JPS58123288A - Color television monitor - Google Patents

Abstract

PURPOSE:To eliminate a color shift even when a color cathode-ray tube is set in any direction at any point on the ground by detecting the intensity of an external magnetic field through a magnetism sensor all the time and canceling the external magnetic field that the color cathode-ray tube receives. CONSTITUTION:This monitor is provided with the magnetism sensor 10 fitted in parallel to the display screen of the color-cathode ray tube 4, a DC amplifier 11, and a coil 12, when fed with an output current from the amplifier 11, generates a magnetic field nearly at right angles to the fluorescent screen of the cathode-ray tube 4 and in the opposite direction to the external magnetic field phi. In this constitution, when the magnetic field phi varies, the sensor 10 and amplifier 11 flow a current which allows the coil 12 to produce a magnetic field with an equal absolute value in the opposite direction to variation of the magnetic field phi, thus canceling the external magnetic field. Consequently, the track of an electron beam is unchanged, so a picture free of a color shift in any environment and in any direction is displayed all the time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color television monitor that eliminates color shift caused by external magnetic fields.

A color cathode ray tube normally used in color television shows red (R), green (G), and blue (B) colors that are arranged in dots on the trajectory of the electron beams emitted from three electron guns. It consists of a phosphor that emits light and a shadow mask that allows the electron beam emitted from the electron gun to land on the dot-shaped phosphor that emits a predetermined color.

Therefore, when a magnetic field is applied from outside the cathode ray tube, the trajectory of the electron beam changes due to the magnetic field, and the electron beam lands on an unspecified phosphor, causing dots of the phosphor that should not normally emit light to emit light, resulting in the purity of the displayed color. If it deteriorates or is exposed to a strong magnetic field, a completely different color will be displayed.

This phenomenon is particularly noticeable in high-resolution color cathode ray tubes in which the dot pitch of the phosphor is fine, and they have the disadvantage that they cannot be used in locations where the external magnetic field changes or are mounted on moving objects such as ships.

This point will be explained in more detail with reference to the drawings.

FIG. 1 is a block diagram of a conventional two-television monitor, and FIGS. 2 and 3 are diagrams for explaining the operation of a color cathode ray tube. The red signal 8m, the green signal &, and the blue signal & are amplified by the video circuit 1 and applied to the electron gun 3 of the color cathode ray tube 2, respectively.

An electron beam 4 corresponding to the three types of signals 81.8G and 8B is emitted from the electron gun 3, and after being accelerated with a high voltage, the electron beam 4 is controlled by a shadow mask 5 and enters the phosphor 6. It emits three colors corresponding to the three types of signals SR, 8G, and 8B described above. - 10,000, the electron beam 4 is deflected by a deflection magnetic field created by a deflection circuit 7 that generates and amplifies a deflection signal from the horizontal synchronization signal H and the vertical synchronization signal ■, and a deflection yoke 8 driven by the deflection circuit 7. Fluorescent material 6
emit light in a planar manner. A television set according to such an operating principle,
When a magnetic field φ is applied from the outside to the color cathode ray tube 2 of the monitor, the electron beam 4 receives a force perpendicular to the field, changing its locus and shifting its landing position on the fluorescent surface, resulting in color shift.

To explain the influence of the external magnetic field in more detail, when the external magnetic field φ is applied to the color cathode ray tube as shown in FIG. 2, the relationship between the electron beam 4 and the phosphor 6 is as shown in FIG. become that way. That is, in FIG. 3, the green electron beam 4G in the absence of an external magnetic field passes through the aperture of the shear mask 5 and emits green light. In this state, the external magnetic field φ
When the force is applied, the electron beam 4G changes its locus as shown in the dotted line 4, and most of it lands on point B of the blue phosphor section, emitting blue light.

As described above, when exposed to an external magnetic field, the locus of the electron beam changes and the specified phosphor does not emit light, resulting in color purity (bi, -
However, if the external magnetic field is strong, other colors will shine.

In conventional television monitors, in order to avoid the influence of the magnetic field mentioned above, 1. The disadvantage is that the entire television set or 7' monitor must be magnetically shielded with a material having high magnetic permeability, such as permalloy, or that corrections must be made each time depending on the strength of the external magnetic field, resulting in increased costs. In addition, the strength of the external magnetic field differs depending on the surrounding magnetic environment and geomagnetism in different parts of the earth, and also depending on the direction of north and south. It was not possible to install electricity and use it.

