US2801355A - Target structure for color television display tubes - Google Patents

Target structure for color television display tubes Download PDF

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US2801355A
US2801355A US428622A US42862254A US2801355A US 2801355 A US2801355 A US 2801355A US 428622 A US428622 A US 428622A US 42862254 A US42862254 A US 42862254A US 2801355 A US2801355 A US 2801355A
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grid
screen
deflection
tube
color
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Crais S Nunan
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Chromatic Television Laboratories Inc
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Chromatic Television Laboratories Inc
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Priority to NL105209D priority Critical patent/NL105209C/xx
Priority to BE538028D priority patent/BE538028A/xx
Priority to NL197037D priority patent/NL197037A/xx
Priority to US428622A priority patent/US2801355A/en
Application filed by Chromatic Television Laboratories Inc filed Critical Chromatic Television Laboratories Inc
Priority to DEC11190A priority patent/DE1015842B/de
Priority to FR1123938D priority patent/FR1123938A/fr
Priority to CH332357D priority patent/CH332357A/de
Priority to GB13518/55A priority patent/GB787409A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/20—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours
    • H01J31/201—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/80—Arrangements for controlling the ray or beam after passing the main deflection system, e.g. for post-acceleration or post-concentration, for colour switching
    • H01J29/803—Arrangements for controlling the ray or beam after passing the main deflection system, e.g. for post-acceleration or post-concentration, for colour switching for post-acceleration or post-deflection, e.g. for colour switching
    • H01J29/806—Electron lens mosaics, e.g. fly's eye lenses, colour selection lenses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/86—Vessels; Containers; Vacuum locks
    • H01J29/861—Vessels or containers characterised by the form or the structure thereof
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/16—Picture reproducers using cathode ray tubes
    • H04N9/22—Picture reproducers using cathode ray tubes using the same beam for more than one primary colour information
    • H04N9/26—Picture reproducers using cathode ray tubes using the same beam for more than one primary colour information using electron-optical colour selection means, e.g. line grid, deflection means in or near the gun or near the phosphor screen
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2229/00—Details of cathode ray tubes or electron beam tubes
    • H01J2229/86—Vessels and containers
    • H01J2229/8613—Faceplates
    • H01J2229/8616—Faceplates characterised by shape
    • H01J2229/862—Parameterised shape, e.g. expression, relationship or equation

