CA1093625A - Apparatus producing static eight-pole magnetic field for correcting raster distortion in a television picture tube - Google Patents
Apparatus producing static eight-pole magnetic field for correcting raster distortion in a television picture tubeInfo
- Publication number
- CA1093625A CA1093625A CA285,162A CA285162A CA1093625A CA 1093625 A CA1093625 A CA 1093625A CA 285162 A CA285162 A CA 285162A CA 1093625 A CA1093625 A CA 1093625A
- Authority
- CA
- Canada
- Prior art keywords
- pole
- deflection
- deflection coil
- fields
- axes
- 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.)
- Expired
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Classifications
-
- 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
- H04N9/28—Arrangements for convergence or focusing
- H04N9/285—Arrangements for convergence or focusing using quadrupole 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
- H01J29/46—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
- H01J29/701—Systems for correcting deviation or convergence of a plurality of beams by means of magnetic fields at least
- H01J29/702—Convergence correction arrangements therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2229/00—Details of cathode ray tubes or electron beam tubes
- H01J2229/56—Correction of beam optics
- H01J2229/568—Correction of beam optics using supplementary correction devices
- H01J2229/5681—Correction of beam optics using supplementary correction devices magnetic
- H01J2229/5687—Auxiliary coils
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Video Image Reproduction Devices For Color Tv Systems (AREA)
- Details Of Television Scanning (AREA)
Abstract
ABSTRACT:
Cushion-like and barrel-like frame distortions can be corrected for by generating in the system of deflection coils of a black-and-white or colour display tube a static eight-pole field the poles of which are situated betwenn the axes of a system of axes the directions of which of the axes alternately coincide and extend diagonally with the two directions of deflection. In colour display tubes the eight-pole field is preferably situated on the side of the display screen of the system of deflection coils so as to minimize the influence on the convergence. The influence on the convergence can be eliminated substantially by incorporating a second eight-pole of opposite polarity on the gun side of the system of deflection coils.
Cushion-like and barrel-like frame distortions can be corrected for by generating in the system of deflection coils of a black-and-white or colour display tube a static eight-pole field the poles of which are situated betwenn the axes of a system of axes the directions of which of the axes alternately coincide and extend diagonally with the two directions of deflection. In colour display tubes the eight-pole field is preferably situated on the side of the display screen of the system of deflection coils so as to minimize the influence on the convergence. The influence on the convergence can be eliminated substantially by incorporating a second eight-pole of opposite polarity on the gun side of the system of deflection coils.
Description
1~936ZS
The invention relates to a colour television display device comprising a display tube of the shadow mask type having a neck portion accomodating an electron gun assembly for generating a plurality of electron beams and a funnel-shaped portion whose widest end is terminated in a display screen; and a system of deflection coils coaxially arranged about the tube at the transition between the neck .
and funnel-shaped portions w'nich deflection coil system com-prises first and second deflection coil units each coil unit having two substantially symmetrical coil halves situated opposite each other, the first deflection coil unit being positioned 90 with respect to the second unit such that the deflection coil units, when energised, deflect the electron beams in first and second orthoginal deflection directions.
It is an object of the invention to provide such a colour television display device where cushion or barrel shaped raster distortion can be corrected by magnet fields.
The invention provides a colour television display device comprising a display tube of the shadow mask type having a neck portion accomodating an electron gun assembly for generating a plurality of electron beams and a funnel-shaped portion whose widest end is terminated in a display screen, a system of deflection coils coaxially arranged about the tube at the transition between the neck and funnel-shaped portions which deflection coil system com-prises first and second deflection coil units and each coil unit having two substantially symmetrical coil halves situat-ed opposite each other, the first deflection coil unit being ~0936Z5 positioned 90 with respect to the second unit such that the deflection coil units, when energised, deflect the electron beams in first and second orthoginal deflection directions; and means for generating first and second static eight pole magnetic fields the poles of which are situated between the axes of a system of axes which alternatively colncoide with and lie diagonally between the said first and second deflection directions, said first eight pole field being generated at or beyond the front end of said deflection coil system which front end faces the display screen whilst the second eight pole field is generated at or beyond the rear end of said deflection coil system which rear end faces the electron gun assembly, correspondingly positioned poles of said first and second eight pole fields being of opposite magnetic polarity.
