US2415059A - Television system - Google Patents

Description

Jan. 28, 1947. v. K. zwoRYKlN TELEVISION SYSTEM Filed Oct. l5, l1944 4 Sheets-Sheet l ATTORN EY 4 Sheets-Sheet 2 AVAVAVAYA'AF V y v v v v AAAAA VVVVV V. K. ZWORYKIN TELEVISION SYSTEM Filed Oct. 13, 1944 INVENTOR ATTORNEY AAAAA Jan. 28, 1947. v. K. zwoRYKlN 2,415,059

TELEVISION SYSTEM Filed Oct. 13, 1944 4 Sheets-Sheet 3 o A /V -I INVENTOR BY M f ATTORNEY 4 Sheets-Sheet 4 v. K. zwORYKlN TELEVISION SYSTEM v Filed Oct. 13, 1944 INVENTOR ATTORNEY Patented Jan. 2S, 1947 T E S 2,415,059 TELEVISION kSYSTEM of Delaware Application Gctober 13, 1944, feralgNo. 558,508

la Claims.

This invention relates to televisionsystems and particularly to television systems wherein additive tricolor images `are developed.

:In the past, various proposals for vachieving color television have been made and among these proposals have been those wherein an electronic image producing tube oi the cathode ray type has been `provided lfor the target formed from a series of :built-up strips or the like which are individual-ly caused .to luminosos in dilerent co-mpement colors of an additive system. Among these proposals, there has been one exemplified by U'. S. Patent No. 2,310,863, granted to H. W. Leverena'which discloses a cathode ray tube havingratoneend a target formed from a plurality of strips fof light `:producing ,luminescent compounds adapted to produce red, green and blue light When activated ,by a cathode ray or an electron scanning beam appropriately directed thereupon.

According to the present proposal for eiecting additive color television, reference will be made by Way of example to a tricolor system and to' ,one utilizing the tube of the general characteristics set forth by the aforesaid Leverenz patent.. :In thisgeneral arrangement, provision is to be emade :for scanning'the -independent strips of :luminescent material of different character placed adjacent to each other in such a manner `that ,the scanning occurs in a direction substantially lengthwise of the strips, in which case it may .be assumed, -for illustrative purposes, that the strips I extend in ldirections corresponding to those along `which the several lines forming the `totalscanning'raster are developed. Of course, it will be appreciated that the system herein to be ydisclosed in no Way is limited to tricolor television for the ,principles herein to be disclosed nd equal application in bicolor or multi-color sys- .tems with appropriate modifications made to -accommodate the control system to the decreased or increasednumber of color scannings.

In accordance with the arrangement herein to be set forth, provision is made for tracing the luminescent strips of the target area by a cathode ray beam which is signal modulated and where the signal modulation is such that the modulated beam represents a signal which would have been produced at the transmitter by light of a color corresponding to that developed at the receiver by an electron beam impacting a strip of luminescent material of a particular character. The invention further carries forward the feature oi providing accurate registration of the -color scannings in :such a Way that the scanning electron beam or cathode Vray ls accurately maintained instantaneously and for each line of scan-ning on one onlyfof the luminescent strips of the vcolo-r series during each scanning operation. Provision is made for controlling the operation in the event that the scanning becomes distorted due to inaccuracies of scanning beam deflection whereby signal modulation which is intended to portray red, for instance, in the nal additive image shall cause the impacting beam to strike red responsive areas only on the target and if, by chance, green or blue responsive areas of the target are impacted, then through appropriate and coordinated control arrangements, the deflection path preferably is automatically modied to :correct for the displacement of the scanning beam in order that accurate `color representations may take place. `In this way, accurate and proper synchronization as to color is obtained at the receiver end of the system with regard to the transmitter end of the system and due to the rapidity of scanning repetitions from: one to anotherof .thecomponent colors of the additive systern, the color sensation is evoked in the brain of the observer.

It, therefore, becomes an object of this invention to provide a system of additive color television `wherein accurate registration of the separate color images is maintained at all times.

It is =a further object of this invention to prf vide for increased accuracy of scanning deflection in a color television system and to prevent the fusion eiect .of different color representations and intermodulation of diiierent color producing media tending to give false color ezdects.

Other Aobjects of .the invention are to provide a color television system in which light losses are reduced to a yminimum due to the .elimination of filters and the like so that it is possible not only to produce color images which appear to come ,directly from the viewed image producing tube 4but also to provide for producing television images in color in such a manner that the resultant images may be projected and yenlarged for viewing purposes.

Another object of the invention is that of providingacontrol system 4by which tricolor or mul- .ticolor television images may be developed and controlled purely Yby electronic means so that scanning traces arelconned to substantially only vthe desired color instantaneously to be portrayed.

A further yobject oi the invention is that of Aproviding a compensating system to correct electronically -ior any variances or departures from .correct color scannings and to provide for such purpose purely electronic switching means which fi shall be effective to control the color registration in accordance with the color instantaneously intended to be portrayed.

Still another object of the invention is that of providing purely electronic compensation means whereby auxiliary control of the deflection in at least one direction oi a cathode ray beam may be provided to compensate automatically for variances in correct color registration.

Other objects and advantages of the invention are to provide a system of color television serving more accurately to portray the color representations and at the same time, to provide for more efficient operation than has heretofore been made possible in systems of the additive type utilizing color filters mechanically driven for exhibiting and revealing the color effects tothe eyes of observers.

Still other objects and advantages of the invention are those of overcoming one or more known. defects in existent systems. Still other objects and advantages of the invention will become apparent and those suggest themselves to those skilled in the art to which the invention is directed, and the following specification and claims are considered in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic representation-of one form of circuit arrangement utilizing an all electronic control system; Fig. 2 is a plan View of a target element upon which the color image appears, it being understood that the gure is not according to scale; Fig. 3 diagrammatically represents one form of switching arrangement and control pulse producing circuit for carrying forward the invention diagrammatically explained by Fig. 1; Fig. 4 shows the group of curves to explain the operation of the circuit of Fig. 3; Fig. 5 is a modiiication of the system explained by Fig. 1 with the modification using a combination of electromechanical-optico means to accomplish the aims and objects obtained with the electronic arrangement of Fig. 1; and, Fig. 6 is a schematic representation of a illter element used in combination with the photoelectric deflection controlling tubes of Fig. 5.

Now referring to the drawings for a further understanding of the invention, and first to Fig. 1 thereof, it is intended that the nal electrooptical image which is to be viewed shall appear on a target element or screen area II formed at one end of an image producing tube I5 which is of the cathode ray type. To form the scanning raster or pattern of the image, there is developed within the tube I5 an electron scanning beam I1 originating from the conventionally represented electron gun structure I9 so as to strike upon the target area II.

As was hereinabove suggested, the target area II is formed as a plurality of coatings of luminescent material formed either upon the inner surface of the end Wall of the tube or upon a separate internal target electrode. Where desired, the target surface may be formed as particularly exemplified by the Leverenz patent, #2,310,863, granted February 9, 1943, and hereinabove referred to. When a tube of this character is utilized, the impacted target area, as represented schematically by Fig. 2 of the drawings, is formed to include a plurality of strips of luminescent material such as those conventionally represented by the strips 2l, 22 and 23, for instance, and assumed to produce upon activation by an electron beam light and three chosen component colorsred, blue andgreen, for instancaoian additive color system. While various forms of luminescentl compounds may be used, there may be mentioned herein, purely by Way of example, that the red eiects may be obtained by coatings of chromium activated aluminum berylliate or zinc cadmium sulde activated by silver. The second color effect, such as thc green, may readily be obtained from the luminescent material coating formed from alpha-willemite activated with manganese and Zinc cadmium sulfide activated with silver. Lastly,- the blue luminescent effects may readily be obtained through the use of coatings formed from silver activated zinc sulfide, zinc silicate and zirconium silicate. The foregoing forms of the luminescent materials have been suggested by the Leverenz patent. Therefore, the showing of Fig. 2 will be considered merely as illustrative of one form of a tube target area and the showing of Fig. 1, insofar as it concerns the tube element itself, may also thus be regarded purely as schematic.

