Electron gun system with dynamic focus and dynamic convergence

• US 4,701,678 A
• Filed: 10/20/1986
• Issued: 10/20/1987
• Est. Priority Date: 12/11/1985
• Status: Expired due to Fees

• Current Assignee: Zenith Electronics Corporation (LG Corporation)
• Original Assignee: Zenith Electronics Corporation (LG Corporation)
• Inventors: Chiodi, Wayne R., Blacker, Allen P.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US06/921,168
• Time in Patent Office: 365 Days
• Field of Search: 315/382, 315/14, 315/15, 315/16, 315/368, 313/414, 313/412, 313/449
• US Class Current: 315/382
• CPC Class Codes: H01J 2229/4841 Dynamic potentials
• CPC Class Codes: H01J 29/503 Three or more guns, the axes of which lay in a common plane
• CPC Class Codes: H01J 29/51 Arrangements for controlling convergence of a plurality of beams by means of electric field only

Abstract

An electron gun system providing beam convergence is disclosed for use in a color CRT display system. Means including cathode means develop three electron beams, two of which are off-axis with respect to a center axis of the gun. A plurality of electrodes means provide shaping and focusing, and assisting in the converging of the beams at the tube screen. Means are provided for developing and applying to the electrode means a pattern of potentials which form field components in the gaps therebetween; at least one of the electrode means receives a varying dynamic focusing voltage for dynamically focusing the beams as they are deflected across the screen. At least selected ones of the plurality of electrodes means for the off-axis beams are so structured and arranged as to cause a plurality of the field components to be asymmetric and effective to converge the off-axis beams. The strengths of the asymmetric field components vary in response to changes in the dynamic focus voltage. The asymmetric field components according to the invention have such polarity and strength, due to the structuring and arranging of the electrodes, and the application of the pattern of voltages, that a change in the levels of the dynamic focus voltage causes a change in the strength of each of the asymmetric field in a direction effective to additively deflect a common off-axis beam in a common angular direction so as to create a strong dependency of the convergence of the off-axis beams on variations in the focus voltage.

Claims

1. An electron gun system for a color cathode ray tube comprising:

means including cathode means for developing an electron beam;

main focus lens means for receiving said electron beam and forming a focused electron beam spot at the screen of the tube, said main focus lens means having a plurality of electrodes situated on a common axis;

means for developing and applying to said electrodes potentials effective to form one or more focusing field components between said electrodes;

said lens means being so structured and arranged as to cause to be formed between adjacent electrodes at least one focusing field component effective to significantly divert a passed beam from a straight-line path through a predetermined angle; and

means for developing and applying a varying voltage to at least one of said electrodes to cause the strength of said asymmetric field component, and thus said angle by which said beam is diverted, to vary in response to said varying voltage.

2. An electron gun system for a color cathode ray tube having a screen and comprising:

means including cathode means for developing three electron beams;

three main focus lens means for receiving said electron beams and forming three focused electron beam spots at the screen of the tube, said main focus lens means each having a plurality of electrode means spaced along a lens axis parallel to the other lens axes and parallel to a gun central axis, at least two of which lens axes are off-axis with respect to said gun central axis;

means for developing and applying to said electrode means of each of said main focus lens means potentials which form one or more field components between said electrode means;

said off-axis main focus lens means each being so structured and arranged as to cause at least one of said field components to be asymmetrical and effective to converge the off-axis beams in the vicinity of the screen; and

means for developing a voltage having amplitude variations correlated with a scan of the beams across the screen and for applying said voltage to at least one of said electrodes of each of said focus lens means to cause the strength of said asymmetrical field components affecting said off-axis beams, and thus the distance from the gun at which the beams converge, also to vary, whereby in addition to dynamically focusing all the beams, the voltage having amplitude variations also provides a measure of beam convergence.

