US2656485A - Memory tube control device - Google Patents

Description

Oct. 20, 1953 c. H. PAGE 2,656,485

MEMORY TUBE CONTROL DEVICE Filed Oct. 8, 1951 2 Sheets-Sheet 1 Fig. l-

75 AMPL/F/EE INVENTOR.

Chester H. P1152 BY XL- ATTORNEYs Oct. 20, 1953 c. H. PAGE MEMORY TUBE CONTROL DEVICE 2 Sheets-Sheet 2 Filed 001:. 8, 1951 FROM SELECTOR CONTROLS SELECTOR DIODES DIODE L ADDE E SELECTOR INPUT SELECTOR INPUT m4 JNVENTOR. Eheater H- P115 2 BY I [1 E] 6LAVE TUBES n4 ATTORNEYS Patented Oct. 20, 1953 was 1 MEMORY TUBE CONTROL DEVICE Chester H. Page, Silver Spring, Md., assignor to the United States of America as represented by the Secretary of the Army Application October 8, 1951, Serial No. 250,377

7 Claims. (Cl. 315-9) (Granted under Title gibU. S. Code (1952),

sec.

The invention described in the specification and claims may be manufactured and used by or for the Government for govermnental purposes without the payment to me of any royalty thereon.

This invention relates to cathode ray tubes of the type known as memory tubes and more particularly to means for controlling the position of an electron beam in such tubes.

A difiiculty encountered in cathode ray tubes is returning the spot formed by the electron beam upon the screen of the tube to a predetermined location on the screen. It is accordingly a primary object of the present invention to develop means for positioning the beam of a cathode ray tube as desired. This difliculty becomes of importance where it is necessary to scan a selected portion of a charged mosaic screen such as may be found in iconoscopes and in some types of memory tubes. A second object of the invention is therefore development of means to position the beam of a cathode ray tube to scan a predetermined part of the screen of the tube. Other objects of the invention will be evident hereinafter.

I have found that a particular type of cathode ray tube in conjunction with a special control circuit will serve to position the spot developed by the electronbeam.This cathode ray tube is constructed with a segmented metallic target for the cathode beam and constructed in segments, each of which is connected to a ladder of diodes grounded at one end. These diodes are held normally nonconducting but are selectively rendered conducting by positive signals fed to the segments. The output of the diodes is supplied to an amplifier. Positioning of the beam in the tube is determined by the output of the amplifier connected to one of a pair of electrostatic deflection plates in the tube and by a positive bias supplied to the other of the same pair of deflection plates from any convenient external source. The construction of the control cathode ray tube and of its circuit will be understood more easily from a consideration of the following description and the appended drawings in which:

Figure 1 is a longitudinal section of the cathode ray tube of the present invention;

Figure 2 shows a view of the target of the cathode ray tube;

Figure 3 is a section along line 3-3 of Figure 2;

Figure 4 is a longitudinal section of another embodiment of the tube of the invention;

Figure 5 is an enlarged view of part of the target showing connections with the diode ladder;

Figure 6 is an enlarged view of part of the target showing selector inputs and some of the selector and ladder diodes in the conducting state;

Figure '7 is a block diagram of the entire control circuit of the tube, the latter being in perspective;

Figure 8 shows the tube of this invention used :tsba master control tube for several slave memory u es;

Figure 9 shows the electron spot of the tube of this invention in position on a vertical segmented target;

, Figure 10 shows the electron spot in position on a horizontal segmented target; and

Figure 11 shows the spot of a slave tube posizicioned horizontally and vertically as by a master The cathode ray tube l9 (Figure 1-4) of this invention consists of an evacuated envelope 20 of ordinary design containing a conventional electron gun 2| with heaters 22, cathode 23, grid 24 and anode 25. An electron beam 26 is emitted by gun 2| and passes through a single pair of electrostatic deflection plates 21 and 28. Connections to the elements of the electron gun may be made through base 29. Electron beam 26 impinges at a spot 30 on a narrow segmented target 3| attached through leads 32 to receptacle 33 and through leads 34 to receptacle 35. The tube as shown has a target 3| with sixteen segments but any desired number may be used. Since it will be necessary to refer to some of the segments of the target separately, they are designated by the numbers 36-5] inclusive although identical physically.

Target 3| is carried by screen 52 and may be formed by depositing a metallic coating in the shape of a long narrow rectangle onto a dielectric surface. The coating is then cut through to the dielectric by straight scratches 53 to form the numbered segments. While the envelope 20 may be of any suitable material, it is essential that screen 52, carrying the target, be a nonconductor and that the segments of the target itself be conductive. If desired the target may be formed on a separate screen 54 (Figure 4) suspended by retainers 55 within the envelope 20. One each of leads 32 and 34 must be electrically connected to a respective segment only and make a separate external contact through conventional receptacles 33 and 35.