Definitions

  • This invention relates to target and color control structures for cathode-ray tubes designed for display of television images in substantially natural color. Specifically, it relates to such tubes of the type wherein the cathode-ray beam which traces the image is refocused in the'space adjacent to the display screen so that a beam, which is of the order of magnitude in cross-sectional area of one elemental area or image point of the picture displayed, is concentrated on a sub-area of smaller size.
  • the sub-area on which the beam is focused is occupied by -a phosphor emissive of light of one component color of a combination additive to produce White. in the region of the display screen has been termed and will be referred to herein as post deflection-focusing.
  • the structure is such-that, when a suitable potential difference is applied between the apertured grid and the electron permeable auxiliary electrode, there is formed a multiplicity of electron lenses distributed over the target area and each having an aperture of the order of magnitude of one picture element.
  • the screen is provided with sub-areas of phosphors grouped in a repeating pattern across the screen, each group comprising phosphors .emissive of all of the.component colors of the additive system employed and'each group electro-optically alined with a corresponding aperture of the grid.
  • the particular "color displayed at any instant isdetermined either by the angle of incidence of the beam at the grid or by microdeflection of the beam ac complished in the plane of the grid-itself. In the latter case the grid is formed out of two setsof'interleaved electrodes.
  • Electrodes of the two sets establish fields which deflect the electrons passing through, the mean potential of the two sets being maintained, with respect to the auxiliaryclectrode, such as to effect the desired lens action and bring the beam'to a refocus upon the proper color.
  • the most convenient form to manufacture is one wherein the auxiliary electron permeable electrode is a thin conducting film, usually of aluminum, deposited onthesurfa-ceof the display screen itself.
  • This not only has the advantage of simplicity of construction but reduces the power required to effect the scanning deflection of the beam when producing an image of a given brilliance, since the same potential difference which does the post-deflection focusing also;accelerates the electronsand imparts greater energy to them as they arrive at the-screen.
  • Patented July 30, 19157 the amount of deviation from, the straight path becoming greater as the scanning angle is increased; accordingly, the phosphor areas must be alined with their corresponding grid' apertures. electro-optically rather than structurally, to take account of the curvature of their paths in the grid s'creen region.
  • The. principles underlying such electro-optical alinement are set forth in the copending application of Ernest 0. Lawrence, Serial No. 399,754, filedDecember 22, 1953.
  • the focusing effect of the gridto-scree'n field also varies with the angle of deflection, the focusingeffect. being. stronger with greater angles offincidence of'the beam at the grid.
  • the beam is brought to a sharp focus at the center of the screen it will be overfocused and produce a larger focal spot as it "is deflected toward the edges of the screen; conversely, sharp focus at the screen edges willrcsult in less than complete convergence at the center of the screen and hence a. compromise value of focusing voltage is frequently used in order to obtain a minimum average spot size.
  • the sensitivity of the beam to a given deflecting voltage also increases with the angle of incidence of the beam at the grid. This'latter effect can, be 'compensateito a large degree, by varying the shape of the phosphor areas as is disclosed in thecopending application of Ernest 0. Lawrence,- Serial-No. 399,753, also filed December 22, 1953.
  • the varying sensitivity to micro-deflection at the grid can also be compensated by imparting a curvature to the screen-or the. grid, ,so that electrons travelling in theinterspace between screen and grid at the center of the screen have alonger distance to travel after the micro-deflecting impulse has been applied than those traversing the grid structure at the edge of the screen.
  • the displacement of the point ofimpact by a given applieddefleeting impulse becomes. substantially uniform.
  • the problem of electrooptical alinement of the grid apertures and phosphor groups can be solved in this latter case by applying the same principles as where uniformgrid-to-screen spacing is. employed.
  • the expedient has, however, no effect on the defocusingofthe beam by varying angles of incidence.
  • Thebroadpurpose of the present invention is to provide a targetstructure, including display screen and electron lenssystem, which permits simultaneous solution of the-three problems of electro-optical alinement, uniform focusing-throughout the display area and uniform-microdeflection sensitivity.
  • Other objects and advantages accomplished by the invention are the provision of a structure which permits a maximum duty cycle to be utilized in the display of either color or monochrome television images, to provide a target structure which will give uniform spot size and definition, both as to color and monochrome, in all parts of the screen; to provide a structure wherein the display screen may be formed upon the viewing window of the tube itself, instead of upon an auxiliary base positioned within the tube and behind thewindow, the screen having sulficient strengthto withstand atmospheric pressure even in large sized tubes, and, by virtue of theimposition of the screen upon the window, avoiding the transmission losses through multiple glass surfaces at which reflection losses can occur; to provide a type of target' structure which may, in an approximate, slightly modified form, he cheaply constructed and readily .computed
  • the position of the focal point or maximum convergence of the electron beam is determined wholly by the ratio of the accelerating voltages between the beam source and the grid to that between the grid and the equi-potential plane, the shape of the grid apertures, and the angle of incidence of the beam at the grid, and is substantially independentof the distance between grid and the equi-potential surface.
