US2825845A - Cathode ray tube for reproducing color television images - Google Patents

Cathode ray tube for reproducing color television images Download PDF

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Publication number
US2825845A
US2825845A US498676A US49867655A US2825845A US 2825845 A US2825845 A US 2825845A US 498676 A US498676 A US 498676A US 49867655 A US49867655 A US 49867655A US 2825845 A US2825845 A US 2825845A
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Prior art keywords
guns
electron
lens
gun
screen
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Expired - Lifetime
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US498676A
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English (en)
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Jonker Johan Lodewijk Hendrik
Francken Jan Carel
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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    • 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
    • H01J29/48—Electron guns
    • H01J29/51—Arrangements for controlling convergence of a plurality of beams by means of electric field only
    • 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

Definitions

  • CATHODE RAY TUBE FOR REPRODUCING COLOR TELEVISION IMAGES Filed April 1, 1955 2 SheetsSheet 2 INVENTOR JOHAN LODEWIJK HENDRIX JONKER 55.5 JAN CAREL FRANCKEN BY fl fiW AGENT luminesce in diflerent colors. stances or phosphors are arranged in a predetermined 2,825,845 CATHODE RAY TUBE FOR REPRODUCING COLOR TELEVISION IMAGES Johan Lodewijk Hendrik .lonker and Jan Carel Francken,
  • the invention relates to cathode-ray tubes and systems for reproducing color television images and, in particular, to cathode-ray tubes of the multi-gun type.
  • One popular cathode-ray tube of the foregoing type comprises three electron guns by means of which three concentrated electron beams can be directed to an image screen containing three luminescent substances which The luminescent submanner, and during operation of the tube are each excited by a beam of only one electron gun.
  • An input signal is supplied to the control grid of each electron gun, .which comprises at least a cathode, a control grid, and
  • the definition for visual observation it has been found to be preferable for the definition to be determined by means of the green image. This is easy to understand since the human eye has the highest resolving power in the green part of the spectrum. However, if desired, the definition might just as conveniently be determined by one of the other colors. Although not described, it is obvious that what has been mentioned hereinbefore with respect to the bandwidth also applies if use is made of only two or of more than three electron guns and of a corresponding number of primary colors.
  • the cathode-ray tube according to the invention comprising an image screen and at least two electron guns, each of which comprises at least a cathode, a control-grid, an anode and a second concentrating electron lens, is characterized by a gun structure in which the gun to which the signal having the largest bandwidth is supplied exhibits a ratio between the relative spacing of the second electron lens and the image screen and the relative spacing of the second lens and the cross-over point which is less than the same ratio in the other electron guns.
  • the gun structure in which the gun to which the signal having the largest bandwidth is supplied exhibits a ratio between the relative spacing of the second electron lens and the image screen and the relative spacing of the second lens and the cross-over point which is less than the same ratio in the other electron guns.
  • the second electron lens of the gun to which the largest bandwidth signal is applied is closer to the image screen than are the second electron lenses of the other-guns.
  • the invention is based upon the fact that the size of the picture elements on the image screen decreases with a decrease in the ratio between the relative spacing of the second electron lens and the image screen and the relative spacing of the lens and the beam node or cross-over. Consequently, the gun to which the signal having the largest bandwidth is supplied in a tube in accordance with the invention and thus having the smallest ratio, will produce the smallest picture elements on the image screen. As indicated hereinbefore, the colorproducing-component of the screen excited by this gun preferably produces a green image. The size of these picture elements and consequently the absolute values of the two spacings are made such that the image has the required definition. With respect to the other guns, one distance or both distances are made difierent with the result that certain structural advantages are obtained, as will be set out more fully hereinafter.
  • the distances by which the second electron lenses and the image screen are spaced apart can be made equal ,for all the guns, so that the distance by which the electron lens and the cross-over are spaced apart is smaller for the guns to which the signals having the smaller bandwidth are supplied than for the gun having the signal of larger bandwidth supplied to it.
  • the length of these guns will be reduced with a resultant considerable saving in material, while more space will become available in the cathode-ray tube.
  • the second electron lenses of the various guns may be arranged so as to be spaced away from the image screen by various distances.
  • the electron lenses operate electrostatically or electromagnetically, they substantially always comprise components the diameter of which exceeds that of their anodes. Since the distance by which they are spaced away from the image screen is different, the axes of the electron guns can, it the differences are properly chosen, be arranged in closer proximity to each other than if the electron lenses were equidistant from the image screen and the broad parts of the lenses were arranged side by side.
