CA1320531C - Crt focus utilising magnetic means - Google Patents
Crt focus utilising magnetic meansInfo
- Publication number
- CA1320531C CA1320531C CA000614806A CA614806A CA1320531C CA 1320531 C CA1320531 C CA 1320531C CA 000614806 A CA000614806 A CA 000614806A CA 614806 A CA614806 A CA 614806A CA 1320531 C CA1320531 C CA 1320531C
- Authority
- CA
- Canada
- Prior art keywords
- cathode
- ray tube
- neck
- cathode ray
- magnetic means
- 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 - Fee Related
Links
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
- H01J29/58—Arrangements for focusing or reflecting ray or beam
- H01J29/64—Magnetic lenses
Landscapes
- Video Image Reproduction Devices For Color Tv Systems (AREA)
Abstract
ABSTRACT
The focus of an electrostatically focused CRT may be improved by placing a split resilient ring around the neck of the CRT having radiating posts which receive ring magnets magnetised across their diameter. The ring may be translated along the neck of the CRT in the vicinity of the cathode and the magnets oriented to bunch the electron beam from the cathode and move it onto the axis of the focusing electrode. Bunching improves the electron density distribution within the spot. The magnet mounted on the ring may be turned to counteract the perturbations due to the excessive field penetration of the yoke in the low beam velocity region. A d.c. bias is added to the yoke current to compensate the resultant offset picture. After positioning of the ring, it may be glued in place.
The focus of an electrostatically focused CRT may be improved by placing a split resilient ring around the neck of the CRT having radiating posts which receive ring magnets magnetised across their diameter. The ring may be translated along the neck of the CRT in the vicinity of the cathode and the magnets oriented to bunch the electron beam from the cathode and move it onto the axis of the focusing electrode. Bunching improves the electron density distribution within the spot. The magnet mounted on the ring may be turned to counteract the perturbations due to the excessive field penetration of the yoke in the low beam velocity region. A d.c. bias is added to the yoke current to compensate the resultant offset picture. After positioning of the ring, it may be glued in place.
Description
~3~2 ~ 04942-1 RDF
IMPROVED CRT FOCUS UTILISING MAGNETnI.C MEANS
This invention relates to a method and apparatus for improving the focus oE an electrostatically focused cathode ray tube ( CRT ) .
A conventional electrostatically focused CRT comprises an e3ectron gun comprising a cathode for emitting electrons, accelerating electrodes and focusing electrodes the CRT also includas a means such as a magnetic yoke to deflec-t an electron beam, and a florescent screen. If the cathode, electrodes and yoke are not co-axial so that the electron beam does not travel along the axis of the focusing electrodes, focus will be degraded.
Further, if the yoke is off-axis or there are symmetry imperfect-ions in the magnetic fields produced by the yoke, especially within the low beam velocity region of the gun, focus will be degraded.
It is known to glue permanent magnets about the periphery of the yoke in order to compensate for imperfections in the yoke.
~owever, such permanent magnets produce stray magnetic fields which influence the electron beam in the vicinity of the cathode with a consequent degradation ln focusc U.S. Patent No. 41801,843 issued January 31, 1989 to Mensies discloses two magnetic rings fixed on the focusing electrodes inside the evacuated neck of a CRT. The magnetic rings are magnetised as a dipoles in order to provide flux lines parallel to the axis of the focusing electrode. In a well understood manner, these parallel Elux lines serve to bunch the electron beam on the axis of the focusing electrodes which improves the focus of 3 ~
049~-1 RDF
the CRT. However, the electron beam will retain focusing problems due to stray fields from the correction magnets on the yoke.
Accordlngly, there remains a need for a method and apparatus to improve the focus of a CRT which avoids drawbacks of known methods.
In accordance with the present invantion there is provided a method for improving the focus of a CRT comprising the step of: placing magnetic means around the neck of a cathode ray tube and translating and orienting said magnetic means untll the focus of the CRT improves.
