JPS5837179Y2 - Projection distortion correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a projection distortion correction device used in a multi-tube color projector.

Traditionally, three cathode ray tubes are used to reproduce monochromatic images of R (red), G (green), and B (blue), and the images reproduced by these cathode ray tubes are projected overlappingly onto a single screen through a lens. A multi-tube color projector that obtains color images is known.

Figures 1 and 2 show an example of the arrangement of cathode ray tubes in such a color projector, where 1 is a screen, 2G is a cathode ray tube for reproducing 0 images, 2B is a cathode ray tube for reproducing 3 images, and 2R is a cathode ray tube for reproducing 3 images. A cathode ray tube for image reproduction, 3 and 4 are lenses, and 5 is a half mirror.

Note that the screen 1 shown by the dotted line is a screen with a curvature.

The cathode ray tubes 2G and 2B are arranged so that their respective central axes are inclined at an angle θ in the horizontal direction and an angle α in the vertical direction with respect to the central axis of the screen 1.
is located below.

The projection light from the cathode ray tube 2G passes through the lens 3 and is projected onto the screen 1, and the projection light from the cathode ray tube 2B passes through the half mirror 5 and the lens 4 and is projected onto the screen 1. After the projected light is reflected by the half mirror 5, it passes through the lens 4 and enters the sufnoon 1.
It is threatened to be projected onto the world.

The color image projected onto the screen 1 by the color projector configured as described above has the tilt angle θ.
, α, etc., various distortions occur.

Figure 3 shows normal loss hatch playback with cathode ray tube 2G.
This shows the screen pattern that will be projected on the flat screen 1 shown by the solid line in Figure 1 when this is projected onto the flat screen 1, which will have a roughly trapezoidal shape and will be horizontally centered around the center of the left half of the screen. There are distortions that are tilted in opposite directions.

Note that the distortion shown by the dotted line occurs when the screen 1 having the curvature shown by the dotted line in FIG. 1 is used.

In addition, if the cathode ray tubes 2B and 2R reproduce the normal loss hatch and project it onto the screen 1, the y
Axis-symmetrical distortion occurs.

In order to match these two symmetrical patterns on the screen 1, conventional projectors of this type perform H, KEYS correction, H, P as shown in FIG. 4A, B, C, and D.
Four correction circuits are provided for performing corrections such as IN correction, H, CRO3S correction, and H, BOW correction.

If these four correction circuits are used to adjust the above two patterns so that they match, and the trapezoidal pattern in Fig. 3 becomes a rectangular pattern by the above H, CRO3S correction, the final pattern as shown in Fig. 5 is obtained. is obtained.

In FIG. 5, the patterns indicated by solid lines are cathode ray tube 2B,
The pattern projected by 2R and the pattern indicated by the dotted line is projected by cathode ray tube 2G.

As is clear from FIG. 5, the pattern produced by the cathode ray tube 2G and the pattern produced by the cathode ray tubes 2B and 2R have distortions that tilt in opposite directions, and the distortion in the center of the screen is particularly significant. It has become.

Such distortion could not be removed even by using the four correction circuits described above, and therefore the two patterns described above did not match on the screen 1, significantly degrading the quality of the screen.

The present invention is intended to solve the above problem, and eliminates the slope distortion as shown in Figure 5 by modulating the voltage applied to the horizontal linear distortion correction coil of the cathode ray tube with a V-period sawtooth waveform or parabolic waveform. It was designed to do so.

First, before explaining the present invention, the principle of horizontal linear distortion correction will be explained with reference to FIGS. 6A, B, and C.

In color television receivers, due to distortions in the characteristics of the horizontal deflection circuit, horizontal linear distortion occurs in which the width of the crosshatch gradually narrows toward the right of the screen, as shown by the solid line in FIG. 6A.

In order to eliminate this horizontal linear distortion, a correction coil 7 is provided in addition to the horizontal deflection coil 6 at the neck of the cathode ray tube 2, as shown in FIG. I try to do that.

Due to this pre-deflection, the electron beam 8 reaches the 0 point on the fluorescent surface of the cathode ray tube 2, changing from the zero point it would reach if it is not pre-deflected, and the amount of change is proportional to the magnitude of the current flowing through the correction coil 7. do.

Therefore, when a parabolic current 9 with an H period (horizontal scanning period) as shown in FIG.
The screen shown by the solid line in the figure is corrected, and a screen with good linearity as shown by the dotted line can be obtained.

Next, embodiments of the present invention will be described with reference to the drawings.

