JPH023260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a projection television apparatus.

Generally, a projection television device using a projection tube has a projection tube 1, a lens 2,
It consists of screen 4, etc. In such a projection television apparatus, as shown in FIG. 1, a projection optical axis 3 consisting of a projection tube 1 and a lens 2
is perpendicular to screen 4, projection tube 1
The image is linearly expanded as it is and displayed on screen 4.
, and if the image reproduced on the projection tube 1 is a rectangular pattern, the image on the screen 4 will also be the third pattern.
It appears as a precise rectangular pattern 5 as shown in the figure. However, as shown in Fig. 2, if the projection optical axis 3 consisting of the projection tube 1 and lens 2 is horizontally inclined by a certain angle θ with respect to the screen 4, the image on the fluorescent screen of the projection tube 1 will not be accurate. Even if the pattern is a rectangular one, the image reproduced on the screen 4 will be a pattern 6 with horizontal trapezoidal distortion as shown in FIG. In order to correct the horizontal keystone distortion that occurs in the pattern 6, the image reproduced on the projection tube 1 is first distorted in the opposite shape, and the horizontal keystone distortion caused by the tilted projection optical axis 3 is corrected. It is necessary to offset the

In a conventional projection television apparatus, as shown in FIG. A trapezoidal distortion correction circuit dedicated to the yoke 8 is provided to distort the image reproduced on the projection tube 1 and correct the trapezoidal distortion occurring in the image reproduced on the screen 4.

However, the electric circuit for correcting this trapezoidal distortion is not only complicated, but also has the drawback of being unstable with respect to electrical fluctuations. In particular, three projection tubes 1 of red R, green G, and blue B as shown in FIG.
Three primary color lights of red, green, and blue from B, 1G, and 1R 3
When trying to obtain a color image by projecting R, 3G, and 3B from separate positions and mixing them on the screen 4, this correction circuit becomes even more complicated, and not only is it not economical, but the adjustment is difficult. It will be extremely difficult. Electrical fluctuations in this case result in color shift on the screen 4, deteriorating the image quality, so the correction circuit is required to have a high degree of stability.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a projection type television apparatus in which a projection tube is installed so that the optical axis of the projection light emitted from the projection tube is inclined horizontally with respect to the screen.
An object of the present invention is to provide a projection type television device capable of reducing horizontal trapezoidal distortion occurring in an image reproduced on a screen without having a horizontal trapezoidal distortion correction circuit.

The present invention will be explained below using examples. In order to correct the horizontal keystone distortion that occurs in the image played on the screen, it is necessary to prepare an image in advance that has horizontal keystone distortion in the opposite direction vertically and horizontally to the horizontal keystone distortion that occurs in the image played on the screen. This can be offset by forming the image on the screen being reproduced by a projection tube and projecting this image onto the screen.

FIG. 6 is a schematic diagram showing how the electron beam of the projection television apparatus according to the present invention is deflected.
A beam bender 10 consisting of a pair of ring-shaped bipolar magnets is installed between the deflection yoke 7 and the electron gun 9. Even when no current flows through the deflection yoke 7 and there is no deflection, the electron beam is 13a
reaches a position shifted by a distance dc from the center O of the fluorescent screen 11 of the projection tube 1 in the direction of arrow A. That is,
The beam bender 10 functions to bend the trajectory of the electron beam 13. When the deflection yoke 7 is not deflected, the amount of deflection on the plane 12 perpendicular to the electron beam 13a is approximately proportional to the deflection current _IH flowing through the deflection yoke 7 when the magnetic field generated by the deflection yoke 7 is uniform.
It is uniform. On the other hand, as the waveform of the conventional horizontal deflection current I _H is shown by the broken line 19a in FIG. It is. However, in the present invention, the horizontal deflection current I _H is determined by the solid line 1 in the same figure.
As shown by 9b, the current has the value of _IHC even at time tc. The amount of deflection of the electron beam by this horizontal deflection current I _HC is determined by the amount of deflection of the electron beam by the phosphor screen 1 of the projection tube 1 shown in FIG.
If it is determined to correspond to the distance dc on 1, then
The electron beam 13a bent by the distance dc by the beam bender 10 can be positioned at the center O of the phosphor screen 11. At this time, if the horizontal deflection magnetic field and the vertical deflection magnetic field of the deflection yoke 7 are uniform magnetic fields, almost no horizontal trapezoidal distortion occurs on the plane 12 perpendicular to the electron beam 13a when the deflection yoke 7 is not deflected as shown in FIG. do not have. However, as shown in FIGS. 7 and 8, normally the horizontal deflection magnetic field 16 generated by the horizontal deflection coil 15 has a pincushion shape, and the vertical deflection magnetic field 18 generated by the vertical deflection coil 17 has a barrel shape. Since the electron beam 13b deflected in the direction of arrow A has a trajectory farther from the center 14 of the deflection yoke 7 than the electron beam 13c deflected in the direction of arrow B, compared to the case where the electron beam 13b is deflected by a uniform magnetic field, electron beam 13b
passes through a position where the horizontal deflection magnetic field and the vertical deflection magnetic field are stronger than those of the electron beam 13c. Therefore, the electron beam 13b is deflected more than the electron beam 13c, causing horizontal trapezoidal distortion on the plane 12 shown in FIG. Furthermore, since the phosphor screen 11 and the plane 12 are inclined, this horizontal trapezoidal distortion tends to be further emphasized on the phosphor screen 11, and the pattern 6 with horizontal trapezoidal distortion as shown in FIG. It is formed. When this distorted image is projected onto the screen of a projection television device, the image becomes rectangular and the distortion of the image is canceled out.

