US2465371A

US2465371A - Color television

Info

Publication number: US2465371A
Application number: US572696A
Authority: US
Inventors: Donald D Grieg
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC; Federal Telephone and Radio Corp
Priority date: 1945-01-13
Filing date: 1945-01-13
Publication date: 1949-03-29
Anticipated expiration: 1966-03-29
Also published as: BE469506A; FR924944A; GB650666A; CH268061A; CH268060A; ES172125A1

Description

COLOR TELEVISION F iled Jan. 13, 1945- 5 SheetS-Sheet i 3 it a 6 5 as AP ?5 4 n 11 at 2" mmvron.

ATTORNEY March 29, 1949. D. n. GRIEG COLOR TELEVISION 5 Sheets-Sheet 3 Filed Jan. 13, 1945 INVENTOR. .DUNAZD D. GlP/EG ATTOR/VEY WWN - March 29, 1949. D. o. GRIEG 6 COLOR TELEViSIOfi 4 Filed Jan. 15, 1945 i 5 Sheets-Sheet 4' IN V EN TOR. OO/VAL L7 D. 6/5 /56 ATTORNEY Patented Mar. 29, 1 949 COLOR TELEVISION Application Eanuary 13, 1945, Serial No; 572,696

9 Ciaims. 1

This invention relates to new and useful improvements in television systems and more particularly to a novel arrangement for controlling the vertical or frame synchronizing pulses in television transmitting and receiving arrangements.

Heretofore it has been the practice to separate the lines of video pulses by individual horizontal or line synchronizing pulses and to separate frames of such lines by a plurality of pulses which were subsequently integrated into a single synchronizing pulse.

In order to eliminate the inaccuracy that may be introduced by the conversion last referred to, to simplify the wave-forms now customarily required and to allow a flexibility so as to permit future changes in the system, according to the present invention the frame or vertical synchronizing pulse or pulses are distinguished from other pulses merely by their modulation.

In one embodiment of the invention successive frame synchronizing pulses are distinguished from one another by their time or Width modulation and thus may be used to control the interlacing of the lines of successive frames, e. g. to produce color effects and for other similar purposes.

These and other features of the invention will more clearly appear from the following detailed description of certain preferred embodiments thereof and the appended claims. The invention will be described with reference to the drawings in which:

Fig. 1 contains a collection of voltage curves of typical television signals arranged in accordance with prior practices and the present invention;

Fig. 2 shows voltage curves representing the signals at various stages of the transmitter;

Fig. 2a shows voltage curves of the color signal indicated at b in Fig. 2

Fig. 2b illustrates the generation of the horizontal synchronizing pulses;

Fig. 3 is a block diagram of a transmitter embodying the present invention;

Fig. 3a is modification of Fig. 3;

Fig. 4 shows voltage curves of television signals as they appear in various parts of the receiver;

Fig. 5 is a block diagram of a, receiver embodying the present invention; and

Fig. Grepresents the end of a cathode ray tube .in the receiver showing the interlaced video color lines.

Referring now to Fig. 1 of the drawings, 0. illustrates a typical. basic television signal which is .sent out by the conventional transmitter. The

signal consists. of a succession of video signals: I, followed by a horizontal synchronizing signal 2, at the end of each line along Whichthe scanning: takes place. These video signals with the horizontal synchronizing signal are repeated until a frame is completed. Then follow a succession of frame or vertical synchronizing impulses 3, consisting a plurality of. relatively long and short pulses. Equalizing pulses. which are generally required with this type of wave-form are not shown inthe illustration. By well known means the horizontal synchronizing impulses 2, are removed fromthe composite wave-form, converted into impulses ta indicated at b, andQthe horizontal synchronizing pulses 3 are integrated into a pulse to. By clipping the pulse to along line 4, the frame synchronizing pulse 32; of Fig. 1c is produced. I

It will be clear from. an inspection of line b, of Fig. i that if the, line 4, along which the pulse 311 is clipped were shifted then the position or the length of pulse 31) would be changed This occurs when the characteristics vary, supply Volt} ages change, signal levels vary, etc., and l ad to inaccuracies of timing and distortion", when the vertical synchronizing pulse is u d an interlaced scanning system to co interlacing of successive frames. The pa the present invention is to avoid. such; and this as indicated at d in Fig.

plished by transmitting one or. more chronizing pulses similar to t, disting the horizontal synchronizing pulses erably from other frame synchronizing time (width) modulation. It is not necessary to integrate and minor shift can occur in the vertical synchronization.

