Cathode ray tube dynamic character correction circuit

Claim 2

Correction apparatus for use in a cathode ray tube display system including a cathode ray tube having major horizontal deflection and major and minor vertical deflection driver circuits operative to generate major and minor positioning waveforms for driving major horizontal and major and minor vertical coils coupled to said tube for deflecting the electron beam along a horizontal line and a vertical direction wherein said minor vertical deflection driver circuits generate a high frequency pulse waveform for producing character writing strokes for said line, said correction apparatus comprising: input circuit means coupled to said major horizontal coil for generating a time position waveform in synchronism with said major horizontal waveform; generator means having an input terminal and an output terminal, said input terminal being coupled to said input circuit means, said generating means being responsive to said time position waveform to generate a triangular voltage waveform at said output terminal; and, output circuit means coupled to said output terminal of said generating means and to said minor vertical driver deflection circuits for applying said triangular voltage waveform to said minor vertical coil for dynamically varying the deflection current through said coil in accordance with said voltage waveform from a maximum value to a minimum value and from said minimum value to said maximum value at a predetermined linear rate during the period of said time position waveform to establish a uniform height for each of said writing strokes.

Claim 3

The correction apparatus of claim 1 wherein said generator means includes: comparator means having an input terminal and an output terminal, said input terminal being coupled to said input circuit means, said comparator means being responsive to said time position waveform to produce a square wave waveform for dividing in half the time interval defined by said time position waveform; and, integrator means having at least one input terminal and an output terminal, said input terminal being arranged to receive said square wave waveform and said integrator means being responsive to said square wave waveform to produce said triangular voltage waveform whose amplitude varies at said predetermined rate at said output terminal for transfer to said input terminal of said generator.

Claim 4

The correction apparatus of claim 2 wherein said comparator means is arranged to operate as a zero-crossing detector circuit and produces said square wave waveform having a period corresponding to said time position waveform.

Claim 5

The correction apparatus of claim 2 wherein said integrator means includes: amplifier means having an inverting terminal and a non-inverting terminal, said inverting terminal being connected to said comparator means; capacitor means connected between said output terminal and said input terminal of said amplifier means; and, adjustable slope correction means connected between said output terminal of said comparator means and said inverting terminal of said amplifier means, said slope correction means adjusted to selected said predetermined rate so as to have the height of each said character writing strokes approximately the same.

Claim 6

The correction apparatus of claim 3 wherein said generator means further includes: height control means connected in common with said output terminal of said comparator means and said input terminal of said integrator means, said height control means being responsive to said square wave waveform to establish a predetermined maximum amplitude for said square wave waveform applied to said input terminal of said integrator means.

Claim 7

The correctiOn apparatus of claim 4 wherein said adjustable slope correction means includes: variable resistor means coupled at one end to said inverting terminal of said amplifier means and at the other end to a reference potential, the value of said resistor means being selected to provide a predetermined time constant for said integrator means establishing said predetermined rate.

Claim 8

The correction apparatus of claim 1 wherein said input means includes: resistor means coupled at one end to said horizontal deflection coil and at the other end to a reference potential so as to produce said positional waveform.

Claim 9

In a display system including a wide deflection angle cathode ray tube, horizontal, vertical and character positioning coils and means for driving said horizontal, vertical and character positioning coils respectively with horizontal, vertical and character pulse positioning signals for establishing the location of character segments for a line of characters to be displayed by said tube wherein said character positioning signals causes a plurality of ramp strokes for a number of time intervals for each character segment, a correction apparatus for compensating for distortion in the characters formed at the extremities of the face of the tube of said line larger in height than the characters formed at the center by differences between the centers of deflection said vertical and character positioning coils, said correction apparatus comprising: circuit means coupled to said horizontal positioning coil for deriving a waveform in synchronism with said horizontal positioning signal; function generating means having an input terminal and an output terminal, said input terminal being coupled to said circuit means, said function generating means being responsive to said derived waveform to generate a triangular voltage waveform at said output terminal synchronized with said horizontal positioning signal so that the peak of said triangular waveform coincides with start of said waveform; and, output means coupled to said output terminal of said function generating means and to said character positioning coil for applying said triangular waveform to vary dynamically in accordance with said triangular voltage the height of said ramp strokes for each character segment of said line during intervals established by said character positioning signal so as to provide approximately the same character height for all the ramp character strokes of a line.