The means for generating the first and second eight pole fields may comprise first and second arrangements of permanent magnets, each arrangement compris-ing four or eight permanent magnetics. The arrangements could alternatively be made up of electromagnets.
One of the eight pole fields may be generated by a pair of rings each being magnetised to have eight magnetic poles, the rings being coaxially mounted and adapted to rotate with respect to each other in order that the strength of the eight pole field so produced may be varied.
The invention also provides the combination of a system of deflection coils and means for generating first and second static eight pole magnetic fields for use ~0936Z5 P~N. 8492.
with a colour television display device as described above.
The invention additionally provides a colour television display tube of the shadow mask type and the said combina-tion.
In our U.S. Patent 4,088,930 - Barten - May 9, 1978 a system is described with which a convergence cor-rection for the isotropic astigmatism can be obtained with-out the landing being noteworthily influenced by it by a dynamic energization of four toroidal windings provided on the core of the deflection coil. For this dynamic energiza-tion parabolic or sawtooth voltages are necessary which have to be generated in separate circuits.
As already shown in the above mentioned Patent Application, an n-pole field can be described with _ _ (1/2n-1) B = Av (1) in which B iS the vector denoting the magnetic field strength B in the complex plane A is an (integration) constant, and v is a complex auxiliary quantity which can be expressed in the coordinates x and _ so that:
B = By + i BX (2) and v = y - i x (3) During the deflection the centre of the three electron beams in the n-pole field moves towards the position xO, yO. Description of the field with respect to said new centre yields the relationship:
B = A (vO - v ~)(l/2n - l) wherein O vO = yO - i xO
v' = y' - i x' (6) B
and x' and y' are the coordinates in the shifted system of coordinates. For the eight--pole used in this invention it follows from (4):
B = A(vo + 3vov + 3vov' + v' ) (7) Now is, generally, with larger deflection ¦vO¦ 7 ¦v ¦ ' in other words, the displacement in the eight-pole fleld caused by the deflection then is large with respect to the eccentricity of the beams. As a result of this the terms with v 2 and v 3 are negligible, so that it holds to an approximation that:
B = A (vO + 3Vov ) (8) The first term Avo represents a homogeneous field the strength of which varies with the third power of the deflection and the direction of which depends on the direction of the deflection. This field exerts an identical influence on the three electron beams on the raster shape but not on the convergence. The second term 3Avo v represents a static four-pole field the strength of which varies with vO, so with the square of the deflection and thus influences the convergence. In order to be able to use the eight-pole for correction of the raster shape in a colour display tube the influence on the convergence should preferably be minimum. Therefore, the second term of formula (8) should be small with respect to the first term. This can be achieved by causing the eight-pole field to extend preferably not over the whole deflection field but by providing it only on the display screen side of the deflection field.
The static eight-pole magnetic field may be constructed in a number of manners. For example, four 1~ .
~V936ZS
or eight permanent magnets or electromagnets may be used which may be situated, for example, to form a ring, or radiate from the display tube. The magnets may be incorporated in the housing of the system of deflection coils, be placed substantially against it or by secured at some distance therefrom, for example, against the envelope of the display tube.
As the influence on the convergence may still be too large when a single eight pole field is used there is generated at or beyond the other end of the system of deflection coils situated a second static eight-pole field of opposite polarity. The strength of the second eight-pole may then be chosen to be so that the second term of formula (8) is compensated for and hence substantially no influence exists of the convergence any longer. The first term of formula (8) which determines the raster distortion is only little counteracted by the first term of the second eight-pole field. This is because vO in the second eight-pole is much smaller. Just as the first eight-pole, the second eight-pole may be manufactured in a number of manners by means of coils, electromagnets and permanent magnets.
The invention can be used with colour display tubes of inter alia the "delta"type in which the electron beams pass through the corners of an equilateral triangle which is situated in a plane substantially at right angles to the tube's longitudinal axis. However, the invention also proves suitable for colour display tubes of the "-in-line" type in which the electron beams are situated substantially in one plane.
-~936ZS PHN 8492 As static eight-poles are used, no voltages or currents varying with the deflection are necessary.
