JP2003098597A - Illumination device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device in which high polarization conversion efficiency can be obtained with simple constitution and which is superior in light resistance and heat resistance. SOLUTION: The illumination device 1 is provided with a light source 2 and the rod lens 4 of a uniform illumination system, which divides a luminous flux from the light source 2 into multiple light fluxes and emits them. The reflecting polarizer 5 of a structure birefringent type, which transmits a partial linear polarized beam in the luminous fluxes which are made incident on the rod lens 4 from the light source 2 and reflects the partial linear polarized beam is disposed on the incident side of the rod lens 4. A reflecting mirror 3 reflecting the polarized beam reflected by the reflecting polarizer 5 is disposed on the incident side of the rod lens 4 in accordance with an area except for an opening part 3a (light incident area) in the incident end face of the rod lens 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device and a projector, and more particularly to the structure of a lighting device having excellent polarization conversion efficiency.

[0002]

2. Description of the Related Art In recent years, the development of information equipment has been remarkable, and the demand for thin, high-resolution, low-power-consumption display devices has been increasing, and research and development have been advanced. Among them, the liquid crystal display device is expected as a display device that can electrically control the alignment of liquid crystal molecules to change the optical characteristics and can meet the above needs. As one form of such a liquid crystal display device, there is known a projector that enlarges and projects an image emitted from an image source including an optical system using a liquid crystal light valve on a screen through a projection lens.

The projector uses a liquid crystal light valve as a light modulating means, but in particular, TN (Twisted Nemati).
In principle, the liquid crystal light valve of type c) uses only polarized light in one direction for display, so approximately half of the indefinite polarized light flux emitted from the light source is not used for display. Therefore, an illumination device for a projector provided with a polarization conversion system for the purpose of increasing the utilization efficiency of light by making it possible to use light that is not normally used by aligning the indefinitely polarized light flux with one-direction polarized light is disclosed in JP-A-8-304739. Japanese Patent Laid-Open No. 10-2
It is disclosed in Japanese Patent No. 32430.

Further, in a lighting device for a projector, a light flux emitted from a light source such as a metal halide lamp generally has a non-uniform illuminance distribution. However, in an illuminated area, specifically, a rectangular liquid crystal light valve. In order to make the illuminance distribution on the display surface uniform, it is known to provide a uniform illumination system including two fly-eye lenses or a rod-shaped light guide.

[0005]

As described in the above publication, for example, in a conventional illumination device, a polarization beam splitter (Polarized Beam Splitter) is used as a polarization conversion system.
In most cases, a combination of an array and a retarder made of an organic film is used. However, in this system, while high polarization conversion efficiency can be obtained, there is a problem that the structure of the PBS array is complicated and expensive, and the cost of the entire illumination device increases. Further, since a high-luminance light source is used in a lighting device for a projector, a retardation plate made of an organic film has a problem in light resistance and heat resistance.

The present invention has been made in order to solve the above problems, and provides a lighting device which has a simple structure, high polarization conversion efficiency, and excellent light resistance and heat resistance. With the goal. Another object of the present invention is to provide a highly reliable projector having the above-mentioned lighting device.

[0007]

In order to achieve the above-mentioned object, an illuminating device of the present invention comprises a light source and a light beam splitting means for splitting a light beam from the light source into a plurality of light beams by utilizing reflection. An illumination device comprising: a light beam splitting means;
On the exit side of the light beam splitting means, there is provided a polarization conversion means provided with a reflection-type polarizer that transmits a part of the polarized light of the light beam incident on the light beam dividing means from the light source and reflects a part of the polarized light. A reflecting mirror, which reflects the polarized light reflected by the reflection type polarizer, is provided on the incident side of the light beam splitting means in a region other than the incident region of the light beam from the light source on the incident end face of the light beam splitting means. Is characterized by.

In the illumination device of the present invention, the light emitted from the light source is first incident on the light beam dividing means, divided into a plurality of light beams, and emitted from the light beam dividing means. The "beam splitting means" here has a function of splitting a bundle of incident light fluxes from the light source into a plurality of light fluxes. It is used for the purpose of making the illuminance distribution uniform in the illuminated area by superimposing it on another optical system that is arranged. In the present invention, since the reflective polarizer is provided on the exit side of the light beam splitting means, when light is incident on the reflective polarizer from the light beam splitting means, the polarization direction that coincides with the transmission axis of the reflective polarizer. Light is transmitted and the other light is reflected. The light transmitted through the reflective polarizer contributes to the illumination of the illuminated area, while the light reflected by the reflective polarizer propagates in the reverse direction (on the incident end face side of the luminous flux splitter) inside the luminous flux splitter. .

Since the light beam emitted from the light source needs to be incident on the light beam splitting means, a predetermined incident region (light transmitting region) is provided on the incident end face thereof. The shape of the incident region substantially matches the cross-sectional shape of the light beam from the light source, and is, for example, circular. In the case of the illumination device of the present invention, since the reflection mirror is provided corresponding to a region other than the incident region, of the polarized light reflected by the reflective polarizer and returning in the opposite direction to the incident end face side, the incident region. The polarized light that has entered the other area is reflected by the reflection mirror and is propagated again to the exit side of the light beam splitting means. In this way, since the reflective polarizer is arranged on the exit side of the light beam splitting means and the reflection mirror is arranged on the incident side, the polarized light reflected by the reflective polarizer is repeatedly reflected inside the light beam splitting means. However, during the reflection, the polarization direction does not always change, but changes. Then, when the changed polarization direction matches the transmission axis of the reflective polarizer, the light that has been repeatedly reflected can pass through the reflective polarizer and reach the illuminated area to contribute to illumination. can do.

