JP2625535B2 - Projection image display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display device, and more particularly, to a projection type image display device capable of improving its focus performance on a screen surface and color unevenness in an image. The present invention relates to an image display device.

[Conventional technology]

The projection type image display device usually has a red,
Green and blue projection tubes (1R, 1G, 1B, respectively) and three projection lenses (2R, 2G, 2B, respectively) are arranged horizontally,
This is a device for obtaining a color image by projecting and combining the images on the respective projection tubes 1R, 1G, 1B onto a screen 3 arranged in front of the projection lenses 2R, 2G, 2B.

In such a projection type image display device, three projection tubes 1
Since the R, 1G, 1B and the three lenses 2R, 2G, 2B interfere with each other locally, it is not possible to arrange all the projection tubes on the central axis of the screen 3 at the same time. The projection lens 2G is placed on the central axis of the screen 3, and the other two colors are arranged on both sides of the screen 3 so that the optical axis faces the center of the screen 3. For this reason, the image projected on the screen by the central projection optical system is substantially rectangular, but the image projected by the projection optical systems on both sides becomes trapezoidal as it is. In order to make this a correct substantially rectangular color image on the screen, the images on the phosphor screens of the projection tubes 1R and 1B on both sides are corrected in advance to reverse trapezoids, and the substantially rectangular image is displayed on the screen. You need to be able to get exactly.

This is shown in FIG. As shown in FIG. 7, since the red projection tube 1R and the projection lens 2R project from the left side with respect to the center axis of the screen 3, the magnification is low on the left side of the screen 3 and high on the right side of the screen 3. Therefore, the image on the phosphor screen is corrected in advance to an inverse trapezoid so as to cancel this, so that the image on the phosphor screen 7 is replaced with the image on the phosphor screen 7 as shown in 6R in FIG. A trapezoidal image is large on the right side and small on the left side with respect to the center C of the surface 7.

The image 6R on the red fluorescent screen is almost completely filled on the right side with respect to the effective raster area 8 of the fluorescent screen 7 on the projection tube, while the left side has enough room. On the contrary, in the case of the blue projection tube 1B and the projection lens 2B, an image of 6B is formed on the phosphor screen, and the left side of the effective raster area 8 is almost almost full, while the right side is too much. I have room. Accordingly, the image on the phosphor screen of the green projection tube 1G and the projection lens 2G on the central axis of the screen 3 is 6G, and there is a margin on both sides with respect to the effective raster area 8.

In this case, the projection tube fluorescent screen 7 is not fully utilized, and the projection optical system is wasteful in terms of brightness and focus. Also, if there is assembly variation of the projection optical system, especially in red and blue, the raster is projected to the left or right in the phosphor screen effective raster area, so that an image of a desired size cannot be obtained. So-called screen chipping occurs.

In order to solve the above problems and improve the focus performance in the projection optical system, reduce color unevenness, and increase reliability together, it is necessary to shift the optical axis of the projection tube 1R, 1B and the projection lens 2R, 2B. Widely used. This means that, as shown in FIG. 9, the projection lens 2R is located outside the red projection tube 1R,
By shifting the projection lens 2B outward with respect to the blue projection tube 1B, the image 6'R on the red phosphor screen and the image 6'B on the blue phosphor screen are respectively projected as shown in FIG. This is a technique for positioning the phosphor screen 7 at the center C of the effective raster area 8. According to this, as shown in FIG. 10, the image 6'R on the red phosphor screen, the image 6'B on the blue phosphor screen,
Since all the images 6'G on the green phosphor screen are located at the center C of the effective raster area 8 of the projection tube phosphor screen 7,
The projection magnification is reduced, and each image 6'R, 6'G, 6'B
Can be used up to 8 full effective raster areas, and a projection optical system with no waste can be obtained.

[Problems to be solved by the invention]

In the above prior art, since it is necessary to shift the optical axes of the projection tubes 1R and 1B and the lenses 2R and 2B, the angle between the center axis of the screen 3 and the optical axes of the red and blue projection optical systems (concentration angle and Despite the increase in the keystone distortion, no consideration has been given to this point, and there has been a problem that the keystone distortion, color shift, color unevenness, and the like caused by the large concentration angle increase.

An object of the present invention is to enlarge the image on the green phosphor screen to the full effective raster area while reducing the concentration angle to less than that of the prior art, and to provide excellent brightness, focus, less color unevenness, and red and blue colors. An object of the present invention is to provide a projection type image display device in which a screen is not missing in an image.