During the course of producing the electron beam I'I within the tube it is caused to move laterally of the screen or target area II in a direction substantially lengthwise of the luminescent strips 2I, 22, 23, etc., under the control of suitable deflection coils 25 and 26, which have been schematically shown. The motion of the beam Il in an up and down direction or in a direction transverse to the strips of the target is provided by the so-called vertical deecting coils 2l and 23. When suitable currents flow through the vertical and horizontal deflecting coils, the scanning beam Il is caused to trace a suitable scanning raster on the target area in a wellknown manner. If the scanning beam during these traversals of the target is modulated by a signal representative of the red image at the time the beam impacts the red responsive strips 2I, for instance, and if the beam then is modulated by signals representative of the green image during time periods when the scanning lbeam impacts green light producing strips 22 of the target, etc., it can readily be seen that colored images will result. To this end, the scanning traces on the target may be such that all red responsive strips of the target are scanned in sequence with the green and the blue having been skipped, and this scanning is followed by a scanning of either the green or the blue responsive strips to be followed by the third heretofore-omitted strip for each produced iielcl so that the color sequence appears from iield to field. This is one suitable form for the scanning operation. Alternatively the beam ll' may be deflected in a direction normal to the arrow shown on Fig. 2 so that one after another of the color strips are scanned and the color blending takes place from line to line of the scanning operation. For purposes of illustration only, the latter form of scanning pattern will herein be assumed in what is to follow.

At times when colored images are to be developed on the target II of the tube I5, signals representative of the videol or image modulation accompanied by sync signals and any necessary control signals may be assumed to be received by radio or wire link connecting to the receiver ampliiier and demodulator unit 3l from the output cf which signals are fed to a suitable amplifier and signal separator 33. These units are of well-known form and require no further illustration other than the note that the separated video or image signals may be fedv or supplied by way of the connecting line 35 in any approprid ate manner to modulate the electron beam il developed in the tube l5.

The separated sync signals (such as the form recommended by present standards) derived from the output of the ampliiier and signal separator unit 33 may then be supplied by way of conductors 3l and 39 to control the operation of the horizontal deflection source ll and the vertical deection source Lil-i, respectively. The de ection sources for horizontal and vertical are also of well-known character and need no cletailed description other than to make mention of the fact that they may be assumed to include a suitable form of relaxation oscillator unit and appropriate ampliiiers for supplying the resultant signal to the vertical or horizontal deilection coils (as indicated) and also subject to being triggered or controlled as to operation periodically by the sync signals (such as shown by curve A of Fig. 4:) supplied through the indicated conductors 3l and 39.

Thus, by well-known means, the developed electron beam Il may be caused to sweep the target area il of the tube i5, and images in color readily result. It, however, frequently happens that the linearity oi deiiection trace is not sufficiently accurate to reta-in the modulated electron beam on the desired individual color responsive scanning strip. Various causes for this lack of registry may be found but it frequently happens that supply uctuatiohs in the power supply cause different beam velocities in the tube so that the tube sensitivity varies, or frequently modulation of the beam tends te cause at times some defocusing effects and still other g causes may prevent continuity or beam registry at the desired strip.

The arrangement ofl is intended to i; sure pro-per registry of the scanning beam on the desired scanned strips at all times. tially, the circuit schematically shown by Fig. l., with the further explanation which will be had from a later consideration of Fig. 3, and the eirplanatory curves of Fig. fi, shall be considered as providing suitable controls oi a purely electronic nature to correct automatically for variances ci the deiiection trace from the desired strip area, such as those represented, for instance, by Fig, and the paths or sections 2i, S22 and 23 ier red, green and blue scannings, respectively.

To effect a control of the nature desired, it may be assumed that the cathode ray tube l5 is pro vided with suitable Windows spaced substantially equidistant one from the other about the tube periphery. These Windows may, where desired, be in the form of lenses lll, and they serve essem tially to gather the light from the impacted surface of the target area li and to direct that light to a plurality of photocells herein generally des ignated as 49, '5l and 53 respectively which will herein be assumed to respond to the red, the greenand the blue lights produced on the target area. The selection of the color of light to which each of photocells 49, 5i and 53 (each essentially of a panchromatic response variety) responds is determined by a hlter element interposed between each photocell and the optical element or win dow M through which the photocells receive light from the tube target. Under these conditions, it may be assumed, for instance, that the filter ele-- ment 55 is red so as to pass red iight to the photocell 4?: and to produce thereby output responses from the photocell during red light activation but to preclude response of the photocell 49 to either the green or the blue light. Simih Essen i larly, the lter 51- positioned intermediate the photocell 5l and the target area Il may be assumed to be green so as to pass green light to the photocell El but to exclude red and blue lights, Where red, green and blue, for instance constitute the chosen component or primary colors. Likewise (although not shown in detail for reasons of simplification of drawing) another filter is so positioned relative to the photocell 53 that this photccell may be considered as responding to blue light but to produce substantiallyr no response to red or green light.

The photocells lid, 5l and 53, when subjected to light of the color passed by the associated hlter produce output currents which flow in the conductors 59, iii and 63, respectively, to output amplier tubes 65, 5l' and iid, respectively, which may be assumed to amplify signals representative of red, green and blue.

The tubes 55 are usually of either the pentcde or the screen grid variety so that they serve as mixer tubes in such a way that the color responsive output from the photocells may be applied as a positive voltage, for instance, upon the control electrode thereby to control the output current flowing and the tube may similarly be controlled by a signal applied from a control source to the screen electrode so as thereby to govern the time periods during which the tube can be made responsive. Signals of this character are applied to the tubes B5, El, and Eil respectively by way of the terminal input points 'l l, 'i3 and 15 so that at times when control voltages are applied at the input terminals, the tubes may be rendered operative or inoperative in accordance with the applied control to illustrate one form of control. The tubes may be considered as being biased and maintained at a predetermined normal state of operation to pass and amplify signals from one of the photocells to an output circuit which shall receive signals and be controlled in accordance with the current iiovving in the ase sociated photocells. However, at times When a signal or control wave of negative polarity is applied at one of the terminals ll, T3 or l5 the associated tube will be biased to a eut-od state.

The control circuit arrangement of Fig. 3 and the explanatory curves of Fig. 4 related thereto will later be discussed, in detail, but, for the moment, it may be assumed the control voltages applied to govern the operative periods of the tubes 65, El and Gil shall be developed from the control unit more particularly shown by' Fig. 3 in such a Way that waves such as L, N and M (see Fig. 4 particularly) shall be applied as control voltages at the terminals l l, 13 and l5, respectively.

It was above pointed out that this invention Was to care for departures of the scanning trace from the desired color responsive strips so that if it was intended instantaneously to scan a red light producing strip (such as the strip 2| of the target, for instance) then, any departures of the scanning beam from this area would be such that the scannig beam should impact a blue or a green area of the target Il and should initiate thereby automatically a control signal which would modify the normal deflection of the scanning beam il so as to place the beam back upon the desired red strip assumed. Accordingly, if the order in which the strips are arranged from the top of the target area toward the bottom, as shown by Fig. 2, is such that the order becomes red, green, blue, red and so on, then, if it is intended that the' green strip be scanned, it will be appreciated that insucient deflection of the scanning beam 'lv in thelownward direction across the target area would permit the beam i1 instantly to impact a red responsive strip but excessive deilection would cause the beam instantly to impact a blue strip. Under such circumstances, if the scanning beam il is intended to scan instantaneously a green strip 22 but it departs therefrom for one cause or another it means that either the red or the blue responsive photocells 49 or 5I will receive light through the appropriate associated light filter and thereby produce an output current flow in either of the tubes 65 or 69, provided that the control voltage applied at the terminals Il and 15, for instance, is not instantly of such polarity as to interrupt the tube response. On the other hand, for the instant that the green strip of the target is being scanned, no output from the control photocell 5| will be desired in that this happens to be the photocell which should continuously receive green light provided an absolutely correct scanning trace deflection is maintained. Consequently, in accordance with the invention, a control voltage may now be supplied to the input terminal 'I3 for the tube 61 which shall apply a negative bias on the tube 6l of such value as to interrupt completely the output current flow from the tube by biasing it to cut off, even in spite of the fact that input voltages are applied by way oi conductor 6|.