According to the illuminating device of the present invention, light having a polarization direction which could not be transmitted through the reflection type polarizer at the beginning can be recycled by such a mechanism, and the light can be illuminated as light having one kind of polarization direction. Since the light can be contributed, the polarization conversion efficiency can be increased as compared with the conventional lighting device. Further, since it is sufficient to dispose a reflection-type polarizer on the exit side and a reflection mirror on the entrance side of a conventional light beam splitting means, it is possible to reduce the polarization conversion efficiency (the efficiency of converting indefinite polarization into specific polarization) with a simple configuration. A high illumination device can be realized.

As the function of the reflection type polarizer, one that transmits one of the linearly polarized lights which are orthogonal to each other and reflects the other can be used. In that case, for example, the X-polarized light beam is transmitted through the reflective polarizer, and the Y-polarized light beam (the X-polarized light beam and the Y-polarized light beam are orthogonal to each other in the polarization direction) is reflected. The Y-polarized light beam reflected by the reflective polarizer repeats reflection with the reflection mirror on the incident side, the polarization direction changes while propagating inside the light beam splitting means, and part of it is converted into an X-polarized light beam. Then, the light is transmitted through the reflective polarizer. In this way, the polarized light can be recycled and can contribute to the illumination as light having one type of polarization direction, so that the polarization conversion efficiency can be improved as compared with the conventional illumination device.

When using linearly polarized light, it is desirable to use a structural birefringent polarizer. "Structural Birefringent Polarizer"
Has a grating portion in which two types of media having different refractive indexes are alternately arranged in a stripe shape with a period shorter than the wavelength of light, and the light is divided into a polarization component parallel to the stripe and a polarization component perpendicular to the stripe. Since the perceived refractive indices are different, a birefringent action occurs, and the birefringence functions as a polarizer. That is, as shown in FIG. 12, in the structural birefringent body 100 having a structure including a plurality of mediums A101 arranged in a stripe pattern at a pitch smaller than the wavelength of incident light, the gap between the adjacent media A101 is It is necessary that the medium B102 having a refractive index different from that of the medium A101 is filled. The medium B102 may be solid, liquid or gas.

[0013] In structural birefringence body 100 having such a structure, the refractive index n ₂ of the refractive index n ₁ and the medium B102 medium A101 is different, valid by the polarization direction of light incident on the structural birefringence body 100 refraction The rates are different. For example, when the refractive index n ₁ of the medium A101 is larger than the refractive index n _{2 of the} medium B102, the effective refractive index of the polarized light A vibrating in a direction substantially parallel to the extending direction of each medium A101 is It becomes larger than the effective refractive index for the polarized light B that oscillates in a direction substantially perpendicular to the extending direction of the medium A101.

When the medium A and the medium B are made of a dielectric material, and the width of the medium A101 is a and the width of the medium B102 is b,
Of the light incident on the structural birefringent body 100, the effective refractive index Na for polarized light A and the effective refractive index Nb for polarized light B are
Are known to be represented respectively by the following equations (1) and (2) (for example, M. Born and E. Wolf: Princi
ples of Optics, 1st ed. (Pergamon Press, New York,
1959) p.705-708). As can be seen from the following equations (1) and (2), the thickness a of the medium A101 and the thickness b of the medium B102 are
The effective refractive index can be changed in the range of n _{1 to} n ₂ by the ratio of.

[0015]

[Equation 1]

It has been described above that the structural birefringent body exhibits different optical properties depending on the polarization state of light. Here, when a light reflector such as a metal or a semiconductor is used as the medium A,
By treating the permittivity as a complex number, it can be treated in the same manner as when obtaining the effective refractive index for the dielectric. However,
The effective refractive index is a complex number. Effective Medium Theory
(For example, Dominique Lemercier-lalanne: Journal of
Modern Optics, 1996, vol43, no.10,2063-2085), or more strictly, Rigorous Coupled-Wave Analysis (MGMoharam:
Numerical calculation using J.Opt.Soc.Am.A, 12 (1995) 1077) shows that when a metal is used as the medium A, the imaginary part of the effective refractive index of the structural birefringent body with respect to the polarized light A becomes large. As a result, it is known that the incident polarized light A is reflected by the structural birefringent body. On the other hand, it is known that the imaginary part of the effective refractive index for the polarized light B has a small value, and the polarized light B transmits through the structural birefringent body. In this way, by forming a periodic structure smaller than the wavelength with two types of media, polarized light that oscillates in a direction parallel to the direction in which the periodic structures of the structural birefringent are arranged is transmitted, and in the direction in which the periodic structures are arranged. A function of reflecting polarized light vibrating in the orthogonal direction can be provided.

Since the above-mentioned structural birefringent polarizer can be formed by using an inorganic material, it has far higher light resistance and heat resistance than a conventional polarization conversion system using a retardation plate made of an organic film. It is excellent and can realize a stable polarization conversion action even if the intensity of illumination light is high.

Although the reflection type polarizer for separating the linearly polarized light into the transmitted light and the reflected light has been described above, a circularly polarized light may be used. That is, as the reflective polarizer, one having a function of transmitting one of the circularly polarized lights having opposite rotations and reflecting the other may be used. However, in that case, it is desirable to provide a quarter wavelength plate between the light beam splitting means and the reflective polarizer.

When the light beam from the light source is directly incident on the light beam splitting means, the light beam is in an indefinite polarization state. Therefore, when the indefinite polarized light beam emitted from the light beam splitting means passes through the quarter wavelength plate, it is separated into an L circular polarized light beam and an R circular polarized light beam (the L circular polarized light beam and the R circular polarized light beam rotate with respect to each other. Direction is opposite). Then, in the reflective polarizer, for example, the L circularly polarized light flux is transmitted and the R circularly polarized light flux is reflected. Similar to the case of the linearly polarized light described above, the R circularly polarized light beam reflected by the reflection type polarizer is repeatedly reflected between the reflection mirror on the incident side and transmitted through the quarter wavelength plate, or the light beam splitting means. The polarization direction changes while propagating inside the
Part of it becomes an L-circularly polarized light beam and passes through the reflective polarizer. In the case of circularly polarized light, the polarized light can be recycled by the same mechanism as in the case of linearly polarized light, and it can contribute to illumination as light having one type of polarization direction. The efficiency can be increased.