Segments 36-51 are connected through leads 32 to receptacle 33 and through the receptacle to a ladder 56 of diodes only four of which 51, 58, 10, and H are shown. (Figures 5 and 6.) As illustrated the upper segment 36 is connected to the plate of diode 51. The-cathode of this diode 51 is joined to the plate of the second diode 58 the 3 cathode of which in turn is connected to the plate of the next lower diode (not shown). Thus the junction between diodes 51 and '58 is connected to the second lower segment 31 of the target. A 4

number of segments and associated circuitry have been omitted from Figures 5 and-6- as indicated by the dotted lines but the connections are made in the same manner down the entire diode ladder.

also be associated with a diode if desired, as will be evident from the description of the operation of" the circuit given hereinafter.

The upper end of the diode ladder 56 is'=connectedithrough line 12 to anam'plifier-Iilas well as'tmuppersegment 36. This amplifieris of any conventional type, as for example a simple triode, soxlongtas sufficient amplification is obtained for a -purpose'to be described. The amplifier furthermore need not be linear. Bias is supplied to the' amplifier 13 through resistor 14. The output of amplifier 13 is .appliedby means of lead 15 to deflection plate 2'! of the cathode ray tube 19. Theother deflection plate 28' is connected through lead 16 (Fig. 7)" to anyconvenient source or positive potential representedby A. Source A may consist of a battery grounded at the negative end or any other steady high voltage.

vIn additionto the connections to the diode ladder 56, each segment of the target has a lead 34- through receptacle 35 -toone' of the bank 94 of selector 'diodeswnlyfive'of which 11, 18, 99. 9 I-an'd B-Zare shown. Each segment is connected directly 'inone to one correspondence with the cathode of respective ones of the selector diodes. Thus segment-35 is connected-to 11, 31 to 18, and s=-0n down through which is connected to diode 92. There is no interconnection between the diodes "of this bank '16. The plates of these =dio'des 11 etc. are joined through individual selector leads-93 to aselector unit (not shown) conventional in the computer art'and forming no part of this invention. -As will be seen the selector acts like a switch-normallyholdingall the diodes in a non-conducting state as by putting a negative voltage on the plates thereof 4 to overcome the positivebias from source'A. The amplified signal; now positive in sign, is-=supplied t0 the second 15 of the single pair of deflection splates in operation to the bias given by A and accordingly drives the cathode beam to the bottom -or grounded segment 5| of the segmented ,target as plate-28 becomes negative with respect to'plate 21. It may be noted that the amplified v asignalscannotdrive-the beam ofi the target comthe beam back "tothe to segment.

or by creating a break in the circuit. When it becomes-desirable toactivateone of the diodes The cathode ray tube l9 operates ina conventional manner. When the cathode is heated and the voltages on the usual controls are adjusted an electron beam is emitted and strikes the con- :ductive target. The positive bias from a source -A applied towone of the singlepair of electroe static deflection plates isisufficient to" deflect the 4 beam to the upper or amplifier connectedsegment. of this target. The cathode beam,.however, being composed of electrons, acts-as a source of negative current. This current as long .as it impinges onany segment ofthe target'supplies a signal to the amplifier where it is amplified and inverted. The ampliflcationof thisi am'plifier is chosen of a size to develop a voltage able pletely. If for some reason the beam did get off the conducting segments the amplifier would no longer receive a negative signal and the positive A bias operating alone would immediately bring With these conditions obtaining enough of the spot formed at the point of impact of the beam on the target will alwaysremain on the target to generate the amplified positioning signal. Essentially the tube is therefore a voltage generating devicew-i tha sequence 'of voltage appearing at the electrostatic plates of the right magnitude to deflect the electron beam to predetermined positions onthe screen.

"To illustrate the function of the selector diodes, reference is made to Figure 6. Assume first that all the selector leads "93are in the normal condition holding the selector diodes non-conducting. In this situation the electrostaticdeflection plates of the cathode ray tube are actuated by the posi- 'tive biassupplied by A-and' the amplified positive signal originated :by the electron beam. As pointedout above the electron beam will come to rest in a position where enough of the signal generated by the electrons can reach the amplifier to form an amplified voltage just-overbal- 'an'cing the A bias. In the figure, segment 5 l"is grounded. If all'of'the' electron 'beam were impinging on segment 5|, onlythe positive bias would be'o-perative onthe deflection plates and the beam' would'be immediately deflected to the top segment in the target, segment 36. Consequently the normal position of the electron beam will be at least touching segment 50, the lowest segment not directly connected to ground.

