JP3151734B2 - Light source unit and display device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive liquid crystal display device in which light emitted from a light source efficiently illuminates a surface to be illuminated, and the angle of light incident on the surface to be illuminated is small, for example, a light valve. The present invention relates to a light source unit suitable for illuminating an optical image formed thereon and a display device using the same .

[0002]

2. Description of the Related Art Conventionally, various types of illumination devices and display devices have been developed as devices using an illumination optical system. For example, as a display device, an optical image formed according to a video signal as a change in optical characteristics on a light valve,
A direct-view display device that irradiates with illumination light from an illumination optical system including a light source and directly looks at the optical image, or a projection display device that projects an optical image on a screen by a projection lens has been developed. In recent years, many liquid crystal display devices using a transmissive liquid crystal display element have been proposed as light valves used in such display devices, and furthermore, such liquid crystal display devices themselves have been reduced in size and have improved performance such as resolution. The size and performance of display devices using this type of liquid crystal display device have been rapidly increasing.

On the other hand, as an illumination optical system used in the display device or the illumination device as described above, a technique has been developed in which light emitted from a light source is efficiently collected on the surface to be illuminated, thereby illuminating the surface to be illuminated brightly. Is also progressing. As an illumination optical system used in a liquid crystal display device or the like using a conventionally proposed liquid crystal display element as a light valve, for example, "Flat panel display '91"; Nikkei BP (issued in 1990), page 202 As shown in FIG. 15, there is a configuration using a concave mirror having a function of collecting light emitted from a light source in the direction of a liquid crystal display element, that is, a liquid crystal panel, which is a surface to be irradiated. However, along with the miniaturization and high performance of the display device or the illumination device as described above, further miniaturization and high performance of the illumination optical system used therein are desired.

[0004]

One of the conditions for reducing the size and improving the performance of an illumination optical system is to efficiently collect light emitted from a light source on a surface to be irradiated. That is, the ratio of the energy of the light irradiated on the irradiation surface to the energy of all the light emitted by the light source (hereinafter, referred to as the
It is important to illuminate the irradiated surface brightly by increasing the light utilization efficiency). Generally, in an illumination optical system, as a method of brightening an irradiated surface having a certain size placed at a certain distance, in addition to increasing the light use efficiency, a high output of the light source itself of the illumination optical system is used. Can be considered. In recent years, there has been a lamp using a light source such as a metal halide, xenon, or halogen as a light source used for the above-described lighting device or display device, and the performance such as brightness and the life of such a lamp have been improved. . However, when the output is further increased, the life of the lamp due to heat generation and the life and size of a device using the lamp are affected, so that it is difficult to increase the output of the lamp. For this reason, it is necessary to increase the light use efficiency of the illumination optical system as much as possible to brighten the irradiated surface.

Another condition of a high-performance illumination optical system is a reduction in luminance unevenness on a surface to be illuminated. That is,
For example, in a liquid crystal display device or the like, luminance unevenness on an irradiated surface caused by an illumination optical system used in the device causes image unevenness as it is, making it impossible to obtain a high-performance display device. Therefore, there is a need for an illumination optical system having less luminance unevenness.

On the other hand, another condition for the downsizing and high performance of the illumination optical system is to optimize the angle at which the light emitted from the light source enters the surface to be irradiated. That is, for example, when the surface to be illuminated is the liquid crystal display device, the characteristics of the liquid crystal are affected by the angle of the light incident on the liquid crystal. In the case where the illumination optical system reflects or separates light from a dichroic mirror or the like other than liquid crystal, or irradiates an optical component such as a microlens or a fiber, the characteristics of each component are determined by the angle of light incident on the component. Therefore, it is necessary to optimize the incident angle of light according to each component and specification, and in many cases, it is better that the light is incident at the same angle as much as possible.

As described above, in order to reduce the size and performance of the illumination optical system, it is necessary to increase the light use efficiency, to reduce the uneven brightness on the illuminated surface, and to reduce the angle of incidence of light on the illuminated surface. It is a condition that they are aligned and that the entire illumination optical system is small.

In general, in the illumination optical system, in order to increase the light use efficiency, it is conceivable to reduce the size of the light source and to condense the light emitted from the light source on a surface to be illuminated by a lens or the like.

To reduce the size of the light source is to bring the light source closer to a point light source. As a method for reducing the size of the light source, the light source itself, that is, the light source itself is reduced in size, and the size of the light source is not changed. There are two methods of relatively reducing the size of the light source by increasing the size of the light source unit used. However, when the size of the light source itself is reduced, if the output is the same, there is a problem that the life of the light source is shortened due to heat generation or the like, and it is difficult to significantly reduce the size. In addition, when the entire light source unit using the light source is enlarged to make the light source relatively small, the components of the illumination optical system and the surface to be illuminated become relatively large. The system and the display device cannot be obtained. For this reason, the light source unit
It also is a limit to increase relatively Tsu bets.

On the other hand, when light emitted from a light source is focused on a surface to be illuminated by a lens or the like in order to increase the light use efficiency, the angle of incidence of the light on the surface to be illuminated is tight as described later. Or uneven brightness on the surface to be illuminated. For this reason, conventionally, there is a limit in condensing light on a surface to be irradiated with a lens or the like.

Accordingly, it is an object of the present invention, such conventional problems to solve, high light utilization efficiency from the light source, and formed by using the same compact, high-performance light source unit and a display
It is to provide a device .

