US2406760A - Color television - Google Patents

Description

Sept. 3, 1946.

P. C. GOLDMARK COLOR TELEVISION Filed sept. i?. 194q 3 Sheets-Sheet 1 ATTORNEYS Sept. 3, 1946.

P. c. GQLDMARK COLOR TELEVISION Filed Sept. 1'7. 1940 3 Sheets-Sheet 2 m-JM- ATTORNEYS Sept. 3, 1946V P. c. GoLDMARK 2,406,760

` coLoR TELEVISION Filed Sept. 1'7, l194.0 3 Sheets-Sheet 3 ATTORNEYS Patented Sept. 3, 1946 COLOR TELEVISION Peter C. Goldmark, New York, N. Y., assignor to Columbia Broadcasting System,

Inc., New

York, N. Y., a corporation of New York Application September 17, 1940, Serial No. 357,082

(Cl. P18-5.2)

46 Claims.

This invention relates generally to the field of television, particularly` television in natural colors. of a method and apparatus for balancing color signals obtained by a scanning procedure. However, in certain of its aspects the invention has somewhat Wider application.

There have been proposed heretofore a number of systems for color television. In one type of system an object field is simultaneously scanned in several primary colors, and the several color signals sent over separate channels to a receiver. Either separate carriers or separate sub-carriers have been suggested. In another type of systeman object eld is successively or sequentially scanned in a plurality of primary colors and the corresponding signals sent over a single channel to a receiver. The latter type of system is considered preferable since it avoids the diiliculties and complexities-of multiple channel transmission and reception.

Correct color rendition requires not only the proper spectral band for each of the primary colors but also requires that the relative magnitudes of each of the primary color signals be properly correlated. In color photography these requirements are met by employing filters of correct spectral band Width and correct transmis- 'l sion factors. Since filters such as the Well known Wratten filters are available only in a limited range of transmission factors for given spectral bands, it is often impossible to find a suitable .combination of lters having both the desired spectral band widths .and proper transmission factors. Therefore, to obtain proper balance neutral gray iilters are often employed.

In televisionsimi1ar resort can be made to neutral gray lters to obtain proper balance in spectral regions of photoelectric surfaces such as commonly employed in television scanning tubes may vary from tube to tube, thus requiring the filter system to be redesigned for each tube. In addition, different lighting conditions such as different day light conditions or diierent types of articial light sources may require different The invention contemplates the provision correction of the transmission characteristics for the different primary colors.

In the color system employing simultaneous scanning in several colors with separate channels for the diierent color signals, the gain of ampliers in the several channels may be changed to secure the proper balance between the magnitudesof the several simultaneous color signals. However, this expedient cannot be employed in the more important sequential system wherein successive color signals are produced by the same scanning device. It is a primary object of the present invention to provide a method and apparatus for changing the relative magnitudes of the different color signals even though they are produced by successive scansions of an object eld through diierent color lters by a single scanning device.

In the present invention, a composite multicolor video signal of the type mentioned above, in which successive portions represent different primary colors, may be employed as the initial signal. In accordance with the invention, signal portions representing at least one color are separated from the initial sequentialcomposite multicolor video signal and the relative magnitudes of the separated portions and the remaining portions altered as desired. The portions are then recombined tcform a color video signal' similar to the initial video signal butzhaving the relative magnitudes of the colors altered as desired.

In a preferred embodiment of the invention the video signal is passed into a number of ychannels corresponding to the number yof colors employed. For convenience of explanation, a.v three-.color system using red, greenand blue lterswill be assumed, it being understood that a diierent number of primary colors may be employed 1f desired. In one channel the green andblue signals are eliminated by blanking waves of suitable form, leaving only the red signal. Inthesecond channel, the red and blue signals are eliminated, leaving only the green signal. In the third channel, red and green are eliminated, leaving the blue signal. In each channel, or in any desirednumber bf channels, is placed a suitable devicej for altering the magnitude of the signal in that channel. Attenuators are conveniently employed, but

other means for either increasing or decreasing the amplitude of the .signals in the channels could be employed if desired, By suitable adjustment of the attenuators or other means forchanging the magnitudes, any desired relationshipwrnay be obtained between the magnitudes of thethree separate color signals. The three signalsare then recombined to form a signal similar to the input video signal, but in which the signals have the desired relative magnitudes.

In this manner proper balances of the colors can be obtained even though the magnitudes of the color signals in the incoming video signal are quite unbalanced. Furthermore, any one or more colors can be emphasized, thus permitting a wide variety of special effects to be obtained and enabling an artistic change in color to be produced at the will of the operator.

A number of advantages result from the employment of the method and apparatus of the present invention. In general, it is necessary" that the filters employed be selected only for proper spectral band widths. In direct pickup devices the same filters may be employed for both outdoor and indoor scenes, and for various conditions of outdoor and indoor illumination. Any unbalance in the several color signals can be corrected quickly and conveniently by altering the gain in one or more channels. Furthermore, in case black and white pictures are interspersed with color pictures, or are transmitted by thev color system, adjustments can readily be made to secure good blacks and Whites. In lmscanning devices employing colored lm, for example, of the Technicolor or Kodachrome type, Correct color balance may be obtained even though the balance of colors in the iilm itself be incorrect. This is a decided advantage, since difiiculties in properly exposing and processing color lm often result in undesired unbalance of color.

A further distinct advantage lies in the improvement in signal-to-noise ratio which may be obtained by the use of the present invention. In filters at present commercially available it is found that the blue lter is less transparent to light than the red or green filters, and one of the latter may be somewhat more transparent than the other. Also, the response of photoelectrlc surfaces, such as used in scanning devices, is commonly different for different spectral regions. In such case, it would usually be necessary to employ neutral filters in connection with the one or more color filters so that the over-all response is balanced. Thus the amount of light falling on the scanning device is cut down for one or more colors, resulting in a decrease in signalto-noise for that color or colors. With thepresent invention it is unnecessary to employ such neutral lters, and the signal-to-noise ratio is therefore not decreased. Subsequently, in the color balancer, the signals corresponding to the more transparent filters may be cut down, but the noise is cut down in like proportion.