The frame synchronizing pulse or pulses 5, can be used in the conventional manner as frame synchronizing pulse of a black and white picture Whether interlaced or not, for controlling stereoscopic or polychromatic systems, or for other similar purposes.

The pedestals 2a and 5a carryingthe synchronizing pulses 2 and 5 may carry also a second pulse indicated at 2?) and 5b whose position is modulated with respect to the leading or trailingedge of the synchronizing pulse to convey some information, e. g. the sound accompaniment of the video signals.

According to one of the features of the present invention the vertical synchronizing pulses having a characteristic time or width modulation are. usedv to control the interlacing of three successive frames of picture signals corresponding 3 to light of difierent colors, e. g. red, blue, and green. In the following description an embodiment of this feature will be explained, it being understood that the invention is not limited to such application.

In Fig. 2, (1 illustrates the signal which it is desired to transmit. It consists of vertical synchronizing pulse 6, of a given width followed by the customary lines of video signals. These lines are interlaced with the lines preceding pulse 6.

At the end of the first frame, a vertical synchronizing pulse I is produced which is of greater width than pulse 6. The lines of video signals that follow pulse 1 will be interlaced between the lines spaced by pulses 6 and I.

At the end of the next frame vertical syncronizing pulse 8 is produced which is wider than I.

The lines of this frame are interlaced, between the lines of the second mentioned of the second frame and the lines following pulse 8, i. e. preceding the next pulse 6. The succession of the three groups or fields of signals as above described may then be repeated in the same sequence or preferably in rotating sequence so that each line receives all three color signals in each frame period in order to prevent color crawling.

As above stated, the pedestals of the synchronizing signal may carry also pulses modulated with respect to the leading or trailing edges of the synchronizing signals to convey some additional information, e. g. sound.

The video signals between B and 'I may repre-- sent red, between I and 8 blue, and between 8 and 6 green color.

A color camera of suitable type indicated in Fig. 3 at 9 will, as it scans an object, produce under the control of a horizontal pedestal generator I8, horizontal sweep generator 28, and vertical sweep generator 2i, video signals similar to those indicated in Fig. 2a. In this figure at b1, are shown the video signals representing red, at b2, those representing blue and at bx, the signals representing the green color. In Fig. 2, at b, these signals representing the three color components are shown in a single line one after the other and without the intervening frame synchronizing pulses.

The output of the color camera 9, is connected with the output of a vertical pedestal generator II. The generator II produces the pedestals 6a,

.Ia, and 8a (Fig. 2, lines a and c) for the vertical synchronizing pulses 8, I, and 8. It is controlled by a color pulse generator I2, which is adapted to produce the pulses shown at f in Fig. 2, marking the start of the color cycle i.e. the leading edge of pulse.

When the output of II and 9 are combined, We obtain three groups of pulses one of which is indicated at d, in Fig. 2. The three groups of pulses are fed into clippers I3, I3a. and I3b, respectively, to cut them along line I4 of Fig. 2 line (1. A composite of the resultant signals is shown at Fig. 2 line e. The three vertical synchronizing pulses 6, I, and 8 occur between two successive pulses I5 and I5a, produced by generator I2.

In addition to the vertical pedestal generator II, the generator I 2 controls also three delay net- Works I6, I60, and Hit). The network I6, is arranged to produce pulses like 6b indicated in Fig. 2 at 9. These pulses produce the field synchronizing pulses 6, to be placed on the pedestals 6a.

The network IGa is arranged to produce the pulses 'Ib indicated in Fig. 2 line i, to place the synchronizing pulse I on the pedestals Ia, and the delay network Ifib produces the pulses 8b of Fig. 2 line k which generates the vertical synchronizing pulses 8. The networks are delayed with respect to one another so as to produce the three pulses 6, I, 8 of varying widths by the relative displacement of the leading edges thereof.

The outputs of delay networks I6, I6a, and I6b, are fed into different width pulse generators I'I, Ila, and 81b, which are trigger circuits or shaper circuits adapted to produce square pulses of certain widths. The outputs of the pulse generators will be the three vertical synchronizing pulses of

different widths

6, 1, and 8.