With the assumed arrangement of the color producing strips of the target, it will be appreciated that inadequate deflection of the scanned beam at the time when it is desired to scan a green strip (such as the strip 22 of Fig. 2) should lbe supplemented by an additional control signal which shall move the scanning beam downward on the target to position it over the green strip, but if there has been too rapid a deflection so that the scanning beam touches a blue responsive strip area then a control should be applied to the deilection voltage which will reduce the amount of deflection oi' the beam in the vertical direction. Consequently, during periods when the green strip is being scanned. for instance, a response from red light responsive photocell i9 would in dicate that the deflection was not suiiiciently rapid because the scanned beam would in. tantaneously be scanning a color strip which precedes that desired. On the other hand, at time periods when it was intended that the blue strip should be scanned, a response from the red light responsive phctocell t3 would indicate that the beam was moving across the target area too rapidly at the vertical deiiection so that a signal should be applied to reduce the amount of mit the beam to be slowed in its vertical direction of motion (transverse tothe strip length) and return to the green strip. Accordingly, certain time periods exist when output currents from the various amplifier tubes 65, 67 and G9 must be used to amplify or increase the deiiection of the beam; and at other times, this output signal must be used to decrease the deflection so that there is developed from each tube two outputs which may be assumed to be of positive polarity where increased deilection is required and negative polarity where decreased deflection is desired. To this end, the output from the tube 65 is fed to a pair of amplifiers 'Il and lB, as conventionally illustrated, which may be assumed to be any ordinary form of cascade amplier which can be ccntrolled by virtue of a control somewhat similar to that shown in connection with the tube 65, for instance, to control the periods of operation or interruption. Normally, it will be assumed that the amplifiers 1l and iii are biased to a cutoff state, so that a positive control signal or control voltage is required for the rst stage, thereof at least to produce any response in the nal output. The control voltages which are applied to the amplifiers 'il and i9, which are connected in the so-called red channel, are impressed at the input terminals Bl and 83. These control voltages may have the wave forms indicated respectively .by the curves H and K of Fig. fl, while thc signal or control voltage applied to control the in operative periods of the tube 65, and which voltages are applied at terminal il, is preferably of the wave form indicated by curve L of Fig. 4. Similarly, with the assumed order of color responsive strips, the amplier 6l which amplies the output from the photocell 5l may be assumed to be inoperative by reason of the signal applied at terminal i3 during periods when green is normally scanned. For the assumed operation the control signal applied at terminal i3 may be one corresponding to the wave i'orm N of Fig. 4 which it will be seen is negative for certain time periods during which the wave form L applied at terminal H is a positive polarity, as will be the case of the control signal applied in a manner later to be described upon tube ES. Arranged similarly to the amplifiers 'il and i9 associated to the output tube G5, there are two amplifiers 85 and 8l, having an even number of stages and an odd number of stages respectively, which receive output signals from the tube 5l. Separate control signals are applied to the ampliiiers 85 and -S'i from terminal points 89 and 9i so that one or the other is unblocked at certain time periods to amplify and relay the output signals from the tube El for controlling or modifying the action of vertical deflection source 33.

Again, the output from the tube 159, which is assumed to be representative of a blue signal, feeds to two amplifiers 93 and 95 having an even number of stages and an cdd number of stages respectively, so that signals of one blue or the other will result therefrom during operative periods of the said ampliiiers. Control voltages for controlling the operative periods of the amplers 93 and gli are applied at control terminal points 97 and 99. The control voltages applied to all of the ampliiiers generally correspond to the wave forms indicated by letters adjacent thereto and are of the general form shown by the diagrams of Fig. 4. As was the case above described for ampliers 'il' and 'i9 or [i5 and Bl, one or the other of the ampliers 93 and 95 is operative during periods when the tube 59 is capable of transmitting amplified phoiocells out put currents from the photocell 53 to these units.

Thus, with the switching arrangement more particularly exemplified by Fig. 3, it is apparent that wave forms of the type shown by Fig. 4 will be available to control the ampliiier tubes 65, Si and 6l) on the one hand, and the plurality of amplifiers il, 19, t5, di', 93 and 95 on the other hand. The controls which are effective will be assumed, for the purpose of illustration, in the present case to be operative upon a time base wherein 6U image frames (120 image holds) each of 525 lines are to be reproduced each second and each of the selected red, green and blue images is to be reproduced 20 times per second, for instance. Where desired, the red, green and blue fields may be scanned by well-known nterlacing methods so that eiectively, there will be transmitted during each second 2O interlaced elds representative of each of the red, the green and theblue component color images. It is to be understood that this rate of transmission is merely submitted by way of illustration and other rates may be utilized without in any way departing from what is herein set forth and shown as the broad principle of operation. In considering the control wave forms, it will be appreciated that each of the wave forms L, N and M herein assumed to control the operative periods of the red, green and blue amplifier tubes 65, 6'! and S9, respectively, is so arranged that the wave has substantially zero amplitude for two successive line periods to be followed by a line period when the wave is negative so as to be'capable of cutting oir the amplier. On the other hand, the waves G, K and H, which are the waves from which the control waves are developed, have substantially zero amplitude for two line periods to be followed by a positive pulse lasting for any substantially one line period so that by utilizing these pulses to control the amplifiers Tl, le, 85, 93 and 95, the time period of operation for each amplifier may be regulated. In arriving at these time cycles, it is to be understood that during the period when the red amplifier 55 is inoperative, it is desirable that the blue amplifier 95, which is intended to add a positive or increased deflection wave, shall be operative to amplify any outputs for the tube 69 so that it may be controlled by the wave form G, as will be the green ampliiier 85 serving to provide for decreasing the rate of deflection. Similarly, during periods when a green strip is intended to be scanned and the amplifier 6l is'rendered inoperative under the influence of the wave form N, it is desirable that the red amplifier 19 which is to add to the deection shall be operative, as will be the blue amplifier S3 which is to subtract from the deflection, so that under such conditions, these amplifiers may be controlled by the wave form K. Lastly, during periods when the blue amplifier 69 is rendered inoperative by reason of the application of the control wave M to the control point T5, it is desirable that the green amplifier 37 which will add to the deflection shall be operative, as well as the red amplifier l1, which will subtract from the deection; and accordingly, during these time periods, the wave form I-I of Fig. 4 may be utilized to control the operative periods, as above explained.

From the foregoing, it is apparent that at any instant, two of the group of amplifiers controlled by the wave forms G, H and K are operative, and the outputs from all of these amplifiers are supplied by way of the conductors lill to the vertical deiiection source 43. It is, of course, evident that where a green strip is intended to be scanned, if the scanning pattern departs therefrom so that the beam impacts a red strip rather than a green, the impacting beam will not reach the blue strip so that there will be produced an output from only one of the amplifier units which is rendered operative during the time period when there is no output available from the green photocell and its amplier. Thus, at any instant, there is combined with the wave output from the vertical deflection source only al single additional wave which is of the character to add or subtract from the defiecting wave normally produced in order that the beam may be rendered to its proper path. One suitable means to accomplish this control and for producing the control waves indicated is shown by Fig. 3 and will now be explained in relationship to Fig. 4 of the drawings.