Thus no extra circuits are necessary to generate these currents or voltages. In the invention, th~ dynamic character of the required correction is obtained by the deflection of the electron beam itself.
The invention will now be described in greater detail with reference to a drawing, in which Figure 1 shows a colour display tube of the "in-line" type according to the invention, Figure 2 shows an eight--pole field and the forces acting on the electron beam as a result thereof, Figure 3 shows the effect of the eight-pole on the frame shape, and Figures 4 to 12 show a number of possibilities for generating an eight-pole field, The colour display tube shown in Figure 1 -comprises a glass envelope 1 which has a neck 2 and a funnel or cone-shaped part 3. Three electron guns 7, 8 and 9 are provided in the neck 2. The colour display tube is of the "in-line" type so that the axes of the guns 7, 8 and 9 are situated substantially in one plane. The electron beams generated by these electron guns are deflected by the system of deflection coils 11 and impinge upon the display screen 4 through the apertures 6 in the colour selection electrode 5 (The shadow mask). The three electron beams pass through the apertures 6 at a small angle with each other (the so-called colour selection angle) and `~B -6-~93~Z5 PHM 8492 consequently each impinge only upon phosphor strips of one colour. The system of deflection coils 11 may comprise a number of saddle-shaped coils and/or toroidal coils. An important property of the tube is the convergence. Con-vergence is the substantial coincidence of the threeelectron beams 27, 28 and 29 in one point in the apertures 6 of the colour selection electrode 5. The beams must not only converge in one point in the centre of the colour selection electrode but this must remain also during the deflection with the system of deflection coils 11. This is necessary because otherwise the red, green and blue rasters no longer coincide entirely and coloured edges at the transitions are formed in the picture. Good convergence in the centre of the colour selection electrode of a col-our display tube can be obtained with simple means.However,it is particularly difficult to maintain a good convergence also for the parts of the colour selection electrode in which a large deflection of the electron beams has taken place, the cause of this being the un-equal influence of the deflection field on the threeelectron beams. Another important property is the extent of raster distortion. The raster distortion which is expressed in a cushion~like and/or barrel-like distort-ion of the picture occurs for the greater part as a re-sult of a non-linear deflection by the system of de-flection coils. Such distortion also occurs in deflect-ion coils for black-and-white tubes where the design of deflection coils may be mainly directed to the minimiz-ation of the extent of the distortion. However, this necessity is omitted when an eight pole is used-In colour lV936Z5 display tubes the convergence is most important. The con-siderable distortion which often occurs in deflection coils providing a good convergence has so far been corrected for by passing currents through the individual winding groups of the system of deflection coils. The correction currents must be generated by extra circuits, so that this solution is cumbersome and expensive. The correction in a colour display tube is carried out by means of static magnetic eight-pole fields one of which is situated in or near the front end of the system of deflection coils 11 which faces the display screen 4 and is generated by a number of magnets 12. This eight-pole field can be generated by means of permanent magnets or by means of electromagnets or coils.
The coils or magnets may be incorporated in the system of deflection coils 11. It is alternatively possible for them to be assembled at some distance therefrom closer to the -~
display screen, and supported, for example by means of ;
braces or strips. As the influence of this eight-pole field on the convergence can prove to be too large, a second . eight-pole field is generated at the other (rear) end of the deflection coil system which focus the electron gun assembly the polarity of which is opposite to that of the first eight-pole field by means of a number of magnets - 13 so that said influence is compensated for without con-siderably influencing the positive influence on the raster distortion.
Fig. 2 shows diagrammatically an eight-pole field by means of a number of field lines 14. The axes X
and Y coincide with the axes of the deflection directions.
B
--8~
~0936Z~i PHN 8492 The forces F acting on each electron beam are shown in the Figure. The north and south magnetic oles (N and Z) are situated between the axes. The eight~pole field need not be completely symmetrical. ~y making the eight pole not quite symmetrical, higher-order multiple fields are obtained in addition (for example a twelve-pole, sixteen-pole) with which higher order errors in the raster can be corrected for.
Fig. 3 shows a cushion-like distortion of the raster (solid line). By using the invention, the forces F
act on the electron beam(s) in such manner that the raster is corrected (broken line). The raster distortion may also be barrel-shaped. In order to correct for raster distortion, the polarity of the eight-pole must be such that the forces F are directed just in the opposite direction.