These pulses are indicated in Fig. 2 at lines h, 7', and Z. The ouputs of pulse generators I'I, Na and I'Ib, and of the clippers I3, I3a, and I3b, are fed into a mixer I8.

While the generation of horizontal synchronizing pulses is well known, I have illustrated in Fig. 2b one way of accomplishing this in the present system. In this figure line a illustrates the output of the horizontal pedestal generator III. This generator is connecetd with a horizontal synchronizing pulse generator Illa, which produces the pulses shown on line b in Fig. 2b and which feeds into a mixer and clipper IOb which in turn is controlled by the vertical pedestal generator II. On the line 0, in Fig. 2b I have shown the vertical pedestal pulses and on line d of Fig. 2b, I have shown the horizontal synchronizing pulses of line b of Fig. 2b, superimposed on the pulses of line 0 of Fig. 2b. The

horizontal pulses are shown on line e, Fig. 2b,

and is the completed horizontal pulse which is fed into the mixer I8.

It will be obvious to those skilled in the art that many modifications of the procedure which I have outlined are possible without departing from the spirit of the present invention.

The output of mixer I8 is fed to a transmitter 40 I9 preferably through an intervening clipper I811.

The transmitter I9 will then transmit the signal shown on line a of Fig. 2.

While I have shown in Fig. 3, the three delay networks I6, I6a, and I6b, connected in parallel with the output of the color pulse generator I2,

the first one of these networks may be omitted, and they may also be connected in series with one another and with the generator I2. Such alternative arrangement is indicated in Fig. 3a.

The television signal a is transmitted through any suitable medium to actuate a receiver 20, Fig. 5. The received signal shown in Fig. 4 line a corresponds to the signal shown in Fig. 2 line a, but dimensioned to bring out more clearly the relationship between the timing of the various pulses. The output of the receiver is supplied to a clipper 2|, where the incoming signal a is clipped along line 22. The resultant is shown at b in Fig. 4, consisting of successive cycles of vertical synchronizing pulses 6, I, and 8 separating groups of horizontal synchronizing pulses 2.

The clipper 2| is connected with a horizontal synchronizing signal separator 23, and also with three

width discriminators

24, 24a and 24b. The separator 23 will have in its output, impulses representing the leading and trailing edges of all the synchronizing pulses. These are indicated at c in Fig. 4 and when fed through a clipper 25 will produce the horizontal synchronizing pulses indicated at d Fig. 4. It should be noted that the dimensions at the television waveform are so chosen as to produce equally spaced horizontal synchronizing pulses. It should also be noted that other means, such as an additional width discriminator may be used to separate the horizontal synchronizing pulses.- For the waveform illustrated the time for vertical blanking is approximately, one-half line period. If a longer blanking time is desired in the system several times line period may be used, and if desired additional horizontal synchronizing pulses may be included following the color pulses in order to maintain the regularity of the horizontal synchronizing signal.

The width discriminators 24, 25a and 25b may be of the same type as described in my copending application with Emile Labin, Serial No. 487,072, filed May 15, 1943, issued U. S. Patent No. 2,440,- 278, April 27, 1948, and will separate the vertical synchronizing pulses G, l, and B, respectively, indicated at e, f, and g, Fig. 4. These width discriminators include a resonant circuit which is shock-excitable in response to the leading and trailing edges of the pulses and a damping circuit having a vacuum tube connected across the resonant circuit for damping out the oscillatory energy following one or two undulations, as the case may be. The output from the circuit is provided with a threshold clipper stage which is adjustable to pass energy in response to undulations produced from pulses of a width corresponding to the tuning of the resonant circuit. Should the pulses be of a width difierent from one-half the period of the frequency to which the circuit is tuned, the undulations thereof will be less than that required to produce conduction in the threshold clipper stage. Thus, pulses varying in width from the desired width are blocked, pulse energy being passed by the clipper stage only in response to undulations produced from pulses of the desired width.

The output of the receiver 29 is fed not only to the clipper 2i but also to three

mixers

26, 25a, 26b in parallel.