In the case of using the above-mentioned circularly polarized light, it is desirable to further provide a quarter wavelength plate on the exit side of the reflective polarizer. According to this configuration, the light emitted from the reflective polarizer as the circularly polarized light beam is converted into the linearly polarized light by passing through the quarter-wave plate, so that the configuration of the projector to which the illumination device is applied is linearly polarized light. The same can be applied to the case of a lighting device that emits light.

As a concrete structure of the light beam splitting means,
It is possible to use a rod-shaped light guide, or a tubular light guide whose inner surface is a reflection surface, that is, a so-called rod lens. In that case, as the shape of the rod lens, the exit end surface needs to be optically conjugate with the illuminated region (similar shape), but the entrance end surface and the exit end surface do not necessarily have to be similar shapes. Further, it may have the same diameter from the entrance side to the exit side, but may have a tapered shape or a tapered shape. When the tapered shape or the tapered shape is adopted, the exit angle can be changed with respect to the incident angle of light to the rod lens. Each effect will be described later.

At the incident end face of the light beam splitting means,
It is preferable that the incident area has a circular shape and the reflection mirror is provided in an area outside the circular incident area. Normally, the intensity distribution of the light flux emitted from the light source is circular when viewed from the optical axis direction, and accordingly, it is the most efficient method with the least loss that the incident area of the light flux splitting means is also circular. . Here, if the illuminated area is a rectangular liquid crystal light valve, the exit end surface of the light beam splitting means is also rectangular, and if the entrance end surface is similar to the exit end surface and is rectangular, a circle is formed inside the rectangular entrance end surface. Since the incident area of is arranged, a reflection mirror may be provided around it.

In particular, when both the incident end surface and the exit end surface of the light beam splitting means are rectangular, it is desirable that the incident end surface is a narrower rectangular shape than the exit end surface.
For example, even if the exit face has a shape close to a square,
If the incident end face is formed in a more elongated rectangular shape, the area of the reflection mirror installation area can be made larger than the area of the incident area, and thus the polarization recycling rate can be improved.

Regarding the arrangement of the incident area in the incident end surface of the light beam splitting means, the center of the incident area may be decentered with respect to the center of the incident end surface in addition to the case where the center of the incident area is aligned with the center of the incident end surface. Of course, the optical axis of the light beam incident on the light beam splitting means (the optical axis of the light source) and the incident end face of the reflective polarizer may form an angle other than vertical. Such a configuration, for example, by inclining the optical axis of the light source with respect to the system optical axis passing through substantially the center of the light beam splitting means, or while shifting the optical axis of the light source parallel to the system optical axis, This can be realized by arranging the incident end surface of the light beam splitting means so as to be inclined so as to form an angle other than perpendicular to the system optical axis. Particularly, in the latter configuration, the optical axis of the light source and the system optical axis are parallel to each other, which is advantageous in that the optical system can be easily downsized. According to this configuration,
Since the proportion of the reflected light from the reflective polarizer is reflected by the reflecting mirror installed on the incident side of the light beam splitting means, high polarization conversion efficiency can be realized. This will also be described later in detail.

A projector according to the present invention comprises the above-mentioned lighting device of the present invention, a light modulation means for modulating the light emitted from the lighting device, and a projection means for projecting the light modulated by the light modulation means. It is characterized by According to this configuration, since the illumination device having high polarization conversion efficiency and durability is provided, it is possible to realize a projector with high brightness and high reliability.

In particular, when the light modulation means is a liquid crystal light valve, the direction in which the illumination angle of the illumination light beam emitted from the light beam splitting means of the illuminating device is widened and the direction in which the liquid crystal light valve has a wide viewing angle are aligned with each other. Is desirable. With this configuration, it is possible to obtain a high contrast and realize a projector with high display quality.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION [First Embodiment] A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram of the illumination device of the present embodiment. In FIG. 1, reference numeral 2 is a light source, 3 is a reflection mirror, 4 is a rod lens (beam splitting means), 5 is a reflective polarizer, 6 is a relay system, and 7 is a liquid crystal light valve (illumination area).

As shown in FIG. 1, the illumination device 1 of the present embodiment has a light source 2 including a lamp 8 such as a metal halide lamp and a reflector 9, a rod lens 4, three lenses 10, 11, The relay system 6 includes a relay system 6.

As the rod lens 4, a transparent rod-shaped light guide body (for example, a glass rod) or a tubular light guide body having an inner surface as a reflection surface (for example, a plurality of reflection mirrors are arranged in a tubular shape inwardly). Kaleidoscope) is used. In the case of the present embodiment, as the shape of the rod lens 4, a rectangular columnar light guide body having the same cross section from the incident side to the exit side is used. The shapes of the incident end face and the exit end face are
As shown in the lower side of FIG. 1, it has a similar shape to the illuminated area, that is, the liquid crystal light valve 7, and has, for example, a rectangular shape with an aspect ratio of 3: 4. In the present embodiment, both the incident end face and the exit end face are similar in shape to the liquid crystal light valve 7, but the incident end face does not necessarily have to be similar. The rod lens 4 has a function of splitting the incident light from the light source 2 into a plurality of light fluxes, and the light fluxes from the plurality of light source images generated thereby are superposed in the illuminated area by a light transmission means such as a relay system 6. By doing so, the illuminance distribution in the liquid crystal light valve 7 is made uniform.