The invention will be more fully understood by a consideration of the following detailed description, taken in conjunction with the drawings, in which:

Fig. 1 is a diagram illustrating the manner in which the several color signals are selectively separated;

Fig. 2 is a diagram illustrating a manner of obtaining the blanking waves shown in Fig. 1;

Fig. 3 is a block diagram of a color balancing apparatus;

Fig. 4 is a circuit diagram of a color balancing apparatus; and

Fig. 5 is a circuit diagram of apparatus which may be used to obtain the blanking waves of Fig. 1.

Fig. 5a illustrates a single pair of tubes connef-ted similarly to those of Fig. 5.

Referring to Fig. 1, curve aillustrates a video signal, successive portions of which correspond to the red, green and blue aspects of an object eld. These portions cyclically recur as shown. The video signal may be considered as composed of three series of signal waves representing three colors, the three series,y alternating in regular sequence. Such a video signal may be forme'd by any suitable scanning device. For example, the scanners described in my copending applications Serial Nos. 355,839, now Patent No. 2,304,081, granted Dec. 8, 1942, and 355,840, led September '7, 1940, may be employed if desired. It will be understood that the invention is not confined to video signals produced by any particular scanning device.

In the usual system, each red, green and blue signal will represent a respective field scansion of the object eld. Each signal is separated by the usua1 blanking signal Il. In Fig. 1(a) the blanking signal is represented as extending to the zero axis, the minimum signa1 (black, in black and white transmission) is at a level slightly above the blanking level, and the maximum signal (white, in black and white transmission) is at a still higher level. It will be understood that the signal shown corresponds in general to the present R. M. A. standard signal. The black and white levels could be interchanged if desired. In general, the invention is applicable to any video signal having successive portions representing different colors. If the portions were of nonuniform length, the blanking waves could be changed accordingly. The polarity of the signals in Fig. 1(a) is selected to correspond to Fig. 4, hereinafter described.

Fig. 1(b) illustrates a type of blanking wave suitable for blanking out the green and blue signals,leaving only the red signal. The wave is denoted Blanking wave I for convenient reference. During the red signa1 period blanking wave I passes the video signal, and during the green and blue signal periods it cuts ol the video signal. Figs. 1(0) and (d) illustrate blanking waves II and III designed to pass the video signal during the green and blue signal periods, respectively, cutting off the remaining portions of the video signa1.v These blanking Waves may be considered as composed of passing pulses, with blanking pulses between the passing pulses. The several blanking waves are phased with respect to the color video signal to pass respectively difierent series of signals representing different colors.

Fig. 2- illustrates one Way of obtaining the blanking waves of Fig. 1. Fig. 2(a) illustrates a symmetrical rectangular wave, one cycle of which occupies 360 electrical degrees in accordance with conventional terminology. Fig. 2(b) illustrates a similar wave displaced minus 60 electrical degrees. When the waves of Figs. 2(a) and 2(1)) are added, the wave shown in Fig. 2(a) is obtained. By cutting off the bottom of the wave in Fig. 2(0) the wave of Fig. 2(d) may be obtained. For example, a tube biased to cut off along line l2 of Fig. 2(a) will yield the desired wave` of Fig. 2(11). Circuit arrangements vfor obtaining the various waves shown in Fig. 2 will be known to those skilled in the art. In Fig. 2(d) the width of each passing pulse is one-half the blanking interval between pulses, thus corresponding to the blanking waves of Fig. 1. By displacing the curve of Fig. 2(d) by 120 electrical degrees in eachdirecton, the three blanking waves of Fig. 1 may be obtained. 1

A convenient system of obtaining the blankinw waves of Fig. 1, designed by John M Hollywood, I

is described hereinafter in connection with Fig. 5. It will be understood that any convenient means of obtainingthe desired blanking waves may be employed, and that the invention is not confined to any'particular manner of obtaining them. Furthermore, the blanking waves will,-of course, be adapted to th'e color video signal being changed, and will be appropirate to the particular apparatus which utilizes the blanking wave.

Referring to Fig. 3, a color video signal such as shown in Fig. 1(a) is fed into potentiometer I3, by means of which the over-all magnitude of the signal may be adjusted. The signal is fed into three separate signal channels, denoted Red, Green, and Blue. Potentiometers I 4R. MG and IIB are inserted in respective channels so that the magnitude of the signal may be independently adjusted in each channel. Direct current relnjection circuits I5R, I5G and I5B are.

inserted in each channel. These circuits may be of conventional .design and serve to provide a stable reference level for the signals in each channel. The direct current reinjection might be performed elsewhere if desired, as will be understood by those skilled in the art. The signals in the three channels then pass into respective mixers IGR, IBG and ISB, wherein they are mixed with' respective blanking waves I, II and III. These mixers serve to completely eliminate all but the desired color signal in the manner described in connection with Fig. 1. The output of mixer IGR will contain only the red signal, that of mixer ISG only the green signal, and that of ISB only the blue signal. These signals are then recombined and pass into the output circuit I1.

The operation of the circuit of Fig. 3 will be apparent. By varying potentiometer I3 the magnitude of the output signal at Il may be changed as a whole. By adjusting potentiometers MR, MG and IIIB the relative magnitudes of the red, green and blue signals may be altered as desired.

It is considered desirable to insert an attenuator in each of the three channels to provide maximum flexibility. However, the attenuators could be omitted in one or two channels if desired. For example, the attenuators in the blue channel might be omitted and balance obtained by adjusting only those in the red and green channels, the'over all magnitude of the signal being adjusted by potentiometer I3. It is also possible to omit variable means for adjusting the magnitudes in the several channels, and sim ply design orl adjust the apparatus -initially to give the desired relative magnitudes in the output video signal for given relative magnitudes in the input signal. Such a design might be useful to simply compensate for diierent transmission.v

factors in the filters under otherwise fixed conditions. vSemi-fixed adjustments could also be employed, if desired.

