to frequency range Ill illustrated in FIGURE lo within which frequency range the vertical high-resolution signals occur. Consequently, the I signal leaving filter 1112 has at spectral response generally similar to that shown in FIGURE lo, which as can be seen is very similar to that in FIGURE lo except for attemlation or complete removal of the high-frequency portions. Filter 1116 thus clears out of the I signal a high-resolution portion into which another signal can be inserted.
Difference signal Go is applied directly to an input of a subtracter 1118 and is also applied to a second inptlt of sltbtractor 1118 by way of a lo delay 1120.
Together, s~lbtractor 1118 and delay 1120 constitute a high-pass comb filter 1122 having a transmission response :.

~2S~5 . 1 -19- RCA 77,253 DIVE s characteristic similar to that illustrated by dote line 1016 of FIGURE 109. This response allows Go signals to pass through filter 1122 when within the frequency range of those signals removed from the I signal by filter 1112, and prevents passage there through when thy Go signals are in the frequerlcy range of the I signals passing through filter 1112.
The low-pass filtered I and high-pass filtered Go signals are applied to the inputs of a summing circuit 1124 so as to frequency interleave the signals. The Go signal only occurs when there is a transition in the G
signal from one horizontal line to the next, as mentioned.
Vertical color transitions, will very often be accompanied by luminance transitions, and the G signal is the' principal constituent of the luminance. Consequently, the Go signal being added to the I signal will most often occur only in the regioll of a fast vertical color transition. The presence of the Go signal within -the I
signal may affect the color rendition of a conventional display but the Go sigllal, being at its maximum value during the fastest color transitions, has the greatest effect only during those times when it is least visible.
The combined I and signals are coupled from I summing circuit 1124 to a modulator 1126 by way of a conventional 1.5 MHz low-pass filter 1128 such as is Connally used for limiting the I bandwidth. Modulators 1104 and 1126 receive mutually phase-shifted signals from a sub carrier generator 818, onto which each modulator amplitude modulates its input signal and the resulting mutually quadrature-modulated Q and I-interleaved-with Go -signals are summed in summing circuit 1110 from which they are coupled to an adder 814 to be added to the YE signal.
Natalie, maximum utility of the resultant composite sum color video television signal including difference signals is achieved only by a display monitor capable of extracting the difference signal from the I signal FIGURE 12 illustrates a portion of a monitor adapted according to the present invention for extracting the difference signal, however S
; -20- RCA 77,253 DIVE B
derived, from the I signal. FIGURE I is generally ' similar to FIGURE 9, and corresponding elements have - either the same reference number or a reference number containing as a prefix the reference number of the corresponding element of FIGURE 9. In FIGURE I a composite color television signal including a difference signal buried within the I channel as described in conjunction with FIGURE 11 is applied at terminal 900 to a sync separator 904 in which vertical and horizontal sync signals are separated. The spectrum of the composite signal is shown in simplified form in FIGURE aye in which the solid lines represent Y and the dotted lines represent modulated chrominance signals with the location of the difference signals shown as I. As can be seen, the difference signal in the chrome signal occurs generally near the frequency of the Y signal. The separated horizontal sync signals from separator 904 are applied to horizontal oscillator 910 for generating horizontal sync signals which are applied to a wobble clock generator 918 and which are also applied together with the separated vertical sync signals -to a deflection apparatus illustrated as a block 91~0. Wobble generator 918 , generates wobble signals which are applied to auxiliary deflection coil 923 associated with kinescope 921 for causing a small vertical deviation of each scan line as described in conjunction with FIGURE 6. The wobble signals are also applied to a wobble modulator 938 to control the synchronous switch snot shown in FIGURE 12) by which the YE signal is alternated at the wobble rate to produce two lines of video for the high-definition display. Composite video from which the sync has been separated is applied from sync separator 904 to a luma-chroma splitting filter 930 and to a burst separator and oscillator 9311. Burst separator and oscillator 9311 samples the burst signal in known fashion and generates two quadrature sub carrier signals for application to a Q
demodulator 9312 and I demodulator 9315. .

