JP2001095002A - Color cathode-ray tube device and moire-suppressing method for the color cathode-ray tube device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a color cathode-ray tube device capable of suppressing moire stripes, without having to especially change the arrangement of an open hole of a shadow mask by dispensing with countermeasures against moire in the color cathode-ray tube device itself, and a method for suppressing the moire. SOLUTION: In this color cathode-ray tube device, a circuit to wave vertical polarized current on a scanning line on a phosphor screen 3 due to horizontal, vertical scanning of electronic beams 8B, 8G, 8R with minute amplitude by superimposing a minute DC current on the vertical polarized current is provided in a polarized circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color cathode ray tube device of a shadow mask type, and more particularly to a color cathode ray tube device in which moire fringes caused by interference between a scanning line on a phosphor screen and an opening of the shadow mask are suppressed. About.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 3, a shadow cathode type color cathode ray tube device has an envelope composed of a panel 1 and a funnel 2, and a light absorbing layer and a light absorbing layer are provided on the inner surface of the panel 1. A phosphor screen 3 including a three-color phosphor layer that emits blue, green, and red light and is formed so as to be embedded in the gap between the light absorbing layers is provided. Further, a shadow mask 5 having a large number of apertures formed on a surface 4 facing the phosphor screen 3 is disposed facing and approaching the phosphor screen 3. On the other hand, 3 in the neck 7 of the funnel 2
An electron gun 9 for emitting electron beams 8B, 8G, 8R is provided. Outside the funnel 2, a deflecting device 10 for generating a magnetic field for deflecting the three electron beams 8B, 8G, 8R emitted from the electron gun 9 in the horizontal and vertical directions is mounted. Then, the three electron beams 8B, 8 emitted from the electron gun 9 by the magnetic field generated by the deflection device 10
G, 8R are deflected in the horizontal and vertical directions, and the phosphor screen 3 is horizontally and vertically scanned through the apertures of the shadow mask 5 to display a color image.

The shadow mask 5 is shown in FIG.
As shown in (a), a shadow mask in which circular openings 12a are arranged on a line intersecting at an angle of 30 ° to the horizontal direction, and as shown in (b), rectangular openings 12b
There is a shadow mask in which a plurality of vertical holes are arranged in a straight line via a bridge 13, and a plurality of vertical openings are arranged in a horizontal line. In any of the shadow masks 5, the openings 12a and 12b are arranged at constant pitches PH and PV in the horizontal and vertical directions, and the openings 12a and 12b which are generally horizontally adjacent are shifted by PV / 2 in the vertical direction. I have.

The three-color phosphor layer of the phosphor screen is formed as a trio of a three-color phosphor layer that emits blue, green, and red light adjacent to the openings 12a, 12b of the shadow mask 5. If the shadow mask 5 has a circular opening, the three-color phosphor layer is formed in a dot shape, and if the opening is rectangular, the three-color phosphor layer is formed in a vertically long stripe shape.

In a conventional color cathode ray tube device, the phosphor screen is scanned by deflecting the electron beam at a relatively high frequency fH in the horizontal direction and a relatively low frequency fV in the vertical direction. In this case, as shown in FIG. 5, the scanning line 15 on the screen is inclined at an angle θ with respect to the horizontal axis (x axis),
The interval h between the adjacent scanning lines 15 is constant.

When a screen is scanned by such scanning lines 15, as shown in FIG. 6A, the electron beams 8 (8B, 8B) are used.
Assuming that the current density of G, 8R) is I (y) and its half-width is ds, the scanning lines 15 at the interval h have a uniform density of the current density I (y) in the vertical direction (y-axis direction). No. Therefore, as shown in FIG. 2B, the vertical interval is PV / 2.
When the light passes through the openings 12 (12a, 12b) of the shadow mask 5, optical interference occurs, and the light enters the phosphor screen 3 in a state in which a swell component is generated. As a result, the density of light emission of the phosphor layer 16 occurs, and the raster moiré 17 shown in FIG. 7 occurs, which deteriorates the visibility of an image.

As described above, in the ordinary color cathode ray tube device, moire fringes occur due to optical interference between the scanning lines and the apertures of the shadow mask. The moire fringes are affected by the vertical arrangement pitch of the openings of the shadow mask, the screen size, the display mode, and the focus performance. In general, moiré is more likely to occur as the focus performance is higher, regardless of the vertical arrangement pitch of the openings of the shadow mask, the screen size, and the display mode. Further, the vertical arrangement pitch of the openings of the shadow mask and the vertical arrangement pitch of the phosphor layer are closely related, and the moire fringes are formed by the vertical arrangement pitch of the openings of the shadow mask, the screen size, the display mode, and the like. Affected by focus performance. In general, moiré is more likely to occur as the focus performance is higher, regardless of the vertical arrangement pitch of the openings of the shadow mask, the screen size, and the display mode. Further, the vertical arrangement pitch of the openings of the shadow mask and the vertical arrangement pitch of the phosphor layers have a close relationship, and the moire fringes are, as described above, the distance h between the scanning lines and the vertical arrangement of the openings of the shadow mask. Direction arrangement pitch P
Depends on the relationship with V.

