JPH06266010A - Rear projection type video display device - Google Patents

Abstract

PURPOSE:To reduce the deterioration of a projection screen and to drastically improve the white uniformity, the color reproducing range and the contrast of an image on the projection screen by forming the width of a black-stripe at the central part of transparent and hard screen wider than the width of the black stripe in a peripheral part. CONSTITUTION:The transparent and hard screen 22 constituting the front surface of the projection screen is formed out of a hard plastic resin and both surfaces thereof are flat. Then, a black-stripe layer 25 obtained by forming the black stripes 24, which are slander in the vertical direction, in parallel and in the horizontal direction at a prescribed pitch is provided on the surface of the observer side of the screen 22. As to the layer 25, an interval between the stripes 24 is changed by making the width of the stripe 24 at the central part of the screen 22 wide and making it narrower toward the peripheral part so that the brightness of the image on the projection screen is not excessively reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection type image display apparatus for enlarging and projecting an image obtained by a cathode ray tube or a liquid crystal panel on the back surface of a projection screen and viewing the projected image from the front surface of the projection screen. In particular, the present invention relates to a rear projection type image display device for improving the image quality on the projection screen.

[0002]

2. Description of the Related Art Conventionally, there is a projection type image display apparatus for enlarging and displaying a television image or the like on a projection screen. As shown in FIG. 4, this projection-type image display device generally includes three monochromatic cathode ray tubes 1a each having a phosphor screen made of a monochromatic phosphor that emits any one of blue, green, and red. , 1b, 1c are each equipped with a projection lens 2, and the projection lens 2 allows the cathode ray tubes 1a, 1b, 1c to be arranged.
The cathode ray tube method in which a color image is displayed by enlarging an image drawn on the phosphor screen and projecting it on the projection screen 3 has become mainstream.

In addition, as shown in FIG. 5, two dichroic filters 6a and 6b and one mirror 7 are arranged on the back surface of three liquid crystal panels 5a, 5b and 5c, and a white lamp is provided.
Eight rays of light are divided into blue, green and red by the two dichroic filters 6a and 6b, and the divided light of each color is divided into pixels of liquid crystal panels 5a, 5b and 5c arranged at corresponding positions. By opening and closing as a shutter, only the necessary light is transmitted, and the transmitted light is magnified by the projection lens 2 arranged on the front surface of each liquid crystal panel 5a, 5b, 5c and projected on the projection screen 3 to produce a color image. There is something to display.

In the projection type image display apparatus shown in FIGS. 4 and 5, the projection type image is projected on the front surface of the projection screen 3 by the projection lens 2 and the projection type screen is viewed from the front side. There is a transmissive type that projects on the back of 3 and looks from the front.

Further, as a home projection type image display device, there is a device which is less affected by external light and can be viewed with normal room brightness. As shown in FIG. 6, this projection-type image display device includes three monochromatic cathode ray tubes 1a, 1b, 1c (provided with a phosphor screen made of a monochromatic phosphor that emits any of blue, green, and red. Projection lens 2 is placed on the front side of (only 1a is shown).
The image drawn on the phosphor screen of each cathode ray tube 1a, 1b, 1c is magnified by 2 and this image is reflected by the mirror 7 placed in front of it on the back surface of the projection screen 3 and the projection screen 3 The color image obtained above is assembled into a rear projection type using a transmissive projection screen 3 for viewing from the front side of the projection screen 3.

Among these projection type image display devices, the conventional transmission type projection screen 3 for projecting an image on the back side of the projection screen 3 and viewing it from the front side is arranged on the side of the projection lens as shown in FIG. , A Fresnel lens 10 that collects the light projected through the projection lens toward the viewer, and a lenticular lens 11 that is arranged on the viewer side and that efficiently distributes a certain amount of light in the viewing range. The lenticular lens 11 is composed of a combination of 1 to 3 lens screens, and a black stripe 12 is formed on the lenticular lens 11 to improve image contrast.

[0007]

As described above, as a projection type image display device, an image obtained from a cathode ray tube or a liquid crystal panel is enlarged and projected on the back surface of a projection screen through a projection lens, and the image is projected. There is a rear projection type image display device using a transmissive projection screen for viewing an image from the front of the projection screen. This rear projection type video display device has a strong visibility of the image obtained on the projection screen,
Optimal viewing range is narrow. Therefore, the projection screen of this rear projection type image display device has a conventional display screen of 0.7 to 1.
A lenticular lens in which a complicated fine pattern is formed at a pitch of about 0 mm is used.