Figures 4 to 12 show a number of possibilities for generating an eight-pole.
Figure 4 shows how an eight-pole field can be generated by means of four permanent magnets 15, 16, 17 and 18.
Figure 5 shows how this is possible with a permanent magnetic ring 19 having pole pieces.
Figures 6 and 7 show the electromagnets 20 and 21 which can replace the permanent magnets of Figures 3 and 4.
Figure 8 shows an eight-pole field generated by eight permanent magnets 22.These magnets may be in-corporated in the system of deflection coils 11 or be assembled at a small distance therefrom.
Figure 9 shows that it is also possible to ~B
_g ~V936ZS
generate an eight-pole by means of a number of coils 23.
Figure 10 shows the toroidal construction for generating an eight-pole field. A number of coils 25 are provided around a magnetic yoke 24.
Figure 11 shows two magnetic rings 26 and 27 constructed to produce an eight-pole with magnetic regions 42. By rotating these rings relative to each other, the strength of the eight-pole field can be adjusted. Rotating the two rings at the same time may be carried out by means of a rack and pinion transmission which is shown in Fig. 12.
Internal teeth 28 are provided on ring 26 and external teeth 29 are provided on ring 27 which are coupled by means of - a pinion 30. Such an adjustable eight-pole is perferably used for producing the second eight-pole field.
The invention relates to a colour television display device comprising a display tube of the shadow mask type having a neck portion accomodating an electron gun assembly for generating a plurality of electron beams and a funnel-shaped portion whose widest end is terminated in a display screen; and a system of deflection coils coaxially arranged about the tube at the transition between the neck .
and funnel-shaped portions w'nich deflection coil system com-prises first and second deflection coil units each coil unit having two substantially symmetrical coil halves situated opposite each other, the first deflection coil unit being positioned 90 with respect to the second unit such that the deflection coil units, when energised, deflect the electron beams in first and second orthoginal deflection directions.
It is an object of the invention to provide such a colour television display device where cushion or barrel shaped raster distortion can be corrected by magnet fields.
The invention provides a colour television display device comprising a display tube of the shadow mask type having a neck portion accomodating an electron gun assembly for generating a plurality of electron beams and a funnel-shaped portion whose widest end is terminated in a display screen, a system of deflection coils coaxially arranged about the tube at the transition between the neck and funnel-shaped portions which deflection coil system com-prises first and second deflection coil units and each coil unit having two substantially symmetrical coil halves situat-ed opposite each other, the first deflection coil unit being ~0936Z5 positioned 90 with respect to the second unit such that the deflection coil units, when energised, deflect the electron beams in first and second orthoginal deflection directions; and means for generating first and second static eight pole magnetic fields the poles of which are situated between the axes of a system of axes which alternatively colncoide with and lie diagonally between the said first and second deflection directions, said first eight pole field being generated at or beyond the front end of said deflection coil system which front end faces the display screen whilst the second eight pole field is generated at or beyond the rear end of said deflection coil system which rear end faces the electron gun assembly, correspondingly positioned poles of said first and second eight pole fields being of opposite magnetic polarity.
The means for generating the first and second eight pole fields may comprise first and second arrangements of permanent magnets, each arrangement compris-ing four or eight permanent magnetics. The arrangements could alternatively be made up of electromagnets.
One of the eight pole fields may be generated by a pair of rings each being magnetised to have eight magnetic poles, the rings being coaxially mounted and adapted to rotate with respect to each other in order that the strength of the eight pole field so produced may be varied.
The invention also provides the combination of a system of deflection coils and means for generating first and second static eight pole magnetic fields for use ~0936Z5 P~N. 8492.
with a colour television display device as described above.
The invention additionally provides a colour television display tube of the shadow mask type and the said combina-tion.
In our U.S. Patent 4,088,930 - Barten - May 9, 1978 a system is described with which a convergence cor-rection for the isotropic astigmatism can be obtained with-out the landing being noteworthily influenced by it by a dynamic energization of four toroidal windings provided on the core of the deflection coil. For this dynamic energiza-tion parabolic or sawtooth voltages are necessary which have to be generated in separate circuits.
