Astigmatism correction for electron beam devices

Claim 2

A circuit for correcting astigmatism in an electron beam deflection system comprising, in combination; means for applying to said electron beam deflection system an astigmatism correction deflection field which substantially fully compensates for astigmatism at a plurality of discrete, selected in advance positions of the beam; and means responsive to voltages indicative of the electron beam position for changing the value of the astigmatism deflection field as the electron beam moves as a function of its relative distances from a plurality of said discrete positions.

Claim 3

A circuit for correcting astigmatism in an electron beam deflection system comprising, in combination: means for applying to said electron beam deflection system a main deflection field for deflecting the electron beam; means for separately applying to said electron beam deflection system an astigmatism correction field which substantially fully compensates for astigmatism at a plurality of discrete, selected in advance positions of the beam, said means including a matrix of impedance means, each such means corresponding to an electron beam position; and means including said matrix of impedance means responsive to voltages indicative of the beam position for changing the value of the deflection field as the electron beam moves as a function of its relative distances from a plurality of said discrete positions.

Claim 4

A circuit for correcting astigmatism in an electron beam deflection system comprising, in combination: means for applying to said electron beam deflection system a main deflection field for deflecting the electron beam; means for separately applying to said electron beam deflection system an astigmatism correction field which substantially fully compensates for astigmatism at a plurality of discrete, selected in advance positions of the beam, said means including a matrix of impedance means, each such means corresponding to an electron beam position; and means including said matrix of impedance means responsive to voltages indicative of the beam position for changing the value of the deflection field as the electron beam moves as a function of its relative distances from a plurality of said discrete positions.

Claim 5

An arrangement for correcting astigmatism in a magnetically deflected cathode-ray tube comprising, in combination: a main deflection yoke on said cathode-ray tube; astigmatism correction coils on said cathode-ray tube; means for applying deflection currents to said yoke for deflecting said electron beam; and an arbitrary function generator responsive to said deflection currents for applying to said astigmatism correction coils correction currents for correcting astigmatism of said electron beam at a plurality of discrete, known in advance positions of said beam.

Claim 6

An arrangement for correcting astigmatism in a magnetically deflected cathode-ray tube comprising, in combination: a main deflection yoke on said cathode-ray tube; astigmatism correction coils on said cathode-ray tube; means for applying deflection currents to said yoke for deflecting said electron beam; and an arbitrary function generator responsive to said deflection currents for applying to said astigmatism correction coils correction currents for correcting astigmatism of said electron beam at a plurality of discrete, known in advance positions of said beam.

Claim 7

An arrangement set forth in claim 3, wherein said arbitrary function generator includes a summing matrix responsive to currents derived from said deflection currents for producing correction currents of values intermediate those produced at said discrete positions of said beam when said beam is intermediate said discrete positions.

Claim 8

A circuit for deriving from a sweep voltage a plurality of waves comprising, in combination: a constant current source; a plurality of active elements, each having a conduction path, said paths being connected at one end to said constant current source and the other end of each path serving as an output terminal, each such element having also a control electrode for controlling the conductivity of its conduction patH; a bias network for applying to said control electrodes successively higher values of bias; a second network receptive of said sweep voltage for applying to said control electrodes successively lower levels of signal in a sense such that the signal tending to cause maximum current through an active element is applied to the active element receiving a value of bias tending to cause minimum current flow through the active element, and the signal tending to cause minimum current through an active element is applied to the active element receiving a value of bias tending to cause maximum current flow through the active element, the initial relative values of said bias and said sweep voltage being such that only said active element receiving said lowest bias initially passes said constant current; and means in said second network responsive to said sweep voltage for successively disconnecting said control electrodes from said second network as said sweep voltage amplitude increases, beginning with the control electrode for the active element receiving the value of bias tending to cause minimum current flow, thereby, in each case, clamping the disconnected control electrode solely to said bias network, whereby each time a control electrode is disconnected, the current passing through the conduction path of its active element starts to decrease and the current passing through the conduction path of the active element receiving the next higher value of bias starts to increase and continues to increase until it draws all of the current supplied by said constant current source.