[Means for Solving the Problems] In order to achieve the above object, according to the present invention, three projection tubes of red, green and blue are arranged such that green is located at the center and red and blue are located on both sides thereof. In a projection type image display device of a system in which an image from a tube is projected on the same rectangular screen through lenses arranged for each projection tube and superimposed and synthesized, a lens corresponding to a green projection tube located at the center is used. Compared to the projection distance (OBD) toward the screen, the projection distance from the lens corresponding to each of the red and blue projection tubes located on both sides toward the screen was increased.

[Action]

When the projection distance of the red and blue projection lenses is made longer than that of the green projection lens, and the red, green and blue projection tubes are viewed from the respective optical axis directions of the red, green and blue projection lenses, the green projection tube Since the configuration is such that a part and a part of the red or blue projection tube overlap each other, the red and blue projection tubes can be arranged closer to the green projection tube, and the angle of concentration can be reduced. In addition, since the projection distance of the red and blue compatible lenses can be used at a large magnification because of the long projection distance, at least the necessary raster margin (actual raster area for the effective raster area Required raster size).

Further, by making the total length of the red and blue projection tubes arranged on both sides of the green shorter than that of the green, the structural height of the rear projection type image display apparatus brought about by implementing the present invention can be improved. It is possible to reduce the increase in the height.

On the other hand, increasing the projection distance as described above leads to a reduction in the raster size on the phosphor screen. In this case, especially in a blue projection tube, luminance saturation of the phosphor screen is likely to occur, and therefore, this state remains unchanged. Brightness may not increase. Even in this case, by decreasing the brightness of the blue projection lens, it is possible to cover a decrease in the tube surface luminance due to luminance saturation.

〔Example〕

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

FIG. 1 is a top view showing one embodiment of the present invention, FIG. 2 is a top view showing another embodiment of the present invention, and FIG. 3 is a rear view of a projection type image display device embodying the present invention. Sectional view, fourth
FIG. 1 is a schematic view of the projection tube viewed from the direction of arrow A in FIG. 1, and FIGS. 5 and 6 are conceptual diagrams each showing a raster shape projected on the projection tube fluorescent screen. FIG. 2 is also a diagram showing the mutual positional relationship between the lens ends when the projection distance of the red and blue corresponding lenses is longer than the projection distance of the green corresponding lens.

1 to 3, 1G, 1R, and 1B are green,
Red and blue projection tubes, 2G, 2R, and 2B are projection lenses, and 3 is a screen.

In FIG. 1, what is indicated by a dotted line is a red or blue projection tube and projection lens according to the prior art. In this case, the same applies when the projection distance from the projection lens to the screen 3 is red, blue, and green.

In the present invention, as shown by solid lines, red and blue are projection lenses.
Set the projection distance of 2R and 2B to the projection distance of green projection lens 2G (OB
D) is used longer than ΔL so that the optical axes of the red, green, and blue projection lenses 2R, 2G, and 2B intersect at one point (O) on the screen 3.

Then, if desired, the green image raster (rectangle 6G in FIG. 5) 9 is set to fill the width (W) of the green projection tube fluorescent screen effective area, and the blue and red image rasters (trapezoid 6R in FIG. 5) are formed. Assuming that the amount protruding from the lateral width (W) is ΔW, ΔL is maximized, and the following relationship is satisfied: ΔL = OBD × (2ΔW / W) (1) That is, as ΔL, the ratio ΔW /
Extend OBD by W only. For example, in the case of OBD = 780 mm, 5.3 inch raster, W = 108 mm, ΔW = 5 mm, and ΔL ≒ 36 mm.

In addition, when a margin is taken in advance for the purpose of absorbing the protruding amount ΔW generated due to assembly variation or the like with respect to the width W, even if the margin is treated as ΔW, the effect intended by the present invention is the same.

FIG. 2 is a diagram for more specifically explaining the mutual positional relationship between the projection lenses for red and blue when the projection distance of the projection lens is longer than that for green by ΔL. Rather than the tip PG of the green corresponding projection lens 2G arranged in the center, the red and blue corresponding projection lenses 2R and 2B arranged at both sides have at least the projection lens tips PR and PB on the side closest to the projection lens 2G. It is arranged so as to be located rearward (upward in FIG. 2).

On the other hand, as shown in FIG.
When viewing the red, green, and blue projection tubes (1R, 1G, 1B) from the optical axis directions of R and 2B, respectively, a part of the green projection tube 1G and one of the red projection tube 1R or the blue projection tube 1B The parts are arranged so as to overlap each other as shown by diagonal lines in the figure, and the optical axes of the red, green, and blue projection lenses 2R, 2G, and 2B are positioned on the screen (point O) or from the screen as seen in FIG. At a distant position (point O '), they intersect each other at one point.