One object of the present invention is the conventional television set as described above.

To provide a television/monitor that does not cause color shift even when facing in any direction at any point on the ground by eliminating the drawbacks of monitors.

A color television set according to the present invention includes the above-described conventional color cathode ray tube, its driving circuit, a magnetic sensor whose detection surface is installed parallel to the display surface of the color cathode ray tube, and an amplifier for amplifying the output of the magnetic sensor. and a coil that generates a magnetic field using the output of the amplifier in a direction substantially perpendicular to the display surface of the color cathode ray tube and canceling a magnetic field incident from the outside.

The present invention will be specifically explained according to examples.

FIG. 4 shows an embodiment of the present invention, in which a sensor l-O having an element, such as a Hall element, installed parallel to the display surface of a cathode ray tube 4 and converting the strength of a magnetic field into an electric signal; When the DC amplifier 11 amplifies the electrical signal from the IO and the output current from the DC amplifier 11 is energized, a force 2 - an external magnetic field φ approximately perpendicular to the fluorescent surface and the shadow mask surface of the cathode ray tube 4 is generated. A coil 12 is attached so as to generate a magnetic field in the opposite direction. According to this embodiment, when the external magnetic field φ changes, the magnetic sensor lO and the DC amplifier 11 cause a current to flow through the coil 12 to generate a magnetic field having the same absolute value and in the opposite direction to the change in the external magnetic field φ. Since the trajectory of the electron beam does not change, it is possible to always display images with strong color shift in any environment or direction.

The other coil 13 in this figure is an old demagnetizing coil that demagnetizes the shadow mask when it becomes magnetized.
4 and the switch 15, which has been used in the past.

Experiments have shown that the direction of the magnetic field that has the most influence on changes in the trajectory of the electron beam, i.e., color shift, is perpendicular to the shadow mask surface.
2 should be installed parallel to the surface of the color cathode ray tube.

FIG. 5 shows another embodiment of the present invention, in which the magnetic sensor 10 operates in the same manner as in the first embodiment and is attached parallel to the tube surface of the cathode ray tube 4, but the coil 16 is similar to the one mentioned in the previous embodiment. It serves as both a correction coil 12 and a degaussing coil 13 according to the invention, and during normal use, the switch 17 is tilted to the side where the invention operates.

If the shadow mask becomes magnetized due to an abnormally strong or non-uniform magnetic field, it can be demagnetized by flipping the switch 17 to the opposite side.

As another example, the magnetic sensor and the DC amplifier may be attached outside the frame of the television monitor, but it is clear that this is within the scope of the present invention.

In the color television monitor of the present invention constructed as described above, the magnetic sensor constantly detects the strength of the external magnetic field, so it operates to cancel the external magnetic field received by the color cathode ray tube, so that the external magnetic field does not change. It also has the feature of not causing color shift.

Therefore, according to the present invention, it is possible to constantly change direction in factories of electric power companies and heavy industries, as well as in ships, automobiles, etc., where color televisions and monitors could not be used due to color shift due to changes in external magnetic fields. Since normal images can be displayed even in moving objects, there is a great advantage in that color televisions and monitors can be installed in such places and information processing and system control can be carried out by combinations and monitors.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional color television and monitor; Fig. 2 is a diagram explaining the operation of a color cathode ray tube; Fig. 3 is an enlarged view showing the light emitting operation of a color cathode ray tube and explaining the influence of an external magnetic field; FIG. 4 shows a first embodiment of the invention, and FIG. 5 shows another embodiment of the invention. l...video circuit, 4...color cathode ray tube. 10...Sensor, 11...DC amplifier, 12゜13...Coil, 14...
Posista. 4

Claims (1)

[Claims] A color cathode ray tube, a drive circuit for operating the color cathode ray tube, a magnetic sensor whose detection surface is installed parallel to a display surface of the color cathode ray tube, an amplifier for amplifying the output of the magnetic sensor, and the amplifier. It is attached to the outer periphery of the display surface of the color cathode ray tube so as to generate a magnetic field in a direction perpendicular to the display surface of the color cathode ray tube and canceling an external magnetic field incident on the display surface of the color cathode ray tube with the output of the width filter. A color television monitor consisting of a coil and a coil.