It is contemplated and preferred to completely eliminate all but one color signal in each channel, thereby securing desirable exibility. However, if`desired for any particular application, signals corresponding to two colorscould be passed in vone channel and the third color in a second channel, thereby permitting a certain` amount of change in colorbalance although not as ilexible a change as with single colors in each of th'ree channels. Furthermore, one or more colors might be separated from the initial video signal, the desired magnitudes obtained, and then recombined with-the complete initial video signal in proper proportions to change the relative magnitudes of the correspondingl colors in the output video signal'. For example, :the red signal might be separated in one channel, the initial'video signal passed unchanged through a sec-I ond channel, the relative magnitudes selected as desired, and the outputs of the two channels combined so that the red signal in the rst channel will alter the red portion of the video signal issuing from the second channel.

Referring to Fig. 4, the video lsignal enters the apparatus at 2I and is supplied through potentiometer 22 and a coupling condenser 23 to the amplifying stages 24. Stages 24 may be a conventional video signal ampliiier and hence need not be described in detail. The output of the amplifying stage is fed into three potentiometers 25R, 25G and 25B connected in parallel as shown. These potentiometers are adjustable and feed the video signal, with the desired relative magnitudes, into respective red, green and blue signal channels through coupling condensers 2BR., 26G and 26B.

For convenience, only the red channel will be described in detail, it being understood that the other two channels are similar.

The D. C. reinjection circuit comprises vthe diode 21R. and resistance 2BR. This D. C. reinjection circuit is known in the art and hence need not be further described. The video signal is then fed into tube 2BR of the mixer type, containing two separate control grids 3IR and 32R shielded from each other. These two control grids act independently on the electron stream. The video signal, which is of the type shown in Fig.. l(a), is fed to control gridSIR. Blanking wave I shown in Fig. l(b) is supplied to terminal 33B., and the corresponding voltage developed across the resistance 34R is applied to grid 32R. The circuits for connecting the blanking wave to the grid areY not shown, since they will be understood by those skilled in the art. Cathode heating circuits are also omitted for simplicity of illustration, but are of course employed.

During the intervals the positive pulses of blanking wave I are applied tov grid 32B., the electron current is permitted to ow and the tube operates as an amplifier tube with modulation under the control of grid SIR. The output is thereby modulated by grid 3IR in -accordance with the red portions of the video signal. During the intervals between the positive pulses of signal, which are thereby cut oft'. 'I'hus only the red portions of the video signal pass to the output line 35B. f

The green and blue channels are similar, ex-v cept blanking wave II of Fig. 1 is impressed on terminal 33G of the mixer tube in the green channel, and blanking Wave III of Fig; 1 on the terminal 33Bof the mixer tube in the blue channel.

Adjustable rheostats 3BR, 3BG and 36B are connected between the cathode and the shielding screens of the respective mixer tubes 2BR, 29G and 29B. By adjusting these three rheostats, the accelerating potentials and thus the gain of the grids 3IR, 3IG and 3IB may be'made the same for all three channels. The potentials for the shields are provided from the B-plus supply through resistance 31, and resistances 38B., 3BG and 38B. A voltage regulator 39 is provided to maintain the screen potentials constant. 'I'he green and blue portions of the video signal are recombined and are fed to the desired output apparatus through coupling condenser I2. At the transmitter, the signals would usually be fed to the monitor and to the transmitter.

The operation of the apparatus is similar to that shown by the block diagram of Fig. 3. The relative magnitudes of the individual red, green and blue components of the video signal are separately adjustable by the variable potentiometers 25R, 25G and 25B, thereby obtaining an adjusted color balance. The over-al1 magnitude of the signal Vis adjustable by the variable potentiometer 22.

Referring to Fig. 5, a circuit designed by John M. Hollywood for conveniently lgenerating the blanking waves I, Il and III is shown. The circuit comprises a, ring connection of three pairs of tubes 50H, 50'R, 50G, 50G and 50B, 50B (the pairs corresponding to red, green and blue waves). The input 5I to the circuit is supplied with a continuous series of pulses, termed starting pulses, which control the generation of the blanking Waves appearing across the output terminals 52H, 52G and 52B.. For the system of Fig. 1, the starting pulses may be the blanking signals rI l appearing between each fleld scansion, and may be taken directly from the blanking signal generator and applied to input 5I, For a fleld scansion period of tiza second, the blanking signals will consist of short pulses recurring at a frequency of 120 per second.

The functioning of the circuit will be grasped more readily by referring rst to Fig. 5`(a) which illustrates a single pair of tubes 50, 50', connected similarly to those of Fig. 5. The tubes specifically illustrated are pentodes, for example, of the 6C6 type, and both the screen and control grids are employed as control grids. Other type tubes may of course be employed if desired.

The cathode of tube 50 is grounded and the cathode of tube 50 is connected to ground through the output resistance 53. The suppressor grids are connected directly to the respective cathodes. The cathode heaters are omitted in the drawings for simplicity, but are of course employed. The screen grids SG and SG', here used as control grids, are connected to the plates of the opposite tubes, respectively. through the batteries D and D having the polarities shown. In the plate circuits are plate resistances R and R', respectively, connected to a B-plus supply.

With the circuit connections shown, and with a proper choice of parameters, a short negative. impulse on the grid G of tube 50 will cause current to begin to flow in tube 50', thus 'causing an output voltage to appear across resistance 5l. This current will continue to ilow after the impulse on grid G ceases, and until a negative impulse is applied to grid G', whereupon the current in tube 50' will be abruptly cut oi and the output voltage across resistance 53 will return to ground potential.

The operation may be understood by assuming initially that current is ilowing in tube 50'. The voltage drop in-plate resistance R' together with the voltage of battery D biases the grid SG of tube 50 sufilciently negative,` by choice of suitable parameters, so that no current can ilow in the plate circuit Aof tube 50 regardless of the potential of its grid G. In this condition a positive output voltage exists at terminal 52. If now being considered to follow tube EO'B.)