At this time, if desired, as shown in FIG. 6, the center of the red (blue) projection screen raster is shifted from the center of the screen by an amount (Δn) given by the following equation (2). Here, the shift amount ΔS ≒ Δn · M on the screen 3 is (M: lens magnification).

Assuming that the linearity distortion caused by oblique projection like a red or blue projection lens is δ and the effective raster width is W, the amount of lateral expansion is δ × (W / 2), and therefore, the actual projected The amount Δn = δ × (W / 2) of shifting the center of the raster to be shifted from the center of the tube surface is obtained. Linearity distortion δ
Increases in proportion to the concentration angle θ and the screen width Ws, and increases as the projection distance (OBD) decreases. That is,
δ = (W / 2) × sin θ / OBD, and as a result, the following equation (2) is obtained.

Δn = 1/4 · sin {tan ^-1 (WL / OBD)} · (Ws / OBD) · W (2) where, WL; red and blue projection lenses 2R and 2B for green projection lens 2G Center distance parallel to the screen surface at the tip, Ws; 1/2 of the width of screen 3 (both are first
See figure).

Now, in the case of OBD = 780mm, WL = 125mm, Ws = 457mm (45 inch screen), W = 108mm, using the technology to shift the raster sensor by Δn ≒ 2.5mm and increase the projection distance as described above ing.

Further, the total length 1 of the red projection tube 1R and the blue projection tube 1B is made shorter by Δl than the green projection tube 1G. In general, since the overall length of the electromagnetic CRT is longer than that of the electrostatic CRT, it can be realized by using both CRTs as projection tubes.

Further, the brightness of the blue projection lens 2B is
R, Make it brighter than the brightness of the green projection lens 2G.

〔The invention's effect〕

According to the present invention, even in short throw optical system using an aspherical fluorescent screen or spherical phosphor screen projection tube, it is reduced to theta ₁ from theta ₂ as seen intensive angle in Figure 1 Therefore, not only excellent color uniformity but also excellent overall focus can be realized, and a bright and high-performance projection image display apparatus can be realized. Further, as shown in FIG. 2, even if the concentration angle is the same as before the projection distance is increased, at least the projection magnification for the red color can be increased, so that the screen lack does not occur.

Further, as shown in FIG. 3, in the case of a rear projection type image display apparatus using a mirror 4, the height H of the set 5 depends on the total length of the projection tube. Therefore, as described above, since the projection distances of the red and blue projection lenses 2R and 2B are increased, the usage is such that the total length of the projection tube is substantially increased by Δl, and the height is increased by ΔH. However, it is possible to shorten the total length of the red and blue projection tubes 1R and 1B by Δl by using an electrostatic cathode ray tube instead of an electromagnetic cathode ray tube. Can be realized.

[Brief description of the drawings]

FIG. 1 is a top view showing one embodiment of the present invention, FIG. 2 is a top view showing another embodiment of the present invention, and FIG. 3 is a rear view of a projection type image display device embodying the present invention. FIG. 4 is a schematic view of the projection tube viewed from the direction of arrow A in FIG. 1; FIG. 5 and FIG. 6 are conceptual diagrams each showing a raster shape projected on the projection tube fluorescent screen; 7 is a top view showing a conventional projection type image display device, FIG. 8 is a conceptual diagram showing an image on a fluorescent screen of a projection tube, FIG. 9 is a top view showing a conventional projection type image display device, FIG. FIG. 4 is a conceptual diagram showing an image on the fluorescent screen of the projection tube. Description of reference numerals 1R, 1G, 1B: red, green-blue projection tubes, 2R, 2G, 2B: projection lens, 3: screen, OBD: projection distance, θ ₁ , θ ₂ ...
… Concentration angle, 6B, 6G… Blue image and green image on the fluorescent screen of the projection tube, respectively 6R, 6′R, 6 ″ R… Red image on the fluorescent screen of the projection tube

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toru Numata 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Home Appliance Research Laboratory, Hitachi, Ltd. (72) Koji Hirata 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd.