  • the object distance and consequently the length of the gun can be varied subject to the condition that in the gun to which the signal having the largest bandwidth is supplied, the ratio between the image distance and the object distance is less than the corresponding ratio of the other guns.
  • a very simple construction of a tube containing three guns is obtained if the axes of the guns are parallel and the second electron lens of the central gun is nearer the image screen.
  • the lengths of the two outer guns may be made equal, and the central gun maybe made such that the cathodes of they three guns are equidistant from the image screen.
  • the lengths of the three guns might be made equal, since in ⁇ this case due to the smaller image distance of the lens ,of the central gun, :the requirement is fulfilled that this gun has the. smallest-magnification.
  • the axes of the guns will preferably be arranged at an angle toeach other such that the electron beams meet in-a point at the image screen. In .this event, no additional fields are required to converge the initially-parallel electron .heams.
  • Fig. 1 shows diagrammatically the construction of one form of cathode-raytube according to the inventioncomprising threeelectron guns, the axes of which are parallel .and lie in .one plane;
  • Fig. 2. shows the neck of another form of cathode-ray tube in accordance with the invention comprising three electron guns arranged at an angle to each other such ,that their axes meet in a point at the image screen;
  • Fig. v3 shows the neck ofstill another form of cathoderay tube in accordance with the invention comprising ethreeelectron guns, theaxes of which form the edges of a right equilateral prism;
  • FIG. 4 is a side view .of a tube shown in Fig. "3;
  • FIG. 5 shows the neck of another form of cathoderay tube in accordance with the invention comprising three electron guns the axes of which are parallel andlie ,in one plane, the lengths of the electron guns varying from one gun ,to another.
  • the cathode-ray tube shown consists of ;a cylindrical neck' portion 1 and a mating conical part 2 closed off by a transparent window 3.
  • This window supports an electron-receiving, luminescent or fluorescent screen 4,
  • three electron guns are arranged, in which .the two outer electron guns are identical. Therefore only one of these guns will be provided with reference numerals.
  • These two guns comprise a cathode 5,.a diaphragm 6 acting as a control-grid, an'accelerating orfirstanode 7, another-anode 8, .an additional electrode 59 and a final electrode '10.
  • the electrodes 8, 9 and 10 constitute a so-called unipotential lens, since the electrodes Sand 10 are directly interconnected electrically and are thus at the same potential.
  • the electrode 9 has a potential applied to it which is lower than thepotentia-l applied to the electrodes 3 and It).
  • the central electron gun comprises a cathode 14,2.
  • the unipotential lens constituted by the electrodes 17, 18 and 1 9 is arranged nearer the image screen 5%. Consequently, for this lens, the ratio between the distan in h chis s a e qm h ho c h ima scr en 4 a d th istance b wh it i a d t ots th crossover produced approximately in the aperture of the di ph m .1 s e than he r ondin ti f t lenses of the two remaining electron guns.
  • the cenneck of the kind 4 tral gun is the gun to which during operation the signals having the largest bandwidth are supplied.
  • This is illustrated in Fig. 1 by showing three signal sources 61, 62 and 63 coupled each to the control electrode of one of the three guns.
  • the sources 61 and 62 which are coupled to the outer two guns, produce color signals of smaller bandwidth A for driving the outer two guns.
  • the third source 63 which produces a color signal of larger bandwidth A-l-AA, is coupled to the center gun whose ratio of second lens to screen distance and second lens to crossover distance is smaller than the corresponding ratio for the outer'two guns.
  • the three electron beams are deflected with theaid of deflector coils 20 and 21 and of two additional coils ensuring the deflection in the plane of thedr-awing (not shown).
  • deflector coils 20 and 21 Between the electron guns and the ,deflector .coils a field is produced such that-the electron beams meet in a point 12 .of the image screen 4. 'For'the sakeof clearness, this field which is not important for an'u'nderstanding of the invention is not shown. "However, many constructions of electrode systems which operate electromagnetically and/or electrostaticallyhave been described for bringing together the three electron beams. As will be seen from the drawing,
  • the two outer guns are considerably'shorter than the central electron gun. Compared with a tube of known construction, it should .be noted that the length of the expansivelectron gun is the same as the guns proposed for 'these known tubes. However, the outer guns are considerably shorter than the corresponding guns of these known .tubes.
  • a neck 22 of a tube contains three electron guns arranged at an angle to each other such that their axes meet in a point of the image screen (not shown). Only the anodes and the ,unipotential second lenses of these guns are shown. As will be seen from the drawing, the three lenses of the guns comprise the additional electrodes 23, 24 and 25, the widths of which considerably exceed that of the anodes 26, 27 and 28. Since the lens of the central gun is arranged nearer the image screen, the outer electron guns may be arranged such that the projections of the electrodes 23, 24 and 25 on to a plane at right angles to the tubes axis 2929 overlap each other.
  • Fig. 3 shows a further modification comprising three electron guns the axes of which constitute the edges of a right equilateral prism.
  • the electron .beams are deflected, similarly to those in the embodiment shown in Fig. 1, 'bymeans of a special field so that they meet ina point of the collecting screen.