1 ' -21- RCA 77,253 MY
The composite video signal applied to splitting filter is applied therein to a luminance filter 9301 the response of which is complimentary to that of a - 5 chrominance filter 9304. Luminance filter 9301 includes a I delay 9302 and a summing circuit 9303 for producing a - transmission response similar to 1004 of FIGURE log while chrome filter- 9304 includes a lo delay 9305 and a I, subtracting circuit 9306 for producing complementary response 1016. the luminance output of filter 9301 illustrated in FIGURE 13b is applied to the Y input of wobble modulator 938 by way of a delay circuit 9420 and an adder 1210. The separated Y signal includes residual a signal occurring at frequencies near the peaks of the lo response of filter 9301. Delay circuit 9420 delays the Y
signal applied to modulator 938 so that it arrives at the ; Salle time as the corresponding signal.
At the OUtpllt of filter 9304, the chro~inance (C) plus difference signal (KIWI) is in the form ox end Q signals quadrature--nlodulated onto a suppressed sub carrier. The separated Crimea FOGGIER 13c ? its contaminated by residual Y signal as shown by the small letters Y at the principal Y frequencies. The separated Cat includes signals within the upper freqllerlcy'portions I' I of the chrome signal sidebands. The I signal is applied ' to a second input of Q demodulator 9312 for demodulation, and the resulting base band Q signal is passed through a low-pass Q filter 9313 and a delay circuit 9314 to the Q
input of a processing and video drive circuit 9320.
I - The I signal of FIGURE 13c at the output of filter 9304 is also applied (by way of a band pass filter 1232 for removing residual Y as in FIGURE 13h) to an I
demodulator 9315 where it is demodulated with reference to the sub carrier signal from burst oscillator 9311. At the I output of demodulator 9315 base band I signal frequency--interleaved with signal is regenerated with some Y
signal contamination as illustrated in FIGURE 13d. This signal is passed through a low-pass I filter 9316 for removal of high-frequency components and is applied to an : 40 I S
. 1 ' . -22- .RCA 77,253 DIVE s I separating circuit 1212 including a whops comb - filter 1214 and a low-pass comb filter 1216. Whops comb filter 1214 includes a lo delay circuit 1218 and a subtracter 1220 for separating the signal FIGURE eye from the deTnodulated I Low-pass comb filter 1216 . includes a lo delay circuit 1222 and a.su~ning circuit 1224 o'er separating the I signal from the demodulated It signal. The separated 1 signal is applied to a third input of processing and video drive circuit 9320 and is combined therein with the Y and Q signals to produce RC7B
drive signals for application to the kinescope.
he signal produced at the output of high-pass comb filter 1214 is applied to a second input of wobble mediator 938 which operates as described in conjunction with FIGURE g to reproduce the Lo, Lo...; Lea, LEA...
scan signal as described previously.
The separated I signal at the output of filter 93()4 is also applied to a low-pass filter 1230 having a cutoff frequency below the lower sideband of the chrome signal to separate out the residual luminance signal (FIGURE 13g) extracted from the composite signal by chrome filter 9304. This residual Y signal is applied to a second input of swirling circuit 1210 to be added to the YE
signal for increasing the low frequency vertical lumillance resolution in known fashion.
FIGURE 14 illustrates another embodiment of an arrangement for generating the simultaneous paired-line information railroad to gerler~t~ Tao sup S and difference signals.
The arr~mge~ent of FIGURE 14 is believed to be more amenable to horizontal aperture correction than other embodiments.
In FIGURE 14, an oscillator 1400 operates at twice normal OH; in the case of signals intended for an NTSC system, oscillator 1400 operates at 31.5 KHz and drives a horizontal deflection winding 1402 associated with a vidicon ! 404. Vidicon 14V4 thus is scanned at twice the normal horizontal rate. The 2FH drive signal is also . applied to a-vertical countdown circuit 1~06 which counts the 31.5 Ye down to a 60 Ho vertical rate. Lowe 60 Ho ~22~ 5 1 . -23- RCA 77,253 MY B
counted signal is used to reset a ramp generator 1408.~f known type which uses an integrator to produce a vertical-rate ramp. The vertical-rate ramp is applied to a first input of an adder and vertical drive circuit 1410.
The 2FH signal from oscillator 1400 is also applied to a limiting or squaring amplifier 1412 for producing a 2FH
scurvy which is applied to a second input of adder 1410 for aiding to and subtracting from the ramp to produce a signal illustrated as 1416 which is applied to a vertical deflection winding 1418 associated with vidicon 1404. The amplitude of scurvy 1414 added to the ramp is selected to cause line pairing as illustrated on the face of vidicon 1404. Lines Lo and Lea are separated by one-fourth of the distills between lines Lo and Lo. This line pulling is similar to that described in the other embodiments.
Target 1~20 of v:idicon 1~04 is coupled to ' terminal 1422 of a four-pole, four-throw switch 1424.
Switch 1424 is under the control of a switch control circuit 1426 which steps switch 1424 to one ox its four positions at the beginning of each new scan line.
In the position shown, the input signal during line Lo is applied from terminal Tao a terminal 1427 of switch 1424 and is applied to the input of a delay line 1431. Clock control terminal 1425 of delay 1431 is driven at eight times the sub carrier rate from a clock generator 1448 coupled to switch terminal 1440. Delay line 1431 as is known must have sufficient storage capacity to store the video at the high clock rate for the duration of scan line Lo. FIGURE 15 is a timing diagram illustrating the operation of switch 1424 and clock delay lines 1431-1434, ~hicl-lmay be charge-coupl~d devices and are referenced CC~_ to CCD4 in injure 15. Also in the interval Tuttle, delay lines 1~,33 and 1434 ore 35, bring clocked at half they'll clock rate, in this.,c2se four times the swearer rate and tune output signals are applied by way of terminals 1452 ankle of a controlled switch 1450 to Torrance 1'55 and 145v of of the switch. At time To, line one ends and at time To line scanning of line Lea begins. In the interval Tl-T2, switch 1424 is .. . .

