US2413075A

US2413075A - Method and system for developing television signals

Info

Publication number: US2413075A
Application number: US444651A
Authority: US
Inventors: Otto H Schade
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1941-01-31
Filing date: 1942-05-27
Publication date: 1946-12-24
Anticipated expiration: 1963-12-24
Also published as: US2458649A; GB555565A

Description

Dfn 24, 1946. o. HQ SCHADE METHOD AND SYSTEM FOR DEVELOPING TELEVISION SIGNALS Original Filed Jan. 3l, 1941 3 Sheets-Sheet l ATTORNEY.

Dec. 24, 1946. o. H. SCHADE METHOD AND SYSTEM FOR DEVELOPING TELEVISION vSIGNALS Original Filed Jan. 31, 1941 5 Sheets-Sheet 2 INVENTOR. arm H. .5c/JADE @wm/'f ATTORNEY.

Dec. 24, 194e.. o, H, SCHADE 2,413,075

METHOD AND SYSTEM FOR DEVELOPING TELEVISION SIGNALS Original Filed Jan. 31, 1941 3 Sheets-Sheet I5 Fig. 6 CdM/P55550 VERTICAL BLANK/N6 i vim/FAL RETURN. i i:

. l f nl 1 a'j l e'Il aIJI'IZT-)I Lld l l l Hlm" I I n.; n n L; nuuumn n INVENTOR. afro H. lSCHADE A TTORN E Y.

Patented Dec. 24, 1946 'r oFFic-E METHOD AND SYSTEM FOR DEVELOPING TELEVISION SIGNALS Otto H. Schade, West Caldwell, N. J., assigner to Radio Corporation oi America, a corporation of Delaware Original application Janu 376,770. Divided and t 1942, Serial N0. 444,651

My invention relates to television transmitting and receiving systems and is'more particularly concerned with methods and systems utilizing charge storage pickup tubes for producing television pictures or images in substantially natural i colors by means of lsuccessive transmission of picture or image iield signals generated by scanning an area on which images in selected primary colors are formed. Thus, light from an object may be projected on the area through successively displaced colored filters to develop video signals representative of the colored light pass.- ing through the illters. 'I'he color video signals representing the component colors, when received, produce colored iield images which are eil'ectively superimposed so as to produce` scanned field patterns which when viewed through corresponding successively displaced illters give to the observer the effect of viewing the original object in substantially its natural colors. 'Ihis application is a division of my copending application Serial No. 376,770, filed January 3l, 1941.

More particularly, my invention relates to the production of television picture images in substantially natural color where the control or modulation signals are transmitted and received over a single channel communication system. In its preferred form the system is so constituted utilization of a signal charge storage type of electron beam scanning pickup tube upon which a light image in different selected primary or component colors is impressed in a predetermined sequence of color exposures to. develop signals representative of the individual color fields.

I have found that when utilizing pickup tubes of the charge storage type, such tubes being known in the art as Iconoscope or Orthicon tubes, the signal resulting from scanning a color field by certain methods is modiiled by the previous color to which the light sensitive target had been exposed. As a consequence, color mixing may occur so that the desired si nals are not representative of a single color but o two or more colors.

In pickup tubes wherein the stored charge image isr neutralized by a low velocity electron beam the developed signal is proportional to the charges stored on the target between successive scannings of the same line area. For interlaced scanning this corresponds to the time for scanning two color fields. Thus if the color f the light projected on a photosensitive target is' changed every iield. and the target is scanned by a low velocity electron beam having suillcient ary 31, 1941, Serial No. his application May 27,

45 Claims. (Cl. 178-5.4)

intensity to discharge the scanned areas. an exposure of every line to at least two colors occurs and hence the signal is representative of two successive color fields.

Television transmitting tubes of the photosensitive type inherently have different photosensitivities to light of diierent colors. For this l reason the signal output is not necessarily pro- .that the signal energy is developed through the i portional to the intensity of the light except in so far as this light is monochromatic. Such tubes are usually highly sensitive to red light, moderately sensitive to the blue and may be even less sensitive to green light. The developed signal accordingly varies for a given amount of light depending upon its color, and consequently it is desirable to provide means to control the sensitivity of a television transmitting system to various colors to develop signals and picture replicas representative of the color values and intensities of the original colored image.

It is an object of my invention to provide a system for color television transmission utilizing a charge storage pickup tube wherein the scanned target or light responsive electrode is subjected to successive color iields and wherein the eiiect of persistence of charge due to preceding color fields is minimized or eliminated. Another oblect is to provide 'such a system wherein the charge due to a preceding color field is neutralized prior tothe generation of signals representative of successive picture iields. It is a further object to provide such a system and of the type described wherein the signals representative of the individual color iields may be controlled or varied in intensity or amplitude by manual semi-auto matic or automatic means, andit is a still further object to provide such a system which may be' automatically controlled to compensate for variations in spectral response of the pickup tube and variation in the intensity and spectral distribution of the light source utilized to provide illumination of the colored object of which an image is to be transmitted.

In accordance with one teaching of my invention I utilize a charge storage television transmitting tube having a photosensitive area which1 is subjected to successive differently colored images of a colored object of which a picture is to be transmitted by projecting the light from the object through a rotating .light filter having primary color lters such' as red, blue and green filters to develop electrostatic charges on a target electrode varying in intensity with the colored light passed by the lter. I so synchronize the scanning beam which neutralizes the charges d with respect to the rotation or motion of the lllters that the charges resulting from one color are neutralized prior to the development of charges representative of another color. One oi the simplest ways to follow this teaching of my invention is to mechanically move primary color filters in synchronized sequence into the path of licht between the object and pickup tube and to scan the pickup tube along areas which have been subjected to only one color. A similar combination of primary color iilters may be moved in synchronized sequence in the path of liebt at a receiving location to develop color images corresponding in natural colors to those oi the original colored object. The iilters at the receiver are moved synchronously but with a phase delay of up to one color ileld time, inasmuch as the transmitting tube stores the signal due to each color field prior to transmission. Many forms of auch filters may be provided, one simple form comprising various sectors of a disc rotating ai: e. suitable intensity by providing a standard reference level for white light, to which all signals representative of individual colors bear a definite relation and likewise bearing a denite relation to a condition of zero light intensity. ln this manner the intensity or amplitude or' signals resulting from individual colors may be controlled to obtain signals representative of the original image colors, notwithstanding non-unlformities such as variations in spectral sensitivities of a. single pickup tube or between pickup tubes, and even variations in light sources within a 'time period as short as one line period irrediating the colored object or the spectral distribution of the light source utilized.

These and other objects, features and advantages of my invention will be apparent upon consideratlon of the following description and thei accompanying drawings in which:

Figure l is a schematic diagram of a television pickup tube and an associated circuit suitable for generation of signals representative of .colored images;

Figures 2 and 3 show two types of rotating colored filters for use in the system of Figure l;

Figure i shows a portion of the tube and filter structure shown in Figure 1; r

Figure 5 is an enlarged view of the taraet of the tube of Figure l showing certain operational phases: and

Figure 6 is a series of grauhs showinc relative sional intensities developed by or abolied to the transmitting system shown in Figure l.

