JPH06189322A - Earth magnetism correction device for color crt display device - Google Patents

Abstract

PURPOSE:To minimize the adverse effect such as deviation in color purity due to the earth magnetism even when screen-oriented azimuth is changed in an installation site in the color CRT display device. CONSTITUTION:The display device main body 1 is provided with a magnetism sensor 3 detecting degaussing coils 2a, 2b and the earth magnetism to discriminate the screen-oriented azimuth. A microcomputer 10 decides a current and a direction of the current supplied to the degaussing coils 2a, 2b based on earth magnetism azimuth data and supplies the current to the degaussing coils 2a, 2b via drivers 16a, 16b, then a magnetic field to cancel the earth magnetism is generated even when any screen-oriented azimuth is set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a geomagnetism correction device incorporated in a color CRT display such as a cathode ray tube of a color television receiver to correct the influence of geomagnetism on quality such as color purity.

[0002]

2. Description of the Related Art The quality of a CRT display is affected by geomagnetism. This is because the electron beam emitted from the electron gun undergoes path bending due to geomagnetism in the process until it reaches the fluorescent screen. How to be affected by geomagnetism is CRT
It depends on the orientation when the display is installed. The direction of rotation of the electron beam is opposite between when the screen is facing north and when it is facing south, resulting in a large difference in color purity. The direction of electron beam deflection is upside down when facing east and south. By the way, the installation direction of the CRT display is completely up to the individual user. In what direction it will be installed,
It is completely unknown at the manufacturing stage.

Therefore, in order to alleviate the influence of geomagnetism almost uniformly even if installed in any direction of north, south, east, and west, ITC adjustment (integrated tube component: total adjustment of CRT) is made at the time of manufacturing. ) Is done. This is because an external magnetic field is applied in the direction opposite to the earth's magnetism around the CRT display to forcibly cancel the earth's magnetism and neutralize it (no magnetic field), and in that state each setting of the deflection yoke, magnet ring, etc. It adjusts (including convergence, color purity, etc.). Alternatively, the adjustment is made by incorporating a correction amount that substantially cancels the geomagnetism, without performing the forced cancellation of the geomagnetism.

By adjusting the ITC at the manufacturing stage as described above, it is possible to minimize the deterioration of quality due to geomagnetism, regardless of the direction of installation such as north, south, east and west, and various destinations overseas. You can

[0005]

However, the above-mentioned conventional ITC adjustment in the manufacturing stage has a limit to the adjustment accuracy, and if the ITC adjustment is removed from the adjusting device and installed in a different place, a different magnetic field (geomagnetic field) from that at the time of adjustment is obtained. ) Is affected. In particular, the larger the screen of the color CRT display, the longer the distance between the electron gun and the fluorescent screen, the greater the influence of the geomagnetism on the electron beam, and the worse the quality such as color purity is. Moreover, the degree of the influence greatly varies depending on the installation direction of the color CRT display.

The present invention was devised in view of such circumstances, and in the installation site itself, it is possible to minimize adverse effects of geomagnetism in response to changes in the installation direction on the spot. The purpose is to be able to.

[0007]

A color CR according to the present invention
The geomagnetism correction device in the T display includes a degaussing coil mounted around the display body, a magnetic sensor that detects the screen orientation by the geomagnetism, and the same reverse strength as the geomagnetism based on the screen orientation detected by this magnetic sensor. And a means for controlling a current value and a current direction to be applied to the degaussing coil so as to generate the magnetic field.

[0008]

This geomagnetic correction device functions at the installation site of the color CRT display. The magnetic sensor detects the direction of the screen on which the CRT display is installed by detecting the geomagnetism. The control means determines a current value and a current direction to be applied to the degaussing coil based on the screen orientation, and applies the current to the degaussing coil. The degaussing coil generates a magnetic field having the same magnitude as the direction opposite to the earth magnetism, and cancels the earth magnetism.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a geomagnetism correction device for a color CRT display according to the present invention will be described in detail below with reference to the drawings. The CRT display to be applied may be a television receiver or a video display terminal (V
DT).

