JP2002268010A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an image display device thin and to make the illuminance distribution on a screen uniform. SOLUTION: The image display device is equipped with a white light source 1, a reflector 2 which generates a virtual secondary light source, a color filter 3 which is arranged nearby the secondary light source and temporally generates the primary colors of light from the white light, a 1st condenser lens 10 which a light beam having passed through the color filter 3 passes through, a plane mirror 11 and a spherical mirror 12 which reflect the light beam having passed through the condenser lens 10, a DMD 8 on which the reflected light from the spherical mirror 12 is made incident, and a projection lens 14 on which the reflected light from the DMD 8 is made incident. In the optical path between the spherical mirror 12 and DMD 8, a 2nd capacitor lens 13 is arranged nearby the DMD 8 and the reflected light from the spherical mirror 12 is made incident on the 2nd condenser lens 13 from obliquely below and further made incident on the DMD 8 through this condenser lens 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display device, and more particularly, to an image display device having a feature in an optical system for projecting and displaying a color image on a screen.

[0002]

2. Description of the Related Art FIG.
It is a top view of the principal part showing the prior art of the projection type color image display device using a device (DMD: registered trademark of Texas Instruments, USA). This prior art is substantially the same as the image display device according to Japanese Patent No. 3121843 by the present applicant.

In FIG. 7, reference numeral 1 denotes a white light source, and this white light source 1 is arranged at one focal point of a reflector 2 formed by an elliptical mirror. Reference numeral 3 denotes a color filter disposed near the other focal point of the reflector 2, that is, a virtual secondary light source formed by the light condensing action of the reflector 2. As shown in FIG. 8, the color filter 3 has a ring zone portion of RED (R), GREEN (G), B
It is composed of transmission filters 3R, 3G, and 3B divided into three corresponding to the three primary colors of LUE (B). The color filter 3 is rotatable about a central axis 3C, and the rotation causes white light to be sequentially reflected in RED, GREEN,
The image is converted into each color of BLUE and output.

The light passing through the color filter 3 enters a condenser lens 5 via a pipe 4 in FIG. Here, the inner surface of the pipe 4 is a total reflection surface, and is used to make the distribution of light uniform. The condenser lens 5 is composed of a plurality of convex lenses. The light that has passed through the condenser lens 5 is reflected by a plane mirror 6 (or a concave cylinder mirror) as a first folding mirror, and is reflected again by a spherical mirror 7 as a second folding mirror to form a cover glass 8A. Through the reflecting surface of the DMD 8.

The DMD 8 arranges a large number of pixels having minute mirrors in a two-dimensional manner, individually controls the inclination of the minute mirrors by an electrostatic field effect of a memory element arranged corresponding to each pixel, and reflects reflected light. The on / off state is created by changing the reflection angle of the light. FIG.
FIG. 4 is a diagram showing an operation state of a micro mirror provided in each pixel of the DMD 8; In FIG. 9, 8a to 8e are micro mirrors of each pixel, and 9 is a projection lens shown schematically. In this figure, the micro mirrors 8c and 8e are on, and the micro mirrors 8a, 8b and 8d are off.

Light rays reflected by the micro mirrors 8c and 8e in the on state enter the projection lens 9 to form an image on a screen (not shown), and are reflected by the micro mirrors 8a, 8b and 8d in the off state. The light does not enter the projection lens 9. Note that the micromirror 8 in the ON state
The inclination angle of c and 8e is about 10 degrees with respect to the horizontal state of the micro mirrors 8c and 8e. DMD8 is
Compared to a liquid crystal display panel using a polarizing plate, it has features such as higher light use efficiency, higher heat resistance, and faster response speed. The light reflected by the DMD 8 is magnified by a projection lens 9 composed of a plurality of lenses and forms an image on an external screen to display an image.