A reflection mirror 3 having a circular opening 3a (light incident area) in the center is installed on the entrance end surface of the rod lens 4 with the reflection surface facing the inside of the rod lens 4. As a concrete installation mode of the reflection mirror 3,
If the rod lens 4 is a tubular light guide, for example, a mirror having an opening in the center may be fitted to the end of the rod lens, or if the rod lens 4 is a rod-shaped light guide,
For example, an annular dielectric mirror that is patterned so that the light transmitting portion is formed in the center may be directly formed on the end surface of the rod lens. In any case, it suffices that the reflection mirror 3 is provided in a region other than the light incident region where the light flux from the light source 2 is incident. Further, the structure of the light incident region from the light source 2 is not limited to the opening, and may be, for example, a structure closed with a light transmissive member.

A reflective polarizer 5 is installed on the exit end surface of the rod lens 4. In the case of the present embodiment, as the reflective polarizer 5, a structural birefringent reflective polarizer that separates indefinite polarized light into two kinds of linearly polarized light orthogonal to each other as shown in FIG. 3 is used. . This reflective polarizer 5
As shown in FIG. 3, a large number of ribs 14 made of a light-reflective metal such as aluminum are formed on the glass substrate 15 at a pitch smaller than the wavelength of incident light. That is, the reflection-type polarizer 5 has a birefringence effect due to the Al ribs 14 having different refractive indices and the air being alternately arranged in a stripe shape at a pitch smaller than the wavelength of the incident light, thereby generating a birefringence effect. Function. With this configuration, when indefinite polarized light is incident on the surface on which the Al rib 14 is formed, S polarized light vibrating in a direction parallel to the extending direction of the Al rib 14 is reflected, and the extending direction of the Al rib 14 is increased. P-polarized light oscillating in the direction perpendicular to (the direction in which the Al ribs are arranged) is transmitted.

With respect to the direction of the reflective polarizer 5, the surface (incident surface) on the side where the Al rib 14 is formed is placed so as to face the inside of the rod lens 4 with emphasis on the efficiency of polarization separation. Is desirable. However, when it is used in combination with a rod-shaped rod lens whose inside is clogged instead of a tubular light guide, there is a very small gap between the exit end face of the rod lens and the Al rib 14. It is desirable to place both. Alternatively, the Al rib 14
The surface (incident surface) on the side where liquid crystal is formed is the liquid crystal light valve 7.
The reflective polarizer 5 may be installed so as to face the (illumination area) side. In that case, the efficiency of polarized light separation may be slightly reduced, but since it can be installed closely to the rod lens, it is easy to install and when used in combination with a rod-shaped rod lens with a clogged inside. Since the exit end surface of the rod lens and the surface of the reflective polarizer 5 on the side where the Al rib 14 does not exist can be brought into close contact with each other and optically integrated, there is an advantage that light loss that is likely to occur at the interface can be reduced.

In the case of this embodiment, three lenses 10, 11 and 12 are used as the relay system 6, and the lens 10 closest to the rod lens 4 is installed so as to be in close contact with the reflection type polarizer 5. However, the number of lenses and the positions of the lenses used in the relay system 6 are not limited to this, and can be changed as appropriate.

Next, the operation of the illumination device 1 having the above structure will be described with reference to FIG. As shown in FIG. 2, the light beam emitted from the light source 2 enters the inside of the rod lens 4 through the opening 3a of the reflection mirror 3 and propagates toward the reflection-type polarizer 5 arranged on the emission side. . At this point in time, the light flux is indefinitely polarized, but when the light enters the reflective polarizer 5, it is polarized and separated according to the polarization direction, and as shown in FIG. 3, the Al rib 14 of the reflective polarizer 5 extends. P-polarized light in a direction (transmission axis direction) perpendicular to the existing direction is transmitted, and Al rib 1
S-polarized light in a direction parallel to the extending direction of 4 is reflected. The P-polarized light transmitted through the reflective polarizer 5 contributes to the illumination of the liquid crystal light valve 7 via the relay system 6, while the S-polarized light reflected by the reflective polarizer 5 travels inside the rod lens 4 in the opposite direction (incident end face). Side).

The S-polarized light reflected by the reflective polarizer 5 reaches the incident end face of the rod lens 4 after that, but the opening 3
Since the reflection mirror 3 is arranged in a region other than a, it is reflected by this reflection mirror 3 and is propagated again to the exit side of the rod lens 4. Since the reflective polarizer 5 is arranged on the exit side of the rod lens 4 and the reflection mirror 3 is arranged on the incident side in this way, S-polarized light that does not pass through the reflective polarizer 5 is incident on the entrance side and the exit side of the rod lens 4. However, the S-polarized light does not always maintain this polarization direction, and when it is reflected by the inner surface of the rod lens 4, the polarization direction rotates and a part thereof is converted into P-polarized light. When it reaches the reflective polarizer 5 in the P-polarized state, the reflective polarizer 5
Can be transmitted and can contribute to the illumination of the liquid crystal light valve 7.

According to the illuminating device 1 of the present embodiment, the polarized light that could not be transmitted through the reflective polarizer 5 at the beginning can be recycled by such a mechanism and can contribute to the illumination. It is possible to improve the utilization efficiency of polarized light as compared with the above illumination device, and realize a bright illumination device. Further, since it is sufficient to dispose the reflective polarizer 5 on the exit side and the reflection mirror 3 on the incident side of the rod lens 4 which has been conventionally used as a uniform illumination system,
It is possible to realize a lighting device having a high polarization conversion efficiency (the efficiency of converting indefinite polarized light into specific polarized light) with a simple configuration.

Further, since the structural birefringent reflection type polarizer 5 can be formed by using an inorganic material such as a glass substrate or aluminum, the conventional polarization conversion using a retardation plate made of an organic film. It has far superior light resistance and heat resistance as compared with the system, and can realize a stable polarization conversion action even if the intensity of illumination light is high.

