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EP0418962A1 - Dispositif de reproduction d'images et tube à rayons cathodiques - Google Patents

Dispositif de reproduction d'images et tube à rayons cathodiques Download PDF

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Publication number
EP0418962A1
EP0418962A1 EP90202446A EP90202446A EP0418962A1 EP 0418962 A1 EP0418962 A1 EP 0418962A1 EP 90202446 A EP90202446 A EP 90202446A EP 90202446 A EP90202446 A EP 90202446A EP 0418962 A1 EP0418962 A1 EP 0418962A1
Authority
EP
European Patent Office
Prior art keywords
electron beams
display device
electrodes
emission means
deflection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90202446A
Other languages
German (de)
English (en)
Inventor
Frederik Christiaan Gehring
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0418962A1 publication Critical patent/EP0418962A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
    • H01J31/123—Flat display tubes
    • H01J31/124—Flat display tubes using electron beam scanning

Definitions

  • the invention relates to a display device comprising a cathode-ray tube having a display screen, emission means for generating a row of electron beams which are arranged at one side of said display screen, the emission means having an emitting element for each electron beam and each electron beam scanning a column of picture elements of the display screen, and deflection means for deflecting the electron beams towards the display screen.
  • the invention also relates to a cathode-ray tube which is suitable for use in a display device.
  • a display device of the type described in the first paragraph is known from European Patent Application 0 288 095.
  • the emission means comprise one (semiconductor) cathode for each electron beam.
  • the electron beams are emitted at least substantially parallel to the display screen.
  • a colour selection electrode is located in front of the display screen.
  • a series of deflection strips is provided on a wall which extends parallel to the colour selection electrode.
  • the electron beams are located between the deflection strips and the colour selection electrode.
  • One of the objects of the invention is to provide a display device of the type mentioned in the opening paragraph, in which the influence of magnetic fields on the paths of the electron beams is reduced. This enables an omission, a reduction in size or a simpler or lighter construction of the magnetic screen.
  • the display device is characterized in that the deflection means comprise a first and a second electrode which are arranged so as to extend at least substantially parallel to each other and between which there is a deflection space, the display device having means to apply a potential difference to these electrodes, and the emission means being suitable for making the electron beams enter the deflection space at an acute angle with the parallel electrodes.
  • the influence of magnetic fields on the paths of the electron beams is reduced substantially, and can be readily compensated in some cases, by virtue of the symmetry of the parabolic paths travelled by the electron beams in the deflection space.
  • An embodiment of a display device in which the display device comprises a colour selection electrode extending in front of the display screen, is characterized in that one of the said electrodes comprises the colour selection electrode, the emission means are suitable for emitting a row of fans of electron beams, and the said angle is approximately 45 o .
  • a further embodiment of the display device according to the invention is characterized in that emission means are constructed such that the angles at which the electron beams in the fans enter the deflection space are symmetrical relative to an angle of 45 o .
  • a still further embodiment of the display device according to the invention is characterized in that the emission means are suitable for simultaneously generating at least two of the electron beams which form a fan.
  • a colour image may be composed of successive images in the primary colours or of simultaneous images.
  • the electron beams forming the fan can be generated successively or simultaneously.
  • the simultaneous display of images in the primary colours has the advantage that lower frequencies can be used for driving the emission means and/or applying the potential difference to the electrodes.
  • the display device according to the invention is very suitable for this purpose because the differences between the kinetic energy levels need only be small.
  • the emission means are suitable for the simultaneous emission of all the electron beams forming a fan.
  • a still further embodiment of the display device according to the invention is characterized in that the emission means are suitable for generating electron beams, the energy levels of which differ so much from each other that at a specific potential difference between the said electrodes the electron beams intersect in the plane of the colour selection electrode.
  • Yet another embodiment of the display device according to the invention is characterized in that the emission means comprise deflection electrodes.
  • the deflection electrodes permit the angle at which an electron beam enters the deflection space and the energy of the electron beam to be influenced in a simple manner.
  • a further embodiment of the display device according to the invention is characterized in that the electrodes are approximately rectangularly shaped and the interspace between the electrodes is more than 1/4 times the length of the electrodes viewed in the direction of travel of the electron beams.
  • the distance between the electrodes is less than 0.40 times the length of the electrodes viewed in the direction of travel of the electron beams.
  • the length of the electrodes viewed in the direction of travel of the electron beams is smaller than the length viewed in a direction transversely to the said direction.
  • a still further preferred embodiment of the display device according to the invention is characterized in that the quotient of the length of the electrodes in the direction of travel of the electron beams and the length of the electrodes in a direction transversely to the said direction is smaller than 3 : 4.
