JP2000113834A - Deflection device for flat cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a keystone distortion by making a pair of horizontal deflection coils of a deflection yoke different in structure without using a keystone distortion correcting circuit in the deflection device for a flat cathode-ray tube. SOLUTION: In the deflection device for a flat cathode-ray tube having a screen 14 extended to obliquely cross the axis of an electron gun 3, a pair of horizontal deflection coils 11a, 11b of a deflection yoke 10 deflecting the electron beam 5 emitted from the electron gun 3 are made different in structure, thus the upper deflection magnetic field and the lower deflection magnetic field formed by a pair of horizontal deflection coils 11a, 11b are made different in strength to correct the keystone distortion of an image plane 17 formed on the screen 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat cathode ray tube deflecting device, and more particularly, to a flat type cathode ray tube which corrects keystone distortion by changing the structure of upper and lower horizontal deflection coils of a deflection yoke. And a deflection device.

[0002]

2. Description of the Related Art Conventionally, there is a flat cathode ray tube (CRT) having a configuration shown in FIG. Flat type CRT25
Is the screen panel 2 that crosses the axis 28 of the electron gun at an angle
9. The electron beam 27 emitted from the electron gun 26 is deflected horizontally and vertically from a deflection center O ′ by a deflection yoke 31, hits a phosphor screen 32 of a screen panel 29, causes a phosphor to emit light, and is formed on the phosphor screen 32. The displayed image can be viewed from the direction of arrow A or the direction of arrow B opposite to the fluorescent screen 32 with the axis 28 of the electron gun interposed therebetween.

Since the electron beam is irradiated on the fluorescent screen 32 obliquely intersecting with the axis 28 of the electron gun, the traveling distance of the electron beam irradiated on the position H on the upper part of the screen is the position L on the lower part of the screen.
It has an extremely long traveling distance compared to the traveling distance of the electron beam irradiated to the. FIG. 8 shows such a flat CR.
FIG. 3 is a schematic diagram illustrating a raster (one surface formed of scanning lines) formed by T. As shown in FIG. 8, in the flat type CRT 25, the fluorescent screen 32 is inclined with respect to the electron gun 26.
The raster 35, which is one surface formed by the scanning lines, has a trapezoidal shape that spreads upward. The trapezoidal distortion of the raster 35 is called keystone distortion.

[0004]

In order to correct the keystone distortion as described above, a horizontal deflection angle .alpha.
1 may be reduced, and the horizontal deflection current may be changed so that the horizontal deflection angle α2 increases at the bottom of the screen. Therefore,
The problem is solved by inserting a keystone distortion correction circuit to reduce the upper horizontal deflection amount and increase the lower horizontal deflection amount.

FIG. 9 is an image diagram of a horizontal deflection current corrected by the keystone distortion correction circuit. The rectangular line in the figure shows a line connecting the peaks of the horizontal sawtooth wave of the horizontal deflection current.By superimposing the control signal on the horizontal deflection current, the amplitude is small at the top of the vertical period, The amplitude increases.

In the keystone distortion correction method using the keystone distortion correction circuit as described above, the correction circuit is complicated, and a keystone distortion correction circuit whose circuit design is difficult is inserted to correct the keystone distortion in the horizontal deflection current. However, there is a problem that the cost is increased because the current is superimposed, reliability is lowered due to an increase in circuit components, and power consumption is increased. Further, a mounting space is required on the substrate for the keystone distortion correction circuit, and the mounting space for the substrate must be increased accordingly.

Accordingly, the present invention provides a flat-type cathode ray tube deflecting device capable of correcting keystone distortion by using different structures of horizontal deflection coils above and below a deflection yoke without using a keystone distortion correction circuit. It is intended to do so.

[0008]

According to the present invention, there is provided a flat-type cathode ray tube deflecting device having a screen extending obliquely with respect to the axis of an electron gun. By changing the structure of the pair of horizontal deflection coils of the deflection yoke that deflects the electron beam to be made, the intensity of the upper magnetic field and the lower magnetic field of the deflection magnetic field formed by the pair of horizontal deflection coils are changed, The keystone distortion of a screen formed on the screen is corrected.

