JPH11187283A - Image distortion correcting device for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct pin cushion distortion of a middle part, with a simple configuration. SOLUTION: This correcting device comprises a core 16 around which first and second coils 6 and 8, which form a pair and 3rd and 4th coils 10 and 11 which form a pair are wound and a saturable reactor 4 that is formed by serially connecting the coils 6 and 10, and the coils 8 and 12 respectively. A serial circuit of the coils 6 and 10 is connected serially to a horizontal deflection coil, and a vertical deflection current that is supplied to the vertical deflection coil or a current, which changes similarly to the vertical deflection current is supplied to a serial circuit of the coils 8 and 12. Also, when the coils 6 and 8 produce magnetic fields in the same direction, each coil of the coils 10 and 12 is connected with polarities that produce magnetic fields which are in mutually opposite directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for correcting a display image distortion in a cathode ray tube.

[0002]

2. Description of the Related Art When an image is displayed by performing a raster scan with a cathode ray tube, the length of the horizontal scanning line is limited by the length of the screen because the fluorescent screen of the cathode ray tube is formed as a substantially flat surface or a spherical surface having a large radius of curvature. The closer to the top and bottom, the longer the
Pincushion distortion occurs in which the left and right central portions of the screen are constricted. Therefore, conventionally, the pincushion distortion has been eliminated by connecting a capacitor for correcting pincushion distortion in series to the horizontal deflection coil and making the current waveform flowing in the horizontal deflection coil into an S-shape.

[0003]

However, in such a conventional correction method, although the left and right ends of the screen are straight, the distortion can be eliminated, but the horizontal deflection angle of the electron beam is smaller than the maximum deflection angle. In, pincushion distortion remains. FIG. 9 is an explanatory view showing the pincushion distortion of the intermediate portion. In the drawing, two curves 110 and 112 are displayed between a center line 104 and left and right end portions 106 and 108 on a screen 102 of a cathode ray tube. These curves 110 and 112 are originally vertical. Are displayed as curved lines 110 and 112 as shown in the figure as a result of the pincushion distortion.

[0004] Here, the region between the center line 104 and the left and right ends 106 and 108, particularly the curves 110 and 1
A region slightly closer to the end where 12 is displayed is referred to as an intermediate portion. An image distortion correction device for eliminating the above-described pincushion distortion in the intermediate portion is disclosed in Japanese Patent Application Laid-Open No. 09-14928.
3, the structure is complicated because the number of required coils is as large as six and a pair of permanent magnets is required. SUMMARY OF THE INVENTION It is an object of the present invention to provide a cathode ray tube image distortion correcting apparatus which can correct pincushion distortion in an intermediate portion with a simple configuration.

[0005]

In order to achieve the above object, the present invention is an apparatus for correcting image distortion in a cathode ray tube displaying an image by deflecting and scanning an electron beam by a horizontal deflection coil and a vertical deflection coil. , A pair of first and second coils, and a pair of third and fourth coils wound around a core, the first and third coils;
And a saturable reactor formed by connecting the second and fourth coils in series, respectively, wherein a series circuit of the first and third coils is connected in series with the horizontal deflection coil, and the second and fourth coils are connected in series. A vertical deflection current to be supplied to the vertical deflection coil or a current that changes similarly to the vertical deflection current is supplied to the series circuit of the fourth coil, and the first and second coils generate a magnetic field in the same direction. At this time, the third and fourth coils are connected to each other with polarities that generate magnetic fields in opposite directions.

Therefore, the image distortion correcting apparatus for a cathode ray tube according to the present invention, by appropriately designing the saturation characteristics of the saturable reactor, can increase the absolute value of the vertical deflection current flowing through the second and fourth coils. One of the first and third coils may have a very small inductance due to saturation of the saturable reactor, while the other may have a large inductance when the saturable reactor operates in an unsaturated state. Therefore, at this time, the sum of the inductances of the first and third coils increases as the absolute value of the vertical deflection current increases. Since the first and third coils are connected in series with the horizontal deflection coil, when the absolute value of the vertical deflection current increases, that is, when the vertical deflection angle increases, the horizontal deflection angle of the electron beam decreases. As a result, the pincushion distortion in the middle part is corrected.

