US2685047A - Color television electron beam deflection control system - Google Patents

Description

2 She'ets-Sheet 1 D. G. MOORE July 27, 1954 COLOR TELEVISION ELEOTRON BEAM OEELEOTION CONTROL SYSTEM Filed Feb. 25, 195o July 27, 1954 D. G.'MooRE 2,685,047

coLoR TELEVISION ELEcTRoN BEAM DEELEcTIoN CONTROL SYSTEM :filed Feb. 25, 195o 2 sheets-sheet 2 Patented July 27, 195.4

UNITED STATES PATENT GFFICE COLGR TELEVISION ELECTRON BEAM DEFLECTIUN CNTROL SYSTEM Donald G. Moore, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware 14 Claims.

This invention relates generally to color television systems of the type using a single color kinescope for the production of images substantially in their natural colors. The invention relates particularly to improvements for effecting registration of an electron scanning beam and the individual phosphor areas of a color kinescope I" the type referred to.

Color television images may be reproduced by a kinescope having' discrete phosphor areas capable respectively of producing light of the different component image colors. One type of tube with which the present invention is particularly adapted for use forms the subject matter of a copending application of Donald S. Bond, Serial No. 145,282, led February 25, 1950 and entitled Electron Beam Tubes. This tube is provided with a screen having separate light-producing and signal-generating regions. The light-producing region consists of a plurality of phosphor lines or strips capable respectively of emitting light of the diierent component image colors. The phosphor strips are arranged in groups which, in a three-color television system, comprise three strips. Where the image is to be reproduced in red, green and blue colors, for example, each group of phosphor strips includes strips capable respectively of emitting red, green and blue light. In the Bond tube the phosphor strips are arranged horizontally and substantially para lel with one another. The phosphor strips of each of the successive horizontally-arranged groups of strips are selectively excited by an electron beam.

In order to selectively excite the phosphor strips for the production ci the desired colors, it is necessary that substantially precise registration be effected between the electron beam and the phosphor strips. Snc manner in which the necessary registration of the beam and the phosphor strips may be effected forms part of the subject matter of a copending application of Donald S. Bond and Donald G. Moore, Serial No. 146,283, led February 25, 1950, now Patent No. 2,634,325 granted April 7, 1953 and entitled Electron Beam-Controlling Systems.

t is an object of the present invention to effect registration between an electron exciting beam and successive groups of phosphor strips in a kinescope o the type described in an improved and more efficient manner.

Another object of the invention is to eect registration between an electron scanning beam and successive groups of color phosphor strips by correcting the position of the beam only to the degree necessary to compensate for changes between the scansion of successive horizontal lines of the image-producing region of the luminescent kinescope screen.

In accordance with this invention, signals representative of any misregistration between the electron beam and a group of color phosphor lines are` generated in a marginal region adjacent to the luminescent screen. The signals are used to develop a correcting signal for impression upon an auxiliary electron beam-delecting system. The auxiliary deecting system functions to correctly position the beam in precise register with the group of phosphor strips prior to its deection over the strips. Inasmuch as the signals derived from the signal-generating region of the kinescope screen are of relatively short time duration, the developed correcting signal is impressed upon the auxiliary deflecting apparatus through a clamping circuit which functions to maintain the necessary beam deflection correction for the duration of the traversal time of the beam over the color phosphor strips. The correcting information is eiectively stored in the clamping circuit so that, during the next traversal of the signal-generating region of the kinesoope screen, the generated registration signals represent only incremental misregistration oi. the beam with the succeeding group ci phosphor strips, The stored correcting information is impressed upon a memory circuit so that it may be combined with the incremental misregistration information to produce a new correcting signal for impression upon the auxiliary deflecting apparatus. By means of such an arrangement, the new correcting information differs from the old by an amount equal to the incremental misregistration information derived from the signalgenerating region of the kinescope screen.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation as well as additional objects and advantages thereof will best be understood from the following description taken in connection with the accompanying drawings.

In the drawings,

Figure 1 is a block circuit diagram of a color television signal-receiving and image-reproducing system embodying the registration apparatuse of the present invention;

Figure 2 is a series of curves illustrating the time relationship of the operation of different parts of the improved registration system;

Figure 3 is a block circuit diagram showing the essential components of any one of the pulse generators employed in the improved registration system; and,

Figure 4 is a schematic circuit diagram of a representative memory circuit used in. the irnproved registration system.

