JPH0785585B2 - Geomagnetic correction device for color cathode ray tubes - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a geomagnetism correction device for improving the purity (color saturation) for a color CRT due to the influence of geomagnetism.

(Prior Art) It has been generally known that, in a super-large color cathode ray tube, the geomagnetism of a horizontal magnetic field is canceled to correct the geomagnetism. However, although effective for some purposes, it does not provide a complete solution for geomagnetic correction.

A conventional geomagnetism correction device of this type is, for example, as shown in FIG. 6, wound with a coil 1 in the peripheral direction of the cathode ray tube 3 and generates a horizontal magnetic field in the tube axis direction of the cathode ray tube 3, thereby causing a geomagnetic effect. It corrects the worse landing.

More specifically, in FIG. 6A, an arrow a indicates a beam moving direction (direction in which landing is deteriorated by geomagnetism) when the television receiver 2 is installed in the south direction.

As shown in FIG. 6 (b), when a current is passed through the coil 1, the geomagnetism (natural magnetic field) is canceled by the magnetic field generated by the coil 1, the magnetic field of the horizontal component disappears, and the beam does not move. Also, the television receiver 2
When it is installed in the north direction, all polarities (vectors) are opposite to those shown in FIG. 6, and this can be corrected by changing the direction of the current flowing through the coil 1.

(Problems to be Solved by the Invention) However, in the above-described conventional method, correction can be performed only when the television receiver is installed in the north-south direction, and the landing shift amount in the east-west direction described on a separate page. There was a problem that correction of was impossible. Moreover,
Since the landing shift is larger at the corners of the cathode ray tube and the vector direction is different at each corner, the conventional geomagnetic correction device that uniformly corrects the surface of the cathode ray tube deteriorates the purity (color saturation) at the corners of the cathode ray tube. There was a problem that was conspicuous.

(Means for Solving the Problem) The present invention relates to a pair of magnetic field generating coils symmetrically arranged with respect to a neck portion on the back surface of a color cathode ray tube,
A geomagnetism correction device for a color cathode ray tube, comprising: a switching means for switching a current flowing through the magnetic field generation coil, wherein at least one side of the magnetic field generation coil is substantially parallel to a vertical side of the color cathode ray tube. Further, the two sides are arranged substantially on the line connecting the neck portion and the corner portion of the color CRT, and the switching means sets the direction of the current flowing through the pair of magnetic field generating coils to the color CRT. Each of them can be switched independently according to the direction of the face surface when the operation is performed.

(Operation) A geomagnetism correction device for a color cathode ray tube according to the present invention,
No matter which direction you install the television receiver, north, south, east,
Since the direction of the current flowing in each magnetic field generating coil can be switched independently, there are four types of geomagnetic fields depending on the landing shift at each corner of each color CRT when the television receiver is installed in the north, south, east, and west directions. The correction can be performed, and the optimum correction can be selected according to the installation state of the television receiver.

(Embodiment) An embodiment of the geomagnetism correction device for a color cathode ray tube according to the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows a state in which the coil A and the coil B are attached to the back surface of the color cathode-ray tube 3.

The coil A and the coil B have a substantially trapezoidal shape, and these coils A and B are installed symmetrically with respect to the neck portion of the color CRT 3. The hypotenuses of the coils A and B should be substantially parallel to the electron beam heading to the corners of the color cathode ray tube 3, that is, the color cathode ray tube 3
The coil A and B are arranged so as to be substantially on the line connecting the neck portion and the corner portion of the cathode ray tube. .

First, an outline of the geomagnetism correction device of the present invention will be described with reference to FIG. In the geomagnetic correction device of the present invention, the geomagnetic correction is performed by switching the vector of the magnetic fields of the coils A and B with respect to the landing shift that differs depending on the installation direction of the television receiver. That is, by independently switching the polarities of the currents flowing through the coils A and B in accordance with the direction of the cathode ray tube 3 by a switch, the landing shift due to the horizontal component of the geomagnetism can be achieved regardless of the direction of the cathode ray tube 3 in the north, south, east and west. It can be lost.

FIG. 3 shows a switching means in an embodiment of the geomagnetism correction device of the present invention, which is composed of a switch circuit 4 for switching the polarity of the current flowing through the coils A and B.

The coils A and B are connected in series, the switch has two circuits and four contacts, and its basic circuit is as shown in FIG. 3 (b). A single switch circuit that does not use the basic circuit of this embodiment requires four circuits and four contacts, but the switch circuit 4 of this embodiment can reduce the number of contacts to half.

FIG. 4 shows the movement of the landing depending on the direction of the horizontal magnetic field when the cathode ray tube 3 is completely demagnetized by the external degausser. This is because the electron beam is deflected by the horizontal component of the geomagnetism, and FIG. 4 (a) shows the theoretical principle of landing movement due to the horizontal component of the geomagnetism.