In addition, by appropriately designing the saturation characteristics of the saturable reactor, the electron beam is allowed to have a maximum horizontal deflection angle,
Alternatively, when it is deflected to an angle close to the maximum horizontal deflection angle, the horizontal deflection current flowing in the first and third coils at that time causes the magnitude and direction of the vertical deflection current flowing in the second and fourth coils to change. Regardless, the saturable reactor can be operated in saturation. Therefore, at this time, the sum of the inductances of the first and third coils is very small, and the horizontal deflection coil operates in almost the same state as when the saturable reactor is not connected. The state where the cushion distortion is corrected is maintained. That is, the pincushion distortion in the middle portion is corrected while the shape of the left and right ends of the screen remains unchanged.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a structural view showing an example of an image distortion correcting device for a cathode ray tube according to the present invention, and FIG.
FIG. 2 is a circuit diagram around a deflection coil including an image distortion correction device for a cathode ray tube. As shown in FIG. 1, the image distortion correcting apparatus 2 for a cathode ray tube corrects pincushion distortion in an intermediate portion in a cathode ray tube displaying an image by deflecting and scanning an electron beam by a horizontal deflection coil and a vertical deflection coil. Saturable reactor 4. The saturable reactor 4 includes a pair of first and second saturable reactors.
Are wound around a core 16 on which a magnetic gap 14 is formed, and the first and third coils 6, 10 and the second and fourth coils 6 and 8, and a pair of third and fourth coils 10 and 12, The fourth coils 8 and 12 are formed by connecting them in series. First and third coils 6,
The number of turns of 10 is equal to each other, and the number of turns of the second and fourth coils 8 and 12 is equal to each other.

Then, the first and third coils 6, 10
2 is connected in series with two horizontal deflection coils 18 and 20 connected in parallel as shown in FIG. 2, and the series circuit of the second and fourth coils 8 and 12 includes a vertical deflection coil. The vertical deflection current (sawtooth wave) supplied to the coil is applied to terminal 2
2, 24. Horizontal deflection coils 18, 20 of a series circuit of first and third coils 6, 10
One terminal of the capacitor 26 for pincushion distortion correction described above is connected to the end opposite to the above, and the terminal on the opposite side of the capacitor 26 is grounded. The terminals of the horizontal deflection coils 18 and 20 opposite to the saturable reactor 4 are connected to a horizontal deflection circuit (not shown), and the horizontal deflection coils 18 and 20 supply a horizontal deflection current of a sawtooth wave to the horizontal deflection coils 18 and 20. Is supplied.

When the first and second coils 6 and 8 generate magnetic fields in the same direction, the third and fourth coils 10 and 12 are connected to each other with polarities that generate magnetic fields in opposite directions. Have been. More specifically, when the current IH flows through the first and third coils 6 and 10 in the directions indicated by arrows in FIG. 1, magnetic fluxes φ1 and φ3 in the directions shown in FIG. When the IV flows through the second and fourth coils 8 and 12 in the directions of the arrows, magnetic fluxes φ2 and φ4 in the directions shown in the drawing are generated. The directions of φ1 and φ2 are equal, and the directions of φ3 and φ4 are opposite to each other.

Next, the characteristics of the saturable reactor 4 will be described. FIG. 3 is a graph showing a change in the inductance of the first coil 6, where the vertical axis represents the inductance of the first coil 6, and the horizontal axis represents the current obtained by adding the currents flowing through the first and second coils 6, 8. It represents the absolute value | IH + IV |. As shown in FIG. 3, when | IH + IV | is zero, the inductance of the first coil 6 is the largest, and | IH + IV |
The inductance gradually decreases as IV | increases. When | IH + IV | is IS, the saturable reactor 4 is almost saturated, and in the region above IS, the first
The inductance of the coil 6 is very low and substantially constant. This IS is equal to the absolute value of the horizontal deflection current that deflects the electron beam to approximately half the maximum horizontal deflection angle in this embodiment.

