JPS6232776A - Correction circuit for raster distortion - Google Patents

Abstract

PURPOSE:To correct non-linear raster distortion by performing the amplitude modulation of a horizontal pulse with vertical synchronization so that the minimum amplitude is obtained when the center part of a picture plane is scanned and the maximum amplitude when its upper and lower parts are scanned. CONSTITUTION:On the vertical winding 10b of a modulation circuit, saw tooth waveform deflection current is flowed and inductance in the horizontal winding 10a of the modulation circuit, by a saturable reactor characteristic, represents the minimum value in the maximum current flow at the start and the end of a scanning of vertical period and the maximum value at the intermediate of the scanning. Therefore, voltage at the both ends of the transformer horizontal winding 5a of a raster distortion transformer 5 generates a pulse modulated with the vertical period in parabolic shape. Thereby, generated voltage at a resonance circuit including the vertical winding 5b of the transformer 5 becomes an envelope of U-character shape, and the result is that the correction of the non-linear raster distortion in which distortion correction in a large volume is performed at the start and the end of the vertical scanning and correction effect is reduced at the intermediate part can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a raster distortion correction circuit that corrects raster distortion of horizontal lines at the top and bottom of a screen that occurs in a display device such as a television receiver that uses a cathode ray tube.

[Conventional technology]

The raster on the phosphor screen, which is the image display section of the cathode ray tube, has an inverted W-shaped distortion as shown in the example shown in FIG. 3 due to the curvature of its face bullet and the magnetic field distribution of the raster forming means, that is, the electromagnetic deflection yoke. The raster distortion shown in the example shown in FIG. 3 is generally corrected by a raster distortion correction circuit surrounded by a broken line in FIG. 4, as shown in Japanese Patent Publication No. 58-57014, for example.

In FIG. 4, la and lb are vertical output transistors,
2 is a coupling capacitor, 3 is a vertical 0-direction coil, 4
is a vertical feedback resistor, 5 is a raster distortion correction transformer, 5a is a transformer horizontal winding of the raster distortion correction transformer, 5b is a transformer vertical winding of the raster distortion correction transformer, 6 is a phase adjustment contor, 7 is a resonant capacitor, 8 and 9 is a capacitor and a resistor forming a bypass circuit for the correction current. Since the raster distortion shown in FIG. 3 has high frequency distortion twice the horizontal deflection frequency fH, the transformer vertical winding 5b of the raster distortion correction transformer 5, the phase adjustment coil 6 and the resonant capacitor 7
to form a resonant circuit tuned to approximately twice the horizontal frequency, and the raster correction current generated in this resonant circuit is transferred to capacitor 8. The correction is performed by flowing the signal to the vertical deflection coil 3 via the resistor 9. The waveform of the raster correction current is superimposed on the vertical deflection current, and if the waveform of the vertical deflection current is observed at a vertical period, it will be as shown in FIG. 5(a). The waveform of the raster correction current in the horizontal period is ideally shown in Figure 5 (b
Therefore, the second-order distortion shown in FIG. 3 is corrected. In addition, if we observe the waveform of the correction current in a vertical cycle, as shown in Figure 5 (C1), the amplitude is almost at its maximum at the beginning and end of the scan of the vertical cycle, and the amplitude is almost at its maximum at the center of the vertical cycle (corresponding to the center of the screen). ), the correction becomes 0, and the envelope from the maximum to 0 has an almost straight line or a slightly convex shape as shown by the broken line in FIG. 5(C), although it depends on the characteristics of the raster distortion correction transformer, etc.

Note that the transformer horizontal winding 5a of the raster distortion correction transformer 5
A horizontal pulse is applied from a Franbank transformer (not shown) or the like, and horizontal energy is supplied to the resonant circuit as a horizontal timing pulse.

[Problem that the invention seeks to solve]

Recently, the faces of cathode ray tubes have become flatter and larger, and fluorescence has become more noticeable. In this case, the curvature of the face surface is complicated in order to satisfy both the realization of a flat feeling and the doming resistance, because if you try to flatten it by simply increasing the radius R of the spherical surface, problems such as doming of the shadow mask will occur. It is often selected for its aspherical structure. FIG. 6 is an example of a contour diagram of a face plate having an aspherical structure. When a cathode ray tube with such a face surface is raster-scanned with a deflection cork, as shown by the broken line in Figure 6, there is a large second-order distortion 2W-shaped distortion at the bottom edge of the screen, but as it approaches the center a little. Non-linear thruster strain is exhibited in the vertical period in which the second-order strain tendency is rapidly reduced. Therefore, if the correction current of the conventional type raster distortion correction circuit is used to properly correct the distortion in the upper and lower parts of the screen, there is a drawback that the middle part of the screen is overcorrected and the distortion increases.