8 a negative pulse of sumcient magnitude termed a cut-oil!" pulse, is applied to grid G', the current in tube 50' will be abruptly cut off, thus causing the output voltage at terminal 52 to drop to ground potential. At the same time, cessation of plate current causes the voltage drop in plate resistance R' to become zero, and the plate B- y plus supply, which is greater than battery D', causes the grid SG to become positive, thus allowing current to iiow in tube '50 under the control of its grid G.

Under these conditions, ii grid G is suillclently positive with respect to its cut-0E potential, current will flow in tube 50. The voltage drop in plate resistance R, together with battery D, will now cause the grid SG .of the tube 50' to become suiilciently negative to prevent any current from flowing in tube l50' regardless of the-potential of its grid G'. Under these conditions no output voltage will be generated. If, then, a negative pulse of sufficient magnitude, termed a starting pulse, is applied to grid "G, current in tube 50 will be cut ofi. The voltage drop in R will become zero, and the plate B-plus supply will counteract battery D and cause grid SG' to become positive, thus allowing current to flow in tube 50 under control of its grid G'.

Referring again to Fig. 5, the pairs of tubes are connected similarly to the' pair in Fig. 5 (a). However, the batteries D and D' have been replaced by respective combinations of a resistances 54, 54' and a condenser 55, 55. The values of these resistances and condensers should be selected with respect to the screen grid current and the frequency of operation to provide a bias equivalent to batteries D and D', as will be understood by those in the art.

The starting pulses from input 5| are applied simultaneously to the grids G of all three tubes 50E, 50G and 50B through respective condensers 56 and resistances 51. Since it isdesired that an output voltage be generated by only one pair of tubes at a time (see Figs. 1 (b), 1 (c) and 1 (d) interconnections are provided so that only one pair of tubes is in condition to be started by a. starting pulse at any given time, and the starting of this pair will cause the cut-off of voltage generated by the previous pair.

These interconnections inclu'de "re-setting re`- sistances 58 connected, respectively, between the platesk of tubes '5|iR, 50G, 50'B- and the grid resistances -51 of the following tubes 50G, 50B, 50B.. (Following tubes are the next tubes around the ring from left to right, tube 50R 'I'he resistance values are selected so that when no current is owing in the plate circuit of any one of tubes 50'R, 50G, 50B, the positive bias applied to the grids G of the following tubes, respectively, will overbalance a negative starting pulse and prevent thefollowing tube 50 from being cut oi by the starting pulse, thereby preventing the corresponding tube 50 of the pair from developing an output voltage. On the other hand, when one tube, say tube 50'G is passing current, the voltage drop in its corresponding plate resistance R will reduce the positive bias on the grid G of the following tube 50B, thereby re-setting tube 50B and permitting the next starting pulse to cut cil current in 50B, thereby causing current to ilow in 50'B to create an output potential at 52B. Condensers 56 introduce a small time lag in resetting, so that a single starting pulse will not start current flowing in the output circuit of each pair of tubes in 9 quick succession. The resetting should of course take place before the next starting pulse arrives. In this manner, only one pair of tubes at a time is in condition to be started by a starting pulse, and the particular pair is the one following the pair which is already creating an output voltage.

The above-mentioned interconnections also include cut-off resistances 59 connected between the grids SG of tubes 50B, 50G, 50B and the grids G of the preceding tubes 50'B, SIJ'R, 50'G, respectively. Continuing the operation just described, the starting of tube 50'B results in applying a negative potential to grid SG of tube 50B sufficient to bias tube 50B to cut-off. The same negative bias is applied through resistance 59 to the grid G' of the previous tube 50'G, thereby cutting off current in that tube and cutting off the output voltage at terminal 52G.

Continuing the cycle, the starting of tube 50B reduces the positive bias applied through resistance 58 to the grid G of tube SUR. The cutting 01T of current in tube 50'G makes grid SG of tube 50G positive, and this positive bias is applied through resistance 59 to grid G' of tube 50'R. Therefore the next starting pulse will cut off current in tube 50B. and cause current to flow in tube 50'R, thereby initiating an output signal at terminal 52B.l Starting of current in 50'R will also cut olf current in tube 50'B, thus cutting off the output voltage at 52B.

It will therefore be apparent from the foregoing that if starting pulses of brief duration recur at, say, 120 pulses per second, output signals will be successively generated at terminals 52E, 52G and 52B at intervals of 1/izo second, and each output signal will have a substantially constant value for substantially 1/120 second. Thus the output signal at 52R will be like Fig. 1 (b), at 52G like Fig. 1 (c), and at 52B like Fig. l (d). Output terminals 52B, 52G and 52B may be connected directly to terminals 33R, 33G land 33B, respectively, if the magnitudes of the voltages are correct, or through suitable means for obtaining the proper magnitudes.

It will be understood that the circuits shown in Figs. 3, 4 and 5 are given for purposes of illustration only. Many circuits may be devised by those skilled in the art for separating the several color components of the color video signal, adjusting the relative magnitudes individually, and then recombining them. Also, the channels need not be all in parallel, as shown. For example, successive pairs of channels might be employed, the red signal being adjusted in the first pair, the green in the second, and the blue in the third pair. Other arrangements will be apparent to those in the art.

The invention can be used for any number of primary colors by providing a suitable number of signal channels and suitable blanking waves, as willbe understood. The invention also may be useful for purposes other than color television. For example, in one system of interlaced lm scanning wherein the lm is continuously moving with uniform motion, two or more prisms or other optical elements are successively operated during respective field scansion periods. In some cases it may be difficult to balance the amount of light passing through each of the successively operated optical elements, and the unbalance in light may produce an objectionable flicker in the reproduced image. In such case, the video signal may be fed into an apparatus similar to that of Fig. 3 or 4, having the proper number of channels, and pulses fed into\the sevnals in each channel. That is, the signals produced by one prism or other optical element may ybe selected in one channel and the signals produced by the other optical elements selected in respective channels. For double interlacing, only two channels and a rectangular pulse wave would be required. By adjusting the attenua- .tors in the several channels, the difference in light transmission may be compensated for. Other uses will be apparent to those in the art.