FIG. 1 is a perspective view showing the appearance of a display body of a color CRT display. A pair of left and right degaussing coils 2a and 2b are symmetrically attached along the ridge line on the back side of the screen in the display body 1 as shown by hatching. Further, a magnetic sensor 3 for detecting the direction of geomagnetism is attached to the back side of the display body 1. Since the orientation relationship between the magnetic sensor 3 and the screen of the display body 1 is fixed,
When the magnetic sensor 3 detects the direction of the geomagnetism,
The orientation of the screen with respect to the geomagnetic orientation can be determined.

FIG. 2 is a block diagram showing the electrical construction of the geomagnetism correction device. 10 is a CPU 11, a ROM 12,
A microcomputer including a RAM 13, 14 is an amplifier for amplifying the output of the magnetic sensor 3, 15 is an A / D converter, and 16a and 16b are drivers for driving the degaussing coils 2a and 2b.

The microcomputer 10 causes the drivers 16a and 16b to perform a power-on reset when the power is turned on.
Is initially driven to pass a current of a certain magnitude and in a certain direction through the degaussing coils 2a and 2b, and a normal degaussing operation before screen display is performed. This is to erase the magnetization magnetized in the magnetic body around the display body 1.

When the power is turned on for the first time after the installation of the color CRT display is completed, the orientation of the screen is detected and the data is stored in the RAM 13. That is, the magnetic sensor 3 detects the azimuth of the geomagnetism, the azimuth signal is amplified by the amplifier 14, converted into digital data by the A / D converter 15 and input to the CPU 11 of the microcomputer 10, and the geomagnetic azimuth data. Are stored in the RAM 13. This RAM
13 is backed up by a rectification power supply circuit branched from the main circuit even when the power supply is off.

The ROM 12 has a table in which the geomagnetic direction data is associated with the current value and the current direction to be passed through the pair of degaussing coils 2a and 2b. The CPU 11 stores the table of the ROM 12 according to the read geomagnetic direction data. Search, read the current value and current direction data,
The data is transferred and stored in the RAM 13. The driver 16a,
A pair of degaussing coils 2 are provided with these data to 16b.
A current having a magnitude and direction corresponding to a and 2b is passed.

As a result, the geomagnetic azimuth relative to the screen azimuth of the display body 1 in the installed state at that time is determined, and the demagnetizing coils 2a and 2b generate magnetic fields in the opposite direction to the geomagnetism and having the same strength. ,
Geomagnetism will be canceled. Therefore, the influence of the geomagnetism on the electron beam traveling from the electron gun to the phosphor screen is eliminated, and it is possible to prevent the deterioration of the image quality such as the deviation of the color purity.

When the power is turned on for the second time and thereafter, the CPU
The driver 11 reads the current value and current direction data from the RAM 13 without searching the ROM 12
a, 16b. The demagnetizing operation for erasing the magnetized magnetization around the display body 1 before the screen is displayed is performed every time the power is turned on.

Incidentally, the geomagnetic data (direction and strength of geomagnetism) for each of a number of destinations (export destinations) is stored in the ROM 12 in advance, and when the destinations are determined, the destinations are selected by a dip switch or the like. The program routine corresponding to the geomagnetic data may be selected. Alternatively, instead of selecting the program routine, a dedicated program for the corresponding destination may be stored in the ROM 12 from the beginning.

[0018]

As described above, according to the present invention, the magnetic field for canceling the earth magnetism is determined by determining the relationship between the actual direction of the earth magnetism at the installation site and the screen orientation. Therefore, regardless of the installation direction, it is possible to minimize adverse effects due to geomagnetism, particularly deterioration of image quality such as color purity shift. The present invention is particularly useful for a large-screen color CRT display which is easily affected by the earth's magnetism.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of a main body of a color CRT display according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the geomagnetism correction device according to the embodiment.

[Explanation of symbols]

 1 ... Display main body 2a, 2b ... Degaussing coil 3 ... Magnetic sensor 10 ... Microcomputer 11 ... CPU 12 ... ROM 13 ... RAM 14 ... Amplifier 15 ... A / D converter 16a, 16b. driver

Claims (1)

[Claims] 1. A degaussing coil mounted around a display main body, a magnetic sensor for detecting a screen orientation by geomagnetism, and a magnetic field having the same strength in the opposite direction as the geomagnetism based on the screen orientation detected by the magnetic sensor. A geomagnetism correction device in a color CRT display, comprising means for controlling a current value and a current direction to be generated in the degaussing coil so as to be generated.