[0012]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a first concave mirror on one side and a second concave mirror on the other side with a light source interposed therebetween on the same optical axis. a light source unit formed by sequences first concave mirror, first the reflecting surface on the optical axis, form part of an ellipsoid having a second focal point, of these two focal points On the reflective surface side of
A position of the first focus is set substantially at a position of the light source;
The second concave mirror is disposed such that its reflective surface forms a part of a spherical surface whose center point is the position of the light source, and the reflective surface faces the reflective surface of the first concave mirror. Radius of the first concave mirror from the position of the first focal point to the second focal point
It is set smaller than the distance position to the, and the second
The concave mirror directly emits light from the light source on the optical axis.
Toward the first concave mirror, reflected by the first concave mirror
While passing light and condensing it at the second focal point,
The light emitted from the light source is directly directed to the second concave mirror,
Reflected by the second concave mirror and then reflected by the first concave mirror
Opening through which the transmitted light is passed and collected at the second focal point
Is provided .

[0013]

Next, the operation of the present invention will be described. FIG. 1 shows a principle sectional view of a light source unit and a display device using the same according to the present invention.

FIG. 1A shows a light source unit according to the present invention.
Shows a principle cross-sectional view of the bets, light emitted from the light source 1 is either reflected by the reflecting mirror is a first concave mirror 2, or a part of the light emitted from the light source 1 in the first concave mirror 2 The light goes toward the condenser lens group 4 without being reflected. Some of these lights are the first light provided as shown in the figure.
The second concave mirror 3 as a means for changing the direction of light not reflected by the concave mirror 2 to reflect the first concave mirror 2
And the other light is directed toward the condenser lens group 4 without being reflected by the second concave mirror 3. Finally, the light that has passed through the second concave mirror 3 also irradiates the irradiated surface 5 after passing through the condenser lens group 4. In the light source unit according to the present invention, the function of the second concave mirror 3 is effective even when the condenser lens group 4 is not provided.

FIG. 1B shows a light source unit according to the present invention.
Shows a principle cross-sectional view of a direct view type display apparatus using a preparative,
An illumination optical system as shown in FIG. 1A illuminates a light valve 6 such as a liquid crystal display element. The light valve 6 has a function of forming an optical image in accordance with a video signal as a change in optical characteristics, and the present apparatus directly views the image of the light valve 6.

FIG. 1C shows a light source according to the present invention.
FIG. 3 is a sectional view showing the principle of a projection type display device using a unit, in which an image formed by a light valve 6 shown in FIG. 1B is enlarged by a projection lens 8 and projected on a screen 9. .

Next, the specific operation of the present invention will be described.
explain. As described above, it is effective to reduce the size of the light source to reduce the size and performance of the light source unit . This will be described with reference to FIG.

FIG. 2 schematically shows an illumination optical system other than the light source unit as a single thin lens. 2A and 2B show a case where the light source is a point light source, and FIGS. 2C and 2D show a light source having a certain size as a linear light source. It is.

As shown in FIG. 2A, when the light source is a point light source 11, of the light emitted from the point light source 11, the light incident on the thin lens 10 is reflected by the thin lens 10. The light can be completely afocal light, so that at least the light that passes through at least the thin lens 10 and is incident on the irradiated surface 5 is perpendicularly incident on the irradiated surface 5. FIG. 2B shows a case where the point light source 11 is separated from the thin lens 10 from the state shown in FIG. As shown in this figure, when the point light source 11 is separated from the thin lens 10, the light emitted from the point light source 11
Will be condensed at a point passing through. In this case, at least all the light incident on the thin lens 10 can be collected on the irradiated surface 5, but as shown in the figure, the state of the light is shifted from the state shown in FIG. The light is incident on the surface 5 at an angle θ. In the case shown in FIG. 2A, θ = 0. Therefore, when it is desired to set the angle θ of the light incident on the irradiated surface 5 to 0, FIG.
Is desired.

On the other hand, FIG. 2C shows a case where the light source of FIG. 2A has a certain length. The line light source 12 shown in this figure is considered as a collection of point light sources. Assuming that the light emitted from the central point light source of the line light source 12 is in the state shown in FIG. 2A, the light path shown by the broken line in FIG. The light of the point light source at the farthest tip is in the state shown in FIG. 2B, and has the optical path shown by the solid line in FIG. 2C. Further, the light of the point light source at the end of the line light source 12 closest to the thin lens 10 has an optical path indicated by a chain line in FIG. FIG. 2D shows the line light source 12 shown in FIG.
Is separated from the thin lens (10). As is clear from these figures, when the light source has a certain size, light from various point light sources enters the surface to be irradiated. Therefore, if the total energy of the light emitted from the light source is equal, the light from the light source is diffused and emitted due to the enlargement of the light source. As a result, the light use efficiency and the incident angle of the light are deteriorated. Will do.

Next, this is further described in the actual light source unit.
The description will be made by using a concave mirror as an example. FIG. 3 shows a light reflection state of a parabolic mirror having a parabolic cross section as a concave mirror.

FIG. 3A shows a case where the light source is a point light source 11. As shown in the figure, when the point light source 11 is placed at the focal position of the parabolic mirror 13, the light emitted from the point light source 11 and reflected by the parabolic mirror 13 is reflected at the center of the parabolic mirror 13. The axis travels parallel to the optical axis. Therefore, the light source unit is equivalent to the state shown in FIG.

FIG. 3B shows that the light source is a linear light source 12.
In this case, as shown in the figure, the central point of the line light source 12 is arranged so as to be at the focal position of the parabolic mirror 13, and the light emitted from the central point light source of the line light source 12 Is
The optical path is indicated by a broken line in FIG. In contrast,
The light from the point light sources at both ends of the linear light source 12 passes through another optical path from the light emitted from the central point light source, and thus has a certain angle ψ from one point on the reflecting surface of the parabolic mirror 13. A bundle of light rays, that is, a luminous flux comes out. Therefore, FIG. 3B is a light source unit equivalent to FIG. 2C.

From the above, in a light source that emits substantially the same light energy, a light source that is as small as possible, that is, a light source that is closer to a point light source is advantageous in terms of light use efficiency and light incident angle on a surface to be irradiated. is there.

