JPH10322715A - Moire reduction method and device in color cathode-ray tube display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To gradually decrease the fine video identification power of a viewer from a screen center to the outer peripheral direction by finely vibrating raster for constituting the screen of a color cathode-ray tube display device in a circumferential direction for surrounding the screen center at a high speed. SOLUTION: An AC voltage amplifier circuit 7 outputs an AC current corresponding to control signals, superimposes it on a DC current and supplies it to a coil 3. The DC current component corrects the inclination of images by an external magnetic field and the AC components of the AC current act so as to reduce moire. Then, by the AC components of the AC current supplied to a deflection coil 3, the direction of a current is changed by a cycle corresponding to a frequency. Thus, since the direction of a magnetic field generated by the deflection coil 3 is cyclically changed, the raster by the scanning of an electron beam 2 is rotationally vibrated corresponding to the size and direction of the magnetic field. Then, the images are rotationally vibrated around the part near the center, luminance is averaged at an image peripheral edge and the moire is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for reducing moiré in a color cathode ray tube display, and more particularly to a method for rotating a moire generated in a still picture display state of a color cathode ray tube to a raster constituting a screen in a rotating direction. The present invention relates to a method and an apparatus for reducing a raster in a color cathode ray tube display which is reduced by applying a micro vibration.

[0002]

2. Description of the Related Art When displaying, for example, a still image on a fluorescent screen of a color cathode ray tube, if there is a difference between the dot pitch of electron beam scanning lines and the dot pitch of a fluorescent screen, so-called moire (interference fringes) may occur. It has been known.

This moiré is caused not only by the difference in the horizontal dot pitch of the scanning lines but also by the difference in the vertical dot pitch of the scanning lines. The former is called character moiré, and the latter is called raster moiré.

When this moiré occurs, an image is displayed on the screen as if the curtain of a race is swaying by the wind. Particularly, when a color cathode ray tube display is used as a monitor of a personal computer, There is a problem that the screen is difficult to see and causes eye fatigue to the patient.

Therefore, in order to reduce this moiré,
Conventionally, various moiré reduction measures have been taken. As one of them, a method called a moiré canceller is known.

In this moiré canceller, the horizontal phase of the video signal is periodically vibrated, for example, every one frame to intentionally generate jitter, and the entire screen is finely vibrated in the horizontal direction to allow visual perception. This is to reduce the viewer's fine image discriminating power over the entire screen and disperse (average) the luminance to make moire less noticeable. In addition, this moiré canceller processing can be applied in principle to the vertical direction of the screen. In this case, the screen is slightly vibrated in the vertical direction as a whole, and the same operation is performed. Becomes

[0007]

However, in such a conventional so-called moiré canceller processing, the whole screen is uniformly finely vibrated regardless of whether the processing is performed in the horizontal direction or the vertical direction. Therefore, not only the both sides of the screen where moiré appears remarkably, but also the image at the center of the screen where the moiré appears relatively lightly vibrate, and depending on the video pattern, the visibility may be significantly reduced. There was a problem to say.

That is, as is generally known, the occurrence of, for example, raster moiré depends on the relationship between the width of the electron beam scanning line and the dot pitch of the fluorescent screen. Moiré is noticeable. This is because the density of the fluorescent dots included in the scanning line varies depending on the path through which the scanning line passes.

As shown in FIG. 4, the electron beam 2 radiated on the fluorescent screen 4 has a circular shape having a diameter D1 at the center of the fluorescent screen 4, whereas the electron beam 2 has both ends in the horizontal direction of the fluorescent screen 4. Part has a vertical width of D2
It becomes a flat and almost elliptical shape crushed by (D1> D2).

As is apparent from this, the occurrence of raster moiré is prominent on both sides of the screen where the electron beam 2 is crushed into a flat elliptical shape and the width of the scanning line is reduced. It is relatively slight at the center of the screen where the electron beam is circular and the scanning lines have a specified width. For this reason, in the moiré canceller processing for uniformly microvibrating the entire screen described above, not only the image on both sides of the screen where moiré is remarkable, but also the image at the center of the screen where moiré appears relatively lightly. Also vibrates, and depending on the image pattern, the visibility may be significantly reduced.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to appropriately reduce moire only without unnecessarily lowering the resolution of the entire screen. It is an object of the present invention to provide a method and an apparatus for reducing moiré in a color cathode ray tube display capable of achieving the above.