  • Yet another embodiment of the display device according to the invention is characterized in that the said quotient is approximately 9 : 16.
  • FIG. 1 is a sectional view of the known display device.
  • a colour display device 1 comprises a cathode-ray tube 2 containing an emission means 3 for emitting a row of electron beams 4 in a deflection space 5 between deflection strips 6 and a colour selection electrode 7. For each column of picture elements at least one electron beam is emitted.
  • voltages are applied to the deflection strips, in such a manner that after the electron beams have entered the deflection space 5 they initially trace a straight path which extends parallel to the deflection strips 6 and the colour selection electrode 7.
  • the electron beams are forced to deflect through an angle of 90 o towards the colour selection electrode.
  • Magnetic fields cause deviations in the paths of the electron beams. Said deviations can be reduced at least partly by accommodating the deflection space in a magnetic screen.
  • the colour selection electrode in Fig. 1 forms part of said magnetic screen. A reduction of the influence of the magnetic fields on the paths of the electron beams may permit a simpler or lighter construction of the magnetic screen or even its omission.
  • the present invention provides a display device in which the influence of magnetic fields on the paths of the electron beams is reduced.
  • Fig. 2 is a sectional view of a display device, in the present example a colour display device 20, according to the invention.
  • Said colour display device 20 comprises emission means 23 in an evacuated envelope 22, said emission means being used to generate a row of fans of, in the present example three, electron beams 24, 25 and 26. It is to be noted that said emission means 23 may comprise three different sources for the three electron beams or one common source for the three electron beams.
  • the colour display device 20 further comprises a deflection space 27 between a colour selection electrode 28 and a flat electrode 29. In operation, an electric field E is applied in the deflection space 27 by means of a potential difference between the colour selection electrode 28 and the flat electrode 29.
  • the electron beams 24, 25 and 26 enter the deflection space 27 at an angle with the plane of the colour selection electrode, i.e. at an angle x with the field lines of the electric field E.
  • the electron beams describe parabolic paths.
  • the electron beams 24, 25 and 26 pass through apertures in the colour selection electrode 28, diverge in the space between the colour selection electrode 28 and a display screen 30 and are incident on said display screen 30.
  • the influence of the magnetic fields on the paths of the electron beams is represented by the force F B exerted by the magnetic fields on the electrons in the electron beams.
  • B the magnetic field
  • v the velocity of the electrons
  • X the vector product of B and v.
  • the electrons move in the plane of the drawing. Consequently, the z-­component of the velocity of the electrons, z being the direction perpendicularly to the plane of the drawing, is 0.
  • the x-component of the velocity of the electrons, x being the horizontal direction is a constant v x .
  • the y-component of the velocity of the electrons varies between an initial value v y0 on entering the deflection space, and a final value -v yo .
  • the magnetic field in the deflection space has the components B x , B y and B z in the x, y and z-direction, respectively.
  • the angle at which the electron beams enter the deflection space is approximately 45 o .
  • this angle ⁇ is 45 o .
  • the angle is 45 o - ⁇ and 45 o + ⁇ , respectively.
  • ⁇ is 1/80 radial ( ⁇ 0.7 o ) and ⁇ is S x5 *3.124*10 ⁇ 4.
  • ⁇ is small and not shown in Fig. 4a, yet under certain conditions it is recommendedable to correct this difference.
  • ⁇ varies from approximately 0 ⁇ m at one edge of the display screen to approximately 156 ⁇ m at an opposite edge, which is approximately equal to half the distance between phosphors on the display screen. ⁇ increases according as the dimensions of the display screen increase.
  • the difference ⁇ is smaller if, for example, the electron beams are located at a distance from each other at the location where they enter the deflection space.
  • ⁇ varies across the display screen between approximately -78 ⁇ m and +78 ⁇ m, which leads to an improved image display.
  • the difference ⁇ is smaller, and can even be compensated completely, when the above constant of the electron beams 24 and 26 is a factor of 1+2 ⁇ 2 larger than the constant of the electron beam 25, for example when the kinetic energy E kin of the electron beams 24 and 26 is a factor of 1+2 ⁇ 2 larger or the electric field strength is a factor of 1+2 ⁇ 2 smaller than for electron beam 25.
  • Fig. 4a shows an arrangement in which the electrons follow a straight path between the electrode 28 and the display screen 30. It is alternatively possible to apply a potential difference between the electrode and the display screen, so that the electrons are post-­accelerated after they have passed through the colour selection electrode 28.
  • the advantages of a so-called post-acceleration tube are that only a relatively small voltage has to be applied between the electrodes 28 and 29 and that the heat supply by the electrons to the colour selection electrode is smaller. Consequently deformations of the colour selection electrode caused by temperature difference are less frequent.
  • Fig. 4b shows a detail of such a colour display device. As the electron beams are accelerated they diverge less in the space between the colour selection electrode 28 and the display screen 30 for a given angle ⁇ .
  • the distance between the electron beams on the display screen should, however, be equal to D which is the distance between the phosphors. For this reason, the angle ⁇ between the electron beams is larger, approximately a factor of 3 to 5. As a consequence hereof ⁇ increases by a factor of 10 to 20.