On the other hand, as described above, in order to reduce the size of the light source, there is a method of relatively reducing the size of the light source by expanding the system using the light source, in addition to reducing the size of the light source itself. As described above, miniaturization of the light source itself is difficult due to problems such as a shortened life of the light source. Therefore, the following describes how to relatively reduce the size of the light source.

FIG. 4 shows a case where the size of the light source is not changed and the parabolic mirror 13 is enlarged as an optical system, in comparison with a case where the size is not so. As shown in FIG. 4B, the illumination optical system such as the parabolic mirror 13 including the surface to be illuminated 5 is enlarged as compared with FIG.
The angle の of the luminous flux from one point on the three reflecting surfaces is reduced, and the light reflected by the enlarged parabolic mirror 13 is incident on the enlarged irradiated surface 5 at a small angle and the light use efficiency is improved. . However, there is a problem that the size reduction cannot be achieved by expanding the entire system.

Therefore, it is advantageous to reduce the size of the light source in terms of light use efficiency and the angle of incidence of light on the surface to be irradiated. However, the life of the light source is shortened, or the entire light source unit is enlarged. Problem, the light source unit and
It is difficult to achieve a small and high-performance display device using this .

On the other hand, when the light from the light source is condensed on the surface to be irradiated by a lens or the like in order to increase the light use efficiency while keeping the size of the light source unchanged, This is equivalent to the relationship shown in FIG. 2B or FIG. 2D, and the angle of incidence of light on the irradiated surface 5 is also deteriorated.

In general, in a light source and an optical system such as a concave mirror and a lens, in order to collect a large amount of light on the small irradiated surface 5, an image of the light source is preferably formed near the irradiated surface 5. At this time, the light use efficiency becomes almost maximum. However, in this case, as shown in FIG. 5B, the angle of incidence on the irradiated surface 5 becomes larger than in the case of FIG. 5A where the image of the light source is not formed near the irradiated surface 5. Would.

Further, when the image of the light source is formed in the vicinity of the surface to be illuminated according to the size of the surface to be illuminated, if the light source itself has uneven brightness or shadow, The unevenness is reflected on the surface to be irradiated as it is, resulting in uneven brightness on the surface to be irradiated, which is not preferable.

As described above, in the combination of a single concave mirror and a lens as a conventional light source unit, if the light utilization factor is increased, the angle of incidence of light on the surface to be illuminated becomes greater, Brightness unevenness tends to increase, and if you try to correct it, the light source unit
In addition, the size of the entire display device using the same has been increased, and there has been a limit to downsizing and higher performance.

In an illumination optical system combining a single concave mirror and a lens, there are roughly two types of light: a light emitted from a light source, reflected by a concave mirror, and then directed to a surface to be irradiated, and light not reflected by the concave mirror. FIG. 6 shows this state.

In the configuration shown in FIG. 6, the concave mirror 14
Even when most of the light reflected by the light source is incident on the surface to be irradiated 5, the light emitted from the light source 1 and not reflected by the concave mirror 14 (hereinafter, referred to as direct light) is directly directed to the surface to be irradiated 5. Only a part of the directly incident light 15 shown in FIG. 6 is incident on the surface 5 to be irradiated, and therefore, most of the direct light, particularly when the surface 5 to be irradiated is smaller than the concave mirror 14. This means that the portion is not used for irradiating the irradiated surface 5.

In order to reflect the direct light with a concave mirror or the like,
If the concave mirror is enlarged or bent in the direction that covers the light source, the angle of incidence of light on the surface to be illuminated becomes large as described above, and the overall size becomes large.
A high-performance light source unit cannot be obtained.

Therefore, in the present invention, the direct light is incident on the irradiated surface without making the incident angle of the light on the irradiated surface tight, thereby improving the light use efficiency. FIG. 7 shows a state of reflection of light by the second concave mirror 3 in the light source unit of the present invention.

The first concave mirror 2 shown in FIG. 7 has the function of causing most of the light reflected by the first concave mirror 2 to be incident on the surface 5 to be illuminated. In the configuration as shown in FIG.
A part of the direct light that has not been reflected by the second concave mirror 3 has an effect of returning to the direction of the light source 1 again by being reflected by the second concave mirror 3. Therefore, the light reflected by the second concave mirror 3, Ri Do that again emitted from the light source 1 to return almost to the light source 1 again, which also is reflected by the first concave mirror 2 irradiates
The light is incident on the surface 5. As a result, the energy of the light emitted from the light source 1 and reflected by the first concave mirror 2 increases, and the light use efficiency can be increased. At this time, since the configuration other than the second concave mirror 3 is not changed, only the energy of the light is increased without changing the state of the light incident on the irradiation surface 5, and the light incident on the irradiation surface 5 is not changed. The angle hardly changes.

Therefore, according to the present invention, it is possible to increase the light use efficiency without deteriorating the angle of light incident on the surface to be illuminated as compared with the related art, and conversely, to make the light use efficiency equal to that of the related art. For example, the angle of light incident on the surface to be illuminated can be reduced by reducing the reflection surface of the concave mirror, and this is effective for downsizing and high performance of a light source unit and a display device using the same .

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 8 is a sectional view showing a first embodiment of the light source unit according to the present invention . 8, the light source 1 is a lamp using, for example, metal halide, xenon, halogen, etc., 18 is an ellipsoidal mirror corresponding to the first concave mirror 2, and 16 is the elliptical mirror in FIG. 2 is a spherical mirror corresponding to the concave mirror 3, and 5 is an irradiated surface.