I have referred to two tyoes of charze storage pickun tubes, one of whichknown as the Iconoscone. utilizes an electron sca'nniner beam wherein the electrons have relatively blah velocity. being capable of liberatine secondary electrons from the photosensitive target electrode. In this type oi' tube the scanning beam, even in the absence loi? light projected on the photosensitive target,

produces a. background signal because o! nonil 1 uniform redistribution of secondary electrons over the surface of the target. Consequently,

there is no denite relationship between'the in cident light and the signal output in so for as the absolute value of signal output is concerned. Thus, while the output is modulated in accordance with the intensity of light, a definite reference level to which the amplitude of the signals may be referred is lacking. In the second type of tube, however. wherein the target electrode is scanned by a low velocity electron beam, auch as in the zo-called O1-thieme" type. the electrons o( the beam do not reach the target electrode in the absence of light focused thereon. Conso quently, in the absence of light no signal is aenereted andl this feature of the losI velocity tube provides a reference level which may be termed the blacls level of the output signal. Therefore, in. accordance Vvwith my invention, l provide a system capable of producing a reference black level signal and likewise provide means to generate a reference color` signal for each individual color auch as red, blue and steen. The difierence in amplitude between the black reference level and the color reference level is then utilized to control the relative gein or ampllication ci the system for the various colors. Thus in the los? velocity type of charge storage pickup tubes the inherent zero signal with zero illumination provides the zero signal level, where as with the high velocity charge storage type of tube I provide a darlr. aree. on the target which is scanned by the high velocity electron beam, the resulting signal being representative of zero illumination. Furthermore, I provide means to project light of controllable intensity and of successively varying colors on the target to provide a standard signal value corresponding to the particular colors;and still further in accordance with my invention, I completely neutralize the signal charge on a given area. resulting rom one color prior to the generation of charges on this area representative of another color. In this manner I am able to avoid the generation of signals representative of two or more colors which would uro-r duce a mixture of colors at the point o1' recreation of the colored picture replica.

The above-mentioned advantages and features of my invention will be understood with reference to Fig. 1 wherein the television pickup tube i is of the low velocity beam scanning type, being of the type disclosed by Iams and Rose in their U. S. latent 2,213,175 and referred to above as of the Orthicon type. It will be appreciated that a tube of the high velocity beam scanning type may be substituted for the tube i as shown, especlally in view of the description wherein the operational details of these two tube types are contrasted and compared. The tube i contains Y the conventional electron source and control electrode assembly 2, horizontal line deflection plates 3 and the conventional photosensitive mosaic electrode and is surrounded by a magnetic focusing coil 5 and vertical or frame deflection coils 6. The electrons from the assembly E are focused and directed upon the mosaic electrode l and scanned in a horizontal or line direction by the electrostatic deflection plates li in combination with the magnetic field produced by the coil 5, and are likewise scanned over the mosaic electrode in a vertical or frame direction by the magnetic deflection coils 6. Suitable delection potentials may be applied to the deflection plates 3 by a horizontal synchronizing and scanning generator I0, the vertical deflection being produced by currents fed to Ithe deflection coils 8 from a vertical synchronizing and scanning generator I I. 'I'he intensity of the electron beam during discharge of the mosaic electrode is maintained constant, but in accordance with my invention may be changed during the so-called return time by a beam return impulse generator I2, as described in more detail below. A colored image of the object of which an image is to be transmitted such as represented by the object I illuminated by a light source I3 is formed on the mosaic electrode 4 in sequentially varying colors. One convenient method of providing sequential color analysis of the image is shown in Figure 1, I provide a lens system I6 to direct light representative of an optical image upon a mirror I'I located within a cylindrical color filter drum I8; whence the light is projected as an image in proper focus upon the mosaic electrode 4. The filter drum 8, as best shown in Fig. 2, comprises a series of primary color filters such as red, blue and green. I have shown in Fig. 2 a drum including two sets of sequential color filters, the red iilter I9 being followed by a blue filter 20 and in turn by a green lter 2|, the series being repeated at |9a, 20a and 2|a. Obviously, a single or any multiple series of such filters may be used depending upon the desired speed at which the drum is to rotate. Each of the filters I9, 20 and 2| is separated from the other around the circumference of the scanning drum I8 by opaque shutters 22. 'I'he opaque shutters 22 may comprise a portion of the scanning drum framework, although the equivalent of such a shutter may be provided by slightly overlapping adjacent filters, since an overlapping red and blue filter would be substantially opaque to red, blue orgreen light and similarly an overlapping blue and green filter would be substantially opaque to blue, green and red light.

While I have shown in Figs. 1 and 2 the use of a filter drum, an equivalent structure such as shown in Fig. 3 is suitable wherein the filter is of disc formation. Referring to Fig. 3, the filter assembly may comprise a red filter 25, a Iblue filter 26 and a green' lter 2'I separated by opaque sections 28 which correspond to the shutters 22 of the drum type of filter assembly Here likewise the opaque sections 28 may be formed by overlapping the two adjacent color filters as described in connection with Fig. 2. The lter disc may be positioned in a plane parallel and close to the plane of the mosaic electrode, the lateral position of the electrode being shown in Fig. 3 at 4. Obviously, either the drum or disctype filter assembly may be located at another image plane in the lens system, this arrangement being preferable where there is considerable distance between the mosaic electrode 4 and the envelope of the tube I.

In accordance with my invention'the speed of rotation of the lter is so chosen and the width of the shadow cast by the opaque sections between illters is so proportioned as to cover and darken that portion of the mosaic which is being scanned at any instant of time. Thus I synchronize the vertical or frame deflection of the scanning beam so that that portion of the target which is being scanned at any instant of time is unilluminated. This principle of operation may be further explained by reference to Fig. 4 Wherein the filters I9, 20 and 2| are shown projected in a single plane, the mosaic electrode 4 being shown displaced to the right of the filter assembly. Multi-colored light such as representa- 6 tive of the object Il is analyzed by the individual color lters |9-2|, a. shutter 22 casting a shadow 30 over the entire width of the mosaic electrode 4, the arrow 3| showing a portion of one horizontal scanning line in this shadow 30 of a shutter 22. 'I'he electrode beam of the tube thus traverses the mosaic electrode 4 and is deflected vertically in synchronism with the rotation or movement of the lter assembly whether it be of the drum type shown in Fig. 2 or of the disc type shown in Fig. 3. It will be obvious that all elemental areas of the mosaic electrode 4 are sequentially subjected to light of the three primary colors, red, blue and green and that any given elemental areas are subjected to light of only one color prior to scanning. After the areas are scanned, they are then illuminated by a single different color of light. Furthermore, it will be noted that the time to which any elemental areas of the mosaic are subject to light of a given color is the same for all colors so that the charges developed on elemental areas of the mosaic will .be representative of the intensity value of the single color. Thus while the area 32 above the shadow portion 30 is being charged in response to light of` one color such as red, the area 33 below the shadow portion 30 (which has just been discharged by the electron beam within the shadow portion) is being charged by light representative of another color such as blue. In this manner the effect of a mixture of charges is avoided, the signal developed by the scanning electron beam being representative of only one color at any particular instant.