The output of width discriminator 25, is connected to a timing circuit 2! and in multiple to a timing circuit 2%. The output of the width discriminator 2% is connected to timing circuits 2] and 21a and the output of width discriminator 2% is connected to timing circuits Zia and 21b. These timing circuits may comprise the wellknown flip-flop type circuits and will, respectively, produce pulses shown at Fig. ah, i and 7' which correspond to pulses e+f=h; f+g=i; and e+ =7'. The outputs of the circuits 2?, Zia and 21b, are fed to the mixers 26, Zea and 2%, where they are combined with the incoming signals a. The resultant is indicated at k in Fig. l. The outputs of the three mixers are clipped in clippers 28, 28a, and 2812, whose outputs in turn are shown at Z, m, and n, Fig. 4, which correspond to the three vision signals b1, b2, and be, shown in Fig. 2a.

The outputs of

clippers

25, 23, 28a and 2% are used to control the reproduction of the picture by interlacing the lines of the three successive colors (red, blue and green). This is illustrated in Fig. 6, which represents the screen of the cathode ray tube of the receiver on which the successive horizontal lines are traced. In this illustration the dimensions of the television waveform are chosen such that each line receives all colors successively for each complete color frame transmitted.

I claim:

1. In a television transmitter, a camera for producing in a plurality of output circuits video signals, a generator of pedestals for frame synchronizing pulses having its output circuit connected with the output circuits of the camera, clippers, one connected with each of the con- Gil nected circuits, a pulse generator controlling the first mentioned generator, a plurality of delay networks controlled by the pulse generator, each delaying to a different extent the generated pulses, a width discriminator connected with each network and arranged to produce pulses whose width is determined by the pulse produced by the associated network said width being less than the width of said pedestals, a mixer to which the clippers and discriminators are connected, and means for transmitting the output of the mixer.

2. In a polychromatic television transmitter, a camera for producing in three output circuits video signals, each representing a different color, a generator of pedestals for vertical synchronizing pulses having output circuits connected with the output circuits of the camera, three clippers, one connected with each of the connected circuits, a color pulse generator controlling the first mentioned generator, 3 three delay network controlled bhG color pulse generator, each delaying to a extent the pulses generated by the latter, a width discriminator connected with each netwerl: and arranged to produce pulses whose width is determined by the p rise produced by the associated. network said widths being less than the width of said pedestals, a mixer in which the outputs of the three clippers and discriminators are fed, and means for transmitting the output of the mixer.

3. A television receiver comprising means for receiving video signals separated by horizontal synchronizing pulses of uniform width and vertical synchronizing pulses of varying widths said pulses being superimposed on pedestal pulses, a clipper and a plurality of mixers connected in multiple with the receiving means, the output of said clipper consisting of said synchronizing pulses devoid of said pedestal pulses, a plurality of pulse width discriminators connected in multiple with the clipper and each arranged to segregate a vertical synchron zing pulse of a particular width, a plurality of flip-flop timing circuits connected with the outputs of the last mentioned width discriminators, a connection from each flip-flop circuit to a different one of the mixes, a clipper to which the output circuit of each mixer is fed, and means for interlacing the outputs of the last mentioned clippers.

i. In a polychromatic television receiver, video signals separated by horizontal synchronizing pulses of uniform width and the frames by vertical synchronizing pulses of varying widths all of said pulses being superimposed on pedestals, a clipper and a plurality of mixers connected with the receiving means, the output of said clipper consisting of said synchronizing pulses devoid of said pedestal pulses, Width discriminators connected with the last mentioned clipper and each arranged to segregate a vertical synchronizing pulse of a particular width, said discriminators controlling said mixers, and means for interlacing the outputs of the mixers.

5. In polychromatic television receiver, means for receiving video signals separated by horizon-- tal synchronizing pulses of uniform width and vertical synchronizing pulses all of said pulses being superimposed on pedestal pulses of varying widths, a clipper and three mixers connected in multiple with the receiving means, the output of said clipper consisting of said synchronizing pulses devoid of said pedestal pulses, three width discriminators connected in multiple with the last mentioned clipper and each arranged to segregate a vertical synchronizing pulse of a particular width, three flip-flop circuits connected with the outputs of the last mentioned width discriminators, the first circuit with the first and second, the second with the second and third, and the third with the third discriminator, a connection from each flip-flop circuit to a different one of the mixers, a clipper to which the output circuit of each mixer is fed, and means for interlacing the outputs of the last mentioned clippers.