Referring now to Fig. 3 of the drawings, the switching control there shown schematically represents one suitable form for an impulse generating and control system for use in connection with a. tricolor television image producing system in which the separate color components are changed for each line scanning cycle. In other words, a diierent color component of the composite television image is presented for each line scanned. Therefore, if the eld frequency of the color television system is cycles (60 frames) per second and each frame is a 525 line image, it is evident that each individual color producing path of the composite color television image target is scannedat a rate 31,500 lines per second.

The impulse generating and switching control systel l shown in Fig. 3 is based upon the disclosure of F. J .Somers in United States patent appli-cation Serial No. 417,295, filed October 31, 1941. Essentially, it includes an amplifying tube it which is preferably of the screen grid type and which includes at least a cathode, a control electrode and an anode. The cathode of tube M3 is connected to ground |84 by cathode resistance lt' which is by-passed by an appropriate condenser |07. The anode is maintained positive with respect to its associated cathode by means of a load resistance connected between the anode and terminal |89 to which a source of positive potential is connected. The control electrode of tube |513 is connected to ground through an appropriate grid resistance lil and negative impulses of television line frequency are applied to the input terminal ||3 in order that they may be impressed upon control electrode of tube m3 by way of condenser I I5. These impulses may be of the form shown in curve A of Fig. e and are indicated by a like letter in Fig. 3. The tube |03 functions as an amplifier tube so that these same voltage variations appear at the anode of the tube with their polarity reversed so that the separate impulses extend in a positive direction as indicated by curve B of Fig. 4. In Fig. 3 all letters used indicate wave forms which are formed in Fig. 4.

An electron nipulsecounter device is provide which includes a duoble diode tube ||'l', is provided as a part of the circuit. The anode of diode section Il!! and the cathode of diode section |2| are connected together and are coupled to the anode of tube |03 by Way of a relatively small condenser |23. The anode of diode section ii is connected directly to ground Imi whereas the cathode of diode section H9 is connected to ground through a condenser |25,

In view of the fact that the condenser |23 is relatively small, a certain differentiating effect is produced so that the voltage variations appearing at the anode of diode section H9 and the cathode of diode section |2| may be of the general wave form shown in curve C of Fig. 4. The voltage variations which extend in a negative direction are substantially eliminated through the snorting effect of the diode l2| where they are passed to ground, whereas the voltage variations which app-ear in a positive direction operate to produce a charge on condenser |25, Each time an impulse, (that is, a sync signal, for instance) is applied to the control electrode of tube |93, the voltage variations which appear at the anode of diode H9 cause a positive charge t0 accumulate on the condenser |25. Unless this charge is removed,` it will continue to accumulate in a stepwise fashion as indicated in the curve shown at D in Fig. 4 until it is approximately equal to the peak positive portion of the wave shown at C in Fig. 4.

The circuit also includes a discharge tube |21, which includes an anode, a cathode, and a control electrode, and, in addition, there is provided a multi-vibrator circuit comprising tubes |29 and |3| which are preferably each of the screen grid type. The cathodes of tubes |29 and |3| are connected to ground while the control electrode of each is connected to the screen grid electrode of the other by means of coupling condensers |33. The screen grid electrode of tube |29 is also connected to the anode of the discharge tube |21 and the anode of tube |29 is connected to the cathode of diode ||9 and to the control electrode of the discharge tube |21. The cathode of tube |21 is normally maintained at a positive potential with respect to ground by means of a potentiometer |35 so that, in View of this positive potential, the tube is normally non-conductive but is rendered conductive when the potential applied to its control electrode is made suiciently positive.

Inasmuch as the control electrode of tube |21 is connected to the cathode of diode |9, the control electrode is maintained at a potential corresponding to the charge on condenser |25. As this charge increases in a positive direction in a stepwise manner, as explained above, eventually the potential of the control electrode of tube |21 will reach a point where the tube is rendered conductive. This point is determined by the setting of potentiometer |35 and for best operations is chosen such that the tube |21 will become conducting when the charge potential on condenser |25 reaches a point represented by the dotted line X which is applied to curve D in Fig. 4. If the tube |21 is to become conductive on the third charging impulse (as shown in Fig. 4) then the bias of the tube should be such as will prevent operation of the tube until after two charging impulses. The bias should then be set at a value corresponding to a potential about half way between the potentials produced by two and three charging impulses.

Since the screen grid electrode'of tube |29 is connected to the anode of tube |21, and the anode of tube |29 is connected to the cathode of diode H9, conduction of tube 21 also initiates a conduction in the plate circuit of tube |29 which permits the charge on condenser |25 to Ibe substantially completely removed by current flow through tubes |21 and |29. It will be noticed that the source of positive potential of the plate of tube |29 is derived only from the chafrge on condenser |25 and by reason of the circuit arrangement just dened, the plate circuit of tube |29 is permitted to become conductive only when its screen grid is supplied with an impulse from tube |21.

Tubes |29 and |3| function as a multi-vibrator and are made alternately conducting and nonconducting by reason of their particular connections. Inasmuch as multi-vibrators are well known in the art, these connections will not be described herein with any further detail.

Since the alternate operation of tubes |29 and |3| is controlled by the charge on condenser |25, the voltage variations appearing at the anode of tube |3| will, therefore, have a frequency of 10.500 impulses per second (assuming image elds at 525 line elds per second with 31,500 control pulses applied to terminal H3 and assuming that each third impulse causes operation of multi-vibrator tubes |29 and |3|). A potentiometer |31 is provided for adjusting the Lif() Y electrode of tube |45.

width of these impulses so that their duration is controllable. Voltage variations appearing at the anode of tube |3| will then have a general wave form such as shown in curve E in Fig. 4. This wave form is substantially rectangular but includes certain undesired signals or irregularities which for best operation of the system should be eliminated, These voltage variations are then applied to the control electrode of tube |39, the bias on the tube being such that the undesired negative peaks shown in curve E are eliminated since tube |39 is rendered non-conductive at such times.

There, therefore, appears at the anode of tube |99 a voltage variation such as indicated in curve F in Fig. 4. To eliminate the undesired peaks associated with this substantially rectangular voltage variation, the impulses are applied to tube |4| so that at the anode terminal |152 of the last named tube impulses are present such as shown at curve G in 4. The voltage variations available at the anode of tube lill include, therefore, only impulses of rectangular wave form, the impulses (the positive wave form) occurring at the line frequency rate and each having the indicated time duration and spaced from each other as indicated. These pulses are utilized, as will later be mentioned, to circuit arnpliiiers and 95 (Fig. 1) as previously described.

The cathode of diode |19, as stated above, has a voltage variation such as indicated at curve D in Fig. 4.. These voltage variations are also applied through condenser |42 to the control The load circuit of tube |45 is connected between ground and the cathode of the tube so that the output of the tube may be derived from its cathode. The voltage variations appearing at the cathode of tube M5 are, therefore, substantially identical to those appearing at the cathode of diode H9. These Voltage variations are then applied to the control electrode of tube |41 which includes at least a cathode, a control electrode and an anode. The potential of the cathode is made positive by a predetermined amount as determined by the setting of potentiometer Uli! so that the tube is normally non-conductive but is rendered conductive when the potential of its control electrode is made sufficiently positive. Normally, the potential of the cathode 4of tube |41 is so adjusted that the tube will be rendered conductive at a potential such as that indicated by the dotted line Y shown associated with curve D of Fig. 4. The anode of tube 41 is maintained positive by a load resistance m9 which is connected between the anode terminal |5| to which a source of positive potential is applied. There, therefore, appears at the anode of tube M1 a voltage variation which is substantially rectangular in wave form and which has a frequency of one-third that of the line frequency impulses applied at the input terminal H3. These impulses have a duration of l/nm of a second since impulses of this frequency are assumed to be applied to the input terminal H3. After appropriate amplification and clipping by means of tubes |52, |53 and |55, there will be produced at the anode terminal |51 of tube E55 a voltage variation such as that shown in curve H of Fig. 4. It will be noticed that the voltage variations of curve I-I are similar to those of curve G but are displaced in phase relationship such that the impulses available at terminal |51 of the tube |55 precede the voltage variations available at output termilli nal M2 ofthe tube lili by l/aitnnul second according to the assumed operating conditions.