  • FIG. 5 shows an arrangement which enables the energy of the electron beams 24 and 26 to be increased and the angle at which electron beams enter the deflection space to be influenced in a simple manner.
  • An electron gun 40 comprises an electron-emitting element 41, for example a p-n emitter, a system of electrodes 42, 43, 44, 45 and 46 which accelerate, deflect and focus an electron beam 47 emitted by the element 41.
  • an electron beam 47 emerges from an aperture 48 it has a velocity of v0, i.e. an energy E0.
  • deflection electrodes 49 and 50 which are at the same voltage as aperture 48 for a specific period of time. During this time, the electron beam is not deflected by the deflection electrodes.
  • V/V electron ⁇ d/l Consequently it has been found that for a V electron of approximately 2 KeV, a ⁇ of approximately 1/80 radial (0.7 degrees) and a d:l ratio of approximately 1:1 a potential difference between the electrodes 49 and 50 of approximately 25 V is sufficient.
  • ⁇ may have a value of approximately 3 to 5 degrees
  • a potential difference in the order of magnitude of 100 to 200 V is sufficient.
  • a potential difference of approximately 0.3 V (or several V in the case of a post-acceleration tube) can be applied between aperture 48 and the electrodes 49 and 50.
  • the energy of the electrons in the deflected electron beams is again a factor of 1+ ⁇ 2 larger than the energy of the undeflected electron beam, and the electron beams intersect at the location of the colour selection electrode.
  • the emission means are suitable for the simultaneous generation of at least two of the electron beams of the fan.
  • the emission means may comprise, for example, three sources for a fan of three electron beams, for example electron beams 24 and 26 of Fig. 2 being generated simultaneously. Said electron beams intersect at the location of the colour selection electrode 28. This enables at least two of the images in the primary colours to be displayed simultaneously without an energy difference between the electron beams 24 and 26 being necessary. This leads to a reduction of the frequency or frequencies at which the emission means or the electrodes 28 and 29 are driven.
  • all electron beams are generated simultaneously, so that they all pass through the deflection space at the same time.
  • a further simplification of the colour display device can then be achieved. Corrections at the location where the electron beams pass through the colour selection electrode can be achieved, for example, by applying slightly less energy to electron beam 25 relative to the electron beams 24 and 26 or by shifting the location where the electron beam 25 enters the deflection space relative to the location where the electron beams 24 and 26 enter said deflection space.
  • the above described example can be compared to a display device according to the invention in which the angle x is 20 o .
  • Fig. 6 diagrammatically shows the deflection space.
  • Said deflection space is an approximately box-shaped space 60 which is defined by ribs a, b and c.
  • the ribs a and b approximately correspond to the sides of the electrodes 28 and 29 (Fig. 2), rib c corresponds to the distance between the electrodes 28 and 29.
  • electron beams 61 enter the deflection space approximately at the location of rib b and at least substantially parallel to rib a .
  • the lengths of the ribs a and c are in a ratio of 1: x , x being selected so that the length of rib c is somewhat larger than the maximum distance between the base 62 of the box-shaped space 60 and the extremum 63 of an electron path (denoted S y in Fig. 6).
  • S y In the case of an entrance angle ⁇ of 45 degrees, the above-mentioned distance S y is approximately equal to 1/4 times the distance covered in a direction parallel to the base 62 (indicated by Sx in Fig. 6).
  • the maximum value of S x should be smaller than the length of rib a .
  • x is not larger than 0.40.
  • a larger value of x means that the display device becomes larger and that a larger potential difference has to be applied to the electrodes 28 and 29.
  • the length of rib a is preferably smaller than the length of rib b.
  • the ratio of the length of ribs a and b is smaller than 1:1.333, for example 9:16.
  • the length of rib c is approximately 12 cm.
  • the "depth" of the display device can then be limited to 15 to 20 cm.
  • a further advantage is that the influence of disturbing magnetic fields is small. The influence of magnetic fields on the paths of the electron beams is smaller according as the distance covered in the deflection space is smaller.
  • the invention is not limited to the shape of the envelope shown herein, nor by the number of electron beams, nor by a specific embodiment of the emission means, the only characteristic being that the emission means are suitable for emitting a row of electron beams, it additionally being stated that some of the embodiments are based on ideas which, as described hereinabove, can also be used for other types of display devices, nor is the invention limited to an entrance angle of 45 o , unless stated otherwise, and for the embodiments in which the entrance angle is approximately 45 o the invention is not limited to an embodiment in which the entrance angles are located symmetrically relative to an angle of 45 o .
  • the number of electron beams may be for example two, one electron beam forming an angle of 45 o - ⁇ , and one electron beam forming an angle of 45 o + ⁇ with the plane of the colour selection electrode.
  • the angles which the electron beams form with the plane of the colour selection electrode may be 45 o - ⁇ , 45 o + ⁇ and 45 o + 3 ⁇ .
  • Four electron beams may be emitted at angles of 45 o - 2 ⁇ , 45 o - ⁇ , 45 o + ⁇ and 45 o + 2 ⁇ .
  • the electron beams may enter the deflection space at a small distance from each other or at the same point.
  • the emission means may have one source for each electron beam or a common source for a fan of electron beams.
  • the display device comprises a colour selection electrode.
  • said colour selection electrode may be absent, in which case the display screen may be provided with a conducting layer and the deflection space may be formed between said conducting layer and the flat electrode 29.