- When the parabolic current 9 of the H period flowing through the correction coil 7 is modulated in amplitude with a sawtooth wave of the V period (vertical scanning period) as shown in FIG. 7B, as shown by the chain line in FIG. 7A, The amount of linear distortion correction gradually decreases at the top of the screen, and increases as it moves toward the bottom of the screen.

Note that the screen indicated by solid lines and dotted lines in FIG. 7A is the same as that in FIG. 6A.

FIG. 7C shows only the screen indicated by the chain line in FIG. 7A, and is approximately parallelogram-shaped.

Next, the screen shown in FIG. 7C is corrected into a rectangle by adjusting the orthogonality between the horizontal deflection coil and the vertical deflection coil, that is, by adjusting the H and CRO3S correction circuits, the screen shown in FIG. 8 is obtained.

This screen in Figure 8 has a rectangular peripheral part of the parallelogram screen in Figure 7C, so the tilt distortion in the center part is as shown in Figure 7C.
The slope is greater than the slope of the central part of the area.

The tilt distortion shown in FIG. 8 is tilted in the opposite direction to the screen tilt distortion shown by the solid line caused by the cathode ray tubes 2B and 2R in FIG. 5, that is, in the direction that corrects the distortion shown in FIG. There is.

The screen shown in FIG. 8 can be created by adjusting the level of the V-period sawtooth wave that modulates the amplitude of the parabolic wave shown in FIG. The inclination angle of the inclination distortion in the central part can be freely adjusted.

In addition, in Figure 7B, the parabolic current is amplitude-modulated with a sawtooth wave whose level increases, but this is amplitude-modulated with a sawtooth wave whose level increases, but this is amplitude-modulated with a sawtooth wave whose level decreases. If it is made larger at the top of the screen and smaller at the bottom, a parallelogram screen tilted in the opposite direction to the screen shown in FIG. 7C is obtained.

When this is corrected to a rectangular screen by H,CRO8S correction, a screen is obtained in which the central part of the screen shown in FIG. 8 is tilted in the opposite direction.

This screen can correct the distortion of the screen projected by the cathode ray tube 2G indicated by the dotted line in FIG.

According to the above, the three cathode ray tubes 2G, 2B, and 2R are
When a screen with various projection distortions as shown in Fig. 3 is projected onto a flat screen 1 by a color projector arranged as shown in Figs.
,D, the screen shown in FIG. 5 is obtained. Next, the current shown in FIG. By performing the correction as shown in FIG. 5, the screen distortion shown in FIG. 5 can be removed.

Next, a case where the screen 1 has a curvature as shown by the dotted line in FIG. 1 will be described.

In this case, the distortion will be as shown by the dotted line in Figure 3, and if this is corrected as shown in Figure 4 A, B, C, and D, the final screen will have a distortion in which the center part is curved in an arched shape. .

And in the correction coil 7 of each cathode ray tube 2G, 2B, 2R,
A current whose amplitude is modulated by a parabolic current with an H period as shown in FIG. 9 is passed, and H, BOW
When the correction is performed, a screen having an arcuate distortion curved in a direction that corrects the above-mentioned arcuate distortion as shown in FIG. 10 is obtained.

Next, an embodiment of a circuit for performing the above correction will be described with reference to FIG. 11.

In FIG. 11, a parabolic voltage with a V period is applied to the input terminal 20, and a sawtooth wave voltage with a V period is applied to the input terminal 21.

The amplitude of the parabolic voltage is adjusted by a variable resistor 23 via a capacitor 22, and the amplitude of the sawtooth voltage is adjusted by a variable resistor 25 via a capacitor 24.

The amplitude-adjusted parabolic voltage is applied to the base of the transistor 29 via the resistor 26 and the capacitor 27,
The amplitude-adjusted sawtooth voltage is applied to the base of a transistor 29 via a resistor 28 and a capacitor 27.

A bias voltage obtained by dividing the power supply voltage element B applied to the power supply terminal 30 by resistors 31 and 32 and a variable resistor 33 is further applied to this base.

The emitter of this transistor 29 is grounded via a resistor 34, and the collector is connected to the power supply terminal 30 via a load resistor 35 and to the base of a transistor 36.

The collector of this transistor 36 is connected to the power supply terminal 30, and the emitter is connected to one end of the primary coil of a transformer 37 and grounded via a capacitor 38.

The other end of the primary coil of the transformer 37 is connected to the horizontal output circuit 3
connected to the collector of the transistor 40 constituting the transistor 9;
This collector also has a resonant capacitor 41. A damper diode 42 and a horizontal deflection coil 46 are connected.