For producing the third series of impulses, a pair of tubes |59 and l5! is used with each tube preferably including at least a cathode, a control electrode and an anode. The cathodes are connected to ground lil!!- Whereas the control electrodes are supplied With the produced voltage variations from tubes le! and |55. The output fromtube Ml is applied to the control electrode of tube itil by way of conductor |53 and capacitor |55 Whereas the output from tube |55 is applied to the control electrode of tube |59 by Way of conductor |51 and capacitor |59. The anodes of these tubes are connected together and have a common anode resistance l'll by means of which the anodes are maintained positive with respect to the cathodes by voltage available at the terminal |13. Since the impulses available at the anode terminals |42 and |51 of tubes Ml and E55 extend in a positive direction, as indicated by the curves G and H of Fig. 3, tubes ll and Ide, respectively, are rendered conductive during these intervals. During the remaining interval when no positive impulses are applied to the control electrodes of either of tubes 59 and 16| neither are conductive and, accordingly, a voltage variation will appear at the anodes of tubes |59 and lill which is of rectangular form with the impulses of the voltage variations extending in a positive direction and each occurring during the intervals when no impulses are supplied by either of tubes lill or |55. After appropriate amplication and clipping in tubes H and ill, there then appears a voltage variation at the anode terminal Iii-l of tube Hl similar to that shov/n by curve K of Fig. 4. These voltage variations are applied at terminals 33 and Si and ampliers 7B and 93 (as explained in Fig. l). The voltages so developed and shown by curve K are similar to the voltage variations available at the anode terminals |52 and |51 of tubes itl! and 55 except that the y impulses constituting the voltage variations are displaced in phase relationship.

There are then available from the anode terminals |li2, |51 and l'l'B of tubes lili, |55 and |ll voltage variations of rectangular wave form having an impulse frequency equal to one-third line frequency. that is, 19.50() and each displaced by 120 electrical degrees from the other for the assumed line and frame or held frequency. These control impulses may then be used to control the operation of the amplifiers used to pass the output of the photocells il, lil and 5s to control the operation of the supplemental voltage production to add or subtract from the normal deflection as above mentioned and described by Fig. 1.

In the previous lconsiderations of Fig. 1, it has been pointed out that at the time the red ampliner 65 is rendered inoperative by reason of the application of the negative control pulse such as that represented by the curve L of Fig. 4, it is desirable that one or the other of the ampliners 85 and 87 connected to receive the energy output from the tube El shall be operative and similarly, one or the other of the amplifiers S3 and 55 connected to receive the output from the tube el? shall be operative. Accordingly, an additional inverting stage is connected in the channels from which each of the signals G, H and K have been derived to control the operation of the amplifier 11, 79, 85, Si, S3 and 95 and from these inverting stages, signals corresponding to the Wave forms L, M, and N of Fig. 4 are obtained 14 to be used, as above experienced, to control amplifiers 55, 69 and G1. To this end, a stage of amplioation represented conventionally by the output tube |8| is connected to receive at its input a Wave form substantially like that available at output terminal |42 and corresponding to the wave form G. In view of the inverting effeet of the tube 8|, there will be available at the output terminal W3 a Wave form suchas that represented at L in Fig. 4 so that the Wave is what might be conventionally considered as oi Zero amplitude for two-thirds of its cycle and of negative amplitude for the remaining one-third of its cycle with the negative amplitude being considered adequate to apply a blocking bias on the screen electrode of the tube 55, for instance.

For convenience and in order to obtain an adequate negative value for the Wave L, an adjustable volume control or potentiometer arrangement has been illustrated although not in any way essential to the operation, provided its circuit constants are adequately chosen. Similarly, a Wave form having the general characteristics of the wave H of Fig. 4. but of opposite polarity is derived by means of the inverting tube |81, to the input of which the Wave form His applied so that at the output terminal |89, a wave similar to Wave M will be available and this will function an amplier 59 in the manner already explained in connection with the foregoing discussion relative to the waves G and L. As was the case with the wave L, the Wave M may be controlled as to its amplitude by means of the volume control or potentiometer lili and the Wave M may then be supplied, for instance, to control the operative periods of the tube 5S through the connection at terminal l5. Lastly, an inverting tube |93 is provided to receive at its input a wave corresponding to the Wave K so that at the output terminal |955 an inverted Wave like that shown at N in Fig. 4 will be available with the amplitude again being controlled by means of the volume control or potentiometer 91. The Wave N may then be applied to terminal T3 to regulate the operative periods of the tube 6l'.

With the arrangement as hereinabove described, it can be seen that during the period when the Wave L is applied at terminal 'il to regulate the operative and inoperative periods of tube 65, the wave form G will be applied to the amplifier 95 and the amplifier B5 to permit these ampliiiers to operate at such time periods but no output will be available from either ampliiler l1 or T9 during the inoperative periods oi amplifier S5. With the Wave K applied to ampliner 93 and the Wave H applied to amplifier 8l, it is apparent that each of these Wave forms being conventionally represented in Fig. 4 as oi zero value during the negative excursions of the Wave L, there will be no sufcient positive voltage applied to either of ampliiiers 8'! or 93 to render it operative so that under such conditions (that is, inoperative periods of amplifier 55), the only amplifiers that are capable of passina signal into conductor lill to control the vertical deection source 43 are those ampliers to which the wave form G is applied, namely, ampliers B5 and 95. The other connections indicated herein will naturally follow and need not be explained in detail except to note that if the order of scanning is as above statedrect green, blue, red, green and so on--and the wave form L is applied to amplier (l5, the wave N applied to amplier 6l and the wave M applied to amplifier l 69, then the controls of amplifiers T1, 19, 85, 81, 93 and 95 will be under the iniiuence oi. the waves H, K, G, H, K, G, respectively, and the operation as above outlined will be obtained.

A modication of the arrangement shown by Fig. 1 is exemplified by Fig. 5 and also, the control iilters for use with the arrangement of Fig. 5 are shown more particularly by Fig. 6. If reference is now made to Fig. 5 for an understanding of the modified form of invention, it will be seen that in this arrangement, the electrooptical image, which is reproduced in color, is also arranged to be produced and to appear on the target element or screen area ll formed at one end of an image producing cathode ray tube l5. Within the tube l5, as was the case with Fig. l, an electronic scanning beam is developed and emanates from a conventionally represented electron gun I9 so as to strike upon the target area li. Deiiecting coils 25 and 25 for effecting horizontal or line traversals of the target by the scanning beam Il are conventionally represented as are the deflecting coils 2l' and 2B assumed to deflect the scanning beam Il along a vertical path or is at least a path transverse to the .line pattern. The scanning raster or pattern area is thus developed by the beam I l striking the target when that beam is controlled in its motion by the deflecting iields.

The target il is formed in the same general manner already explained in connection with the representation of Figs. l. and 2 and the beam l'i is intended to scan the target strips lengthwise for each line of the produced pattern. In the modified arrangement of Fig. 5 also, signals are received on the receiver amplifier and demodulated in the arrangement conventionally represented at 3| so that these signals may be then fed to an amplifier and signal separator 33. Although not shown, audio signals may be separated directly following the demodulator and video and sync and other control signals may be 'separated in the amplifier and signal separator 33, as indicated, so that the video signal may be applied in well known manner to control the modulation of the cathode ray beam ll. Like wise, as explained above, sync signals may be supplied by conductors 31 and 38 to control thel horizontal and vertical beam deflection control sources il and 43.