While particularly important for use at the transmitter of a c0101` television system, the invention is also applicable to color television receivers wherein a standard sequential composite multi-color signal may be altered t0 give proper color rendition for receivers of different characteristics. Of course, in determining the balance of the color video signal at the transmitter, the characteristics of the receiver will usually be taken into account.

What is claimed is:

1. In a. color television system utilizing an initially produced sequential composite multi-color video signal of which successive portions represent different component colors of the plurality of colors of an image eld, the method of changing the color balance of said color video signal which comprises separating therefrom signal portions representing at least one selected color component of said image eld, altering the relative magnitudes of the separated portions and those other remaining' component portions of the initial color video signal, and recombining the separated and the remaining portions after said altering to obtain a sequential composite multi-color video signal having a desired color balance differing from that of said initially produced signal but otherwise substantially corresponding thereto.

2.- In a color television system utilizing an initially produced sequential composite multi-color video signal comprising successive portions which represent dierent component colors of the plurality of colors of an image field, the method of adjusting the color balance of said composite color video signal which comprises passing said composite color video signal into a plurality of signal channels, blanking out in at least one of said channels portions of the video signal representing',y at least one of said colors, recombining the signal waves to form a final sequential composite/'"multi-color video signal substantially corresponding .to said initial signal, and selecting the gain in said channels to yield an adjusted desired color balance of said iinal multi-color video signal.

3. In a color television system utilizing an initially produced sequential composite multi-color video signal comprising a plurality of color series of signal waves representing a corresponding plurality of colors of an image field, the signal waves of said plurality of series alternating in sequence, the method of adjusting the color balance of said multi-color video signal which comprises separating therefrom at least one color series of signal waves, adjusting the magnitudes of the separated series and the remaining color series of signal waves, and recombining the separated color series and the remaining color series after 'said adjusting to form an adjusted iinal sequential composite multi-color video signal.

4. In a color television system utilizing an initially produced sequential composite multi-color videosignal comprising a plurality of color series of signal waves representing a corresponding plurality of colors of an image field, the signal waves of said plurality of series alternating in sequence, the method of adjusting the composite multi-color balance of said color video signal which comprises passing said color video signal into a plurality of signal channels, blanking out in one of said channels all but one of said component color series of signal waves, blanking out in the remaining channels said one component color series, adjusting the relative magnitudes of the signal waves in said channels, and recombining the signal waves in said channels after said adjusting to form an adjusted final sequential composite mul-ti-color video signal.

5. In a color television system utilizing an initially produced sequential composite multicolor video signal comprising a plurality of color series of signal waves representing a corresponding plurality of colors of an image field, the signal waves of said plurality of series alternating in sequence, the method of adjusting the color balance of said color video signal which comprises passing said sequential composite multicolor video signal into a plurality of signal channels corresponding in number to said plurality of color series, each channel containing an electronic tube amplifier, applying an electric blanking wave to eachchannel to blank out all but one of said component color series of signal waves, the component color series not blanked out being different for diierent channels adjusting the relative magnitudes of the signal waves in said channels, and combining the output signal waves of said channels to form a final sequential composite multi-color video signal similar to the inital sequential composite multi-color video signal but of adjusted color balance.

6. In a color television system utilizing an initially produced sequential composite multicolor video signal comprising a plurality of series of signal waves representing the corresponding plurality of different colors of an image field, the signal waves of said plurality of series alternating in regular sequence and corresponding to respective field scansions of substantially equal length, the method of adjusting the color balance of said color video signal which comprises passing the composite multi-color video signal into a like plurality of signal channels, generating a like plurality f electric blanking waves and combining them with the video signals in respective channels, each blanking wave having pulses of substantially field scansion length recurring at the frequency of signal waves in one component color series and adapted to pass signal waves of that series, the portions of the blanking wave between said pulses being adapted to blank out the remaining component color series oi the video signals, the blanking waves being phased with respect to the video signals to pass different component color series in different channels, adjusting'the amplitude of the signal waves in one or more channels to thereby adjust the balance between the different component color signal waves, and combining the output signal waves in said plurality of channels to form a final sequential composite multi-color video signal similar to the initial sequential composite multi-color video signal but of adjusted color balance,

7. In a color television system utilizing an initially produced sequential composite multicolor video signal of which successive portions represent different component colors of the plu- 12 ralityof colors of an image field, in combination, means for separating from said multi-color video signal portions representing at least one selected component color of said image field, means for altering the relative magnitudes of the separated component color portions and the remaining component color portions of the initial color video signal, and means for combining said separated color component portions and the remaining color component portions after said altering to form an altered final sequential composite multi-color video signal.

8. In a color television system utilizing an initial sequential composite multi-color video signal of which successive portions represent different component colors of the plurality of colors of an image field, in combination, a plurality of signal channels connected to be supplied with said color video signal, means associated with at least one of said channels for blanking out portions of said color video signal representing at least one of said component colors, and means for combining the outputs of said signal channels.

9. In a color television system utilizing an initial sequential composite multi-color video signal of which successive portions represent different component colors of the plurality of colors of an image iield, in combination, a plurality of signal channels connected to be supplied with said color video signal, means associated with at least one of said channels for blanking out portions of said complete composite multi-color video signals representing at least one of said component colors, and means for combining the outputs of said signal channels to form a iinal output sequential composite multi-color video signal similar to the initial sequential composite multi-color video signal, the gain in said channels being selected to alter the color balance in the nal output video signal from that of the said initial video signal.

10. In a color television system utilizing an initial sequential composite multi-color video signal comprising a plurality of component color series of signal waves representing the corresponding plurality of colors o1' an image field, the signal waves of said plurality of series alternating in sequence, apparatus for changing the color balance in said color video signal which comprises, in combination, a plurality of signal channels connected to be supplied with said initial color video signal, means associated with at least one of said channels for blanking out all but one of said component color series of signal Waves, means associated with the 'remaining signal channels for blanking out said one component color series in the remaining channels, means for altering the relative magnitudes of the color series in said channels from their relative magnitudes in the said initial color video signal, and means for combining the output signal waves of said channels to form a final sequential composite multi-color video signal similar to the said initial sequential composite multi-color video signal but of altered color balance.