Assume .now. that the equilibrium of the system is suddenly disturbed by the injection of a positive signal into one 'of the'selector diodes, diode forfexample, by means of its particular input lead" 93.' Diode 90 immediately begins conducting thus driving segment'49, to which it is directly connected, positive. lThe plate of diode 10 in the amplifier diode ladder in turn becomes positive, diode lll begins conducting, drives the plate of .diode H positive and causes diode H to conduct. The cathode of "diode 1| is grounded. Since an electron. stream is now travelling between-segment and ground, segment 49 isalso efiectively grounded. Unless a shift in the position of the electron beam takesv place the situation obtains spoken of previously as impossible, that is, the situation in which the beam is impinging on a part of the target not affecting the amplifier at the same time the positive bias.- is operating on the electrostatic deflection plates. In actual fact however the bias pulls the beam. back on the target immediately and a new equilibrium isset up with the beam touching the lowest segment still not grounded. Withsegment 49 grounded, the lowestsegment-conducting to-the amplifier .is48. Consequently the new position assumed by the electron beam [is one touchingvsegment 48.

;.The sequence of 'events outlined in the immediatelyvpreceding paragraphis repeated whenever an inactive selector diode nearer the top of the bank than one presently active is rendered conductive. Thus if diode 18, connected to segment 31, is activated, segment 31 and all segments lower than 31 in the target are grounded and the cathode beam is immediately shifted to contact with segment 36. If the top diode 11 starts conducting the entire target is grounded and the amplifier has no influence on the position of the cathode ray spot, that is, the cathode beam takes the position determined by the positive bias.

The sequence of activation of segments can be reversed by cutting out selector diodes high in the bank in favor of lower diodes. The amplified cathode beam signal immediately pulls the beam down to the lowest ungrounded segment, the beam assuming the position necessary to generate enough amplified signal to overcome the positive bias. It will thus be observed that a cathode ray beam can be made to take instantaneously any one of a number of predetermined positions within a cathode ray tube merely by indicating the desired position by means of an electronic switch. Actually a simple manual switch could be used to replace the bank of selector diodes, a positive potential being supplied by a battery grounded at the negative end. Such a manual switch would however be entirely too slow for use in computers where rapid calculation is necessary.

A feature of the cathode ray tube as described thus far is utilization of a single pair of deflection plates. A single pair only is needed because positioning of the beam in only one direction, which may be described as either vertical or horizontal, is required. It will be evident to those skilled in the art that both vertical and horizontal positioning can be obtained in one tube by use of the customary two pairs of deflection plates. Such positioning requires 'a separate set of selector and amplifier diodes for each pair of plates. The target for such a tube is a lined mosaic resembling that of Figure 11. Since the tubes will however be normally used as controls and since two tubes with a single pair of plates will perform the duties of the more complicated. tube with two pairs of plates, a detailed discussion of the latter is believed unnecessary.

Figure 8 gives a circuit diagram utilizing the tube previously described as a control for memory tubes. Tube I is the horizontal positioning control for the reading beam of the memory tubes I02, I03 and I04 while tube IOI is the vertical positioning control. In this circuit the control tubes may be called masters and the controlled tubes slaves. The cathode beam I51 of horizontal positioning tube I00 is driven to a preselected position on the target of the tube through selector diodes I55 as discussed above while the .beam I62 of tube IOI is driven to another preselected position through diodes I60. The memory tubes are so connected to the masters that their respective reading beams assume automatically the same position horizontally as the beam of tube I00 and that vertically of the beam of MI. A bank of three memory tubes only is diagrammed but any desired number may be slaved to the same two masters. It is assumed that the dimensions of the screen and the linear sensitivity of the slave tubes are the same as the corresponding characteristics of the masters but predetermined positions will be in any case assumed by the beams of the slaves.

The memory tubes of Figure 8 are quite similar 'to those described by Haefi in Electronics, September 1947, pages 80-83. A bifurcated envelope IE1 is shown but the plain envelope ofthe cited publication may be utilized instead. These memory tubes I02, I03 and I00 contain identical mosaic screens I05 upon which can be stored desired information in the form of electric charges. Each screen I05 consists of numerous discrete metallic particles I06 deposited or otherwise mounted on a dielectric support I01. A pattern of electrostatic charges induced on the particles will be retained intact for some time since they cannot leak away. Each of the memory tubes carries in bifurcation I08 an electron gun I08 and associated deflection plates I 00 utilized to establish the desired charge pattern on the screen I05 by means of electron beam I60. This process is called writing. External connections to the guns I08 and the plates I00 may be made in exactly the manner prescribed by the Haeff publication and are accordingly omitted from the drawing.