3. An electron gun system for a color cathode ray tube having a screen and comprising:

means including cathode means for developing three electron beams;

three main focus lens means for receiving said electron beams and forming three focused electron beam spots at the screen of the tube, said main focus lens means each having a plurality of electrode means, including focus electrode means, spaced along a lens axis parallel to the other lens axis and parallel to a gun central axis, at least two of which lens axes are off-axis with respect to said gun central axis;

means for developing and applying to said electrode means of each of said main focus lens means potentials which form one or more field components between said electrode means;

said off-axis main focus lens means each being so structured and arranged as to cause at least one of said field components to be asymmetrical and effective to converge the off-axis beams in the vicinity of the screen; and

means for developing a dynamic focus voltage having amplitude variations correlated with a scan of the beams across the screen, and for applying said voltage to said focus electrode means of each said lens means to cause the focal distance of each of said beams to vary, while at the same time to cause the strength of said asymmetrical field components affecting said off-axis beams, and thus the distance from the gun at which the beams converge, also to vary, whereby in addition to focusing all the beams, the dynamic focusing voltage also provides a measure of beam convergence.

4. A color cathode ray tube system having a screen with multi-color light-emitting phosphor elements thereon, comprising:

means for partially dynamically converging the beams as a function of location of the beams on the screen; and

an electron gun system, comprising;

means including cathode means for developing three electron beams;

three main focus lens means for receiving said electron beams and forming three focused electron beam spots at the screen of the tube, said main focus lens means each having a plurality of electrode means, including focus electrode means, spaced along a lens axis parallel to the other lens axes and a parallel to a gun central axis, at least two of which lens axes are off-axis with respect to said gun central axis;

means for developing and applying to said electrode means of each of said main focus lens means potentials which form one or more field components between said electrode means;

said off-axis main focus lens means each being so structured and arranged as to cause at least one of said field components to be asymmetrical and effective to partially converge the off-axis beams in the vicinity of the screen; and

means for developing a dynamic focus voltage having amplitude variations correlated with a scan of the beams across the screen, and for applying said voltage to focus electrode means of each of said lens means to cause the focal distance of each of said beams to vary, and to cause the strength of said asymmetrical field components affecting said off-axis beams, and thus the distance from the gun at which the beams converge, also to vary, whereby the dynamic focus voltage of the gun system, in addition to focusing all the beams, supplements the partial beam convergence provided by the beam converging means to also provide a measure of beam convergence.

5. A color cathode ray tube system having a screen with multi-color light-emitting phosphor elements thereon, said tube system comprising:

self-converging yoke means;

a three-beam, in-line electron gun system for exciting said phosphor elements, comprising;

means including cathode means for developing said beams;

three main focus lens means for receiving said electron beams and forming three focused electron beam spots at the screen of the tube, said main focus lens means each having a plurality of electrode means, including focus electrode means, spaced along a lens axis parallel to the other lens axes and parallel to a gun central axis, one of which lens axes lies on said central axis, and two of which lens axes are off-axis axis with respect to said gun central axis;

means for developing and applying to said electrode means of each of said main focus lens means potentials which form one or more field components between said electrode means;

said off-axis main focus lens means each being so structured and arranged as to cause at least one of said field components to be asymmetrical and effective to converge the off-axis beams at the screen; and

means for developing a dynamic focus voltage having amplitude variations correlated with a scan of the beams across the screen, and for applying said voltage to focus electrode means of each of said focus lens means to cause the focal distance of each of said beams to vary, and to cause the strength of said asymmetrical field components affecting said off-axis beams, and thus the distance from the gun at which the beams converge, also to vary, whereby the application of the dynamic focus voltage, in addition to focusing all the beams, provides an additional measure of beam convergence to reduce the self-convergence demands on the yoke.

6. A color cathode ray tube system with a substantially flat faceplate and an associated flat tension shadow mask, said faceplate having a screen with multi-color light-emitting phosphor element thereon, said tube system comprising:

self-converging yoke means;

a three-beam electron gun system for exciting said phosphor elements, comprising;

means including cathode means for developing said beams;

three main focus lens means for receiving said electron beams and forming three focused electron beam spots at the screen of the tube, said main focus lens means each having a plurality of electrode means, including focus electrode means, spaced along a lens axis parallel to the other lens axes and parallel to a gun central axis, one of which lens axes lies on said central axis, and two of which lens axes are off-axis with respect to said gun central axis;

means for developing and applying to said electrode means of each of said main focus lens means potentials which form one or more field components between said electrode means;