The present invention has been made to solve the above-mentioned problems, and provides means for correcting nonlinear raster distortion in the vertical period caused by an aspherical structure face plate, etc., using a simple structure.

[Means for solving problems]

Therefore, the raster distortion correction circuit according to the present invention modulates the amplitude of the horizontal timing pulse with vertical synchronization so that the amplitude is minimum when scanning the center of the screen and maximum when scanning the top and bottom of the screen. The present invention is characterized in that a vertical modulation circuit is provided for applying this amplitude-modulated horizontal timing pulse to the horizontal winding of the raster distortion correction transformer.

[Effect]

The vertical modulation circuit amplitude modulates the horizontal timing pulse with vertical synchronization, and the amplitude is minimum when scanning the center of the screen.
The amplitude is maximized when scanning the top and bottom of the screen.

In this way, vertically synchronized and amplitude modulated horizontal timing pulses are applied to the horizontal windings of the raster correction transformer.

As a result, the current generated in the resonant circuit consisting of the coil and capacitor including the vertical winding of the raster distortion correction transformer is minimum when scanning the center of the screen, and maximum when scanning the top and bottom of the screen. Therefore, raster distortion is minimized at the center of the screen and maximum at the top and bottom of the screen, and is efficiently corrected.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

Note that the same components as in the prior art are given the same numbers and their explanations are omitted.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In FIG. 1, 10 is a vertical modulation circuit. This vertical modulation circuit IO is of a saturable reactor type, and t
Oa is a modulation circuit horizontal winding, 10b is a modulation circuit vertical winding,
IOC is Saturapur Core. In this saturable reactor method, since a sawtooth vertical deflection current flows through the vertical winding 10b of the modulation circuit, the inductance of the horizontal winding 10a of the modulation circuit changes at the beginning and end of scanning of the vertical period due to the well-known characteristics of the saturable reactor. The inductance value is the minimum when the current is at maximum, and the inductance is the maximum when the vertical deflection current is in the middle of scanning, that is, when the vertical deflection current is O. Therefore, the voltage across the transformer horizontal winding 5a of the raster distortion correction transformer 5 becomes a pulse modulated with a vertical period in a parabolic manner.

When the voltage applied to the transformer horizontal winding 5a of the Rician distortion correction transformer 5 is modulated concavely in a parabolic manner with a vertical period as described above, the generated voltage of the resonant circuit including the transformer vertical winding 5b of the raster distortion correction transformer 5 Figure 5 (C
), but rather a U-shaped envelope as shown in FIG. As a result, such a resonant voltage performs a large distortion correction at the beginning (or end) of the vertical scan, but as it approaches the middle, the correction effect decreases rapidly, and the non-linear raster distortion shown in Figure 2 becomes difficult to achieve. It will be corrected.

In the embodiment shown in FIG. 1, a saturable reactor is used as the vertical modulation circuit. For the vertical bias in this case, a vertical deflection current was passed through the modulation circuit vertical winding tab.
It is also possible to install an open magnetic path type satura pull core close to the core (not shown) and use the leakage flux of the deflection yoke as a magnetic bias.

Furthermore, it is also possible to realize a vertical modulation circuit using an electronic circuit combining ordinary semiconductor elements without using a saturable reactor.

Furthermore, the transformer horizontal winding 5a of the raster distortion correction transformer 5
The voltage applied before vertical modulation has been described with reference to the flybank pulse, but the present invention is also applicable to a method in which the repetition frequency is the horizontal deflection frequency or an n-th harmonic is applied.