In the modied arrangement of Fig. 5, a different system has been shown to insure that registry of the scanning cathode ray beam always takes place at the desired strip of the target area and. further, in Fig. 5, suitable correcting circuits for correcting the deflection trace automatically upon a departure of the scanning beam from the desired color responsive area are disclosed. Again, in Fig. 5, the corresponding circuits set forth are connected to respond in accordance with the output current flowing. from photoelectric tubes 22e and 25| connected to energize amplifiers 253 and 255, the output of which are fed by way oi conductors 51 and 59 to add or subtract from the normal voltage fed from the vertical deflection source |53 to the vertical deflecting coils 21 and 28. Thus, if it be arranged so that the amplier 253 causes an increase in the instantaneous voltage applied to the vertical deecting coils, it will be appreciated that the beam will be moved one way from its normal deflection arrangements if the output from the ampliiier 255 supplies to the vertical defiecting coils a voltage which is phase opposed to the output from the vertical deflection source 43, then it will be appreciated that there is less voltage across theA coil and the beam ll will tend to move over the target in exactly the opposite sense to that which would be produced by an increase in voltage. Accordingly, if provision is made :for activating or influencing the photo- electric tubes 249 and 25| by light of one of the two colors not intended instantaneously to be represented as an optical image, then it will be appreciated that output current flows from either ampliers 253 or 255 only at times when the scanning beam Il moves remotely from the light producing strip instantaneously intended to be scanned. For this purpose, there is positioned immediately between the photo cells 259 and 25| and the light image producing target area l of the tube I5 a suitable iilter element 25| which is shown by way of ex ample in greater detail in Fig. 6 and which will be referred to more specically later.

Each of the filters 26| is positioned upon a driven shaft element 253 so as to rotate, for instance, in the direction shown by the arrow and each disk may be driven by means of the unitary connection diagram shown by the dot and dash lines from a signal synchronized drive motor 265. This drive motor which is controlled as to its operation by means of signals supplied to it, for instance, by way of conductor 261 from the amplier and signal separator unit 33. Thus, the motor unit 255 may be driven and controlled to rotate at any desired speed which is commensurate with the signal and suitable gearing may be provided between the motor 265 and the drive shaft 263 so as to rotate the filter discs 26| at the desired speed, as will be later explained.

In the operation of the system, when a light image is produced upon the tube target that image is directed not only directly outwardly from the tube but is also directed through the lens elements |65 and 21| through the lter discs 26| and thence, by way of the masking apertures 2`a'2 and 2'53 in the masi-z elements 2M and 215 so as to reach the photoelectric cells 249 and 25|- Thus, if instantaneously a red section of one oi the two nlter discs 25| is interposed in the light pattern between the tube target I and the photo cell, it will be appreciated that the photo cell will respond to red light but becomes unresponsive to the blue or the green due to the ltering effect of the disc 25|, To accomplish this objective the lter discs 26|, as can be seen from Fig. 6, are formed to include a multiplicity of red, green and blue lter areas 271, 218 and 219 respectively. These nlter sections are preferably arranged as sectors of the nlter disc with the arcuate or angular extent of each sector being determined largely by the size of the complete filter disc. In the preferred form, the separate filter sections of different color transmission properties are separated one from the other by opaque or black areas 25|, as indicated. These opaque arrangements may generally be constituted as being of such arcuate or angular extent that when the filter element 26| is rotating on its shaft or support spindle 253 relative to the photo cell 249 or 25|, the black er opaque section of the disc will mask any light at all from the photo cells during the period of rapid snap-back of the scanning beam in its .rapid return motion in one direction of scanning according to present practices.

If now, to provide the control above outlined, the scanning beam 7 may be assumed to be tracing a red responsive strip 2| of the target area H, for instance, then the lter disc 26| which is positioned imnediately in front oi the photo cell 249 may be assumed to be in such position that a green area 218 of the disc is just being revealed to the photo cell at the time the scanning trace on the red image producing strip 2| starts at the left. The lter disc 26| also shall be assumed to be rotating on the support spindle or shaft 263 at such a rate that one filter section only moves across the photo cell during the time of scanning one line. As the lter disc has been schematically illustrated by -Fig. 6 it is provided with twelve complete lter sectors so that it will loe seen the disc would rotate once during the scanning of each twelve lines of the image area on the tube I5.

With the second filter disc 222i! which is to re veal the light on the target area l-l to the photo cell being of like character to that interposed in the light path to the photo cell M9, it will be appreciated, similarly, that if a red responsive strip 2| oi the target area is being scanned, the disc 2M positioned in the light path to the photo cell 25| may be so positioned that will reveal to the photo cell, 29| the light ci only a blue image. Thus, at the instant when the scanning of a red strip 2l is initiated, a blue :filter section 219 of the lter disc 26! will be interposed in the light path between the target area i l and the photocell 25| The filter` discs 26 |l are driven as uni-controiled elements from the signal synchronized drive Inotor 265, as schematically illustrated, with the phasing of the two ilter discs relative to other set, as above indicated. lt will be app/ree ciated that so long as the scanning beam hereinabove assumed for illustrative purposes as traversing the red responsive strip El remains on red responsive strip, no light whatever wouid reach either the photocell Zit or the photocell 25| because of the instantaneous interpositioning of green and blue filter sections in the light path to these photocells. However, if the vertical motion (the motion transfers to the strips El, 22, 23, etc.) is non-uniform for any reason so that the scanning spot or beam il happens to impact or strike a green responsive strip 2?. during the time period it was intended to be striking the red strip 2l, then some light will reach the photo cell 249 through the green lter section and pro duce an output from the amplier 293. However, il? the scanning spot happens to be distorted in its projection pattern toward the target ll so that it strikes a blue responsive strip 23 while it should have impacted a red responsive strip 2l, then by reason of the blue lter section being interposed in the light path to the photocell 25| during such time periods intended for red scanning, there will be an output signal produced from the photocell 275|.

In any event, whenever light reaches, either photocell 249 or 25|, signals will result and output currents will flow from the amplifiers 253 and 255 to be additively combined with the voltages causing currents to flow through the deflecting coils 2l and 2E. Obviously, since one amplifier is to add to the deflection energy and the other is to subtract from the amplifiers 253 and 255 will be out of phase one with another and that the added increments combined with the normal deflection voltages will continue only during the period when the scanning spot or beam ll has departed from its intended and normal trace pattern.

As soon as the scanning ci the red responsive strip 2| is completed, the scanning beam ll will move to the next adjacent strip, such as the green strip 22 on Fis. 2, and, by this time, the

lter discs 5| will have rotated so that at the start of the green scanning, a red lter section of the disc, for instance, will mask the light which would otherwise reach the photocell 2tlg and likewise,` a blue lter section will be interposed in the path of the light to the photocell 25|, and the control will be as above outlined. During the time when blue scanning traces are intended to be made on the target area ll, then it may be assumed that a red filter section will be interposed in the light path to the photocell @d and a green illter section will be interposed in the light path to the photocell 25|, after which the initial sequence hereinabove mentioned Will be repeated.

While the arrangement has been illustrated as comprising a control eiect through the use of a photocell and associated amplifier it will be apparent that there may be substituted for the photocell and its amplifier a single electron multiplier tube in which the electron ilow is initiated by impinging light. Similarly, in lieu or" the illter discs hereinabove suggested. Three separate photocells may be provided with a different character iilter interposed between each and an amplier associated with each. Then, by the provision of a cyclically operative switching or commutating means, such as an electronic switch, two of the photocells may be operative (in the gen eral manner above outlined) to supply an output to the deflection circuit to add or subtract volt ages therefrom while the third (that correspond" ing to the color instantaneously to be reproduced) will be disconnected from the scanningf circuit.

Other and various modications, oi course, may readily be made and will suggest themselves at once to those skilled in the art to which the invention is directed, and it is to be believed that the claims hereinafter appended should be considered broadly in view of the probability oi such modications.

