JP3975948B2 - Illumination device and projection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an illumination device for illuminating a liquid crystal display element and other spatial light modulation devices, and a projection device that projects an image using the spatial light modulation device and the illumination device.
[0002]
[Prior art]
As an illumination device for a liquid crystal projector, one that emits illumination light from a lamp light source into a desired linearly polarized light using a grid-type polarizer is known (for example, see Patent Document 1). In this illumination device, the S-polarized reflected light from the polarizer provided on the exit side is returned to the light source side to reciprocate between the light source side and reenter the exit side polarizer. At this time, since the quarter-wave plate is disposed so as to face the polarizer, the reflected light from the polarizer passes through the quarter-wave plate twice, and from the S-polarized light. The light is converted to P-polarized light and almost passes through the polarizer. In such an illuminating device, the polarization conversion efficiency of illumination light can be increased by the presence of the quarter-wave plate.
[0003]
[Patent Document 1]
JP-A-11-6989 [Problems to be Solved by the Invention]
However, in the above-described illumination device, it is necessary to precisely arrange the light source and the reflecting mirror, which leads to a complicated light source structure and an increase in cost. Moreover, in such an illuminating device, the light from a light source cannot fully equalize. In particular, when an LED or the like is used as a light source, it is not easy to form uniform illumination light because the radiation angle distribution is likely to be biased.
[0004]
Therefore, an object of the present invention is to provide an illumination device that can generate uniform polarized light with high polarization conversion efficiency by a simple optical system.
[0005]
Another object of the present invention is to provide a projection apparatus that can easily and efficiently illuminate and can project a high-quality image by incorporating such an illumination apparatus.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, an illumination device according to the present invention reflects a part of illumination light from a light source that generates illumination light and illumination light, and transmits the remaining light to convert it into polarized light in a specific direction. A polarization conversion element, a scattering member provided on the incident surface side of the polarization conversion element, and light that returns the illumination light reflected by the polarization conversion element to the polarization conversion element again via the scattering member And a return means.
[0007]
In the illumination device, since the scattering member provided on the incident surface side of the polarization conversion element scatters the light passing therethrough, the light reflected by the polarization conversion element is again incident on the polarization conversion element by the light feedback means. In the meantime, the uniformity of the illumination light can be improved. Therefore, the uniformity of the intensity distribution and the emission angle of the illumination light emitted from the polarization conversion element is improved, and uniform and efficient illumination can be performed on the liquid crystal light valve that is the illumination target.
[0008]
In a specific aspect of the illumination device, the polarization conversion element is a grid-type polarizer in which conductor lines are formed in stripes on a transparent substrate. In this case, stable polarization is possible with a grid-type polarizer that has a simple structure, durability, and a relatively gradual incidence angle, so that the illumination light emitted from the polarization conversion element can be stable over a long period of time. Can be made.
[0009]
Moreover, in another specific aspect of the illumination device, the scattering member has a surface unevenness pattern formed on the back surface of the transparent substrate. In this case, the processing of the scattering member is simple, and the manufacture of the lighting device is simplified compared to the case where the scattering member is provided individually.
[0010]
In another specific aspect of the illumination device, the surface uneven pattern is an aggregate including at least one of a lens-shaped protrusion and a recessed portion. In this case, by adjusting the arrangement and shape of the lens-like protrusions or depressions, a desired scattering state can be easily realized, and the controllability of illumination for a liquid crystal light valve or the like can be improved.
[0011]
In another specific aspect of the lighting device, the surface uneven pattern is an aggregate including at least one of a cone-shaped protrusion and a recessed portion. In this case, a desired scattering state can be easily realized by adjusting the arrangement and shape of the cone-shaped protrusions or depressions, and the controllability of illumination on the liquid crystal light valve or the like can be improved.
[0012]
In another specific aspect of the illumination device, a wave plate for changing a polarization state of reflected light from the polarization conversion element is further provided between the polarization conversion element and the light feedback means. In this case, when the light reflected by the polarization conversion element is returned to the polarization conversion element by the optical feedback means, it can be converted into polarized light that efficiently passes through the polarization conversion element. Efficient removal is possible.
