Cathode-ray-tube astigmatism correction apparatus

Claim 2

Astigmatism correction apparatus for an electromagnetically deflected cathode-ray-tube having an electron gun including beam-forming, accelerator and focusing electrodes forming an electron beam and an electromagnetic deflection yoke which establishes two orthogonal deflection fields and deflects said electron beam across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, and wherein said magnetic deflection yoke produces distortion of said electron beam, said apparatus comprising: electrostatic correction means disposed along said electron beam and through which said electron beam passes before reaching said deflection yoke, said electrostatic correction means, comprising at least first, second and third plate-form electrodes spaced along the direction of the electron beam and each having an aperture through which said beam passes, the aperture in the first electrode being non-circular and being elongated in a direction parallel to one of the two deflection fields, the aperture in the third electrode being non-circular and being elongated in a direction intermediate the directions of the two deflection fields, and the aperture in the second electrode, which is disposed between the first and third electrodes, being circular, and means connected to said electrostatic correction means and responsive to the beam deflection signals for varying the electrostatic field produced by said electrostatic correction means to compensate dynamically for the distortion caused by said deflection yoke at a plurality of predetermined locations on said screen.

Claim 3

Astigmatism correction apparatus for an electromagnetically deflected cathode-ray-tube having an electron gun including beam-forming, accelerator and focusing electrodes forming an electron beam and an electromagnetic deflection yoke deflecting said electron beam across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, and wherein said magnetic deflection yoke produces distortion of said electron beam, said apparatus comprising: first, second and third plate-form electrodes spaced along said electron beam and having apertures through which said electron beam passes, the aperture in the second electrode being circular and the apertures in the first and third electrodes being non-circular and angularly displaced relative to each other, and means responsive to the beam deflection signals for dynamically applying separate correction voltages to said first and third electrodes, said correction voltages producing counter-distortion of said electron beam as the result of the non-circularity of the apertures in the first and third electrodes compensating the distortion produced by said deflection yoke at a plurality of predetermined locations on said screen.

Claim 4

Astigmatism correction apparatus for an electromagnetically deflected cathode-ray-tube having an electron gun including beam-forming, accelerator and focusing electrodes forming an electron beam and an electromagnetic deflection yoke deflecting said electron beam across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, and wherein said magnetic deflection yoke produces distortion of said electron beam, said apparatus comprising: first, second and third plate-form electrodes spaced along said electron beam and having apertures through which said electron beam passes, the aperture in the second electrode being circular and the apertures in the first and third electrodes being non-circular and angularly displaced relative to each other, and means responsive to the beam deflection signals for dynamically applying separate correction voltages to said first and third electrodes, said correction voltages producing counter-distortion of said electron beam as the result of the non-circularity of the apertures in the first and third electrodes compensating the distortion produced by said deflection yoke at a plurality of predetermined locations on said screen.

Claim 5

The apparatus according to claim 2 further including means responsive to said beam deflection signals for dynamically applying an error voltage to said focusing electrode to focus said electron beam at said predetermined locations on the screen of said cathode-ray-tube.

Claim 6

Astigmatism correction apparatus for an electromagnetically deflected cathode-ray-tube having an electron gun including beam-forming, accelerator and focusing electrodes forming an electron beam and an electromagnetic deflection yoke deflecting said electron beam across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, and wherein said magnetic deflection yoke produces distortion of said electron beam, said apparatus comprising: a first plate-form electrode in said electron gun, said first electrode having a transversely elongated slot through which said electron beam passes before reaching said deflection yoke, a second plate-form electrode in said electron gun spaced along the path of said electron beam from said first electrode, said second electrode having a circular aperture through which said electron beam passes before reaching said deflection yoke, a third plate-form electrode in said electron gun spaced along the path of said electron beam from said second electrode, said third electrode having a transversely elongated slot through which said electron beam passes before reaching said deflection yoke, said slot in said third electrode being elongated at an angle to the slot in the first electrode, and means responsive to the deflection of said electron beam for applying correction voltages to said first, second and third electrodes counter-distorting the cross section of said electron beam in a compensating sense to the distortion caused by said deflection yoke at a plurality of predetermined locations on the screen of said cathode-ray-tube.

Claim 7

Astigmatism correction apparatus for an electromagnetically deflected cathode-ray-tube having an electron gun including beam-forming, accelerator and focusing electrodes forming an electron beam and an electromagnetic deflection yoke deflecting said electron beam across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, and wherein said magnetic deflection yoke produces distortion of said electron beam, said apparatus comprising: a first plate-form electrode in said electron gun, said first electrode having a transversely elongated slot through which said electron beam passes before reaching said deflection yoke, a second plate-form electrode in said electron gun spaced along the path of said electron beam from said first electrode, said second electrode having a circular aperture through which said electron beam passes before reaching said deflection yoke, a third plate-form electrode in said electron gun spaced along the path of said electron beam from said second electrode, said third electrode having a transversely elongated slot through which said electron beam passes before reaching said deflection yoke, said slot in said third electrode being elongated at an angle to the slot in the first electrode, and means responsive to the deflection of said electron beam for applying correction voltages to said first, second and third electrodes counter-distorting the cross section of said electron beam in a compensating sense to the distortion caused by said deflection yoke at a plurality of predetermined locations on the screen of said cathode-ray-tube.