Claim 10

In a display system including a wide deflection angle cathode ray tube, horizontal, vertical and character positioning coils and means for driving said horizontal, vertical and character positioning coils respectively with horizontal, vertical and character pulse positioning signals for establishing the location of character segments for a line of characters to be displayed by said tube wherein said character positioning signals causes a plurality of ramp strokes for a number of time intervals for each character segment, a correction apparatus for compensating for distortion in the characters formed at the extremities of the face of the tube of said line larger in height than the characters formed at the center by differences between the centers of deflection said vertical and character positioning coils, said correction apparatus comprising: circuit means coupled to said horizontal positioning coil for deriving a waveform in synchronism with said horizontal positioning signal; function generating means having an input terminal and an output terminal, said input terminal being coupled to said circuit means, said function generating means being responsive to said derived waveform to generate a triangular voltage waveform at said output terminal synchronized with said horizontal positioning signal so that the peak of said triangular waveform coincides with start of said waveform; and, output means coupled to said output terminal of said function generating means and to said character positioning coil for applying said triangular waveform to vary dynamically in accordance with said triangular voltage the height of said ramp strokes for each character segment of said line during intervals established by said character positioning signal so as to provide approximately the same character height for all the ramp character strokes of a line.

Claim 11

In a display system including a wide deflection angle cathode ray tube, horizontal, vertical and character positioning coils and means for driving said horizontal, vertical and character positioning coils respectively with horizontal, vertical and character pulse positioning signals for establishing the location of character segments for a line of characters to be displayed by said tube wherein said character positioning signal causes a plurality of ramp strokes for a number of time intervals for each character segment, a correction apparatus for compensating for distortion in the characters forms at the extremities of the face of the tube of said line larger in height than the characters formed at the center by differences between the centers of deflection said vertical and character positioning coils, said correction apparatus comprising: input circuit means coupled to said horizontal positioning coil for deriving a waveform in synchronism with said horizontal positioning signal; function generating means having an input terminal and an output terminal, said input terminal being coupled to said circuit means, said function generating means being responsive to said derived waveform to generate a triangular voltage waveform at said output terminal synchronized with said horizontal positioning signal so that the peak of said triangular waveform coincides with start of said waveform, said function generating means further including; comparator means having an input terminal and an output terminal, said inPut terminal being coupled to said input circuit means, said comparator means being responsive to said time position waveform to produce a square wave waveform for dividing the time interval defined by said time position waveform and, integrator means having at least one input terminal and an output terminal, said input terminal being arranged to receive said square wave waveform and said integrator means being responsive to said square wave waveform to produce at said output terminal said triangular voltage waveform whose amplitude varies at said predetermined rate for transfer to said output terminal of said function generator means; and, output means coupled to said output terminal of said function generating means and to said character positioning coil for applying said triangular waveform to vary dynamically in accordance with said triangular voltage the height of said ramp strokes for each character segment of said line during intervals established by said character positioning signal so as to provide approximately the same character height for all of the ramp character strokes of a line.

Claim 12

In a display system including a wide deflection angle cathode ray tube, horizontal, vertical and character positioning coils and means for driving said horizontal, vertical and character positioning coils respectively with horizontal, vertical and character pulse positioning signals for establishing the location of character segments for a line of characters to be displayed by said tube wherein said character positioning signal causes a plurality of ramp strokes for a number of time intervals for each character segment, a correction apparatus for compensating for distortion in the characters forms at the extremities of the face of the tube of said line larger in height than the characters formed at the center by differences between the centers of deflection said vertical and character positioning coils, said correction apparatus comprising: input circuit means coupled to said horizontal positioning coil for deriving a waveform in synchronism with said horizontal positioning signal; function generating means having an input terminal and an output terminal, said input terminal being coupled to said circuit means, said function generating means being responsive to said derived waveform to generate a triangular voltage waveform at said output terminal synchronized with said horizontal positioning signal so that the peak of said triangular waveform coincides with start of said waveform, said function generating means further including; comparator means having an input terminal and an output terminal, said inPut terminal being coupled to said input circuit means, said comparator means being responsive to said time position waveform to produce a square wave waveform for dividing the time interval defined by said time position waveform and, integrator means having at least one input terminal and an output terminal, said input terminal being arranged to receive said square wave waveform and said integrator means being responsive to said square wave waveform to produce at said output terminal said triangular voltage waveform whose amplitude varies at said predetermined rate for transfer to said output terminal of said function generator means; and, output means coupled to said output terminal of said function generating means and to said character positioning coil for applying said triangular waveform to vary dynamically in accordance with said triangular voltage the height of said ramp strokes for each character segment of said line during intervals established by said character positioning signal so as to provide approximately the same character height for all of the ramp character strokes of a line.

