JPS59119653A - Beam spot correcting device - Google Patents

Abstract

PURPOSE:To correct distortion of the shape of a spot, by amplitude-modulating a parabolic-wave signal of the horizontal period with a parabolic-wave signal of the vertical period and applying the modulated current to the coil of the correcting yoke provided at the neck portion of the picture tube. CONSTITUTION:A signal from the transformer 1 provided in the horizontal deflecting circuit of an inline type 3-beam color picture tube is changed by the integrating circuit 3-5 into a sawtooth-wave voltage, which then is applied to the transistor 6 for making a switching, whereby a parabolic signal with the horizontal period is provided at the point C. Meanwhile, a parabolic signal of the vertical period is applied to the base of the transistor 21. And in the modulating device 17, the signal with the horizontal period is amplitude-modulated with the signal of the vertical period, and the thus obtained correcting current is applied to the coil of the quadrupole correcting yoke for dynamic convergence correction provided at the neck portion. Hence a distortion of the shape of the spot from any cause, for example from difference in the horizontal and vertical focusing distances, can be certainly corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a beam spot correction device for a picture tube (cathode ray tube).

BACKGROUND ART AND PROBLEMS With the recent spread of microcomputers, there is an increasing demand for picture tubes that can display a large number of characters and have good beam focusing.

In particular, in an in-line 3-beam color picture tube such as Trinitron (registered trademark), a quadrupole correction yoke is provided from the outside of the neck part at the convergence electrode part for horizontal static convergence, so that red, a, Because the blue beam is dynamically converged in the horizontal direction, the degree of convergence of the beam inevitably decreases, that is, the spot shape is distorted.

Therefore, conventionally, the decrease in the degree of beam convergence has been corrected as follows. A conventional beam spot correction device for an in-line three-beam color picture tube will be described below with reference to FIG.

In Fig. 1, (1) is a horizontal quadrangle installed in a horizontal deflection circuit, and the high potential side (point A) of its secondary winding (2) is connected as shown in Fig. 2 A. A pulse voltage of negative polarity with a horizontal period is generated. The high potential side of the secondary winding (2) is connected to an integrating circuit in which a coil (3) and a series circuit of a capacitor (4) and a resistor (5) are connected in an inverted configuration. On the output side (point B) of
The horizontal sawtooth voltage shown in is generated. This sawtooth voltage is supplied to the base of the transistor (6) through an inverted circuit of a capacitor and a resistor, and the transistor (6) is switched by the sawtooth voltage.

The emitter of the transistor (6) is grounded, and its collector is connected to the power supply terminal 10B through a choke coil (7) and a variable resistor (8) in order, and a damper diode (9) is connected between the collector and ground. and a parallel circuit of capacitor members are connected. The variable resistor (8) has one end of its stator open and its slider connected to the power supply terminal 10B, and the power supply voltage supplied to the circuit is varied by the variable resistor (8). Ru.

At the collector (6 points) of this transistor (6), when the transistor (6) is off, a wide pulse voltage (pulse width of about 30 μδ) with a horizontal period shown in FIG. 2C is generated.

Further, αυ indicates a correction coil wound around a yoke for beam spot correction. The correction yoke is a quadrupole yoke,
Two correction coils aυ are provided symmetrically in a U-shape, and a correction coil aυ is wound around each of them, and the correction coil αυ is a combination of the correction coils of each yoke. This correction yoke is provided at a portion of the neck portion that corresponds to the focusing electrode. A first series circuit is constituted by a correction coil (1υ) and a first diode (121), and a coil (13) with an inductance value approximately equal to that of the correction coil αυ and a first diode (121
A second series circuit is constructed by the second diode α force having a polarity opposite to that of the second diode, and these first and second series circuits are connected in parallel, and one end of this parallel circuit is connected to a choke coil (7
) and the variable resistor (8), and the other end is connected to the collector of the transistor (6) via the capacitor (151).The correction coil αυ or the coil (
The inductance value of 131 is sufficiently small compared to that of the choke coil (7), and this correction coil a0
Alternatively, the series resonance frequency determined by the coil α wrinkle and the capacitor (151) is selected to be approximately equal to the water frequency.

Furthermore, between the connection point of the correction coil (11) and the diode (121) and the connection point of the coil α4 and the diode (t4),
With respect to the back electromotive force generated in the correction coil αυ or the coil (13) when these diodes are cut off,
Capacitor (16) to protect these diodes
is inserted. In this case, the diode 0 and (14)
Capacitors may be connected in parallel between the anode and cathode of each, but since one diode is always on, the diode can be protected by simply connecting one capacitor θe as shown. .