In another aspect, the present invention comprises a magnetic means for use in improving the Eocus of a cathode ray tube comprising the Eollowing:
a support for translatable reception by the neck of a cathode ray tube proximate the cathocle of said cathode ray tube, said support having means to carry a plurality of magnets in a selectable orientation; and at least one magnet carried by said support~
whereby an electron beam emitted by said cathode may be bunched alon~ the axis of the focusing electrode and orienting said at least one magnet to provide a magnetic Eield making an angle with the path of said electron beam and the degree of bunching of said electron beam may be controlled by selec-ting the number of magnets carried by said support.
In the figures which disclose example embodiments of the inven-tion, ~3~53~ 04942-l RDF
~ igure l is a side schematic view oE a CRT made in accordance with this invention, ~ igure 2 is an end view of a magnetic means made in accordance with this invention, Eigure 2a is a plan view of a magnet used in the magne-tic means of figure 2, and figures 3 and 4 are a schematic views of a portion oE a CRT.
Turning to figure l, a CRT with electrostatic focusing is illustrated schematically at lO. The CRT comprises a neck 12 and a screen 14. The neck contains a cathode 16, a control electrode 18, accelerating electrodes 20 and 22, and a focusing electrode 24. A yoke 26 surrounds the neck 12. The yoke 26 comprises two coils oriented so as to produce magnetic fields at right angles to each other and to the axis of the CRT when the coils are energised, as is well understood by those skilled in the art. Permanent magnets 23a and 28b, which are correction magnets, may be glued to the yoke A voltage source 32 may supply a variable d.c. supply to one of the coils of the yoke 26. This d~c.
voltage is superimposed on the a.c. voltage which is applied to the coils to deflect an electron beam about the screen. The remainder of the electrical control system for the yoke is conventional and is not shown. A magnetic means made in accordance with this invention is shown at 30.
Figure 2 illustrates the magnetic means 30. This is seen to comprise a support 34 which is a split ring of resilient material. Three pos-ts 36a, 36b, and 36c extend radially outwardly 13 2 0 ~ 3 ~ 04942-1 RDF
from the ring 3~; these posts may support ring magnets of the type shown in figure 2a at 38. In figure 2, posts 36a and 36c are shown supporting ring magnets 38a and 38b, respectively. The ring magnets are polarized across their diameter. The inner annulus of the ring magnets 38 and the diameter of the posts are sized to pro~ide an friction fit between the magnets and the posts 36a, 36b, and 36c of the split ring; consequently, the magnets will hold any position to which they are set on the posts and in particular may be rotated on the posts to any desired rotational position.
Because of the resilience of -the split ring 30, it may be snapped over the neck of a CRT and will have a snug fit with the neck so that it will maintain any position on the neck to which it is moved. Thus, the ring may be rotated and translated on the neck of the CRT.
In general -terms, the operation of the CRT of figure 1 absent a consideration of magnetic means 30 and d.c. source 32 is as follows. Electrons emitted from the cathode 16 drift toward the control electrode 18 as a beam of electrons. The beam tends to diverge due to the forces of repulsion between the electrons of the beam. As the beam passes through the aper-ture oE the control electrode 18 it is constricted by the negative voltage on this electrode. The beam is then accelerated by the accelerating electrode 20. The focusing electrode 24 applies a concentrating Eorce to the electron beam. More particularly, the focusing electrode imparts to the electrons of the beam a velocity componen-t directed radially inwardly toward the a~is of the focusing electrode. After the beam leaves the focusing electrode it is 1~ 3 2 0 ~ 3 ~ 04942 1 RDF
accelerated by acceleratlng electrode 22 and anode 21 and is then deflected by the coils oE yoke 26. The deflected beam impinges on the screen 14.
The forces of repulsion be-tween the electrons of the beam impart a radially outwardly directed acceleration to the electrons.
The focusing electrode imparts a radially inwardly directed component of velocity to the electrons in the beam, and converges the beam to a point called the image point. It is intended this image point lies on the screen~ Since the distance from the focusing electrode to the screen varies with the angle of deflec-tion, dynamic focusing is necessary to ensure that the beam is focused at the screen irrespective of the angle of deflection.