[0012]

According to the first aspect of the present invention, there is provided a method for reducing moiré appearing on a screen in a still picture display state of a color cathode ray tube display, the method comprising: By vibrating the raster that constitutes the screen of the tube display at high speed in the circumferential direction surrounding the center of the screen, the viewer's fine image discriminating power gradually decreases from the center of the screen toward the outer periphery. And a method for reducing moiré in a color cathode ray tube display.

According to the first aspect of the present invention, since the fine image discriminating power of the viewer through vision is gradually reduced from the center of the screen toward the outer periphery thereof, moire generated on both right and left sides of the screen is reduced. While it is less noticeable to the patient, the resolution for the patient in the center of the screen is better maintained, and as a result, only the moire is reduced without unnecessarily reducing the resolution of the entire screen. Can be appropriately reduced.

According to a second aspect of the present invention, there is provided an apparatus for reducing moiré appearing on a screen in a still image display state of a color cathode ray tube display, wherein the screen inclination of the color cathode ray tube display is reduced. A deflection coil having a function of correcting the deflection current, a means for supplying a DC current corresponding to a constant screen inclination to the deflection coil, and an AC current to be superimposed on the DC current flowing through the deflection coil. Means for reducing moiré in a color cathode ray tube display.

According to the second aspect of the present invention, it is possible to easily realize a function of finely vibrating a raster constituting a screen of a color cathode ray tube display at a high speed in a circumferential direction surrounding the center of the screen. can do.

The invention according to claim 3 of the present application is characterized in that the amplitude of the alternating current corresponds to a vertical vibration width of about 100 μm on both sides of the screen. In a moiré reduction device in a color cathode ray tube display.

According to the third aspect of the invention, it is possible to appropriately reduce the occurrence of moire on both sides of the screen.

According to a fourth aspect of the present invention, there is provided the moiré reducing device for a color cathode ray tube display according to the second aspect, wherein the frequency of the alternating current is 70 Hz or more.

According to the fourth aspect of the invention, it is possible to appropriately reduce the occurrence of moire on both sides of the screen.

According to a fifth aspect of the present invention, in the color cathode ray tube display according to the second aspect, the deflection coil is a Z yoke coil for correcting a screen inclination or for correcting a geomagnetism. In the moiré reduction device.

According to the fifth aspect of the present invention, the present invention can be realized at low cost while effectively utilizing existing parts.

[0022]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a moiré reduction device for a color cathode ray tube display according to the present invention. As shown in the figure, a color cathode ray tube 5 includes an electron gun 1 that emits an electron beam 2 and a fluorescent screen 4 that emits light when irradiated with the electron beam 2. It is configured to display a moving image.

The deflection coil 3 is provided so as to surround the electron beam 2 and to cross the path of the electron beam 2, and the electron beam 2 is appropriately turned on the basis of the direction and magnitude of the current supplied to the deflection coil 3. The raster forming the screen is bent at an appropriate angle.
Note that the deflection coil 3 can be replaced with an existing Z yoke coil that corrects an inclination due to rotation of an image due to an external magnetic field such as terrestrial magnetism.

The AC current amplifying circuit 7 outputs an AC current having a predetermined frequency and amplitude determined based on a control signal output from the AC current control circuit 6. In this example, the frequency of the alternating current is set to 70 Hz or more, and its amplitude corresponds to a vertical vibration width of 100 μm on both sides of the screen.

The DC current amplifying circuit 9 outputs a DC current of a predetermined level determined based on a control signal output from the DC current control circuit 8. The level of the DC current is set so that the screen has a regular angle by correcting the screen tilt.

The AC current output from the AC current amplifier 7 and the DC current output from the DC current amplifier 9 are superimposed and supplied to the deflection coil 3.

Next, the operation based on the above configuration will be described. In FIG. 1, a DC current control circuit 8 outputs a control signal for controlling the level and direction (polarity) of the DC current Id output from the DC current amplification circuit 9.

The DC current amplifier 9 outputs a DC current Id (FIG. 2A) according to the control signal, and the DC current Id is supplied to the deflection coil 3.

At this time, the level and direction of the DC current Id are controlled by the DC current control circuit 8 in accordance with the degree and direction of the image tilt due to the influence of an external magnetic field such as geomagnetism.

When the DC current Id is supplied to the deflection coil 3, a magnetic field having a magnitude and direction corresponding to the DC current Id is generated, and the electron beam 2 is bent by the magnitude and direction of the magnetic field. Thereby, the raster by scanning of the electron beam 2 rotates according to the magnitude and direction of the magnetic field. For example, as shown in FIG. 3A, when the image 11 is tilted due to the influence of the external magnetic field, the level and the direction of the DC current Id output from the DC current amplification circuit 9 are controlled so that the correct image is obtained. The tilt can be corrected by rotating to the position 12.

