JP3045082B2 - Display with degauss control function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetic correction function for correcting the influence of a magnetic field change outside a display in a CRT display.

[0002]

2. Description of the Related Art Since a CRT display draws an image on a phosphor screen by scanning an electron beam emitted from an electron gun, when a magnetic field is applied to the electron beam, the quality such as color purity deteriorates. Occurs. The magnetic field applied to the electron beam includes terrestrial magnetism and magnetism generated when a magnetic body such as a metal part inside a CRT display is magnetized. The magnetization of the magnetic body is caused by a change in the magnetic field applied to the magnetic body due to movement of the CRT display or a change in the magnetic field near the CRT display. In particular, in a color CRT display or the like, when a shadow mask, which is a thin metal plate through which an electron beam passes, is magnetized, it greatly affects the quality such as color purity.

As a countermeasure against this adverse effect, in a conventional display device with a degauss control function, an alternating current that converges for a predetermined time is passed through a coil provided around a display body of a CRT to generate a magnetic field. Degaussing function to demagnetize the magnetic material, and measure the direction and strength of the magnetic field applied to the electron beam with a magnetic sensor, etc., and generate a magnetic field in the direction opposite to the direction of the magnetic field to cancel the magnetic field applied to the electron beam And other magnetic correction functions.

For example, in the device disclosed in Japanese Patent Application Laid-Open No. 06-189322, a degaussing operation (hereinafter, referred to as degauss) for erasing magnetized magnetization around a display device with an alternating current is performed only when power is turned on.

FIG. 2 shows a configuration diagram of a main part of the conventional display device with a degauss control function.

This conventional display device with a degauss control function has a degauss control circuit 302, a magnetic sensor 1, a correction coil control circuit 3, a degauss coil 6, a magnetic correction coil 7, and a CRT 5.

The magnetic sensor 1 detects the direction and intensity of the magnetic field 101 applied to the electron beam, and performs a correction coil control circuit 3
Output the magnetic sensor output 102. When the magnetic sensor output 102 is input, the correction coil control circuit 3
A correction coil drive signal 105 for generating a magnetic field whose direction is opposite to and the same in strength as the magnetic field detected by the magnetic sensor 1 is output to the magnetic correction coil 7 based on such data. When the correction coil drive signal 105 is input, the magnetic correction coil 7 generates a magnetic field that cancels the magnetic field 101. The degauss control circuit 2 outputs a degauss coil drive signal 104 to the degauss coil 6 in response to a power-on signal 106 generated upon detecting that power is supplied to the CRT 5.
The degauss coil 6 receives the degauss coil drive signal 104 and performs degauss on the CRT 5 with an AC magnetic field.

In this conventional display device with a degauss control function, when a power is supplied to the CRT 5, a power-on signal 106 is supplied.
Occurs, and only at that time, the degauss control circuit 302 generates the degauss coil drive signal 104, and the degauss coil 6
Is driven to degauss the CRT 5. CR
After performing the degauss of T5, the magnetic sensor 1 detects the magnetic field 101
And outputs a magnetic sensor output 102 to the correction coil control circuit 3. Correction coil control circuit 3
Outputs a correction coil drive signal 105 to continuously generate a magnetic field that drives the magnetic correction coil 7 and cancels the magnetic field 101.

Japanese Patent Application Laid-Open No. 02-238790 describes a system in which magnetic correction operation and degauss are simultaneously performed by one coil.

FIG. 3 is a block diagram of a main part of the conventional display device with a degauss control function. The same numbers as those in FIG. 2 indicate the same components.

This conventional display device with a degauss control function has a magnetic sensor 1, a degauss / magnetic correction coil control circuit 8, and a degauss / magnetic correction coil 9. The degauss / correction coil control circuit 8 receives the magnetic sensor output 102 and outputs a degauss / magnetic correction coil drive signal 107 to the degauss / magnetic correction coil 9. The degauss / magnetic correction coil drive signal 107 is obtained by superimposing an alternating current for performing degauss on a direct current for performing magnetic field correction.

The degauss / magnetic correction coil 9 has a degauss /
Upon receiving the magnetic correction coil drive signal 107, degauss is performed, and a magnetic field that cancels the magnetic field 101 is simultaneously generated to correct the CRT 5.

In this conventional display device with a degauss control function, the degauss / magnetic correction coil control circuit 8 uses a magnetic field 101
When a magnetic sensor output 102, which is information on the strength and direction of the magnetic sensor, is input, a degauss / magnetic correction coil drive signal 107 is output to the degauss / magnetic correction coil 9 to perform magnetic correction. And a DC current for performing degauss is superimposed on the DC current for performing magnetic correction and degauss simultaneously with one coil.

Japanese Unexamined Patent Publication No. 63-033779 discloses that in a display device having a screen rotation function, rotation of a screen is detected by a rotation sensor of an installation portion, and a signal indicating the degauss is detected. The method of implementation is described.