  • the electron guns shown diagrammatically by rectangles 30, 31 and 32 are accommodated in separate tubes 33, 34 and 35.
  • the second electron lenses operate electromagneticallyand consist of'coils 36, 37 and 38.
  • the electron gun 3t) and the coil 36 constitute the system to which the signal having the largest bandwidth is supplied. As may be seen more clearly from the side elevation shown in Fig.
  • the axes of the electron guns form the edges of a right equilateral prism and are arranged in closer proximity to each other than the sum of the radii of the circumferences of the coils, which is possible .by means of the fact that the coils are staggered in the direction of their length.
  • Fig. 4 which is a projection on to :a plane at right angles to the tube axis, the coils therefore partially overlap.
  • Such an arrangement can also be used if use is made of electrostatic focussing by means of widened cylinders, as is shown in Fig. 2.
  • the image screen 4 (not shown) is to the left of the figure.
  • Fig. 5 shows the neck of a further cathode-ray tube in accordance with the invention comprising three electron guns the lenses of which are of different construction.
  • the axes of the guns are parallel and lie in one plane and the lengths of the guns are difierent similarly to the embodiment shown in Fig. 1.
  • the second electron lenses of the outer guns consist of electrodes 39, 40 and 41, and 42, 43 and 44, respectively.
  • the second electron lens of the central gun comprises electrodes 45, 46 and 47. As will be seen, the width of the electrode 46 exceeds that of the anode 45 of the central gun. This results in a better lens.
  • the lenses are arranged so as to be staggered, the axes of the guns may be nearer each other than the sum of the radii of the electrodes 41 and 46 or 44 and 46 respectively.
  • additional deflector electrodes 48 and 49 and 50 and 51, respectively, for the outer guns are arranged at the level of the second electron lens of the central gun. With the aid of these sets of deflector electrodes, the two outer electron beams can be converged to the point at which the central electron beam strikes the image screen.
  • the crossover was formed approximately at the aperture in the control grids 6 and 15.
  • the thin lens constituted by electrodes 8, 9 and 10 of the outer guns was spaced about 60 mms. from the crossover, and about 497 mms. from the screen 4. Therefore, the ratio was 60
  • the thin lens constituted by electrodes 17, 18 and 19 was spaced about 87 mms. from the crossover, and about 470 mms. from the screen.
  • a system for reproducing color television images comprising a cathode-ray tube, said tube including an electron-receiving screen and a plurality of electron guns, each of said guns including a cathode, a control grid and an anode and producing an electron beam having a crossover point, and a plurality of second electron lenses each associated with one of said electron guns, the second lens associated with one of said guns being positioned so that said one gun exhibits a smaller ratio of lens to screen distance and lens to crossover distance than that exhibited by the other guns, a source of color signals including at least two separate signals of which one has a larger bandwidth than the other, and means for applying the signal of larger bandwidth to said one gun.
  • a system for reproducing color television images comprising a cathode-ray tube, said tube including an electron-receiving screen and a plurality of electron guns, each of said guns including a cathode, a control grid and an anode and producing an electron beam having a crossover point, and a plurality of second electron lenses each associated with one of said electron guns, the second lens associated with one of said guns being closer to the electron-receiving screen than the second lenses of the other guns so that said one gun exhibits a smaller ratio of lens to screen distance and lens to crossover distance than that exhibited by the other guns, a source of color signals including at least two separate signals of which one has a larger bandwidth than the other, and means for applying the signal of larger bandwith to said one gun.
  • the second electron lenses each contain one electrode whose diameter is greater than another of its electrodes, said one electrode having a diameter at which a projection thereof on to a plane at right angles to the tube axis will produce partially overlapped images.
  • a system for reproducing color television images comprising a cathode-ray tube, said tube including a fluorescent screen containing a plurality of color-producing-components and a plurality ofi electron guns each producing an electron beam adapted to cooperate with one of said color-producing-components of said fluorescent screen, each of said guns including a first immersion lens producing a crossover point of said electron beam and a second electron lens adapted to project said crossover point onto said fluorescent screen, the ratio of the spacings between said second lens and said screen and said second lens and said crossover point for one of said guns being smaller than the corresponding ratio for the other guns, a source of color signals including a signal of larger bandwidth and another signal of smaller bandwidth, and means coupling said signal of larger bandwidth to said one gun and said signal of smaller bandwidth to another of said guns.
  • a cathode-ray tube for reproducing color television images comprising an image screen having difierent, color-producing, electron-responsive areas, at least two electron guns each including an electron lens for producing two electron beams directed at the screen, the lenses of the two guns having difierent ratios of image-to object spacings with respect to the whole of the screen, said guns producing differently-sized picture elements over said screen, and means for coupling to said guns color signals possessing different bandwidth characteristics.