In recent years, color cathode ray tubes have been required to have higher focus performance, that is, higher performance display. Further, as a computer monitor, multi-scan correspondence capable of realizing various display modes (resolutions) with one monitor is standard.

In such a multi-mode display color cathode ray tube device, the intervals between scanning lines change depending on the display mode. Therefore, the vertical arrangement of the openings of the shadow mask so that moire fringes do not occur in all display modes. Pitch P
It is extremely difficult to select y. Further, even if the vertical arrangement pitch Py is selected so that moire fringes do not occur in a plurality of display modes, the setting is compromised,
It is difficult to avoid the occurrence of moire fringes in a certain mode.

[0010]

As described above, the color cathode ray tube apparatus of the shadow mask system has a possibility that moire fringes may occur due to the optical interference between the scanning line and the aperture of the shadow mask. . The most commonly used method of suppressing moire is to select the vertical arrangement pitch of the openings of the shadow mask so that the moire fringes are not noticeable.

However, such a method for suppressing moire is as follows.
There is a limit to the selection of the vertical arrangement pitch of the apertures due to the fineness of the shadow mask and structural restrictions. Further, in a recent multi-mode display color cathode ray tube device, since the interval between scanning lines changes depending on the display mode, even if the vertical arrangement pitch is selected so that moire fringes do not occur in a plurality of display modes, a certain mode may be selected. There is a problem that it is difficult to avoid the occurrence of moire fringes in the image.

As another method for making moire fringes inconspicuous, there is a method of breaking the regularity of the aperture arrangement of the shadow mask. However, such a method is not preferable in terms of screen uniformity. There is also a problem in the production of the shadow mask and in terms of strength.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and eliminates the need for a countermeasure against moiré in a color cathode ray tube itself, and can suppress moiré fringes without significantly changing the arrangement of apertures in a shadow mask. It is an object of the present invention to obtain a pipe device and a method for suppressing moire.

[0014]

SUMMARY OF THE INVENTION An electron gun, a deflecting device having a horizontal and vertical deflection coil for deflecting an electron beam emitted from the electron gun in horizontal and vertical directions, and a horizontal and vertical deflection coil respectively provided in the horizontal and vertical deflection coils. A deflection circuit for supplying a vertical deflection current, and deflects the electron beam emitted from the electron gun in the horizontal and vertical directions by the deflecting device, thereby forming a large number of apertures of a shadow mask formed in a predetermined arrangement. In a color cathode ray tube apparatus that horizontally and vertically scans a phosphor screen in which a large number of phosphor layers are provided in a predetermined arrangement via a predetermined circuit, a deflection circuit superimposes a small alternating current on a vertical deflection current to horizontally or horizontally shift an electron beam. A circuit was provided to make scanning lines on the phosphor screen by vertical scanning undulate with a minute amplitude.

In the method of suppressing moiré of a color cathode ray tube device, the moiré generated by optical interference between a scanning line on a phosphor screen by horizontal and vertical scanning of an electron beam and an opening of a shadow mask formed in a predetermined arrangement. Stripes,
By superimposing a minute alternating current on the vertical deflection current and making the scanning line undulate with a minute amplitude, the scanning line is made inconspicuous.

Further, the frequency of the minute AC current is set to an integral multiple of the horizontal deflection frequency.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a color cathode ray tube device as one embodiment thereof and its peripheral circuits.

The color cathode ray tube device has the same configuration as a conventional color cathode ray tube device, has an envelope composed of a panel 1 and a funnel 2, and has a light absorbing layer and a light absorbing layer on the inner surface of the panel 1. A phosphor screen 3 having a three-color phosphor layer that emits blue, green, and red light is provided so as to be embedded in gaps formed in a predetermined arrangement of light absorbing layers. Further, a shadow mask 5 having a large number of apertures formed in a predetermined arrangement on a surface 4 facing the phosphor screen 3 is disposed so as to face and approach the phosphor screen 3. On the other hand, three electron beams 8B, 8B are placed in the neck 7 of the funnel 2.
An electron gun 9 for emitting G, 8R is provided. A horizontal deflection coil for generating a horizontal deflection magnetic field for deflecting the three electron beams 8B, 8G, 8R emitted from the electron gun 9 in the horizontal direction by supplying a deflection current from the horizontal deflection circuit 20 to the outside of the funnel 2. Deflecting device 10 having a vertical deflecting coil for generating a vertical deflecting magnetic field for deflecting in the vertical direction by supplying a deflecting current from a vertical deflecting circuit 21
Is installed.