In bifurcation I 69 each of the memory tubes carries a second conventional electron gun I I0 producing an electron beam I65 used to scan the mosaic and withdraw information stored there. This process may be termed reading and is possible because of the fluctuations in the beam I65 caused by the deposited charges. Beam I05 may be used in addition to restore the electrons that leak away with time no matter how good the dielectric propertie of the screen, thus enabling data to be dynamically stored for any desired period. A third electron gun may however be used to carry out this holding function.

In order that a predetermined area of the memory mosaic may be scanned the electrostatic deflection plates of the tubes are connected in parallel with the plates of the control tubes. Thus plate III of tube I00 is connected through leads I21, I28, and I to plate H5 of tube I02, through leads I21, I28, I and IOI to plate IIII of tube I03 and through leads I21, I28, I30 and I32 to plate I23 of tube I00. The positive A bias of tube I00 is connected to plate I II through junction I5I. Deflection plate II2 of tube I00 connects with the amplifier I59 through junction I52 of leads I33 and I30 and through these leads and I35 to plate H0 of tube I02, through I33, I34, I36 and I31 to plate I20 of tube I03 and to plate I24 of tube I05 through leads I33, I00, I30 and I38. Plates H5 and H6, H0 and I20 and I23 and I20 are thus seen to be connected in parallel with the plates I I I and H2 of horizontal control tube I00. In like manner the deflection plates of vertical master tube IOI are connected in parallel with the vertical plates of the slave tubes. Plate H4 is connected through leads I39, I40 and MI to plate I26 of tube I00. The positive bias of tube IOI enters at junction I54 of leads I39 and I40. Plate H4 is also connected through leads I30, I00, I02 and I43 to plate I22 of tube I03 and through leads I30, I40, I02 and I44 to plate II8 of tube I02. The connection to plate II3 are through leads I05 and I06, amplifier I64 being joined to the circuit at the junction I53 of these leads. Lead I 00, connects through lead I41 to plate I25 of tube I00, through I48 and I09 to plate I2I of tube I03 and through I48 and I50 to plate I I1 of tube I02.

The control systems of the master tubes I00 and IOI are those described previously. Selector diodes I are individually connected to the segments of target I50 in tube I00. Electron beam I51, generated by conventional electron gun I10, passes through anode I12 and is defiected by plates III and H2, to the desired segments of the target. The outputof target-ll56 connects through diode-ladder I 58 and amplifier 159 to plate H2. Positive bias is suppliedtothe otherplate III. 'lhe connections-of tube I'M are-similar: to-those of-tube "100 but it is to be emphasized that the-tubes are e-ntirel tindepen'dent of each other. Selector diodes tfitlare connected-to the segments of target 161 which is struck by beam I 62. Thisbeamsisgeneratediby conventional gun I'll, passes through'anode ln and is defiected byplates I13 and 4. Plate H3 is connected to thetarget l-Bl throughamplifier 64 and diode ladder l 63. Plate I [4 carries the usual positive bias.

The operation' of the entire circuitdiagrammed in Figure '8 can be better understoo'dby reference to Figures 9, 10and l1. 1 Figure 9 shows the'target IGI of vertical control ma'stertube lM -with the spot I15 made by beam Hi2 impinging theren. Spot l15is held-in position'on-the line separating segments 12 and M in the target'by proper choice of theselector diodes. Since the verticalplates of each'of the slave tubes areconnected in parallel with the plates of thevertical control, the spots I'IB of the formerare in the corresponding verticalposition on mosaic I65. In like manner Figure shows the target I55 of horizontal positioning control I60 with the spot I14 made by beam I51. This spot I74 is held in the 'horizontal position on the line dividingsegments l2-and l3. Because-of the parallel connections the'spots I16 of the slave tubes assume the corresponding horizontal position on the-mosaics. "The targets of Figures 9 and 10-: areshown at right-angles to each-other merely for' purposes of*clarity. "Figure 11 illustrates the final positiontaken-by the beams T65 of the slaves in response to thesignalsfrom the master tubes. ltwillbe-evident that any-other desired position of the scanning beams of the slaves'can be indicated-merely by choice of the necessary-selector controls. Since all controls-are electronic;shifts in scanningpositionand scanning of information can be made in periods of microseconds.