As already shown in the above mentioned Patent Application, an n-pole field can be described with _ _ (1/2n-1) B = Av (1) in which B iS the vector denoting the magnetic field strength B in the complex plane A is an (integration) constant, and v is a complex auxiliary quantity which can be expressed in the coordinates x and _ so that:
B = By + i BX (2) and v = y - i x (3) During the deflection the centre of the three electron beams in the n-pole field moves towards the position xO, yO. Description of the field with respect to said new centre yields the relationship:
B = A (vO - v ~)(l/2n - l) wherein O vO = yO - i xO
v' = y' - i x' (6) B
and x' and y' are the coordinates in the shifted system of coordinates. For the eight--pole used in this invention it follows from (4):
B = A(vo + 3vov + 3vov' + v' ) (7) Now is, generally, with larger deflection ¦vO¦ 7 ¦v ¦ ' in other words, the displacement in the eight-pole fleld caused by the deflection then is large with respect to the eccentricity of the beams. As a result of this the terms with v 2 and v 3 are negligible, so that it holds to an approximation that:
B = A (vO + 3Vov ) (8) The first term Avo represents a homogeneous field the strength of which varies with the third power of the deflection and the direction of which depends on the direction of the deflection. This field exerts an identical influence on the three electron beams on the raster shape but not on the convergence. The second term 3Avo v represents a static four-pole field the strength of which varies with vO, so with the square of the deflection and thus influences the convergence. In order to be able to use the eight-pole for correction of the raster shape in a colour display tube the influence on the convergence should preferably be minimum. Therefore, the second term of formula (8) should be small with respect to the first term. This can be achieved by causing the eight-pole field to extend preferably not over the whole deflection field but by providing it only on the display screen side of the deflection field.
The static eight-pole magnetic field may be constructed in a number of manners. For example, four 1~ .
~V936ZS
or eight permanent magnets or electromagnets may be used which may be situated, for example, to form a ring, or radiate from the display tube. The magnets may be incorporated in the housing of the system of deflection coils, be placed substantially against it or by secured at some distance therefrom, for example, against the envelope of the display tube.
As the influence on the convergence may still be too large when a single eight pole field is used there is generated at or beyond the other end of the system of deflection coils situated a second static eight-pole field of opposite polarity. The strength of the second eight-pole may then be chosen to be so that the second term of formula (8) is compensated for and hence substantially no influence exists of the convergence any longer. The first term of formula (8) which determines the raster distortion is only little counteracted by the first term of the second eight-pole field. This is because vO in the second eight-pole is much smaller. Just as the first eight-pole, the second eight-pole may be manufactured in a number of manners by means of coils, electromagnets and permanent magnets.
The invention can be used with colour display tubes of inter alia the "delta"type in which the electron beams pass through the corners of an equilateral triangle which is situated in a plane substantially at right angles to the tube's longitudinal axis. However, the invention also proves suitable for colour display tubes of the "-in-line" type in which the electron beams are situated substantially in one plane.
-~936ZS PHN 8492 As static eight-poles are used, no voltages or currents varying with the deflection are necessary.
Thus no extra circuits are necessary to generate these currents or voltages. In the invention, th~ dynamic character of the required correction is obtained by the deflection of the electron beam itself.
