EP0281184A1 - Bildwiedergabevorrichtung mit Mitteln zur Kompensation der Streufelder - Google Patents

Bildwiedergabevorrichtung mit Mitteln zur Kompensation der Streufelder Download PDF

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Publication number
EP0281184A1
EP0281184A1 EP88200294A EP88200294A EP0281184A1 EP 0281184 A1 EP0281184 A1 EP 0281184A1 EP 88200294 A EP88200294 A EP 88200294A EP 88200294 A EP88200294 A EP 88200294A EP 0281184 A1 EP0281184 A1 EP 0281184A1
Authority
EP
European Patent Office
Prior art keywords
coil
coils
display device
compensation
deflection coil
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.)
Granted
Application number
EP88200294A
Other languages
English (en)
French (fr)
Other versions
EP0281184B1 (de
Inventor
Albertus Aemilius Seyno Sluyterman
Gerrit Bosch
Fransicus Maria Petrus Pius Doomernik
Adriaan Jacob Groothoff
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 EP0281184A1 publication Critical patent/EP0281184A1/de
Application granted granted Critical
Publication of EP0281184B1 publication Critical patent/EP0281184B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H01J29/70—Arrangements for deflecting ray or beam
    • 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
    • H01J29/003—Arrangements for eliminating unwanted electromagnetic effects, e.g. demagnetisation arrangements, shielding coils
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2229/00—Details of cathode ray tubes or electron beam tubes
    • H01J2229/0007—Elimination of unwanted or stray electromagnetic effects
    • H01J2229/0015—Preventing or cancelling fields leaving the enclosure