In this embodiment, in particular, a vertical synchronization signal 23 is supplied to the vertical deflection circuit 21 and a horizontal synchronization signal 24 supplied to the horizontal deflection circuit 20 is distributed so that a minute AC A circuit is provided for supplying a current in which the current is superimposed to the vertical deflection coil.

The vertical synchronization signal 23 is transmitted to the vertical deflection circuit 2
The voltage waveform forming circuit 25 forms a vertical deflection voltage waveform, and outputs the waveform signal to the waveform superimposing circuit 26. On the other hand, the vertical deflection circuit 2
1 is supplied to the frequency conversion circuit 2
7 and further output via a voltage waveform forming circuit 28 and an amplifying circuit 29 a signal which fluctuates with a small amplitude converted by the frequency converting circuit 27 to a waveform superimposing circuit 26. Then, the waveform superimposing circuit 26 superimposes a minute AC current that fluctuates at the minute amplitude on the vertical deflection current, and supplies the vertical deflection current on which the minute AC current is superimposed to the vertical deflection coil.

The frequency of the minute alternating current is preferably an integral multiple of the horizontal deflection frequency, that is, several times to several tens of times the horizontal deflection frequency.
z.

When the vertical deflection current on which the minute AC current is superimposed is supplied to the vertical deflection coil as described above, the scanning line 31 undulates with a minute amplitude as shown in FIG.
When the scanning line, which is originally a straight line, undulates at a very small amplitude in this manner, the electron beams 8B, 8G, 8R cause the shadow mask 5
, The optical interference between the scanning lines and the vertical arrangement of the openings of the shadow mask 5 can be dispersed in the vertical direction. Therefore,
The generation of raster moiré can be suppressed, and as a result, the visibility of moiré fringes can be reduced.

If the scanning line is made to undulate with a minute amplitude, the image quality is degraded in accordance with the amplitude and frequency. Therefore, it is necessary to set the amplitude and frequency of the scanning line within a range that does not impair image quality. In this regard, as described above, by using the horizontal synchronization signal 24 to obtain a minute AC current superimposed on the vertical deflection current, a minute AC current having a frequency several to several tens times the horizontal deflection frequency can be easily obtained. Can be obtained.

[0025]

As described above, by superimposing a minute alternating current on a vertical deflection current and causing a scanning line to undulate with a small amplitude, moire fringes caused by optical interference between the scanning line and the aperture of the shadow mask can be reduced. Therefore, it is possible to configure a color cathode ray tube apparatus in which moiré fringes are less likely to be generated without specially changing the arrangement of apertures of the shadow mask without the need for countermeasures against moire in the color cathode ray tube itself.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a color cathode ray tube device according to an embodiment of the present invention and a peripheral circuit thereof.

FIG. 2 is a diagram for explaining scanning lines of the color cathode ray tube device.

FIG. 3 is a diagram showing a configuration of a conventional color cathode ray tube device.

FIG. 4A is a diagram showing a hole arrangement of a shadow mask having a circular opening, and FIG. 4B is a diagram showing a hole arrangement of a shadow mask having a rectangular opening. is there.

FIG. 5 is a diagram for explaining scanning lines of a conventional color cathode ray tube device.

6A and 6B are diagrams for explaining the relationship between the current density of the electron beam and the aperture of the shadow mask. FIG. 6A is a diagram of the current density of the electron beam, and FIG. FIG. 3 is a diagram illustrating a state of an electron beam passing through a hole.

FIG. 7 is an explanatory diagram of moire fringes generated in a conventional color cathode ray tube device.

[Explanation of symbols]

 3 phosphor screen 5 shadow mask 8B, 8G, 8R 3 electron beam 9 electron gun 10 deflecting device 31 scanning line

Claims (3)

[Claims] 1. A deflection device having an electron gun, a horizontal and vertical deflection coil for deflecting an electron beam emitted from the electron gun in horizontal and vertical directions, and a horizontal and vertical deflection current supplied to the horizontal and vertical deflection coils, respectively. And a deflection circuit for supplying an electron beam emitted from the electron gun in the horizontal and vertical directions by the deflecting device. In a color cathode ray tube apparatus for horizontally and vertically scanning a phosphor screen having a large number of phosphor layers provided thereon, the deflection circuit is superimposed with a small alternating current on the vertical deflection current to horizontally and vertically shift the electron beam. A color cathode ray tube device comprising a circuit for undulating scanning lines on a phosphor screen by scanning with a minute amplitude. 2. Moire fringes generated by optical interference between a scanning line on a phosphor screen by horizontal and vertical scanning of an electron beam and apertures of a shadow mask formed in a predetermined arrangement are converted into a minute deflection current by a vertical deflection current. A method of suppressing moire in a color cathode ray tube device, wherein the scanning lines are superposed on each other to make the scanning lines undulate with a very small amplitude. 3. The method according to claim 2, wherein the frequency of the minute alternating current is an integral multiple of the horizontal deflection frequency.