Further, since the capacitance value of this capacitor Qe is sufficiently smaller than that of the capacitor α9, it hardly affects the resonance operation between the coil Qll or the coil ←■ and the capacitor Q51.

In the correction device shown in FIG. 1 described above, by supplying the pulse voltage with the horizontal period shown in FIG. αυ and the coil (13). Therefore, the diodes a and I are turned on alternately, and a sine wave current with a horizontal frequency flows as a whole. As shown, a current flows with a horizontal period of approximately parabolic (or approximately sinusoidal) shape, which reaches a negative maximum approximately at the center of the horizontal scanning period and reaches zero on both sides thereof. The other correction coil Ql) has a zero value approximately at the center of the horizontal scanning period and a positive maximum on both sides, as shown in FIG. 2 E, when the direction indicated by E in FIG. 1 is positive. A substantially parabolic (or substantially sinusoidal) horizontal period correction current flows.

In this case, actually, due to the capacitor αe, the correction current does not become completely zero at approximately the center of the horizontal scanning period, but becomes slightly negative, but this is almost negligible. Therefore, the amount of correction at the center of the screen can be set to zero, and the amount of correction can be increased toward the periphery of the screen. The waveform in FIG. 2E is the waveform of the correction current flowing through the correction coil of the quadrupole correction yoke for dynamic convergence correction, which is provided corresponding to the convergence electrode part for static convergence correction. The shape is symmetrical with respect to the time axis.

Note that FIG. 2F shows the collector current waveform of the transistor (6), and the damper current due to the damper diode (9) is shown by a broken line in the same figure.

By the way, in the above-mentioned beam spot correction device shown in Fig. 1, it is difficult to improve the degree of beam convergence, that is, correct distortion of the beam spot shape, due to differences in the horizontal and vertical focal lengths of each arm and child beam. It wasn't enough.

OBJECTS OF THE INVENTION In view of the above points, the present invention seeks to propose a beam spot correction device capable of sufficiently correcting distortion in the shape of a beam spot, regardless of the cause of the distortion.

Summary of the Invention A beam spot correction device according to the present invention includes a correction yoke provided at a neck portion and amplitude modulation of a horizontal period parabola wave signal (or sine wave signal) with a vertical period parabola wave signal (or sine wave signal). A correction current based on a modulated signal from the modulator is made to flow through a correction coil of a correction yoke.

According to the present invention, it is possible to obtain a beam spot correction device that can sufficiently correct distortion in the beam spot size, regardless of the cause of the distortion.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to FIG. 3. In FIG. 3, parts corresponding to those in FIG. .

The same shows a modulator, in which a horizontally periodic parabolic wave signal (or sine wave signal) is amplitude-modulated by a vertically periodic parabolic wave signal (or sine wave signal), and this modulator (amplitude modulated signal from Iη) is used. A correction current based on is made to flow through the correction coil αυ of the correction yoke.

Next, the configuration of an example of this modulator surface will be explained.

The power supply element B is connected to the collector of the transistor (6), ie, point C, through the collector and emitter of the variable impedance transistor α, and then through the coil (7). Incidentally, the emitter of the transistor H is grounded through a capacitor wire for removing ripples. Transistor Ql
A bias resistor wire is connected between the collector and base of the transistor No. 19. The base of the transistor α is connected to the collector of the control transistor 0υ, and the transistor 0I)
The emitter of E3. is grounded through a resistor (24).
(Incorporated) is a base bias resistor for transistor Qυ. A parabolic wave signal (or sine wave signal) with a vertical period V is supplied from the input terminal (c) to the base of the transistor Qυ through a series circuit of a capacitor C26) and a resistor (271).

Incidentally, the diodes αL (14) are each connected in opposite polarity to that in FIG. The other circuit configurations are the same as in FIG. 1.

Next, referring to FIG. 4, the structure of the color picture tube used in the embodiment of FIG. 3 will be explained. KR* KG sKB is a cathode, and after the red, blue, and green electron beams R, G, and B from these cathodes KR, KG, and KB intersect at the focusing electrode G4, a convergence electrode (2gl (electrostatic deflection plate) (consisting of P, P; Q, Q) and intersect at the slit part of the aperture grill AG, and a fluorescent screen SC consisting of striped phosphors
Each color value of the light body will impact the stripe.

(to) is 41 arranged corresponding to the part of the focusing electrode G4.
This is a polar correction yoke, which consists of a pair of U-shaped yokes (30a) and (30b) as shown in Figure 5.
0a).

(30b) is the beam R2 on the outside of the neck part NC.
The correction coil aυ shown in FIG.
is wrapped.