[Effects of the Invention] As explained above, the raster distortion correction circuit according to the present invention minimizes the amplitude when scanning the center of the screen, and maximizes the amplitude when scanning the top and bottom of the screen. A vertical modulation circuit is provided that amplitude-modulates the horizontal timing pulse with vertical synchronization and applies the amplitude-modulated horizontal timing pulse to the transformer horizontal winding of the raster distortion correction transformer. It is possible to easily and accurately correct the complex vertical raster distortion that occurs in cathode ray tubes.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing non-linear raster distortion, Fig. 3 is a waveform diagram showing the raster distortion waveform on the screen, and Fig. 4 is a diagram showing the conventional raster distortion. The circuit diagram of the distortion correction circuit, Fig. 5+8) to Fig. 5(C) are waveform diagrams showing the waveforms of the vertical deflection current and raster correction current, and Fig. 6 shows the isolinear and raster distortion of an aspherically symmetrical screen. FIG. 5... Raster distortion correction transformer, 5a... Transformer horizontal winding, 5b... Transformer east series winding, 10... Vertical modulation circuit, 10a... Modulation circuit horizontal winding, IOb...
- Modulation circuit vertical winding. Agent Masuo Oiwa (2 idiots) Deception C0 滌し Showa Year Month Date 20 Name of the invention Raster distortion correction circuit 3, Person making the amendment 5, Symmetrical claims of the amendment, Detailed description of the invention, Drawings A brief description and drawing column. 6. Contents of the amendment + 11 The scope of the claims will be amended as shown in the attached sheet. (2) In the third line of page 4 of the specification, the phrase "Fran 8tsuku" is amended to read "Flybank." (3) In the same book, page 4, line 9, ``fluorescence'' is replaced with ``tendency.''
and correct it. (4) In the first line of page 5 of the same book, the word "thruster" has been corrected to "raster." (5) In the fourth line of page 5 of the same book, the phrase ``and the screen'' has been corrected to ``and the screen as shown in Figure 2.'' (6) The same book, page 5, line 20 to page 6, line 1, 6
In the fourth line of the page, "vertical synchronization" is corrected to "vertical period." (7) On page 6 of the same book, lines 9 to 13, the phrase "The generated current is corrected to the screen... Since it is modulated with a vertical period, the envelope line becomes U-shaped as shown in FIG. 1, and the amount of correction decreases sharply as it goes inward from the top and bottom edges of the screen. Therefore, the distortion shown in FIG. 6 is ideally corrected. (8) On page 7, line 14 of the same book, replace the phrase “Rician distortion” with “
Correct "raster distortion". (9) In the third line of page 8 of the same book, “Figure 2” was replaced with “Figure 6.”
Correct it to "Fig." Ql Same book, page 9, line 14, [The figure shows nonlinear raster distortion] is corrected to ``The figure shows the distortion when the raster distortion in Figure 6 is corrected using the conventional method.'' . On page 9, line 18 of the RanRoku, the phrase ``aspherical symmetry'' is corrected to ``aspherical structure.'' +121) The drawings and Figure 6 will be corrected as shown in the attached sheet. 2. Claims: By applying a horizontal timing pulse to the transformer horizontal winding of the raster distortion correction transformer, a resonant circuit consisting of a coil including the transformer vertical winding of the raster distortion correction transformer and a coil capacitor is driven. In the raster distortion correction circuit, which corrects the raster distortion on the screen by passing the correction current generated in this resonant circuit through the vertical deflection coil, the amplitude is minimum when scanning the center of the screen, and A vertical modulation circuit is provided that amplitude-modulates the horizontal timing pulse in a vertical phase so that the amplitude is maximum during scanning, and applies this amplitude-modulated horizontal timing pulse to the transformer horizontal winding of the raster distortion correction transformer. A raster distortion correction circuit characterized by:

Claims (1)

[Claims] By applying a horizontal timing pulse to the transformer horizontal winding of the raster distortion correction transformer, a resonant circuit consisting of a coil and a capacitor including the transformer vertical winding of the raster distortion correction transformer is driven. In a raster distortion correction circuit that corrects raster distortion on a screen by flowing a correction current through a vertical deflection coil, the amplitude is minimum when scanning the center of the screen, and maximum when scanning the top and bottom of the screen. A raster distortion correction device comprising a vertical modulation circuit that amplitude-modulates the horizontal timing pulse with vertical synchronization so that the horizontal timing pulse is amplitude-modulated and applies the amplitude-modulated horizontal timing pulse to the transformer horizontal winding of the raster distortion correction transformer. circuit.