In the figure, a light source 1 is a vertex of an ellipsoidal mirror 18.
The ellipse on the point side is located near the first focal point position, and thereby the light
Ellipse first focal position on the vertex side of ellipsoidal mirror 18 in source 1
Light emitted from the vicinity and reflected by the ellipsoidal mirror 18 is
The focal point on the opposite side to the focal point where the light source 1 of the elliptical mirror 18 is provided.
The light is focused near a certain elliptical second focal point 19. Meanwhile, the light source
1 and the spherical mirror (the
The light incident on the second concave mirror 16 is deflected by the spherical mirror 16.
Is emitted, returns to the direction of the light source 1 again, passes through the light source 1,
The light is reflected by the circular mirror 18 and is therefore close to the elliptical second focal point 19.
It is collected nearby. As a result, conventional direct light
Irradiation of the light that has not contributed to the irradiation of the surface 5 to the irradiated surface 5
This allows the use of light with high light utilization efficiency
A source unit can be obtained. Also, in this embodiment,
In addition, as is apparent from FIG.
Position where the second focal point 19 is farther from the light source 1 than the spherical mirror 16
Therefore, the radius of the spherical mirror 16 is
The position of the ellipse first focal point (that is, the position of the light source 1)
It is smaller than the distance to the position of the two focal points 19.

FIG. 9 shows the spherical mirror (second concave mirror) 16.
It is a perspective view which shows an example. Spherical mirror 16 shown in FIG.
Is Propelled by one circular exit window 17 which passes light, and the light reflected by the ellipsoidal mirror 18 is emitted from the light source <br/> 1, reflected by the spherical mirror 16 is emitted from the light source 1 Pass unreachable light (direct light). For example , the portion corresponding to the exit window (opening) 17 of the second concave mirror according to the present invention, such as the spherical mirror 16 of this example, is not limited to a circle as shown in FIG. It may have a shape
No.

[0041]

FIG . 10 is an explanatory diagram in the case where a condenser lens group 4 is provided between the light source 1 and the irradiated surface 5. The condensing lens group 4 in FIG. 10 has the function of collecting the light condensed by the elliptical mirror 18 and the spherical mirror 16 in the vicinity of the elliptical second focal point 19 on the irradiated surface 5 with a good angle. Thus, the light incident angle on the irradiated surface 5 is corrected, and the light source unit has good light use efficiency and a small light incident angle (θ in FIG. 4). Further, since the condensing lens group 4 has a configuration in which at least one surface is an aspherical surface, the aspherical surface can have an action of correcting light unevenness such as uneven brightness on the irradiated surface 5. Even when the light use efficiency is increased, it is possible to obtain a light source unit with good performance with less light unevenness.

FIG . 11 shows another example of the spherical mirror 16. The spherical mirror 16 shown in FIG.
Is a structure in which a hole corresponding to the emission window 17 of the spherical mirror 16 is not opened. The spherical mirror 16 shown in FIG. 11 is, for example, manufactured in a hemispherical hollow shape using glass, and then forms a reflective surface by depositing a film such as aluminum on the inside . By vapor-depositing only on the reflection surface 20, a non-vapor-deposited portion is used as the transmission surface 21 through which light is transmitted. This has the same function as the exit window 17 shown in FIG. 9 and eliminates the need to perform operations such as making a hole in the spherical mirror 16. Further, the size of the transmission surface 21 corresponding to the exit window for light is reduced by the above-mentioned hollow hemisphere. It is possible to adjust without reshaping the glass etc.,
The brightness of the irradiated surface 5 and the light incident angle can be adjusted so as to be suitable for a system using the present spherical mirror 16.

[0044]

FIG . 12 shows a light source unit according to a second embodiment of the present invention . In this embodiment, a structure capable of further reducing the angle of incidence of light on the surface to be illuminated than in the first embodiment. Has taken. FIG. 12A shows a case where the aperture diameter (D shown in the figure) of the elliptical mirror (first concave mirror) 18 is large.
FIG. 12B shows that the opening diameter of the ellipsoidal mirror 18 is as shown in FIG.
2 (a) (the second embodiment). As shown in this figure, the angle of incidence of light on the irradiated surface 5 (θ shown in FIG. 12 ) is indicated by 22 of the light incident on the irradiated surface 5 when the aperture diameter of the elliptical mirror 18 is large. When the aperture diameter of the ellipsoidal mirror 18 is small, the one shown in 23 of the light incident on the irradiated surface 5 is the largest, and as is clear from the drawing, the incident light 23
Is smaller than the incident angle of the incident light 22. Therefore, if it is good incident angle θ is small, Fig.
As shown in FIG. 12B, this can be achieved by reducing the opening diameter D of the elliptical mirror 18 corresponding to the first concave mirror in the present invention. Also, the size of the spherical mirror 16 can be reduced. Also in the present embodiment, the condenser lens group 4 may be provided as in the modification shown in FIG. 10, and the effect of the condenser lens in that case is the same as that of the modification.

On the other hand, as is apparent from FIG. 12 , by changing the size of the light exit window 17 of the spherical mirror 16, the angle of light incident on the surface 5 to be irradiated and the light use efficiency can be adjusted. It is possible. That is, for example, the emission window 1
By reducing 7 of size, it is possible to not incident on the irradiation surface 5 shields the light incident at the largest angle surface to be irradiated 5 as shown in FIG. 12 (theta in Figure 12) This makes it possible to adjust the energy of light with respect to the incident angle of light on the entire irradiated surface 5. Accordingly, in the light source unit in the present invention, by the ellipsoidal mirror <br/> Li Cheng first concave mirror 2, the spherical mirror by Li Cheng second concave mirror 3, and the shape of the focusing lens group 4, an illumination optical system The size of the surface to be illuminated in the device used, the size and characteristics of the light source used in the device, the light utilization efficiency of the surface to be illuminated required for the device, the angle of light incidence on the surface to be illuminated, and the overall size of the device The optimal shape is set in consideration of the above factors.

FIG . 13 shows a configuration in which the light source unit according to the present invention and the condenser lens group 4 are combined. FIG.
Of (a), it is provided in the vicinity of the example both, the light source 1 is elliptical first focus on the vertex side of the ellipsoid mirror 18 (b). Thus, the light reflected by the ellipsoidal mirror 18 is emitted from the light source 1 of the focus position, as shown in FIG., The outside of the spherical mirror 16
Proceeds as it focused on ellipses second focus located, respectively
The light is incident on the condenser lens group 4 disposed outside the spherical mirror 16 .