FIG. 4 is a graph showing a change in the inductance of the third coil 10, wherein the vertical axis represents the inductance of the third coil 10, and the horizontal axis represents the absolute value of the current | IH-I.
V | represents current. The shape of the curve representing the inductance is the same as that of FIG. 3, and only the horizontal axis is different.
As shown in FIG. 4, when | IH-IV | is zero, the inductance of the third coil 10 is the largest, and | IH-I
The inductance gradually decreases as V | increases.
When | IH-IV | is the above IS, the saturable reactor 4 is almost saturated, and in the region above IS, the first
The inductance of the coil 6 is very low and substantially constant. Therefore, the second and fourth coils 8, 1
2, no current flows, while the first and third coils 6,
When a current IS for deflecting the electron beam to an angle approximately half of the maximum horizontal deflection angle is supplied to the series circuit 10, the saturable reactor 4 is substantially saturated.

When a current for deflecting the electron beam to the maximum horizontal deflection angle is passed through the series circuit of the first and third coils 6 and 10, the series circuit of the second and fourth coils 8 and 12 flows through the series circuit. Regardless of the magnitude and direction of the flowing current, the saturable reactor 4 operates in a saturation region. This will be described in more detail later. Such characteristics of the saturable reactor 4 can be realized by appropriately setting the cross-sectional area of the core 16, the material of the core 16, the number of turns of each coil, the interval between the magnetic gaps 14, and the like.

Next, the operation of the image distortion correcting apparatus 2 for a cathode ray tube, that is, the saturable reactor 4 configured as described above will be described. FIG. 5A shows a screen 102 of a cathode ray tube.
FIG. 3B is an explanatory diagram showing the position of an electron beam spot (also simply referred to as a beam spot) above, and FIG.
And (C) is a graph showing the inductance of the third coil 10. FIGS. 5B and 5C are basically the same as FIGS. 3 and 4, respectively, with the ordinate representing the inductance and the abscissa representing the current | IH + IV | and the current | IH-IV |, respectively. .

In FIG. 5A, a position A0 indicates the position of the beam spot when the electron beam is not deflected in the vertical direction but is deflected only in the horizontal direction to an angle almost half of the maximum horizontal deflection angle. ing. On the other hand, the positions A1 and A2 are
The horizontal direction indicates the position of the beam spot when the electron beam is deflected similarly to the case of A0, and the vertical direction indicates the position of the beam spot when the electron beam is deflected to the upper and lower maximum vertical deflection angles.

When the position of the beam spot is A0,
Since the electron beam is deflected to approximately half the maximum horizontal deflection angle, the first and third coils 6,
The horizontal deflection currents I1A0 and I3A0 flowing through 10 are equal to the above-described current IS. Accordingly, the saturable reactor 4 is almost saturated, and as shown in FIGS. 5B and 5C, the inductance L1A0 of the first coil 6 and the inductance L3A0 of the third coil 10 are both very high. It is a small value. Therefore, the first and third
Have almost no effect on the current flowing through the horizontal deflection coil, and the horizontal deflection coil operates in almost the same state as when the first and third coils 6, 10 are not connected. Therefore, the image does not deform near the position A0.