said off-axis main focus lens means each being so structured and arranged as to cause at least one of said field components to be asymmetrical and effective to converge the off-axis in the vicinity of the screen; and

means for developing a dynamic focus voltage having amplitude variations correlated with a scan of the beams across the screen, and for applying said voltage to focus electrode means of each of said focus lens means to cause the focal distance of each of said beams to vary, and to cause the strength of said asymmetrical field components affecting said off-axis beams, and thus the distance from the gun at which all the beams converge, also to vary, whereby the application of the dynamic focus voltage, in addition to focusing the beams, provides an additional measure of beam convergence to reduce the extraordinary demands on the self-converging yoke which result from the flatness of the faceplate.

7. A color cathode ray tube system with a curved faceplate having a screen with multi-color light-emitting phosphor elements thereon, said tube system comprising:

self-converging yoke means;

a three-beam electron gun system for exciting said phosphor elements, comprising;

means including cathode means for developing said beams;

three main focus lens means for receiving said electron beams and forming three focused electron beam spots at the screen of the tube, said main focus lens means each having a plurality of electrode means, including focus electrode means, spaced along a lens axis parallel to the other lens axes and parallel to a gun central axis, one of which lens axes lies on said central axis, and two of which lens axes are off-axis with respect to said gun central axis;

means for developing and applying to said electrode means of each of said main focus lens means potentials which form one or more field components between said electrode means;

said off-axis main focus lens means each being so structured and arranged as to cause at least one of said field components to be asymmetrical and effective to converge the off-axis beams in the vicinity of the screen; and

means for developing a dynamic focus voltage having amplitude variations correlated with a scan of the beams across the screen, and for applying said voltage to focus electrode means of each of said focus lens means to cause the focal distance of each of said beams to vary, and to cause the strength of said asymmetrical field components affecting said off-axis beams, and thus the distance from the gun at which the beams converge, also to vary, whereby the application of the dynamic focus voltage, in addition to focusing all the beams, provides an additional measure of beam convergence to reduce the demands on the self-converging yoke.

8. For use with a color CRT system, an electron gun system providing beam convergence, comprising:

means including cathode means for developing three electron beams parallel to the center axis of the gun, two of which are off-axis with respect to the center axis;

a plurality of electrode means for each beam for shaping and focusing and assisting in the convergence of said beam at the screen of the tube;

means for developing and applying to said plurality of electrode means a pattern of potentials which form field components in the gaps therebetween;

means for developing and applying a varying dynamic focus voltage to at least one of said electrode means for each beam for dynamically focusing said beams as they are deflected across said screen,

at least selected ones of said plurality of electrode means for each of said off-axis beams being so structured and arranged as to cause a plurality of said field components to be asymmetric and effective to converge said off-axis beams, the strength of said asymmetric field components varying in response to changes in said dynamic focus voltage applied to said electrode means,

said asymmetric field components having such polarity and strength, due to said structuring and arranging of said electrodes, and the application of said pattern of voltages, that a change in the level of said dynamic focus voltage causes a change in the strength of said asymmetric field components in a direction effective to additively deflect a common off-axis beam in a common angular direction so as to create an enhanced dependency of the convergence of said off-axis beams on variations in said focus voltage.

9. For use with a color CRT system having a self-converging yoke, an electron gun system assisting in providing beam convergence to reduce the self convergence demands on the yoke, the system comprising:

means including cathode means for developing three electron beams parallel to the center axis of the gun, two of which are off-axis with respect to the center axis;

a plurality of electrode means for each beam for shaping and focusing and assisting in the convergence of said beam at the screen of the tube;

means for developing and applying to said plurality of electrode means a pattern of potentials to form field components in the gaps between the electrodes;

means for developing and applying a varying dynamic focus voltage to at least one of said electrode means for each beam for dynamically focusing said beams as they are deflected across said screen,

at least selected ones of said plurality of electrode means for each of said off-axis beams being so structured and arranged as to cause a plurality of said field components to be asymmetric and effective to converge said off-axis beams, the strength of said asymmetric field components varying in response to changes in said dynamic focus voltage applied to said electrode means,

said asymmetric field components having such polarity and strength, due to said structuring and arranging of said electrodes, and the application of said pattern of voltages, that a change in the level of said dynamic focus voltage causes a change in the strength of each of said asymmetric field components in a direction effective to additively deflect a common off-axis beam in a common angular direction so as to create a strong dependency of the convergence of said off-axis beams on variations in said focus voltage, whereby a portion of the self convergence desired to be attained in said CRT system is achieved by the converging of said beams as said beams are dynamically focused to thereby reduce the self-convergence demands on the yoke.