Definitions

  • the invention relates to a picture display device having a display tube the rear part of which consists of a cylindrical neck accommodating a device for generating electron beams and the front part of which is funnel-shaped with the widest part being present on the front side, and a picture display phosphor screen, said display device also being provided with an electromagnetic deflection unit mounted around the display tube for deflecting electron beams across the display screen and comprising a line deflection coil and a field deflection coil which, when energized, generate magnetic fields having at least a dipole component.
  • this object is realized in that the device is provided with a compensation coil system which is oriented in such manner and in operation is energizable in such manner that, measured at a predetermined distance from the picture display device, at least the strength of the local magnetic dipole field is below a desired standard, said compensation coil system comprising a first set of compensation coils arranged symmetrically relative to the plane of symmetry of the line deflection coil on the outer side of the deflection unit, and extending with main portions of their lenghts in the axial direction, and two further compensation coils arranged symmetrically relative to the plane of symmetry of the line deflection coil on the outer side of the deflection unit and extending at least substantially parallel to the display screen.
  • the invention is based on the recognition that for interference suppression of magnetic fields at a long distance from the interfering source (distances of, for example more than 3 m) it is sufficient to compensate the dipole component only.
  • Deflection units also produce higher order (for example sixpole and tenpole) magnetic deflection field components, but their strength decreases much more rapidly as the distance increases than the strength of the dipole component so that their contributions are already negligible at a distance of approximately 50 cm.
  • the magnetic dipole moment of an interfering source (the line deflection coil) can be compensated by adding an opposed dipole moment.
  • This dipole moment can be obtained by energizing two current loops positioned on the outer side of the line deflection coil and extending with two main portions of their lengths at least approximately parallel to the tube axis on facing sides thereof, said current loops having the required number of turns, the required surface area and the required orientation.
  • Energizing may be effected by arranging the compensation coils constituted by the current loops in series with or parallel to the line deflection coil.
  • the compensation coils should preferably cover a surface area which is as large as possible. The larger the surface area the less energy will be required to generate a desired magnetic dipole moment. A surface area of, for example 1 to 10 dm2 has been found suitable in practice.
  • the number of turns of the compensation coils may be small (less than 10). In many cases 2 to 6 turns may suffice.
  • the compensation coil system according to the invention comprises two further compensation coils which are arranged on the outer side of the deflection unit symmetrically relative to the plane of symmetry of the line deflection coil and extending parallel to the display screen. During operation they should be energized in the same manner as the first compensation coils.
  • the compensation coils should be large in order to reduce the energy content.
  • the two further compensation coils each comprise at least two sub-coils arranged in parallel at a predetermined distance. Their effect will be explained hereinafter.
  • the first compensation coils may be formed by current loops whose turns are substantially co-planar parallel to the plane of symmetry of the line deflection coil. It is, however, practical to form them as saddle coils which are mounted on the outer side of the electromagnetic deflection unit. Particularly if these saddle coils are of the so-called yoke winding type (i.e. wound on a support) they may be formed in such a manner that two main portions of their length extend in the axial direction on facing sides of the tube axis, which main portions together with connection portions connecting them at the ends define at least two coil windows of different size. By adjusting the surface areas of the windows (and hence of the total "effective" coil surface) it is possible to adapt the compensating dipole field to the stray field of each line deflection coil with which the first compensation coils are combined.
  • Figure 1a is a perspective elevational view of a combination of a deflection unit and a display tube placed in a cabinet 2 which can be provided with means to compensate interference fields, according to the invention.
  • a deflection unit and a display tube placed in a cabinet 2 which can be provided with means to compensate interference fields, according to the invention.
  • Figure 1a is a perspective elevational view of a combination of a deflection unit and a display tube placed in a cabinet 2 which can be provided with means to compensate interference fields, according to the invention.
  • FIG. 1a is a perspective elevational view of a combination of a deflection unit and a display tube placed in a cabinet 2 which can be provided with means to compensate interference fields, according to the invention.
  • the display tube has a cylindrical neck 1 and a funnel-shaped portion 3 the widest part of which is present on the front side of the tube and comprises a display screen (not shown).
  • the display screen comprises phosphors which upon impingement by electrons luminesce in a predetermined colour.
  • the rear part of the neck 1 accommodates an electron gun system 7 (shown diagrammatically).
  • an electromagnetic deflection unit 9 diagrammatically shown is arranged on the tube, which unit comprises, inter alia a line deflection coil 11 (Figure 1b) for deflecting the electron beams in a horizontal direction x .
  • the line deflection coil 11 may consist of, for example, two saddle-shaped coil halves. In the operating condition a sawtooth current having a frequency of between 10 and 100 kHz, for example a frequency of approximately 6 kHz flows through these coils.
  • the line deflection coil 11 is surrounded by an annular core element 10 of soft magnetic material, the so-called yoke ring, which is shown in a broken line in Figure 1b.
  • the line deflection coil can be assumed for large distances to be a current loop having a given magnetic moment.
  • the field B o in the centre of a line deflection coil without a yoke ring can be calculated to be approximately 30 Gauss.
  • the field of a practical deflection coil with a yoke ring has approximateluy twice this value.
  • the line deflection coil field at 1 m distance is approximately 1 mGauss.
  • This radiation field can be compensated by means of an auxiliary loop current having a low nI value and a large radius such that the magnetic moment is the same as that of the coil itself.
  • the orientation of the compensation loop should be such that the magnetic dipole moment generated upon current passage through this coil at a predetermined distance (for example 3 m) compensates the magnetic dipole moment of the interfering component.
  • the dipole moment of the compensation loop should be parallel to and oppositely directed relative to the dipole moment of the interfering component.
  • the interfering component is the line deflection coil in the first place.
  • the line output transformer may generate an interference field and can then be considered as an interfering component. In that case it applies that:
  • Parallel dipole moments originating from one or more components can be compensated with one current loop.
  • Non-­parallel dipole moments can be compensated with one loop when the frequency and the phase of the dipole moments to be compensated are the same.
  • Figure 2 shows a deflection unit having two sets of interference coils, a horizontally arranged set 18, 19 and a vertically arranged set 18a, 19a.
  • ⁇ Y1 remains small; the 6-pole can be reduced to a slight extent by enlarging the diameter of the coils 22 and 23 which results in ⁇ X necessarily increasing because the coils cannot be inserted in the tube.
  • a 4-pole proportional to the size of the coil, the current through the coils and the distance ⁇ Y2 is predominantly generated with the two vertical coils 24 and 25.
  • the 4- and the 6-poles can be neutralized by correct combination of coil sizes and current intensities. For the 8-­poles all coils should not become so large that they are tangential to the measuring circle because then the 8-poles and even higher harmonics start playing a role.
  • the invention provides the solution of building up the coils of the system arranged at right angles to the plane of symmetry of the line deflection coil from at least two sub-coils (28a and 28b and 29a and 29b, respectively in Figure 4).
  • ⁇ Z predetermined distance
  • each sub-coil pair may have half the number of turns which would otherwise be required for a single coil. This means that the inductance of the system with two pairs of sub-coils may be half the inductance of a set of single coils. This results in a reduction of the energy content.
  • the saddle coils 18, 19 may be of the so-called yoke winding type. This means that they are directly wound on a support.
  • This support may comprise, for example two grooved flanges which are secured to the front and rear sides of the deflection unit. The positions of the axially extending turn portions can be fixed by means of the grooves.
  • for example universal flanges (with grooves uniformly distributed over the circumference) can be used to wind compensation coils having two or more coil windows of different size. In this manner the "effective" compensation coil surface area can be adapted to each line deflection coil with which the compensation coil is combined.
  • Figure 5 is a diagrammatic plan view of a compensation saddle coil half 30 having three coil windows 31, 32 and 33 of different size.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • Picture Signal Circuits (AREA)
  • Transforming Electric Information Into Light Information (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Closed-Circuit Television Systems (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
  • Controls And Circuits For Display Device (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
EP88200294A 1987-02-24 1988-02-18 Bildwiedergabevorrichtung mit Mitteln zur Kompensation der Streufelder Expired - Lifetime EP0281184B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8700449A NL8700449A (nl) 1987-02-24 1987-02-24 Beeldweergeefinrichting met middelen voor het compenseren van lijnstrooivelden.
NL8700449 1987-02-24

