US2825847A - Cathode-ray tube for the reproduction of colour television images - Google Patents

Cathode-ray tube for the reproduction of colour television images Download PDF

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Publication number
US2825847A
US2825847A US581109A US58110956A US2825847A US 2825847 A US2825847 A US 2825847A US 581109 A US581109 A US 581109A US 58110956 A US58110956 A US 58110956A US 2825847 A US2825847 A US 2825847A
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United States
Prior art keywords
cathode
guns
image
gun
electron
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Expired - Lifetime
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US581109A
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English (en)
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Gier Johannes De
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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
    • 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

  • a cathoderay tube having three electron guns by means of which three concentrated electron beams can be directed to an image screen containing three luminescent substances emitting light of different colours, which substances are arranged uniformly in discrete surfaces and, .in the operation of the tube, can each be excited by a beam from a single electron gun.
  • a predetermined signal is supplied to each of the guns.
  • the use of the difierent bandwidth was discovered in the search for a composite television signal which is suitable for wireless transmission and does not have an excessively large over all bandwidth, preferably a bandwidth not exceeding that of a signal .of the kind used in black-and-white television.
  • a cathode-ray tube in accordance with the invention for the reproduction of coloured television images comprises an image screen provided with at least two luminescent materials, which, on electron bombardment, emit light of difierent colours and with difierent efficiency and are arranged in discrete uniformly distributed surfaces, and at least two electron guns, which each comprise at least a cathode, a control grid and an anode and which generate electron beams which each pass through a principal or main focus'sing lens having the same image atent O 2,825,847 .”Patented Mar.
  • thecontrol electrode of the gun which cooperates with a luminescent material of higher efliciency having a signal supplied to it which has a greater bandwidth than the signal-supplied to the control electrode of the gun'co-operating-with a luminescent material of lower efficiency.
  • the geometry of the tube is such that the spot size of the gun co-operating with luminescent material of higher efficiency at a predetermined current strength and with maximum focusing by the principal lens is smaller than that of the gun cooperating with a luminescent material of lower efiiciency, when compared under conditions of the same current strength and with maximum focusing.
  • image ratio of the principal lens is to be understood to mean the ratiobetween'the distance by which the infinitely thin lens, which with respect to its efiect may replace the principal lens, is spaced away from the image screen and the distance by which it is spaced away from the control electrode.
  • This image ratio is analogous to the image ratio of an optical lens.
  • the object an image of whichfis produced electron-optically, is the cross-over produced in close proximity to the control electrode.
  • a larger beam spot on the image screen means that the cross-over also is larger, for the cross-over is the object of whichan image is produced by the principal lens.
  • a larger cross-over means a smaller specific cathode load, i. e. the current persq. cm. of the operative cathode surface.
  • the luminescent material with which the gun for the greater bandwidth co-operates requires acertain current strength to produce a predetermined amount of light.
  • a greater current strength in the electron beam is necessary. If the size of the beam spot on this luminescent material were made equal to that on the luminescent material of higher efiiciency, there would be, for a cross-over of equal surface area, a greater current strength, and this means that the specific cathode load of the gun producing this cross over is greater.
  • the life of the lastmentioned cathode would be shorter than that of the first-mentioned cathode. It is obvious that this is very inconvenient, since the guns and consequently the cathodes are arranged in one tube and hence failure of on'e cathode necessitates replacement of the tube or viewing pictures in unnatural colours henceforth- However, as has been described hereinbefor'e, it is not necessary that the definition of all the images be equal and hence when the higher definition is produced in the screen of the highest efiiciency, the spot on the screen material of smaller efficiency can be made larger.
  • the size of the cross-over is also dependent upon the value of the current in the electron beam, any comparison of beam spot sizes must obviously be made with the same current strength.
  • the current in the electron beam produced by the gun which co-operates with the luminescent material of lower efliciency will exceed the current in the beam of the gun which co-operates with the luminescent material of higher efiiciency.
  • a larger cross-over and consequently a larger spot can, for example, be obtained by a larger aperture of passage in the control electrode and by a larger spacing between the cathode and the control electrode. Consequently, variations in the geometry of the electron gun permit of obtaining a predetermined size of the cross-over and consequently of the spot on the image screen, at a given current strength.
  • a larger aperture of passage of a control electrode results in the reduction of the so-called cut-01f voltage, i. e. the voltage of the control electrode at which the electron beam current is reduced to zero.
  • cut-01f voltage i. e. the voltage of the control electrode at which the electron beam current is reduced to zero.
  • a mask electrode which ensures that electrons from one gun can exciteluminescent material only which emits light of one colour.
  • the electron beams may be additionally concentrated in known manner between the mask and the image screen. In this embodiment, the spot size must be measured at the mask.