Claim 13

In the system of claim 9 wherein said comparator means is arranged to operate as a zero-crossing detector circuit and produces said square wave waveform having a period corresponding to said time position waveform.

Claim 14

In the system of claim 9 wherein said integrator means includes: amplifier means having an inverting terminal and a non-inverting terminal, said inverting terminal being connected to said comparator means; capacitor means connected between said output terminal and said input terminal of said amplifier means; adjustable slope correction means connected between said output terminal of said comparator means and said inverting terminal of said amplifier means, said slope correction means being adjusted to select said predetermined rate so as to have said height of said character ramp strokes of a line uniform.

Claim 15

In the system of claim 10 wherein said function generator means further includes: height control means connected in common with said output terminal of said comparator means and said input terminal of said integrator means, said height control means being responsive to said square wave waveform to establish a predetermined maximum amplitude for said square wave waveform applied to said input terminal of said integrator means.

Claim 16

In the system of claim 11 wherein said adjustable slope correction means includes: variable resistor means coupled at one end to said inverting terminal of said amplifier means and at the other end to a reference potential, the value of said resistor means being selected to provide a predetermined time constant for said integrator means establishing a rate of height correction corresponding to said predetermined rate.

Claim 17

In the system of claim 10 wherein said input means includes: resistor means coupled at one end to said horizontal deflection coil and at the other end to a reference potential, said resistor means being arranged so as to produce said positional waveform.

Claim 18

A cathode ray tube display system including a cathode ray tube having major horizontal deflection and major and vertical deflection driver circuits operative to generate major and minor positioning waveforms for driving major and minor horizontal and vertical control circuits coupled to said tube for deflecting the electron beam along a horizontal line and in a vertical direction wherein said minor vertical deflection driver circuits generate a high repetition frequency pulse waveform for producing character writing strokes for said line, said horizontal deflection circuits produce a low frequency sawtooth waveform as said major horizontal positioning waveform and said major vertical deflection circuits produce a staircase waveform as said major positioning waveform, said system further including correction apparatus comprising: input circuit means coupled to said major horizontal control circuits for generaTing a time position waveform in synchronism with said major horizontal waveform; function generator means having an input terminal and an output terminal, said input terminal being coupled to said input circuit means, said generating means being responsive to said time position waveform to generate a triangular voltage waveform at said output terminal; and, output circuit means coupled to said output terminal of said generator means and to said minor vertical driver deflection circuits for applying said triangular voltage waveform to said minor vertical circuit with said high frequency pulse for dynamically varying the deflection current through said circuit in accordance with said voltage triangular waveform from a maximum value to a minimum value and from said minimum value to said maximum value at a predetermined linear rate during the period of said time position waveform to establish a maximum uniform height for all of said writing strokes of said line.

Claim 19

A cathode ray tube display system including a cathode ray tube having major horizontal deflection and major and vertical deflection driver circuits operative to generate major and minor positioning waveforms for driving major and minor horizontal and vertical control circuits coupled to said tube for deflecting the electron beam along a horizontal line and in a vertical direction wherein said minor vertical deflection driver circuits generate a high repetition frequency pulse waveform for producing character writing strokes for said line, said horizontal deflection circuits produce a low frequency sawtooth waveform as said major horizontal positioning waveform and said major vertical deflection circuits produce a staircase waveform as said major positioning waveform, said system further including correction apparatus comprising: input circuit means coupled to said major horizontal control circuits for generaTing a time position waveform in synchronism with said major horizontal waveform; function generator means having an input terminal and an output terminal, said input terminal being coupled to said input circuit means, said generating means being responsive to said time position waveform to generate a triangular voltage waveform at said output terminal; and, output circuit means coupled to said output terminal of said generator means and to said minor vertical driver deflection circuits for applying said triangular voltage waveform to said minor vertical circuit with said high frequency pulse for dynamically varying the deflection current through said circuit in accordance with said voltage triangular waveform from a maximum value to a minimum value and from said minimum value to said maximum value at a predetermined linear rate during the period of said time position waveform to establish a maximum uniform height for all of said writing strokes of said line.