  • an additional electrode structure is utilized, this structure comprising a I second grid mounted between the first grid and the screen.
  • the second grid is also preferably comprised of wires tightly stretched across the display screen in a direction normal to that of the electrodes comprising the first grid.
  • the wires of the second grid act to form slightly diverging lenses, increasing in some degree the size of the focal spot in a dimension parallel to the phosphor strips, but have. no defocusing effect in the direction of width of the strips.
  • the effect of the second .grid With other types of focusing and display screen, the effect of the second .grid
  • the invention when used in tubes of the type using linear grid electrodes and strip phosphors a relatively close approximation to the desired uniform focusing and uniform deflection sensitivity can be attained by using a screen which is curved in only one dimension; i. e., is a section of a right cylinder whose axis lies in a plane at right angles to the planes of the grid electrodes. .
  • the deflection sensitivity when used in this modified form in a tube wherein the maximum scanning deflection is 72 the deflection sensitivity may be held constant to within :2.2% over the entire screen area and the maximum spot size will be only 2.2% of the aperture width greater than the minimum;
  • the width of the spot will vary between 3 mils and 3% mils; the corresponding variations in a like tube using a planar screen and grid are 11%.
  • the variation in spot width will be between a minimum of approximately 3 mils and a maximum of approximately 4 and the micro-deflection sensitivity can be held constant to within i-3% throughout the screen.
  • the variation in deflection sensitivity is about i20% and the variation in spot sizeis over 100%, i. e., between a minimum of 3 mils and a maxi- -mum of about 7 mils.
  • Fig. l is a diagrammatic view, in cross-section, of a cathode-ray color-television display tube embodying the present invention
  • Fig. 2 is a fragmentary cross-sectional view of a disicate the order of this arrangement.
  • Fig. 3 is an exaggerated perspective view of a viewing screen, shaped in accordance with the present invention, and adapted to give complete focusing and deflection sensitivity correction over the entire screen;
  • Fig. 4 is a similar view of a cylindrical screen, adapted to give approximately uniform focusing and deflection sensitivity throughout the screen area;
  • Fig. 5 is a family of curves illustrating, in terms of the spacing between the grids of the tubes of this invention, the screen curvature in various planes parallel to the conductors of a linear-element deflecting grid.
  • the tubes in which the present invention is incorporated may be conventional in structure, comprising an evacuated envelope of generally funnel-shaped form, which may be either of glass or of glass and steel construction.
  • the tube comprising a cylindrical glass neck 1 wherein is mounted an electron gun having an electron emitting cathode 3, a control grid 5, a first anode 7 and a second anode 9, with the usual connections for applying suitable electrical potentials to each of these elements.
  • the second anode is preferably connected either to the funnelshaped metal shell 11 which constitutes the body of the tube, or, if the tube be of all glass construction, to a conductive coating deposited upon its inner surface.
  • a viewing window 13 which, in the case of the tube illustrated in Fig. 1 constitutes the base upon which the light emitting phosphors of the display screen are deposited. It will be noted that the window is illustrated as curved, i. e., convex outwardly. The exact form of this curvature will be discussed hereinafter.
  • Fig. 2 shows, upon an enlarged scale, a small crosssection of the window 13 and the phosphor screen thereon.
  • Deposited upon the base 13 are strips of phosphors which are emissive, upon electron impact, of light of different component colors additive to form white.
  • Each group of strips extends across substantially the entire face of the screen in one dimension, and its width, which is uniform or very nearly uniform throughout its length, is of the order of magnitude of one element or picture 'point of the television images to be displayed thereon.
  • the strips are deposited in a repeating pattern in the order red, green, blue, green, red, etc., and in the diagram of Fig. 2 the various strips are designated as the initial letters R, G, and B, to indi- Preferably, overfilm 15, which is permeable to electrons.
  • films are well known in the art and they are usually of aluminum. They serve the triple purpose of establishing a definite potential for the screen, of reflecting back, out through the window, light which would otherwise be radiated back into the body of the tube and lost, and of suppressing, to a considerable degree, the secondary emission of electrons.
  • This conducting film is not, however, an absolute essential in the operation of the tube, since under the bombardment of the cathode rays the screen will emit secondary electrons until it reaches an equilibrium potential which is only a few volts negative to certain portions of the electrode structure of the target the film 15 may be omitted.
  • a grid 17 of fine wires or other linear conductors Stretched across the viewing window or screen and in a direction substantially normal to the phosphor strips is a grid 17 of fine wires or other linear conductors
  • the spacing of the conductors of the grid 17 (hereinafter referred to as the second grid, even though it is the first to be described) is not critical, although preferably it is of the same order of magnitude as the spacing of the centers of successive green strips tin thewscreen; Asawill be shown hereinafter it isaconvenient that the conductors of the grid l7contactz the edges of the screen, although .this,.;too, isnot essentialto the operation of the tube as will be set forth in detail hereinafter. It will be obvious from a-description of the construction that:the grid "17 is substantially planar when considered as a :whole.