Publications (2)

Publication Number Publication Date
EP0281184A1 true EP0281184A1 (de) 1988-09-07
EP0281184B1 EP0281184B1 (de) 1994-07-20

Family

ID=19849617

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88200294A Expired - Lifetime EP0281184B1 (de) 1987-02-24 1988-02-18 Bildwiedergabevorrichtung mit Mitteln zur Kompensation der Streufelder

Country Status (7)

Country Link
EP (1) EP0281184B1 (de)
JP (1) JP2677585B2 (de)
KR (1) KR960000348B1 (de)
AT (1) ATE108947T1 (de)
DE (1) DE3850687T2 (de)
NL (1) NL8700449A (de)
NO (1) NO880765L (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996023315A1 (en) * 1995-01-24 1996-08-01 International Business Machines Corporation Cathode ray tube display apparatus with reduced stray magnetic fields
US8623190B2 (en) 2005-11-28 2014-01-07 Siemens Aktiengesellschaft Device and method for performing maintenance on an apparatus in a flow duct

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0646142Y2 (ja) * 1989-04-28 1994-11-24 日本ビクター株式会社 漏れ磁束軽減装置
KR20190064899A (ko) 2017-12-01 2019-06-11 주식회사 에이치케이 작업 테이블 교환장치

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0039502A1 (de) * 1980-05-06 1981-11-11 Siemens Aktiengesellschaft Anordnung zur Kompensation von auf Farbfernsehröhren einwirkenden magnetischen Fremdfeldern
EP0179298A1 (de) * 1984-10-09 1986-04-30 Viggo Berthelsen Verfahren zur Eliminierung des Einflusses einer Magnetfeldquelle auf eine oder mehrere Personen oder Tiere und eine Vorrichtung zur Eliminierung solcher Einflüsse
US4634930A (en) * 1984-04-13 1987-01-06 Mitsubishi Denki Kabushiki Kaisha Display device
WO1987005437A1 (en) * 1986-03-04 1987-09-11 Autovision S. Blixt Ab A device for the suppression of leakage fields in front of viewing screens and the like
WO1987006054A1 (en) * 1986-03-27 1987-10-08 Telefonaktiebolaget Lm Ericsson Apparatus in cathode ray tubes for reducing the magnetic field strength in the tube environment

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8602397A (nl) * 1985-10-25 1987-05-18 Philips Nv Beeldweergeefinrichting met ontstoringsmiddelen.
SE459054C (sv) * 1986-03-07 1992-08-17 Philips Norden Ab Foerfarande foer reducering av magnetiskt laeckfaelt samt anordning foer genomfoerande av foerfarandet
JPS62268046A (ja) * 1986-05-14 1987-11-20 Mitsubishi Electric Corp 偏向ヨ−ク

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0039502A1 (de) * 1980-05-06 1981-11-11 Siemens Aktiengesellschaft Anordnung zur Kompensation von auf Farbfernsehröhren einwirkenden magnetischen Fremdfeldern
US4634930A (en) * 1984-04-13 1987-01-06 Mitsubishi Denki Kabushiki Kaisha Display device
EP0179298A1 (de) * 1984-10-09 1986-04-30 Viggo Berthelsen Verfahren zur Eliminierung des Einflusses einer Magnetfeldquelle auf eine oder mehrere Personen oder Tiere und eine Vorrichtung zur Eliminierung solcher Einflüsse
WO1987005437A1 (en) * 1986-03-04 1987-09-11 Autovision S. Blixt Ab A device for the suppression of leakage fields in front of viewing screens and the like
WO1987006054A1 (en) * 1986-03-27 1987-10-08 Telefonaktiebolaget Lm Ericsson Apparatus in cathode ray tubes for reducing the magnetic field strength in the tube environment

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996023315A1 (en) * 1995-01-24 1996-08-01 International Business Machines Corporation Cathode ray tube display apparatus with reduced stray magnetic fields
US8623190B2 (en) 2005-11-28 2014-01-07 Siemens Aktiengesellschaft Device and method for performing maintenance on an apparatus in a flow duct

Also Published As

Publication number Publication date
NL8700449A (nl) 1988-09-16
KR880010464A (ko) 1988-10-08
DE3850687D1 (de) 1994-08-25
DE3850687T2 (de) 1995-02-16
KR960000348B1 (ko) 1996-01-05
NO880765D0 (no) 1988-02-22
EP0281184B1 (de) 1994-07-20
JP2677585B2 (ja) 1997-11-17
JPS63227186A (ja) 1988-09-21
NO880765L (no) 1988-08-25
ATE108947T1 (de) 1994-08-15

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