In any of the above-mentioned conventional display devices with a degauss control function, the mounting position of the degauss coil is usually limited to the rear surface of the CRT. In some cases, the degauss effect is not uniform over the entire screen. Especially in the case of large-screen display devices, the degauss effect is weakest at the center of the screen, so depending on the direction and strength of the externally applied magnetic field, even if degauss is applied to the magnetized magnetism, the magnetism cannot be removed evenly May remain.

In the case where the degauss effect is not uniform and the magnetism partially remains as described above, it is difficult to correct the magnetism by the magnetic correction. This is because the magnetic correction coil can only apply a correction magnetic field of a certain strength to the CRT.
It is difficult to cancel out the magnetic field generated unevenly on the screen of T by the correction magnetism.

Whether or not a magnetization pattern that is difficult to correct when degauss is performed differs depending on the shape and structure of the CRT and the display device.

FIG. 4 shows an example of a screen display when a magnetization pattern that is difficult to correct remains when this degauss is performed.
(A), (b) and (c) are shown. FIG. 4A shows a screen display in an initial state where no magnetic field is applied from the outside. When a magnetic field is externally applied to the CRT in this state, the CRT is magnetized, and a green image is originally supposed to be displayed as shown in FIG. 4B due to the influence of a magnetic field generated from the magnetized magnetism. It becomes like this. When degauss is performed in this state, the screen returns to the original green screen if the magnetized magnetism can be completely degaussed. However, if a portion where the effect of degauss does not reach remains partially, FIG. The part which remains in the red screen like this is left. If such a non-uniform magnetization pattern remains, it becomes difficult to correct it by magnetic correction.

[0019]

The above-mentioned conventional display device having a degauss control function has the following problems. (1) In the method of performing degauss only at power-on,
After the power is turned on, the CRT is moved and a magnetic field change occurs.
Is magnetized, all the magnetic fields generated by the magnetization must be corrected by the magnetic correction coil. for that reason,
In the case where the change in the magnetic field after turning on the power is large, or in the case of a display device having a large screen, the amount of correction by the magnetic correction coil increases, and the current consumption increases. Further, a change in the magnetic field near the magnetic correction coil becomes large, and uniform correction cannot be performed. (2) Since the mounting position of the degauss coil is usually limited to the rear part of the CRT, the degauss effect is weakest at the center of the screen in a large-screen display device, so that the degauss effect is uniform over the entire screen. When degauss is performed, degauss becomes partially incomplete and a magnetization pattern that cannot be corrected by magnetic correction remains. (3) In a method in which the rotation of the screen is detected by a rotation sensor of the installation unit and the signal is used to perform degauss, if the display device is moved without rotating the screen, the degauss cannot be performed. .

It is an object of the present invention to provide a display device with a degauss control function in which the amount of correction by a magnetic correction coil is reduced as much as possible and current consumption is suppressed.

It is another object of the present invention to provide a display device with a degauss control function which can prevent a case where a magnetized pattern magnetized on a CRT is magnetized and a magnetic pattern which cannot be easily corrected by magnetic correction remains. is there.

[0022]

To achieve the above object, a display device with a degauss control function according to the present invention comprises: a magnetic sensor for detecting the direction and intensity of a magnetic field applied to the display device; A degauss control circuit for detecting a change in the magnetic field based on the direction and intensity of the applied magnetic field to determine whether or not the degaussing operation is to be performed, a degauss coil for performing the degaussing operation according to an instruction of the degauss control circuit, It has a correction coil control circuit for outputting a signal for generating a correction magnetic field for canceling the magnetic field, and a magnetic correction coil for generating a correction magnetic field for canceling the magnetic field according to an instruction from the correction coil control circuit.

According to the present invention, not only after turning on the power, but also
When the change in the magnetic field applied to the display device is a certain value or more, the degauss is automatically performed to minimize the magnetization of the display device, and the amount of magnetic correction by the magnetic correction coil can be reduced.

According to an embodiment of the present invention, the degauss control circuit controls the intensity of the magnetic field for magnetizing the magnetism of the magnetized pattern, which cannot be uniformly demagnetized by the degaussing operation and causes non-uniform magnetism, to the display device. And storage means for storing the direction and
If the strength and direction of the magnetic field detected by the magnetic sensor match the strength and direction of the magnetic field stored in the storage means, no degaussing operation is performed.

According to the present invention, a case where a magnetization pattern which remains difficult to correct by magnetic correction when degauss is performed is determined before performing degauss based on data stored in a built-in ROM. Degauss is not performed and only magnetic correction is performed. Therefore, since a non-uniform magnetized pattern does not remain, deterioration of image quality can be prevented even when various patterns of magnetic field change occur.

[0026]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a main part of a display device with a degauss control function according to an embodiment of the present invention. The same numbers as those in FIG. 2 indicate the same components.