Claims (8)

(57) [Claims] A projection tube provided for each of red, blue, and green; and a projection lens provided for each of the projection tubes, wherein an optical axis of each projection lens is at one intersection. To intersect, the red and blue corresponding projection tube and projection lens,
Arranged on both sides of the projection tube and the projection lens corresponding to the green color,
In a projection type image display device configured to project an image from each projection tube on the same screen through a respective projection lens, the light emission surfaces of the red and blue projection lenses are each a green corresponding projection lens. The projection lens corresponding to the red and blue is disposed so as to be located behind the light exit surface of the projection tube side, the projection distance from the projection lens corresponding to the red and blue to the screen from the projection lens corresponding to the green from the green. A projection-type image display device characterized in that the projection distance is longer than a projection distance to a screen. 2. A projection tube corresponding to each color of red, blue, and green, and a projection lens provided for each of the projection tubes, wherein an optical axis of each projection lens is at one intersection. To intersect, the red and blue corresponding projection tube and projection lens,
Arranged on both sides of the projection tube and the projection lens corresponding to the green color,
In a projection type image display device configured to project an image from each projection tube on the same screen through a respective projection lens, the projection tube corresponding to each color is viewed from the optical axis direction of the projection lens corresponding to red. When one end of the projection tube corresponding to the red overlaps behind one end of the projection tube corresponding to the green, so that the projection tube corresponding to each color is viewed from the optical axis direction of the projection lens corresponding to the blue. A projection type image display device, wherein the projection tubes corresponding to the respective colors are arranged such that one end of the projection tube corresponding to the blue color is hidden behind the other end of the projection tube corresponding to the green color. 3. A projection tube corresponding to each color of red, blue, and green, and a projection lens provided corresponding to each of the projection tubes, and an optical axis of each projection lens at one intersection. To intersect, the red and blue corresponding projection tube and projection lens,
Arranged on both sides of the projection tube and the projection lens corresponding to the green color,
In a projection type image display device configured to project an image from each projection tube on the same screen through a respective projection lens, the light emission surfaces of the red and blue projection lenses are each a green corresponding projection lens. The projection lens corresponding to the red and blue is disposed so as to be located behind the light exit surface of the projection tube side, the projection distance from the projection lens corresponding to the red and blue to the screen from the projection lens corresponding to the green from the green. A projection-type image display device, wherein the projection distance is longer than a projection distance to a screen, and the intersection is a position farther in a light traveling direction than a position where the screen is arranged. 4. A projection tube corresponding to each color of red, blue and green, and a projection lens provided corresponding to each of the projection tubes, wherein the optical axis of each projection lens is at one intersection. To intersect, the red and blue corresponding projection tube and projection lens,
Arranged on both sides of the projection tube and the projection lens corresponding to the green color,
In a projection type image display device configured to project an image from each projection tube on the same screen through a respective projection lens, the projection tube corresponding to each color is viewed from the optical axis direction of the projection lens corresponding to red. When one end of the projection tube corresponding to the red overlaps behind one end of the projection tube corresponding to the green, so that the projection tube corresponding to each color is viewed from the optical axis direction of the projection lens corresponding to the blue. The projection tubes corresponding to the respective colors are arranged such that one end of the projection tube corresponding to the blue is hidden behind the other end of the projection tube corresponding to the green, and the screen is arranged at the intersection. A projection-type image display device, wherein the projection-type image display device is located farther away in the light traveling direction than the position. 5. The image raster of each of the red and blue projection tubes has a width equal to the width (W) of the effective image area of the projection tube surface, and Assuming that the length dimension of the projection screen effective image area for red and blue corresponding to the lateral width from the width (W) dimension is ΔW, the projection distance from the red and blue corresponding projection lens to the screen, The difference (DELTA) L from the projection distance (OBD) from the projection lens corresponding to green to the said screen was set to (DELTA) L (OBD) X (2 (DELTA) W / W), The Claims 1,2,3 or 4 characterized by the above-mentioned. Projection image display device. 6. A center position of an image raster in each of the red and blue projection tubes is shifted from a center position of the surface of each projection tube by a dimension distance Δn given by the following equation. The projection type image display device according to claim 3. Δn = (1/4) sin {tan ^-1 (WL / OBD)} · W · Ws / OBD, where WL: the optical axis at the exit surface of the projection lens corresponding to red or blue, and the emission axis at the exit surface of the projection lens corresponding to green The distance between the optical axis, that is, the distance Ws: 1/2 of the width of the screen 7. The projection type image according to claim 1, wherein the total length of the projection tubes for red and blue is shorter than the total length of the projection tubes for green. Display device. 8. The projection lens corresponding to blue color, another red color,
5. The projection type image display device according to claim 1, further comprising a lens that is brighter than a green projection lens.