1l. In a color television system utilizing an initial sequential composite multi-color video signal comprising a plurality of color series of signal waves representing the corresponding plurality of colors of an image field, the signal waves of said plurality of series alternating in sequence, apparatus for changing the color balance in said color video signal which comprises, in combination, a plurality of signal channels equal in num- 13 ber to said color series connected to be supplied with said sequential color video signal, blanking means associated with each channel for blanking out all but one of said color series yof signal waves, said one color series being diierent in different channels, means for altering the relative magnitudes of the color series in said channels from their relative magnitudes in the said initial color video signal, and means for combining the output signal waves of said channels to form a nal sequential composite multi-color video signal similar to the said initial sequential composite multi-color video signal but of altered color balance.

12. In a color television system utilizing an initial sequential composite multi-color vvideo signal comprising a plurality of color series of signal Waves representing the corresponding plurality of colors of an image field, the signal waves of said plurality of series alternating in sequence, apparatus for changing the color balance in said video signal which comprises, in combination, a plurality of signal channels connected to be supplied with said initial color video signal, means for generating an electric blanking Wave, means associated with one of said channels connected to receive said electric blanking wave and adapted to utilize said blanking wave to blank out portions ofthe said color video signal in said one channel, said electric blanking wave being adapted to blank out at least one component color series of signal waves in said one channel, means for combining the 'output signal waves of -said channels to form a nal output sequential composite multi-color video signal, the gains in said channels being controlled tc yield an output color video signal of altered color balance from the said initial sequential composite multi-color video signal.

13. In a color television system utilizing an initially produced sequential composite 'multi-color video signal comprising a plurality of color series `of signal waves representing the corresponding plurality of colors of an image ileld, the signal waves of said plurality of series alternating in sequence, apparatus for changing the color balance in said color video signal which comprises, in combination, a plurality of signal channels connected to be supplied with said color video signal, means for generating an electric blanking wave bination, a plurality oi signal channels equal in number to said color series having respective electronic mixer tubes connected -to be fed simultaneously with said color video signal, means for generating a plurality of electric blanking waves each having passing pulses of substantially eld scansion length recurring at the frequency of signal waves in one of said series and blanking pulses between the passing pulses, means for supplying a blanking wave to each of said 'mixer tubes in phase to pass different series of color signals in diierent channels, means in said channels for adjusting the relative magnitudes of the signal waves therein, and circuit connections for combining the outputs of said channels to form a iinal sequential composite multi-color video signal, whereby a resultant color video signal similar to the initial color video signal but of adjusted color balance may be obtained.

15. In a color television system utilizing a sequential color video signal comprising a plurality of series of signal waves representing a corresponding plurality of different primary colors of an image eld, the signal waves of said plurality of series alternating in regular sequence and corresponding to respective iield scansions of substantially equal length, apparatus for changing the color balance in said sequential color video signal which comprises, in combination, input terminals for receiving said sequential color video signal, a plurality of signal channels equal in having passing pulses recurring at the frequency y of signal waves in one of said series and blanking pulses between the passing pulses, means associated with one of said channels connected to receive said electric blanking wave and adapted to utilize said blanking wave to vpass said one series of the color video signal in said one channel and blank out the remaining series, means for combining the output signal waves of said channels to form a final output sequential composite multi-color video signal, the gains in said channels being controlled to yield a final output sequential composite multi-color video signal of alteredccolor balance from the initial sequential composite multi-color video signals.

14. In a color television system utilizing an initially produced sequential composite multi-,color video signal lcomprising a plurality of series of signal Waves representing the corresponding plurality of different primary colors of an image field, the signal waves of said plurality of series alternating in regular sequence and corresponding to respective field scansions of substantially equal length, apparatus for changing the color balance in said color video signal which comprises, in comnumber to said color series connected to be fed simultaneously with said complete color Video signal from said input terminals, direct current reinjection means in each channel, a thermionic vacuum tube in each channel having a pair of control grids of which one is connected to receive said sequential color video signal, means fo-r generating a plurality of electric blanking waves and Supplying respective blanking waves to the other control grid of the tube in respective channels, said electric blanking waves having pulses of substantially eld scansion length recurring at the frequency of signal waves of respective color series and adapted to pass signal waves of respective series and blank out the remaining color series, the blanking waves being phased with respect to the color video signal to pass different color series in different channels, means in said channels for adjusting the relative magnitudes of the signal waves therein, and circuit connections for combining the outputs of said channels to form a color video signal, whereby a resultant color video signal similar to the initial color video signal but of adjusted color balance may be obtained.

16. In a television systemcutilizing an initially produced sequential composite video signal comprising a plurality of series of signal waves, the waves of said plurality of series alternating in regular sequence, the method of adjustably balancing said series which comprises separating from said initial sequential'composite video signal the waves forming one series, adjusting the relative magnitudes of the Waves of said one series and the remaining portions of the said video signal, and recombining said one series with said remaining portions to form a desired adjusted video signal.

1'7. In a television system utilizing an initially produced sequential composite video signal comprising a plurality of series of "signal waves, the Waves of said plurality of series alternating in regular sequence, the method of adjustably balancing said series which comprises passing said sequential composite video signal into a plurality of signal channels, blanking out in at least one of said channels at least one of said series, recombining the signal waves in said channels to form a finally adjusted video signal, andv selecting the gains in said channels to yield a desired balanced video signal.

18. In a television system utilizing an initially produced sequential composite video signal comprising a plurality of series of signal waves,-the waves of said plurality of series alternating in regular sequence, the method of adjustably balancing .said series which comprises passing said video signal into a plurality of signal channels, combining an electric blanking signal with the said video signal in one channel to blank out all but one of said series of signal waves, combining an electric blanking signal with the video signals in the remainder of said channels to blank out said one series of signal waves, adjusting the relative magnitudes of said one series of signal Waves in said one channel with respect to the series of signal waves in the remainder of said channels, and recombining said one series with the remaining series to form a flnal sequential composite adjusted video signal. f

19. In a television system utilizing an initially produced sequential composite video signal comprising a plurality of series of signal waves, the waves of said plurality of series alternating in regular sequence, apparatus for balancing said series which comprises aplurality of signal channels connected to be supplied with said sequential composite video signal, means associated with at least one of said channels for blanking out at least one of said series of signal Waves, means for combining the outputs of said signal channels to yield a sequential composite output video signal, and means associated with said channels for altering the balance of said series in the said output video signal from that of the initial input video signal.