10. For use with a color CRT system having a self-converging yoke, an electron gun system assisting in providing beam convergence to reduce the self-convergence demands on the yoke, the system comprising:

means including cathode means for developing three electron beams parallel to the center axis of the gun, two of which are off-axis with respect to the center axis;

main focus lens means for each beam for receiving said beams and for focusing and assisting in the convergence of said beams at the screen of the tube, said focus lens means for each beam including at least focus electrode means and second electrode means adjacent to said focus electrode means on the side away from said cathode means;

third electrode means for each beam located adjacent to said focus electrode means on the side toward said cathode means;

means for developing and applying to said focus electrode means and to said second and third electrode means a pattern of potentials which form first and second field components in the gaps between said third electrode means and said focus electrode means and between said focus electrode means and said second electrode means, respectively;

means for developing and applying a varying dynamic focus voltage to said focus electrode means for each beam for dynamically focusing said beams as they are deflected across said screen,

said third electrode means and said focus electrode means, and said focus electrode means and said second electrode means for each of said off-axis beams being so structured and arranged as to cause said field components therebetween to be asymmetric and effective to converge said off-axis beams, the strength of said first and second asymmetric field components varying in response to changes in said dynamic focusing voltage applied to said focus electrode,

said asymmetric field components having such polarity and strength, due to said structuring and arranging of said electrodes, and the application of said pattern of voltages, that a change in the level of said dynamic focus voltage causes a change in the strength of each of said asymmetric field components in a direction effective to additively deflect a common off-axis beam in a common angular direction so as to create a strong dependency of the convergence of said off-axis beams on variations in said focus voltage, whereby a portion of the self convergence desired to be attained in said CRT system is achieved by the converging of said beams as said beams are dynamically focused to thereby reduce the self-convergence demands on the yoke.

11. For use with a color CRT system having self-converging yoke, an electron gun system assisting in providing beam convergence to reduce the self-convergence demands on the yoke, the system comprising:

means including cathode means for developing three electron beams parallel to a center axis of the gun, two of which are off-axis with respect to the center axis;

main focus lens means for each beam for receiving said beams and for focusing and assisting in the convergence of said beams at the screen of the tube, said main focus lens means for each beam including at least focus electrode means and second electrode means adjacent to said focus electrode means on the side away from said cathode means;

third electrode means for each beam located adjacent to said focus electrode means on the side toward said cathode means;

means for developing and applying to said focus electrode means and to said second and third electrode means a pattern of potentials which form first and second field components in the gaps between said third electrode means and said focus electrode means and between said focus electrode means and said second electrode means, respectively;

means for developing and applying a varying dynamic focus voltage to said focus electrode means for each beam for dynamically focusing said beams as they are deflected across said screen,

the addressing faces and/or apertures of said third electrode means and said focus electrode means, and the addressing faces and/or apertures of said focus electrode means and said second electrode means for each of said off-axis beams being so structured and arranged as to cause said asymmetric field components therebetween to be asymmetric and effective to converge said off-axis beams, the strength of said first and second asymmetric field components varying in response to changes in said dynamic focusing voltage applied to said focus electrode,

said asymmetric field components having such polarity and strength, due to said structuring and arranging of said electrodes, and the application of said pattern of voltages, that a change in the level of said dynamic focus voltage cause a change in the strength of each of said asymmetric field components in a direction effective to additively deflect a common off-axis beam in a common angular direction so as to create a strong dependency of the convergence of said off-axis beams on variations in said focus voltage, whereby a portion of the self convergence desired to be attained in said CRT system is achieved by the converging of said beams as said beams are dynamically focused to thereby reduce the self-convergence demands on the yoke.

12. The color CRT display system according to claim 11 wherein said addressing faces are parallel and angled relative to said central axis so as to create said asymmetry in field components.