Having now described the invention, what is claimed and desired to be secured by Letters Patent is the following:

l.. In a tricolor television system wherein additive color images are produced with the three component colors of the additive system being sequentially and. cyclically produced in a line-forline manner on a target element of a cathode ray tube, said target being 'formed in a repeating series of strip elements where each series includes at least one strip area producing light, under electron scanning beam activation, in each selected component color, and in which a signal modulated scanning beam is appropriately deflected relatively rapidly along substantially linear paths lengthwise of each oi the several color strips in sequence and is also deected transversely to the strip lengths so as to pass progressively from one color scanning to another, he combination comprising a plurality of light sensitive elements of a number corresponding to the number of component color strips in each series oi the target area to receive lights resulting upon electron beam impact on the target, means to produce output currents measured by one light color only from each of the light sensitive elements, means to render the input signals from one of the light resistive elements ineffective in an output circuit while the output of the other two is useful, means to utilize the instantaneous useful output of the said light sensitive elements to accelerate or decelerate the transverse deflection of the scanning beam in accordance with departures thereof from the color strip instantai9 neously intended to be scanned so as to retain the instantaneous line deection path of the scanning beam on a desired color strip area, and means cyclically to switch between instantaneously useful and ineffective light sensitive controls.

2. In a television system including a cathode ray tube having a target area formed from a repeating series of light producing elongated strip areas so arranged that each series includes a plurality of strips adapted individually to produce light under an electron beam impact in one of a plurality of selected component colors and so positioned that all selected component color lights are produced by the strips of each series and also including a line deflection system to deflect the electron beam lengthwise of the strips to scan the several strips in a line-for-line manner to produce light of a color corresponding to the component color strip instantaneously impacted and a eld deflection system to deflect the electron beam relatively slowly, as compared to the line deiiection rate, along a path substantially normal .to the strip length to cause the scanning progressively and cyclically to change from one to another of the component colors of the strips, the combination comprising a plurality of photoelectric tubes positioned to receive light from the target area, means cooperating with the photoelectric tubes to produce output currents therefrom at time periods when the scanning trace departs from the instantaneous line path normally desired to be followed in accordance with desired electron beam deflection so that undesired color responses from other component colors are instantaneously developed, means controlled by the output currents flowing from the photoelectric tubes during said time periods to accelerate or decelerate the eld deilection of the cathode ray beam to restore beam registry on the color strip area instantaneously intended to produce light, and means for cyclically switching the control and operative periods of the photoelectric tubes between different colors of the component series to establish the control for all colors of light in the series.

3. ln a tricolor television system wherein additive color images are produced by sequentially and cyclically developing light intensities representative of an image in three selected component colors of an additive system and wherein the light values are sequentially and cyclically produced in a line-for-line manner on a target element of a cathode ray tube in which a signal modulated cathode ray scanning beam is appropriately deected along substantially linear paths longitudinally of a series of different component color light producing strips of which the target is formed and wherein the beam is relatively slowly denected transversely to the strip lengths so as to pass progressively from one color scanning to another,l the combination comprising a plurality of photoelectric tubes to receive light produced as a result of the target scannings by the scanning beam, filter elements for restricting the light upon each photoelectric tube to a single component color light and to influence each tube by light of a diilerent color, switching means to render ineffective the output of one of the photoelectric tubes receiving light of a color corresponding to that instantaneously intended to be developed to a zero value and for providing output from the other photoelectric tubes in accordance with any light developed instantly in the undesired component colors to which the other tubes instantaneously respond, means to utilize the photoelectric tube outputs representative of instantaneously undesired component color outputs to accelerate or decelerate the transverse deflection of the scanning beam in accordance with departures of the scanning beam from the color strip instantaneously intended to be scanned so as to retain the instantaneous line deflection path oi the scanning beam on a desired color strip area, and commutating means for cyclically and sequentially switching the photoelectrlc tubes, and the control on deilection exercised thereby, between operative and inoperative conditions as the transverse scanning progresses.

4. In a tricolor television system wherein additive color images are produced by sequentially and cyclically developing light intensities representative of an image in three selected component colors of an additive system and wherein the ligi-it values are sequentially and cyclically produced in a line-for-line manner on a target element of a cathode ray tube in which a signal modulated cathode ray scanning beam is appropriately deflected along substantially linear paths longitudinally of a series of different component color light producing strips of which the target is formed and wherein the beam is relatively slowly deeoted transversely to the strip lengths so as to pass progressively from one color scanning to another, the combination comprising a plurality of photoelectric tubes to receive light produced as a result of the target scanning-,fs by the scanning because, iilter elements for restricting the light upon each photoelectric tube to a singie component color light and to influence eachv tube by light of a diierent color, switching means to render the effective output of one of the photoelectric tubes receiving light of a color corresponding to the instantaneously intended to be developed ineifective and for providing output from the other photoelectric tubes in accordance with any light developed instantly in the undesired component colors to which the other tubes instantaneously respond, means to utilize the photoelectric tube outputs representative of instantaneously undesired componet color outputs to accelerate or decelerate the transverse deilection of the scanning beam in accordance with departures of the scanning beam from the color strip instantaneously intended to :be scanned so as to retain the instantaneous line deflection path of the scanning beam on a desired color strip area, and means for cyclically and sequentially switching the photoelectric tubes, and the control in deflection exercised thereby, between operative and inoperative conditions as the transverse scanning progresses.

5. In a television system including a cathode ray tube having a target area formed from a repeating series of light producing elongated 00 strip areas so arranged that each series includes a plurality of strips adapted individually to produce light under an electron beam impact in one of a plurality of selected component colors and so positioned that all selected component color o5 lights are produced by the strips of each series and also including a line deflection system to deflect the electron beam lengthwise of the strips to scan the Several strips in a line-for-line manner to produce light of a color corresponding to the component color strip instantaneously impacted and a field deflection system to deflect the electron beam relatively slowly, a-s compared to the line deilection rate, along a path substantially normal to the strip length to cause the scanning progressively and cyclically to change aiiaoe from one to another of the component colors of the strips, the combination comprising .a plurality of photoelectric tubes positioned to receive light from the target area, means cooperating with the photoelectric tubes to produce output currents therefrom at time periods when the .scanning trace departs from the instantaneous line path normally desired to be followed in accordance with desired electron beams deflection so that undesired color responses from other component colors are instantaneously developed, and electronic commutation means to supply the output currents flowing from the photoelectric tubes during said time periods to the field deliection circuit to accelerate or decelerate the deflection of the cathode ray beam to restore beam registry on the color strip area instantaneously intended to produce light.

6. In a tricolor television system wherein additive color images are produced with the three component colors of the additive system being sequentially and cyclically produced in a linefor-line manner on a target element of a cathode ray tube, said target being formed in a repeating series of strip elements vwhere each series includes at leastone strip area producing light, under electron scanning beam activation, in each selected component color, and in which tube a signal modulated scanning beam is developed to impact the target, the combination comprising line deflecting rmeans for sweeping the scanning beam along the said strip so as to scan the same, eld deecting means for deflecting the scanning beam in a path normal to the strip lengths, to cause the scanning to shift progressively from one to another ofthe selected component colors, a plurality of light sensitive elements of a number corresponding to the number of component color strips in each series of the vtarget area to receive light resulting upon electron beam impact on the target, means to produce output currents measured by one light color only from each of the light sensitive elements, means to render the output signals from one of the light sensitive elements ineffective in an output circuit while the output of the other two is useful, means to combine the instantaneous useful output of the said light sensitive elements with the energy in said field deecting means so as accelerate or decelerate the transverse deflection of the scanning beam in accordance with departures thereof from the color strip instantaneously intended to be scanned so as to retain the instantaneous' line deflection path of the scanning beam on a desired color strip area, and means cyclically to switch between instantaneously useful and ineective light sensitive controls.