  • a second grid oflinear electrodes, 19 and 19' Mounted in a plane parallel to that-iofj the grid 17 is a second grid oflinear electrodes, 19 and 19', whichextend across the surface of the screen in a direction substantially normal to the extension of the conductors of grid 17 and therefore substantially parallel to theaphosphor strips.
  • The: conductors 19 and 19 alternate.
  • the set of conductors 19 is connected to a common lead 21 which is brought out through the envelope.
  • conductors 19' are connected "to a common lead 21 also brought out through the wall of the envelope.
  • the two sets of conductors are mutually insulated so that apotential difference can be established'between the two sets ofconductorsto effect micro-deflection of'the beam.
  • the conductors 19 and.19' are so positioned that the center of the aperture'formed between each adjacent pair of electrodes is electro-optically centered in front of the center of'a corresponding one of the green emitting strips G; that is, they are so positioned that whenthe electronfor concentrating the beam from the electron gun and for scanning it over the surface of the target area, are employed. Since such focusing and deflecting coils are conventional and are not a part of the present invention they are omitted for simplicity in the drawing and description.
  • the cathode 3 is operated at the lowest 'potential'in the system, and anodes 7 and 9 are progressively more positive.
  • the two sets of electrodes 19.and 19, comprising the first grid are preferably operated at a potential of between 200 and 400 volts negative to that of the second electrode and the tube shell, assuming that "the latter is in the neighborhood of 5000 volts to 8000 volts positive with respect to the cathode.
  • This refers to the mean potential of the two sets of electrodes; in operation an oscillating voltage of perhaps 400 volts peak to peak is applied between the two sets of electrodes of-the grid.
  • the second grid 17 is operated at a potential considerably higher than the mean potential of the first grid, and the conducting film 15 is connected to and therefore operated at the same potential as the grid17.
  • the cathode-ray beam is deflected bidimensionally over the area of the viewing screen to trace a raster thereon in accordance with .usual television practice, vertically at substantially 60 cycles per second and horizontally at substantially 15,750 cycles per second in accordance with present standards in transmission in the United States, or in accordance with whatever other standards may be employed in the service for which the tube is to be used.
  • the conductors 19 and 19' extend across the screen in the direction of the higher frequency or line deflection.
  • the cathode-ray beam developed by the electron gun travels in a substantially straight line from a center of deflection, the exact position of which depends on the position of the deflecting coils, to reach the plane of the first grid 19-19 at varying angles of incidence.
  • the beam passes through the plane of the considered-overall, and through the major portionof-the distancebetwen the-two ,grids it is substantially uniform and-in ardirection normal to the plane of bothgrids; thereforeit-bends, :the beam so thatits angle of incidence to-the-;second grid is less than that of its angle of incidence to-the first grid.
  • thefield In the immediate neighborhood of the grids thefield is concentrated on the conductors-comprising them. Inzthe plane of the first grid this .field is directed away-from the wires, giving the electrons constituting the-beam an impulse which tends to converge them. This impulse is in the direction normal to the wires and its effect is-to make the beam converge into a fine-line parallel to-the grid conductors.
  • the. distance between the grids will be of the order of 10to 15 times .the-distance between thegrid conductors, andwith these proportions no material error is involvedin, considering that the entire impulsewhich causesthe. convergence of the beam is applied to theplane of the grid itself.
  • the screen is materially shorter than that betwen the grids, and-therefore the electrons have a shorter time in which to diverge, even at the center of thetube where the distance between the second grid and screen is greatest.
  • the electrons of the beam are subjected to three different accelerations which divert them from their straight line paths.
  • the first of these is an acceleration directly toward the second grid and screen, resulting in a refraction of the beam as a wholeand causing its center to fall on a point of the screen closer to the axis of the tube than it would if the field were not applied.
  • the second is the converging or focusing action of the second grid.
  • the third is the micro-deflection of the beam which controls the color displayed by the tube and which will be referred to hereinafter as the color deflection to distinguish-it from the scanning deflection.
  • the screen as to accomplish all of these purposes will next the screen is lower and it is therefore subjected to the accelerating field for a longer time and because the component of velocity added in the grid-to-screen' region, normal to the screen, is a greater proportion of its total
  • the sensitivity'to focusing is also greater at greater angles of incidence, both because of the longer time taken by the electrons in passing through the field where focusing deflection takes place and because there is a longer time during which the electrons are traveling between grid and screen and the velocity components causing the convergence is effective.
  • the sensitivity to the color deflection increases with increased angle of incidence for the same reason, and substantially to the same extent as does the focusing sensitivity.
  • the focusing effeet is substantially independent of the distance between grid and screen. If it were possible, in a practical tube, to give the screen and grid both a curvature concentric about the center of scanning deflection, the angle of incidence of the beam would be a constant and uniformity of both focusing and color deflection would be achieved. With screens of the size now demanded for television viewing, however, such concentricity would involve either an unduly long tube or a screen so convex as to cause an apparent distortion of the image when viewed. Either the screen or the grid can be curved to give substantially uniform deflection sensitivity, but in other than the concentric relationship this does not help defocusing.