In conventional television transmitting systems it is customary to use what is referred to as interlaced scanning, that is, the electron beam during one portion of the frame time is caused to scan the target in a Vertical direction over one distinct raster. During another portion of the frame time the beam is scanned over a second distinct raster Whose lines are intermediate those of the rst raster. Thus the scanning of evennumbered and odd-numbered lines is alternately performed. The vertical frame is thus divided into two portions referred to as fields, the vertical scanning frequency being twice that ofv normal non-interlaced scanning. It has been considered by those skilled in the art that the application of such an interlaced system of scanning to color television systems is impractical because of the mixing of signals generated by two successive colors. However, it is very desirable to retain interlacing to reduce flicker and transmission band width requirements. Tubes of the charge storage type such as the Iconoscope and especially the Orthicon, referred to above, retain the charge due to light of one color to which is added the charge derived from light of a succeeding color during scanning of the second raster. It is therefore necessary to provide means to discharge the entire mosaic area during the scanning time of one raster to avoid double color exposure. I have found that if the electron beam, instead of being blanked during the horizontal return time, is intensified and simultaneously defocused and deflected over the uncharged intervening areas following the vertical progression of the beam, this difficulty may be overcome.

Referring to Fig. 5,` the electron beam is assumed to be moving during line scansion from the left to the right across the mosaic electrode 4 and during vertical deflection from bottom to top of the mosaic electrode. The electron beam trace 50 shown in Fig. 5 which corresponds to one horizontal scanning line is shown as being in the shadow 30 of the shutter 22. Following each horizontal trace of the electron beam, it is deflected in a direction opposite to the normal vertical deflection, that is, downward in Fig. 5, and follows the path I. Over this path 5I the electron beam is intensied and preferably defocused to discharge the electrostatic charges not previously discharged by the scanning beam during previous horizontal scansions. The amount of deflection in a downward direction is preferably equal to the width of an odd number oi frame scanning lines. It will be appreciated that this applies to an interlaced scanning system of the single interlacing type. However, if a fourto-one interlace ratio is utilized, such as where lines I, 5, 9, etc., are ilrst scanned during one interlaclng ileld, lines 3, 1, II, etc., during the next interlacing iield, then lines 2, 6, I0, etc., and then the remaining lines during the fourth interlacing ileld, it is necessary to defocus or vibrate the beam sufiiciently to discharge all the intervening lines not scanned by the beam during a single raster time. It is not necessary that the return trace 5I as shown in Fig. 5 remain in the shadow of a shutter 22 separating the effective areas of the colored filters.

While I have described the electron beam as returning over an adjacent unscanned interline area, it will be appreciated that the return beam path need not necessarily be over the adjacent unscanned area but over a more distant area. Inasmuch as the electron beam must continue scanning such as at the top of the target shown in Fig. 5 to completely discharge the non-scanned areas adjacent the top, a few horizontal scanning lines and the corresponding time equivalent will be lost adjacent the top of the target. It is therefore desirable to have the return trace of the beam closely adjacent the scanning trace. It is also advantageous to limit the width of the shutters 22 so that the width of the shadows cast by the shutters is less than the vertical space occupied by one to two per cent of the horizontal scanning lines during a single frame period. 'Ihus if the width of the shutter is limited to less than approximately five lines for conventional 44l-line frame scanning, the loss of lines at the top ofthe target is small. I have found a width of the shadow 30 equivalent to three horizontal scanning lines sumcient for good operation.

I have shown the scanning line 5I! as being close to the top of the shutter shadow 30. I

' have found it very desirable, especially in the operation of high velocity beam pickup tubes, to operate in this manner to obtain high sensitivity. I believe this high sensitivity which I have obtained is due to scanning immediately after the light has been removed from the area. to be scanned while the charge storage is a maximum. For this condition it is necessary to synchronize the lter and the vertical deiiection rather closely and have a sharply deilned shadow image of the shutter.

It will be apparent from the above that I have provided means for preventing the generation of signals representative of a mixture of colors. However, in tubes of the type described, the mosaic electrode is usually sensitive to various colors in varying degrees. The red sensitivity of such a mosaic electrode is usually higher than the blue and green sensitivity, and likewise the blue sensitivity is usually higher than the green.

To obtain a standard reference level, especially in tubes oi! the high velocity electron beam scanning type to which the amplitude of the signal generated in response to any color may be re- Ierred, I provide means to provide a minimum or zero signal by casting a shadow over a portion of the mosaic surface preferably over an elongated area parallel with the vertical direction of scanning. With reference to Fig. 1 I may provide a mask 35 directly on the wall of the tube to mask a portion of the light projected on the mosaic electrode and form a shadow 35 over a narrow strip of the mosaic as shown in Fig. 4. The area of the shadow 3B when scanned in a horizontal direction by the electron beam will produce a signal which, in the case of the low velocity electron beam tube, is zero, and in the case ot the high velocity electron beam tube, is of a iinite value. It is not absolutely necessary to provide a mask 35 in combination with the low velocity type of tube inasmuch as the signal in the absence of light or beam current is zero.

By providing this reference value representing zero illumination it is possible to form a relationship between the maximum signal derived from any color with respect to the zero illumination signal. Therefore in accordance with a further teaching of my invention and in order to overcome the disadvantages attendant upon variations in spectral sensitivity of the mosaic electrode and of varying light sources or variations from tube to tube, I provide means to project a controlling amount of light on the mosaic electrode in three synchronized sequential colors.

Thus, referring to Fig. l, I provide a light sourcey such as a color control standard light source or projector 40 to project a narrow band of white light on to the lter assembly I8 and as sequential primary colors upon the mosaic electrode 4. preferably over a narrow section of the mosaic extending in the direction of vertical scanning. The color control standard projector 40 may be provided with-three separately controllable light sources 4I, 42 and 43, each of the sources developing red, blue and green light respectively which is mixed and focused as white light and then passed through the rotating filter I8 as colored light upon the mosaic electrode 4. As the iilter I8 rotates., colored strips of light will be projected on the mosaic electrode so that a red strip of light appears during the time the mosaic is subjected to red light from the object I5 and a blue strip of light when subjected to blue light from the object I5. Similarly, the strip of light will be green during the time the green iilter 2l is opposite the mosaic electrode 4. This strip of light from the projector 40 is shown in Figs. 4 and 5 as a narrow band 45 adjacent the shadow portion 36. For purposes of simplicity in explanation, the shadow portion 36 and colored band of light 45 are shown adjacent one another, my system, however, functioning equally as well whether these bands are separated or at one side of the mosaic or the other. it being only desirable that these bands be parallel with the direction of vertical scanning so that the scanning beam passes over an area in shadow and an area illuminated by one color of light during each horizontal beam scansion.