Claim 9

A circuit for deriving from a sweep voltage a plurality of waves comprising, in combination: a constant current source; a plurality of active elements, each having a conduction path, said paths being connected at one end to said constant current source and the other end of each path serving as an output terminal, each such element having also a control electrode for controlling the conductivity of its conduction patH; a bias network for applying to said control electrodes successively higher values of bias; a second network receptive of said sweep voltage for applying to said control electrodes successively lower levels of signal in a sense such that the signal tending to cause maximum current through an active element is applied to the active element receiving a value of bias tending to cause minimum current flow through the active element, and the signal tending to cause minimum current through an active element is applied to the active element receiving a value of bias tending to cause maximum current flow through the active element, the initial relative values of said bias and said sweep voltage being such that only said active element receiving said lowest bias initially passes said constant current; and means in said second network responsive to said sweep voltage for successively disconnecting said control electrodes from said second network as said sweep voltage amplitude increases, beginning with the control electrode for the active element receiving the value of bias tending to cause minimum current flow, thereby, in each case, clamping the disconnected control electrode solely to said bias network, whereby each time a control electrode is disconnected, the current passing through the conduction path of its active element starts to decrease and the current passing through the conduction path of the active element receiving the next higher value of bias starts to increase and continues to increase until it draws all of the current supplied by said constant current source.

Claim 10

A circuit as set forth in claim 5, wherein said active elements comprise transistors.

Claim 11

A circuit as set forth in claim 6, wherein said transistor are all in a single integrated circuit package.

Claim 12

A circuit as set forth in claim 5, wherein said bias network comprises a plurality of impedance elements connected in series between two terminals of a direct current source.

Claim 13

A circuit as set forth in claim 8, wherein said impedance elements comprise Zener diodes connected to conduct in the forward direction.

Claim 14

A circuit as set forth in claim 5, wherein said last-named means comprises a plurality of normally conducting diodes coupling said bias network to said control electrodes.

Claim 15

A circuit for correcting astigmatism in an electron beam deflection system comprising, in combination: means responsive to vertical and horizontal sweep waves for applying to said electron beam deflection system a main deflection field for deflecting the electron beam; means for deriving from each horizontal sweep wave a group of successive first sweep waves, each corresponding to a different amplitude increment of the horizontal sweep wave; means for deriving from each vertical sweep wave a group of successive second sweep waves, each corresponding to a different amplitude increment of the vertical sweep wave; a matrix of impedance means arranged in columns and rows, each impedance means corresponding to a discrete electron beam position; means applying the respective first sweep waves to the respective rows of said matrix; and means responsive to voltages at the columns of said matrix and to said second sweep waves for separately applying to said electron beam deflection system an astigmatism correction field which substantially fully compensates for astigmatism at the plurality of discrete positions of said electron beam corresponding to the elements of said array and for changing the value of the deflection field as the electron beam moves, as a function of its relative distances from a plurality of said discrete positions.

Claim 16

A circuit for correcting astigmatism in an electron beam deflection system comprising, in combination: means responsive to vertical and horizontal sweep waves for applying to said electron beam deflection system a main deflection field for deflecting the electron beam; means for deriving from each horizontal sweep wave a group of successive first sweep waves, each corresponding to a different amplitude increment of the horizontal sweep wave; means for deriving from each vertical sweep wave a group of successive second sweep waves, each corresponding to a different amplitude increment of the vertical sweep wave; a matrix of impedance means arranged in columns and rows, each impedance means corresponding to a discrete electron beam position; means applying the respective first sweep waves to the respective rows of said matrix; and means responsive to voltages at the columns of said matrix and to said second sweep waves for separately applying to said electron beam deflection system an astigmatism correction field which substantially fully compensates for astigmatism at the plurality of discrete positions of said electron beam corresponding to the elements of said array and for changing the value of the deflection field as the electron beam moves, as a function of its relative distances from a plurality of said discrete positions.

Claim 17

In the combination as set forth in claim 11, said means responsive to said vertical and horizontal sweep waves comprising the main deflection means for said electron beam and the last-named means comprising a second deflection means independent of said main deflection means.