  • the screen can be given a curvature and the relationship between the pitch of the grid wires and the width of *the phosphor strips can be so adjusted that not only 'are the groups of phosphor strips electro-optically alined with the corresponding apertures in the color control grid, but the screen lies in the focal surfaces of the various electron lenses forming the color grid and because of the similarity of the conditions for focusing and for color deflection sensitivity, the latter is substantially uniform
  • the conditions for so forming be discussed in detail.
  • Refraction is proportional to the square root of the potentials of these various elements with respect to the cathode.
  • potential of the first grid is so nearly that of the second anode of the electron gun that the space between the gun and the first grid may be considered, without appreciable error, as an equi-potential space, and all lines of force originating on one grid may be considered as terminating upon the other, since the space between the second grid and the screen'is substantially equi-potential.
  • the quantity y is the distance in the direction normal to the electrodes of the first grid, between the foot of a perpendicular dropped from the center of one of the electrodes 19 or 19' and the center of a corresponding red or blue emitting phosphor strip, as the case may be, at a given point of incidence of the beam corresponding to a particular value of 0; or, stated otherwise, it is the distance measured in the same direction between the foot of a perpendicular dropped from the center of the aperture between two electrodes 19 and 19 and the center of the corresponding strip of green emitting phosphor.
  • the quantity y varies with both a and 5 components of the angle 0.
  • the ratio of pitch of the grid wires to the phosphor spacings varies from the center of the sceen outwardly toward its edges, as is the case with the single planar grid and planar screen, and correction for the distortion and pitch change can be accomplished in the same manner as is disclosed in the Lawrence application, Serial No. 399,754, identified above.
  • the change in ratio of spacing can be accomplished either by varying the widths of the phosphor strips or by varying the pitch of the grid electrodes, either continuously or in zones, from the center of the screen out toward the edges.
  • Equation .1 is given interms .ofithe. component angle ofincidence B, .the actual point .of :impact of any. electron upon the screen is related .to 'i'ts point :of entry at the grid. by its component of velocity parallel to the grid plane, times the. time interval between the instant of passing through'the color control gridand the impact upon the-screen;
  • Fig. 5 there is given a series of curves in which the value of as computed from Equation 4, is: plotted for various values 'of the angle 0 and its component [3. These curves are. plotted for tubes of two different designs. In this figure, curves 25, 27, 29 and 31 are plotted with respect to .ahtubeof. the deflection type, while curves 3'1, 33 and 35 refer'to 72 tubes; i. e., with regard to the first set of curves the maximum value of 0, when the beam isdefiected to the corners of the display screen, is taken at 45, while in the latter set of curves the maximum angle of 0 is'36.
  • Curve 25 gives the values of F on the horizontal axis of the screen, where tan [3:0.
  • Curve 27 is plotted for a 'value of tan 9:0.361. and curve29 for a'zvalue ofitan 8:0.600, i. e., for the upper and loweredges .of the field where the angle )8 is a maximum. .1
  • curves 27 and 33 lie approximately equidistant from those representing the maximum and minimum concavity of the screen, along its axis and at its edges respectively.
  • Va is the voltage applied between conductors 19, 19'
  • s is the spacing of the wires or other electrodes of the grid
  • w is to the diameter of the grid wires, the other symbols used having the same significance as before. It may be noted in passing that the expression given is actually for the change in sine 3 but because of the small values of deflection angle used in practice, the angle and its sine are effectively equal. Since Equation 2 gives the change in y for small changes in the value of 19, the relative displacement of the spot,
  • Equation 7 is similar in form to Equation 3, and except for coeflicientswhichare constant (or can be made constant) for any given tube, the equations are substantially identical.
  • the ratio .K is a constant and is the same for both equations.
  • the deflecting voltage Va is, at any instant, constant throughout the tube.
  • the only quantity which may vary .with' angle and which is not identical in the two equations is the denominator in the first term at the right of the equality in Equation 7. If the refraction correction is accomplished by varying the width of the groups of phosphors, rather than the pitch of the grids, this term is also a constant over the surface of the screen.
  • the deflection sensitivity will also be constant. If the refraction correction is accomplished by varying the pitch of the grid wires, the widths of the phosphor groups being maintained a constant, there will be a slight difference in the sensitivity to deflection due to the changes in the quantity
  • the spacing of the grid wires averaged approximately 30 mils and the diameter of the grid wires w is 6 mils. The total difference in spacing of grid wires requisite to accomplish the necessary screen, was approximately one percent. The corresponding change in the quantity Zn iii) was about 0.6%.
  • the refraction correction, applied to maintain the apertures and phosphor groups in electro-optical alinement, is accomplished by varying the width of the phosphor groups, there is some theoretical advantage in maintaining the width of the central strips (green in the example here given) constant and taking up the width variation in the strips which are electro-optically centered under the grid wires, i. e., the red and blue emitting strips. Because the total variation is so small, however, this advantage is more theoretical than practical.