6. A television system comprising in the transmitter, a camera for producing in a plurality of output circuits video signals, a generator of pedestals for vertical synchronizing pulses having its output circuit connected with the output circuits of the camera, clippers, one connected with each of the connected circuits, a pulse generator controlling the first mentioned generator, a plurality of passive delay networks controlled by the pulse generator, each delaying to a different extent the generated pulses, a width discriminator connected with each network and arranged to produce pulses whose width is determined by the pulse produced by the associated network, a mixer to which the clippers and discriminators are connected, and means for transmitting the output of the mixer; and in the receiver, means fOr receiving the transmitted signals, a clipper and a plurality of mixers connected in multiple with the receiving means, the output of said clipper corresponding to the combined outputs of the width discriminators at the transmitter but devoid of said pedestals, a plurality of pulse width discriminators connected in multiple with the last mentioned clipper and each arranged to segregate a pulse of a particular width, a plurality of timing circuits connected with the outputs of the last mentioned width discriminators, a connection from each timing circuit to a difi'erent one of the mixers in the receiver, a clipper to which the output circuit of each mixer is fed, and means for interlacing the outputs of the last mentioned clippers.

7. A polychromatic television system comprising in the transmitter, a camera for producing lines of video signals, in each circuit representing different colors, means for producing frame synchronizing pulses superimposed on pedestal pulses, means for modulating the width of said synchronizing pulses to differentiate between successive frames of difierent color, a mixer for said signals and pulses, and means for transmitting the output of the mixer, and in the receiver, means for receiving the transmitted signals, means for discriminating said pulses, means for eliminating said pedestal pulses and means for interlacing lines of successive frames under the control of said pulse.

8. A polychromatic television system comprising in the transmitter, a camera for producing in a plurality of output circuits video signals, each representing a different color, a generator of pedestals for vertical synchronizing pulses having its output circuits connected with the output circuits of the camera, clippers, one connected with each of the connected circuits, a pulse generator controlling the first mentioned generator, means controlled by the pulse generator to produce pulses of a plurality of different widths, a mixer in which the last mentioned pulses are combined with the outputs of said clippers, and means for transmitting the output of the mixer; and in the receiver, means for receiving the transmitted signals, a clipper and a plurality of mixers connected with the receiving means, the output of said clipper corresponding to the last mentioned pulses of different widths devoid of said pedestal pulses, width discriminators connected with the last mentioned clipper and each arranged to segregate a pulse of a particular width, said discriminators controlling said last mentioned mixers, and means for interlacing the outputs of the last mentioned mixers.

9. A polychromatic television system comprising in the transmitter, a camera for producing in three output circuits video signals, each representing a different color, a generator of pedestals for vertical synchronizing pulses having output circuits connected with the output circuits of the camera, three clippers, one connected with each of the connected circuits, a color pulse generator controlling the first mentioned generator, three passive delay networks controlled by the color pulse generator, each adapted to delay to a different extent the pulses generated by the latter, a width discriminator connected with each network and arranged to produce pulses whose width is determined by the pulse produced by the associated network, a mixer in which the three clippers and discriminators are connected, and means for transmitting the output of the mixer; and in the receiver, means for receiving the transmitted signals, a clipper and three mixers connected in multiple with the receiving means, the output of said clipper corresponding to the combined outputs of the three width discriminators at the transmitter devoid of said pedestals, three width discriminators connected in multiple with the last mentioned clipper and each arranged to segregate a pulse of a particular width, three flip-flop circuits connected with the outputs of the last mentioned width discriminators, the first circuit with the first and second, the second with the second and third, and the third with the third discriminator, a connection from each flip-flop circuit to a different one of the mixers in the receiver, a clipper to which the output circuit of each mixer is fed, and means for interlacing the outputs of the last mentioned clippers.

DONALD D. GRIEG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,109,540 Leishman Mar. 1, 1938 2,261,762 Hazeltine Nov. 4, 1941 2,295,023 Beatty Sept. 8, 1942 2,301,521 Cawein Nov. 10, 1942 2,306,386 Hollywood Dec. 29, 1942 2,309,506 Herbst Jan. 26, 1943 2,319,789 Chambers May 25, 1943 2,406,760 Goldmark Sept. 3, 1946