In the operation of my television transmitting system the signal plate is connected to the cathode circuit of the tube I through an output impedance 55, the signal across this output impedance being fed to a video pre-amplifier 56 such as through a coupling condenser 51 where the signal strength is increased by amplification, whereupon it may be applied to* a further amplifier 58 and toa transmission network, as well known in the art.

Y However, in accordance with my .invention I control the gain of the video pre-amplifier 55 in accordance with the intensity of the light projected on the mosaic by the projector 40 which serves as a reference for automatically controlling the color signal intensity. Therefore, in accordance with my invention, I apply a portion of the output of the video pre-amplifier to a metering tube 59. This metering tube produces an impulse which is proportional to the intensity of lightfrom the projector 4I) focused on the mosaic electrode 4 as the narrow band of light 45 during successive col'or fields. 'I'he tube 58 preferably comprises a cathode 50, an anode 5I, a control grid 52 and a screen or modulating grid 53. It will be obvious in view of the following description that the metering tube 59 may be either a triode or pentode in place of the tetrode type shown. As mentioned above, a portion of the video output from the amplifier 55 may be applied such as through a condenser 65 to the grid 52 of the tube 59. To limit the operation of the tube 59 to a period of time simultaneous with the passage of the electron beam over the lighted strip portion 45 shown in Figs. 4 and 5 I connect the grid 53 'to the horizontal synchronizing and scanning generator which is so designed as to provide a positive pulse during the time the electron beam is passing over the lighted area 45. The output, or ampliiled output ifdesired, of the metering tube 59 representative of the intensity of the colored light projected on the mosaic electrode is applied to a rectifier such as a diode' 55 to rectify the pulsating output which is applied to a condenser 61. 'Ihis output is proportional to the colored light intensity projected on the mosaic electrode 4 as a reference and is applied as an automatic color signal control voltage to the video pre-amplier 55. This control voltage is utilized in the video pre-amplifier to adjust the gain in much the same manner as automatic volume control potentials in a conventional radio receiver, in fact, conventionalmethods known in the art may be provided in the video pre-amplifier for automatic color signal control such that the gain of the ampliiler is increased for low projected intensities of light from the projector 401er decreased for high intensities.

The operation of the circuit shown in Fig. l may be understood more fully by reference to Fig. 6 which shows in sub-Figs. A to G the various wave forms produced and utilized in the circuit of Fig. 1. Referring to Fig. 6, the wave form A represents the output signal appearing across the output impedance 55 which is applied to the video pre-amplifier 56 through the condenser 5l, the condenser 51 having the required value to pass the frequency spectrum of the video signal. The wave form A of Fig. 6 is shown in four representative portions, the first, that portion designated R., being a portion of the horizontal video line signal representative of the signal derived in response to red light from the object I5 being projected through a red lter such as the filter I8 and upon the mosaic electrode 4, it being understood that a portion of the mosaic such as the strip 38 is maintained in shadow. The adjacent strip 45 is illuminated by the red light component of light from the projector 40 likewise passing through the red lter I9. From an examination of the first portion of the wave form A it will be noted that the signal is zero during the time the election that the signal derived from the tube I for the given intensity of the red component of the light from the projector 40 is higher than a corresponding signal produced by the Ablue light component and, similarly, still higher than the signal produced by the green light component. The wave fornrportion c shown in Fig. 6A is representative of the red light component from the object I5 and is the true video 'signal for which transmission is desired. 'I'his video signal is followed by a return line signal d having considerable amplitude inasmuch as the electron beam is intensified during the horizontal return time for the purpose of discharging areas of the mosaic such as interlacing areas by the method described in connection with Fig. 5. The entire line signal is then repeated for the balance of the horizontal line scannings to complete the red color field scanning. `The wave form A is therefore shown discontinuous at e. The portion marked B of the wave form of Fig. 6A is representative of the signal across the impedance 55 during a little more than the last two useful horizontal scanning lines prior tothe vertical return of the beam for scanning the succeeding field subjected to the green light component from the object I5. It will be noted that over the portion a' the video signal is zero as in the caseof over the portion alpreviously described because the electron beam is scanning an unilluminated portion of the mosaic. 'I'he amplitude of the video signal over the portion b is constant and representative of the blue component of light from the projector 40 over the area 45 of the mosaic. As mentioned above, it is here assumed for purposes of explanation that the amplitude of. this b portionis lower than the corresponding b portion representative of the red component in the projected light. The portion c' is representative of the blue component of light from the object I5. 'I'he portion d' corresponds to the signal generated during the horizontal beam return and, naturally, is of high amplitude because of the electron beam intensiilcation during the horizontal return time. As noted above, the portion of the wave fo'rm B representative of substantially the last two useful lines of the blue field is followed by the vertical return of the electron beam prior to the generation of signals during the blue color field. AIt will be noted that this portion of the wave form has been compressed, it being understood that the vertical return time of the pickup tube beam is equivalent to the time occupied by a number of line scannings, this time in practice being approximately five per cent of the field time. During the vertical return the electron beam intensity is reduced to zero so that no signal is derived during this return. In addition, the video signal of several lines before and after the vertical return is likewise blanked such as for the purpose of obtaining a well-defined top and bottom of the recreated picture replica. Vertical blanking is removed at the beginning of the green field, a por tion of which is shown at C+, and the portion b^ l1 is representative of the green component of light lfrom the projector ll. The portion b" is followed as before by the true video silml e" produced by the green light component from the obof the tube 08, the function of which is described below. Therefore the tube is in operation only during the time the electron beam is traversing the illuminated portion 45 of the mosaic electrode. This keying pulse is of constant amplitude for the red, blue and green ilelds and merelyv places the tube 59 in operation so that the output such as in the plate circuit of this tube appears as shown in Fig. 6C. It will be noted that the amplitude of the pulses of Fig. 6C is proportional to the amplitude of the respective portions b, b' and b" for the three colored elds. This pulse amplitude is therefore proportional to the individual colored components of the light from the projector l prior to applying the automatic control voltage, and is therefore a measure of the overall response of the system to a constant value of colored illumination projected on the mosaic. 'I'he tube I8 in conjunction with the resistor 88 periodically provides a discharge path for the condenser I1 so that the condenser vvoltage may instantly be made equal to the metering pulse amplitude within the keying time. The time constant of the condenser i1, tube i! and resistor 89 combination must therefore be given the proper value to meet this requirement. 'I'he rectified wave form of the pulses shown in Fig. 6C is shown in Fig. 6D, this being substantially constant in amplitude and of negative polarity so that when this wave form is applied to the video pre-ampliner i6 an increase in the negative direction reduces the amplication of the pre-amplifier.