  • the over-all difference in phosphor group width as between center and edge of the screen is, in the case mentioned, only about one percent, and if the difference is applied equally to the red, green and blue strips, it is only about one-tenth of a mil. Since this is of a lower order of magnitude than the mechanical precision which at present seems desirable to maintain in commercial manufacture, any errors due to the method in which the correction for refraction are applied can usually be neglected.
  • Curve 30 shows the variation of the ratio F/D along the vertical axis of the screen of a 90 deflection tube, where the curvature is greatest.
  • the maximum degree of curvature in the vertical plane, for exact focus, is only about one-fourth as great as that in the horizontal plane.
  • a screen which is, in form, a right cylinder.
  • the contour of such a cylinder conforms in curvature to substantially the value shown in curve 27 or, in a 72 tube, with that indicated by curve 33.
  • curves are drawn for values of the angle 5 where the amount of defocusing is substantially equal at the top and bottom and at the center of the vertical axis of the screen, the beam being underfocused at the center and overfocused at the upper and lower edges.
  • the bulge of the display screen for a fully corrected tube is only 0.153 inch maximum, and. that of the compromise cylindrical screen only 0.137 inch.
  • the screen has enough of a bulge to withstand atmospheric pressure but not enough so that its curvature is'obtrusive or to cause an apparent distortion of the television image because it is displayed on a curved surface.
  • the ,secondgrid has a diverging or defocusing effect in the direction normal to the focusing effect of the first grid.
  • the effect of the defo'cusingaction- is to-lengthenthe focal line or spot in the direction ofthe line scanning. If the primary focus of the beam, as accomplished by the electron gun and the usual focusing; coil is poor, resulting in an initially over-large spot, this may be important, but under ordinary.circumstances it is not.
  • the amount of the defocusing action which occurs is directly proportional to the distance F,- since the space between the second grid and the screen is substantially a unipotential space as the second gridand screen are directly connected.
  • some of the lines of force which the theory of operation; of'the invention assumes terminate on the second grid will actually terminate on the screen itself; i. e., in the narrow zone where the distance between second grid, and soreeniis small in comparison with the separation of the second grid wires.
  • the amount of convergence in the second gridscreen region, required to bring the beam to the minimum focal size is so small that it is unimportant. In the.
  • the second grid causes substantially no divergence in the plane normal to the second-grid wires.
  • the increase in the length of the focal line is less than 20% of the diameter of the beam as it enters the focusing structure, and it is to be remembered that this can be as small as is normally the case in monochrome tubes.
  • the principal eifect of the divergence of the beam is to make any shadow which the second grid wires might otherwise cast upon the screen less prominent.
  • a cathode-ray tube for the display of television images in color which comprises an evacuated envelope including a window area through which the images may be viewed and an electron gun within said envelope for developing a beam of cathode ray directed toward said window area and adapted to be bidimensionally deflected thereacross to trace a raster; a target and color control structure comprising a substantially planar grid positioned adjacent to said window area and approximately equal thereto in size, said grid having a multiplicity of apertures therein closely and substantially uniformly spaced over substantially the entire area of said grid, a second grid of like character positioned between said first grid and said window area in a plane substantially parallel to said first grid, terminals external to said envelope connecting respectively to said grids for applying different electrical potentials thereto, and a display screen mounted in said window area and comprising a transparent base, a coating on said base comprising phosphors emissive on electron impact of light of different colors, said phosphors being disposed in groups
  • a cathode-ray tube for the display of television images in color which comprises an evacuated envelope including a window area through which the images may be viewed and an electron gun within said envelope for developing a beam of cathode rays directed toward said window area and adapted to be bidimensionally deflected thereacross to trace a raster; a target and color control structure comprising a substantially planar grid positioned adjacent to said window area and approximately equal thereto in size, said grid comprising a plurality of linear electrodes closely spaced to form a multiplicity of apertures therebetween substantially uniformly spaced over substantially the entire area of said grid, a.
  • second grid of like character positioned between said first grid and said window area in a plane substantially parallel to said first grid, and with its linear electrodes running in a direction substantially normal to that of the electrodes of said first grid, terminals external to said envelope connecting respectively to said grids for applying different electrical potentials thereto, and a display screen mounted in said window area and comprising a transparent base, a coating on said base comprising strips of phosphors emissive on electron impact of light of difierent colors, said phosphor strips being disposed substantially parallel to the electrodes of said first grid in groups forming a repeating pattern covering substantially the entire area of said screen, the width of each group being of the order of magnitude of one elemental area of the images to be reproduced and including all of said phosphors and each group being electro-optically alined with a corresponding aperture of said first grid, a conducting film disposed over said coating and means for connecting said second grid to said conducting film, said base being concavely curved toward said electron gun.