7. In a tricolor television system wherein additive color images are produced by sequentially and cyclically developing signals representative of the light intensities of an image in three selected component colors of additive system and wherein the developed signals are sequentially and cyclically produced in a line-for-line manner on a target element of a cathode ray tube in which a signal modulated cathode ray scanning beam is appropriately deflected along substantially linear paths longitudinally of a series of diierent component color light producing strips of which the target is formed and wherein the beam is relatively slowly deflected transversely to the strip lengths so as to pass progressively from one color scanning to another, the combination comprising a pair of photoelectric tubes to receive light produced .as a result of the target scannings by the scanning beam, rotary lter elements each including lter seotions of each component color, said lters being positioned and arranged to rotate relative to the photoelectric tubes so as to restrict the light instantaneously reaching each photoelectric tube to a single component color light, said lter elements being phased so as to influence each tube by light of a dierent color` so that the output of the photoelectric tubes is representative of colors corresponding to light colors instantaneously intended to be remote from the scanning beam line trace so that any output developed instantly is representative of an undesired beam deflection, means to utilize the photoelectric tube outputs thus representative of instantaneously undesired component color outputs to accelerate or decelerate the transverse deection of the scanning beam in accordance with departures of the scanning bearn from the color strip instantaneously intended to be scanned so as to retain the instantaneous line deilection p-ath of the scanning bearn on a desired color strip area, and means for rotating the iilter elements at like speeds and with constant phase diiferences for cyclically and sequentially the color light effective upon the photoelectric tubes to control the effect exercised thereby in the deflection.

8. In a tricolor television system wherein additive color images are produced with the three component colo-rs of the additive system being sequentially and cyclically produced in a linefor-line manner on a target element of a cathode ray tube, said target being formed in a repeating series of strip elements where each series includes at least one strip area producing light, under electron scanning beam activation, in each selected component color, and in which a signal modulated scanning bea-m is appropriately deflected relatively rapidly along linear paths lengthwise of each of the several color strips in sequence and is also deilected relatively slowly transversely to the strip lengths so as to pass progressively from one color scanning to another, the combination comprising a plurality of light sensitive elements to receive light resulting upon electron beam impact on the target, means to produce output currents measured by one light color only from each of the light sensitive elements, means to utilize the instantaneous useful output of the said light sensitive elements to accelerate or decelerate the transverse deflection of the scanning beam in accordance with departures thereof from the color strip instantaneously intended to be scanned so as to retain the instantaneous line deflection path of the scanning beam on a desired color strip area, and means cyclically to modify the effective outputs from the said light sensitive elements so that the instantaneously useful output to control electron Ibeam deflection results from departures of the scanning beam scanning an instantly desired color responsive strip area to one of the other light color producing areas.

9. In a tricolor television system wherein additive color images are produced with the three component colors of the additive system being sequentially and cyclically produced in a linefor-line manner on a target element of a cathode ray tube, said target being formed in a repeating series of strip elements where each series includes at least one strip area producing light, under` a modulated electron scanning beam activation in desired brilliance for each selected component color and in which the signal modulated scanning beam is appropriately deflected sequentially and relatively rapidly along substantially linear paths lengthwise of each of the several color strips of each series and is also deflected relatively slowly transversely to the strip lengths so as to pass progressively from one color scanning to another, the combination comprising a plurality of light sensitive elements to receive light resulting upon electron beam impact on the target, filter means to limit the component color light effect to reach the said light sensitive elements so that the said elements develop output currents measured by the component color light reaching said elements through the filter means, means to so control the resultant output signals from the said light sensitive elements that during scanning one component color output energy from the light sensitive ele ments is interrupted with respect to the norA mally scanned color while output signals repre sentative oi' the other two color components is derived during periods when the scanning instantly contacts undesired color areas, means to utilize the instantaneous useful output of the said sensitive elements to accelerate or decelerate the transverse deiection of the scanning beam in accordance with departures thereof from the color Strip instantaneously intended to be scanned so as to restore the instaneous line deflection path of the scanning beam to the desired color strip area, and means cyclically to switch the useful output so that the said light sensitive elements progressively produce outputs measured by the light values of colors other than the one instan" taneously desired to be scanned.

10. In a tricolor television system wherein additive color images are produced with the three component colors of the additive system being sequentially and cyclically produced in a line-for line manner on a target element of a cathode ray tube, said target being formed in a repeating see ries of strip elements where each series includes at least one strip area producing light, under the influence of a modulated electron scanning beam in each selected component color and in which the signal modulated scanning beam is appropriately deflected relatively rapidly along linear paths lengthwise of each of the several color strips in sequence and is also deflected relatively slowly transversely to the strip lengths so as to pass progressively from one color scanning to another, the combination comprising a. plurality of light sensitivity elements of a number corresponding to the number of component color strips in each series of the target ares, to receive light resulting upon electron beam impact on the target, filter means positioned in the light path from the target area to the light sensitive elements to control the impacting light color so that each element produces output currents measured by one light color only, commutating means to cyclically and sequentially render the output signals from one of the light sensitive elements ineffective in an output circuit while connecting the output of the other two into a load utilization circuit, and means to utilize the instantaneous useful output of the said light sensitive elements to accelerate or decelerate the transverse deflection of the scanning beam in accordance with departures thereof from the color strip instanten neously intended to be scanned so as to retain the instantaneous line deflection path of the scanning beam on a desired color strip 11. VIn a tricolor television system wherein ditive color images are produced with the three component colors of the additive system being sequentially and cyclically developed in a linefor-line manner on a target element of a cathode ray image viewing tube, said target being formed in a repeating series of strip elements where each series includes a plurality of strips with at least one strip area for producing light under electron beam activation in each selected component color, and wherein means are provided to develop and signal modulate an electron scanning beam which is appropriately deflected relatively rapidly along substantially linear paths lengthwise of each of the several color strips in sequence and is also deflected relatively slowly in a direction transverse to the strip lengths so as to pass progressively from one color scanning to another, the combination comprising a plurality of light sensitivity elements of a number corre sponding to a multiple of the number of component color strips in each series of the target area to receive light resulting upon electron beam impact on .the target, means to produce output currents measured by one light color only from each of the light sensitive elements, means to render the output signals from the light sensitive elements receiving light of a color instantaneously intended to be scanned ineffective in an output circuit while the output of the other light sensitive elements receiving the other color lights is useful in the output circuit, means to utilize the instantaneous useful output of the said light sensitive elements to accelerate or decelerate the transverse deflection of the scanning beam in accordance with directions of departures thereof from the color strip instantaneously intended to be scanned so as to restore the instantaneous line deflection path of the scanning beam on a desired color strip area.

lil. he combination derived in claim 1l wherein the means to render the output signale from the light, sensitive elements ineffective and useful comprises electronic commutating means to switch .to the load circuit the signal outputs from light sensitive elements receiving light in colors remote from the desired color to instantly be produced by the scanning beam and to render instantly ineffective outputs from light sensitive elements representative of the color light instantly to be produced.

13. The system claimed in claim 9 wherein the said filter means comprises a pair of disk elements to reveal light to the said light sensitive element in the two colors of light normally intended to be external to the scanning beam path.

14. In la television system including a cathode ray tube having a target area formed from a repeating series of light producing elongated strip areas so arranged that each series includes a plurality of strips adapted individually to produce light under an electron beam impact in one of a plurality of selected component colors and so positioned that all selected component color lights are produced by the stripsI or" each series and also including a, line deflection system to deflect the electron beam lengthwise of the strips to scan the several strips in a linefcr-line manner to produce light of a color corresponding to the component color strip instantaneously impacted and a field deflection system to deflect the electron beam relatively slowly, as compared to the line deflection rate, along a path substantially normal to the strip length to cause the scanning progresu sively and cyclically Ito change from one to another of the component colors of the strips, the combination comprising a plurality of light sen ments to the eld deflection circuit either to 10 26 accelerate or to decelerate .the deflection of the cathode ray beam during periods when output currents are developed from the light sensitive elements so that a. restoration of the scanning beam registry on the color strip area instantaneously intended to produce light in a selected component color is substantially instantaneously brought about.

VLADIMIR. K. ZWORYKIN.

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