In this prior art, the color filter 3
A specific method for projecting and displaying a color image on a screen using the DMD 8 and the DMD 8 is as follows. For example,
If you want to display a part of an image in red, use DMD8
The micromirror of the pixel at the predetermined address is turned on, and the light beam passing through the red transmission filter 3R is reflected by the micromirror in the on state and is incident on the projection lens 9. The same applies in principle to the case of displaying green and blue, and the light passing through the transmission filters 3G and 3B is reflected by the on-state micromirror at a predetermined address and incident on the projection lens 9. By performing these operations in chronological order and at high speed, it is possible to project and display an image of three primary colors of light and an arbitrary color obtained by mixing the three primary colors on a screen.

[0008]

In the prior art shown in FIG. 7, the light reflected by the spherical mirror 7 is focused on the entrance pupil of the projection lens 9 via the DMD 8. For this reason, in order to make the reflected light from the spherical mirror 7 incident on the DMD 8 without leakage, the effective diameter along the reflecting surface of the spherical mirror 7 must be increased, which reduces the height of the image display device. (That is, making the entire device thinner). Therefore, achieving a thinner image display device is one solution.

FIG. 10 is a diagram showing the configuration of the optical system (spherical mirror 7, DMD 8, and projection lens 9) after the spherical mirror 7 in the prior art of FIG. is there. The reflected light of the spherical mirror 7 is
In order to be reflected by the micro mirror in the ON state of the DMD 8 and made incident on the projection lens 9, as shown in FIG.
It is necessary to arrange the spherical mirror 7 so that the reflected light from the spherical mirror 7 enters the DMD 8 from a diagonally lower angle with a relatively large incident angle.

However, as a result, as shown in FIG.
On the reflection surface of the DMD 8, the illuminance distribution becomes non-uniform as a whole, and the upper side becomes bright and the lower side becomes dark. FIG.
Reference numeral 1 denotes an illuminance distribution diagram in which positions of the same illuminance on the reflection surface of the DMD 8 are connected by illuminance contour lines 8f, and reference numeral 8g denotes a reference range in the reflection surface. According to FIG. 11, the rectangle formed by the illuminance contour lines 8f is distorted outside the reference range 8g.

When the illuminance distribution on the reflection surface of the DMD 8 becomes non-uniform as described above, the illuminance distribution of the image on the screen becomes as shown in FIG. In FIG. 12A,
The horizontal axis is the position on the horizontal line H and the vertical line V set on the screen (aspect ratio 3: 4). FIG.
As shown in (b), the horizontal line H on the screen
_U (near the top edge of the screen), H ₀ (center of the screen), H _D (near the bottom edge of the screen), and each position on the vertical line V are shown on a ± 1000 scale centered on 0. In FIG. 12A, the vertical axis indicates the relative value of the illuminance in the range of 0 to 1000.

From FIGS. 12A and 12B, it can be seen that there is a large difference in illuminance depending on the height even on the screen, and the brightness along the vertical direction on the screen is not uniform. The illuminance is also unbalanced in the horizontal direction of the screen. Therefore, uniformizing the illuminance of the projected image on the screen is another problem to be solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image display device which can be made thinner by improving the configuration of an optical system and making the entire device thinner. Another object of the present invention is to provide an image display device in which the illuminance of a projected image on a screen is substantially uniform.

[0014]

In order to solve the above-mentioned problems, an invention according to claim 1 includes a white light source, a reflector that collects light from the white light source to form a virtual secondary light source, A color filter that is arranged near the secondary light source and creates the three primary colors of light from white light with time, a first condenser lens through which light rays passing through the color filter pass;
A reflecting mirror that reflects the light beam that has passed through the first condenser lens; a light beam that is reflected by the reflecting mirror is incident on the mirror; A reflection display means such as a DMD that forms an on / off state by changing an emission angle, a projection lens that receives reflected light from a micromirror of a pixel in an on state, and enlarges and projects the incident light; And a second condenser lens is arranged on the optical path between the return mirror and the reflection display means in proximity to the reflection display means, and the reflected light from the return mirror is transmitted to the second reflection lens. From the diagonally lower part of the condenser lens through the condenser lens to the reflection display means, and the second condenser lens is It is intended to also operate as part of a projection lens for expanding and displaying a reflected light from the morphism display means.