The wave forms shown in FigsfoA, B and C are assumed as being generated in the absence of color signal control fed to .the pre-amplifier 56, it being understood that the eflect of the ap plied control will be to decrease proportionally the wave forms for the successive color Iields to a level such that all color control pulse amplitudes shown in Fig. `6C are made substantially equal, their value being adjustable by means of the variable potential source 80 which may be referred to as a delay bias." This automatic control action, therefore, will maintain constant color control pulse amplitude irrespective of changes in spectral response of the pickup tube, transmission oi the iilters or variations of the standard light from the projector l0. Therefore, if the red light component from the color control light source or projector is decreased, the amplifier gain will be raised automatically to the original level, thereby producing a reciprocal increase in the video signal resulting during the red color field. In this manner the ratio of the various colors may be controlled and maintained automatically by a single adjustment of the color ratios oi' the color control light source. For linear transmissh1 ion the color control light source is made pure w te.

It is further possible to utilize my system for automatic compensation for variation in color and intensity of the source oi.' illumination used to illuminate the object of which an image is to l2 directly-from the light source Il used to illuminate the object is diverted, and used in place of the projector Il as a color control standard, variations in both color of light and intensity of light are automatically` and instantly compensated within the time of successive line scannings. The resultant signal is equivalent to that obtained with illumination of the object by a perfectly white light'source oi' exceptionally high stability. y

The wave form shown in Fig. 6E is representative of the vertical scanning current applied to the vertical deection coils l of the tube I. It will be noted that the notches are provided to displace the scanning beam during the horizontal return time in the direction of the previously scanned lines and during the time the electron beam is intensiiied as shown in Fig. 6l". Instead of applying .the notches to the vertical scanning wave form, a separate deflection system may be used to move the beam in a direction opposite to the vertical scanning during the horizontal return time.

It will be obvious that it would be undesirable to transmit a signal corresponding to the wave form shown in Fig. 6A, and portions of this signal are therefore blanked, as well known in the art,

such as by pulses shown in Fig. 6G applied to the ampliiler I8 from a blanking impulse source such as the generator lil. Suitable synchronizing signals are likewise mixed with the transmitted video signal for purposes of synchronizing the receiver with the transmitter.

While I have described my invention in connection with a circuit wherein automatic color control potentials are applied in a negative polarity to the pre-amplifier, it will be obvious thai-.such control potentials may be applied in either positive or negative polarity to any suitable control point in the system. In some applications it may be desirable to provide additional manual control for color response and shading signals such as by keying a number of amplifiers connected in parallel with the color controlled pre-ampliiier. Thus three ampliners may be utilized, each having an individual gain and/or shading control and keyed by a sequence switching network controlled by the vertical synchronizing generator in such a. manner that only one amplifier is operative at a time, the amplifiers being sequentially switched in accordance with the color iields. Thus one ampliiler individually gain controlled may be utilized to control the red response and similar amplifiers for the blue and the green response, the outputs ci these amplifiers being applied in parallel to the transmitting network. Similarly, a single amplifier supplied with keyed gain control signals may be used -to obtain the additional manual color control. In the arrangement a conventional vsequence switching network controlled by vertical synchronizing held impulses may be used to apply to the video amplier a color control bias from each of three manually controlled potentiometers during successive scanning fields, thereby varying Ithe gain of the amplifier during successive fields. In such a system automatic color control may be applied to Athe pre-ampliiler, and the following single amplifier or the three amplifiers in parallel may be individually controlled to obtain abnormal accentuation of various colors.

V While I have indicated the preferred embodiments of my television transmitting system and my method of controlling the accentuation or be transmitted. Thus, if a. portion of :the light attenuation of signals representative of various l. A television transmitting system for developing signals representative of colored optical images including a transmitting tube having a light responsive electrode, an optical system for projecting an optical image `upon the light responsive electrode along an optical axis, a plurality of differently colored light filters, means for successively interposing the light filters in the optical axis to sequentially subject said electrode to differently colored components of said image y in natural color, and a plurality of sources of light each of a different color positioned to project light through the filters onto a portion of the light responsive electrode to provide color reference signal values corresponding to each of said difierent colors.

2. A television transmitting system for sequential color transmission including a transmitting tube having a light responsive electrode, an optical system for projecting along an optical axis light representative of an optical image of an object upon the light responsive electrode, a plurality of differently colored light filters, means for successively interposing the light filters in the optical axis of the television transmitting tube to progressively subject said electrode to differently colored portions of said optical image, and a plurality of sources of light each of a different color corresponding substantially to the colors of said filters positioned on the object side of said color filters for projecting light on a portion of the light responsive electrode.

3. A television transmitting system for sequential color transmission including a transmitting tube having a light responsive electrode, an optical system for projecting an optical image of an object upon the light responsive' electrode along an optical axis, a plurality of differently colored light filters, successive filters being capable of transmitting light of a different primary color, means for successively interposing the light filters in the optical axis of the television transmitting tube to expose the electrode to successive primary colors, a plurality of sources of light each of a different primary color corresponding tothe colors of the filters, the plurality of sources being positioned on the object side of the color filters to project light through said filters and upon a portion of the light responsive electrode to develop color reference signal values corresponding to the intensity of light transmitted through said filters from said plurality of sources, and means for independently controlling the intensity of each of the different sources of light to vary the reference signal values in accordance with the color response of said electrodes.

4. A television transmitting system including a transmitting tube having a light responsive electrode, means in said tube for generating a focused beam of electrons, means for defiecting the beam in horizontal and vertical directions at different rates in order to cyclically scan the light responsive electrode, an optica-1 system for projecting an optical image on the light responsive electrode along an optical axis, a plurality of filters of different colors, means for moving the color filters so that a different color filter is interposed in the optical axis during each vertical scanning cycle of the cathode ray beam, a plurality of sources of light each of a different color positioned to illuminate a portion of said electrode whereby, as a result of scanning said beam over said electrode, signals representative of the intensity of said image and of said plurality. of light sources are developed, a signal amplifying network, and means to control the amplication oi' said network in accordance with the intensity of light from said sources.

5. In a television transmitting system for generating signals representative of colored optical images including a device having a charge storage electrode and means to direct a storage discharging beam upon said electrode, a light filter assembly having a plurality of displaced filters substantially transparent to light of different colors, means to focus light from an object through at least one of the filters of said filter assembly and upon said electrode, means to move said filter assembly to successively interpose said filters in the focused light from said object and form an image of progressively varying color corresponding to the color of said filters on said electrode, means to scan said beam over said electrode and develop signals representative of successive differently colored light focused thereon through said filters, a. source of white light, means to project successive difl'erently colored portions of the light from said source upon the scanned area of said electrode adjacent the area illuminated by light from said object to modify the signals generated by scanning said beam over said electrode, an amplifier associated with said device to amplify the signals developed by said scanning, and means responsive to the signals generated in response to said portions of light from said source to control the amplification of said signals resulting from scanning.

6. In a television transmitting system for generating signals representative of a succession of colored optical images including a device having a charge storage electrode and means to direct an electron beam upon said electrode, a light filter assembly having a plurality of displaced filters substantially transparent to light of difierent colors, means to direct light from an object through the filters of said filter assembly and toward said electrode, means to move said filter assembly 4to expose said electrode to light forming an image of a progressively varying color, the color of said image progressing over said electrode from one side to the other thereof, means to scan said electron beam over said electrode and develop signals representative of successive differently colored optical images focused thereon, means to project successive differently colored light corresponding to the color of light to which said filters are transparent upon a relatively narrow scanned area of said electrode extending substantially from one of said sides to the other to modify the signals generated by scanning said beam over said electrode, an' amplifier associated with said device to amplify the signals developed by said scanning, and means responsive to the signals representative of the .light projected on said relatively narrow scanned area to" control they amplification of said signals resulting from scanning.