20. In a television system utilizing an initially produced sequential composite video signal comy prising a plurality of series of signal Waves, the Waves of said plurality of series alternating in regular sequence, apparatus for balancing said series which comprises a plurality of signal channels connected to be supplied with said initial sequential composite video signal, means for generating an electric blanking wave, means associated with one of said channels connected to receive said blanking Wave and adapted to utilize said blanking Wave to blank out portions of the video signal in said one channel, said blanking wave being adapted to blank out at least one series of signal waves in said one channel,. and means for combining the outputs of said signal channels to yield a final output sequential composite video signal, the gains of said channels Ibeing selected to yield an output video signal of altered balance from the said initial video signal.

21. In a television system utilizing an initially produced sequential composite video signal comprising a plurality of series of signal waves, the Waves of said plurality of series alternating in regular sequence, apparatus for balancing said series which comprises a plurality of signal channels connected to be supplied with said video signal, means for generating an electric blanking wave having passing pulses recurring at the frequency of signal Waves in one of said series and blanking pulses between the passing pulses, an electronic mixer tube associated with one of said channels connected to receive said composite video signal and said blanking wave and adapted to utilize said blanking wave to pass said one series of signals in said one channel and blank out the remaining series, and means for combining the outputs of said signal series, and means for combining the outputs of said signal channels to yield a final output sequential composite video signal, the gains of said channels being selected to yield an output Video signal of altered balance from the said initial video signal.

22. In a color television system, the method which comprises scanning an object field successively in a plurality of different colors to produce initially a sequential composite multi-color video signal of whichsuccessive portions represent different component colors of the object field, and subsequently changing the relative magnitude of those portions of the sequential composite multicolor video signal which represent one component color with respect to those portions representing another component color.

23. In a color` television system, the method which comprises successively scanning an object field in a plurality of different primary colors during respective eld scansions to thereby produce a sequential composite multi-color video signal of which successive field-scanning Waves represent different primary colors of the object eld,and subsequently changing the relative magnitude of the field-scanning Waves representing one primary color with respect to field-scanning waves representing another color to produce a sequential composite color video signal having altered color balance.

24. In a color television system utilizing a sequential composite color video signal comprising a plurality of color series of signal waves representing the corresponding plurality of colors of an image field, the signal waves of said plurality of series alternating in sequence, the method of adjusting the color balance of said color video signal which comprises generating an electric control wave having pulses recurring at the frequency of signal waves of one color series, said pulses being of substantially constant magnitude for the duration of the respective signal Waves of said one color series, and combining said electric control wave with said color video signal in phase with the signal Waves of said one color series to alter the magnitude of said one series.

25. In a color television system utilizing an initially produced sequential composite electric multi-color video signal comprising a plurality of color series of signal Waves representing the corresponding plurality of colors of an image field, the signal waves of said plurality of series alternating in sequence, apparatus for changing the color balance in said initial sequential composite multi-color video signal which comprises, in combination, means for generating an electric control Wave having pulses recurring at the frequency of signal waves of one color series, said pulses being of substantially constant magnitude for the duration of the respective signal Waves of said one color series, and means for combining said electric control wave With said sequential composite multi-color video signal substantially in phase with said one color series to thereby alter the magnitude of said one series with respect to another series.

26. In a color television system utilizing an initially produced sequential composite multicolor Video signal comprising a plurality of series of signal Waves representing the corresponding video signal which comprises, in combination, a`

signal channel containing an electronic mixer tube connected to be supplied with said color video signal, means for generating an electric control wave having pulses recurring at the frequency of signal waves of one color series, said pulses being of at least one field scansion in length and of substantially constant magnitude f A throughout a field scansion, and means for applying said control wave to said electronic mixer tube in phase with the signal waves of said one color series to alter the magnitude thereof.

2'7. In a television system, the method which comprises scanning an object ileld successively to produce an initial sequential composite video signal having a plurality of series of signal waves, the waves of said plurality of-series alternating in regular sequence, and subsequently changing the relative magnitude of one series of waves in 18 time represented by each television field, and means for cyclically controlling the amplification of the picture signals by the generated plurality of series of impulses.

32. In a color television system having a light sensitive surface with a non-uniform spectral sensitivity characteristic the method of transmitting signals representative of an object which includes the steps of sequentially altering the light transmitting path between the object and the light sensitive surface to produce a plurality of images of different selected spectral color bands said sequential composite video signal with respect to another series to thereby produce a modified sequential composite video signal similar to said initial video signal but of altered balance between saidseries.

' 28. The method of transmitting color television pictures which includes the steps of producing successively a plurality of primary color images of the object to be transmitted, sequentially scanning the plurality of produced images, producing electrical signals representative of each of the plurality of images, sequentially altering the intensity of the produced signals in synchronism with the sequential scanning of the plurality of color images. and individually controlling the degree to which the signals representative of any particular primary color are altered.

29. A color television system comprising means for producing successively a plurality of primary color images of the object to be transmitted, means for sequentially scanning the plurality of produced images, means for producing electrical signals representative of each of the plurality of images, means for sequentially altering the intensity of the signals in synchronism with the sequential scanning of the plurality of color images, said last named means including means for individually controlling the degree to which signals representative of any particular primary color are altered.

30. A television transmitting system wherein a series of picture signals are produced comprising a picture 'signal amplifying channel, means for generating a plurality of series of impulses, the impulsesof each series having a common frequency and time duration, and the impulses of each series being displaced from the impulses of the other series by a predetermined amount so that the impulses occur in a predetermined sequence, and means for cyclically controlling the amplification of the picture signals by the impulses.