Claim 8

The apparatus according to claim 4 wherein said voltage applying means comprises means addressable in accordance with said deflection signals for storing values representing the correction voltages appropriate for application to said electrodes for bringing about the counter-distortion at the plurality of predetermined locations on the screen.

Claim 9

The apparatus according to claim 4 wherein the slot in said first electrode is elongated in a direction of one of two orthogonal deflection fields of said deflection yoke, and wherein the slot in said third electrode is elongated in a direction intermediate the direction of the two orthogonal deflection fields of said deflection yoke.

Claim 10

The apparatus according to claim 6 wherein the slot in the third electrode is elongated at an angle of approximately forty-five degrees from the slot in the first electrode.

Claim 11

The apparatus according to claim 4 wherein said voltage applying means applies a voltage to said first electrode which to a first approximation is proportional to the difference of the squares of orthogonal deflection values applied to said deflection yoke, and wherein said voltage applying means further applies a voltage to said third electrode which to a first approximation is proportional to the produce of the deflection values applied to said deflection yoke.

Claim 12

The apparatus according to claim 4 including further apertured electrodes disposed on either side of said first and third electrodes to provide a lensing action with respect to said electron beam in conjunction with said first and third electrodes, said further apertured electrodes and said second electrode each having a substantially constant voltage applied thereto.

Claim 13

The apparatus according to claim 9 wherein the apertures in said further electrodes are circular and aligned with said electron beam.

Claim 14

The apparatus according to claim 4 wherein said voltage applying means includes means for applying a correction voltage to said focus electrode, said correction voltage focusing said beam at the plurality of predetermined locations on the screen of said cathode-ray-tube.

Claim 15

The apparatus according to claim 11 wherein said means for applying the correction voltage to said focus electrode comprises means addressable in accordance with said beam deflection signals for storing values representing the voltages appropriate for application to said focus electrode for bringing about focusing of said beam at the corresponding plurality of locations on the screen of said cathode-ray-tube.

Claim 16

The apparatus according to claim 11 wherein said cathode-ray-tube includes an anode electrode, said first and third electrodes being located between said anode electrode and said focus electrode.

Claim 17

Astigmatism correction apparatus for an electromagnetically deflected cathode-ray-tube having an electron gun including beam-forming, accelerator and focusing electrodes forming an electron beam and an electromagnetic deflection yoke deflecting said electron beam across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, and wherein said magnetic deflection yoke produces distortion of said electron beam, said apparatus comprising: electrostatic correction means disposed along said electron beam and through which said electron beam passes before reaching said deflection yoke, said electrostatic correction means comprising at least first, second and third plate-form electrodes spaced along the direction of the electron beam and each having an aperture through which said beam passes, the aperture in the first electrode being non-circular and being elongated in a first direction, the aperture in the third electrode being non-circular and being elongated in a direction that is oblique to said first direction, and the aperture in the second electrode, which is disposed between the first and third electrodes, being circular, and means for applying predetermined correction voltages to said plate-form electrodes for counter-distorting said beam in a compensating sense to distortion caused by said deflection yoke at one of a plurality of predetermined locations on the screen of the cathode-ray-tube.

Claim 18

Astigmatism correction apparatus for an electromagnetically deflected cathode-ray-tube having an electron gun including beam-forming, accelerator and focusing electrodes forming an electron beam and an electromagnetic deflection yoke deflecting said electron beam across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, and wherein said magnetic deflection yoke produces distortion of said electron beam, said apparatus comprising: electrostatic correction means disposed along said electron beam and through which said electron beam passes before reaching said deflection yoke, said electrostatic correction means comprising at least first, second and third plate-form electrodes spaced along the direction of the electron beam and each having an aperture through which said beam passes, the aperture in the first electrode being non-circular and being elongated in a first direction, the aperture in the third electrode being non-circular and being elongated in a direction that is oblique to said first direction, and the aperture in the second electrode, which is disposed between the first and third electrodes, being circular, and means for applying predetermined correction voltages to said plate-form electrodes for counter-distorting said beam in a compensating sense to distortion caused by said deflection yoke at one of a plurality of predetermined locations on the screen of the cathode-ray-tube.

Claim 19

The apparatus according to claim 14 wherein said means for applying the correction voltages to said electrodes applies the predetermined correction voltages responsive to the deflection of said electron beam, said non-circular apertures each comprising an elongated slot.