7. In a television transmitting system for developing signals representative of colored optical images including a tube having a photosensitive electrode, means to expose areas-oi said electrode to successive dinerently colored optical images of Y Asaid signals, and means to control the amplification-of said signals in accordance with the intensity of the color components of said color control -light beam.

8. In a television transmitting system for developing signals representative of colored optical images including a tube having a photosensitive electrode, means to expose areas of said electrode to successive primary colors oi an image of an object of which a picture is to be transmitted', means to direct a color control light beam on said electrode in successively changing primary colors corresponding in color to the primary color to which said electrode is exposed, means to sequentially develop signals representative of successive primary colors of said object and signals representative of the successive primary colors of said color control light beam, means to amplify the said signals, and means to control the amplification of said signals in accordance with the in tensity oi' the color components of said color control light beam.

9. In a color television transmitting system a tube having a light responsive electrode, an object of which an image is to be transmitted, a source of light to illuminate said object with substantially white light, means to expose areas of said electrode to successive differently colored optical images of said object while illuminated by light from said source, means to project upon a limited area of said electrode a portion of the light from said source in successively varying colors corresponding in color to the color of said optical images, means to develop signals representative of the intensity oi said images and signals representative of the light from said source, means to amplify said signals, and means to control the ampllilcation of said signals in accordance with the signals resulting from the light from said source projected on said limited area.

l0. vlin a television transmitting system for de veloping signals representative of colored optical images including a tube having a photosensitive electrode of the charge storage type and means to develop an electron beam, means to project on a portion of said electrode light representative of an object, movable means to intercept light of various colors from the light incident on said electrode and to progressively expose areas of said electrode to diierently colored components of the light from said object to develop charges representative of the colored light intensity, means to progressively expose another portion of said electrode to light of controllable intensity and of a color corresponding to the color of light from said object incident upon said electrode, means to scan said beam in a plurality of line patterns over said` electrode to develop a series of signals representative of light from said object and signals 'representative of said light of controllable intensity, means to amplify the developcd series of signals, and means to control the amplification of said signals in accordance with the intensity of signals representative of said light of controllable intensity.

i1. In a color television transmitting system a tube having a charge storage light responsive electrode and means to develop an electron beam, an object of which an image is to be transmitted, a source oi' light to illuminate said object with substantially white light, means to progressively expose areas of said electrode to successive diiierently colored optical images of said obiect while illuminated by light from said source to successively develop charges on said electrode representative of the intensity of successive colored images, means to direct upon an area of said electrode a portion oi the light from said source in successively varying colors corresponding in color to the color of said optical images, means -to scan said beam in a plurality of line patterns over said electrode to develop signals representative of light from said object and signals representative of said light from said source, means to amplify the developedfsignals, and means to control the amplication oi' ysaid signals in accordance with the intensity of signals representative of said light from said source.

l2. In a television transmitting system for developing signals i'or color television including a cathode ray tube having a photosensitive electrode adapted to receive images of an object oi' which a picture is to be transmitted, means to form an optical image of an object on said electrode, a illter assembly adapted to intercept light incident onsaid electrode, said assembly including a plurality of displaced light filters capable of transmitting light representative of different colors, means to move said filter assembly to form an image of progressively varying color on said electrode, means to project colored components of white light through the illters of said assembly and upon a limited area of said electrode adjacent the area subjected to said image, means to develop, in a predetermined sequence, a series of signals representative of successive colored images, signals representative of said colored light components and signals representative of zero illumination on said electrode, means to amplify the said developed series of signals and means to control the amplication of said signals in accordance with the difference in amplitude between the signals representative of zero illumination and the signals developed in response to said colored light components.

13. In a television transmitting system including a cathode ray tube having a photosensitive electrode adapted to be scanned by an electron beam, means to form an image of an object of which a picture is to be transmitted on said electrode, progressively moving means to change the color of one portion of the image to a different color, the area exposed to one color progressively decreasing while the area exposed to another color is progressively increasing, means to i1- luminate an elongated area of said electrode with light of controllable intensity and of a color corresponding to the colors of said image, said area extending in a direction perpendicular with the direction of progression of said colors, means to cast an elongated shadow on said electrode parallel with said elongated illuminated area, means to scan said beam in a series of parallel lines across said elongated areas and across the image area intermediate the said two colors to develop sequentially signals representative of zero illumination, the controllable illumination and image illumination, means to amplify said signals, means to separate signals representative li the controllable illumination from the develof a color corresponding to that oi' said images ,developing image and charge signals representative of said images and chargea'and controlling the relative anplitude of said image signals inaccordance with the amplitude of said charge signals.

15. The method oi developing controlled lntensity television signals comprising the steps 18 vision t in natural color comprising the steps of progressively developing over anv area a succession of electrostatic images representative of three successively different primary color optical images, progressively developing from the electrostatic images three sets of image signals, each representative of the intensity oi the primary color, sequentially developing three sets ot color control signals representative of the de slred amplitude o! said respective sets of image signals, and utilizing said sets ot color control signals to control4 the ampliilcation of' corresponding sets of'said image signals.

J 20. The method of producing signals for teleoi' successively developing electrostatic images over an image area representative of successive colored optical images. successively developing electrostatic charges over a control area adiacent said image area representative of light of controllable intensity and of a color correspond- Y ing to that of said images, developing chronologically spaced image and charge signals representative of said images and charges, separating said charge signals from said image signals, and controlling the relative amplitude of said image signals in accordance with the amplitude of said charge signals.

18. 'I'he method of developing controlled amplitude television signals comprising the steps of forming a succession of electrostatic images representative of successive differently colored optical images, simultaneously forming asuccession of electrostatic charges representative of light oi' controllable intensity and o! a color corresponding to those of said images, utilizing .portions of said successive electrostatic images and said successive electrostatic charges to sequentially develop image signals and charge signals, separating the developed charge signals from the image signals, and utilizing said charge signals to control the ampliilcation oi' said image signals.

17. The method o! developing ampliiled controlled amplitude television signals comprising the steps of progressively forming a succession of electrostatic imagesver an image area representative o! successive differently colored optical images, simultaneously forming a succession of electrostatic charges over an adjacent area representative of light of controllable intensity and of a color corresponding to the color of the respective optical image, utilizing portions of each oi' the successively formed electrostatic images and each oi' the successively formed electrostatic charges to develop a sequence of image signals,

charge signals, amplifying the signals, separating the developed charge -signals from the image signals, and utilizing said charge signals to control the amplincation oi' said image signals.