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
EP90202446A 1989-09-22 1990-09-17 Dispositif de reproduction d'images et tube à rayons cathodiques Withdrawn EP0418962A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8902374A NL8902374A (nl) 1989-09-22 1989-09-22 Beeldweergave-inrichting en kathodestraalbuis.
NL8902374 1989-09-22

Publications (1)

Publication Number Publication Date
EP0418962A1 true EP0418962A1 (fr) 1991-03-27

Family

ID=19855348

Family Applications (1)

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EP90202446A Withdrawn EP0418962A1 (fr) 1989-09-22 1990-09-17 Dispositif de reproduction d'images et tube à rayons cathodiques

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Country Link
EP (1) EP0418962A1 (fr)
JP (1) JPH03133035A (fr)
NL (1) NL8902374A (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000067288A1 (fr) * 1999-04-30 2000-11-09 Sarnoff Corporation Tube cathodique economisant l'espace
WO2000067286A1 (fr) * 1999-04-30 2000-11-09 Sarnoff Corporation Tube cathodique de faible encombrement a deviation amplifiee par voie electrostatique
WO2000067287A1 (fr) * 1999-04-30 2000-11-09 Sarnoff Corporation Tube cathodique asymetrique, a gradients de potentiel, d'encombrement reduit
US6586870B1 (en) 1999-04-30 2003-07-01 Sarnoff Corporation Space-saving cathode ray tube employing magnetically amplified deflection

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4598233A (en) * 1979-09-21 1986-07-01 U.S. Philips Corporation Color display tube and device having such a tube
EP0288095A1 (fr) * 1987-02-27 1988-10-26 Koninklijke Philips Electronics N.V. Dispositif d'affichage

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4598233A (en) * 1979-09-21 1986-07-01 U.S. Philips Corporation Color display tube and device having such a tube
EP0288095A1 (fr) * 1987-02-27 1988-10-26 Koninklijke Philips Electronics N.V. Dispositif d'affichage

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000067288A1 (fr) * 1999-04-30 2000-11-09 Sarnoff Corporation Tube cathodique economisant l'espace
WO2000067286A1 (fr) * 1999-04-30 2000-11-09 Sarnoff Corporation Tube cathodique de faible encombrement a deviation amplifiee par voie electrostatique
WO2000067287A1 (fr) * 1999-04-30 2000-11-09 Sarnoff Corporation Tube cathodique asymetrique, a gradients de potentiel, d'encombrement reduit
US6476545B1 (en) 1999-04-30 2002-11-05 Sarnoff Corporation Asymmetric, gradient-potential, space-savings cathode ray tube
US6541902B1 (en) 1999-04-30 2003-04-01 Sarnoff Corporation Space-saving cathode ray tube
US6586870B1 (en) 1999-04-30 2003-07-01 Sarnoff Corporation Space-saving cathode ray tube employing magnetically amplified deflection
US6674230B1 (en) 1999-04-30 2004-01-06 Sarnoff Corporation Asymmetric space-saving cathode ray tube with magnetically deflected electron beam

Also Published As

Publication number Publication date
JPH03133035A (ja) 1991-06-06
NL8902374A (nl) 1991-04-16

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