Claim 20

Astigmatism correction apparatus for an electromagnetically deflected color cathode-ray-tube having an electron gun structure forming plural electron beams and an electromagnetic deflection yoke deflecting said electron beams across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, said magnetic deflection yoke bringing about convergence of said electron beams, wherein said magnetic deflection yoke produces distortion in one or more of said electron beams, said apparatus comprising: electrostatic correction means disposed along said one or more of said electron beams formed by said electron gun structure, said one or more of said beams passing through said electrostatic correction means before reaching said deflecting yoke, said electrostatic correction means comprising at least first, second and third plate-form electrode means spaced along the direction of the electron beam and each having apertures through which respective electron beams pass, the apertures in the first electrode means each being non-circular and being elongated in a first direction and the apertures in the third electrode means each being non-circular and being elongated in a direction that is oblique to said first direction and the apertures in the second electrode means, which is disposed between the first and third electrode means, being circular, and means connected to said electrostatic correction means for dynamically determining an electrostatic field produced by said correction means for counter-distorting the beams passing therethrough in a compensating sense to the distortion caused by said deflection yoke at a plurality of locations on the screen of said cathode-ray-tube.

Claim 21

Astigmatism correction apparatus for an electromagnetically deflected color cathode-ray-tube having an electron gun structure forming plural electron beams and an electromagnetic deflection yoke deflecting said electron beams across a screen of said cathode-ray-tube in response to beam deflection signals applied to said electromagnetic deflection yoke, said magnetic deflection yoke bringing about convergence of said electron beams, wherein said magnetic deflection yoke produces distortion in one or more of said electron beams, said apparatus comprising: electrostatic correction means disposed along said one or more of said electron beams formed by said electron gun structure, said one or more of said beams passing through said electrostatic correction means before reaching said deflecting yoke, said electrostatic correction means comprising at least first, second and third plate-form electrode means spaced along the direction of the electron beam and each having apertures through which respective electron beams pass, the apertures in the first electrode means each being non-circular and being elongated in a first direction and the apertures in the third electrode means each being non-circular and being elongated in a direction that is oblique to said first direction and the apertures in the second electrode means, which is disposed between the first and third electrode means, being circular, and means connected to said electrostatic correction means for dynamically determining an electrostatic field produced by said correction means for counter-distorting the beams passing therethrough in a compensating sense to the distortion caused by said deflection yoke at a plurality of locations on the screen of said cathode-ray-tube.

Claim 22

The apparatus according to claim 16 wherein said non-circular apertures comprise elongated slots.

Claim 23

The apparatus according to claim 16 wherein said electrode means comprise plural electrodes respectively passing different ones of said electron beams, and wherein said means for determining the electrostatic field produced by said correction means comprises means for applying different voltages to said plural electrodes, said voltage applying means being responsive to beam deflection signals at each of said plurality of locations on the screen of said cathode-ray-tube.

Claim 24

The apparatus according to claim 16 including further electrode means on either side of said electrostatic correction means to provide lensing with respect to said electron beams.

Claim 25

The apparatus according to claim 1, wherein the electrodes of the electron gun include an anode and the electrostatic correction means comprise two additional plate-form electrodes between which the first, second and third electrodes are disposed and each having a circular aperture through which said beam passes, the second electrode and the two additional electrodes all being connected to the anode of the electron gun.

Claim 26

The apparatus according to claim 20, wherein the apertures in the first and third electrodes are transversely elongated slots.

Claim 27

The apparatus according to claim 1, wherein the aperture in the third electrode is elongated at an angle of approximately 45 degrees from the direction of elongation of the aperture in the first electrode.

Claim 28

The apparatus according to claim 2, wherein the electrodes of the electron gun include an anode and the second electrode is connected to the anode, and the apparatus further comprises two additional plate-form electrodes between which the first, second and third electrodes are disposed and each having a circular aperture through which said beam passes, the second electrode and the two additional electrodes all being connected to the anode.

Claim 29

The apparatus according to claim 4, wherein the electrodes of the electron gun include an anode and the second electrode is connected to the anode, and the apparatus further comprises two additional plate-form electrodes between which the first, second and third electrodes are disposed and each having a circular aperture through which said beam passes, the second electrode and the two additional electrodes all being connected to the anode.

Claim 30

The apparatus according to claim 14, wherein the electrodes of the electron gun include an anode and the second electrode is connected to the anode, and the apparatus further comprises two additional plate-form electrodes between which the first, second and third electrodes are disposed and each having a circular aperture through which said beam passes, the second electrode and the two additional electrodes all being connected to the anode.

Claim 31

The apparatus according to claim 16, wherein the electrodes of the electron gun include an anode and the second electrode means is connected to the anode, and the apparatus further comprises two additional plate-form electrode means between which the first, second and third electrode means are disposed and each having circular apertures through which respective electron beams pass, the second electrode means and the two additional electrode means all being connected to the anode.