[Second Embodiment] The second embodiment of the present invention will be described below.
The embodiment will be described with reference to FIG. The basic configuration of the illumination device of this embodiment is the same as that of the first embodiment, but the first embodiment uses a reflective polarizer that separates linearly polarized light, The form is different in that a reflective polarizer that separates circularly polarized light is used. Therefore, in this embodiment, only the periphery of the rod lens will be described with reference to FIG. 4, and description of the light source and the relay system will be omitted.

In the illumination device of this embodiment, the reflecting mirror 3 on the incident side of the rod lens 4 has the same structure as that of the first embodiment, but the structure on the emitting side is different. That is, as shown in FIG. 4, a circularly polarized light having a function of transmitting one (for example, L-polarized light) of circularly polarized lights having opposite rotations to the most exit side of the rod lens 4 and reflecting the other (R-polarized light). A separate reflective polarizer 17 is installed. As this type of reflective polarizer 17, for example, a polarizer using cholesteric liquid crystal can be used. The first quarter-wave plate 18 is installed on the light source 2 side of the reflective polarizer 17, and the second quarter-wave plate 19 is installed on the relay system 6 side of the reflective polarizer 17. ing. Figure 4
Then, for convenience of description, the first quarter-wave plate 18, the reflective polarizer 17, and the second quarter-wave plate 19 are drawn separately, but they do not need to be particularly separated. It doesn't matter if they are closely attached.

The operation of the illumination device of this embodiment will be described. The point that the indefinitely polarized light beam from the light source 2 enters the rod lens 4 and propagates is the same as that of the first embodiment. When this indefinite polarized light beam passes through the first quarter-wave plate 18, it is separated into an L circularly polarized light beam and an R circularly polarized light beam whose rotation directions are opposite to each other. Specifically, for example, of the indefinite polarized light beam included in the light source light, the linearly polarized light that vibrates in the direction perpendicular to the paper surface in FIG. 4 is converted into the R circularly polarized light light beam, and the linear polarized light that vibrates in the direction parallel to the paper surface Is converted into an L circularly polarized light beam, and these polarized lights are separated.
Next, in the reflective polarizer 17, for example, an L circularly polarized light beam is transmitted and an R circularly polarized light beam is reflected. After that, as in the case of the linearly polarized light of the first embodiment, the R circularly polarized light flux reflected by the reflective polarizer 17 is repeatedly reflected between the incident side reflection mirror 3 and inside the rod lens 4. While being reflected, the polarization direction (rotational direction) changes in the reverse direction, and a part thereof becomes an L circularly polarized light beam and passes through the reflective polarizer 17.

In any case, at the time when the reflective polarizer 17 on the exit side of the rod lens 4 is emitted, all are L-circularly polarized light fluxes, so this polarized light is passed through the second quarter-wave plate 19. By transmitting the light, the L circularly polarized light beam is converted into linearly polarized light that vibrates in a direction parallel to the paper surface. Depending on how the optical axes of the second quarter-wave plate 19 are arranged, it is converted into linearly polarized light that vibrates in the direction perpendicular to the paper surface. Although the second quarter-wave plate 19 is not always necessary, circularly polarized light is converted into linearly polarized light by inserting the second quarter-wave plate 19 at the subsequent stage of the reflective polarizer 17. Therefore, the lighting device of the present embodiment can be used without changing the configuration of the projector side including the liquid crystal light valve 7.

As described above, also in the illumination device of the present embodiment, the polarized light that could not be transmitted through the reflective polarizer 17 at the beginning can be recycled, and contributes to the illumination as light having one kind of polarization direction. Therefore, the polarization conversion efficiency can be increased as compared with the conventional lighting device.
It is possible to obtain the same effect as that of the first embodiment. A cholesteric liquid crystal polarizer was used as the reflective polarizer 17 that separates circularly polarized light. However, since the cholesteric liquid crystal does not have a light-absorbing property, the light resistance and heat resistance are higher than those of a conventional device using an organic film. Can be increased.

[Third Embodiment] The third embodiment of the present invention will be described below.
The embodiment will be described with reference to FIGS. 5 and 6. The basic configuration of the illumination device of this embodiment is the same as that of the first and second embodiments, and only the configuration of the rod lens is different. Therefore, in the present embodiment, only the configuration of the rod lens will be described with reference to FIGS. 5 and 6, and description of the other configurations will be omitted.

In the above embodiment, the cross-sectional shape of the rod lens is constant from the entrance side to the exit side, but in the present embodiment, it is tapered from the entrance side to the exit side as shown in FIG. 5 (a). The tapered rod lens 21 or the inverse tapered rod lens 22 diverging from the incident side to the exit side as shown in FIG. 5B is used. The reflective polarizer 5 is provided on the exit side of the rod lenses 21 and 22,
The reflection mirror 3 is installed on the incident side as in the first and second embodiments. The reflective polarizer 5 may be either a linearly polarized light separating type or a circularly polarized light separating type.

6 (a) and 6 (b) are respectively shown in FIG.
It is a top view of rod lenses 21 and 22 of (a) and (b). When the tapered rod lens 21 as shown in FIG. 5A is used, as shown in FIG.
The light incident on the rod lens 21 enters the reflecting surface 21a of the rod lens 21 at a deeper angle and is reflected, so that the exit angle θ ₂ is wider than the incident angle θ ₁ on the rod lens 21 and is emitted. . On the other hand, in the case of using the rod lens 22 having the divergence as shown in FIG. 5B, the light incident on the rod lens 22 is reflected on the reflection surface of the rod lens 22 as shown in FIG. 6B. Since the light enters and is reflected at a shallower angle with respect to 22a, the exit angle θ ₂ is narrower than the incident angle θ ₁ to the rod lens 22 and the light is emitted. Since the rod lenses 21 and 22 according to the present embodiment have a tapered shape or a reverse tapered shape in both the vertical and horizontal directions, the above-mentioned action is obtained not only in a plan view but also in a side view. Have

When such rod lenses 21 and 22 are applied to the present invention, the following effects are obtained, respectively. When the tapered rod lens 21 shown in FIG. 5A is used, the area of the incident end face can be made larger than that of the exit end face, and therefore the reflection mirror 3 with respect to the cross-sectional area of the light flux incident on the rod lens 21 from the light source 2. The area for installing is relatively large, and the polarization conversion efficiency can be improved. On the other hand, when the rod lens 22 having the diverging tip shown in FIG. 5B is used, the installation area of the reflection mirror 3 cannot be made very large, but as described above, the light emitted from the rod lens 22 is Since the exit angle θ ₂ can be narrowed, when a projector is configured by using the liquid crystal light valve 7 whose contrast characteristic depends on the incident angle of light, it is possible to improve the contrast of the image displayed by the projector. You can The reason is that when the emission angle θ ₂ is small, a large amount of light is incident on the liquid crystal light valve 7 at a small angle, so that it is possible to prevent a decrease in contrast. Of course, the shape of the rod lens is not limited to the above-mentioned two types, and in FIG. 5, for example, a rod lens having different taper shapes (including an inverse taper shape) in the xz plane and the yz plane may be used.

[Fourth Embodiment] The fourth embodiment of the present invention will be described below.
The embodiment will be described with reference to FIG. The basic configuration of the illumination device of this embodiment is the same as that of the first to third embodiments, and only the configuration of the reflecting mirror on the rod lens incident side and the way of incidence of light from the light source 2 to the rod lens are different. Is. Therefore, in this embodiment, only the configurations of the rod lens and the reflection mirror will be described with reference to FIG. 7, and the description of the other configurations will be omitted.

In the case of the present embodiment, it is assumed that an illuminated area, that is, a liquid crystal light valve having a width longer than that of the first to third embodiments and an aspect ratio of 9:16 is used. . Therefore, accordingly, the cross-sectional shape of the rod lens 25 also becomes a horizontally long shape with an aspect ratio of 9:16. The reflective polarizer 5 on the exit side of the rod lens 25 may have the same structure as in the first to third embodiments, but the reflective mirror 24 on the incident side of the rod lens 25 may have the first to third structures. Different from the embodiment. That is,
In the first to third embodiments, the center of the circular light incident region 3a coincides with the center of the incident end face of the rod lens 4, whereas in the present embodiment, the center of the light incident region 24a is the rod lens. It is decentered from the center of the incident end surface of 25 and is displaced in the longitudinal direction of the cross-sectional shape of the rod lens 25 (rightward in the upper drawing of FIG. 7).

Further, in the case of the first to third embodiments, the light source optical axis L of the light beam emitted from the light source 2 is the system optical axis M.
However, in the present embodiment, the light source optical axis L of the light flux from the light source 2 is inclined in the direction in which the center of the light incident area 24a is eccentric, and the light from the light source 2 is incident on the light incident area 24a.
When the light is transmitted through, the light is reflected by the reflective polarizer 5 at a position approximately at the center of the exit end surface of the rod lens 25, and again the reflective mirror 2
The positional relationship is to reach 4.

In this way, the center of the light incident region 24a is decentered from the center of the incident end face of the rod lens 25, and the light source 2
By inclining the light source optical axis L of the light beam emitted from the system optical axis M from the system optical axis M, the light beam in the rod lens 25 is incident on the reflective polarizer 5 at a predetermined angle, and this light is emitted. Since the proportion of the light reflected by the reflection mirror 24 toward the wider area increases, the proportion of the light reflected by the reflection mirror 24 increases and the polarization conversion efficiency can be further increased.

Considering the use of a tapered rod lens as in the third embodiment, the liquid crystal light valve has a shape close to a square (for example, an aspect ratio of 3 :).
In the case of 4), the exit end surface of the rod lens may be matched to the shape thereof, and only the shape of the entrance end surface may be changed to make the entrance end surface wider (for example, the aspect ratio is 9:16). Thereby, even if the liquid crystal light valve has a shape close to a square, the recycling rate of polarized light can be increased and the polarization conversion efficiency can be increased. Even in this case, if the center of the light incident area is decentered from the center of the incident end surface of the rod lens and the light source optical axis L is tilted from the system optical axis M, the same effect as described above can be obtained.

[Fifth Embodiment] The fifth embodiment of the present invention will be described below.
The embodiment will be described with reference to FIG. The basic configuration of the illumination device of this embodiment is the same as that of the first to third embodiments, and only the configuration of the reflecting mirror on the rod lens incident side and the way of incidence of light from the light source 2 to the rod lens are different. Is. Therefore, in this embodiment, only the configurations of the rod lens and the reflection mirror will be described with reference to FIG. 8, and the description of the other configurations will be omitted.

This embodiment is also similar to the fourth embodiment.
The center of the light incident area 29a is decentered from the center of the incident end surface of the rod lens 28 and is displaced upward in FIG.
However, in the case of the fourth embodiment, the light source optical axis L of the light flux emitted from the light source 2 is inclined with respect to the system optical axis M, whereas in the case of the present embodiment, the light source light The axis L is shifted in parallel with the system optical axis M. Further, the incident end surface of the rod lens 28 is disposed so as to be inclined with respect to the system optical axis M at an angle other than perpendicular.

In the case of this embodiment, the light source optical axis L and the system optical axis M are parallel, but since the incident end face of the rod lens 28 is inclined with respect to the light source optical axis L, the light is incident on the rod lens 28. The incident light beam is refracted at the time of incidence and is incident on the reflection type polarizer 5 at a predetermined angle, and this light is reflected toward the side having a wider area of the reflection mirror 29. The polarization conversion efficiency can be further enhanced, as in the case of (1). Further, since the optical axis L of the light source and the optical axis M of the system are parallel to each other, there is an advantage that the optical system can be easily downsized.

[Sixth Embodiment] The sixth embodiment of the present invention will be described below.
An embodiment will be described with reference to FIGS. 9 and 10. The basic configuration of the illumination device of this embodiment is the same as that of the first to fifth embodiments, and only the configuration of the rod lens is different. Therefore, in the present embodiment, only the configuration and action of the rod lens will be described with reference to FIGS. 9 and 10, and description of the other configurations will be omitted.

While the rod lens 21 of the third embodiment has a taper shape which is tapered in both the vertical and horizontal directions, the rod lens 27 of the present embodiment has only a lateral (X) direction. It has a tapered shape and is not thin in the vertical direction (Y direction). With this structure, as described in the section of the third embodiment, the emission angle θ _{2 of the} light emitted from the rod lens 27 expands in the horizontal direction but does not expand in the vertical direction. . That is,
The illumination angle distribution of the light emitted from the rod lens 27 has a horizontally long (long in the X direction) elliptical shape.

Here, paying attention to the viewing angle characteristic of the liquid crystal light valve which is the illuminated region, the viewing angle characteristic of the liquid crystal light valve does not always show symmetry, and for example, the clear viewing direction is 6
In a TN mode liquid crystal light valve at 12:00 or 12:00, as shown in FIG. 10B, the isocontrast curve is often narrow in the vertical direction and wide in the horizontal direction. When the liquid crystal light valve has the viewing angle characteristic as shown in FIG. 10B, the contrast when the one having the characteristic as shown in FIG. 10A is used as the illumination angle distribution of the light that illuminates the liquid crystal light valve. Therefore, a high contrast part can be used, and a high contrast can be obtained.

From this point of view, when the illuminating device according to the present embodiment is applied to a projector, by using the rod lens 27 having a taper shape which is tapered only in the lateral direction as shown in FIG. A high contrast can be maintained, and a projector with high display quality can be realized.

[Projector] FIG. 11 is a schematic configuration diagram showing an embodiment of a projector provided with the illumination device of the present invention. In the figure, reference numeral 510 is a light source, 530 is a rod lens, 531 is a reflection mirror, 532 is a reflection type polarizer,
513, 514 are dichroic mirrors (color light separating means), 515, 516, 517 are reflection mirrors, 522.
523 and 524 are liquid crystal light valves (light modulation means), 5
Reference numeral 25 is a cross dichroic prism (color light combining means), 521 is a light guide optical system, and 526 is a projection lens (projection means).

The illumination device 540 comprises a light source 510, a rod lens 530, a reflection mirror 531 and a reflection type polarizer 532. The light source 510 includes a lamp 511 such as a metal halide and a reflector 512 that reflects the light from the lamp. Further, the rod lens 530 is used as a uniform illumination system for making the illuminance distribution of the light source light uniform, and the reflective polarizer 53 is provided on the exit end face of the rod lens 530.
2, a reflection mirror 531 having a circular opening through which a light beam from the light source 510 enters is provided on the incident end surface. A condenser lens 535 is provided on the exit side of the rod lens 530.
However, relay lenses 536 and 537 are provided before and after the dichroic mirrors 513 and 514, and collimating lenses 518R and 518G and a condenser lens 518B are provided on the incident side of the liquid crystal light valve and the incident side of the light guide optical system 521.
Are arranged respectively, and these lenses have the same function as the relay system 6 described in the first embodiment.

The dichroic mirror 513 for reflecting the blue light and the green light reflects the red light L _R of the luminous flux from the light source 510.
And transmits the blue light L _B and the green light L _G. The transmitted red light L _R is reflected by the reflection mirror 517 and enters the red light liquid crystal light valve 522. On the other hand, among the color light reflected by the dichroic mirror 513, the green light L _G is reflected by the dichroic mirror 514 for reflecting green light, and the liquid crystal light valve 52 for green light is reflected.
It is incident on 3. On the other hand, the blue light L _B also passes through the second dichroic mirror 514, passes through the condenser lens 518B, the two reflection mirrors 515 and 516, the relay lens 519 and the collimating lens 520, and enters the blue light liquid crystal light valve 524. To do. The light guiding optical system 521 is a condenser lens 51.
By correcting the optical distance between 8B and the collimating lens 520 and matching the length of the blue optical path with that of other colored light, it has a function of reducing the occurrence of uneven illumination.

Liquid crystal light valves 522, 523, 52
The three color lights modulated by 4 enter the cross dichroic prism 525. This prism is formed by laminating four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface thereof. These dielectric multilayer films combine the three color lights to form light representing a color image. The combined light is a projection lens 52 which is a projection optical system.
6, the image projected on the projection screen 527 and enlarged is displayed.

A high-luminance light source is often used in a projector, and conventionally there was a problem in light resistance and heat resistance. According to this configuration, an illumination device having high polarization conversion efficiency and durability. With the provision of, it is possible to realize a projector with high brightness and high reliability.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the configuration of the illumination device including the light guide optical system 521 is illustrated, but the light guide optical system 521 is not an essential component of the illumination device and may be omitted. Further, the specific description regarding the shapes of the incident end surface and the exit end surface of the rod lens, the configurations of the reflection type polarizer and the reflection mirror, etc. is not limited to the above-mentioned embodiment, and the design can be appropriately changed.