In the flat-type cathode ray tube deflecting device according to the present invention, the intensity of the upper magnetic field and the lower magnetic field of the deflection magnetic field formed by the pair of horizontal deflection coils are different.
The horizontal deflection amount is different between the upper part and the lower part, and the keystone distortion is corrected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a flat type cathode ray tube deflector according to the present invention will be described below with reference to the drawings. FIG. 1 is a side view of a flat cathode ray tube to which a deflection device according to the present invention is applied. The bulb 2 of the flat CRT 1 has a screen panel 7 obliquely intersecting with the axis 6 of the electron gun. The electron beam 5 emitted from the cathode 8 of the electron gun 3 is applied to horizontal deflection coils 11 a,
At the same time as the light is deflected in the horizontal direction by 11b, the light is deflected in the vertical direction by the left and right vertical deflection coils 12a and 12b, and is scanned on the fluorescent screen 14 of the screen panel 7. A screen formed on the phosphor screen 14 is provided with a transparent and flat window 15 provided on the opposite side to the phosphor screen 14 with respect to the axis 6 of the electron gun.
It can be seen from. The present invention corrects the keystone distortion, which is a trapezoidal distortion in which the screen on the fluorescent screen 14 spreads out on the upper side. Therefore, the structure of the horizontal deflection coils 11a and 11b above and below the deflection yoke 10 without using a keystone distortion correction circuit. For example, the keystone distortion is corrected by changing the turn ratio.

FIG. 2 is a diagram showing the trajectory of the electron beam and the overall image. The electron beam 5 emitted from the cathode 8 of the electron gun 3 is horizontally deflected from the deflection center O by horizontal deflection coils 11a and 11b above and below the deflection yoke 10, and is vertically deflected by left and right vertical deflection coils 12a and 12b. The light is deflected and scanned on the phosphor screen 14 to form a raster 17 which is one surface composed of the scanned scanning lines.

FIG. 3 is a diagram showing a raster 17 formed on the fluorescent screen 14. The uncorrected raster 18 formed on the phosphor screen 14 indicated by the dotted line in FIG. 3 causes an arc distortion 19 due to the deflection distortion at the upper position and the lower position, and the horizontal left and right edges of the raster 18 are sector-shaped. This results in a tilting distortion, that is, a keystone distortion 20. That is, the raster distortion is composed of the arc distortion 19 and the keystone distortion 20, but the arc distortion 19 at the upper position of the raster 18 can be reduced as the upper position approaches the axis of the electron gun of the flat type CRT.

FIG. 4 is an explanatory diagram showing a change in the amount of horizontal deflection by the horizontal deflection coils above and below the deflection yoke depending on the location. A horizontal coil magnetic field is generated between the upper and lower horizontal deflection coils 11a and 11b. The number of turns of the upper horizontal deflection coil 11a is N
1. Since the number of turns of the lower horizontal deflection coil 11b is N2 and the turn ratio is N1 <N2, the magnetic field distribution at the neck of the flat type CRT is weak at the top and strong at the bottom. In the figure, the length of the arrow indicates the amount of deflection of the electron beam when the turn ratio N1 <N2. The amount of deflection is small at the upper part and large at the lower part. The left and right vertical deflection coils 1 are applied to this electron beam.
When a vertical deflection magnetic field is applied by 2a and 12b, keystone distortion correction is applied from the upper part to the lower part of the screen. That is, as shown in FIG. 3, since the amount of deflection of the electron beam is small at the upper position of the screen, the electron beam is deflected at a small deflection angle in the horizontal direction, and the amount of deflection of the electron beam is large at the lower position of the screen. The electron beam is deflected in the horizontal direction at a large deflection angle, and the keystone distortion is corrected to form a substantially rectangular raster 17 as shown by the solid line.

FIG. 5 is an image diagram of the horizontal deflection current in the present invention. The rectangular line in the figure shows a line connecting the peaks of the horizontal sawtooth wave of the horizontal deflection current, nothing is superimposed on the horizontal deflection current, and the amplitude is the same from the top to the bottom of the vertical period It is shown that.

FIG. 6 is a diagram showing a raster when the ratio of the winding ratio of the upper horizontal deflection coil to the lower horizontal deflection coil is increased. If the ratio of the number of turns of N1 <N2 of the horizontal deflection coil is increased, the arc distortion may increase at the upper position 21a and the lower position 21b of the raster 21.
In such a case, the arc distortion can be reduced by reducing the ratio of the number of turns of N1 <N2 of the horizontal deflection coil and using it together with a keystone distortion correction circuit having a small correction amount. Therefore, when used together with the keystone distortion correction circuit, the correction amount of the keystone distortion correction circuit may be small, and accordingly, an inexpensive device can be used, the cost can be reduced, and the reliability can be improved.