1 claim:

' 1. Ina system for positioning the electron beam of a'first cathode ray tube,-.asecondcathode ray tube containinga pair-'ofelectrostaticplates for deflecting-the 'electron beam thereof anelectricallyconductive targetfor the electron beam formed ofdiscrete rectangular segments separated by non-conductors =-one end 'of *said target being grounded means forgrounding any'selected number of segments including said grounded end,

inflsaid first cathode ray tube in direct'relationship. to the potential of the electrostatic plates-of saidsecond cathode ray tube.

12.. ,In a. system for positioning the electron beam of afirst cathode ray tube,-a second cathode ray tube comprising a pair of electrostatic platesfor deflecting the electron beam thereof and anelec- "trically conductive target for the electron'beam formed of discrete metallic rectangular segments separated'by insulators; means for grounding in sequence all-of the segments beginning with that at one end of-said target, means for generating "on the electrostatic plates voltage for retaining the electron beam on a'zposition at least touching the unground'ed segmentadjacent a grounded "segmentand means-synchronizing the position of 8 the beam of the first cathoderay-tube with' that of thesecond.

'3. In a system forpositioning thei'electronzbeam of a first cathode ray-tube, asecond cathoderay tube comprisingra- .pair of electrostaticrplates :for deflecting: the electron beams thereof an: electrica'lly conductive target forzthe electronrgbeam formed: of discrete segments-:oneend :of said :target :being grounded, means -forqgroundinge'anyselectednumber of segments including said grounded .end,umeans"v for. developing a: potential. on the said r-electrostatic plates to "retain the electron beam striking about 5 a spot between adjacent grounded and non-grounded segments'andmeans for adjusting thepotentialnonxtheelectrostatic plates in said first'cathode-ray tubein direct-relationship to" the potential of. the said electrostatic plates of said second :cathode ray tube.

I i. Inasystem for positioning .the electron beam of a'first cathode ray tube having electrostatic deflection plates,'a second cathode ray tube comprising a pairof electrostatic plates for deflecting the electron beam thereofand a conductive: target .for the said-beam formed of discrete metallic segments, means for grounding anyselected number of the said segments,- means for generating on the electrostatic plates of thesaid second tube-voltage for retaining the electron beam onvaposi-tion at least touchin the ungroundedsegment adjacent a grounded segment and :meansfor'adjusting the potential on said electrostatic plates in said first cathode ray tube in direct relationship to the potential of the electrostatic platesof said second cathode ray tube.

.5. In a system (for.positioningtheelectron beam of a first cathode ray tube having deflection plates, a second cathode ray tube comprisingma pair of deflection .plates for deflecting theelectron beam thereof and a conductivetargetfor the said beam'formed of discrete electrically conducting-segments, one end of. said target .being grounded, adiode-ladderffor groun'dingany selected number of segments including said, grounded end, .meansfordevelopinga potential on the deflectionplates to retain the electron beam striking at about a spot between adjacentgrounded and non-grounded segments, and meansforadjusting the potential on said deflection plates. in said first cathode ray tube in direct. relationship to thepotential. of the said deflection plates of said second cathode raytube.

, 6. Inasystem for positioning the electron beam of a first cathode ray tube. having deflection plates, a second cathode ray tube comprising a pair of deflection platesfor deflecting the electron beam thereof and a conductive target for the said, beam formed of discrete electrically'con- 'ductingsegments separated by insulators, one end of said target being grounded, ,a diode ladderfor grounding any selected number of segmentsineludingv said grounded end, means for developing a potential on the deflection plates of the said secondltube. to retain the electron ,"beam striking a spot about the insulator between adjacent grounded andinon-grounded segments, and. means'for adjusting fthepotential on the. said deflection plates in said first. cathode ray tube indirect relationship tothe potential of.thelsaid-deflection :plates of said second cathode ray tube.

7. In a. system .forypositioning the. electronbeam of a, first. cathodeiraytube having electrostatic deflection plates,asecond cathode ray tube. comprisingapair of electrostatic-deflection plates for deflecting the. electron beam thereof and: a con- .ducti-v.e:itargetfor..rthe: said beamiformed ofcdiscrete electrically conducting segments separated by insulators, one end of said target being grounded, a diode ladder for grounding any selected number of segments including said grounded end, means comprising an amplifier for developing a potential on the electrostatic deflection plates of said second tube to retain the electron beam striking a spot about the insulator between adjacent grounded and non-grounded segments, and means for adjusting the potential on the said deflection plates in said first cathode ray tube in direct relationship to the potential of the said electrostatic deflection plates of said second cathode ray tube.

CHESTER H. PAGE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Cunnifi May 1, 1945 Goldsmith Aug. 14, 1945 Flory July 13, 1948 Mesner Jan. 11, 1949 Mesner Oct. 3, 1950 Mesner Oct. 3, 1950 Pierce et al Nov. 20, 1951

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