More particularly, this image distance from the focusing electrode varies directly with the voltage on the focusing electrode, consequently, by varying the voltage of the focusing electrode depending on the angle of deflection, the beam may be focused on the screen at any angle of deflection. Correction magnets 28a and 2~b are glued to the yoke in an attempt to compensate for aberration~ in the image on the screen resulting from imperfections in the yoke.
The focus of the CRT may be improved by placing a split ring 34 on the neck of the CRT, judiciously choosing the number of ring magnets for the split ring 34, appropriately translating the ring with ring magnets and rota-ting the magnets on the posts of the ring, for reasons which will now be explained. Once the ring is in the desired position on the neck of the CRT it may be glued in ~32~3~ 04942~1 RDF
place and an appropriate d.c. bias voltage applied to the coils oE
the yoke in order to centre the image back on the screen.
As is well understood by those skllled in the art, iE
electrons are injected into a magnetic ~Eield which is perpendicular to their direction of travel, the electrons will move in circles with a radius inversely proportional to the magnetic flux density.
Consequentlyr an electron entering a magnetic field at an angle other than nine-ty degrees will follow a helical trajectory wi-th the axis of the helix parallel to the field lines of the field. A beam of electrons entering a field at an angle will accordingly follow the direction of the field with electrons which were divergent from the direction of the field following a helical trajectory. These helical trajectories keep the beam from spreading radially (so that the beam is "bunched") and hence improve the electron density distribution within a cross-section of the beam.
Figure 3 illustrates a portion of a C~T wi-th a cathode 11~ having an axis 140 ~hich is not aligned with the axis 142 of the focusing electrode 124. ~ccordingly, absent correction, an electron bezm emitted from the cathode will follow the axis 140 oE
the cathode and hence will be off the axis of the focusing electrode, which will result in degraded focus. Since the ring magnets of this invention are polarized across their diameter, the magnetic means of this invention may be used to produce a local magnetic field which makes any desired angle with the axis 140 of the cathode, such as the -field lines 150 of figure 3. The strength of this magnetic Eield may be controlLed by choosing the strength of the magnets on the posts of the ring. If ring magnets are ~32~53~ 04942-1 RDF
placed on the ring and rotated and the split ring translated so as to produce field lines 150, the electrons in the beam will tend to ~ollow the direction of Eield lines 150 toward the axis 142 of the focusing electrode. Thus the magnetic means 30 of the subject invention may be used to correct for axial mis-alignment of the cathode and Eocusing electrode.
Figure 4 illustrates a portion of a CRT showing stray field lines 200 from correction magnets on the yoke of the CRT in the vicinity of the cathode 216 and focusing electrode 224 of the CRT. It may be noted that CRT's are frequently manufactured with short necks which exacerbates the problem of stray fields since the end of the yoke is proximate the cathode area. Since the illustrated stray field induces the electron beam to follow its path, it will be apparent that the stray field moves an electron beam which is on the axis 242 of the focusing electron beam off-axis. In addition, the stray field illustrated by field lines 200 reduces the velocity component oE the beam in a direction toward the screen and parallel with axis 242. Both of these effects degrade focusing. More particularly, the second effec-t will develop local degradation of the image, as the image distance depends on the velocity of the electrons in the beam in a direction -toward the screen. Thus, a slower velocity will shorten the image distance.
The magnetic means of the subject invention may eliminate the degradation in focus caused by these stray fields by applying a field in opposition to the stray field as illustrated in do-tted lines at 2~0. Again this is achieved by appropriately orienting ~2~3~
a judiciously chosen number o~ ring magnets on the split ring oE
the magnetic means.
The subject magnetic means may simultaneously correct for both described defocusing efEects by applying resultant magne-tlc fields which resolve -to the components 150 and 250 of figures 3 and 4.
In practice, the ring and the magnets thereon are appropriately positioned by trial and error. That is, the screen of a CRT may be watched while the ring is translated and rotated and the magnets thereon rotated until focus has improved acceptably.
Application of the fields from the magnetic means of the subject inven-tion have the effect of displacing the entire image on the screen. This may be corrected by applying an appropriate d.c. bias to the yoke by means of variable d.c. voltage source 32.