The invention will now be described in greater detail with reference to a drawing, in which Figure 1 shows a colour display tube of the "in-line" type according to the invention, Figure 2 shows an eight--pole field and the forces acting on the electron beam as a result thereof, Figure 3 shows the effect of the eight-pole on the frame shape, and Figures 4 to 12 show a number of possibilities for generating an eight-pole field, The colour display tube shown in Figure 1 -comprises a glass envelope 1 which has a neck 2 and a funnel or cone-shaped part 3. Three electron guns 7, 8 and 9 are provided in the neck 2. The colour display tube is of the "in-line" type so that the axes of the guns 7, 8 and 9 are situated substantially in one plane. The electron beams generated by these electron guns are deflected by the system of deflection coils 11 and impinge upon the display screen 4 through the apertures 6 in the colour selection electrode 5 (The shadow mask). The three electron beams pass through the apertures 6 at a small angle with each other (the so-called colour selection angle) and `~B -6-~93~Z5 PHM 8492 consequently each impinge only upon phosphor strips of one colour. The system of deflection coils 11 may comprise a number of saddle-shaped coils and/or toroidal coils. An important property of the tube is the convergence. Con-vergence is the substantial coincidence of the threeelectron beams 27, 28 and 29 in one point in the apertures 6 of the colour selection electrode 5. The beams must not only converge in one point in the centre of the colour selection electrode but this must remain also during the deflection with the system of deflection coils 11. This is necessary because otherwise the red, green and blue rasters no longer coincide entirely and coloured edges at the transitions are formed in the picture. Good convergence in the centre of the colour selection electrode of a col-our display tube can be obtained with simple means.However,it is particularly difficult to maintain a good convergence also for the parts of the colour selection electrode in which a large deflection of the electron beams has taken place, the cause of this being the un-equal influence of the deflection field on the threeelectron beams. Another important property is the extent of raster distortion. The raster distortion which is expressed in a cushion~like and/or barrel-like distort-ion of the picture occurs for the greater part as a re-sult of a non-linear deflection by the system of de-flection coils. Such distortion also occurs in deflect-ion coils for black-and-white tubes where the design of deflection coils may be mainly directed to the minimiz-ation of the extent of the distortion. However, this necessity is omitted when an eight pole is used-In colour lV936Z5 display tubes the convergence is most important. The con-siderable distortion which often occurs in deflection coils providing a good convergence has so far been corrected for by passing currents through the individual winding groups of the system of deflection coils. The correction currents must be generated by extra circuits, so that this solution is cumbersome and expensive. The correction in a colour display tube is carried out by means of static magnetic eight-pole fields one of which is situated in or near the front end of the system of deflection coils 11 which faces the display screen 4 and is generated by a number of magnets 12. This eight-pole field can be generated by means of permanent magnets or by means of electromagnets or coils.
The coils or magnets may be incorporated in the system of deflection coils 11. It is alternatively possible for them to be assembled at some distance therefrom closer to the -~
display screen, and supported, for example by means of ;
braces or strips. As the influence of this eight-pole field on the convergence can prove to be too large, a second . eight-pole field is generated at the other (rear) end of the deflection coil system which focus the electron gun assembly the polarity of which is opposite to that of the first eight-pole field by means of a number of magnets - 13 so that said influence is compensated for without con-siderably influencing the positive influence on the raster distortion.
Fig. 2 shows diagrammatically an eight-pole field by means of a number of field lines 14. The axes X
and Y coincide with the axes of the deflection directions.
B
--8~
~0936Z~i PHN 8492 The forces F acting on each electron beam are shown in the Figure. The north and south magnetic oles (N and Z) are situated between the axes. The eight~pole field need not be completely symmetrical. ~y making the eight pole not quite symmetrical, higher-order multiple fields are obtained in addition (for example a twelve-pole, sixteen-pole) with which higher order errors in the raster can be corrected for.
Fig. 3 shows a cushion-like distortion of the raster (solid line). By using the invention, the forces F
act on the electron beam(s) in such manner that the raster is corrected (broken line). The raster distortion may also be barrel-shaped. In order to correct for raster distortion, the polarity of the eight-pole must be such that the forces F are directed just in the opposite direction.
Figures 4 to 12 show a number of possibilities for generating an eight-pole.
Figure 4 shows how an eight-pole field can be generated by means of four permanent magnets 15, 16, 17 and 18.
Figure 5 shows how this is possible with a permanent magnetic ring 19 having pole pieces.
Figures 6 and 7 show the electromagnets 20 and 21 which can replace the permanent magnets of Figures 3 and 4.
Figure 8 shows an eight-pole field generated by eight permanent magnets 22.These magnets may be in-corporated in the system of deflection coils 11 or be assembled at a small distance therefrom.
Figure 9 shows that it is also possible to ~B
_g ~V936ZS
generate an eight-pole by means of a number of coils 23.
Figure 10 shows the toroidal construction for generating an eight-pole field. A number of coils 25 are provided around a magnetic yoke 24.
