JPS61289788A - Color cathode ray tube display device - Google Patents

Abstract

PURPOSE:To seldom raise the problem of beam moving by flowing a correction current to a magnetic cancel coil in accordance with the detected value of a magnetic sensor detecting an external magnetic field. CONSTITUTION:Directly after the main current switch of a display device is turned on to degauss a color cathode ray tube 1, a detection quantity available from A/D-converting a detection value Vx is stored in the 1st memory 20 for a short time T. Afterward, the 1st switch 22 is inverted, and an optimum correction current calculated by the cancel coil 6 is conducted. In terms of the correction Vz of a tube axial direction component, the initial magnetic amount Vz is stored in the 2nd memory 28 in the same manner, and an optimum correction current is conducted to the cancel coil 2. The correction table of the interrelationship between the detection values Vx and Vz and the optimum correction current is stored in two ROMs 23 and 31, whereby the optimum correction current can be outputted through the 1st and 2nd D/A converters 24 and 32 and the 3rd and fourth DC amplifiers 25 and 33.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a color cathode ray tube display device which is equipped with means for preventing unnecessary magnetism external to the color cathode ray tube and is used for high quality color displays and the like.

(Prior art) Measures against unnecessary external magnetism such as earth's magnetism for color cathode ray tubes used in this type of display device include providing a magnetic shield plate made of iron plate, silicon steel plate, etc. inside or outside the color cathode ray tube. For cathode ray tubes whose diagonal dimensions are approximately 2 inches or less, the above measures have reached a practical level. As the color cathode ray tube becomes larger, the travel distance of the electron beam increases, and even in an external magnetic field at the geomagnetic level, beam movement problems such as color shift/raster position shift become noticeable.

As a countermeasure to this problem, it has been devised to provide a function to generate a canceling magnetic field that cancels out the external magnetic field, in addition to shielding the external magnetic field.

Figure 8, (2) shows an example of a conventionally used magnetic cancellation method. In the same figure, ■), (
1) is a color cathode ray tube, (2) is a magnetic canceling coil for a bone thin two-way magnetic field, (3> is a DC power supply, (4) is a resistor for current limiting, and (5) is an extreme voltage changeover switch.

In this example, the installer investigates the direction in which the display device is installed, that is, whether the screen of the color cathode ray tube (1) is facing east, west, north, south, or north or south of the shaded zone shown in Figure 4. (2) The switch (5) is set according to K. When the direction is outside the diagonal line zone,
In this example, the switch (5) is set to a neutral state so as not to operate the cancel function.
It is also possible to increase the number of canceling coils (2) to have a canceling function for east-west or vertical magnetic fields, or to make the amount of correction current variable (power source (3) or resistor (4), etc.) variable. In any case, these methods require the installer of the display device to set the switch (5) etc. at the installation location. Furthermore, there was a great deal of doubt as to how accurate correction could be made when the direction and strength of the magnetic field at the installation location were unknown.

This invention was made to solve the above drawbacks.
A color that can automatically perform optimal correction for 1 magnetic cancellation no matter what magnetic boundary conditions it is installed under, and ideally corrects for poor color purity without requiring the installer's intervention. The purpose of the present invention is to provide a cathode ray tube display device.

(Means for Solving the Problems) A color cathode ray tube display device according to the present invention includes a magnetic sensor for detecting an external magnetic field applied to a color cathode ray tube, detects an initial amount of magnetic field before correction, and stores it in memory. is stored, and an optimum correction current corresponding to the detected amount is applied to the canceling coil.

(Function) In this invention, the magnetic sensor detects an external magnetic field. At this time, when the canceling current value calculated from the detected value is energized to the -H canceling coil, the magnetic sensor also synthesizes the canceling correction magnetic field. It will be detected.

Therefore, by storing the initial magnetic field 'Ik (external magnetic field, t) before cancellation correction in memory, the correction amount corresponding to the initial detection value can be automatically applied to the cancellation coil while the display device is operating. A near-ideal Cankill correction will be performed.