Claim 20

A cathode ray tube display system including a cathode ray tube having major horizontal deflection and major and minor vertical deflection driver circuits operative to generate major and minor positioning waveforms for driving major and minor horizontal and vertical control circuits coupled to said tube for deflecting the electron beam along a horizontal line and in a vertical direction wherein said minor vertical deflection driver circuits generate a high repetition frequency pulse waveform for producing character writing strokes for said line, said horizontal deflection circuits produce a low frequency sawtooth waveform as said major horizontal positioning waveform and said major vertical deflection circuits produce a staircase waveform as said major positioning waveform, said system further including correction apparatus comprising: input circuit means coupled to said major horizontal control circuits for generating a time position waveform in synchronism with said major horizontal waveform; function generator means having an input terminal and an output terminal, said input terminal being coupled to said input circuit means, said generating means being responsive to said time position waveform to generate a triangular voltage waveform at said output terminal; output circuit means coupled to said output terminal of said generator means and to said minor vertical driver deflection circuits for applying said triangular voltage waveform to said minor vertical circuit with said high frequency pulse for dynamically varying the deflection current through said circuit in accordance with said voltage triangular waveform from a maximum value to a minimum value and from said minimum value to said maximum value at a predetermined linear rate during the period of said time position waveform to establish a maximum uniform height for all of said writing strokes of said line; and, said minor vertical deflection driver circuits including: a variable voltage source having an output terminal coupled to one end of said minor vertical deflection control circuit for applying a voltage signal of a predetermined amplitude; transistor switching means having an input electrode and first and second output electrodes, said first electrode being coupled to the other end of said minor vertical deflection control circuit, said second output electrode being connected to ground reference potential, said transistor switching means being responsive to the pulse signals of a said high repetition frequency waveform to switch state connecting said other end of said minor vertical deflection control circuit to said ground reference potential so as to produce said high frequency pulse waveform at said circuit; and, means for combining the triangular voltage waveform from said function generator output terminal with the voltage from said output terminal of said variable voltage source and for applying an output signal to said one end of said minor vertical deflection control circuit.

Claim 21

A cathode ray tube display system including a cathode ray tube having major horizontal deflection and major and minor vertical deflection driver circuits operative to generate major and minor positioning waveforms for driving major and minor horizontal and vertical control circuits coupled to said tube for deflecting the electron beam along a horizontal line and in a vertical direction wherein said minor vertical deflection driver circuits generate a high repetition frequency pulse waveform for producing character writing strokes for said line, said horizontal deflection circuits produce a low frequency sawtooth waveform as said major horizontal positioning waveform and said major vertical deflection circuits produce a staircase waveform as said major positioning waveform, said system further including correction apparatus comprising: input circuit means coupled to said major horizontal control circuits for generating a time position waveform in synchronism with said major horizontal waveform; function generator means having an input terminal and an output terminal, said input terminal being coupled to said input circuit means, said generating means being responsive to said time position waveform to generate a triangular voltage waveform at said output terminal; output circuit means coupled to said output terminal of said generator means and to said minor vertical driver deflection circuits for applying said triangular voltage waveform to said minor vertical circuit with said high frequency pulse for dynamically varying the deflection current through said circuit in accordance with said voltage triangular waveform from a maximum value to a minimum value and from said minimum value to said maximum value at a predetermined linear rate during the period of said time position waveform to establish a maximum uniform height for all of said writing strokes of said line; and, said minor vertical deflection driver circuits including: a variable voltage source having an output terminal coupled to one end of said minor vertical deflection control circuit for applying a voltage signal of a predetermined amplitude; transistor switching means having an input electrode and first and second output electrodes, said first electrode being coupled to the other end of said minor vertical deflection control circuit, said second output electrode being connected to ground reference potential, said transistor switching means being responsive to the pulse signals of a said high repetition frequency waveform to switch state connecting said other end of said minor vertical deflection control circuit to said ground reference potential so as to produce said high frequency pulse waveform at said circuit; and, means for combining the triangular voltage waveform from said function generator output terminal with the voltage from said output terminal of said variable voltage source and for applying an output signal to said one end of said minor vertical deflection control circuit.

Claim 22

The system of claim 16 wherein saiD predetermined amplitude of said variable voltage source is adjusted to establish a minimum value for said signal applied to said minor vertical control circuit.