On the other hand, the AC current control circuit 6 outputs a control signal for controlling the frequency and the amplitude of the AC current Ia output from the AC current amplifier circuit 7. AC current amplifier 7
Outputs an AC current corresponding to the control signal, and the AC current is superimposed on the DC current Id and supplied to the coil 3 as an AC current Ia ((b) in FIG. 2). The frequency of the alternating current Ia is 70 Hz or higher, preferably 85 Hz or higher, and is set to a frequency higher than the level at which human eyes do not respond. The amplitude in the vertical direction on both sides of the screen due to the alternating current Ia is about 100 μm, and can be controlled by the degree of moiré.

When the alternating current signal Ia, which is a superimposed signal of the direct current Id and the alternating current, is supplied to the deflection coil 3, the component of the direct current Id corrects the image inclination due to the external magnetic field as described above, and the alternating current Ia AC component acts to reduce moiré. AC current Ia supplied to deflection coil 3
, The direction of the current changes at a cycle corresponding to the frequency.

Therefore, since the direction of the magnetic field generated by the deflection coil 3 changes periodically, the raster by scanning of the electron beam 2 rotates and vibrates according to the magnitude and direction of the magnetic field. For example, as shown by the arrow in FIG.
The image 12 whose inclination due to the external magnetic field has been corrected undergoes rotational vibration in the circumferential direction surrounding the center of the screen according to the cycle and amplitude of the AC component of the AC current Ia. In this way,
Since the image 12 rotationally oscillates around its center, the luminance is averaged around the periphery of the image 12, and the occurrence of moire is reduced. That is, by vibrating the raster constituting the screen of the color cathode ray tube display at high speed in the circumferential direction surrounding the center of the screen, the viewer's fine image discriminating power through the sight from the center of the screen to the outer periphery thereof. It can be gradually reduced.

As a result, while the amplitude at the center of the screen is relatively small, the amplitude at the periphery of the screen is large.
It is possible to appropriately reduce only moiré without unnecessarily reducing the resolution of the entire screen.

[0036]

As is apparent from the above description, according to the present invention, there is provided a color cathode ray tube display capable of appropriately reducing moire only without unnecessarily reducing the resolution of the entire screen. A moiré reduction method and apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a specific configuration of a color cathode ray tube display of the present invention.

FIG. 2 shows a direct current I of the color cathode ray tube display of the present invention.
It is a figure which shows the waveform of d and alternating current Ia.

FIG. 3 is an operation explanatory view showing a state of rotation and vibration of an image of the color cathode ray tube display device of the present invention.

FIG. 4 is a diagram showing a relationship between a beam shape and a moire of the color cathode ray tube display device of the present invention.

[Description of Signs of Main Parts]

 REFERENCE SIGNS LIST 1 electron gun 2 electron beam 3 coil 4 fluorescent screen 5 color cathode ray tube 6 AC current control circuit 7 AC current amplifier 8 DC current control circuit 9 DC current amplifier 11 image 12 image

Claims (5)

[Claims] 1. A method for reducing moiré appearing on a screen in a still picture display state of a color cathode ray tube display, wherein a raster constituting the screen of the color cathode ray tube display is a circle surrounding a center of the screen. By finely vibrating in the circumferential direction at high speed, the viewer's fine image discrimination power through vision,
A method of reducing moire in a color cathode ray tube display, wherein the moire is gradually reduced from the center of the screen to the outer periphery thereof. 2. An apparatus for reducing moiré appearing on a screen in a still image display state of a color cathode ray tube display, comprising: a deflection coil having a function of correcting a screen inclination of the color cathode ray tube display; Means for supplying a DC current corresponding to a constant screen tilt to the deflection coil, and means for supplying an AC current to be superimposed on the DC current flowing through the deflection coil, A moiré reduction device in a color cathode ray tube display characterized by the above-mentioned. 3. The apparatus according to claim 2, wherein the amplitude of the alternating current corresponds to a vertical vibration width of about 100 μm on both sides of the screen. . 4. The device according to claim 2, wherein the frequency of the alternating current is 70 Hz or more. 5. The moiré reducing device according to claim 2, wherein the deflection coil is a Z yoke coil for correcting a screen tilt or for correcting a geomagnetism.