13. The color CRT display system according to claim 11 wherein at least one of said asymmetric field components is created by the offsetting of said apertures.

14. The color CRT display system according to claim 11 wherein at least one aperture adjacent to one of said asymmetric field components is offset from said central axis to create the asymmetric field, and wherein the addressing faces of the electrodes adjacent to the other asymmetric field components are parallel and angled relative to said central axis to create said other asymmetric field.

15. For use with a color CRT system having a self-converging yoke, an electron gun system having a three-element extended field main focus lens, said gun system assisting in providing beam convergence to reduce the self-convergence demands on the yoke, the system comprising:

means including cathode means for developing three electron beams parallel to the center axis of the gun, two of which are off-axis with respect to the center axis;

main focus lens means for each beam for receiving said beams and for focusing and assisting in the convergence of said beams at the screen of the tube, said focus lens means for each beam including at least focus electrode means, anode electrode means, and at least one intermediate electrode situated between said focus electrode means and said anode electrode means;

prefocus electrode means for each beam located adjacent to said focus electrode means on the side toward said cathode means;

means for developing and applying to said prefocus electrode means, said focus electrode means, said anode electrode means and said intermediate electrode means, a pattern of potentials which form first and second field components in the gaps between said prefocus electrode means and said focus electrode means, and between said focus electrode means and said intermediate electrode means, respectively;

means for developing and applying a varying dynamic focus voltage to said focus electrode means for each beam for dynamically focusing said beams as they are deflected across said screen,

said prefocus electrode means and said focus electrode means, and said focus electrode means and said intermediate electrode means for each of said off-axis beams being so structured and arranged as to cause said field components therebetween to be asymmetric and effective to converge said off-axis beams, the strength of said first and second asymmetric field components varying in response to changes in said dynamic focusing voltage applied to said focus electrode,

said asymmetric field components having such polarity and strength, due to said structuring and arranging of said electrodes, and the application of said pattern of voltages, that a change in the level of said dynamic focus voltage causes a change in the strength of each of said asymmetric field components in a direction effective to additively deflect a common off-axis beam in a common angular direction so as to create a strong dependency of the convergence of said off-axis beams on variations in said focus voltage, whereby a portion of the self convergence desired to be attained in said CRT system is achieved by the converging of said beams as said beams are dynamically focused to thereby reduce the self-convergence demands on the yoke.

16. For use with a color CRT system having a self-converging yoke, an electron gun system having a four-element main focus lens, said gun system assisting in providing beam convergence to reduce the self-convergence demands on the yoke, the system comprising:

means including cathode means for developing three electron beams parallel to the center axis of the gun, two of which are off-axis with respect to the center axis;

main focus lens means for each beam for receiving said beams and for focusing and assisting in the convergence of said beams at the screen of the tube, said focus lens means for each beam including at least a first, second, third, and fourth electrode means with prefocus electrode means for each beam located adjacent to said first electrode means on the side toward said cathode means;

means for developing and applying to said electrode means a pattern of potentials which form field components in the gaps therebetween, said pattern of potentials following the relationship;

first electrode means--medium;

second electorde means--low;

third electrode means--medium;

fourth electrode means--high;

means for developing and applying a varying dynamic focus voltage to said second electrode means for each beam for dynamically focusing said beams as they are deflected across said screen,

said first electrode means and said second electrode means, and said second electrode means and said third electrode means for each of said off-axis beams being so structured and arranged as to cause said field components therebetween to be asymmetric and effective to converge said off-axis beams, the strength of said asymmetric field components varying in response to changes in said dynamic focusing voltage applied to said focus electrode,

said asymmetric field components having such polarity and strength, due to said structuring and arranging of said electrodes, and the application of said pattern of voltages, that a change in the level of said dynamic focus voltage causes a change in the strength of each of said asymmetric field components in a direction effective to additively deflect a common off-axis beam in a common angular direction so as to create a strong dependency of the convergence of said off-axis beams on variations in said focus voltage, whereby a portion of the self convergence desired to be attained in said CRT system is achieved by the converging of said beams as said beams are dynamically focused to thereby reduce the self-convergence demands on the yoke.