EP0061934A1 - Improved lateral convergence correction system - Google Patents

Improved lateral convergence correction system Download PDF

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Publication number
EP0061934A1
EP0061934A1 EP82301697A EP82301697A EP0061934A1 EP 0061934 A1 EP0061934 A1 EP 0061934A1 EP 82301697 A EP82301697 A EP 82301697A EP 82301697 A EP82301697 A EP 82301697A EP 0061934 A1 EP0061934 A1 EP 0061934A1
Authority
EP
European Patent Office
Prior art keywords
coils
beams
deflection system
field
convergence
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.)
Withdrawn
Application number
EP82301697A
Other languages
German (de)
English (en)
French (fr)
Inventor
Clayton C. Wahlquist
Archie M. Barter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tektronix Inc
Original Assignee
Tektronix Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Tektronix Inc filed Critical Tektronix Inc
Publication of EP0061934A1 publication Critical patent/EP0061934A1/en
Withdrawn legal-status Critical Current

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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
    • H01J29/70—Arrangements for deflecting ray or beam
    • H01J29/701—Systems for correcting deviation or convergence of a plurality of beams by means of magnetic fields at least
    • H01J29/702—Convergence correction arrangements therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2229/00—Details of cathode ray tubes or electron beam tubes
    • H01J2229/56—Correction of beam optics
    • H01J2229/568—Correction of beam optics using supplementary correction devices
    • H01J2229/5681—Correction of beam optics using supplementary correction devices magnetic
    • H01J2229/5687—Auxiliary coils

Definitions

  • the present invention relates generally to deflection convergence systems for multi-gun shadow mask cathode-ray tubes (CRTs), and more particularly to an improved lateral convergence system for such tubes.
  • CRTs shadow mask cathode-ray tubes
  • the color CRTs used in most present-day television and similar color image display systems have three electron guns -- one for each of three primary colors (red, green and blue).
  • the guns are disposed symmetrically in a triangular or "delta" arrangement around the central axis of the tube, and generate individual electron beams that pass through small holes in a shadow mask positioned between the guns and a cathodoluminescent display screen.
  • the display screen is formed of three color phosphors deposited in a regular pattern of dots on the inner face of the CRT. The relative locations of the phosphor deposits and shadow mask apertures is such that, ideally, each electron beam strikes only the deposits of its respective color.
  • Static convergence may be achieved by applying fixed magnetic fields to one or more of the beams using suitable external magnets.
  • suitable waveforms generated in synchronization with the horizontal and vertical deflection signals are applied to individual red, green and blue convergence coils mounted on the CRT neck. The currents produced in these coils by suitable drivers move each beam radially to achieve dynamic convergence.
  • a fourth convergence waveform may be applied to a dynamic lateral convergence coil assembly to shift one beam (usually the blue beam) horizontally relative to the others.
  • Such "dynamic blue lateral" convergence is particularly needed with high resolution shadow-mask CRTs, because of the superior convergence accuracy they require.
  • a general object of the present invention is to provide an improved lateral convergence correction system for a delta-gun shadow mask CRT.
  • a more specific object of the invention is to provide a delta-gun CRT electron beam convergence system capable of shifting one beam laterally without substantial movement of the other two beams.
  • Another object of the invention is to provide a lateral convergence coil assembly of relatively simple construction.
  • a convergence correction system that includes three series-connected lateral convergence coils arranged to provide a vertically-oriented magnetic field in the path of the blue beam and essentially zero magnitude fields in the paths of the red and green beams.
  • FIG. 1 a cross-sectional view of a delta-gun CRT neck at the location of the lateral convergence coils is shown in FIG. 1.
  • Three electron guns (not shown) within neck 10 of the CRT, arranged symmetrically around its central axis 12, emit electron beams that travel along paths 14, 16 and 18 through the neck.
  • the blue beam will be assumed to travel along path 14, the red beam along path 16 and the green beam along path 18.
  • the three coils are connected in series electrically, and are disposed with their planes oriented along the tube's central axis as shown.
  • Coil 20 is mounted directly above the blue beam, and is oriented vertically so that it adds only a vertical component to the magnetic field in the path 14 of the beam.
  • Coils 22 and 24 have an equal number of turns, and.are arranged symmetrically relative to coil 20 (and are thus symmetrical about the vertical plane containing coil 20 and beam path 14). The horizontal components of their fields thus cancel each other in the vertical direction.
  • 'Unipotential field lines 26 show the net magnetic field produced by coils 20, 22 and 24.
  • Coil 20 has a greater number of turns than coils 22 and 24, and thus has a pole strength that is higher by a factor K.
  • the angle theta (e) between coil 20 and each of coils 22 and 24, the angle beta (s) between a radial at angle e and the plane of coil 22 (or 24) and pole strength coefficient K are adjusted to provide nulls in the magnetic fields surrounding beam paths 16 and 18.
  • FIG. 1 a computer-calculated plot of the field strengths produced by a lateral convergence coil assembly according to the present invention, shows more clearly how the field is effectively nulled at path locations 16 and 18 through which the red and green beams travel.
  • FIG. 3 shows a suitable electrical circuit for driving lateral convergence coils 20, 22 and 24.
  • Horizontal and vertical scanning signals which are typical synchronized ramp signals of different frequencies, are applied to the X and Y input terminals, and converted into a suitable convergence signal, such as a parabola signal, by a waveform converter 30.
  • the convergence signal is amplified by a linear class B transconductance output amplifier 32, which includes symmetrically-connected transistors 38 and 38', 40 and 40', 42 and 42', input resistor 44, feedback resistors 46 and 46', controllable current source 34 and anti-saturation circuit 36.
  • Controllable current source 34 includes PNP transistor 52 and variable resistor 54 to provide a controllable output bias current depending on the setting of the variable resistor.
  • the output current is shared by input stage transistors 38, 38' to drive intermediate stage emitter-follower transistors 40, 40' which drive output stage common emitter transistors 42, 42'.
  • First, second and third coils 20, 22 and 24 are serially connected between the collectors of transistors 42, 42' and voltage source +V 3 .
  • Anti-saturation circuit 36 includes back-to-back diodes 58, 58', which are respectively connected to the collectors of transistors 42, '42'.
  • the common junction of diodes 58, 58' is connected to reference voltage source +V 1 , through diodes 60.
  • Intermediate emitter-follower transistors 40, 40' may be deleted to simplify the circuit if transient signals are not included in the input signal. However, the emitter follower stage is used in this embodiment to improve the circuit response.
  • the circuit operates as follows.
  • the convergence control signal from waveform converter 30 is applied to input resistor 44 of amplifier 32.
  • Input stage transistors 38, 38' and current source 34 constitute a conventional differential amplifier.
  • transistor 42' When the input signal to amplifier 32 is negative, transistor 42' is reverse biased or non-conducting, and the left-hand side of amplifier 32 including transistors 38, 40 and 42 and feedback resistor 46 operates as a conventional operational amplifier to develop the corresponding output voltage on the emitter of NPN transistor 42.
  • This output voltage is given by (-R 46 /R 44 ) e in and causes the signal current to flow in resistor 50.
  • Most of the signal current flows into the emitter and collector of transistor 42 and then in one direction through the left-hand side of convergence coils 22, 24 and 20.
  • Diode 58' in anti-saturation circuit 36 prevents'the collector voltage of transistor 42 from decreasing substantially below the supply voltage V (e.g., +5 volts), thereby avoiding saturation of transistor 42, which is detrimental to high speed
  • transistor 42 When the input signal to amplifier 32 is posi-' tive, transistor 42 is non-conducting and transistor 38 and all the right hand side circuit section including transistors 38', 40' and 42' are activated to form a noninverting amplifier. As the input signal increases in a positive direction, less current flows in transistor 38 and more current in transistor 38', thereby increasing the base voltage and, in turn, the emitter voltage of transistor 40'. As a result, more collector-emitter current flows in output stage transistor 42' and in an opposite direction through the right side of convergence coils 20, 24 and 22.
  • the symmetrical circuit arrangement of amplifier 32 ensures that the drive to the convergence coils is symmetrical.
  • the coils 20, 22, and 24 are connected in series, the coils will be energized equally. Therefore, the position of the zero flux areas around the red and green beam paths will not be altered with changes in the current through them. The amount or degree of energization of the three convergence coils will effect only the lateral position of the blue beam.
  • the lateral convergence control apparatus of the present invention is very simple in construction and allows one beam (i.e., the blue beam) to be shifted laterally without affecting the other two beams. This avoids problems inherent in prior art approaches that attempt to shift the red and green beams in a direction opposite to the movement of the blue beam.
  • the three coils may be identical if the pole strength of one of the three coils is controlled by any other external means.
  • the driving circuit for the convergence coils may be of any conventional design.