The efEects illustrated in figures 3 and 4 are small and have been exaggerated in these figures for the purpose of explanation.
IMPROVED CRT FOCUS UTILISING MAGNETnI.C MEANS
This invention relates to a method and apparatus for improving the focus oE an electrostatically focused cathode ray tube ( CRT ) .
A conventional electrostatically focused CRT comprises an e3ectron gun comprising a cathode for emitting electrons, accelerating electrodes and focusing electrodes the CRT also includas a means such as a magnetic yoke to deflec-t an electron beam, and a florescent screen. If the cathode, electrodes and yoke are not co-axial so that the electron beam does not travel along the axis of the focusing electrodes, focus will be degraded.
Further, if the yoke is off-axis or there are symmetry imperfect-ions in the magnetic fields produced by the yoke, especially within the low beam velocity region of the gun, focus will be degraded.
It is known to glue permanent magnets about the periphery of the yoke in order to compensate for imperfections in the yoke.
~owever, such permanent magnets produce stray magnetic fields which influence the electron beam in the vicinity of the cathode with a consequent degradation ln focusc U.S. Patent No. 41801,843 issued January 31, 1989 to Mensies discloses two magnetic rings fixed on the focusing electrodes inside the evacuated neck of a CRT. The magnetic rings are magnetised as a dipoles in order to provide flux lines parallel to the axis of the focusing electrode. In a well understood manner, these parallel Elux lines serve to bunch the electron beam on the axis of the focusing electrodes which improves the focus of 3 ~
049~-1 RDF
the CRT. However, the electron beam will retain focusing problems due to stray fields from the correction magnets on the yoke.
Accordlngly, there remains a need for a method and apparatus to improve the focus of a CRT which avoids drawbacks of known methods.
In accordance with the present invantion there is provided a method for improving the focus of a CRT comprising the step of: placing magnetic means around the neck of a cathode ray tube and translating and orienting said magnetic means untll the focus of the CRT improves.
In another aspect, the present invention comprises a magnetic means for use in improving the Eocus of a cathode ray tube comprising the Eollowing:
a support for translatable reception by the neck of a cathode ray tube proximate the cathocle of said cathode ray tube, said support having means to carry a plurality of magnets in a selectable orientation; and at least one magnet carried by said support~
whereby an electron beam emitted by said cathode may be bunched alon~ the axis of the focusing electrode and orienting said at least one magnet to provide a magnetic Eield making an angle with the path of said electron beam and the degree of bunching of said electron beam may be controlled by selec-ting the number of magnets carried by said support.
In the figures which disclose example embodiments of the inven-tion, ~3~53~ 04942-l RDF
~ igure l is a side schematic view oE a CRT made in accordance with this invention, ~ igure 2 is an end view of a magnetic means made in accordance with this invention, Eigure 2a is a plan view of a magnet used in the magne-tic means of figure 2, and figures 3 and 4 are a schematic views of a portion oE a CRT.
Turning to figure l, a CRT with electrostatic focusing is illustrated schematically at lO. The CRT comprises a neck 12 and a screen 14. The neck contains a cathode 16, a control electrode 18, accelerating electrodes 20 and 22, and a focusing electrode 24. A yoke 26 surrounds the neck 12. The yoke 26 comprises two coils oriented so as to produce magnetic fields at right angles to each other and to the axis of the CRT when the coils are energised, as is well understood by those skilled in the art. Permanent magnets 23a and 28b, which are correction magnets, may be glued to the yoke A voltage source 32 may supply a variable d.c. supply to one of the coils of the yoke 26. This d~c.
voltage is superimposed on the a.c. voltage which is applied to the coils to deflect an electron beam about the screen. The remainder of the electrical control system for the yoke is conventional and is not shown. A magnetic means made in accordance with this invention is shown at 30.
