JPS622752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Projection display devices are known that allow images projected on a cathode ray tube to be enlarged and viewed.

As shown in FIG. 1, it consists of a projection cathode ray tube 1, a reflecting mirror 2, a lens 3, and a screen 4, and the cathode ray tube 1 used is one with particularly high brightness. The image projected on the screen of the cathode ray tube 1 passes through the reflector 2 and lens 3 to the screen 4.
It is enlarged and projected upwards for display.

By the way, the aspect ratio of the screen size of television images is determined to be 3:4, but in order to make the image more powerful, such as in CinemaScope, it is better to make the image more horizontal. .

In particular, when viewing an impressive screen in a place where the ceiling is relatively wide, such as inside an airplane, but the ceiling is at the bottom, it is preferable and effective to use a horizontally long screen.

In view of the above-mentioned points, the present invention provides a projection display device in which a display image can be made laterally longer than a television image.

By the way, in television receivers, the horizontal and vertical amplitudes of the raster are adjusted so that they are overscanned by 10 to 18%. In other words, as shown in Fig. 2, the raster horizontal,
The vertical amplitude (indicated by the dashed line in the figure) is made larger, so that about 10 to 18% of the image is not displayed on the screen. Generally, the overscan amount is made to have the same ratio both horizontally and vertically.

In this invention, the projected image can be made horizontally elongated by skillfully utilizing the overscan area on the screen of the television receiver, that is, the cathode ray tube.

Hereinafter, an embodiment of the image display device according to the present invention will be described with the screen 4 having an aspect ratio of 5:8.
Let's explain using an example where the image is horizontally long.

That is, as shown in FIG. 3, first, the size of the screen 1a of the cathode ray tube 1 is adjusted so that the horizontal and vertical amplitudes of the raster coincide with each other, so that the amount of overscan in the cathode ray tube 1 is zero. .

Then, the vertically shaded portion BL of the screen 1a of the cathode ray tube 1 in FIG. 3 is optically shielded, for example. In this case, the area of the shielded portion is about 18% in total of the vertical image size, with about 9% each on the top and bottom.

In this way, the image visible on the cathode ray tube 1 will have an aspect ratio of approximately 5:8. Therefore, if this image is projected onto the screen 4, the horizontally long image will be displayed to fill the entire screen 4 since the screen 4 has an aspect ratio of 5:8.

That is, as shown in FIG. 3, the screen 4 displays a horizontally elongated television image in which the overscan amount in the horizontal direction is zero and the overscan amount in the vertical direction is 18%. It is something.

In this case, the limit value of the amount of overscan in the vertical direction is the limit value at which the text of the caption does not become vignetted, that is, 18%. Therefore, when the screen 4 is made horizontally long, the maximum aspect ratio is 4.92:8.

In very special cases, when you want to view graphs or tables up to the top and bottom, you can reduce the horizontal and vertical amplitude of the cathode ray tube image without changing the projection magnification. ,
As shown in Figure 4, a screen 4 with an aspect ratio of 5:8
A screen with an aspect ratio of 3:4 can be displayed on top.
In this case, there are areas on the left and right sides of the screen 4 where nothing is displayed.

Figure 5 shows the horizontal direction of the image projected on the cathode ray tube.
An example of a vertical amplitude adjustment and switching circuit includes a vertical deflection yoke 5, a horizontal deflection yoke 6, a vertical drive circuit 7, a horizontal drive circuit 8, a vertical output circuit 9, and a horizontal output circuit 10. 11 is a vertical amplitude adjustment circuit; 12 is a horizontal amplitude adjustment circuit;
A and 11B are vertical amplitude adjustment volumes, and 12A and 12B are horizontal amplitude adjustment volumes. Further, 13 is a terminal to which a sawtooth wave voltage having a vertical period is supplied, and 14 is a terminal to which a sawtooth wave voltage having a horizontal period is supplied.

15 and 16 are switches for changing the image size,
When these switches 15 and 16 are connected to the state shown in the figure, the volumes 11A and 12A are adjusted.
The horizontal and vertical amplitudes of the raster are made equal to those of the cathode ray tube screen. In this state, by shielding the screen 1a of the cathode ray tube 1 by optically masking the top and bottom in the vertical direction as shown in FIG. 3, a 5:8 horizontally long image is displayed on the screen 4. .

Next, when switches 15 and 16 are connected in a state opposite to that shown in the figure, the volume 11
The horizontal and vertical amplitudes of the raster are reduced by B and 12B, so that a 3:4 image is displayed on the screen 4 as shown in FIG. In this case, vertical optical shielding in the upper and lower directions is not performed; for example, the shielding mask is removed from the screen in conjunction with switching of a switch.

As described above, according to the present invention, by skillfully utilizing the overscan portion of a television image, it is possible to obtain a horizontally long image that is more powerful than a television image.

In addition, in the above-mentioned embodiment, when creating a more horizontally elongated image, the upper and lower parts of the screen in the vertical direction are optically shielded, but instead of optically shielding, the upper and lower parts of the image are electrically shielded. Exactly the same effect can be obtained by blanking in terms of signal processing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of an example of a projection display device, FIG. 2 is a diagram for explaining a television image, and FIG. 3 is a diagram for explaining a screen of an example of an image display device according to the present invention. , 4th
The figure shows one aspect of the display image of this invention device;
FIG. 5 is a diagram showing an example of an image size adjustment circuit. 1 is a cathode ray tube, 1a is its screen, 3 is a lens,
4 is a screen.

Claims (1)

[Claims] 1. In devices that display an enlarged image on a screen by projecting an image projected on a cathode ray tube, the cathode ray tube is scanned so that the screen size and the horizontal and vertical amplitudes of the raster are approximately equal. Make sure there is almost no overscan,
It is possible to display areas that are not normally displayed on the screen, and by optically or electrically blanking the top and bottom of the cathode ray tube screen in the vertical direction, an image that is laterally longer than the cathode ray tube screen is displayed on the screen. An image display device designed to obtain