L18` The method of developing signals for television. transmission in natural color comprising the steps of progressively developing over an area a succession of electrostatic images representative of successively diil'erent colored optical images, progressively developing image signals from the electrostaticimages over portions. of said area, developing color control signals representative of the desired amplitude of said image signals, and utilizing said color control signals to control the amplification of said image sig- 19. The method of developing signals for television in color which comprises the steps of progressively developing a cyclically repeating series of electrostatic charge images on a mosaic suri'ace which successively represent a plurality of diilerent primary color optical images, producing trains of image signals successively representing each of the plurality of diiIerent color images oi' the series under the control of the developed seriesof electrostatic charge images, increasing the amplitude of the produced trains of image signals by amplification, and cyclically controlling the degree of ampliiication of each ot the produced trains of image signals.

21. The method oi' producing signals for television transmission in color which comprises the steps of progressively developing a cyclically repeating series of electrostatic charge images on a mosaic surface which successively represent a plurality of different primary color optical images, utilizing the developed series of electrostatic charge images to produce corresponding trains of image signals successively representing each of the plurality oi dlilerent color images of the series, the amplitude of the produced trains of image signals by ampliiication, developing corresponding cyclically varying control potentials, and cyclically controllingthe degree. of ampliilcatlon of each oi' the produced trains of image signals by the developed control potentials.

22. The method of producing signals for television ton in color which comprises the steps of progressively developing a cyclically repeating series of electrostatic charge images on a mosaic surface which represent correspondingly cyclically repeating diil'erent primary color optical images, generating a cathode ray beam, utilizing the generated cathode ray beam to scan the mosaic surface to produce from the developed electrostatic charge images trains of image signals corresponding to the cyclically repeating electrostatic charge images, increasing the amplitude of the produced trains of image signals by ampliilcation, and'cyclically controlling the degree of amplification oi.' the produced trains of image signals.

23. The method o! producing signals for television on in color which comprises the steps ol' progressively developing a cyclically repeating series of electrostatic charge images on a mosaicsurface which represent correspondingly cyclically repeating different primary color optical images, generating a cathode ray beam. utilizing the generated cathode ray beam to scan the mosaic surface to produce from the developed electrostatic charge images trains oi' image signals corresponding to the cyclically repeating electrostatic charge images, increasing the amplitude of the produced trains of image signals by ampliilca'tion. developing corresponding cyclically varyin! control potentials, and cyclically controlling 19 the degree of amplification of the produced trains of image signals by the developed control potentials. s

24. A television transmitting system for producing signals representative of colored optical images including a television pickup tube having a photo-sensitive mosaic electrode, means to expose a predetermined portion of said electrode to cyclically repeating different primary color optical images of an object to thereby develop correspondingly cyclically repeating electrostatic charge images on said electrode, means to generate a. cathode ray beam in said tube, means to scan said electrode by the generated cathode ray beam to produce trains of image signals corresponding to the cyclically repeating charge images,vmeans to amplify the produced image signals, and means to correspondingly cyclically vary the degree of amplification of the trains of image signals.

25. A television transmitting system for producing signals representative of colored optical images including a television pickup tube having a photo-sensitive mosaic electrode, means to expose a predetermined portion of said electrode to cyclically repeating different primary color optical images of an object. of which a. picture is to be transmitted to thereby develop correspondingly cyclically repeating electrostatic charge images on said electrode, means to generate a cathode ray beam in said tube, means to scan said electrode by the generated cathode ray beam to produce trains of picture signals corresponding to the cyclically repeating charge images, means to amplify the produced picture signals, means to generate corresponding cyclically varying control potentials, and means to vary the degree of amplification of the trains of picture signals in accordance with the developed cyclically varying control potentials.

26. A television transmitting system for transmitting images in color including a television pickup tube having a light responsive electrode, means to sequentially project on the light responsive electrode optical images corresponding to different primary color light components of an object to produce on a target electrode corresponding sequential electrostatic charge images representative of the different primary color components, means to generate a cathode ray beam,`

means for scanning a target electrode by the cathode ray beam to sequentially produce corresponding trains of image signals. means including an amplifier for amplifying the Vproduced trains of image signals, means to develop correspondingly sequentially varying control potentials, and means for cyclically controlling the degree of amplification of the produced trains of image signals by the developed control potentials.

27. A television transmitting system for transmitting images in color including a television pickup tube having a light responsive electrode, means to cyclically project on the light responsive electrode optical images corresponding to different primary color light components of an object of which a picture is to be transmitted to cyclically produce on a target electrode corresponding electrostatic charge images representative of the different primary color components, means to generate a cathode ray beam, means for scanning the target electrode by the cathode ray beam to cyclically produce corresponding trains of picture signals, means including an amplifier for amplifying the produced trains of picture signals, optical means to develop correspondingly cyclically varying control potentials. and means for cyclically controlling the degree of amplification of the produced trains of picture signals by vmitted, movable lter means to intercept light of various colors from the light incident on said target electrode to progressively expose areas of said electrode to differently colored components of light from the object to thereby develop electrostatic charge images representative of the colored light intensity, means to scan said target electrode by the generated cathode ray beam to produce a series of picture signals corresponding to the electrostatic charge images, means including an amplifier for amplifying the produced series of picture signals, means to develop cyclically varying control potentials, the cyclic rate of variation of the control potential corresponding to the movement of said lter means, and means for cyclically controlling the degree of amplification of the produced series of picture signals in accordance with the developed cyclically varying control potentials.

29. A television transmitting system wherein a series of image signals are produced representing successive television fields comprising an ampliner for increasing the intensity of the image signals, means for producing a series of impulses of a predetermined frequency and time duration, the time duration of the impulses corresponding substantially to the time represented by each television eld, and means for controlling `the amplication Vof the image signals by the produced series of impulses. f

30. In a color television system having a light sensitive surface with a non-uniform spectral sensitivity characteristic, comprising means for sequentially altering the light transmitting path between an object to be televised 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 of the plurality of the produced images to produce signals representative thereof, and means responsive to the spectral sensitivity of the light sensitive surface for each of the produced images for sequentially altering the amplitude of the produced signals.

31. In a color television system including a television camera tube having a light sensitive surface with a non-uniform spectral sensitivity f characteristic and a target electrode, means for sequentially altering the light transmitting path between an object to be televised and a light sensitive surface to produce a plurality of electrostatic charge images on the target electrode representative of diiferent selected spectral color bands of the object, means for scanning each of the plurality of the produced charge images to produce signals representative thereof, and means responsive to the spectral `sensitivity of the light sensitive electrode for each selected spectral color band for sequentially altering the amplitude of the produced signals.

32. A color television system comprising a light sensitive surface with a non-uniform spectral sensitivity characteristic, means for sequentially objectwhose image is to be transmitted and the 33. A color television system comprising alight 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 diiferent selected spectral color bands of the object on the light sensitive surface, means for scanning each of theplurality of the produced images to produce signals representative thereof. and means inversely responsive to the product of the spectral sensitivity and the transmission of the light transmitting path for each of the produced images for sequentially altering the amplitude of the produced signals.