On the other hand, when the position of the beam spot is A1, the electron beam is deflected to almost half the maximum horizontal deflection angle and at the same time is deflected upward to the maximum vertical deflection angle, so that the current | IH + IV | Is I1A1 obtained by adding the vertical deflection current to the current IS, as shown in FIG. 5B. Since the saturable reactor 4 operates in the saturation region, the inductance L1A1 of the first coil 6 becomes very large. It becomes a small value. Conversely, the value of the current | IH-IV | is I3A1 obtained by subtracting the vertical deflection current from the current IS, as shown in FIG. 5C, and the saturable reactor 4 operates in the non-saturation region. The inductance L3A1 of the third coil 10 has a large value. Then, at a position between the position A0 and the position A1, the inductance of the third coil 10 is an intermediate value between the value in the case of the position A0 and the value in the case of the position A1, and increases as the position approaches the position A1. . Therefore, as the position of the beam spot approaches the position A1 from the position A0, the inductance of the first coil 6 keeps a small value, but the inductance of the third coil 10 gradually increases. The flowing current gradually decreases. As a result, as the position approaches the position A1, the horizontal deflection angle gradually decreases, the curvature of the curve 112 shown in FIG. 9 is corrected, and the pincushion distortion in the middle portion is eliminated.

When the position of the beam spot is A2, the electron beam is deflected to almost half of the maximum horizontal deflection angle and at the same time is deflected downward to the maximum vertical deflection angle, so that the current | IH + IV | Is I1A2 obtained by subtracting the vertical deflection current from the current IS as shown in FIG. 5B. Since the saturable reactor 4 operates in the non-saturation region, the inductance L1A2 of the first coil 6 is obtained.
Is a large value. At a position between the position A0 and the position A2, the inductance of the first coil 6 is
It is an intermediate value between the value for 0 and the value for position A2,
The value becomes larger as approaching the position A2. Conversely, the value of the current | IH-IV | is, as shown in FIG.
I3A2 is obtained by adding the vertical deflection current to the current IS. Since the saturable reactor 4 operates in the saturation region, the inductance L3A2 of the third coil 10 has a very small value. Therefore, as the position of the beam spot approaches from the position A0 to the position A2, the inductance of the third coil 10 keeps a small value, but the inductance of the first coil 6 gradually increases. The flowing current gradually decreases. As a result, as the position approaches the position A2, the horizontal deflection angle gradually decreases, the curvature of the curve 112 shown in FIG. 9 is corrected, and the pincushion distortion in the middle portion is eliminated. Pincushion distortion in the middle part on the left side of the screen is also eliminated.

FIG. 6A is an explanatory view showing the position of an electron beam spot on the screen 102 of the cathode ray tube, and FIG.
Is a graph showing the inductance of the first coil 6,
(C) is a graph showing the inductance of the third coil 10. FIGS. 6B and 6C show FIGS. 3 and 4 respectively.
And the vertical axis represents the inductance and the horizontal axis represents the current | IH + IV | and the current | I, respectively.
H-IV |.

As shown in FIG. 6A, when the position of the beam spot is A0 ', the electron beam is deflected to almost half the maximum horizontal deflection angle. The horizontal deflection currents I1A0 'and I3A0' flowing through the three coils 6 and 10 are equal to the current IS described above.
Therefore, the saturable reactor 4 is almost saturated,
As shown in FIGS. 6B and 6C, the first coil 6
The inductance L1A0 'of the third coil 10 and the inductance L3A0' of the third coil 10 are both very small values. Therefore, the first and third coils 6, 10
Has almost no effect on the current flowing through the horizontal deflection coil, and the horizontal deflection coil has first and third coils 6,
10 operates in almost the same state as when it is not connected. Therefore, the image is not deformed near the position A0 '.