(Embodiment of the Invention) FIG. 1 shows an embodiment of a color cathode ray tube display device according to the present invention. In the figure, (1) is a color cathode ray tube, and (2) is an N tube that cancels the magnetic field BZ in the tube axis direction.
/8 cancellation coils (6a) and (6b) are a pair of opposing coils that are connected in series or parallel to each other and constitute an E/W cancellation coil that cancels the magnetic field Bx in the direction perpendicular to the tube axis. (8) is an enclosure such as a cabinet,
(7) is a magnetic sensor for horizontal magnetic field detection. In this embodiment, the filter for canceling the vertical magnetic field By and the magnetic sensor + for detecting the vertical magnetic field By are omitted, but they may be provided if necessary.

FIG. 2 shows an example of a block diagram of the magnetic cancellation correction means of the color cathode ray tube display device according to the present invention.

The magnetic sensor (7) is generally used in electronic controllers, paths, etc., and includes a toroidal type ferrite core (7a) that is easily subject to magnetic saturation, an excitation coil (7b) that generates an annular magnetic field, and a core (7a). Two output filters (7c) and (7d) that are orthogonal to each other in the diametrical direction are wound. With this configuration, from K,
It is possible to detect from which direction and in what magnitude the external magnetic field is coming, and the detected amount is a detected voltage value V proportional to X and the magnetic field amounts BX and BZ of the two-directional components.
x, Vz are obtained.

(9) is an oscillator that sends an alternating current through the driver α ([7b), which generates an alternating magnetic flux during the toroidal type core ('7').
.

(g) are the first and second bandpass filters connected to the output coils (7b) and (7d), respectively;
as are the first and second AC amplifiers, αη are the first and second rectifiers, Q4. (to) is the first and second
This is a DC amplifier.

Since the alternating current magnetic flux changes due to the external magnetic flux passing through the core (7a), the change is extracted as a signal from the output coils (7C) and (7d) that intersect with these magnetic fluxes, and the changes are extracted as signals from the first and second bandpass. Filter (b).

αG, first and second AC amplifier (2), 0Q5 first
and a second rectifier α1. αη and the first and second
An output voltage V x h vZ corresponding to the external magnetic field strength is outputted through the DC amplifiers a◆ and (g).

(II is the first A/D converter that A/D converts the output voltage Vx, (7) is the first memory connected to the first A/D converter 0, (b) is the first A read/write control circuit for the memory (E), (2) is the first switch, (to) is the first
ROM, Trout is the first D/A converter connected to the first memory (1) via the first ROM (to), (7) is the eighth DC amplifier, and (e) is the first D/A converter connected to the first memory (1). Use the power switch 2,
The above-mentioned canceling coils (6a) and (6b) (hereinafter referred to as K'r>*
2 A/ (explained as (a)) is connected to the output terminal of the eighth DC amplifier 4.

A circuit similar to the above is provided corresponding to the output voltage Vz. That is, the (goods) is the second A/D converter, (
(to) is the second memory, (to) is the second reading control circuit, (function) is the eighth switch, C1υ is the second ROM, @ is the second D/A converter, (to) is the fourth In the above configuration, the canceling coil 2 is connected to the output terminal of the fourth DC amplifier (to) through the fourth energization switch ■. The magnetic sensor (7) detects voltages Vx and V according to the horizontal component of the external magnetic field.
z is output 0 From these detected voltages Vx and Vz, as described above, arithmetic processing is performed based on the value at the stage before the correction current is applied to the cancellation coil (2) or (6), and then the correction current value, that is, cancellation. Coil (2) or (6
) must be determined. This is because once the correction current is applied, the magnetic sensor (7
) also detects the generated component of the canceling magnetic field, and the reference value for automatic correction is not determined and normal correction is performed.
) If possible, Vx, V
It is possible to close the feedback loop so that the y value is 0, but this may not be possible.