Condensing lens group 4 in FIG .
Has the effect of substantially parallel emitted to the optical axis of the reflected light by the ellipsoid mirror 18 and condensing lens unit 4 in FIG. 13 (b) is reflected by the ellipsoidal mirror 18 After being further focused by the convex lens having a positive refractive power on the light source 1 side, the convex lens on the surface to be irradiated 5 has the function of converting the light substantially parallel to the optical axis again. Due to each of the condenser lens groups 4 described above, even when the irradiated surface 5 is relatively small,
The irradiated surface 5 can be irradiated with high light use efficiency. Further, in the embodiment shown in FIG. 13 , at least one of the lens surfaces of the condenser lens group 4 is made to be aspherical, so that unevenness in brightness on the irradiated surface 5 is obtained in the same manner as in the modification shown in FIG. Irregularities due to light can be reduced.

[0049]

With the above arrangement, the light source unit according to the present invention
With the light source unit , the light use efficiency can be approximately doubled without deteriorating the angle of incidence on the surface to be irradiated, as compared with the light source unit having the conventional configuration.

Next, display using the light source unit of the present invention.
An embodiment of the apparatus will be described. FIG. 14 shows a first embodiment of a display device using the light source unit according to the present invention . A display using a liquid crystal display element 24 as the light valve 6 of the display device shown in FIG. Device. The illumination optical system including the light source 1 in this embodiment and each embodiment of the display device described later is an illumination optical system using the light source unit according to each embodiment of the present invention described above. Since the functions and effects are the same as described above, their description will be omitted to avoid duplication.

[0052] In the present embodiment, as shown in FIG. 14, the liquid crystal display device 2 light from the light source unit is a surface to be illuminated
4 is incident. The liquid crystal display element 24 in this embodiment is
For example , a transmission type liquid crystal display element such as a twisted nematic (TN) type liquid crystal display element is provided. Liquid crystal is injected between a pair of transparent substrates having a transparent electrode coating. Before and after the liquid crystal cell, two polarizers (polarizing plates) are arranged so that their polarization directions differ from each other by 90 °. Image information is displayed by controlling the transmitted light amount of incident light by combining the selection operation of the polarization component of the element with the transmitted light. According to the illumination optical system using the light source unit of the present invention, it is possible to reduce the light incidence angle (θ in FIG. 4) on the illuminated surface, which is the liquid crystal display element 24, with a small size and high light use efficiency. This makes it possible to obtain a bright and small liquid crystal display device having good characteristics of liquid crystal, that is, performance of a display element.

FIG . 15 shows a second embodiment of the display device using the light source unit according to the present invention. Table of this embodiment
The display device is provided on the surface of the liquid crystal display element 24 shown in FIG. 14 on the side where the light emitted from the light source 1 is incident.
The liquid crystal display device 24 has a configuration in which a microlens array 7 having unit lens portions corresponding to one pixel of the four pixel array and having the same array as the pixel array of the liquid crystal display element 24 is provided. Here, the micro lens array 7 in the present embodiment
Will be described in detail with reference to the drawings.

FIG . 16 is a perspective view showing an example of a liquid crystal display device to which the above-mentioned microlens array is added. FIG.
The liquid crystal display element 24 of FIG. 14 uses a transmission type liquid crystal display element equivalent to the liquid crystal display element of the embodiment of FIG. 14 , and shows a case where a flat microlens array 25 is provided as a microlens array in the liquid crystal display element 24. The flat microlens array 25 is a two-dimensionally arranged microlens array as shown by a broken line in the figure. here,
16 , reference numerals 26 and 26 denote a pair of substrates (transparent substrates) facing each other, 27 denotes a transparent counter electrode provided on one substrate 26, 28 denotes a liquid crystal, 29 denotes a transparent pixel electrode provided on the other substrate 26, Numeral 30 denotes a metal wiring of each electrode provided on the same substrate 26 as 29, a non-linear element or a switching element added as means for individually controlling each pixel, a gap around the pixel electrode, etc., and contributes to display. This is the part (light-shielding part) not to be used. The liquid crystal cell 60 is constituted by these 26 to 30. In the present liquid crystal display element 24, two polarizing plates 31, 31 are arranged on the front and back sides of the liquid crystal cell 60, respectively, so that the respective polarization directions are different from each other by 90 °. By combining the action of rotating the polarization plane and the action of selecting the polarization component of the polarizing plate 31, the incident light 32
Is controlled to display image information. In FIG. 16 , reference numeral 33 denotes light emitted from the liquid crystal display element 24.

The above-mentioned flat plate microlens array 25
Is a unit lens portion (unit refractive index distribution region) 2 having the same shape as a region corresponding to one pixel of the transmission type liquid crystal display element 24.
5a is formed in the same manner as the pixel array of the liquid crystal display element 24. The focal position of each unit lens portion 25a is set so as to coincide with the liquid crystal surface and substantially at the center of the pixel electrode 29 or to be in the vicinity thereof. The incident light is less likely to be blocked by the light shielding portion 30 and has an effect of being effectively guided to the pixel electrode 29. Therefore, the aperture ratio (the ratio of the energy of the light emitted from the liquid crystal display element to the energy of the light incident on the liquid crystal display element) due to the action of each unit lens portion 25a of the flat microlens array 25.
Is high, that is, a bright image information display is obtained.

FIG . 17A shows the liquid crystal display element 24.
FIG. 4 is a diagram showing a relationship between light incident on the lens unit and each unit lens unit 25a constituting the flat microlens array 25.
As shown in FIG. 17A, when the flat microlens array 25 as described above is provided in a light valve such as the liquid crystal display element 24, incident light 32a parallel to the optical axis 35 incident on the flat microlens array 25 is provided. Will converge at the focal position of each unit lens portion 25a of the flat microlens array 25, and all the parallel light incident on the light valve will pass through the pixel electrode 29 instead of the light shielding portion 30, so that bright image information Display can be obtained.