On the other hand, when the position of the beam spot is A1 ', the electron beam is deflected to almost half the maximum horizontal deflection angle and at the same time is deflected upward to the maximum vertical deflection angle, so that the current | IH + IV | Is the current IH
Is opposite to the above case, and as shown in FIG. 6B, I1 obtained by subtracting the vertical deflection current from the current IS
A1 ′, and the inductance L1A1 ′ of the first coil 6 becomes a large value because the saturable reactor 4 operates in the unsaturated region. At a position between the position A0 ′ and the position A1 ′, the inductance of the first coil 6 is
The value becomes an intermediate value between the value in the case of 0 'and the value in the case of the position A1', and becomes a larger value as approaching the position A1 '. Conversely, the value of the current | IH-IV | is I3A1 obtained by adding the vertical deflection current to the current IS, as shown in FIG. 6C, since the direction of the current IH is opposite to that described above. And the inductance L3A1 'of the third coil 10 becomes a very small value because the saturable reactor 4 operates in the saturation region. Therefore, the position of the beam spot is
0 ′, as the position approaches the position A1 ′, the third coil 1
Although the inductance of 0 maintains a small value,
The inductance of the coil 6 gradually increases, so that the current flowing through the horizontal deflection coil gradually decreases. As a result, the horizontal deflection angle becomes gradually smaller as approaching the position A1 ', and the curve 110 shown in FIG.
Is corrected, and the pincushion distortion at the intermediate portion is eliminated.

When the position of the beam spot is A2 ', the electron beam is deflected to almost half the maximum horizontal deflection angle and at the same time is deflected downward to the maximum vertical deflection angle, so that the current | IH + IV The value of | becomes I1A2 'obtained by adding the vertical deflection current to the current IS as shown in FIG. 6B, and the inductance L1A2' of the first coil 6 because the saturable reactor 4 operates in the saturation region.
Is a very small value. Conversely, the value of the current | IH-IV | is I3A2 'obtained by subtracting the vertical deflection current from the current IS, as shown in FIG.
Operates in a non-saturation region, the inductance L3A2 ′ of the third coil 10 has a large value. And position A
In the position between 0 ′ and the position A2 ′, the inductance of the third coil 10 is equal to the value in the position A0 ′ and the position A2 ′.
The value becomes an intermediate value between the values in the case of and the value becomes larger as approaching the position A2 ′. Therefore, as the position of the beam spot approaches from the position A0 'to the position A2', the inductance of the first coil 6 keeps a small value, but the inductance of the third coil 10 gradually increases, so that the horizontal deflection The current flowing through the coil gradually decreases. As a result, as the position approaches the position A2 ', the horizontal deflection angle gradually decreases, the curvature of the curve 110 shown in FIG. 9 is corrected, and the pincushion distortion in the middle portion is eliminated.

Next, the case where the electron beam is deflected to the maximum horizontal deflection angle will be described. 7A is an explanatory diagram showing the position of the electron beam spot on the screen of the cathode ray tube, FIG. 7B is a graph showing the inductance of the first coil 6, and FIG. 7C is the graph showing the inductance of the third coil 10. FIG. FIGS. 7B and 7C are basically the same as FIGS. 3 and 4, respectively, with the vertical axis representing inductance and the horizontal axis representing current | IH + IV | and current | IH-IV |, respectively. . In FIG. 7B, position B0 does not deflect the electron beam in the vertical direction,
The position of the beam spot when the beam is deflected to the maximum horizontal deflection angle only in the horizontal direction to the right is shown. On the other hand, the positions B1 and B2 indicate the positions of the beam spots when the electron beam is deflected in the horizontal direction as in the case of B0 and when the electron beam is deflected to the upper and lower maximum vertical deflection angles, respectively. ing.

When the position of the beam spot is B0,
Since the electron beam is deflected to the maximum horizontal deflection angle, the horizontal deflection currents I1B0 and I3B0 flowing through the first and third coils 6 and 10 at this time are almost equal to twice the current IS described above. Therefore, the saturable reactor 4 operates in a saturated state, and as shown in FIGS. 7B and 7C, the inductance L1B0 of the first coil 6 and the inductance L3B0 of the third coil 10 are both very high. It is a small value. Therefore, the first and third coils 6, 10 have almost no effect on the current flowing in the horizontal deflection coil, and the horizontal deflection coil is almost the same as when the first and third coils 6, 10 are not connected. Works in the same state. Therefore, the image is not deformed near the position B0.