Oυ is a 41-pole correction yoke for dynamic convergence correction placed on the outside of the neck corresponding to the convergence electrode (29), and is similar to the correction yoke (g) shown in Fig. 5. It consists of a pair of U-shaped yokes, which are perpendicular to the plane containing the beams R, G, and B, and arranged symmetrically on both sides of the plane containing the central beam G, and around which a correction coil is wound.

DY is a horizontal and vertical deflection yoke, which is arranged near the convergence electrode (and on the aperture grille AG side).

Next, the correction current applied to the correction coil αυ of the correction device shown in FIG. 3 will be explained. FIG. 6 shows the waveform of the carrier wave current of the correction current (modulated current) flowing through the correction coil Ql), that is, the horizontal period parabolic wave current (or sine wave current), which reaches its maximum value ( A parabolic wave (or sine wave) that is positive) and minimum (slightly negative) on both sides.
It is. The waveform in FIG. 6 has a shape that is substantially symmetrical with respect to the time axis with the waveform of the current flowing through the correction coil of the convergence correction yoke Oυ (see FIG. 7).

Then, the amplitude-modulated current obtained by amplitude-modulating the parabolic wave current (or sine wave current) with the horizontal period shown in Fig. 6 with the parabolic wave current (or sine wave current) with the positive vertical period (see Fig. 8). , where the direction E in FIG. 3 is positive) is applied to the correction coil α1).

Also, since the waveform of the correction current flowing through the correction coil of the convergence correction yoke Oυ is a parabolic wave (or sine wave) shown in FIGS. 9 and 10, the correction current applied to the correction coil αυ of the correction yoke (to) The waveform of the current is a parabolic wave (or sine wave) as shown in FIGS. 11 and 12, respectively. As shown in FIG. 12, the correction current flowing through the correction coil αυ (if negative, the connection polarity of the diodes α2, 04 in FIG. 3) must be reversed from that shown in FIG.

In Figure 5, the U-shaped yoke (3) of the correction yoke (to)
Magnetic flux FL in mutually opposite directions from 0a) and (30b)
a.

Due to FLb, the electron beam EB (R, G, B), which is perpendicular to the plane of the paper and directed from the front surface to the back surface, has upper and lower beams as shown in the figure.
Forces f1 to f4 shown by arrows act on the left and right sides, and the beam EB is crushed in the vertical direction and deformed as if pulled in the left and right directions, thereby correcting the distortion of the beam spot. According to experiments, by providing a correction yoke,
Compared to the case where no beam is provided, the reduction rate of the spot size of each beam R, G, and H on the phosphor screen SC is highest near the vertical center line of the screen SC, and decreases as it moves away from there to the left and right. Narata. The spot size of the beam EB near the corners of the screen SC and the left and right ends of the horizontal center line was hardly reduced.

Incidentally, as a modification of Fig. 3, the diode α, α,
The connection point to the emitter of the transistor <181 may be connected to the collector of the transistor (6) via the capacitor a, and the connection point of the coils 0υ and α stage to the capacitor a may be grounded. In this case, the diodes a2) and αa may be connected in parallel in opposite directions via the capacitor αe (the polarity of the connection is arbitrary).

In addition, in the case of a color picture tube, such as the Trinitron, where there is a part where the three color electron beams R2G and B intersect between the cathode and the deflection center, the correction yoke (to) is placed near the intersection point. In the case of a color picture tube that does not have such an intersection point between the cathode and the center of deflection, it is desirable to provide a pair of correction yokes (see FIG. 5) in the part where the spot size of each electron beam can be corrected independently. 30a), (3
It is sufficient to provide three sets of 0b) and perform correction for each beam.

Further, the present invention can also be applied to a monochrome picture tube.

Effects of the Invention According to the present invention described above, it is possible to obtain a beam spot correction device that can reliably correct distortion in the beam spot size, regardless of the cause of the distortion.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional correction device, FIG. 2 is a waveform diagram for explaining its operation, and FIG. 3 is a circuit a3 of an embodiment of the beam spot correction device according to the present invention.
FIG. 4 is a layout diagram showing the arrangement of each part of the cathode ray tube, FIG. 5 is a layout diagram showing the correction yoke, and FIGS. 6 to 12 are waveform diagrams. ←υ is a correction coil, a7) is a modulator, and (to) is a correction yoke. (14) Two - 4th prisoner Figure 5n Figure 6 Figure 7 Figure 8 Figure 9 Figure 11 and Figure 10 Figure 12

Claims (1)

[Claims] A correction yoke provided at the neck portion, a modulator that modulates the amplitude of a horizontal period parabolic wave signal (or sine wave signal) with a vertical period parabolic wave signal (or sine wave signal), and a modulated signal from the modulator. A beam spot correction device characterized in that a correction current based on a signal is caused to flow through a correction coil of the correction yoke.