Therefore, since the winding ratio of the number of turns N1 of the upper horizontal deflection coil 11a and the number of turns N2 of the lower horizontal deflection coil 11b is set to satisfy the relationship of N1 <N2, the magnetic field distribution in the neck portion of the flat type CRT has an upper part. Since the lower portion is weaker and stronger, that is, the deflection amount is smaller at the upper portion and larger at the lower portion, the keystone distortion can be effectively corrected.

Further, since a keystone distortion correction circuit having a complicated correction circuit and difficult circuit design is not required, the number of circuit components can be reduced and the cost can be reduced. The reliability is improved by not using the keystone distortion correction circuit.
The power consumption is small, and the substrate mounting space for the keystone distortion correction circuit is not required.

When used in combination with the keystone distortion correction circuit, the amount of correction of the keystone distortion correction circuit may be smaller than when the keystone distortion correction circuit is used alone. And reliability can be improved.

In the above-described embodiment, by changing the turn ratio of the horizontal deflection coils above and below the deflection yoke,
The keystone distortion is corrected by making the magnetic field distribution of the neck portion of the flat CRT weaker at the upper portion and stronger at the lower portion, but the present invention is not limited to this. The keystone distortion may be corrected by making the magnetic field distribution at the neck of the CRT weaker at the upper part and stronger at the lower part.

Further, in the above-described embodiment, the upper end of the raster is located near the axis of the electron gun. However, the present invention is not limited to this, and it goes without saying that the upper end of the raster may be coincident with the axis of the electron gun. .

[0021]

As described above, according to the present invention,
The keystone distortion is corrected by changing the upper and lower structures of the deflection yoke so that the magnetic field distribution is weaker at the upper part and stronger at the lower part, eliminating the need for a keystone distortion correction circuit and reducing the number of circuit components. Cost can be reduced.

By not using the keystone distortion correction circuit,
Reliability is improved, power consumption is reduced, heat generation is reduced, and no space is required for mounting a substrate for a keystone distortion correction circuit.

Further, in the case where the keystone distortion correction circuit is used in combination, the amount of correction of the keystone distortion correction circuit may be smaller than in the case where the keystone distortion correction circuit is used alone.
Accordingly, inexpensive devices can be used, cost can be reduced, and reliability can be improved.

[Brief description of the drawings]

FIG. 1 shows a flat CRT to which a deflection device according to the present invention is applied.
It is a side view which shows as a partial cross section.

FIG. 2 is a diagram illustrating the trajectory of an electron beam and an overall image.

FIG. 3 is a schematic diagram illustrating a raster formed by a flat type CRT.

FIG. 4 is an explanatory diagram showing a change in a horizontal deflection amount depending on a position by a horizontal deflection coil above and below a deflection yoke according to the present invention.

FIG. 5 is an image diagram of a horizontal deflection current in the present invention.

FIG. 6 is a schematic diagram illustrating a raster when a ratio of a winding ratio of an upper horizontal deflection coil to a lower horizontal deflection coil is increased.

FIG. 7 is a side sectional view of a conventional flat type CRT.

FIG. 8 is a schematic diagram illustrating a raster formed by performing normal deflection on a flat-type CRT.

FIG. 9 is an image diagram of a horizontal deflection current corrected by a keystone distortion correction circuit.

[Explanation of symbols]

Reference Signs List 1 flat CRT, 2 valve, 3 electron gun, 5 electron beam, 6 axis of electron gun, 8
· Cathode, 10 ... deflection yoke, 11a ... upper horizontal deflection coil, 11b ... lower horizontal deflection coil, 12a
... left vertical deflection coil, 12b ... right vertical deflection coil, 14 ... fluorescent screen, 17 ... raster, 19 ...
Arc distortion, 20: Keystone distortion, 21: Raster, O: Deflection center

Claims (3)

[Claims] 1. A flat cathode ray tube deflecting device having a screen extending so as to obliquely intersect with an axis of an electron gun, wherein a deflection yoke deflects an electron beam emitted from the electron gun. By making the structures different, the intensity of the upper magnetic field and the lower magnetic field of the deflection magnetic field formed by the pair of horizontal deflection coils are made different to correct the keystone distortion of the screen formed on the screen. Characteristic deflection device for flat type cathode ray tube. 2. The flat-type cathode ray tube deflecting device according to claim 1, wherein the keystone distortion is corrected by changing a winding ratio of a pair of horizontal deflection coils of the deflection yoke. 3. The deflecting device according to claim 1, wherein the deflecting device includes a keystone distortion correction circuit for correcting keystone distortion.