On the other hand, when the position of the beam spot is B1, the electron beam is deflected rightward to the maximum horizontal deflection angle and upward to the maximum vertical deflection angle, so that the current | IH + IV | Is a value obtained by adding the vertical deflection current to the current I1B0, as shown in FIG.
1B1, and since the saturable reactor 4 operates in the saturation region, the inductance L1B1 of the first coil 6 has a very small value. As shown in FIG. 7C, the value of the current | IH-IV | is I3B1 obtained by subtracting the vertical deflection current from the current I3B0, and is smaller than the current I3B0, but is larger than the current IS and is saturable. Since the reactor 4 operates in the saturation region, the inductance L3B1 of the third coil 10 has a very small value.

When the position of the beam spot is B2, the electron beam is deflected rightward to the maximum horizontal deflection angle and downward to the maximum vertical deflection angle, so that the current | IH + IV | Is the value of (B) in FIG.
As shown in (1), the current I1B0 is equal to I1B2 obtained by subtracting the vertical deflection current, which is smaller than the current I1B0 but larger than the current IS. This is a very small value. The value of the current | IH-IV |
As shown in FIG. 7C, the current becomes I3B2 obtained by adding the vertical deflection current to the current I3B0. Since the saturable reactor 4 operates in the saturation region, the inductance L3B2 of the third coil 10 has a very small value. . As described above, when a current for deflecting the electron beam to the maximum horizontal deflection angle is supplied to the series circuit of the first and third coils 6 and 10, the current flows to the series circuit of the second and fourth coils 8 and 12. Regardless of the magnitude and direction of the current, the saturable reactor 4 operates in a saturation region. Therefore, when the electron beam is deflected to the maximum horizontal deflection angle or an angle close to the maximum horizontal deflection angle, the inductance of the first and third coils 6, 10 is very small regardless of the vertical deflection angle. Value. As a result, the first and third coils 6,
10 has almost no effect on the current flowing in the horizontal deflection coil, and the horizontal deflection coil operates in almost the same state as when the first and third coils 6, 10 are not connected. Therefore, in the vicinity of the right end of the screen, the image is not deformed, and the state where the pincushion distortion at the right end of the screen is corrected is maintained.

The same applies to the left end of the screen. FIG. 8A is an explanatory diagram showing the position of an electron beam spot on the screen 102 of the cathode ray tube, and FIG.
And (C) is a graph showing the inductance of the third coil 10.
FIGS. 8B and 8C are basically the same as FIGS. 3 and 4, respectively, with the vertical axis representing inductance and the horizontal axis representing current | IH + IV | and current | IH-IV |, respectively. . In FIG. 8B, a position B0 'indicates the position of the beam spot when the electron beam is not deflected in the vertical direction but is deflected only in the horizontal direction to the left to the maximum horizontal deflection angle. On the other hand, positions B1 'and B2'
Indicates the position of the beam spot when the electron beam is deflected in the horizontal direction in the same manner as in the case of B0 ', and in the vertical direction, the electron beam is deflected to the upper and lower maximum vertical deflection angles.

When the position of the beam spot is B0 ', since the electron beam has been deflected to the maximum horizontal deflection angle, the horizontal deflection current I1B0', which flows through the first and third coils 6, 10 at this time, I3B0 'is approximately equal to twice the current IS described above. Therefore, the saturable reactor 4 operates in a saturated state, and as shown in FIGS. 8B and 8C, the inductance L1B0 ′ of the first coil 6
And the inductance L3B0 ′ of the third coil 10 has a very small value. Therefore, the first and third coils 6, 10 have almost no effect on the current flowing in the horizontal deflection coil, and the horizontal deflection coil is almost the same as when the first and third coils 6, 10 are not connected. Works in the same state. Therefore, the image is not deformed near the position B0 ′.

On the other hand, when the position of the beam spot is B1 ', since the electron beam is deflected to the maximum horizontal deflection angle and upward to the maximum vertical deflection angle, the value of the current | IH + IV | Becomes I1B1 'obtained by subtracting the vertical deflection current from the current I1B0', as shown in FIG. 8B. However, since the saturable reactor 4 operates in the saturation region, the inductance L1B1 of the first coil 6 is obtained. '
Is a very small value. The value of the current | IH-IV | is I3B1 'obtained by adding the vertical deflection current to the current I3B0', as shown in FIG. 8C, and the saturable reactor 4 operates in the saturation region. The inductance L3B1 ′ of the third coil 10 has a very small value.