  • the electron beams produced by the guns can be passed through a common principal lens. By ensuring that in all the guns the cathode is spaced away from the principal lens by the same distance, it can be ensured that the image ratio is the same for all the guns.
  • a cathode-ray tube for visual observation in which use is made of 3 luminescent materials, which emit green, red and blue light respectively.
  • luminescent materials use was made for the green image of willemite, for the red image of zinc beryllium silicate activated with manganese, and for the blue image of calcium magnesium silicate activated with titanium. Of the said three substances, the willemite has the highest efiiciency. Since the tube is to be used for visual observation, it is of advantage to determine the definition by the green image. Consequently, the spot on the material luminescent in green must be smallest. Since, in measuring, a raster was traced out, the line width was measured instead of the spot size, which amounts to the same thing.
  • the diameter of the area of passage of the control electrode was 0.5 mm. in the electron gun for the green image and 0.6 mm. in the two other electron guns.
  • the cut-oif voltages were equal for all the three guns, i. e. 60 volts.
  • the spacing between the control electrode and the cathode was 0.2 mm. and in the two other guns 0.25 mm.
  • the thickness of the control electrode and the spacings between the said electrode and the screen were equal in all the electrode systems.
  • 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 a luminescent screen 4 containing three luminescent materials,- luminescing in three primary colors, arranged in a repetitive pattern.
  • three electron guns are arranged, in which the two outer electron guns are identical.
  • These two guns comprise a cathode 5, a diaphragm 6 acting as a control grid, an accelerating or first anode 7 and a final anode 8. Due to the cooperation of the electrodes 5, 6 and .7, which serve as an immersion or first lens, a cross-over is produced approximately in the aperture of the control grid 6.
  • This node is projected onto the luminescent screen 4 by means of a second electron lens formed by a focussing coil 9, which lens is called the main or principal lens.
  • This main lens is as may be seen common to the cathode-rays produced by the three guns. Apart from focussing each electron beam, this main lens at the same time converges the three beams to a'common point 15 of the image screen 4. Between the main lens formed by the coil 9 and the screen the three electron beams are deflected with the aid of defleeting coils 13 and 14.
  • the central gun is of a construction which is for the greater part similar to the construction of the two outer guns.
  • the aperture or passage in the control grid 6 is smaller than the corresponding apertures in the control grids of the two outer guns.
  • the distance between the cathode and the control-grid is smaller for the central gun than for the two outer guns.
  • three signal sources are provided for applying signals of bandwidth A and a signal of larger bandwidth A-l-AA to the control grids 6 of the three guns for modulating their beam current.
  • the signal with the greater bandwidth A+AA is applied to the central gun.
  • This central gun which produces a smaller beam spot, co-operates with the luminescent material of higher efficiency on the screen 4.
  • a cathode-ray tube comprising an image screen containing plural luminescent materials possessing higher and lower efiiciencies and luminescing in plural colors to form a composite color image, and a plurality of electron guns each producing an electron beam for exciting one of Sa d luminescent materials, said gun exciting the higheraeaasw efficiency luminescent material producing a smaller beam spot size in the vicinity of the screen than that of the other guns, when compared under conditions of the same beam current and the same beam focnssing;
  • each of the guns includes a cathode and an apertured control grid, the control grid of the gun exciting the higher-emciency luminescent material having a smaller aperture than that of the control grids of the other guns.
  • each of the guns includes a cathode and an apertured control grid, the spacing between the cathode and the control grid of the gun exciting the higher-efficiency luminescent material being smaller than that of the other guns.
  • Cathode-ray tube apparatus comprising: a cathoderay tube having an image screen containing plural luminescent materials possessing higher and lower efficiencies and luminescing in plural colors to form a composite color image, and a plurality of electron guns each including cathode and apertured control grid electrodes and each producing an electron beam for exciting one of said luminescent materials; and a principal lens associated with the guns and having the same image ratio for each of the guns for focussing the beams onto the image screen; said gun exciting said higher-efliciency luminescent material producing a smaller beam spot size in the vicinity of the screen than that of the other guns, when compared under conditions of equal beam current and maximum focussing by the principal lens.
  • Cathode-ray tube apparatus comprising: a cathoderay tube having an image screen containing plural luminescent materials possessing higher and lower eficiencies and luminescing in plural colors to form a composite color image, and a plurality of electron guns each including cathode and apertured control grid electrodes and each producing an electron beam for exciting one of said luminescent materials; a principal lens associated with the guns and having the same image ratio for each of the guns for focussing the beams onto the image screen; said gun exciting said higher-efiiciency luminescent material producing a smaller beam spot size in the vicinity of the screen than that of the other guns, when compared under conditions of equal beam current and maximum focussing by the principal lens; plural signal sources generating signals of larger and smaller bandwidth; and means for applying the larger bandwidth signal to the gun exciting the higherefliciency material and the signals of smaller bandwidth to the other guns.