25;~L5 I RCA 77,253 DIVE s 1 . .
operated end each contact moves clockwise by one throw.
Terminal 1422 wherefore contacts terminal 1428, and video can be read into delay line l432 which then is clocked at the high clock rate by way of terminal 1441 from clock generator 1448. Clocking of delay line 1433 ceases, but clocking at the low rate of delay line 1434 continues by way of terminal 1447 from clock generator 1449. Low-rate clocking of delay 1431 begins at the low rate by way of lo terminal 1~44 from clock generator 1449. Also in the interval Tl-T2, switch AYE is thrown to connect delay 1431 to terminal 1455.
In the interval T2-T3, vidicon 1404 scans line Lea and the signal is applied to clocked delay 1432 for being stored therein at the high clock rate. Also yin the interval T2~T3, delay 1431 is read out at the low clock rate as illustrated it FIGURE 15b and delay 1434 continues to be clocked out at the low clock rate, as illustrated in FIGURE eye. At thy time To of the end of lint Lea switch 1424 is thrown to the next position so that tile video at terminal 1422 during line Lo is available for reading into -delay line 1433, delay line 1431 continues to be clocked out to terminal 1455 and the Lea data stored in delay line 1432 begins to be clocked out at the low rate. Swish 1415b is thrown to connect terminal 1453 with terminal 1456. The system continues to cycle, clocking into each delay line in succession at the high clock rate, hollowed by an interval of clocking out at the low clock rate as illustrated in FIGURES byway. It should be noted that fry the unloading pry, etch delay line CCD1-4 goes through one Ho interval in a quiescent state. As illustrated in FIGURES
15d and e, the Lo information loaded ho delay 1433 in the interval T4-T5 is unloaded in the interval T5-T9, while the LEA information loaded in-to delay 1434 in the interval T6-T7 is read out in the interval T7-Tll. Issue, it can be seen that the information of the paired lines appears at terminals 1455, 1456, relatively delayed by HJ2. This is corrected by an H/2 delay line 1460 coupled in the Lo, Lo t I,3...path, with the result that the information from the I