When the position of the beam spot is B2 ', since the electron beam is deflected to the maximum horizontal deflection angle and downward to the maximum vertical deflection angle, the value of the current | IH + IV | Is the current I1B0 'plus the vertical deflection current as shown in FIG. 8B.
B2 ′, and the saturable reactor 4 operates in the saturation region, so that the inductance L1B2 ′ of the first coil 6 has a very small value. The value of the current | IH-IV | is I3B2 'obtained by subtracting the vertical deflection current from the current I3B0', as shown in FIG. 8C, but the saturable reactor 4 operates in the saturation region. Therefore, the inductance L3B2 ′ of the third coil 10 has a very small value. As described above, when a current for deflecting the electron beam to the maximum horizontal deflection angle is applied to the series circuit of the first and third coils 6 and 10, the series circuit of the second and fourth coils 8 and 12 is connected to the series circuit. Regardless of the magnitude and direction of the flowing current, the saturable reactor 4 operates in a saturation region.

Therefore, when the electron beam is deflected to the maximum horizontal deflection angle or an angle close to the maximum horizontal deflection angle, the inductance of the first and third coils 6 and 10 becomes independent of the vertical deflection angle. This is a very small value. As a result, the first and third coils 6, 10
Has almost no effect on the current flowing through the horizontal deflection coil, and the horizontal deflection coil has first and third coils 6,
10 operates in almost the same state as when it is not connected. Therefore, the image is not deformed even near the left end of the screen, and the state where the pincushion distortion at the left end of the screen is corrected is maintained.

As described above, in the image distortion correcting apparatus 2 for a cathode ray tube according to the present embodiment, the pincushion distortion at the intermediate portion is
The correction is performed without affecting the pincushion distortion correction at both ends of the screen. Since the image distortion correcting apparatus 2 for a cathode ray tube according to the present embodiment has a simple configuration in which four coils are wound around the core 16, it is advantageous in reducing the size and cost of the apparatus.

Although the present invention has been described based on the embodiment, it is merely an example, and the present invention can be implemented in various forms without being limited to this example. For example, in the present embodiment, the vertical deflection current supplied to the vertical deflection coil is supplied to the second and fourth coils 8 and 12, but not the vertical deflection current itself but the same as the vertical deflection current. A changing current may be supplied. Further, the characteristics of the saturable reactor 4 described above can be realized without forming the magnetic gap 14.

[0034]

As described above, the apparatus for correcting image distortion of a cathode ray tube according to the present invention, by appropriately designing the saturation characteristics of the saturable reactor, can reduce the absolute vertical deflection current flowing through the second and fourth coils. As the value increases, the inductance of one of the first and third coils becomes very small due to the saturation of the saturable reactor, while the other inductance becomes large when the saturable reactor operates in the non-saturated state. Can be configured. Therefore, at this time, the sum of the inductances of the first and third coils increases as the absolute value of the vertical deflection current increases. Since the first and third coils are connected in series with the horizontal deflection coil, when the absolute value of the vertical deflection current increases,
That is, when the vertical deflection angle increases, the horizontal deflection angle of the electron beam decreases, and as a result, the pincushion distortion in the intermediate portion is corrected.