Figure 2 illustrates the magnetic means 30. This is seen to comprise a support 34 which is a split ring of resilient material. Three pos-ts 36a, 36b, and 36c extend radially outwardly 13 2 0 ~ 3 ~ 04942-1 RDF
from the ring 3~; these posts may support ring magnets of the type shown in figure 2a at 38. In figure 2, posts 36a and 36c are shown supporting ring magnets 38a and 38b, respectively. The ring magnets are polarized across their diameter. The inner annulus of the ring magnets 38 and the diameter of the posts are sized to pro~ide an friction fit between the magnets and the posts 36a, 36b, and 36c of the split ring; consequently, the magnets will hold any position to which they are set on the posts and in particular may be rotated on the posts to any desired rotational position.
Because of the resilience of -the split ring 30, it may be snapped over the neck of a CRT and will have a snug fit with the neck so that it will maintain any position on the neck to which it is moved. Thus, the ring may be rotated and translated on the neck of the CRT.
In general -terms, the operation of the CRT of figure 1 absent a consideration of magnetic means 30 and d.c. source 32 is as follows. Electrons emitted from the cathode 16 drift toward the control electrode 18 as a beam of electrons. The beam tends to diverge due to the forces of repulsion between the electrons of the beam. As the beam passes through the aper-ture oE the control electrode 18 it is constricted by the negative voltage on this electrode. The beam is then accelerated by the accelerating electrode 20. The focusing electrode 24 applies a concentrating Eorce to the electron beam. More particularly, the focusing electrode imparts to the electrons of the beam a velocity componen-t directed radially inwardly toward the a~is of the focusing electrode. After the beam leaves the focusing electrode it is 1~ 3 2 0 ~ 3 ~ 04942 1 RDF
accelerated by acceleratlng electrode 22 and anode 21 and is then deflected by the coils oE yoke 26. The deflected beam impinges on the screen 14.
The forces of repulsion be-tween the electrons of the beam impart a radially outwardly directed acceleration to the electrons.
The focusing electrode imparts a radially inwardly directed component of velocity to the electrons in the beam, and converges the beam to a point called the image point. It is intended this image point lies on the screen~ Since the distance from the focusing electrode to the screen varies with the angle of deflec-tion, dynamic focusing is necessary to ensure that the beam is focused at the screen irrespective of the angle of deflection.
More particularly, this image distance from the focusing electrode varies directly with the voltage on the focusing electrode, consequently, by varying the voltage of the focusing electrode depending on the angle of deflection, the beam may be focused on the screen at any angle of deflection. Correction magnets 28a and 2~b are glued to the yoke in an attempt to compensate for aberration~ in the image on the screen resulting from imperfections in the yoke.
The focus of the CRT may be improved by placing a split ring 34 on the neck of the CRT, judiciously choosing the number of ring magnets for the split ring 34, appropriately translating the ring with ring magnets and rota-ting the magnets on the posts of the ring, for reasons which will now be explained. Once the ring is in the desired position on the neck of the CRT it may be glued in ~32~3~ 04942~1 RDF
place and an appropriate d.c. bias voltage applied to the coils oE
the yoke in order to centre the image back on the screen.
As is well understood by those skllled in the art, iE
electrons are injected into a magnetic ~Eield which is perpendicular to their direction of travel, the electrons will move in circles with a radius inversely proportional to the magnetic flux density.
Consequentlyr an electron entering a magnetic field at an angle other than nine-ty degrees will follow a helical trajectory wi-th the axis of the helix parallel to the field lines of the field. A beam of electrons entering a field at an angle will accordingly follow the direction of the field with electrons which were divergent from the direction of the field following a helical trajectory. These helical trajectories keep the beam from spreading radially (so that the beam is "bunched") and hence improve the electron density distribution within a cross-section of the beam.