~2~3~5 1 line pairs occurs simultaneously at output terminals 1462, 1464 as illustrated in FIGURE foe. The video Ll/L2/L3 from output terminal 1462 and the video Lyle from output terminal 1464 is processed ego as shown in FIGURE 7, to produce the sum S and difference signals.
A high-resolution monitor of FIGURE 16 is arranged to scan at twice the standard horizontal frequency; at 31.5 I in the case of NTSC. In the arrangement of FIGURE 16, the input signal is in the form of two video signals occurring simultaneously, each of which represents the video from two adjacent scanned lines. The video signals are applied to terminals 1601 and 1602 at the left of the Fugue. The video signals applied to terminals 1601 and 1602 are arrived from the sum S an differ-once signals by ego apparatus as shown in Fig. 9 comprising adder 934, divider 935 and subtracter 936 as shown in block 938. ' The arrangement of FIGURE 16, generally speaking, is the reverse of the arrangement of FIGURE 19. In FUGUE 16, the two incline simultaneous signals at 15,750 Ho are rearrange as se~lelltial 31.5 Oh signals which are applied to kinescope 1670 at the right of the FIGURE.
A sync separator 1662 coupled to input terminal 1601 separates vertical and horizontal sync which is applied to a 2FH ILL 1664 for producing 2FH drive signals. (Alternatively, sync could be separately introduced and applied directly where required). The OF signal is applied to a vertical countdown and deflection circuit 1668 which generates a step ramp as described in conjunction with FUGUE 14 which is applied to a vertical deflection winding 1618 associated with kinescope 1670. The - 2FH signal is also applied as drive to a horizontal deflection winding 25 1676 at 31.5 KHz. At 31.5 KHz, each scan across the face of kinescope 1670 occurs in FH/2. Consequently, the two parallel input signals must be time-compressed and arranged in sunnily order.
Switches aye and 1650b are operated by signal produced by flip flop (OF) aye. OF 1658 is driven by OH signal.
As incoming signals representing lines Lo and Lea are received, switches aye and 1650b are in the down position connecting terminals 1655 and 1656 to delay lines 1632 and 1634, respectively.
Clock signals for these delay lines are provided from the 4X sub carrier generator ,:

~Z~5~
1 -26- KIWI 77,253 DIVE s 1649. These lines are written into the delays, and - writing is completed during one oh interval or cycle. At the completion of the input of lines Lo and Lea switches aye and 1650b are switched to their upper positions by a signal from OF 1658 and the next incoming line pair (Lo and LEA) begins to load into delay line 1631 and 1633.
Switch 1676 is also operated by OF 165~ and applies 4XSC
(low) clock signal to delays 1631 and 1633 by- way of contacts 1444 and 1445, respectively. during the time period in which lines It and IDA are being received and written into delays 1631, 1633, reeducate of line Lo begins from delay line 1632 while delay line 163~ is quiescent.
Switch terminal 1622 is connected to terminal 1628 by a lo trigger signal from 31 KEY clock, connecting the rodeo processing unit 1674 to the output of delay line. At the same time all 8X sub carrier clock 1648 is connected to delay line 1633 from thy 8X venerator through terminal 14~1 which is switched at the 31 OH rate in synchronism with the video Olltpllt switch. Readout of delay line 1632 is completed in half of the normal 15 KHz period, and switch 1678 is orated to a new position at which switch terminal 1622 and the output of 8X sub carrier generator 164~ are coupled to delay line 1634 which it read out, thus developing the required video for the display. The sequence of parallel read-in, sequential readout continues for supplying signal for the 31.5 KHz scan of the monitor.
Figure 17 illustrates a broadcast television receiver according to the invention. In FIGURE 17 an antenna 1710 receives composite color television signals with buried signal, the whole modulated onto carriers at standard broadcast frequencies with vestigial lower sidebands and with FM-modulated audio signals offset from 3., the video carrier frequency in the usual manner. A tuner 1712 selects one of the carriers and converts it to a standard IF frequency. *he resulting IF signal is amplified by an IF amplifier 1714 and is applied to a second detector 1716 for conversion to basebarld. The ~2'~5~L~5 27- RCA 77,253 DIVE B
audio signal is applied to an audio signal processing circuit 171~ which may include an FM demodula1;~r for : producing ~aseballd audio and which may also include an S audio drive for driving a loudspeaker 1720 associated with the receiver. The base band video signal is applied to an AGO control circuit 1722 which is coupled to the IF
amplifier and tuner for controlling the base band video amplitude. The controlled-amplitude husband composite color television signal with a is applied to circuitry corresponding to monitor 1200 of FIGURE 12 for producing on a color- kinescope 921 a color television signal with increased vertical resolution.
FIGURE 18 illustrates an arrangement for burying independent signals from first and second sources coupled to terminals 1802 and 1804 (to the left of the FIGURE) within the Q and I signals, respectively, of a composite color television signal. on FIGURE 18, light from a source (not shown) is applied through optics 800 to a splitting prism 802 W}liC}l divides the light and applies it to red and blue vidicons Andy 80~ and to a green vidicon 600 the deflection of which is wobbled at a wobble clock rate by an auxiliary deflection winding 606 riven ' from clock generator 614. Generator 614 also drives sync and blanking venerator 616 Jo generate burst flag and the sync and blanking signals which are coupled to an inserter 81R. The red and blue video signals are applied from vidicons 806 and 808 to a matrix 812. the green-representative signal is applied to a summing and differencing circuit 861, which,. for example consists of the combination of the synchronous modulator 618 and sum and difference circuit 700 of FIGURE
'/. Circuit 861 generates a US signal which is applied to an input of matrix 812 and a G six l wakeless Go to 35 dif:Eerentiator illustrated US a block 130b the output of weakly is coy to a threshold sense circuit 1808 which produces a read enable signal when the rate of change of the Go signal exceeds a predetermined level. The YE sisal from. matrix 812 is alp lie through a delay 1102 to a sunning circuit , .
....