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  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
US498676A 1954-04-03 1955-04-01 Cathode ray tube for reproducing color television images Expired - Lifetime US2825845A (en)

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NL329957X 1954-04-03

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US (1) US2825845A (en(2012))
BE (1) BE537063A (en(2012))
CH (1) CH329957A (en(2012))
DE (1) DE948616C (en(2012))
FR (1) FR1129948A (en(2012))
GB (1) GB783305A (en(2012))
NL (1) NL186490B (en(2012))

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2915671A (en) * 1955-04-29 1959-12-01 Emi Ltd Plural beam cathode ray tubes
US3571643A (en) * 1967-09-20 1971-03-23 Sony Corp Plural beam electron gun for a color picture tube with different-sized control grid apertures
US3755703A (en) * 1968-04-14 1973-08-28 Sony Corp Electron gun device for color tube
US4331904A (en) * 1979-03-20 1982-05-25 U.S. Philips Corporation Color television display tube

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2459790A (en) * 1945-09-05 1949-01-25 Standard Telephones Cables Ltd Indicating cathode-ray tube
US2549072A (en) * 1946-02-27 1951-04-17 Rca Corp Recording apparatus for radar systems
US2570858A (en) * 1949-02-26 1951-10-09 Rca Corp Frequency analyzer
US2728025A (en) * 1951-05-17 1955-12-20 Rca Corp Post-deflected cathode-ray tubes
US2728872A (en) * 1953-10-23 1955-12-27 Hughes Aircraft Co Direct-viewing storage tube with character writing electron gun

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2459790A (en) * 1945-09-05 1949-01-25 Standard Telephones Cables Ltd Indicating cathode-ray tube
US2549072A (en) * 1946-02-27 1951-04-17 Rca Corp Recording apparatus for radar systems
US2570858A (en) * 1949-02-26 1951-10-09 Rca Corp Frequency analyzer
US2728025A (en) * 1951-05-17 1955-12-20 Rca Corp Post-deflected cathode-ray tubes
US2728872A (en) * 1953-10-23 1955-12-27 Hughes Aircraft Co Direct-viewing storage tube with character writing electron gun

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2915671A (en) * 1955-04-29 1959-12-01 Emi Ltd Plural beam cathode ray tubes
US3571643A (en) * 1967-09-20 1971-03-23 Sony Corp Plural beam electron gun for a color picture tube with different-sized control grid apertures
US3755703A (en) * 1968-04-14 1973-08-28 Sony Corp Electron gun device for color tube
US4331904A (en) * 1979-03-20 1982-05-25 U.S. Philips Corporation Color television display tube

Also Published As

Publication number Publication date
GB783305A (en) 1957-09-18
BE537063A (en(2012))
NL186490B (nl)
DE948616C (de) 1956-09-06
FR1129948A (fr) 1957-01-29
CH329957A (de) 1958-05-15

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