34. 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 color bands of the object on the light sensitive surface, means for scanning each of the plurality of the produced images to produce signals representative thereof, and means responsive tov a function of the product of the spectral sensitivity and the transmission of the light transmitting path for each of the produced images for altering the amplitude of the produced signals.

35. -In a color television system utilizing a color video signal of which successive portions represent diilerent colors oi' a plurality of colors of an object eld, the method of changing the color' balance of said color video signal which comprises passing said color video signal through an amplifying channel whose ampliilcation' may be varied in accordance with an im pressed control wave and impressing a control wave having control pulses recurring at the fre-V quency of theportions of the color video signal representing one color on said amplifying channel to change the amplication for said portions representing said color with respect to the amplification for portions representing another color, the amplication of the channel for portions representing said one and said other colors yielding corresponding signal portions in the output color video signal of the channel of substantial magnitude.

36. In a color television system utilizing a color video signal of which successive portions represent different colors of a plurality of colors of an object ield, the method of changing the color balance of said color vide signal which comprises passing said color video signal through an amplifying channel whose amplification may be varied in accordance with an impressed control wave and impressing a control wave having control pulses recurring at the frequency of the portions of the color video signal representing one color on said amplifying channel to change the ampli- -22 ncatioh for said portions representing with vrespect to the amplication for portions representing another. color.

37. In a color television system utilizing a color video signal comprising a plurality of color series of signal Waves representing a corresponding plurality of diiferent primary colors of an object field. the signal waves'of said plurality of series alternating in sequence, the method of changing the color balance of said color video signal which comprises passing said color video signal through an amplifying channel whose ampliilcation may be varied in accordance with an impressed con-eA trol wave, and impressing a controlwave having control pulses recurring at the frequency of said signal waves in the respective color series for each of said plurality of color series on said amplify? ing channel to change the amplication thereof for one color series of signal waves with respect to the ampliilcation for another color series, the amplification for both said one and said other color series yielding corresponding color series of signal waves of substantial magnitude in vthe output color video signal of the channel.

38. In a television system utilizing a video signal comprising a plurality of series of signal waves. the waves of vsaid series alternating in sequence, the method of changing the balance 0f said series which comprises passing said video signal through an amplifying channel whose amplification may be varied in accordance with an impressed control wave, and impressing a control wave having control pulses recurring at the frequency of one series of said signal waves on said channel to change the ampliilcation thereof for said one sexies of signal waves with respect to the amplification for another series, the amplification for said one and said other series yielding corresponding signal waves of substantial magnitude in the output video signal of the channel.

39. In a color television system utilizing a color video signal comprising a plurality of color seriesV of signal waves representing a corresponding pilirality of colors of an object ileld, apparatus for changing the color balance in said color video signal which comprises an amplifying channel having an input and an output circuit, means for supplying a control wave having control pulses recurring at the frequency of signal waves in one color series and persisting substantially throughout the periods of said signal waves to said amplification channel to control the ampliilcation thereof, the magnitudes of said control pulses being selectable to alter the ampliiication of the signal waves in said one color series with respect to the signal waves in another color series and to yield output signal waves of said one and said other color series of substantial magnitude, whereby an output color video signal containing a plurality of color series of signal waves with one color series altered in magnitude with respect to another color series may be obpulses being of substantially constant magnitude for the duration of the respective signal waves of said one color series to said amplier tube in phase with the signal waves of said one color series to control the amplification of said tube during said series and thereby control the magnitude of said one color series with respect to another color series in the output color video signal of the tube, the Waves of said one and said other color series being of substantial magnitude in said output signal.

41. In a color television system utilizing a color video signal comprising a plurality of series of signal waves representing a corresponding plurality of different primary colors of an image iield,- 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 combination, a signal channel containing an electronic amplier tube and input and output circuits therefor, said input circuit being connected to receive said color video signal, means for supplying a control wave having control 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 throughout a field scansion, to said ampliier tube in phase with the signal waves of said one color series to control the amplification of said tube to alter the magnitude of said one color series with respect to another color series in the output color video signal of said channel, the waves of said one color series being of substantial magnitude in said output signal. l

42. In a television system utilizing a video signal comprising a plurality of series of signal waves, the waves of said series alternating in sequence, apparatus for changing the balance of said series which comprises an electronic ampliiler tube connected to be fed with said video signal and adapted to produce an output video signal, means for supplying to said ampliiier tube in phase with the signal waves of said one series a control wave having. control pulses recurring at the frequency of signal waves of one series and persisting substantially throughout the periods of said signal waves to control the amplincation of said tube during said series with respect to the amplification of the tube during another series, the amplification of said tube for said one and said other series yielding corresponding signal waves of substantial magnitude in the output video signal, whereby the balance between said series in the output video signal may be changed from the balance between the corresponding series in the input video signal.

43. In a color television system utilizing a 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 field scansions of substantially equal length, apparatus for changing the color balance in said color video signal which comprises, in combination, a signal channel containing an electronic amplifier tube and input and output circuits therefor, said input circuit being connected to receive said color video signal, means for supplying a control wave having a plurality of series of pulses equal in number to said plurality of color series, the pulses in each series recurring at the frequency of the signal waves of the corresponding color series and each pulse being of substantially constant magnitude for a field scansion to said amplifier tube in phase with the color video signal to control the ampliiication thereof, variable means for controlling the relative magnitudes of the plurality of series in said control wave, the magnitudes of said color video signal and the series of said control wave being selected so that the signal waves of each color series are of substantial magnitude in said output circuit, whereby an output color video signal similar to the input color video signal but `of adjusted color balance may be obtained.

44. In a color television system utilizing a color video signal comprising a plurality of color series of signal waves representing a corresponding plurality of diilerent primary colors of an object 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 an electronic vacuum tube having a control grid and an output circuit, said tube being of the variable-mu type whose amplification factor varies markedly with a change in control grid bias, means for impressing said color video signal on said control grid, means for impressing on said control grid a control wave having a. plurality of series of pulses, the pulses in each series securing at the frequency of the signal waves of the corresponding color series and each pulse being of substantially constant magnitude for the duration of the corresponding signal wave, variable means for controlling the re1- ative magnitudes of the plurality of series in said control wave, the series of pulses in said control wave being in phase with the respective color series and the magnitudes of said color video signal and the series of said control wave being selected so that the waves of each corresponding color series are of`substantial magnitude in said output circuit. whereby an output color video signal similar to the input color video signal but of adjusted color balance may be obtained.

45. A television transmitting system for transmitting images in color including a television image pick-up tube having a light responsive electrode with non-uniform/spectral sensitivity characteristics, means to sequentially project on the light responsive electrode optical images corresponding to different color components of an object to sequentially produce on atarget electrode corresponding electrostatic charge images representative of the different color components, means to generate a cathode ray beam, means forscanning the target electrode by the cathode ray beam to sequentially produce corresponding trains of image signals, means including an amplifier for amplifying the produced trains of image signals, and means responsive to the spectral sensitivity of the light responsive electrode for each of the optical images for sequentially controlling the gain of the ampliiier.

OTTO H. SCHADE.