[0013]
In another specific aspect of the illumination device, the light feedback means is a concave reflecting mirror that collects the illumination light emitted from the light source. In this case, since the reflected light from the polarization conversion element is returned to the polarization conversion element again while condensing the illumination light, the distribution of the emission angle of the illumination light can be made within a certain range.
[0014]
In another specific aspect of the illuminating device, an optical integrator is further provided that causes the illumination light from the light source to be incident on the polarization conversion element via the scattering member in a state where the illumination light is divided and superimposed. In this case, since the light from the light source is wavefront-divided and superimposed by the optical integrator, it is possible to improve the uniformity of the intensity distribution and the emission angle distribution of the illumination light emitted from this apparatus.
[0015]
Moreover, the 1st projection apparatus which concerns on this invention is the projection optical system which projects the image light from the above-mentioned illuminating device, the spatial light modulation device illuminated with the illumination light from an illuminating device, and a spatial light modulation device. Is provided. Here, the “spatial light modulation device” is an optical device represented by, for example, a liquid crystal light valve.
[0016]
In the first projection device, since the spatial light modulation device is illuminated using the above-described illumination device, uniform polarized light can be efficiently generated, and a high-quality image can be projected by an inexpensive device. it can.
[0017]
Further, a second projection device according to the present invention includes a plurality of image forming units for each color each having the above-described illumination device and a spatial light modulation device illuminated by illumination light from the illumination device, and a plurality of images. A light combining member that combines and emits image light from the forming unit, and a projection optical system that projects the image light combined through the light combining member.
[0018]
In the second projection apparatus, since the spatial light modulation apparatus is illuminated using the above-described illumination apparatus, uniform polarized light can be efficiently generated for each color, and a high-quality color image can be generated by an inexpensive apparatus. Can project.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
FIG. 1 is a block diagram conceptually illustrating the structure of the projection apparatus according to the first embodiment. The projection device, that is, the projector 10 includes an illumination device 20, a light modulation device 30, a projection lens 40, and a control device 50. Here, the illumination device 20 includes an R light illumination device 21, a G light illumination device 23, a B light illumination device 25, and a light source driving device 27. The light modulation device 30 outputs drive signals to the three liquid crystal light valves 31, 33, and 35 that are spatial light modulation devices, the cross dichroic prism 37 that is a light combining member, and the liquid crystal light valves 31, 33, and 35. And an element driving device 38. The R light illumination device 21 and the liquid crystal light valve 31 are collectively called an image forming unit. Similarly, the units of the G light illumination device 23 and the liquid crystal light valve 33 and the units of the B light illumination device 25 and the liquid crystal light valve 35 are also referred to as image forming units.
[0020]
FIG. 2 is a diagram illustrating the structure of the R light illumination device 21 in the illumination device 20. The R light illuminating device 21 is fixed to the light source 21a that generates R light among the three primary colors, the concave reflecting mirror 21b that condenses the illumination light emitted from the light source 21a to the side, and the opening of the concave reflecting mirror 21b. The (λ / 4) plate 21c, which is the wavelength plate, the rod integrator 21d fixed in a state of being opposed to the concave reflecting mirror 21b across the (λ / 4) plate 21c, and the exit end of the rod integrator 21d And a polarization conversion element 21e connected thereto. Of these, the concave reflecting mirror 21b functions as a light feedback means for returning the reflected light from the polarization conversion element 21e back to the polarization conversion element 21e, and the rod integrator 21d is an optical that splits and mixes the illumination light from the light source 21a.・ It functions as an integrator.
[0021]
Here, the light source 21a is an LED package also called a solid light source, and incorporates a light emitting unit, that is, a diode chip PC. The light beam LF emitted from the diode chip PC while diverging in the front direction is converted into a light beam having a certain spread by the lens portion LP of the light source 21a, and is incident on the rod integrator 21d via the (λ / 4) plate 21c. Incident from the end IP. The light beam LS emitted while diverging from the diode chip PC in the side surface direction is also converted into a light beam having a certain spread by the concave reflecting mirror 21b and is incident on the rod integrator 21d through the (λ / 4) plate 21c. To do.