Here, the x-axis represents the electron beam vector in the horizontal direction of the cathode ray tube 3, the y-axis represents the vertical direction of the cathode ray tube 3, and the z-axis represents the vector of the electron beam in the tube axis direction. The left-hand rule causes electromagnetic deflection as shown in FIGS. 4 (b) and 4 (c), respectively. This changes the position of the electron beam when passing through the shadow mask, causing mislanding with respect to the phosphor. Since the principle of this problem is already known, it is omitted here. Only the movement of the electron beam will be described below.

FIG. 5 shows the principle of operation of the geomagnetic correction coils A and B in this embodiment.

The principle of landing shift due to geomagnetism is as described above with reference to FIG. 4, and the operation principle of the coils A and B will be described below. FIG. 5A shows a geomagnetic correction state when the face surface of the cathode ray tube 3 faces east.
Here, the magnetic field at the diagonal corner of the cathode ray tube 3 is corrected by canceling it by the correction magnetic field generated by the coil A and the coil B. Further, in the vertical direction of the central portion of the screen, the correction magnetic fields of different vectors are applied by the left and right coils A and B, so that there is no magnetic field. Therefore,
Landing shift as shown in FIG. 4 (e) does not occur, and just landing can be performed completely.

When the face surface of the cathode ray tube 3 faces west, as shown in FIG. 5 (b), all the magnetic field directions are opposite to those in the east direction described above, so the polarities of the currents flowing through the coils A and B are also east. It is the exact opposite of when facing.

FIGS. 5C and 5D show geomagnetic correction states when the face surface of the cathode ray tube 3 faces south and north, respectively. 4 (a), (b), and (c) show the landing movement due to the magnetic field of the horizontal component, but the landing shift direction is different between the east-west direction and the north-south direction. That is, the geomagnetic correction when the face surface of the cathode ray tube 3 faces the north-south direction can be performed by reversing the polarities of one coil in the correction state when the face surface faces the east-west direction. The polarities of the currents flowing through the coils A and B are opposite when the face surface of the cathode ray tube 3 faces south and north.

Further, the arrow b direction in FIG. 5 (c) shows an example in which the horizontal component (z-axis direction) electron beam is deflected by the present invention. In the drawing, the vector component is in the horizontal direction only. The electron beam is actually a cathode ray tube 3
Although it moves to the diagonal line of, the stripe type phosphor is generally used, so it is illustrated here as an illustration of only the horizontal component that affects the landing.

As described above, according to the present invention, when the television receiver is installed in any of the north, south, east, and west directions, the coils A, B
It is possible to eliminate the landing shift (color shift) by independently switching the polarity of the current that flows in, and the effect of geomagnetic correction for a large CRT with a small degree of latitude in geomagnetism can be expected.

As a result of the circuit experiment in the present embodiment, in the large-sized 33-inch class color cathode-ray tube 3, both coils A and B are 3
A corrected magnetic force of about 4 AT was sufficient.

Further, when the face surface of the cathode ray tube 3 is oriented in the east-west direction, the horizontal magnetic field component generally has a magnetic field distribution as shown in FIG. 4 (d) at the corner portion of the magnetic shield plate provided inside the cathode ray tube 3. Become. The vertical component generated at this corner portion deflects the horizontal component of the electron beam to cause landing movement, as shown in FIGS. 4 (e), (f), and (g). In this way, the movement of the electron beam is deflected by the geomagnetism, and the geomagnetism is corrected by analyzing these movements.

(Effect of the Invention) Since the geomagnetism correction device for a color cathode ray tube according to the present invention has the above-described configuration, the direction of the current flowing through each magnetic field generating coil is independently switched to set the installation direction of the television receiver. Can perform four types of correction control according to the landing shift at each corner of each color cathode-ray tube in the north, south, east, and west, and the influence of geomagnetism on the color cathode-ray tube can be minimized, especially the influence of geomagnetism is large. It is extremely useful in practice for very large cathode ray tubes. Further, technically, the design of the cathode ray tube can be facilitated, and economically, the automatic degaussing circuit can be simplified, and the outer shield can be dispensed with.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention, FIGS. 1 (a) and 1 (b) are a rear view and a side view showing an arrangement state of a geomagnetic correction coil, and FIG. 2 is a cathode ray tube of the correction coil. FIG. 3 is a circuit diagram showing a switch circuit, FIG. 4 (a) to FIG. 4 (g) are explanatory diagrams showing movement of an electron beam due to geomagnetism, and FIG. 5 (a).
6A to 6D are explanatory diagrams showing the principle of operation of geomagnetic correction, and FIGS. 6A and 6B are explanatory diagrams showing a conventional example.

Claims (1)

[Claims] 1. A geomagnetism correction for a color cathode ray tube having a pair of magnetic field generating coils symmetrically arranged with respect to a back neck portion of the color cathode ray tube, and switching means for switching a current flowing through the magnetic field generating coil. In the device, at least one side of the magnetic field generating coil is substantially parallel to a vertical side of the color CRT, and two sides thereof are substantially on a line connecting a neck portion and a corner portion of the color CRT. The switching means can independently switch the direction of the current flowing through the pair of magnetic field generating coils according to the direction of the face surface when the color cathode ray tube is installed. A geomagnetism correction device for a color cathode ray tube, which is characterized in that