[0015] According to a second aspect of the present invention, the reflecting mirror includes a first reflecting mirror that reflects light rays passing through the first condenser lens, and a second reflecting mirror that reflects light reflected by the reflecting mirror. And the second folding mirror may be a flat mirror, and the second folding mirror may be a concave spherical mirror.

Further, as described in claim 3, the first folding mirror is a concave cylinder mirror, and the second folding mirror is a second mirror.
May be a concave spherical mirror.

In the second and third aspects, the folding mirror is constituted by two mirrors. However, as described in the fourth aspect, the folding mirror is constituted by a single concave spherical mirror. The light that has passed through one condenser lens may be reflected by a single turning mirror and incident on the second condenser lens.

Here, as described in claim 5, it is desirable that the second condenser lens is formed in a convex lens shape and the surface thereof is opposed to the folded mirror side.

Further, a pipe or a rod lens whose inner surface is a total reflection surface is disposed between the color filter and the first condenser lens.
If a fly-eye lens is arranged between the first condenser lens and the folding mirror, the illuminance distribution on the screen can be made more uniform.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view showing a configuration of a main part of this embodiment. As described above, 1 is a white light source, and this white light source 1 is arranged at one focal point of a reflector 2 formed of an elliptical mirror. Reference numeral 3 denotes a color filter arranged at the other focal point of the reflector 2, which is provided with transmission filters 3R, 3G, and 3B of RED, GREEN, and BLUE as shown in FIG.

In front of the color filter 3, there is disposed a pipe 4 whose inner surface is a total reflection surface. This pipe 4 is for making the light distribution uniform, and is shown in FIG.
As shown in (c), it may be replaced by a rod lens 4A or a fly-eye lens 4B. A first condenser lens 10 including a plurality of convex lenses is disposed in front of the pipe 4.

At a position ahead of the optical axis L2 in front of the condenser lens 10, a plane mirror 11 as a first folding mirror is arranged. Here, the plane mirror 11
Alternatively, a concave cylinder mirror may be used. Along the optical axis L1, the color filter 3, the pipe 4,
The light that has passed through the first condenser lens 10 is reflected by a plane mirror 11 and is incident on and reflected by a concave spherical mirror 12 as a second folding mirror.

The position of the spherical mirror 12 as viewed from above is closer to the projection lens 14 than in FIG. 7 as is apparent from the comparison between FIG. Is getting longer. Further, when viewed from the side, the spherical mirror 12 is disposed below the optical axis L2 as in the related art, but as is clear from the comparison between FIG. 3A and FIG.
The effective diameter of the spherical mirror 12 of the present embodiment is smaller than the effective diameter of the conventional spherical mirror 7, and the lower end of the spherical mirror 12 is located above the lower end of the spherical mirror 7.

Referring back to FIG. 1A, the spherical mirror 12
Is reflected by the second condenser lens 13 disposed at a position earlier than the optical axis L1. The condenser lens 13 is a convex lens having a convex surface facing the spherical mirror 12, and its curvature is designed so that halation due to surface reflection is reduced. A cover glass 8A is provided on the plane opposite to the condenser lens 13.
And the DMD 8 is arranged in close proximity to it. In addition, DMD
Reference numeral 8 denotes a reflection display unit according to the present invention. The light reflected by the on-state micromirrors in each pixel of the DMD 8 enters the projection lens 14 along the optical axis L2.

The function of the DMD 8 is the same as that of the prior art. A large number of pixels having micromirrors are two-dimensionally arranged, and the tilt of the micromirrors is individually controlled by the electrostatic field effect of a memory element corresponding to each pixel to reflect the pixels. The on-state and off-state are realized by changing the light reflection angle.

The projection lens 14 is composed of a plurality of lenses, the specific structure of which is slightly different from that of the projection lens 9 of FIG. 7, but the function and operation are substantially the same as those of the projection lens 9. In the above configuration, the optical axis L1 constituted by the white light source 1, the reflector 2, the color filter 3, the pipe 4, and the first condenser lens 10, and the light constituted by the DMD 8, the second condenser lens 13, and the projection lens 14. The axis L2 is substantially orthogonal to the axis L2 when viewed from above.