However, since this lenticular lens is made of soft plastic or acrylic resin having good moldability, it is easily scratched, and is easily soiled due to a complicated fine pattern. I have a problem. Also, on the projection screen,
Although the image magnified by the projection lens is projected, the brightness of the projected image from the center of the projection screen to the peripheral part decreases in proportion to the fourth power of the cosine of the angle of view from the center of the lenticular lens. There is a problem that the white uniformity of the image on the projection screen is not good.

Further, in the projection type image display apparatus using the cathode ray tube, the terbium activated rare earth phosphor is used for the phosphor screen of the cathode ray tube for the green image. However, this rare earth phosphor has a problem that the emission color is close to yellowish green and the color reproduction range is narrow because the red subband exists in the emission spectrum.

The present invention has been made in view of the above problems, and it is possible to reduce the deterioration of the projection screen and significantly improve the white uniformity, the color reproduction range, and the contrast of the image on the projection screen. An object of the present invention is to configure a rear projection type image display device that can be used.

[0011]

A rear projection type in which an image obtained by a cathode ray tube or a liquid crystal panel is magnified by a projection lens and projected on the back of a projection screen, and the projected image is viewed from the front of the projection screen. In the image display device, a transparent hard screen with flat both sides is provided in front of the projection screen, a large number of black stripes are formed in parallel on this transparent hard screen, and the width of this black stripe at the center of the transparent hard screen is the black of the peripheral portion. It was formed wider than the width of the stripe.

[0012]

As described above, a transparent hard screen having flat both sides is provided on the front surface of the projection screen, and a large number of black stripes are formed in parallel on the transparent hard screen. When the width is larger than the width of the black stripe, the transparent hard screen is arranged in front of the lenticular lens that constitutes the projection screen, and the lenticular lens can be prevented from being scratched or soiled. On the other hand, the transparent hard screen is hard to be scratched because it is hard, and even if it gets dirty, the surface is flat,
It can be easily removed by washing or the like. Furthermore, it is easy to form a black stripe on a transparent hard screen with a flat surface, the stripe width of each part can be changed arbitrarily, and the stripe width of the central part is wider than the stripe width of the peripheral part. Then, by reducing the transmittance in the central portion, it is possible to improve the white uniformity and the contrast over the entire screen.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

The overall structure of the rear projection type image display device is the same as that of the projection type image display device shown in FIGS. 4 to 6. That is, as for the cathode ray tube type rear projection type image display device, as shown in FIGS.
Projection lenses are arranged in front of three monochromatic cathode ray tubes each having a phosphor screen made of a monochromatic phosphor that emits blue, green, or red, and are drawn on the phosphor screen of each cathode ray tube. It is formed in a structure in which an image is enlarged by a projection lens and projected on the back surface of a projection screen described later. Further, in the projection type image display device shown in FIG. 5, two dichroic filters and one mirror are arranged on the back surface of three liquid crystal panels,
Place a projection lens on the front of each LCD panel,
The light of the white lamp is split into blue, green, and red by two dichroic filters, and the split light of each color is opened and closed so that only the necessary light is transmitted through the pixels of the liquid crystal panel, and the transmitted light. Is enlarged by a projection lens and projected on the back surface of a projection screen described later.

As shown in FIG. 1, the projection screen of each of the above projection type image display devices has a Fresnel lens 20 arranged on the projection lens side and constituting the back surface of the projection screen, and a Fresnel lens 20 adjacent to the Fresnel lens 20. Substantially two lenticular lenses 21 each having a vertical lenticular lens and a horizontal lenticular lens formed on both sides, and a transparent hard screen which is arranged adjacent to the lenticular lens 21 and constitutes the front surface of the projection screen. It consists of 22 and.

The transparent hard screen 22 is made of a hard plastic resin, and both surfaces thereof are flat surfaces. And this transparent hard screen 22
On the viewer-side surface, a black stripe layer 25 is provided in which black stripes 24 elongated in the vertical direction are formed in parallel in the horizontal direction at a predetermined pitch. This black stripe layer 25 covers 50% of the total screen area of the projection screen so as not to reduce the brightness of the image on the projection screen too much.
% Or less, and the width of the black stripe 24 in the central portion of the transparent hard screen 22 is widened and narrowed toward the peripheral portion so as to cancel the 4th law of the angle of view related to the brightness of the screen. The gap between the stripes 24 is changed.