1 814. The Q and I signals produced by matrix 812 are applied to low-pass comb filters 1810 and 1812 (erg. as shown a 1112 in Fig. 11) respectively, for combing out of the Q and I signals those portions representing rapid rate of change. The combed Q and I signals are applied to summing circuits 1814 and 1816, respectively. Thy incipient signals from the 5 first and second sources are applied together with their clock signals to memories 1818 and 1820, respectively, which act as buffers for accumul-cling the independent signals during those periods of time when the rate of change of the video signal is not great enough to conceal the independent signal. When a vertical-rate transition occurs, threshold 10 sense 1808 produces a read enable signal which is coupled to memories 1818 and 1~20 Lo enable reading at the rate of clock 1822, which is selected to interleave the independent signal into the I and Q signals.
The indeper,den- signals being read from memories 1818 and 1820 are combined wow sync words derived from thy clock 1822 in inserters 1830 15 and 1831. The sync words allow the regeneration of the clock signals upon retrieving the independent signals frown the television signal. The independent signals and the sync words are cleaned up in high-pass comb filters 1822 and 1824 (erg. as shown at 1122 in Fig. 11), respectively, and applied to summing circuits 1814 an 1&16 to be combined with their 20 respective concealing signal. The resulting sunless are low-pass filtered and applied to quadrature-modulators in known fashion for producing a chrominance signal which is summed with the YE signal in adder 814 and otherwise processed in the manner of a standard signal. A standard NTSC
color television receiver may display the independent signal on the edges 25 of vertical luminance transitions in the form of color errors in the transition region, kit such errors especially for large luminance trays-itchiness are subjectively not very visible. Consequently, a standard receiver is essentially insensitive to the buried information.
FIGURE 19 illustrates a receiver adapted for displaying 30 conventional television signals in which independent signals are buried and for extracting the independent signals. Those elements of FIGURE 19 corresponding to elements of FIGURE 12 are designated by the save reference numeral. FIGURE 19 differs from the SLY