Figure 3 illustrates a portion of a C~T wi-th a cathode 11~ having an axis 140 ~hich is not aligned with the axis 142 of the focusing electrode 124. ~ccordingly, absent correction, an electron bezm emitted from the cathode will follow the axis 140 oE
the cathode and hence will be off the axis of the focusing electrode, which will result in degraded focus. Since the ring magnets of this invention are polarized across their diameter, the magnetic means of this invention may be used to produce a local magnetic field which makes any desired angle with the axis 140 of the cathode, such as the -field lines 150 of figure 3. The strength of this magnetic Eield may be controlLed by choosing the strength of the magnets on the posts of the ring. If ring magnets are ~32~53~ 04942-1 RDF
placed on the ring and rotated and the split ring translated so as to produce field lines 150, the electrons in the beam will tend to ~ollow the direction of Eield lines 150 toward the axis 142 of the focusing electrode. Thus the magnetic means 30 of the subject invention may be used to correct for axial mis-alignment of the cathode and Eocusing electrode.
Figure 4 illustrates a portion of a CRT showing stray field lines 200 from correction magnets on the yoke of the CRT in the vicinity of the cathode 216 and focusing electrode 224 of the CRT. It may be noted that CRT's are frequently manufactured with short necks which exacerbates the problem of stray fields since the end of the yoke is proximate the cathode area. Since the illustrated stray field induces the electron beam to follow its path, it will be apparent that the stray field moves an electron beam which is on the axis 242 of the focusing electron beam off-axis. In addition, the stray field illustrated by field lines 200 reduces the velocity component oE the beam in a direction toward the screen and parallel with axis 242. Both of these effects degrade focusing. More particularly, the second effec-t will develop local degradation of the image, as the image distance depends on the velocity of the electrons in the beam in a direction -toward the screen. Thus, a slower velocity will shorten the image distance.
The magnetic means of the subject invention may eliminate the degradation in focus caused by these stray fields by applying a field in opposition to the stray field as illustrated in do-tted lines at 2~0. Again this is achieved by appropriately orienting ~2~3~
a judiciously chosen number o~ ring magnets on the split ring oE
the magnetic means.
The subject magnetic means may simultaneously correct for both described defocusing efEects by applying resultant magne-tlc fields which resolve -to the components 150 and 250 of figures 3 and 4.
In practice, the ring and the magnets thereon are appropriately positioned by trial and error. That is, the screen of a CRT may be watched while the ring is translated and rotated and the magnets thereon rotated until focus has improved acceptably.
Application of the fields from the magnetic means of the subject inven-tion have the effect of displacing the entire image on the screen. This may be corrected by applying an appropriate d.c. bias to the yoke by means of variable d.c. voltage source 32.
The efEects illustrated in figures 3 and 4 are small and have been exaggerated in these figures for the purpose of explanation.
Claims (9)
1. A method for improving the focus of an electrostatically focussed CRT having a screen, a neck, and a yoke surrounding the neck comprising the step of:
placing magnetic means around the neck of an electrostatically focussed CRT and translating and orienting said magnetic means until the focus of the CRT improves.
placing magnetic means around the neck of an electrostatically focussed CRT and translating and orienting said magnetic means until the focus of the CRT improves.
2. The method of claim 1 including the step of adding a d.c. bias voltage to the yoke of said CRT to centre the image on the screen of said CRT.
3. A method for improving the focus of an electrostatically focussed cathode ray tube having a neck comprising a cathode, cathode electrode, accelerating electrode means, focusing electrode, and a yoke and a screen, comprising the steps of:
(a) placing magnetic means around the neck of an electrostatically focussed cathode ray tube;
(b) translating said magnetic means along the neck of said cathode ray tube and orienting said magnetic means in order to bunch an electron beam emitted from the cathode of said cathode ray tube along the axis of the focusing electrode of said cathode ray tube;
(c) adjusting the strength of the magnetic field of said magnetic means to control the degree of bunching of said electron beam along said axis of said focusing electrode; and (d) introducing a d.c. bias on the yoke of said cathode ray tube in order to centre the image on the screen of said cathode ray tube.
(a) placing magnetic means around the neck of an electrostatically focussed cathode ray tube;
(b) translating said magnetic means along the neck of said cathode ray tube and orienting said magnetic means in order to bunch an electron beam emitted from the cathode of said cathode ray tube along the axis of the focusing electrode of said cathode ray tube;
(c) adjusting the strength of the magnetic field of said magnetic means to control the degree of bunching of said electron beam along said axis of said focusing electrode; and (d) introducing a d.c. bias on the yoke of said cathode ray tube in order to centre the image on the screen of said cathode ray tube.