Figure 11 shows two magnetic rings 26 and 27 constructed to produce an eight-pole with magnetic regions 42. By rotating these rings relative to each other, the strength of the eight-pole field can be adjusted. Rotating the two rings at the same time may be carried out by means of a rack and pinion transmission which is shown in Fig. 12.
Internal teeth 28 are provided on ring 26 and external teeth 29 are provided on ring 27 which are coupled by means of - a pinion 30. Such an adjustable eight-pole is perferably used for producing the second eight-pole field.
Claims (4)
1. A colour television display device comprising a display tube of the shadow mask type having a neck portion accomodating an electron gun assembly for generating a plurality of electron beams and a funnel-shaped portion whose widest end is terminated in a display screen; a system of deflection coils coaxically arranged about the tube at the transition between the neck and funnel-shaped portions which deflection coil system comprises first and second deflection coil units each coil unit having two substantially symmetrical coil halves situated opposite each other, the first deflection coil unit being positioned 90° with respect to the second unit such that the deflection coil units, when energised, deflect the electron beams in first and second orthoginal deflection directions;
and means fox generating first and second static eight pole magnetic fields the poles of which are situated between the axes of a system of axes which alternately coincide with and lie diagonally between the said first and second deflection directions, said first eight pole field being generated at or beyond the front end of said deflection coil system which front end faces the display screen whilst the second eight pole field is generated at or beyond the rear end of said deflection coil system which rear end faces the electron gun assembly, correspondingly positioned poles of said first and second eight pole fields being of opposite magnetic polarity.
and means fox generating first and second static eight pole magnetic fields the poles of which are situated between the axes of a system of axes which alternately coincide with and lie diagonally between the said first and second deflection directions, said first eight pole field being generated at or beyond the front end of said deflection coil system which front end faces the display screen whilst the second eight pole field is generated at or beyond the rear end of said deflection coil system which rear end faces the electron gun assembly, correspondingly positioned poles of said first and second eight pole fields being of opposite magnetic polarity.
2. A display device as claimed in Claim 1, in which said means comprises first and second arrangements of permanent magnets for respectively generating said first and second eight pole fields, each arrangement comprising either four or eight permanent magnets.
3. A display device as claimed in Claim 1, in which said means comprises first and second arrangements of electromagnets for respectively generating said first and second eight pole fields.
4. A display device as claimed in Claim 1, in which one of said eight pole fields is generated by a pair of rings each being magnetized to have eight magnetic poles, said rings being coaxically mounted and adapted to rotate with respect to each other in order that the strength of the eight pole field so produced may be varied.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7609374 | 1976-08-24 | ||
| NL7609374A NL7609374A (en) | 1976-08-24 | 1976-08-24 | DEVICE FOR DISPLAYING TELEVISION IMAGES, DEVICE COIL SYSTEM FOR SUCH DEVICE AND PICTURE TUBE FITTED WITH SUCH DEFLECTION COIL SYSTEM. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093625A true CA1093625A (en) | 1981-01-13 |
Family
ID=19826783
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA285,162A Expired CA1093625A (en) | 1976-08-24 | 1977-08-18 | Apparatus producing static eight-pole magnetic field for correcting raster distortion in a television picture tube |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS593018B2 (en) |