Further, in a projection screen for enlarging and projecting a three-color image of blue, green and red obtained from a cathode ray tube, a wavelength selective absorption layer 26 is provided in the gap between the black stripe layers 25. This wavelength selective absorption layer 26 is for improving the deterioration of color reproducibility due to the emission spectrum distribution of the phosphor used in the phosphor screen of the cathode ray tube for green image, and is shown by the curve 28 in FIG. like,
570-6 out of the emission spectrum 29 of the green-emitting phosphor
It is formed of a material that lowers the subband 30 of 00 nm.

When the projection screen is constructed as described above,
Due to the transparent hard screen 22 arranged in front of it,
It is possible to protect the lenticular lens 21 that is susceptible to scratches and stains, and prevent scratches and stains on the lenticular lens, which has been a problem in the past. On the other hand, this transparent hard screen 22 is hard to be scratched because it is hard, and has a flat surface even if it becomes dirty, so that it can be easily removed by washing or the like. Further, since the black stripe layer 25 is formed on the transparent hard screen 22 having a flat surface, the black stripe layer 25 is easily formed, and the stripe width of each part can be arbitrarily changed. By making the width wider than the width and reducing the transmittance in the central portion, it is possible to improve the white uniformity and the contrast over the entire screen.

Further, the projection screen for enlarging and projecting the three-color image of blue, green and red obtained from the cathode ray tube is used as the phosphor screen of the cathode ray tube for the green image in the gap portion of the black stripe layer 25. 570-600 nm sub-band due to the emission spectrum distribution of the phosphor 29
By providing the wavelength selective absorption layer 26 that lowers the color reproducibility, the color reproducibility of the image on the projection screen can be improved.

FIG. 3 shows a different configuration of the projection screen. In this projection screen, a Fresnel lens 20 and a lenticular lens 21 arranged on the projection lens side are substantially formed by a single lens 32, and a transparent hard screen 22 adjacent to the lenticular lens 21 and having flat both surfaces is provided.
Are arranged. A black stripe layer 25 is formed on the viewing side of the transparent hard screen 22. With the projection screen having such a configuration, the same effects as those of the projection screen of the above-described embodiment can be obtained.

The same effect can be obtained by disposing two lenticular lenses adjacent to the Fresnel lens and disposing a transparent hard screen on the viewing side.

[0022]

EFFECTS OF THE INVENTION In a rear projection type image display device in which an image obtained by a cathode ray tube or a liquid crystal panel is enlarged by a projection lens and projected on the rear surface of a projection screen, and the projected image is viewed from the front surface of the projection screen. A transparent hard screen with flat both sides is provided on the front of the screen, and a large number of black stripes are formed in parallel on this transparent hard screen, and the width of this black stripe at the center of the transparent hard screen is wider than the width of the black stripes at the periphery. Once formed, the transparent hard screen will
Since it is arranged in front of the lenticular lens that constitutes the projection screen, the lenticular lens that is likely to be scratched or soiled can be protected, and the scratching or soiling can be prevented. On the other hand, the transparent hard screen is hard to be scratched and has a flat surface even if it becomes dirty, so that it can be easily removed by washing or the like. Also, since the surface is flat, black stripes can be easily formed, and the central stripe width is made wider than the peripheral stripe width to lower the central transmittance, thus making it possible to create a white uniform across the entire screen. It is possible to obtain effects such as good miti and contrast.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a projection screen of a rear projection type image display device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a relationship between an emission spectrum of a green light emitting phosphor and a wavelength selection absorption layer provided on a transparent hard screen of a projection screen.

FIG. 3 is a diagram showing a configuration of a projection screen according to another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of an example of a conventional projection-type image display device.

FIG. 5 is a diagram showing a configuration of a different conventional projection-type image display device.

FIG. 6 is a diagram showing a configuration of still another conventional projection-type image display device.

FIG. 7 is a diagram showing a configuration of a projection screen of a conventional projection-type image display device.

[Explanation of symbols]

 20 ... Fresnel lens 21 ... Lenticular lens 22 ... Transparent hard screen 24 ... Black stripe 25 ... Black stripe layer 26 ... Wavelength selective absorption layer

Claims (1)

[Claims] 1. A rear projection type image display apparatus for enlarging an image obtained by a cathode ray tube or a liquid crystal panel by a projection lens and projecting the image on the back surface of the projection screen, and viewing the projected image from the front surface of the projection screen. In the projection screen, a transparent hard screen with flat both sides is provided on the front surface, and a large number of black stripes are formed in parallel on the transparent hard screen, and the width of the black stripe at the center of the transparent hard screen is the black stripe of the peripheral portion. A rear projection type video display device characterized by being formed wider than the width of the.