Also, by appropriately designing the saturation characteristics of the saturable reactor, the electron beam can be adjusted to the maximum horizontal deflection angle,
Alternatively, when it is deflected to an angle close to the maximum horizontal deflection angle, the horizontal deflection current flowing in the first and third coils at that time causes the magnitude and direction of the vertical deflection current flowing in the second and fourth coils to change. Regardless, the saturable reactor can be operated in saturation. Therefore, at this time, the sum of the inductances of the first and third coils is very small, and the horizontal deflection coil operates in almost the same state as when the saturable reactor is not connected. The state where the cushion distortion is corrected is maintained. That is, the pincushion distortion in the middle portion is corrected while the shape of the left and right ends of the screen remains unchanged. The image distortion correcting apparatus for a cathode ray tube according to the present invention has a simple configuration in which four coils are wound around a core, so that the apparatus can be reduced in size and cost.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing an example of an image distortion correcting device for a cathode ray tube according to the present invention.

FIG. 2 is a circuit diagram around a deflection coil including the image distortion correcting device of the cathode ray tube of FIG.

FIG. 3 is a graph showing a change in inductance of a first coil.

FIG. 4 is a graph showing a change in inductance of a third coil.

FIG. 5A is an explanatory diagram showing a position of an electron beam spot on a screen of a cathode ray tube, FIG. 5B is a graph showing an inductance of a first coil, and FIG. 5C is a diagram showing an inductance of a third coil. It is a graph.

6A is an explanatory diagram illustrating another position of an electron beam spot on a screen of a cathode ray tube, FIG. 6B is a graph illustrating inductance of a first coil, and FIG. 6C is an inductance of a third coil. It is a graph showing.

FIG. 7A is an explanatory diagram showing still another position of an electron beam spot on a screen of a cathode ray tube, and FIG.
A graph showing the inductance of the coil of FIG.
6 is a graph showing the inductance of the coil of FIG.

8A is an explanatory diagram illustrating another position of an electron beam spot on a screen of a cathode ray tube, FIG. 8B is a graph illustrating inductance of a first coil, and FIG. 8C is an inductance of a third coil. It is a graph showing.

FIG. 9 is an explanatory diagram showing pincushion distortion in an intermediate portion.

[Explanation of symbols]

2 ... Image distortion correction device, 4 ... Saturable reactor, 6 ...
1st coil, 8 2nd coil, 10 3rd coil, 12 4th coil, 14 ... magnetic gap, 16 ... core, 18 ... horizontal deflection coil, 20 ... …
Horizontal deflection coils, 22 terminals, 24 terminals, 26
... condenser, 102 ... screen, 104 ... center line, 1
06 ... end, 108 ... end, 110 ... curve, 11
2. Curves.

Claims (6)

[Claims] An apparatus for correcting image distortion in a cathode ray tube displaying an image by deflecting and scanning an electron beam by a horizontal deflection coil and a vertical deflection coil, comprising a pair of first and second coils and a pair And a saturable reactor formed by winding a third and a fourth coil around a core, connecting the first and third coils, and the second and fourth coils, respectively, in series. The series circuit of the first and third coils is connected in series with the horizontal deflection coil, and the series circuit of the second and fourth coils has the same configuration as the vertical deflection current supplied to the vertical deflection coil or the vertical deflection current. When the first and second coils generate magnetic fields in the same direction, the third and fourth coils generate magnetic fields in opposite directions. Each coil in sex is connected, the image distortion correction apparatus of a cathode ray tube, characterized in that. 2. The image distortion correcting apparatus according to claim 1, wherein the first and third coils have the same number of turns, and the second and fourth coils have the same number of turns. 3. No current is passed through the second and fourth coils, while the series circuit of the first and third coils deflects the electron beam to approximately half the maximum horizontal deflection angle. 2. The apparatus according to claim 1, wherein the saturable reactor is substantially saturated when a current is applied. 4. A magnitude of a current flowing in the series circuit of the second and fourth coils when a current for deflecting an electron beam to a maximum horizontal deflection angle is passed through the series circuit of the first and third coils. The apparatus according to claim 1, wherein the saturable reactor operates in a saturation region regardless of the direction and the direction. 5. The image distortion correcting apparatus according to claim 1, wherein a magnetic gap is formed in the core. 6. An apparatus according to claim 1, wherein a capacitor for correcting pincushion distortion is connected in series to said horizontal deflection coil.