[0022]
The rod integrator 21d has a structure in which a rectangular cylindrical inner surface is formed as a reflection surface, and the illumination light incident from the incident end IP is divided into wavefronts by internal reflection according to the angle, and the wavefront is divided in this way. The illumination lights are combined in a superimposed manner and are incident on the exit end EP from the inside. Thereby, illumination light with a uniform distribution can be emitted from the emission end EP with a relatively uniform angular distribution within a desired angular range. At this time, the size of the aperture AP of the concave reflecting mirror 21b and the size of the incident end IP of the rod integrator 21d are matched, and reflecting surfaces (not shown) functioning as auxiliary optical feedback means are provided at the four corners of the incident end IP. Thus, the illumination light emitted from the diode chip PC can be coupled to the rod integrator 21d without omission, and the return reflected light LR returned from the polarization conversion element 21e is reflected by the rod integrator 21d and the concave reflecting mirror 21b. Leakage to the outside can be reliably prevented at the joint with the (λ / 4) plate 21c.
[0023]
The polarization conversion element 21e is composed of a grid-type polarizer that is a kind of a reflective polarizing plate that reflects light that has not been polarized with little absorption. This polarization conversion element 21e has stripe conductors SC, which are made of conductor patterns of equal width and formed at equal intervals on the surface of the transparent substrate TP, and are also called wire grids. Since the width and interval of the stripe conductor SC are set to be equal to or less than the wavelength of the R light, of the light incident on the polarization conversion element 21e, polarized light perpendicular to the specific direction in which the stripe conductor SC extends (hereinafter referred to as P for convenience). Only the polarization conversion element 21e selectively passes through the polarization conversion element 21e.
[0024]
On the incident surface side of the polarization conversion element 21e, that is, the back surface side of the transparent substrate TP, a scattering member 21g in which lens-like microprojections PP are randomly arranged at an appropriate density is formed. The scattering member 21g is for scattering light passing through the scattering member 21g in a random direction. For this reason, the light that passes through the scattering member 21g and enters the polarization conversion element 21e has a relatively uniform angular distribution within a certain incident angle range. In addition, the light that passes through the scattering member 21g in the reverse direction and enters the rod integrator 21d also has a relatively uniform angular distribution within a certain incident angle range, and the rod integrator 21d is moved backward. In the plane perpendicular to the axis of 21d, the two-dimensional distribution of the brightness of the illumination light is further uniformized. In particular, when a solid-state light source such as an LED is used as the light source 21a, the illumination light emitted from the light source often has a certain pattern. Therefore, by arranging the scattering member 21g in front of the polarization conversion element 21e, the polarization conversion element The illumination light incident on 21e can be made uniform effectively. Since the polarization conversion element 21e is a wire grid polarization element, the allowable range of the incident angle of illumination light incident on the polarization conversion element 21e is wide. Therefore, according to such a polarization conversion element 21e, it is possible to extract P-polarized light with little polarization of S-polarized light and high polarization conversion efficiency even if the illumination light has various angles to some extent.
[0025]
The scattering member 21g can be formed as follows, for example. First, a resist film is applied to the back surface side of the transparent substrate TP of the polarization conversion element 21e, and an image of a mask having circular shielding portions that are randomly arranged is projected onto the resist film in a state where the focus is appropriately removed. On the developed resist film, convex portions randomly arranged corresponding to the arrangement of the circular shielding portions of the mask are formed. By removing the resist film processed in this way by dry etching, convex lens-shaped microprojections PP corresponding to the convex portions of the resist film are randomly formed at a desired density.
[0026]
As another method, a glass substrate or a plastic substrate to be the transparent substrate TP is heated to an appropriate softening temperature, and a mold having a transfer surface made up of a large number of minute recesses corresponding to the pattern of the minute protrusions PP is formed on this glass. By pressing against a substrate or a plastic substrate, the microprojections PP to be the scattering members 21g can be stamped on the substrate surface. For example, the stripe conductor SC is formed on the front side of the transparent substrate TP after embossing the minute protrusions PP on the back side. For example, the stripe conductor SC is formed by depositing a metal film on the surface side of the transparent substrate TP, forming a stripe pattern of a resist film thereon, and performing etching using such a stripe pattern as a mask to form the metal film into a number of thin wires. It is formed by processing.