FIG. 2 is a perspective view showing a main part of the embodiment of FIG. Reference numeral 4a denotes an emission surface of the pipe 4.

In this embodiment, the folding mirror that reflects the light beam that has passed through the first condenser lens 10 is composed of a plane mirror 11 as a first folding mirror and a spherical mirror 12 as a second folding mirror. However, a single folding mirror may be used. That is, when the white light source 1, the reflector 2, the color filter 3, the pipe 4, and the first condenser lens 10 in FIG. 1A are moved to symmetric positions with respect to the plane mirror 11, the result is as shown in FIG.

According to the embodiment shown in FIG. 6, the plane mirror 11 becomes unnecessary, and only the spherical mirror 12 is required as the folding mirror. Therefore, when the arrangement of each optical component shown in FIG.
6, the number of optical components can be reduced as compared with the embodiment of FIG. 1 by removing the first folding mirror (the plane mirror 11 or the cylinder mirror). In the embodiment of FIG. 6, a rod lens 4A and a fly-eye lens 4B can be used instead of the pipe 4.

Next, FIG. 3A is a diagram showing the configuration of the optical system after the spherical mirror 12 in the embodiment of FIG. 1 and the path of the light beam reflected by the spherical mirror 12. In the present embodiment, the second condenser lens 13 is provided, and the reflected light of the spherical mirror 12 is made to enter from obliquely below the condenser lens 13. Then, due to the refraction effect of the condenser lens 13, as shown on the left side of FIG.
The reflected light from the condenser lens 13 is more than the incident angle θ _{1 of the} light entering the condenser lens 13,
Towards the incident angle theta ₂ of the incident light is increased to.

In the prior art shown on the right side of FIG.
And the angle of incidence of light entering the DMD 8 from the spherical mirror 7
θ₂′, And the second embodiment of the present embodiment shown on the left side of FIG.
If the refractive index of the condenser lens 13 is n, then n · sin θ₂= Sinθ₂’Holds, θ₂Is θ₂Smaller than ’
You. Also, as described above, θ ₁Is θ₂Even smaller. Book
Comparing the embodiment with the prior art,₁<Θ₂<
θ₂′, Through the DMD 8 from the spherical mirror 12.
And the path of the light incident on the projection lens 14 is smaller than that of the prior art.
Will also approach horizontal.

That is, in the prior art, the effective diameter of the spherical mirror 7 is increased due to the large incident angle θ ₂ ′, and the position of the lower end must be lower than in the present embodiment. In the form, the spherical mirror 12 to the DMD 8
Even if the distance to the reflecting surface is longer than in the prior art, the effective diameter of the spherical mirror 12 can be reduced and the position of the lower end can be higher than in the prior art, resulting in a thinner image display device. be able to.

FIG. 4 is a diagram showing the distribution of light rays on the reflecting surface of the DMD 8 in the present embodiment, and FIG. 5 is a diagram showing the illuminance distribution on the screen, each of which is related to the prior art.
1 and FIG. With the arrangement structure of the spherical mirror 12 and the second condenser lens 13 as shown in FIG. 3, the light incident on the DMD 8 from the spherical mirror 12 slightly obliquely below the DMD 8 can be made closer to the horizontal light. As shown in FIG. 4, the illuminance distribution on the reflection surface has a characteristic in which the deviation in the vertical direction has been corrected as compared with the related art (FIG. 11). That is, the center of the illuminance distribution is closer to the center of the reflection surface of the DMD 8, and the illuminance contour 8f around the reference range 8g is closer to a rectangle than before. For this reason, as for the illuminance distribution on the screen, as shown in FIGS. 5A and 5B, the uniformity in the up, down, left, and right directions is improved, so that an illuminance distribution close to a substantially rectangular shape is obtained. It will be located almost in the center.

[0034]

As described above, according to the present invention, it is possible to reduce the effective diameter of the folding mirror for allowing the light from the white light source to enter the reflective display means such as the DMD, and thereby the entire image display device can be realized. Can be made thinner. For this reason, it is possible to reduce the size and weight of the device, improve portability, and improve manufacturing and transportation costs. Also, the illuminance distribution on the screen is made uniform, and the quality of the projected image can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a main part showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of the embodiment of FIG.