On the other hand, the light emitted from the light source is radiated in various directions as described above.
Are not only light parallel to the optical axis 35, but also various light in the range of the incident angle (θ in FIG. 17A ). As shown in FIG. 17A , when a light beam enters the flat microlens array 25 at an incident angle θ, such as 32b, the light beam may not be focused on the pixel electrode 29 and may enter the light shielding unit 30. . Then, the light incident on the light-shielding portion 30 is shielded and is not included in the outgoing light 33, so that the aperture ratio becomes low and a bright image information display cannot be obtained. FIG. 17B shows a certain illumination optical system.
The horizontal axis represents the angle of the light beam incident on the flat plate microlens array 25 (θ in FIG. 17A ), and the vertical axis represents the relative value of the aperture ratio. In addition, 36 in FIG.
a shows the case where the interval t shown in FIG. 17A is 1.1 mm, and 36b shows the case where t is almost 0 mm. As shown in FIG. 17B , when the incident angle of light is large, the aperture ratio is greatly reduced when t is large, whereas when the t is small, the aperture ratio is larger than when t is large. Hardly changes. Therefore, in order to obtain a brighter image, the liquid crystal display element 24
In order to make all the light rays incident on the light valve such that the angle of incidence is uniform to some extent, the distance between the flat microlens array 25 and the pixel electrode portion (see FIG.
It is desirable to reduce t) of (a) of FIG. 17 and to set an optimum microlens shape in accordance with each illumination optical system and configuration.

[0058] Figure 18 shows a perspective view of a planar microlens array 25 provided on the liquid crystal display device 24 in the embodiment shown in FIGS. 15 to 17. The flat microlens array 25 shown in FIG. 18 is a so-called refractive index formed by, for example, forming a region having a refractive index N different from the refractive index N ₀ with periodicity in a transparent flat glass substrate 37 having a refractive index N _0. It is a distribution type micro lens array. This refractive index distribution type microlens array can be formed by, for example, an ion exchange method.

In the above-mentioned ion exchange method, a mask layer having a required pattern is formed on a transparent plate-like glass by, for example, a metal, and the mask layer is immersed in a molten salt bath so that Na + (sodium ion) and K + contained in the glass are formed. Cation such as (potassium ion) is exchanged with cation such as Tl + (thallium ion) contained in the molten salt through the exposed surface of the glass. The ion-exchanged region has a different refractive index from the original glass, and becomes a unit refractive index distribution region (unit lens portion) 25a having an action of refracting light. By forming a large number of unit lens portions 25a by this ion exchange method, the inside of the transparent flat glass can be provided with a lens function of refracting light, so that the flat microlens array 25 having a flat surface is formed. Further, the shape of the region to be ion-exchanged can be changed by adjusting the shape of the mask layer having the required pattern and the ion exchange time, and the like. The lens portion 25a can be formed in a substantially rectangular shape as shown in FIG .

FIG . 19 shows the effect of the flat microlens array 25 constituted by the microlenses (unit lens portions 25a) having the above-described substantially rectangular shape. FIG.
(A) shows a case where, as a microlens corresponding to one pixel of the liquid crystal display element 24, for example, a region (unit lens portion 25a ') having a lens function such as a refractive index distribution region has a circular shape. As shown in FIG. 19A, the light beam 40 incident on the unit lens portion 25a 'of the flat microlens array 25 does not reach the light shielding portion 30 of the liquid crystal display element 24 due to the above-described lens action. The light passes through the liquid crystal display element 24. However, FIG.
When the unit lens portion 25a ′ has a circular shape as shown in FIG. 7, the region 39 corresponding to one pixel of the liquid crystal display element 24 has a substantially rectangular shape, and thus the unit lens portion 25a ′ And the unit lens unit 25 corresponding to the adjacent pixel
There is a gap that does not have a lens action with a ′,
For this reason , the light beam 41 incident on the gap portion shown in FIG. 19A reaches the light shielding portion 30 of the liquid crystal display element 24 and does not pass through the liquid crystal display element 24.

On the other hand, as shown in FIG.
A region having a lens function, for example, a refractive index distribution region corresponds to a region 39 corresponding to one pixel of the liquid crystal display element, and a unit lens portion 25a having a planar shape (substantially rectangular shape) substantially equal to the region 39 is formed. 19A, the light beam 41 shown in FIG. 19A is subjected to a lens action, and does not reach the light shielding portion 30 of the liquid crystal display element 24.
The light passes through the liquid crystal display element 24. Therefore, the figure
19B , light transmitted through the liquid crystal display element 24 is increased in FIG. 19B , whereby the apparent aperture ratio can be greatly improved, and a liquid crystal display device which can obtain a bright display can be realized. . In this embodiment, the shape of the unit lens portion 25a having a lens function, for example, a refractive index distribution region, may correspond to the shape of a region corresponding to one pixel of the liquid crystal display element 24 using the flat microlens array 25. The present invention is not limited to the rectangular shape as in the present embodiment. The area having a lens function in the transparent flat glass substrate may be provided on either side of the liquid crystal cell 60 (either the front or back side of the transparent flat glass substrate) or on both sides of the transparent flat glass substrate. It may be provided.