Referring rst to Figure l of the drawings, color television signals are intercepted by an antenna i i which is coupled to a composite television signal receiver i2 for the impression of the intercepted signals thereon. It will be understood that the receiver i2 may include such conventional apparatus as a radio frequency ampliner, a frequency converter, an intermediate freqency amplifier and a second or signal detector. A composite television signal is derived from the receiver l2 consisting of a video signal component and the horizontal and vertical synchronizing signal component.

The video signal component of the composite television signal is impressed upon a video signal channel i3. The synchronizing signal component oi the composite television signal is impressed upcn a synchronizing signal channel Ui. It will be understood that the video and synchronizing signal channels may be conventional. Accordingly, the video signal channel may include one or more stages of video signal amplification and direct current re-insertion circuits to intensity modulate an electron scanning beam. Similarly, the synchronizing signal channel may include deiiection voltage generators for control by the synchronizing signals to energize the beam deflection apparatus.

The image-reproducing system also includes a color kinesccpe it, preferably of the type covered by the copending Bond application refered to. It is provided With a target screen comprising a luminescent, light-producing region I6 and a registration signal-generating region located in a vertical marginal area. rEhe signal-generating region of the screen comprises two vertical groups or columns il and i8 of secondary electron emissive targets such as 23 and 2li. The luminescent screen is is formed of a multiplicity of substantially horizontal, parallel phosphor strips arranged in groups of three, for a threecolor television system, for reproducing an image in red, green and blue color components. One group of such phosphor strips consists of red, green and blue strips 25, 23 and 21 respectively. The signal-generating targets of the group i8 including the target 213 are aligned with the red phosphor strips such as 25. Similarly, the sig- 'nal-generating targets of the group E? such as the target 23 are aligned with the blue phosphor strips such as 2i. The kinescope also is provided With a secondary electron collector 28 located adjacent to the signal-generating target region.

The kinescope further is provided with a conventional electron gun 23 by which to develop an electron beam for impingement of the target screen. An electromagnetic deflection system including a yoke 3i is provided to deflect the electron beam over the target screen to form the usual television raster. In addition, the kinescope is provided With a pair of auxiliary deflecting plates 32 which, when energized, eiect relatively small verticai deections of the electron beam.

The secondary electron collector 28 is coupled to a registration signal amplifier 33 for the impression thereon of signal effects produced by the secondary electron emission from the registration signal-generating targets such as 23 and 24. It Will be observed that, by reason of the fact that the target groups i? and i3 are located in two vertical columns, the secondary electron emission from the blue targets such as 23 Will precede in time the secondary electron emission from the red targets such as 24. Accordingly, the signal eiects derived from the collector 28 consist of time-spaced pulses representing the secondary electron emission from the respective columns of targets.

Such a signal wave is amplified by the registration signal arnplier 33 and impressed concurrently upon blue and red gating devices 3d and 35, respectively. Both or" these devices normally are inoperative so that there is no transfer of energy to their respective output circuits. In order to selectively render the gating devices 34 and 35 operative, there are provided blue and red gating pulse generators 33 3i, respectively. The pulses produced by these devices are generated under the control of the horizontal synchronizing signals derived from the synchronizing signal channel I4. The blue and red gating pulses derived respectively from the generators and Si are impressed upon the blue and red gating devices 34 and 35, respectively, to control the gating of the registration signals.

rihe blue gating device is coupled to a delay device 3S which functions to delay the blue gated registration signal pulses sufficiently to effect coincidence thereof with the red gated registration signal pulses. The red gating device 35 is coupled to a phase inverter 33 which serves to reverse the polarity of the red gated registration signal pulses relative to the blue gated registration signal pulses. The output circuits of the delay device 3S and the phase inverter 39 are connected as shown so as to combine the delayed blue pulse with the phase inverted red pulse. In this manner, there is produced a correcting signal having polarity and magnitude representative of the sense and magnitude of the deviation of the electron beam from precise registration with the group of phosphor strips of the kinescope luminescent screen I6.

The delay device 38 and the phase inverter 39 are coupled to an oscillation preventing delay device li which, in turn, is coupled to a clamping circuit i2 for the impression upon this circuit of the correcting signal. The operation of the clamping circuit is controlled by a clamping pulse received from a delay device i3 connected between the red gating pulse generator and the clamping circuit as shown. Thus, the signal and clamping pulse are applied concurrently to the clamping circuit. A low impedance clamping circuit enables the omission of both delay devices. The output of the clamping circuit is coupled to the auxiliary deflecting plates 32 for the impression thereon of a voltage having a polarity and magnitude sufficient tc effect the desired correction of the electron beam position relative to the group of phosphor screen strips.