[0065]

As described above in detail, according to the present invention, it is possible to recycle polarized light that cannot pass through the reflection type polarizer and contribute to illumination, and therefore, compared with the conventional illumination device. As a result, the utilization efficiency of polarized light can be improved, and a bright lighting device can be realized. Further, since it is only necessary to dispose a reflection-type polarizer on the exit side and a reflection mirror on the entrance side of the light beam splitting unit that has been used as a uniform illumination system, it is possible to realize an illumination device with a simple configuration and high polarization conversion efficiency. can do. In addition, since the structural birefringent reflective polarizer can be formed by using an inorganic material,
Compared with a conventional polarization conversion system using a retardation plate made of an organic film, it is far superior in light resistance and heat resistance and can realize a stable polarization conversion action. By providing such an illumination device, a highly reliable projector with high brightness can be realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a lighting device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the polarization conversion action in the rod lens of the illumination device.

FIG. 3 is a perspective view showing a structure of a structural birefringent reflective polarizer used in the illumination device.

FIG. 4 is a schematic configuration diagram showing a configuration on a rod lens exit side of a lighting device according to a second embodiment of the present invention.

5A and 5B are perspective views showing a configuration of a rod lens of an illumination device according to a third embodiment of the present invention.

6A and 6B are views for explaining the action of the rod lens of FIGS. 5A and 5B.

FIG. 7 is a perspective view showing a configuration of a rod lens of a lighting device according to a fourth embodiment of the present invention.

FIG. 8 is a perspective view showing a configuration of a rod lens of a lighting device according to a fifth embodiment of the present invention.

FIG. 9 is a perspective view showing a configuration of a rod lens of a lighting device according to a sixth embodiment of the present invention.

FIG. 10A is a diagram showing an illumination angle distribution of light emitted from the rod lens, and FIG. 10B is a view showing viewing angle characteristics of a liquid crystal light valve.

FIG. 11 is a schematic configuration diagram showing an example of a projector of the present invention.

FIG. 12 is a diagram for explaining the principle of a structural birefringent polarizer.

[Explanation of symbols]

1,540 Illumination device 2,510 Light source 3,24,29,531 Reflection mirrors 3a, 24a Opening (light incident area) 4,21,22,25,27,28,530 Rod lens (light beam splitting means) 5, 17,532 Reflective polarizer 7,522,523,524 Liquid crystal light valve (illumination area, light modulating means) 18 First quarter wavelength plate 19 Second quarter wavelength plate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/13357 G02F 1/13357 G03B 33/12 G03B 33/12 F term (reference) 2H049 BA05 BA07 BA42 BA43 BB03 BB61 BB63 BC22 2H052 BA02 BA03 BA07 BA09 BA14 2H088 EA12 HA10 HA18 HA24 HA25 HA28 MA01 MA02 MA04 MA06 MA20 2H091 FA07Z FA17Z FA50Z FD22 FD23 LA16 LA17 LA18

Claims (14)

[Claims] 1. A lighting device comprising: a light source; and a light beam splitting unit that splits a light beam from the light source into a plurality of light beams by using reflection, and emits the light beam. On the exit side of the means, there is provided a polarization conversion means provided with a reflection-type polarizer that transmits a part of polarized light of the light beam incident on the light beam dividing means from the light source and reflects a part of the polarized light. A reflection mirror for reflecting the polarized light reflected by the reflection type polarizer on the incident side of the light beam splitting means, corresponding to an area other than the incident area of the light flux from the light source on the incident end face of the light beam splitting means. An illumination device provided. 2. The illumination device according to claim 1, wherein the reflective polarizer has a function of transmitting one of the linearly polarized lights which are orthogonal to each other and reflecting the other. 3. The illumination device according to claim 2, wherein the reflective polarizer is a structural birefringent polarizer. 4. The reflection-type polarizer has a function of transmitting one of circularly polarized lights having mutually opposite rotations and reflecting the other, and is provided between the light beam splitting means and the reflection-type polarizer. /
The lighting device according to claim 1, wherein a four-wave plate is provided. 5. An additional 1 / on the exit side of the reflective polarizer
The lighting device according to claim 4, wherein a four-wave plate is provided. 6. The light beam splitting means comprises a rod-shaped light guide or a tubular light guide having an inner surface as a reflection surface. Lighting equipment. 7. The light guide body is tapered from the incident side toward the exit side.
The lighting device according to. 8. The lighting device according to claim 6, wherein the light guide body has a shape that is divergent from the incident side toward the exit side. 9. The incident area on the incident end surface of the light beam splitting means has a circular shape, and the reflection mirror is provided in an area outside the circular incident area. The lighting device according to any one of 1. 10. The incident end surface and the exit end surface of the light beam splitting means are both rectangular in shape, and the incident end surface is a more elongated rectangular shape than the exit end surface. The illumination device according to any one of claims 1 to 9. 11. The center of the incident area is eccentric with respect to the center of the incident end surface of the light beam splitting means, and the optical axis of the light beam incident on the light beam splitting means is perpendicular to the incident end surface of the reflective polarizer. The lighting device according to any one of claims 1 to 10, wherein the lighting device forms an angle other than. 12. The center of the incident area is eccentric with respect to the center of the incident end face of the light beam splitting means, the light source optical axis of the light beam from the light source and the system optical axis are arranged in parallel, and the light beam splitting is performed. 2. The entrance end face of the means forms an angle other than perpendicular to the system optical axis.
The lighting device according to any one of claims 1 to 10. 13. The illumination device according to claim 1, an optical modulator that modulates the light emitted from the illumination device, and a light that is modulated by the optical modulator. A projector comprising: a projection unit. 14. The light modulating means comprises a liquid crystal light valve, and a direction in which an illumination angle of an illumination light beam emitted from a light beam splitting means of the illuminating device is widened and a direction in which the liquid crystal light valve has a wide viewing angle are aligned with each other. 14. The projector according to claim 13, wherein the projector is provided.