4. The method of claim 3 wherein the step of orienting said magnetic means to bunch said electron beam at the axis of said focusing electrode comprises orienting said magnetic means to provide a magnetic field making an angle with the path of said electron beam.
5. The method of claim 1 including the step of:
fixing said magnetic means in place on said cathode ray tube after completion of the step of claim 1.
fixing said magnetic means in place on said cathode ray tube after completion of the step of claim 1.
6. In an electrostatically focussed cathode ray tube having a neck comprising a cathode, cathode electrode, accelerating electrode means, focusing electrode, and a yoke and a screen, a magnetic means for improving the focus of the cathode ray tube comprising:
a support received by the neck of said cathode ray tube proximate said cathode, said support having means to carry a plurality of magnets in a selectable orientation, said support being translatable along the neck of said cathode ray tube; and at least one magnet carried by said support.
a support received by the neck of said cathode ray tube proximate said cathode, said support having means to carry a plurality of magnets in a selectable orientation, said support being translatable along the neck of said cathode ray tube; and at least one magnet carried by said support.
7. A magnetic means for use in improving the focus of an electrostatically focussed cathode ray tube having a neck comprising a cathode and a focusing electrode comprising the following:
a support for translatable reception by the neck of an electrostatically focussed cathode ray tube proximate the cathode of said cathode ray tube, said support having means to carry a plurality of magnets in a selectable orientation; and at least one magnet carried by said support, whereby an electron beam emitted by said cathode may be bunched along the axis of the focusing electrode and orienting said at least one magnet to provide a magnetic field making an angle with the path of said electron beam and the degree of bunching of said electron beam may be controlled by selecting the number of magnets carried by said support.
a support for translatable reception by the neck of an electrostatically focussed cathode ray tube proximate the cathode of said cathode ray tube, said support having means to carry a plurality of magnets in a selectable orientation; and at least one magnet carried by said support, whereby an electron beam emitted by said cathode may be bunched along the axis of the focusing electrode and orienting said at least one magnet to provide a magnetic field making an angle with the path of said electron beam and the degree of bunching of said electron beam may be controlled by selecting the number of magnets carried by said support.
8. A magnetic means for use in improving the focus of an electrostatically focussed cathode ray tube having a neck comprising a cathode and a focusing electrode comprising the following:
a resilient split ring with a plurality of posts radiating therefrom for reception by the neck of an electrostatically focussed cathode ray tube proximate the cathode of said cathode ray tuba î and at least one ring magnet polarized across its diameter for reception by one of said plurality of posts, whereby an electron beam emitted by said cathode may be bunched along the axis of the focusing electrode by translating said split ring along the neck of said cathode ray tube to proximate said axis and orienting said at least one magnet to provide a magnetic field making an angle with the path of said electron beam.
a resilient split ring with a plurality of posts radiating therefrom for reception by the neck of an electrostatically focussed cathode ray tube proximate the cathode of said cathode ray tuba î and at least one ring magnet polarized across its diameter for reception by one of said plurality of posts, whereby an electron beam emitted by said cathode may be bunched along the axis of the focusing electrode by translating said split ring along the neck of said cathode ray tube to proximate said axis and orienting said at least one magnet to provide a magnetic field making an angle with the path of said electron beam.
9. The magnetic means of claim 8 wherein said at least one ring magnet is sized for an interference fit with said posts of said resilient split ring.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000614806A CA1320531C (en) | 1989-09-29 | 1989-09-29 | Crt focus utilising magnetic means |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000614806A CA1320531C (en) | 1989-09-29 | 1989-09-29 | Crt focus utilising magnetic means |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1320531C true CA1320531C (en) | 1993-07-20 |
Family
ID=4140828
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000614806A Expired - Fee Related CA1320531C (en) | 1989-09-29 | 1989-09-29 | Crt focus utilising magnetic means |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1320531C (en) |
-
1989
- 1989-09-29 CA CA000614806A patent/CA1320531C/en not_active Expired - Fee Related
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