To operate the system continuously for successive horizontal groups of phosphor strips, a memory circuit iii is provided. The correcting signal information which it is desired to store in the memory circuit between successive horizontal lines of the image is derived from the delay device @l as shown by a connection 55. rIhe correcting signal is released from the memory circuit later and combined with additional information derived from the blue gating device 34 by means of a connection d6. The storing and releasing operations of the memory circuit are controlled by a pulse impressed thereon by a connection il to the delay device 43 and by anvof the blue registration signal other pulse impressed thereon by a connection i8 to the blue gating pulse generator 36.

lhere also is provided a color deflection generator 59, the output of which is coupled to the deflecting plates 32. The function of this generator is to develop a stair-step voltage wave 58 having three different amplitude levels so as to effect a corresponding deflection of the electron beam for color-selecting purposes.

A :so-called white pulse generator 5l, operating under the control oi horizontal synchronizing pulses derived from the synchronizing signal channel lll, produces pulses which are impressed upon the video signal channel i3 and upon the color deflection generator 4u. The impulses derived from the generator 5l when impressed upon the video signal channel I3, serve to control the intensity of the electron beam developed by the gun 2t in a manner to produce maximum intensity thereof during the time that the beam is traversing the marginal signal-generating target region of the kinescope screen. Also, during this time the impression of these pulses upon the color deflection generator 49 serves to render it inoperative so that there is no corresponding deflection of the electron beam during its time of traversal or' tne signal-generating screen region.

in View ol the foregoing description of the ima-ge reproducing system embodying the present invention, its operation may be completely understood with the following additional explanation. rrhis portion of the description will be given with additional reference to the curves of Figure 2. f hese curves represent the timing ol' the appaiatus during the period in which the electron beam traverses the signal-generating screen region inciuding the two columns of target electrodes il and l. It will be understood that this traversal occurs during the later stages of' the horizontal blanking periods. In Figure 2 the curve 52 represents the horizontal blanking period. The curve 53 represents a horizontal synchronizing pulse. rhe curve 5d represents a white pulse under the control of which the intensity of the electron beam is increased to maximum or other' predetermined value. Consequently, the electron beam, in traversing a representative horizontal line of the kinescope screen, is indicated by the dashed line 55 of Figure l. It will be assumed that, in traversing the signalgenerating region, the beam is out of register with the green phosphor strip 2t in the direction of' the red phosphor strip 25. Consequently, in traversing the signal-generating region, there will be emitted a greater number of secondary electrons from the red target 2&3 than from the blue target 23. The registration signal wave derived from the collector 28 is represented by the curve 595 of Figure 2. It will be seen that the amplitude indicated at 5l is somewhat less than the amplitude indicated at 53. These signals correspond respectively to the secondary electron emission from the blue and red targets 23 and 2t.

It is this type of registration signal wave 56 which is impressed upon the blue and red gating devices te and 35, respectively, by the registration signal amplifier 33. In Figure 2, the curve 5s represents the time of occurrence of one of the blue gating pulses by which to effect operation of the blue gating device 3d. It may be seen that these events coincide with the occurrence Likewise, the curve El represents a red gating pulse to render the red gating device 35 operative in coincidence with the occurrence of the red registration signal 58.

After delaying the blue registration signal and inverting the phase of the red registration signal, there is produced by their combination a correcting signal for impression upon the deflecting plates 32. The polarity of this signal, as impressed upon the deilecting plates, is of a character to effect a downward deflection of the electron beam. 'The magnitude of the correcting signal Voltage impressed upon the plates 32 is suitable to control the amount of downward denection so that the beam is brought into register with the green phosphor strip 2e,

It will be appreciated that the present invention may be used advantageously in eld and line sequential color television systems. Additionally, the operation of the type of tube diagrammatically illustrated herein and forming the subject matter of the copending Bond application referred to may be used to particular advantage in a color television system operating according to the dot or elemental multiplex principle. In a television system of this latter character, the color information of each elemental area of the image is represented by successive instantaneous amplitudes of a Video signal wave. Accordingly, when such a video signal wave is used to control the intensity of an electron beam, a tube of the character described may be operated so that each of the component colors of the different elemental areas of each horizontal line of the image is produced during a single horizontal deflection of the electron beam. In the present system, the entire video signal wave may be used to control the electron beam intensity. Alternatively, if desired, the wave may be sampled to derive only the successive instantaneous amplitudes thereof. In this case, the signal samples are used to modulate the beam intensity.

A system operating in accordance With 'the elemental multiplex prnciple is covered in a copending application of John Evans, .Serial No. 111,384, filed August 20, 1949 and tilted Color Television. Accordingly, it will be understood that the video signal channel i3 may include suitable sampling apparatus to derive from such a video signal wave the necessary color information to operate a tube of the type described. One such sampling system is disclosed in the copending Evans application referred to. Another suitable sampling system forms the subject matter of a copending application of George C. Sziltlai, Serial No. 145,421), rlled February 21, i950 and titled Color rirelevision Receiving Systems.

It will be understood, therefore, that while the electron beam is being deflected to form one horizontal line of the image, it is modulated in intensity at successive instants in accordance with the different color components of the elemental areas of the image line. The intensity modulation of the electron beam is used to excite the appropriate phosphor strips under the control of a color-selecting deflection produced by the deflecting plates 32. A stair-step wave 50 derived from the color deflection generator i9 impresses suitable voltages upon the deilecting plates S2. As indicated by the dashed line in the light-producing region of the luminescent screen l, the electron beam is deflected vertically to impinge successively upon the different phosphor strips 25, 2c and 2l. It will be understood that, during the times that the beam is in register with the red strip 25, its intensity is controlled by a red representative video signal. A similar relationship exists for the green and blue strips 26 and 2l.

During the blanking period between the scansion of successive horizontal lines of the screen i6 the electron beam is caused to traverse the signal-generating marginal region including the target groups il and i8. During each traversal of the target region the corrective deection oi the beam given to it in the preceding line is effective to control its position during this excursion. Accordingly, by the operation of the clamping circuit 4?., in conjunction with the memory circuit lidi, there is produced a new correcting voltage for impression upon the plates E2 which represents a combination .of the old correcting voltage and any incremental correcting voltage necessary .to eiect the desired precise registration.

Reference now Will be made to Figure 3 for a disclosure of one of the gate pulse generators shown diagrammatically in Figure 1. For purposes of illustration, the blue gate pulse generator 35 will be described, it being .understood that the red gate pulse and White pulse generators 3l and 55, respectively, may be substantially identical. The blue pulse generator 3S includes an input amplifier 5'2. This may be an entirely conventional device capable of amplifying pulses such as a horizontal synchronizing pulse t3. rlhe amplier 62 is coupled by means of an isolation stage which may consist of a diode @il to the control circuit of a pulse timing multivibrator t5. It will be noted that the pulse 56, derived from the diode Gel, is similar to the horizontal synchronizing pulse S3 except that it is of reverse polarity. Also, it will be noted that the pulses 53 and se occur between times T2 and Ts indicated on the time scale of Figure 2 and corresponding with the time oi occurrence oi the horizontal synchronizing pulse 53.

The pulse timing multivibrator 95 is a monostable multivibrator which has the characteristic of having one stable and one unstable state. it normally is in its stable state and may be triggered'for operation to its unstable state. The time during which it remains in its unstable state is dependent upon its .circuit constants. en illustrative form of multivibrator is shown in the book entitled Time Bases by Puclle, published in New York by John Vliley and Sons inc. and in London by Chapman and Hall Ltd. Monostable multivibrators suitable for use in the present apparatus are shown in Figs. 27 .and 28 of the reference appearing respectively at pa es 50 and 5l.

1t will be understood that the pulse timing multivibrator 5s is triggeredfrom its normal stable state to its unstable stateat time T2 in response to the pulse Accordingly, there developed in the output of the multivibrator 55 a pulse having substantially the form shown atti'. It will be noted tL at the pulse'! extends from time to time T5. rhe purpose of the `multivibrator is to time the generation of the blue gating pulses with reference to the horizontal synchronizing pulses. in this connection it will be noted that is that-coinciding with the leadiwT edge of the blue gating pulse 59 of 1Eigure 2.

The pulse Si is impressed upon a clipper by which it is made substantially rectangular as indicated at The clipper also functions to invert the polarity of the pulself'l.

The pulsets is impressed Vupon a..dierentiat ins :nett/,cirka il Ywhich iunciions @produce Slaan negative ,and positive pulses 'l2 and respec-l tively, occurring at times r2 and T5 respectively.

The Ypulses l2 and 'i3 ,are `impressed upon another clipper ii which is responsive only to pulses of positive polarity, such as the pulse T3. The output of the clipper 'it is coupled through an isolation stage such as a diode 'l5 to the control circuit of a pulse length multivibrator l. It will be noted that there is impressed upon the multivibrator l5 a pulse "il of negative polarity occurring at time T57. The pulse 'il is produced by the operation of the clipper 'i4 in response to the pulse 'it impressed thereon.

The pulse length multivibrator 'is preferably is a monostable multivibrator of substantially the same type las the ip uljtivibra tor E5. The function of the multivibrairfi is to ontrolthe length or time duration o'. @ne blue gating pulse. Azccordingly, its circuit .constants are adjusted to uce a pulse is extending from times :Q5 -to T e. This, it will be observed, vcOrresponds to the width r time duration of the blue gating pulse l59 of Figure 2.

The pulse is impressed upon another clipper i9 by which an inverted and 4clipped pulse Si is produced. This pulse is amplified ,and inverted in polarity an output amplifier B2, to produce a pulse 83. This pulse may be seen to correspond to the blue gating pulse 59 `of Figure 2.

lin View or" the foregoing description of the blue gating pulse generator 3 5, it will not be necessary to describe Ythe lred and White pulse generators and hrespectively. Each of these generators will be understood to include pulse timing and pulse .length multivibrators of the monostable type. The respective pulse timing multivibrators have circuitcconstants suitable to control the timeof occurrence of the ,leading edges or" the pulses to be developed with reference to the horizontal synchronizing pulses. Similarly, :the pulse `length multivibrators are provided with circuit .constants suitable t0 .90ntrol the length or .time durations of ,theAgenerated pulses.

rEhe circuit details of the memorycircuitl of Figure lare illustrated iniFigure 4 of thedrawings. In general, the memory.circuitconsists of two major components. One is a clamping circuit by which to ystore the correcting signal information from onehorizontal image lineto another. he other main componentof` the rnerrupryv circuit is a gating device bywhich to transferthe kstored correcting signal information to the delay device oi Figure l for lcornbination withthfezincremental correcting signal information ,nGWls/,derived from the bluegatinsdeyice A3s.

The clamping circuit preferably is of a type similar to ,thatusedior the` clampingcircuit 42 of Figure lys/'nich` is covered Vby Patent 2,299,945, granted .October,27, ,1942 to R. Wendt and titled DirectCurrentReinserting Circuit. The memory circuit clamping apparatus is a lowvoltage device relativetothehigh voltage clamping circuit t2. vrIt Vcomprises twohdiodes Sil and having the cathode oi the former coupledto the anode of the lattergthrOugh two equal resistors t5 and 8l. The otheridiode electrodes are directly connected together as shown. The junction point of resistorstii and 8l is ccnnectedto ground'through a source of negative biasing Voltage represented bye battery S3. The clamping circuit also islprovided With a keying `tube 89. The cathode ortho tube 89 isconnectedtoground the delay device lil.

through a load resistor 9|. The anode of the tube 99 is connected to a source of space current, indicated at +B, through a second load resistor 92. Preferably, the resistors 9i and 92 are equal in value. The anode of the keying tube 99 is coupled to the anode of the diode S by a capacitor 93. Similarly, the cathode of the tube 99 is coupled by a capacitor 94 to the cathode of the diode 8A.

The clamping circuit described is provided with the correcting signal information which it is desired to retain by a coupling including a capaciitor 95 to the delay device 4i of Figure 1. The clamping circuit is operatively controlled by a signal derived from the delay device 3 oi Figure 1. The control signal is impressed upon the clamping circuit through a phase inverter 96 by which the pulse of positive polarity derived from the delay device 43 is converted to a pulse of negative polarity. This pulse is impressed upon the control grid of the keying tube 89 by a capacitor 91 for which there is provided a leak resistor 98.

Normally the keying tube 89 is in a conducting state. In response to the impression of a negative control impulse upon the grid thereof, it is biased to a point beyond cut oli. Accordingly,

there is developed, at the anode of the keying tube, a positive pulse 99 which is impressed by the 'capacitor 99 upon the anode of the diode B5.

Similarly, a negative pulse lill, derived from the cathode of the keying tube, is impressed upon the cathode of the diode 34. By this means the diodes 84 and S5 are rendered conducting to alter the charge on the capacitor 95 in accordance with the correcting signal information derived from Following the occurrence of the pulses 99 and im, the diodes M and 85 are rendered non-conducting, thereby storing the correcting signal information derived from the delay device il in the capacitor 95.

The memory circuit of Figure 4 also includes apparatus for transferring the correcting signal information stored in the capacitor 95 to the delay device 39 of Figure 1. This apparatus generally may be characterized as a gating device. It consists of a gating electron tube HD2, a polar izing electron tube E93, and a pulse-combining electron tube iM.

The gating tube 592 preferably is a multi-grid tube and for one particular system which has been successfully operated it is a pentode. The control, or number one, grid its of the gating tube is connected directly to the storage capacitor 95 of the clamping circuit. The screen, or number two, grid 95 of the gating tube is connected to a source of positive potential indicated at +B through a resistor E97, The screen grid lll also is by-passed to ground by a capacitor i518 which is shunted by a resistor E99. The suppressor, or number three, grid iii of the gating tube has impressed thereon a negative potential derived from a suitable source such as indicated by the battery i i2. The cathode of the gating tube E92 is grounded and the anode is connected to the positive terminal of a source oi space current, indicated at +B, through resistors it? and H3.

Normally, by reason of the impression of the negative potential upon the suppressor grid iii, the gating tube E92 is biased beyond cut-off eo that it is non-conductive, irrespective of the stored signal energy impressed upon the control grid H85 thereof. The gating tube is rendered conductive periodically by means of pulses derived from the blue gate pulse generator 3S of Figure 1. As indicated in Figure 4, the conductor 48, extending from the pulse generator 36, is terminated by the grounded resistive element of a potentiometer i ill. rlihe movable contact element of the potentiometer iii is coupled by a capacitor iii/l to the suppressor grid HI of the gating tube H92.

The potentiometer Ml also is shunted by a series connection of a capacitor lit and the resistive element of another potentiometer H1. rEhe movable contact element of the potentiometer ill is directly connected to the control grid or" the polarizing tube it. The anode of this tube preferably is directly connected to the positive terminal of a source of space current indicated at +B. The cathode of the polarizing tube is connected to ground through a load resistor H8.

The cathode of the polarizing tube iii and the anode of the gating tube HG2 are coupled by capacitors H9 and il, respectively, to the control grid of the pulse-combining tube IM. A leak resistor E22 is provided for the coupling oapacitors H9 and ii. The cathode oi the pulse combining tube is connected to ground by a selfbiasing network including a resistor E23 and a by-pass capacitor E24. The anode of the pulsecombining tube is connected to the positive terminal of a source of space current indicated at +B through a load resistor $25. The anode of the pulse-combining tube i9@ also is coupled by a capacitor 526 to the delay device Se by Way of conductor Lit.

In describing the operation of the memory circuit of Figure 4, it will be understood that the keyed clamping circuit, including diodes td and S5, functions in the manner described to store in the capacitor correcting signal information of either positive or negative polarity relative to ground. In viev7 of the described negative biasing of the suppressor grid iii of the gating tube 92, no current is conducted in this tube until one of the blue gate pulses such as 59 of Figure 2 occurs. The impression of a blue gate pulse in positive polarity upon the suppressor grid l ii of the gating tube overcomes the negative biasing of this electrode to render the tube conducting. The degree to which the tube is rendered conducting, neglecting for the moment the effect of the control grid leb, is determined by the setting of the potentiometer lili. This adjustment should be so that there is developed at the anode of the gating tube 92 a pedestal pulse having an amplitude ci a value between the extremes of non-conduction and maximum or saturated conduction in the tube. Accordingly, when additionally considering the concomitant eiiect of the correcting signal energy stored in the capacitor 95 upon the conductivity of the gating tube it?, it will be seen that its conduction of space current is either greater or less than the pedestal pulse value depending upon Whether the stored correcting signal energy impressed upon the contr-ol grid 95 is of positive or negative polarity relative to ground. Thus, it is seen that it is possible to identify the polarity of the stored correcting signal energy in the anode circuit of the gating tube E92 on the basis oi the amplitudes of the pulses developed therein with respect to the described pedestal pulse.

The blue gate pulse derived from the generator 3% also is impressed in positive polarity upon the control grid of the polarizing tube iet. Accordingly, it will be seen that there is developed at the cathode of this tube a pulse having a polarity relative to ground which is opposite to the polarity of the pedestal pulse developed at the anode of the gating tube 402. By proper adjustment of the potentiometer IH, the pulse developed at the cathode of the polarizing tube 103 may be made to neutralize or completely cancel out the pedestal pulse.

Hence, it may be seen that there is impressed upon the control grid of the pulse-combining tube les pulses of either positive or negative polarity relative to ground in accordance with the polarity of the correcting signal energy stored in the capacitor 95 of the clamping circuit component of the memory circuit 44. Accordingly, by coupling the outputcircuit of the pulse-combining tube ll to the delay device 38 of Figure l in the manner described, there is impressed upon this delay device a pulse representing the correcting signal for the preceding line of the kinescope screen scanned by the electron beam. It also will be noted that this information is transferred to the delay device 38 concurrently with the additional transfer to this device of the blue registration signal derived from the blue gating device S of Figure l and representing any incremental correcting signal indicative of any additional deviation of the electron beam, in traversing the signal-generating target area of the screen, from precise registration with the next succeeding group of phosphor strips to be scanned. It will be appreciated that the described impression of the correcting signal information upon the delay device 38 of Figure l concurrently from the memory circuit lit and from the blue gating device 34 is achieved by operating both the memory circuit and the blue gating device by the same blue gating pulse derived from the generator 36. Y