| AU (1) | AU509555B2 (en) |
| BE (1) | BE858010A (en) |
| BR (1) | BR7705588A (en) |
| CA (1) | CA1093625A (en) |
| DD (1) | DD131435A5 (en) |
| DE (1) | DE2736162A1 (en) |
| ES (1) | ES461806A1 (en) |
| FR (1) | FR2363186A1 (en) |
| GB (1) | GB1567669A (en) |
| IT (1) | IT1084860B (en) |
| MX (1) | MX143041A (en) |
| NL (1) | NL7609374A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5206559A (en) * | 1989-08-04 | 1993-04-27 | Kabushiki Kaisha Toshiba | Cathode ray tube which improves deflection aberration |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL181895C (en) * | 1979-10-02 | 1987-11-16 | Philips Nv | CATHODE JET TUBE WITH CORRECTION RINGS MULTIPOLO MAGNETIZED. |
| NL8104735A (en) * | 1980-12-05 | 1982-07-01 | Philips Nv | CATHODE SPRAY TUBE WITH A DEFLECTION UNIT CONTAINING PERMANENT MAGNETS WHICH GENERATES A STATIC MULTIPOLO FIELD FOR SIMULATING A MODULATION OF THE DYNAMIC DEFLECTION FIELD. |
| GB8611321D0 (en) * | 1986-05-09 | 1986-06-18 | Philips Nv | Correcting electron beam misconvergance |
| NL8601512A (en) * | 1986-06-11 | 1988-01-04 | Philips Nv | CATHODE BEAM WITH MAGNETIC FOCUSING LENS. |
| GB2208034A (en) * | 1987-08-13 | 1989-02-15 | Ibm | Reducing magnetic radiation in front of a cathode ray tube screen |
| US5225736A (en) * | 1988-06-27 | 1993-07-06 | Kabushiki Kaisha Toshiba | Color cathode ray tube apparatus |
| US5177399A (en) * | 1988-06-27 | 1993-01-05 | Kabushiki Kaisha Toshiba | Color cathode ray tube apparatus |
| FR2667722B1 (en) * | 1990-10-09 | 1996-09-06 | Videocolor Sa | ELECTROMAGNETIC GEOMETRY CORRECTOR FOR SINGLE - BEAM CATHODE RAY TUBE. |
| US5258693A (en) * | 1990-10-09 | 1993-11-02 | Videocolor, S.A. | Geometry corrector for a cathode ray tube |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB739068A (en) * | 1952-08-09 | 1955-10-26 | Emi Ltd | Improvements in or relating to cathode ray tube arrangements |
| GB750310A (en) * | 1953-04-10 | 1956-06-13 | Marconi Wireless Telegraph Co | Improvements in or relating to cathode ray tubes |
| NL148441B (en) * | 1969-07-09 | 1976-01-15 | Philips Nv | COLOR TV DISPLAY DEVICE EQUIPPED WITH AN ELECTRON BAM TUBE AND DEVICE COIL SYSTEM FOR USE THEREIN. |
-
1976
- 1976-08-24 NL NL7609374A patent/NL7609374A/en not_active Application Discontinuation
-
1977
- 1977-08-11 DE DE19772736162 patent/DE2736162A1/en active Granted
- 1977-08-18 CA CA285,162A patent/CA1093625A/en not_active Expired
- 1977-08-19 AU AU28049/77A patent/AU509555B2/en not_active Expired
- 1977-08-19 GB GB3488977A patent/GB1567669A/en not_active Expired
- 1977-08-19 DD DD20066177A patent/DD131435A5/en unknown
- 1977-08-22 ES ES461806A patent/ES461806A1/en not_active Expired
- 1977-08-22 BR BR7705588A patent/BR7705588A/en unknown
- 1977-08-22 JP JP10038777A patent/JPS593018B2/en not_active Expired
- 1977-08-22 FR FR7725549A patent/FR2363186A1/en active Granted
- 1977-08-22 BE BE180352A patent/BE858010A/en unknown
- 1977-08-22 MX MX17030977A patent/MX143041A/en unknown
- 1977-08-22 IT IT2685277A patent/IT1084860B/en active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5206559A (en) * | 1989-08-04 | 1993-04-27 | Kabushiki Kaisha Toshiba | Cathode ray tube which improves deflection aberration |
Also Published As
| Publication number | Publication date |
|---|---|
| NL7609374A (en) | 1978-02-28 |
| FR2363186B1 (en) | 1981-12-04 |
| BR7705588A (en) | 1978-06-06 |
| JPS5326618A (en) | 1978-03-11 |
| AU509555B2 (en) | 1980-05-15 |
| MX143041A (en) | 1981-02-23 |
| GB1567669A (en) | 1980-05-21 |
| BE858010A (en) | 1978-02-22 |
| DE2736162C2 (en) | 1987-11-05 |
| IT1084860B (en) | 1985-05-28 |
| FR2363186A1 (en) | 1978-03-24 |
| DE2736162A1 (en) | 1978-03-09 |
| AU2804977A (en) | 1979-02-22 |
| ES461806A1 (en) | 1978-05-16 |
| DD131435A5 (en) | 1978-06-21 |
| JPS593018B2 (en) | 1984-01-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |