JP2001061077A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce moire at a circumferential part of a display screen while keeping a focus characteristic of an electron beam in the middle of the display screen in an excellent way. SOLUTION: The image display device employing a cathode ray tube A with a deflection yoke 14 consisting of horizontal and vertical deflection coils orthogonal to a tube axis direction of an outer package 11, is provided with a display screen tilt correction coil 21 coaxial to the tube axis direction at an opening side of the deflection yoke 14, a DC current power supply section 22 that supplies a DC current to the display screen tilt correction coil 21, and a rectangular wave current power supply section 23 that supplies a rectangular wave current with a period twice the vertical deflection period in the deflection yoke 14 to the coil 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display apparatus using a cathode ray tube, and more particularly, to a cathode ray tube for arranging a deflection yoke comprising horizontal and vertical deflection coils and displaying a required image on a screen. The present invention relates to an improvement in an image display device that reduces moire generated at the time of display, in particular, moire between a central portion and a peripheral portion of a display screen on average.

[0002]

2. Description of the Related Art Conventionally, a cathode ray tube (CRT) called a picture tube or a color picture tube has been used as an image display device applied for image display. As is well known, the cathode ray tube includes an electron gun provided in a neck portion of an envelope (tube), a phosphor screen formed on a front display panel inside a funnel portion, and a fluorescent screen formed on the neck portion. A deflection yoke comprising horizontal and vertical deflection coils arranged at right angles to the outer periphery of the tube axis direction, and a horizontal and vertical direction in which electron beams emitted and emitted from the electron gun are generated in the deflection yoke. By deflected in the corresponding direction by each of the deflection magnetic fields, and by scanning the phosphor screen surface in the horizontal and vertical directions by the deflected electron beam, the corresponding phosphor particles in a dot arrangement are arranged every frame period of the scanning. Is selectively excited to emit light, and a required image is displayed on the screen.

In an image display apparatus using such a cathode ray tube, an undesired bright and dark stripe pattern is generated on a display screen due to mutual interference between scanning lines and phosphor dots in a vertical direction. This is a so-called moiré, and since this moiré is a cause of image quality deterioration of a display image on a display screen, various measures have been taken to suppress the moiré.

In the prior art, as means for suppressing the moire, conceptually, for example, means for changing the scanning line interval between horizontal scanning lines, means for superimposing a minute AC current on a vertical deflection current, and 2H for horizontal scanning are used. Means for changing the focus for each synchronization have been proposed. Further, Japanese Patent Laid-Open No. 5-2
JP-A-36290 also discloses a means for changing the display position of a screen every frame period of vertical scanning.

[0005]

As described above, conventionally, as means for suppressing the moire generated in the cathode ray tube, (a) a rectangular wave current is superimposed on the vertical deflection current every 2H synchronization. Means for moving the even-numbered or odd-numbered horizontal scanning lines and changing the scanning line interval on the display screen to reduce moire; (b) superimposing a minute alternating current on the vertical deflection current to display the display screen; Means for reducing the moire by slightly undulating each scanning line direction above, (c) Changing the dynamic voltage intended to improve peripheral focus every 2H synchronization of horizontal scanning, and changing the focus for each scanning line (D) means for reducing the moire by shifting the display position of the screen relatively vertically in each one frame period of the vertical scanning.

Here, the moiré characteristics of the cathode ray tube generally depend on the shape of the electron beam emitted from the electron gun and, consequently, the focusing performance.
The moiré characteristics at the peripheral portion of the display screen are more so at the peripheral portion of the display screen because the shape of the electron beam has a distortion due to the deflection aberration than at the central portion of the display screen and is in a so-called horizontal collapse state. Remarkable moire occurs.

However, in the case of each of the conventional means described in (a) to (d) above, not only the display image portion at the peripheral portion of the display screen but also the display image portion at the central portion of the display screen. In the same manner as above, since the scanning line interval and the like by the electron beam are made to fluctuate in the vertical direction, the focus characteristic of the electron beam as the whole display screen is significantly deteriorated. For example, the height of the display characters as the display image portion at the center of the display screen is also relatively large compared to the periphery of the display screen. That is,
In other words, there is a problem in that the display mode is unbalanced between the central portion and the peripheral portion of the entire image displayed simultaneously for each one frame period and the quality of the display image itself is impaired.

[0008] The present invention has been made to solve such a conventional problem.
An object of the present invention is to provide an image display device capable of effectively reducing moiré in a peripheral portion of a display screen while maintaining good electron beam focus characteristics in a central portion of the display screen.

[0009]

According to a first aspect of the present invention, there is provided an image display apparatus, wherein each of a horizontal and a vertical deflection coil is orthogonal to a tube axis direction of an envelope. In an image display device using a cathode ray tube provided with a deflection yoke, a display screen tilt correction coil coaxial with the tube axis direction is provided on the opening side of the deflection yoke,
A DC current supply power supply for supplying a DC current to the display screen tilt correction coil, and a rectangular wave current supply power supply for supplying a rectangular wave current having a cycle twice as long as a vertical deflection cycle in the deflection yoke are provided. It is characterized by:

In the image display device of the present invention, a rectangular wave current having a period twice as long as the vertical deflection period is supplied to the display screen tilt correction coil disposed on the opening side of the deflection yoke in the cathode ray tube. Thus, moire generated at the peripheral portion of the display screen is reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image display device according to the present invention will be described below in detail with reference to FIGS.