On the other hand, by making the microlens array flat as described above, the flat microlens array 25 can be formed integrally with the liquid crystal cell 60 as shown in FIG . In the liquid crystal cell 60 shown in FIG. 20 , one substrate (incident side transparent substrate) 26 in the configuration of FIG. 16 is also used as the flat plate microlens array 25, thereby
5 is integrated with the liquid crystal cell 60. By doing so, the unit lens portion 25a approaches the liquid crystal surface, and the interval t in FIG. 17A can be reduced as much as the thickness of the substrate 26 on the side of the incident light 32 in FIG. 16 is eliminated.
As a result, as described above, even when the angle of incidence of light on the liquid crystal display element 24 increases to some extent, the aperture ratio remains high,
A brighter liquid crystal display element can be obtained. Further, as described above, by integrally forming the liquid crystal cell 60 and the flat microlens array 25, the number of components of the liquid crystal display device provided with the flat microlens array is reduced, which is suitable in terms of manufacturing such as cost. , When the liquid crystal cell and the flat microlens array are not integrated,
Positioning of each unit lens unit and each pixel of the liquid crystal display element is simplified.

As described above, in order to improve the brightness of the liquid crystal display device, it is effective to increase the aperture ratio of the liquid crystal display element . By providing the micro lens array 7 shown in FIG. Element 24
Can increase the apparent aperture ratio, and a display device capable of brighter display can be obtained. However, as described above, even in the liquid crystal display element 24 provided with the microlens array 7, the angle of light incident on the microlens array 7 is
It is desirable that they are aligned as parallel to the optical axis of the unit lens as possible, because the aperture ratio can be further increased. Therefore, by combining the above-described light source unit according to the present invention with a liquid crystal display device having a microlens array, the light use efficiency can be increased when the microlens array is used as the surface to be irradiated, and the light enters the microlens array. The angle of light can be made nearly parallel to the optical axis of the unit lens portion as compared with the conventional case. Thereby, the effect of improving the aperture ratio by the microlens array is greatly improved compared to the case where the light source unit according to the present invention is not used, and the high light use efficiency by the light source unit of the present invention and the aperture ratio of the display element by the microlens array By the synergistic effect with the improvement, the performance such as the brightness of the liquid crystal display device can be greatly improved. As described above, as shown in FIG. 15 , by combining the light source unit according to the present invention with a liquid crystal display device having a microlens array, a bright, small, and high-performance liquid crystal display device can be realized.

The microlens array according to the present invention is not limited to the above-described manufacturing method, but may be formed of other materials such as a molding method using a plastic lens, a compression molding method using a heat-deformable resin on the surface of a glass substrate, and the like. It is needless to say that the aperture ratio can be improved as long as it has a function as a lens.

Further, in the embodiments shown in FIGS . 14 and 15 , an example of a so-called direct-view type liquid crystal display device for directly viewing a liquid crystal display element is shown. The projection lens 8 is provided as shown in FIG. 1 and the image of the liquid crystal display element can be enlarged and projected on a screen 9 to be used as a so-called projection display device.

Next, the light source unit according to the present invention was used.
A third embodiment of the display device will be described with reference to FIG . As shown in FIG. 21 , in the display device of this embodiment, the liquid crystal display element 24 with the microlens array used in the second embodiment of the liquid crystal display device described above is replaced by so-called three primary colors of R (red). , G (green), and B (blue), respectively, to provide a three-panel projection type liquid crystal display device (projection type color liquid crystal display device) using three units in total.

In this embodiment, a light beam emitted from a light source 1 using a lamp such as a metal halide, xenon, or halogen lamp is reflected directly or by a first concave mirror 2 or reflected by a second concave mirror 3. After 1
Is reflected by the concave mirror 2 and passes through an infrared cut filter 43 that reflects heat rays and passes visible light. The light beam that has passed through the infrared cut filter 43 is
, Is emitted so as to be substantially parallel to the optical axis, and thereafter, the light beam is reflected by a B (blue) reflecting dichroic mirror 44 arranged at an angle of 45 ° with respect to the optical axis of the light beam.
The light of B is reflected by a, and R (red) and G (green)
Light is transmitted. The reflected B light is reflected by the total reflection mirror 45.
The optical path is bent by the first liquid crystal display element 2
4 is incident. On the other hand, B reflection dichroic mirror 4
The R and G rays transmitted through 4a enter a G reflection dichroic mirror 44b disposed at an angle of 45 ° with respect to the optical axis of the rays, and the G reflection dichroic mirror 44b
, The G light is reflected, and the R light is transmitted. The reflected G light is directly incident on the second liquid crystal display element 24. The R ray transmitted through the G reflection dichroic mirror 44b has its optical path bent by the total reflection mirrors 45 and 45 and is incident on the third liquid crystal display element 24.

Further, the images corresponding to R, G, and B displayed on the liquid crystal 28 surface of each liquid crystal display element 24 are
It has a B-reflecting surface 47 and an R-reflecting surface 48, and the reflecting surfaces are combined by a dichroic prism 46 configured to be at an angle of 45 ° with respect to the optical axis of each color light beam. Is magnified by the projection lens 8 to obtain a magnified real image on the screen 9. Here, the dichroic prism 46 in the present embodiment is replaced with a dichroic prism 46 if it has an action of synthesizing images corresponding to R, G, and B displayed on the liquid crystal surface of each liquid crystal display element 24. Is possible.

As a driving circuit of the liquid crystal display element in this embodiment shown in FIG. 21 , there is, for example, a circuit as shown in the lower part of FIG. That is, laser disk, VT
A video input from R or the like is processed by a video chroma processing circuit 54 and input to output circuits 55 corresponding to each of R, G, and B colors. R, G, B output circuits 5
In 5, the polarity of the video signal corresponding to each color is inverted every vertical period in order to drive the liquid crystal display element 24 by AC, and is input to the liquid crystal display element 24 via the X driver 56 corresponding to each color. Under the control, a voltage is applied to the liquid crystal display element 24 via the Y driver 51 corresponding to each color. The video chroma processing circuit 54, the output circuit 55 corresponding to each color, the X driver 56 and the Y driver 51 are synchronized by the synchronization processing circuit 49 and the controller 50 corresponding to each color.

