Note: Descriptions are shown in the official language in which they were submitted.
Lowe
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1 TELEVISION SYSTEMS AND SUBSYSTEMS THEREFORE
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
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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;
Jo '
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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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-6- lZZ51~5 RCA 77253 DIVE B
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
,
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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.
LO
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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
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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
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--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 4
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
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RCA 77,253 DIVE B
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
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-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
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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.
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--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.
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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
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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. .
I 5
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
-25- RCA 77253 MY B
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
, .
....
-28- RCA 77253 DIVE B
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
-29- RCA 77253 DIVE B
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.