Note that if the central axis 14 of the deflection yoke 7 is shifted horizontally with respect to the central axis 20 of the projection tube 1 as shown in FIG. 11, the horizontal trapezoidal distortion occurring on the phosphor screen 11 in FIG. 6 can be further strengthened. Can be done.

Note that there are two methods for flowing the horizontal deflection current _IHC at time tc: a method of superimposing a direct current on the conventional horizontal deflection current waveform 19a, and a method of shifting the phase of the video signal with respect to the horizontal deflection current waveform. You can also use this method.

Furthermore, as is clear from Fig. 5, the projection tube 1B
The horizontal trapezoidal distortion of the image reproduced on the screen 4 by the projection tube 1R and the projection tube 1R are opposite to each other. Therefore, the projection television apparatus according to the present invention described above can only be used for either one of the projection tubes 1R and 1B. However, as mentioned above, the projection tube 1R,
Since the horizontal trapezoidal distortion of the image reproduced on the screen 4 by the projection tube 1B is inverse to each other, for example, when the embodiment of the present invention described above is applied to the projection tube 1R, the projection tube 1B has an electronic Beam distance (-dc)
It is sufficient to use the beam bender 10 to be moved and the deflection yoke 7 on which a DC current is superimposed by the current (-I _HC ).

As explained above, according to the present invention, there is no need for a dedicated sub-deflection yoke or a trapezoidal distortion correction circuit for correcting the horizontal trapezoidal distortion that occurs as image distortion on the screen, and the horizontal keystone distortion can be corrected or The degree of horizontal keystone distortion can be reduced. Therefore, a complicated electrical correction circuit can be simplified and stable images can be obtained.

[Brief explanation of drawings]

Figures 1 and 2 are schematic diagrams showing the relative positional relationship between the screen and the projection tube in a projection television device, Figure 3 is a pattern diagram of the projected image reproduced on the screen, and Figure 4. 5 is a schematic diagram showing the configuration of a projection tube, deflection yoke, and sub-deflection yoke in a conventional projection television device, FIG. 5 is a schematic diagram showing a conventional projection color television device, and FIG. 6 is a diagram showing a projection tube according to the present invention. A schematic diagram showing how an electron beam is deflected by a projection tube, a deflection yoke, and a beam bender in a type television device;
FIG. 7 is a cross-sectional view of a deflection yoke for explaining the shape of the horizontal deflection magnetic field and the electron beam trajectory according to the present invention, and FIG. 8 is a cross-sectional view for explaining the shape of the vertical deflection magnetic field and the electron beam trajectory according to the present invention. 9 is a pattern diagram of an image reproduced on a fluorescent screen in a projection tube according to the present invention. FIG. 10 is a waveform diagram showing the waveform of a horizontal deflection current according to the present invention. The figure is a schematic diagram showing another embodiment according to the present invention. 1... Projection tube, 4... Screen, 7... Deflection yoke, 9... Electron gun, 10... Beam bender (electron beam moving means), _IHC ... Current.

Claims (1)

[Claims] 1. In a projection television device that projects an image reproduced on a phosphor screen of a projection tube from an oblique direction onto the screen, the projection tube has the following features: an electron gun that is arranged on the central axis of the projection tube and generates an electron beam; a deflection yoke that generates a pink-tension type horizontal deflection magnetic field and a barrel-type vertical deflection magnetic field; and a gap between the electron gun and the deflection yoke. 2 arranged on the projection tube and formed in a pair of ring shapes.
1. A projection television apparatus comprising a beam bender made of a polar magnet and horizontally moving an electron beam emitted from an electron gun by a predetermined distance.