FIG. 1 shows the overall appearance of an image display device including a deflection yoke and a display screen tilt correction coil to which the present embodiment is applied, a DC current supply power supply unit and a rectangle attached to the display screen tilt correction coil. FIG. 5 is a block diagram for explanation conceptually showing a connection state of a wave current supply power supply unit.

FIG. 2 is an explanatory diagram showing a state of a tilt change of a display screen in the image display device of the above.
FIG. 4A shows the correlation between the vertical deflection current to the vertical deflection coil of the deflection yoke and the rectangular wave current to the display screen tilt correction coil. FIG. 6A shows the vertical deflection supplied to the vertical deflection coil. FIG. 3B is a waveform diagram of a current, and FIG. 3B is a waveform diagram of a rectangular wave current supplied to the display screen tilt correction coil.

It should be noted that the inclination angle of the inclination change on the display screen shown in FIG. 2 is somewhat exaggerated to assist in understanding the operation of the present embodiment and to supplement the explanation. Add it.

In the apparatus configuration shown in FIG. 1, the image display device according to the present embodiment is used by adding the configuration of the present embodiment to the cathode ray tube A of a normal mode for displaying a required image.

That is, the cathode ray tube A has an envelope comprising a neck portion 12 having an electron gun (not shown) provided therein and a funnel portion 13 having a phosphor screen (not shown) formed on the inner surface of the front display panel. (Tube) 11,
And horizontal to the outer periphery of the neck portion 12 at right angles to the pipe axis direction,
It is configured by arranging a deflection yoke 14 composed of vertical deflection coils.

In the case of this embodiment, the cathode ray tube A having the above configuration
The display screen tilt correction coil 21 is provided on the opening side of the deflection yoke 14, that is, on the funnel section 13 side, coaxially with the tube axis direction of the envelope 11.
A DC current supply power supply unit 22 for supplying a DC current to the display screen tilt correction coil 21;
, That is, a rectangular wave current having a period twice as long as the period of the vertical deflection current periodically supplied to the vertical deflection coil as shown in FIG.
This is connected to a rectangular wave current supply power supply unit 23 for supplying a rectangular wave current shown in FIG.

Accordingly, in the image display apparatus to which the present embodiment is applied, and eventually, in the cathode ray tube A, the electron beam emitted and emitted from the electron gun is emitted from the deflection yoke 14 as in the conventional case.
The screen is deflected by the horizontal and vertical deflection magnetic fields generated in the above, and scans the phosphor screen surface in the horizontal and vertical directions, thereby displaying a required image on the screen every frame period of the scanning. At this time, as shown in FIG. 2, the display screen tilt correction coil 21 arranged on the opening side of the deflection yoke 14 finely alternates in the left-right rotation direction every frame display by the supplied rectangular wave current. As a result, the moire generated on the display screen is reduced regardless of the central part and the peripheral part of the display screen.

That is, in the prior art, the moire on the image display surface is reduced by uniquely changing the scanning line interval of the electron beam and the like in the vertical direction for each frame. In the case of the embodiment, the focus characteristics of the electron beam at the center of the display screen are maintained as well as the conventional one by changing the relative display position by alternately finely tilting in the left-right rotation direction for each frame. As it is, moire on the image display surface can be reduced as expected.

[0020]

As described above in detail with the embodiment, according to the image display device of the first aspect of the present invention,
A rectangular wave current having a cycle twice as long as the vertical deflection cycle is supplied to the display screen tilt correction coil arranged on the opening side of the deflection yoke in the cathode ray tube. This has a practically excellent feature that moiré generated in the image can be more effectively reduced and a high-quality image can be displayed.

[Brief description of the drawings]

FIG. 1 is an overall external configuration of an image display device including a deflection yoke and a display screen tilt correction coil to which an embodiment of the present invention is applied, and a DC current supply power supply unit and a rectangular wave attached to the display screen tilt correction coil. FIG. 4 is a block diagram for explanation conceptually showing a connection mode of a current supply power supply unit.

FIG. 2 is an explanatory diagram showing a state of a tilt change of a display screen in the image display device.

FIG. 3 shows a correlation between a vertical deflection current to a vertical deflection coil of the deflection yoke and a rectangular wave current to a display screen tilt correction coil. FIG. 3A is supplied to the vertical deflection coil. FIG. 4B is a waveform diagram of a vertical deflection current, and FIG. 4B is a waveform diagram of a rectangular wave current supplied to a display screen tilt correction coil.

[Explanation of symbols]

 A: cathode ray tube 11: envelope (tube) 12: neck 13: funnel 14: deflection yoke composed of horizontal and vertical deflection coils 21: display screen tilt correction coil 22: DC current supply power supply 23 ... Square wave current supply power supply

Claims (1)

[Claims] 1. An image display apparatus using a cathode ray tube provided with a deflection yoke composed of horizontal and vertical deflection coils perpendicular to a tube axis direction of an envelope, wherein the tube shaft is provided on an opening side of the deflection yoke. A display screen tilt correction coil coaxial with the direction; a DC current supply power supply for supplying a DC current to the display screen tilt correction coil; and a rectangular wave having a cycle twice as long as a vertical deflection cycle in the deflection yoke. An image display device comprising: a rectangular wave current supply power supply unit for supplying a current.