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  • Video Image Reproduction Devices For Color Tv Systems (AREA)
EP82301697A 1981-03-31 1982-03-31 Improved lateral convergence correction system Withdrawn EP0061934A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP4624981A JPS57162897A (en) 1981-03-31 1981-03-31 Lateral convergence controller
JP46249/81 1981-03-31

Publications (1)

Publication Number Publication Date
EP0061934A1 true EP0061934A1 (en) 1982-10-06

Family

ID=12741878

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82301697A Withdrawn EP0061934A1 (en) 1981-03-31 1982-03-31 Improved lateral convergence correction system

Country Status (3)

Country Link
EP (1) EP0061934A1 (enrdf_load_stackoverflow)
JP (1) JPS57162897A (enrdf_load_stackoverflow)
CA (1) CA1210873A (enrdf_load_stackoverflow)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3307067A (en) * 1964-04-16 1967-02-28 Motorola Inc Dynamic blue lateral correction system
DE1290174B (de) * 1967-09-08 1969-03-06 Philips Patentverwaltung Schaltungsanordnung zur seitlichen Einjustierung von Elektronenstrahlen in einer Farbfernsehbildwiedergaberoehre
US3781731A (en) * 1973-03-23 1973-12-25 L Poel Purity and blue lateral assembly for delta beam type cathode ray tube

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5043630U (enrdf_load_stackoverflow) * 1973-08-22 1975-05-02

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3307067A (en) * 1964-04-16 1967-02-28 Motorola Inc Dynamic blue lateral correction system
DE1290174B (de) * 1967-09-08 1969-03-06 Philips Patentverwaltung Schaltungsanordnung zur seitlichen Einjustierung von Elektronenstrahlen in einer Farbfernsehbildwiedergaberoehre
US3781731A (en) * 1973-03-23 1973-12-25 L Poel Purity and blue lateral assembly for delta beam type cathode ray tube

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
IBM JOURNAL OF RESEARCH AND DEVELOPMENT, vol. 24, no. 5, September 1980, New York J. S. BEETESON et al. " Digital system for convergence of three-beam-high- resolution color data displays " Pages 598-611 * Abstract * *
RADIOSCHAU,vol. 11, 1966, Erbverlag, Vienna M. KOUBEK " Farbfernsehtechnik (IV) " * Page 594, fig. 27 ; page 595, left column " Lateralmagnet " * *

Also Published As

Publication number Publication date
CA1210873A (en) 1986-09-02
JPS57162897A (en) 1982-10-06
JPH0153557B2 (enrdf_load_stackoverflow) 1989-11-14

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19830912

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Inventor name: WAHLQUIST, CLAYTON C.

Inventor name: BARTER, ARCHIE M.