According to the present embodiment shown in FIG . 21 , for example, the first concave mirror 2, the second concave mirror 3, and the condenser lens group 4 are
The liquid crystal display element 24 having the configuration shown in FIG . 10 or FIG.
By using the one shown in FIG . 16 or FIG. 20 , a bright, small, and high-performance projection liquid crystal display device can be obtained. The condenser lens group 4 may be omitted depending on the configuration of the concave mirror or the like, and a part or all of the condenser lens group 4 may be disposed on the liquid crystal display element side with respect to the B reflection dichroic mirror 44a or on the first concave mirror. It may be provided between the second concave mirror 3 and the second concave mirror 3, that is, in the vicinity of the opening of the first concave mirror 2. The operations of the flat microlens array, the light source unit, and the like have already been described, and a detailed description thereof will be omitted.

[0071] Note here, to the light source unit <br/> in the present invention, as the illuminated surface illuminated by said light source unit, a polarization conversion element having the effect of changing the polarization direction of the light or optical, such as a dichroic mirror It goes without saying that the operation of the light source unit of the present invention does not change even when components are arranged.

[0072]

As described above, according to the present invention, it is possible to obtain a light source unit and a display device having high efficiency of using light from a light source and having small size and high performance .

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of the principle of a light source unit of the present invention and a display device using the same.

FIG. 2 is an explanatory diagram schematically illustrating an illumination optical system other than a light source as a single thin lens.

FIG. 3 is an explanatory diagram showing an operation of a concave mirror of the light source unit.

FIG. 4 is an explanatory view showing an operation of a concave mirror of the light source unit.

FIG. 5 is an explanatory diagram showing a state of an image forming operation by a light source unit.

FIG. 6 is an explanatory diagram showing direct light and the like from a light source of a light source unit.

FIG. 7 is an explanatory view showing the principle of the light source unit of the present invention.

FIG. 8 is a sectional view showing a first embodiment of the light source unit according to the present invention .

FIG. 9 is a perspective view showing an example of a spherical mirror serving as a second concave mirror in FIG. 8;

FIG. 10 illustrates the operation of the condenser lens in the light source unit .
It is a figure for clarification.

11 is another example of the spherical mirror as the second concave mirror in FIG .
It is a perspective view showing an example .

FIG. 12 shows a second embodiment of the light source unit according to the present invention .
FIG .

FIG. 13 shows a light source unit according to the present invention including a condenser lens group.
It is sectional drawing which shows the structure combined .

FIG. 14 shows a display device using the light source unit of the present invention.
It is sectional drawing which shows one Example .

FIG. 15 shows a display device using the light source unit of the present invention.
It is sectional drawing which shows 2 Examples .

FIG. 16 is a perspective view showing a configuration of the liquid crystal display device of FIG .

FIG. 17 illustrates the operation of the flat microlens array of FIG . 16;
FIG .

FIG. 18 schematically shows the flat microlens array of FIG .
It is a partial perspective view shown in FIG.

19 is a flat microphone having the rectangular unit lens unit of FIG .
In contrast to the function of the lens unit and the circular lens unit
It is an explanatory diagram showing.

FIG. 20 is a perspective view showing a modification of the liquid crystal display device of FIG.

FIG. 21 illustrates a display device using the light source unit of the present invention.
It is sectional drawing which shows 3 Example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 1st concave mirror 3 2nd concave mirror 4 Condensing lens group 5 Irradiation surface 6 Light valve 7 Micro lens array 8 Projection lens 9 Screen 10 Thin lens 11 Point light source 12 Linear light source 13 Parabolic mirror 16 Spherical mirror 17 Emission window 18 Elliptical mirror 25 Flat microlens array 25a Unit lens unit 26 Substrate (transparent substrate) 27 Counter electrode 28 Liquid crystal 29 Pixel electrode 30 Light shielding unit 31 Polarizing plate 32 Incident light 33 Outgoing light 35 Optical axis 43 Infrared cut filter 44a , 44b, 44c Dichroic mirror 45 Total reflection mirror 46 Dichroic prism

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI G03B 33/12 G02F 1/1335 530 (72) Inventor Mio Ariki 292 Yoshidacho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. (72) Inventor Takashi Tsunoda 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Video and Media Research Laboratory (72) Inventor Tatsu Yamazaki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Video and Media Research Laboratory (72) Inventor Takesuke Maruyama 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Visual Media Research Laboratory, Hitachi, Ltd. (56) References JP-A-3-51882 (JP, A) JP-A-62-94826 (JP) JP-A-64-35415 (JP, A) JP-A-4-120530 (JP, A) JP-A-4-53926 (JP, A) JP-A-3-293615 (JP, A)

Claims (2)

(57) [Claims] 1. A light source unit comprising a first concave mirror arranged on one side and a second concave mirror arranged on the other side on both sides of a light source on the same optical axis, wherein the first concave mirror is , first, second the reflecting surface is on the optical axis
Form part of an ellipsoid having a focal point of focus of the two
The position of the first focal point on the reflection surface side of the points is set substantially at the position of the light source, and the second concave mirror is configured such that the reflection surface has a spherical surface centered at the position of the light source. forms a part, the reflective surface is disposed to face the reflective surface of the first concave mirror, the radius of the spherical surface is the
From the position of the first focal point of the first concave mirror to the position of the second focal point
The distance from the light source is set to be smaller than the distance to the position , and the second concave mirror is placed on the optical axis on the optical axis.
Projected directly toward the first concave mirror, the first concave mirror
Pass the light reflected by and focus on the second focal point
With the light emitted from the light source and directly to the second concave mirror.
And reflected by the second concave mirror, then the first
The light reflected by the concave mirror is also passed and collected at the second focal point.
A light source unit, characterized in that an opening is provided . 2. The light source unit according to claim 1, a lens group, and a light valve , wherein light from the light source unit is transmitted through the lens group to the light bar.
A display device configured to display an image by irradiating the light onto the lube .