3l. A television transmitting system wherein a series of picture signals are produced representing successive television fields 'comprising an amplifier for increasing the intensity of the picture signals, means for generating a plurality of series of impulses having a predetermined common frequency and time duration, the time duration of the impulses of each series corresponding to the of the object on the light sensitive surface, scanning each of the plurality of the produced images to produce signals representative thereof, and sequentially altering the amplitude of the produced signals in accordance with a function of the product of the spectral sensitivity and the transmission of the light transmitting path for each of the produced images.

33. In a color television system having a light sensitive surface with a non-uniform spectral sensitivity characteristic the method of transmitting signals representative of an object which includes the steps of sequentially altering the light transmitting path between the object and the light sensitive surface to produce a plurality of images of different selected spectral color bands of the object on the light sensitive surface, scanning each of the Aplurality of the produced images to produce signals representative thereof, and sequentially altering the amplitude of the produced signals inversely as the product of the spectral sensitivity and the transmission of the light transmitting path for each of the produced images.

34. A color television system comprising a light sensitive surface with a non-uniform spectral sensitivity characteristic, means for sequentially altering the light transmitting path between the object whose image is to be transmitted and the light sensitive surface to produce a plurality of images of different selected spectral color bands of the object on the light sensitive surface, means for scanning each o f the plurality of the produced images to produce signals representative thereof, and means for sequentially altering the amplitude of the produced signals in accordance with a function of the product of the spectral sensitivity and the transmission of the light transmitting path for each of the produced images.

35. A color television system comprising a light sensitive surface with a non-uniform spectral sensitivity characteristic, means for sequentially altering the light transmitting path between the object whose image is to be transmitted and the light sensitive surface to produce a plurality of images of different selected spectral color bands of the object on the light sensitive surface, means 36. `A color television system comprising a light sensitive-electrostatic charge storage surface with a non-uniform spectral sensitivity characteristic, means for sequentially altering the light transmitting. path between the object to be transmitted and the light sensitive surface to produce a plurality of images of different selected spectral A color bands of the object on the light sensitive surface, means for Ascanning each of the plurality of the produced images to produce signals representative thereof, and means for altering the amplitude of the produced signals in accordance with a function of the product of Athe spectral sensitivity and the transmission of the light transmitting path for each of the produced images.

37. In a television receiving system, the method of altering the balance of a received sequential composite video signal having a plurality of series of signal waves, the waves of said plurality of series alternating in regular sequence, which comprises locally changing the relative magnitude of one series of waves in said signal with respect to another series to thereby produce a modined sequential composite video signal similar to said received video signal 'out of altered balance between the series. v

38. In a color television receiving system, the method of altering the color balance of a received sequential composite multi-color video signal the successive portions of which represent diierent component colors which comprises locally changing the relative magnitude of those portions of the received signal which represent one component color with respect to thosev portions representing another component color.

39. In a television system, the combination of means for scanning an object field successively to produce an initial sequential composite video signal having a plurality of series of signal waves, the waves of said plurality of series alternating in regular sequence, and means for subsequently changing the relative magnitude of one series of waves in said sequential composite video signal with respect to another series, whereby a modined sequential composite video signal is produced which is similar to said initial video signal but of altered balance between said series.

40. In a television system, means for sequentially scanning anv object field to produce an initial composite video signal having a plurality of series of signal waves, the waves of said plurality of series alternating in regular sequence, means supplied with said composite video signal foraltering the intensity of the produced signal waves of said video signal in synchronism with the sequential scanning, means for individually controlling the degree to which the signals of one series of said waves are altered with respect to another series of said waves, whereby l a modified sequential composite video signal is produced which is similar to said initial video signal but of altered balance between said series.

4l. In a television system utilizing an initially produced sequential composite video signal having a plurality -of series of signal waves, the

vWaves of said plurality of series alternating in regular sequence,v in combination, amplifying means for said composite video signal, and means for sequentially altering the amplification of said amplifying means in synchronism with the sequential alternations of said series of signal waves to change the relative magnitude of one series of waves with respect to another of said series, whereby a modified sequential composite video signal similar to said initial video signal but of altered balance between said series may be produced.

42,. In a. television system utilizing an initially produced sequential composite video signal having a plurality of series of signal waves, the waves of said plurality ofseries alternating in regular sequence, in combination, amplifying means for said composite video signal, means for producing control impulses alternating in regular sequence, and means for cyclically controlling the amplifiication of the composite video signal by said control impulses to change the relative magnitude of said one series of waves with respect to another series, whereby a modified sequential composite video signal similar to said initial video signal but of altered balance between said series may be produced. v

43. In a television system utilizing an initially produced sequential composite video signal having a plurality of series of signal waves, the waves of said plurality ,of series alternating in regular sequence, in combination, amplifying means for said composite video signal, means for producing control impulses alternating in regular sequence,

. means for cyclically controlling the ampllca- 'color-video signal of which successive portions represent different component colors of an object field, in combination, amplifying means for said video signal, and means for sequentially altering the amplification of said amplifying means in synchronism with the sequential change of color of. said video signal, whereby the magnitude of those portions of the sequential composite multicolor video signal which represent one component color may be altered with respect to those portions representing another component color.

45. In a color television system utilizing an initially produced sequential composite multicolor video signal of which successive portions represent different component colors of an object eld, in combination, amplifying means for said video signal, means for producing control impulses alternating in regular sequence, and means for cyclically controlling the amplication of said video signal by said control impulses to change the relative magnitude of those portions of the video signal which represent one component color with respect to those portions representing another component color.

46. In a color television system utilizing an initially produced sequential composite multicolor video signal of which successive portions represent different component colors of an object eld, in combination, amplifying means for said video signal, means for producing control impulses alternating in regular sequence, means utilizing said control impulses for cyclically controlling the amplication of said video signal by said amplifying means to change the relative magnitude of those portions of the video signal which represent one component color with respect to those portions representing another component color, and means for manually setting the change in relative magnitude produced by the last-mentioned means.

PETER C. GOLDMARK.

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