Landscapes

  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US581109A 1955-05-12 1956-04-27 Cathode-ray tube for the reproduction of colour television images Expired - Lifetime US2825847A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL791486X 1955-05-12

Publications (1)

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US2825847A true US2825847A (en) 1958-03-04

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US581109A Expired - Lifetime US2825847A (en) 1955-05-12 1956-04-27 Cathode-ray tube for the reproduction of colour television images

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US (1) US2825847A (enrdf_load_stackoverflow)
BE (1) BE547784A (enrdf_load_stackoverflow)
DE (1) DE1009227B (enrdf_load_stackoverflow)
FR (1) FR1153894A (enrdf_load_stackoverflow)
GB (1) GB791486A (enrdf_load_stackoverflow)
NL (1) NL197194A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3393336A (en) * 1965-05-20 1968-07-16 Cft Comp Fse Television Three gun color tube with central gun of smaller cross-section than lateral guns
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
US3619686A (en) * 1969-03-07 1971-11-09 Sony Corp Color cathode-ray tube with in-line plural electron sources and central section of common grid protruding toward central source
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 (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2672574A (en) * 1952-03-19 1954-03-16 Rca Corp Magnetic beam controlling system
US2679614A (en) * 1952-09-17 1954-05-25 Rca Corp Beam-controlling system for tricolor kinescopes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2672574A (en) * 1952-03-19 1954-03-16 Rca Corp Magnetic beam controlling system
US2679614A (en) * 1952-09-17 1954-05-25 Rca Corp Beam-controlling system for tricolor kinescopes

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3393336A (en) * 1965-05-20 1968-07-16 Cft Comp Fse Television Three gun color tube with central gun of smaller cross-section than lateral guns
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
US3619686A (en) * 1969-03-07 1971-11-09 Sony Corp Color cathode-ray tube with in-line plural electron sources and central section of common grid protruding toward central source
US4331904A (en) * 1979-03-20 1982-05-25 U.S. Philips Corporation Color television display tube

Also Published As

Publication number Publication date
NL197194A (enrdf_load_stackoverflow)
FR1153894A (fr) 1958-03-28
GB791486A (en) 1958-03-05
DE1009227B (de) 1957-05-29
BE547784A (enrdf_load_stackoverflow)

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