  • a cathode-ray tube for the display of television images in color which comprises an evacuated envelope including a window area through which the images may be viewed and an electron gun within said envelope for developing a beam of cathode rays directed toward said window area and adapted to be bidimensionally deflected thereacross to trace a raster; a target and color control structure comprising a substantially planar grid positioned adjacent'to said window area and approximately equal thereto in size, said grid comprising a plurality of linear electrodes closely spaced to form a multiplicity of apertures therebetween substantially uniformly spaced over substantially the entire area of said grid, a second grid of like character positioned between said first grid and said window area in a plane substantially parallel to said first grid and with its linear electrodes running in a direction substantially normal to that of the electrodes of said first grid, terminals external to said envelope connecting respectively to said grids for applying different electrical potentials thereto, and a display screen mounted in said window area and comprising a transparent base, a coating on said base comprising
  • a cathode-ray tube for the display of television images in color which comprises an evacuated envelope including a window area through which the images may be viewed and an electron gun within said envelope for developing a beam of cathode raysdirected toward said window area and adapted to be bidimensionally deflected thereacross to trace a raster; a target and color control structure comprising a substantially planar grid positioned adjacent to said window area and approximately equal thereto in size, said grid comprising two interleaved and mutually insulated sets of elongated linear conductors, adjacent conductors being substantially uniformly spaced over substantially the entire area of said grid to form a multiplicity of .apertures therebetween, a second grid positioned between said first grid and said window area in a plane substantially parallel to said first grid, and comprising elongated linear conductors disposed in a direction substantially normal to that of the conductors of said first grid, terminals external to said envelope connecting respectively the sets of conductors of said first grid and to said second grid,
  • a cathode-ray tube for the display of television images in color which comprises an evacuated envelope including a window area through which the images may be viewed and an electron gun within said envelope for developing a beam of cathode rays directed toward said window area and .adapted to be bidimensionally deflected thereacross to trace a raster; a target and color control structure comprising a substantially planar grid positioned adjacent to said window area and approximately equal thereto in size, said grid having a multiplicity of apertures therein closely and substantially uniformly spaced over substantially the entire area of said grid a second grid of like character positioned between said first grid and said window area in a plane substantially parallel to said first grid, terminals external to said envelope connecting respectively to said grids for applying different electrical potentials thereto, and a display screen mounted in said window area and comprising a transparent base, a coating on said base comprising phosphors emissive on electron impact of light of difierent colors, said phosphors being disposed in groups electro-optieally
  • a cathode-ray tube comprising an evacuated envelop and an electron gun adapted to direct a beam of electrons against a target area within said envelop, said beam being deflectable to fall or any portion thereof, a target structure positioned within said target area and comprising a cylindrically curved display screen, a coating comprising a repeating pattern of strips of phosphors emissive upon electron impact of light of different colors additively producing white deposited on said screen in a direction normal to planes including the cylindrical axis of said screen, a grid of parallel conductors tautly supported across chords of said cylindrical screen 6 and secured closely adjacent to the edges thereof, and a second grid of parallel conductors tautly supported in a plane substantially parallel to the plane of said first mentioned grid, the conductors of said second grid being parallel to and electro-optically alined with strips of said coating.
  • a cathode-ray tube comprising an evacuated envelop and an electron gun adapted to direct a beam of electrons against a target area within said envelop, said beam being deflectable to fall on any portion thereof, a.
  • target structure positioned within said target area and comprising an electron lens structure comprising a pair of spaced parallel grids, each grid comprising a multiplicity of parallel linear conductors, the conductors of the two grids extending in mutually perpendicular directions, connections for establishing different electrical potentials on said grids, a curved display screen mounted closely adjacent to the one of said grids more distant from said electron gun and a coating on said screen of light emissive phosphors, the curvature of said screen being substantially such that said phosphor coating lies on a surface defined by the foci of the electron lenses formed by said grids with respect to electrons from said gun when directed to the various areas of said electron lens structure.
  • a target structure mounted within said area comprising a first grid and a second grid mounted in substantially parallel planes separated by a distance D, each of said grids comprising a multiplicity of substantially parallel linear conductors and the conductors of said second grid extending in a direction substantially normal to that of the conductors of said first grid, connections for applying diiferent voltages between said cathode and said first grid and said first and second grids, a curved display screen mounted closely adjacent to said second grid, and a coating of phosphors emissive of light on electron impact deposited on said display screen, the curvature of said display screen being such that its distance F from the plane of said second grid bears to the distance D the ratio 2 /I+K see? 0 1+tan a tan 5 K sec. 6 1+K sec. 0