FIG. 3A is a diagram showing a configuration of an optical system after the spherical mirror in FIG. 1 and a path of a light beam reflected by the spherical mirror, and FIG. 3B is an embodiment of the present invention. FIG. 6 is a side view showing the position of a spherical mirror in the related art in comparison with that of the related art.

FIG. 4 is a diagram showing an illuminance distribution on a reflection surface of a DMD in the embodiment of FIG. 1;

FIG. 5 is a diagram showing an illuminance distribution on a screen in the embodiment of FIG. 1;

FIG. 6 is a plan view of a main part showing another embodiment of the present invention.

FIG. 7 is a plan view of a main part showing a conventional technique.

FIG. 8 is an explanatory diagram of a color filter.

FIG. 9 is a diagram illustrating an operation state of a micro mirror provided in each pixel of the DMD.

10 is a diagram illustrating a configuration of an optical system after a spherical mirror and a path of a light beam reflected by the spherical mirror in the related art of FIG. 7;

11 is a diagram showing an illuminance distribution on a reflection surface of a DMD in the conventional technique of FIG. 7;

FIG. 12 is a diagram showing an illuminance distribution on a screen in the prior art of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 White light source 2 Reflector 3 Color filter 3C Rotating axis 3R, 3G, 3B Transmission filter 4 Pipe 4a Outgoing surface 4A Rod lens 4B Fly-eye lens 8 DMD 8a-8e Micromirror 8f Illuminance contour 8g Reference range on reflective surface 8A Cover Glass 10 First condenser lens 11 Planar mirror (first folding mirror) 12 Spherical mirror (second folding mirror) 13 Second condenser lens 14 Projection lens L1, L2 Optical axis

Claims (8)

[Claims] 1. A white light source, a reflector for condensing a light beam from the white light source to form a virtual secondary light source, and a three-dimensional primary color of light from white light disposed over the secondary light source with time , A first condenser lens through which the light passing through the color filter passes, a folding mirror that reflects the light passing through the first condenser lens, and the light reflected by the folding mirror enter.
And reflection display means for making an on / off state by changing the inclination of the micromirrors of a large number of pixels arranged two-dimensionally to change the emission angle of the reflected light, and micromirrors of the pixels in the on state. And a projection lens for projecting the incident light by enlarging and projecting the incident light, wherein the second condenser lens is provided on an optical path between the return mirror and the reflective display means. It is arranged close to the reflection display means, and the reflected light from the folding mirror is made to enter the reflection display means via the condenser lens from obliquely below the second condenser lens.
An image display device, wherein the condenser lens is also operated as a part of a projection lens for enlarging and displaying reflected light from the reflection display means. 2. The image display device according to claim 1, wherein the folding mirror reflects a light beam passing through the first condenser lens, and a first reflecting mirror reflecting light reflected by the folding mirror. An image display, comprising: a second folding mirror for entering the second condenser lens; the first folding mirror being a plane mirror; and the second folding mirror being a concave spherical mirror. apparatus. 3. The image display device according to claim 1, wherein the folding mirror reflects a light beam passing through the first condenser lens, and a light reflected by the folding mirror. And a second folding mirror that is incident on the second condenser lens, wherein the first folding mirror is a concave cylinder mirror, and the second folding mirror is a concave spherical mirror. Image display device. 4. The image display device according to claim 1, wherein the folding mirror is a single concave spherical mirror. 5. The image display device according to claim 1, wherein the surface of the second condenser lens facing the folding mirror has a convex shape. 6. The image display device according to claim 1, wherein a pipe whose inner surface is a total reflection surface is arranged between the color filter and the first condenser lens. Characteristic image display device. 7. The image display device according to claim 1, wherein a rod lens is arranged between the color filter and the first condenser lens. 8. The image display device according to claim 1, wherein a fly-eye lens is arranged between the first condenser lens and the folding mirror. .