1 arrangement of FIGURE 12 in that the demodulated and filtered I and Q
signals are both sassed through complementary high-pass and low-pass filters and in that the luminance signal is differentiated and threshold Ed to control additional independent-:.ynal processing.
In FIGURE 19, the Q signal is applied to a complementary high-5 payslips comb filter pair 1914-1916 similar to filter pair 1214-1216 of FIGURE 12. The Q signal is available at the output of filter 1916 and is applied to the Q input of video process and drive circuit 9320. The independellt signal appears at the output of high-pass filter 1914. A circuit 1920 is coupled to receive the sum luminance signal YE
10 and compares adjacent lines to produce a difference signal corresponding to the output of differentiator 1806 in Fig. 18 and which is applied to a threshold circuit illustrated as a block 1932 for generating a signal indicative of the time when the independent signal on the Q channel may be coupled through the system. The inde~?lld~rlt 15 signal which appears at thy? outlet of filter 1914 is applied to a delay circuit 1918, having a delay sufficient to delay the independellt signal until after the operation of threshold 1932 couples the independent signal, to a gate 1920 which is operated by the enable signal. The gate couples the independent signal to a sync word identifying circuit 1922 20 and to the input of a memory circuit 1926. Sync word indent-flier 1922 identifies the sync words associated with the independent signals enabling independent signal clock generator 1924 to regenerate the clock signal to enable the signal to be written into memory 1926, where it remains 25 available for use. In a similar fashion, the independent I-channel signal becomes available at the output of high-pass comb filter 1214 and is coupled to a delay, gate, sync word identifier, clock generator and memory 1934 for the I channel corresponding to elements 1918-1926 of the Q channel.
Other embodiments of the invention will be apparent to those skilled in the art. Rather than inserting the information into the I channel, it can be inserted into the Q channel in the same manner as that ~;22S~
-30- RCA 77,253 DIVE s 1 described so long as the reduced Q bandwidth is acceptable . lot the bandwidth of the signal. Plurality of -I- signals can be inverted into both the I and Q channels, why oh fur this purpose constitute fourth and fifth c`.-.~nnels within the composite video transmission path.
Siillilarly, a signal can ~:~ inserted in either 1 or Q and ; all independent signal can be inserted into the other channel. Other wobble clock frequencies can be used in those embodiments using wobble clocks, and as mentioned these clocks may be locked to various system signals.
The invention can be used in conjunction Whitehall PAL composite color TV transmission systems in the same fashion as with NTSC, since the monochromatic or' luminance aspects of the resolution are toe same and the principles of.t~le color transmission differ from NTSC oily in minor details not relevant to the concealment aspects of the invention.
While the S and Q sigrlals in the e~lhodiments illustrated were derived from a green channel of a tricolor signal source, the difference signal could if desired be derived from the R or B signals, or the RUB
: signals front the source could be matrixes to produce pairs ox simultaneous Y signals which could then be sunned and 25 dif.Lerenced to produce YE and Y signals.
Another embodiment of the color camera of FIGURE 3 could use red, blue and luminarlce-responsive tubes as known, with two tubes in the luminance channel and one tube each in the chrome channels for reduced cost.
30 The offset of the rasters of -the two vidicons (or the corresponding offset of the images) in the arrangement of FI.IJRE 4 can be in multiples of 1/2 the interline distance plus 1/4 line, ratter thin simply 1/4 line.

This application is a division of Canadian Patent Application 408402.

Claims (5)

CLAIMS:

1. Display means for displaying an image represented by signals representing the difference in luminance between predetermined pairs of lines of a predetermined image scanning pattern and further luminance representative signals, derived from signals representing the luminances of the pairs of lines and which together with the difference signals allow the reproduction of the signals representing the luminances of the pairs of lines, the display means comprising means responsive to the differ-ence signals and the further signals to reproduce the luminance signals of said pairs of lines and means for reproducing the image from said reproduced luminance signals.

2. Display means according to Claim 1 for displaying an image represented by a composite video signal comprising the further signal and at least one chrominance component from which a portion of the frequency spectrum has been removed and into which portion the difference signal has been inserted, the display means comprising decoding means for decoding the composite video signal to reproduce the further signal and the chrominance component into which the difference signal is inserted and filter means for separating the difference signal from the chrominance component.

3. Display means according to Claim 2 for displaying an image represented by a composite video signal comprising the further signal and said one chrominance component into which the difference signal is inserted and further comprising a further chrominance component from which a portion of the frequency spectrum has been removed and into which an independent signal has been inserted, the display means further comprising further filter means for separating the independent signal from the further chrominance component.

4. Display means according to Claim 1, 2 or 3 wherein the lines of each said pair are adjacent.

5. Display means according to Claim 1 wherein the image reproducing means comprises means for reconstructing the image according to a further scanning pattern of scanning paths extending in a line scan direction and distributed in a field scan direction transversely of the line scan direction, each scanning path having a waveform oscillating in the field scan darken about the line scan direction, the scanning paths intersecting both the lines of the respective pairs of lines, which are adjacent, of the predetermined image scanning pattern, and means for sampling the luminance signals reproduced from the difference signals and the further signals in pro-determined time relationship with the oscillations of the waveform lo apportion them between the lines intersected by the waveform so as to reproduce the image.