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US428622A 1954-05-10 1954-05-10 Target structure for color television display tubes Expired - Lifetime US2801355A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
NL105209D NL105209C (cs) 1954-05-10
BE538028D BE538028A (cs) 1954-05-10
NL197037D NL197037A (cs) 1954-05-10
US428622A US2801355A (en) 1954-05-10 1954-05-10 Target structure for color television display tubes
DEC11190A DE1015842B (de) 1954-05-10 1955-05-07 Elektronenstrahlroehre zur Wiedergabe von Farbfernsehbildern
FR1123938D FR1123938A (fr) 1954-05-10 1955-05-10 Tube cathodique pour la reproduction d'images de télévision en couleurs
CH332357D CH332357A (de) 1954-05-10 1955-05-10 Vorrichtung mit einer Elektronenstrahlröhre zur Wiedergabe von Farbfernsehbildern
GB13518/55A GB787409A (en) 1954-05-10 1955-05-10 Improvements in or relating to cathode-ray tubes for the reproduction of colour television images

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US428622A US2801355A (en) 1954-05-10 1954-05-10 Target structure for color television display tubes

Publications (1)

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US2801355A true US2801355A (en) 1957-07-30

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US428622A Expired - Lifetime US2801355A (en) 1954-05-10 1954-05-10 Target structure for color television display tubes

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US (1) US2801355A (cs)
BE (1) BE538028A (cs)
CH (1) CH332357A (cs)
DE (1) DE1015842B (cs)
FR (1) FR1123938A (cs)
GB (1) GB787409A (cs)
NL (2) NL197037A (cs)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2937297A (en) * 1957-08-05 1960-05-17 Sylvania Electric Prod Image display device
US3043975A (en) * 1957-08-05 1962-07-10 Sylvania Electric Prod Image display device
US3060426A (en) * 1957-11-07 1962-10-23 Thompson Ramo Wooldridge Inc Display apparatus
US3219225A (en) * 1963-05-21 1965-11-23 Mcdowell Mfg Co Multi-part cathode-ray cone
US20110001057A1 (en) * 2009-07-01 2011-01-06 Sge Analytical Sciences Pty Ltd Component for manipulating a stream of charged particles
US20110001056A1 (en) * 2009-07-01 2011-01-06 Sge Analytical Sciences Pty Ltd Component for manipulating a stream of charged particles
US20110179743A1 (en) * 2010-01-28 2011-07-28 Custom Building Products, Inc. Rapid curing water resistant composition for grouts, fillers and thick coatings

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1270077B (de) * 1966-11-10 1968-06-12 Werk Fernsehelektronik Veb Verfahren zur Vermeidung von Farbfehlern bei Farbfernsehbildroehren

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2606246A (en) * 1947-11-28 1952-08-05 Rca Corp Color television system
USRE23672E (en) * 1946-11-16 1953-06-23 Television tube
US2669675A (en) * 1952-01-08 1954-02-16 Chromatic Television Lab Inc Display surface for color television tubes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE23672E (en) * 1946-11-16 1953-06-23 Television tube
US2606246A (en) * 1947-11-28 1952-08-05 Rca Corp Color television system
US2669675A (en) * 1952-01-08 1954-02-16 Chromatic Television Lab Inc Display surface for color television tubes

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2937297A (en) * 1957-08-05 1960-05-17 Sylvania Electric Prod Image display device
US3043975A (en) * 1957-08-05 1962-07-10 Sylvania Electric Prod Image display device
US3060426A (en) * 1957-11-07 1962-10-23 Thompson Ramo Wooldridge Inc Display apparatus
US3219225A (en) * 1963-05-21 1965-11-23 Mcdowell Mfg Co Multi-part cathode-ray cone
US20110001057A1 (en) * 2009-07-01 2011-01-06 Sge Analytical Sciences Pty Ltd Component for manipulating a stream of charged particles
US20110001056A1 (en) * 2009-07-01 2011-01-06 Sge Analytical Sciences Pty Ltd Component for manipulating a stream of charged particles
US20110179743A1 (en) * 2010-01-28 2011-07-28 Custom Building Products, Inc. Rapid curing water resistant composition for grouts, fillers and thick coatings

Also Published As

Publication number Publication date
NL105209C (cs)
NL197037A (cs)
CH332357A (de) 1958-08-31
BE538028A (cs)
GB787409A (en) 1957-12-11
DE1015842B (de) 1957-09-19
FR1123938A (fr) 1956-10-01

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