The new correcting signal produced in the manner described is impressed upon the delay device 4l of Figure l and subsequently upon the clamping circuit 2. Substantially concurrently with the impression of the new correcting signal information upon the clamping circuit 42 a clamping pulse derived from the red gating pulse generator 3? through the delay device 3 is impressed upon the clamping circuit G2 to store the new correcting signal energy therein. At the same time this clamping pulse is impressed by conductor Il? upon the memory circuit M to store the new correcting signal information in the clamping circuit thereof. In this manner the new correcting signal information is available for transfer in the manner described for the production of a correcting signal for the following line of the image to be reproduced.

It will be seen that the present invention provides a system by which to control the deflection of an electron beam so that it may be brought into precise register with the light-producing strips of a kinescope of the type disclosed in the copending Bond application referred to. inasmuch as the beam deflection control system enibodies a memory circuit by which the correcting signal information of one beam deection over the kinescope screen may be used to contribute to the development of a correcting signal for a succeeding beam deflection, it is necessary only to develop registration signals representative of any required additional line-to-line corrective deflection of the beam. Such an arrangement provides an improved control system which is capable of operating in a highly efcient manner.

It is advantageous in a color television receiver,

particularly of the typedescribed, insuring ter color-selection. Obviously the system may be used beneficially to control beam deflection in camera tubes, such as the well known iconoscop'e, orthicon and image-orthicon, for example. By such use more accurate video signals may be 'gen'- erated. it will be apparent that the deflection control system of this invention may be used to advantage also in black and White television systems; in fact, 'whenever it is necessary to maintain accurate registration of an electron beam and a target electrode scanned thereby. u Y

The inclusion of a memory circuit in a control system of this character 'enables accurate Acontrol of raster size and position on the `kinescbp'e screen. This benecial result is produced requiring a correction between successive lines which is representative only of ,the line-toline deviation or the scanning deflection system, which ordinarily is small. v ,Y r Furthermore, in accordance with one 'of features of this invention, there is rovided a memory circuit or" a type capable for transferring from an input circuit to an output circuit signal effects of 4either positive or negative polar? ity. Additionally, as one of the components of the memory circuit, an improved type of gating device is provided. Ey reason o f the descried biasing and operative control of a multi-grid electron tube, it is seen that signals may be produced in the output circuit of the tube of dierent amplitudes representative respectively not only of the amplitudes of the signals iinpressed upon the input circuit of the tube, but also of the polarity of the input signals. m'lhus, by the additional use o a means for combining Ineutralizing signals with such output signals,

there may be derived signals of either polarity corresponding to thepo'la'rity of the input signals.

The nature of the invention may be ascertained from the foregoing disclosure of an illustrative embodiment thereof. The scope or the invention is set forth in the appended claims.

l. An electron beam deflection control system for a color television receiver embodying 'a kineseope having a luminescent screen including a multiplicity of groups of lsubstantially horizontal strips of material capable respectively of pro'- ducing light of the different component colors of an image to be reproduced in response to excitation by an electron beam deflected 'over said screen, said kinescope also having'electro'dc structure adjacent to one edge of said screen to generate registration signals responsive to trav]- ersal thereof by said beam and representative of the orientation of said beam with successive groups of said screen strips, said control system comprising, beam-deiiecting means adjacent to said electron beam path and'energizable to elfe-ct registration of said beam with successive groups of said screen strips, means for developing correcting signals from said registration signals, means for energizing said beam-deecting'means by said correcting signals, means for storing said correcting signals respectively during successive horizontal deflections of said beam over said screen, and means to combine said stored correcting signal for each horizontal beam deecion to develop a correcting signal for said next horizontal beam deflection.

2. An electron beam deilection' control system as defined in claim l, wherein said beam-deflecting energizingmeans includes a clamping circuit.

fin electronV deflection controlsystem as deiined in claim 2, including additionally means for keying said clamping circuit subsequently to the generation of said registration signals.

4. An electron beam deflection control system as dened in claim 1, wherein said correcting signal-storing means includes a clamping circuit.

5. An electron beam deflection control system as deiined in claim 4, including additionally a gating device coupled to said clamping circuit and operative to transfer said stored correcting signals to said correcting signal developing means.