The display device with a degauss control function of the present embodiment is different from the conventional display device with a degauss control function in FIG. 2 in that the degauss control circuit 302 is replaced by a degauss control circuit 2 and the degauss control circuit 2 outputs a magnetic sensor output 102 to the degauss control circuit 2. Is input.

The degauss control circuit 2 outputs the magnetic sensor output 10
When the change of the magnetic field 101 is detected by the step 2, the execution / non-execution of the degauss is determined based on the data stored in the built-in ROM. When the execution is determined, the degauss coil drive signal 104 is output to the degauss coil 6.

Whether or not a magnetized pattern, which is difficult to correct by magnetic correction when a degauss is performed, remains depending on the shape and structure of the CRT and the display device. In addition to the display, degauss is performed each time, and data is acquired on what magnetic field is applied to result in a magnetization pattern that cannot be completely degaussed. Then, this data is stored in the ROM data of the degauss control circuit 2.

Next, the operation of this embodiment will be described with reference to FIG.

When the magnetic field 101 does not change and remains constant, the correction coil control circuit 3 detects the strength and direction of the magnetic field 101 by the magnetic sensor 1 and generates a magnetic correction coil to cancel the magnetic field 101. 7, a correction coil drive signal 105 is output.

When the magnetic field 101 changes, the degauss control circuit 2 outputs the magnetic sensor output 1 output from the magnetic sensor 1.
02, the change is detected. When the change is equal to or more than a certain value, the degauss control circuit 2 has a built-in R
The magnitude and direction of the magnetic field for magnetizing the magnetism, which remains a magnetization pattern that is difficult to correct when degauss stored in the OM is performed, and the strength and direction of the magnetic field 101 are compared.

If the data stored in the built-in ROM does not match the strength and direction of the magnetic field 101, the degauss control circuit 2 performs a degauss by outputting a degauss coil drive signal 104 to the degauss coil 6. . After performing the degauss, the correction coil control circuit 3 determines the strength and direction of the magnetic field 101 after the degauss by the magnetic sensor 1.
, And outputs a correction coil drive signal 105 to perform correction by the magnetic correction coil 7.

When the data stored in the built-in ROM matches the strength and direction of the magnetic field 101, the degauss control circuit 2 does not output the degauss coil drive signal 104 and does not perform degauss. In this case, if degauss is performed, the degauss effect becomes non-uniform, and a magnetization pattern which is difficult to correct by magnetic correction remains. in this case,
The correction coil control circuit 3 drives the correction coil 7 to perform only magnetic correction.

According to the above operation, in the display device with the degauss control function of this embodiment, the non-uniform magnetization pattern
Since it does not remain at T5, it is possible to prevent image quality from deteriorating due to a magnetic field change.

In this embodiment, the degauss control circuit 2
And the correction coil control circuit 3 are separately controlled, but it is also possible to control the degauss control circuit 2 and the correction coil control circuit 3 by one CPU.

[0038]

As described above, the present invention has the following effects. (1) Since the implementation of degauss is controlled by detecting the direction and intensity of the magnetic field change, the magnetization of the CRT can be minimized, and the correction amount of the magnetic correction coil can be reduced. As a result, current consumption can be suppressed. (2) Since it is possible to prevent a magnetization pattern that is difficult to correct by magnetic correction from remaining, deterioration in image quality can be prevented even in various magnetic field changes.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a display device with a degauss control function according to an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of a conventional display device with a degauss control function.

FIG. 3 is a block diagram of a main part of another conventional display device with a degauss control function.

FIG. 4 is a screen display example when a magnetization pattern that is difficult to correct remains when degauss is performed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 magnetic sensor 2 degauss control circuit 3 correction coil control circuit 5 CRT 6 degauss coil 7 magnetic correction coil 8 degauss / magnetic correction coil control circuit 9 degauss / magnetic correction coil 101 magnetic field 102 magnetic sensor output 104 degauss coil drive signal 105 correction coil drive Signal 106 Power-on signal 107 Degauss / magnetic correction coil drive signal 302 Degauss control circuit

Claims (1)

(57) [Claims] 1. A display device having a degauss control function, wherein a demagnetizing operation cannot uniformly demagnetize and non-uniform magnetism remains.
The strength of the magnetic field that magnetizes the magnetized pattern to the display device
Storage means for storing the direction and strength of a magnetic field applied to a display device; and a magnetic sensor for detecting a change in the magnetic field based on the direction and strength of the magnetic field detected by the magnetic sensor. Detected by
The strength and direction of the applied magnetic field are stored in the storage means.
Degaussing only when it does not match the strength and direction of the magnetic field
A degauss control circuit for determining operation, a degauss coil for performing a degaussing operation according to an instruction of the degauss control circuit, and a correction coil control circuit for outputting a signal for generating a correction magnetic field for canceling the magnetic field detected by the magnetic sensor A display device with a degauss control function, comprising: a magnetic correction coil that generates a correction magnetic field that cancels a magnetic field according to an instruction from the correction coil control circuit.