The base of this transistor 40 has a horizontal drive circuit (
(not shown), a drive pulse of H period is applied via the terminal 43.

One end of the secondary coil of the transformer 37 is grounded, and the other end is grounded via the integrating coil 46 and the correction coil 7.

Further, a series circuit of a capacitor 44 and a resistor 45 is connected in parallel to the correction coil 7.

Next, the operation of the above configuration will be explained.

When a V-period sawtooth voltage is applied to the input terminal 21, the amplitude of this sawtooth voltage is adjusted by a variable resistor 23 and then applied to the base of a transistor 29 via a resistor 26 and a capacitor 27.

Therefore, a sawtooth voltage having substantially the same phase as the above sawtooth voltage is outputted to the emitter of the transistor 36, and this voltage is applied to the primary coil of the transformer 37.

On the other hand, a pulse with an H period is applied to the base of the transistor 40 from a terminal 43, whereby the above-mentioned sawtooth voltage is switched with an H period, and thereby the above pulse has a waveform whose amplitude is modulated by a sawtooth wave with a V period. An output voltage having the following value is taken out from the secondary coils of the lances 1 to 37 and applied to the integrating coil 46.

Furthermore, the above output voltage is integrated by a capacitor 44 and a resistor 45 to become the voltage shown in FIG. can do.

Incidentally, FIG. 12A shows a current waveform flowing through the correction coil 7.

Furthermore, when a V-period parabolic voltage is applied to the input terminal 20, it is possible to remove bow distortion that occurs in a screen having curvature.

Incidentally, in actual screens, both slope distortion and bow distortion often occur, but in that case, both parabolic voltage and sawtooth voltage are applied to the input terminals 20 and 21, and these combined voltages are switched. This output voltage is corrected by coil 7.
The above two distortions may be removed by flowing the current to the current.

The above is a case where the screen in Figure 3 is made into a rectangle at the periphery as shown in Figure 5 by the corrections shown in Figures A, B, C, and D in Figure 4, and then the tilt distortion in the center is removed. However, conversely, it is also possible to remove the oblique distortion or arcuate distortion in the central part and then remove the distortion in the peripheral part.

The present invention provides a multi-tube projector in which a single image is obtained on the screen by projecting reproduced images from a plurality of cathode ray tubes onto the screen at a predetermined projection angle. A horizontal linear distortion correction coil is provided in the section, and a parabolic wave current with a horizontal period modulated by a sawtooth wave signal with a vertical period or a parabolic wave signal with a vertical period is supplied to the correction coil to be projected onto the screen. The present invention relates to a projection distortion correction device characterized in that it corrects asymmetric distortion of an image.

Therefore, according to the present invention, the asymmetrical distortion that occurs in this type of projector can be removed with a simple circuit, and the screens of each cathode ray tube can be made to coincide on the screen.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the principle of a multi-tube color projector to which the present invention can be applied; Fig. 2 is a side view of Fig. 1; Fig. 3 is a front view showing a screen with projection distortion; 4 Figures A, B, C
, D are schematic diagrams of screens for explaining the conventional correction method, FIG. 5 is a front view of the screen corrected by the method of FIG. Front view of the screen, waveform diagram and line plan view of the cathode ray tube, Figures 7A and B
, C is a front view of the screen, a waveform diagram, and a front view of the screen for explaining the principle of correction according to the present invention, FIG. 8 is a front view of the screen obtained by the method of FIG. 7, and FIG. 9 is a front view of the screen. A voltage waveform diagram of the correction coil when there is a curvature, Fig. 10 is a front view of a screen with an arcuate shape, Fig. 11 is a circuit diagram showing an embodiment of the present invention, and Fig. 12 is a diagram of the correction coil of Fig. 11. It is a current and voltage waveform diagram. In the symbols used in the drawings, 1 is a screen, 2G, 2B, and 2R are cathode ray tubes, 6 is a horizontal deflection coil, and 7 is a horizontal linear distortion correction coil.

Claims (1)

[Scope of utility model registration request] In a multi-tube projector that obtains a single image on the screen by projecting reproduced images from a plurality of cathode ray tubes onto the screen at a predetermined projection angle, a horizontal straight line is attached to the neck portions of the plurality of cathode ray tubes. By providing a distortion correction coil and supplying a horizontal period parabolic wave current modulated by a vertical period sawtooth wave signal or a vertical period parabolic wave signal to the correction coil, asymmetric distortion of the image projected on the screen is eliminated. A projection distortion correction device characterized in that it corrects.