6. An electron beam deection control system as defined in claim 5, including additionally means for operating said gating device concurrently with the generation of said registration signals, and means for keying said clamping device subsequently to the generation of said registration signals.

7. An electron beam deflection control system for use in a color television system embodying a kinescope having a luminescent screen including a multiplicity of groups of substantially horizontal strips of material capable respectively of producing light of the diierent component colors of an image to be reproduced in response to excitation of an electron beam deflected over said screen, said kinescope also having electrode structure adjacent to one edge of said screen to develop registration signals responsive to traversal thereof by said beam and representative of the orientation of said beam with successive groups of said screen strips, said control system comprising, a pair or" beam deflecting plates in said kinescope energizable to effect registration of said beam with successive groups of said screen strips, means for developing correcting signals from said registration signals, means including a clamping circuit for impressing said correcting signals upon said deflecting plates means including a memory circuit for storing said correcting signals respectively during successive horizontal deflections of said beam over said luminescent screen, a gating device in said memory circuit operative to release said correcting signals stored in said memory circuit, means to periodically operate said gating device immediately preceding the development of said correcting signals, and means to combine said released correcting signals for each horizontal beam deiiection with generated registration signals for the next horizontal beam deection to develop a correcting signal for said next horizontal beam deflection.

8. Apparatus for the selective transfer of signals or either positive or negative polarity from an input circuit to an output circuit, said apparatus comprising, a normally inoperative electron gating tube having an input electrode coupled to said input circuit for the substantially continuous impression thereon of signals of either positive or negative polarity, an output electrode and a control electrode for said gating tube, means including a source of gating pulses coupled to said control electrode to periodically operate said gating tube to develop at said output electrode pulses of greater or less than a predetermined pedestal pulse magnitude depending upon the polarity of the signals impressed upon said input electrode, and means including a source of polarizing pulses having a polarity opposite to that of said pedestal pulses coupled to said output electrode to neutralize said pedestal pulses, thereby to produce for impression upon said output circuit positive and negative pulses corre- 14 sponding respectively to the positive and negative signals derived from said input circuit.

9. Apparatus of the type defined in claim 8, wherein said gating tube has a plurality of space current control grids, one of which comprises said input electrode and another of which comprises said control electrode.

10. Apparatus of the type defined in claim 8, wherein said gating tube is a pentode, of which the control or number one grid comprises said input electrode and the suppressor or number three grid comprises said control electrode.

1l. Apparatus of the type dened in claim 8, wherein said control electrode is negatively biased to normally prevent space current conduction in said gating tube, and said gating pulses are of positive polarity to render said gating tube conducting for the production of said pedestal pulses.

12. Apparatus of the type defined in claim 8, wherein said source of polarizing pulses includes an electron polarizing tube having an input electrode coupled to said source of gating pulses and an output electrode coupled to the output electrode of said gating tube.

13. Apparatus of the type defined in claim 12, wherein said pedestal pulse-neutralizing means includes an electron pulse-combining tube having an input electrode coupled to the output electrodes respectively of said gating tube and said polarizing tube, and one output electrode coupled to said output circuit.

14. Apparatus for the selective transfer of signals of either positive or negative polarity from an input circuit to an output circuit, said apparatus comprising, an electron gating tube having an anode and a plurality of space current control grids, one of said grids being coupled to said input circuit for the substantially continuous impression thereon o signals of either positive 01 negative polarity, a source of negative biasing voltage coupled to a second one of said grids to render said gating tube normally non-conducting, means coupled to said second grid and including a source of positive gating pulses of a magnitude to render said gating tube conductive to a predetermined degree to develop at said anode a negative pedestal pulse, said tube conductivity being greater or less than said predetermined degree depending upon the polarity of the signals impressed upon said rst grid, whereby to develop at said anode negative signal pulses of greater or less magnitude than said pedestal pulses, a polarizing electron tube having a control grid and a cathode, the control grid of said polarizing tube being coupled to said source of positive gating pulses to develop at said cathode positive pedestal-neutralizing pulses equal in magnitude to said negative pedestal pulses, and a pulse-combining electron tube having a control grid coupled to the anode and cathode respectively of said gating and polarizing tubes and an anode coupled to said output circuit for the impression thereon of positive and negative pulses corresponding respectively to the positive and negative signals derived from said input circuit.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,415,059 ZWOrykin Jan. 28, 1947 2,418,116 Grieg Apr. 1, 1947 2,490,812 Hoiman Dec. 13, 1949 2,545,957 Kell Mar. 20, 1951 2,616,047 Boothroyd Oct. 28, 1952

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