In this example, in view of the above-mentioned points, the initial detected values Vx and Vz before cancellation correction were stored in person/D [[K first and second memo +) gJ, @IIC, respectively, and calculations were made from the detected values. Correction current canceling coil (2),
(6) is configured to be energized. That is, immediately after the main power switch (not shown) of the display device is turned on and the color cathode ray tube (1) is demagnetized (not shown), the detected value V x t-A is maintained for a certain period of time T. The /D-converted detected amount is stored in the first memory lJmK. During this period, the first switch (a) of the TK first read/write control circuit Qυ is closed, and in conjunction with this first switch (2), the first energization switch (to) to the cancellation coil (6) is closed. is open. The initial detection amount that is stable during the above-mentioned fixed period T is stored in the first memory (E), and after the period T has passed, the first switch (2) is reversed and the calculation is sent to the canceling coil (6). The optimum correction current is applied. At this point, Vx outputs a detected value different from the initial state, but 1
Since the first switch (in the first switch) is open, the first memory wire is not accepted and the state continues with the initial magnetic field amount Vx stored. ◎The initial magnetic field amount Vz is similarly set for the correction of the tube axis direction component Vz. is stored in the memory (c) of fault 2 and the optimum correction current is energized to the canceling coil (2) K.

The optimum correction current can be determined from the initial magnetic field detection values Vx and Vz in the following manner.

Knowing in advance at the design stage what kind of detected values Vx and Vz will output when various external magnetic fields are applied, including the structure of the display device and the position of the magnetic sensor (7); Furthermore, it is possible to know in advance at the design stage what correction current value should be sufficient for i&appropriate correction for these external magnetic fields. By storing a correction table (table) of the correlation between the detected values Vx, Vz and the optimum correction current value in the first and second ROMs ■ and 0η, the first
It becomes possible to output the optimum correction current through the second D/A converter (c), (2), the eighth and fourth DC amplifiers), and -.

By the way, in the above embodiment, the magnetic cancellation correction means was constructed with an oven-loose circuit, but in order to further improve the cancellation accuracy, the cancellation coil (2) a (a
) A method may also be considered in which the voltage generated in a current detection resistor (not shown) inserted in series with K is fed back to the DC amplifier (c) and C13. In addition, the first and second R
OM (a), the first and second D/A converters (goods) that have gone through 0υ, @ the output reference value, and the output of the magnetic sensor (7) after cancellation correction based on the initial magnetic field detection amount. The reference value and the corrected magnetic sensor (
It is also possible to construct a closed loop that performs comparison and amplification with the output of step 7).

In any case, the initial detection value before cancellation correction must be memorized.K remains the same.In addition, as the color cathode ray tube (1) mentioned above, one that uses an internal or external magnetic shield plate is also applicable. It is possible.

Furthermore, the configuration and shape of the magnetic canceling coils (2) and (6) may be other than those in the above embodiments. Further, the installation location of the magnetic sensor (7) does not particularly matter, whether it is inside or outside the envelope (3) such as a cabinet.

Furthermore, in the above embodiment, a reactor-type magnetic sensor (7) is used, but it is also possible to use a Hall element or the like.

(Effects of the Invention) As described above, according to the present invention, a color cathode ray tube is equipped with a magnetic sensor that detects an external magnetic field applied to a color cathode ray tube, and a magnetic canceling coil that flows a correction current according to the detected value of the magnetic sensor. Since the configuration is configured to perform correction to cancel out unnecessary external magnetism, it is possible to realize a color cathode ray tube display device with almost no beam movement problems without requiring the installer's intervention. 0, which is extremely suitable for high-definition color display devices.

[Brief explanation of drawings]

FIG. 1 is an external view showing an embodiment of a color cathode ray tube display device according to the present invention, FIG. 2 is a block diagram of a magnetic cancellation correction means in the same color cathode ray tube display device, and FIG. FIG. 4 is a perspective view of a color cathode ray tube and its surroundings in a conventional color cathode ray tube display device, and a circuit diagram of a magnetic correction means. FIG. o) --- Force 5-F5 Run fil, (2), (6
a), (6b) - canceling coil, (7)... magnetic sensor, C1υ... memory. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A magnetic sensor that detects the direction and magnitude of an external magnetic field applied to the color cathode ray tube, a magnetic cancellation coil that flows a correction current according to the uncorrected magnetic field detection value by the magnetic sensor, and a correction current that flows through the magnetic cancellation coil. A color cathode ray tube display device comprising means for memorizing an initial magnetic field amount in an uncorrected state before flowing.