[0027]
The operation of the R light illumination device 21 shown in FIG. 2 will be described. Light beams LF and LS emitted while diverging from the diode chip PC built in the light source 21a in the front direction and the side direction are narrowed to an appropriate divergence angle. (Λ / 4) passes through the plate 21c, goes straight through the rod integrator 21d, or is reflected by the inner surface one or more times and enters the polarization conversion element 21e in a uniform state. As a result, the polarization conversion element 21e is illuminated almost uniformly by the illumination light from the light source 21a. Of the light beams LF and LS incident on the polarization conversion element 21e, the light that has passed through the polarization conversion element 21e is output light of only P-polarized light. On the other hand, of the illumination light incident on the polarization conversion element 21e, the light reflected by the polarization conversion element 21e is substantially composed only of S-polarized light. Such reflected light is disposed at the incident end IP of the rod integrator 21d. The light passes through the (λ / 4) plate 21c and is converted into circularly polarized light. The circularly polarized reflected light that has passed through the (λ / 4) plate 21c is returned to the concave reflecting mirror 21b. The concave reflecting mirror 21b re-enters the polarization conversion element 21e by reflecting the return reflected light LR from the polarization conversion element 21e one or more times. At this time, the circularly polarized light reflected by the concave reflecting mirror 21b is maintained in the circularly polarized state although the rotation direction is reversed, and passes when it reenters the polarization conversion element 21e through the rod integrator 21d (λ / 4). ) The circularly polarized light is converted to P polarized light by the plate 21c. As a result, the return reflected light LR re-entering the polarization conversion element 21e efficiently passes through the polarization conversion element 21e. As a result, the illumination light emitted from the light source 21a is almost completely converted into P-polarized light and emitted as output light from the emission side of the polarization conversion element 21e.
[0028]
In this case, the concave reflecting mirror 21b and the rod integrator 21d function as an optical confinement container, and the illumination light emitted from the light source 21a is incident on the polarization conversion element 21e without omission and is converted into P-polarized light by the polarization conversion element 21e. The return reflected light LR that has not been generated is superimposed while being divided into wavefronts with low loss, and is incident again on the polarization conversion element 21e. In addition, since the scattering member 21g appropriately scatters the light incident on or reflected by the polarization conversion element 21e, the illumination uniformity of the polarization conversion element 21e can be further improved. That is, the uniformity of the intensity distribution and the emission angle of the illumination light emitted from the polarization conversion element 21e is increased, and the liquid crystal light valve 31 can be illuminated uniformly and efficiently.
[0029]
As is clear from the above description, according to the R light illuminating device 21, the illumination light emitted from the light source 21a is converted into an extremely uniform and high-intensity P-polarized output light and emitted. As a result, not only can the subsequent liquid crystal light valve 31 be illuminated uniformly, but also the heat generated by the polarizing plate or the like disposed in the vicinity thereof can be reduced.
[0030]
The uniformity of the output light and the incident angle range to the liquid crystal light valve 31 can be appropriately adjusted by appropriately adjusting the arrangement of the light source 21a, the focal length of the concave reflecting mirror 21b, the length of the rod integrator 21d, and the like. it can. Also, the incident angle range of the illumination light incident on the polarization conversion element 21e can be adjusted as appropriate by appropriately adjusting the radius of curvature of the minute protrusions PP constituting the scattering member 21g.
[0031]
In the above description, only the structure of the R light illumination device 21 in the illumination device 20 of FIG. 1 has been described, but the G light illumination device 23 and the B light illumination device 25 also have some design specifications according to the emission wavelength. It has basically the same structure as the R light illuminating device 21 only by being changed.
[0032]
That is, the G light liquid crystal light valve 33 is illuminated very uniformly by the G light from the G light illuminating device 23, but the illumination light at this time almost completely radiates the G light from the LED package which is a solid state light source. Efficiently converted to P-polarized light. Further, the B light liquid crystal light valve 35 is illuminated very uniformly by the B light from the B light illumination device 25, but the illumination light at this time almost completely converts the B light from the LED package, which is a solid light source. Efficiently converted to P-polarized light.
[0033]
The light from the illuminating devices 21, 23, 25 of the respective colors incident on the liquid crystal light valves 31, 33, 35 is two-dimensionally modulated by the liquid crystal light valves 31, 33, 35, respectively. The light of each color that has passed through each of the liquid crystal light valves 31, 33, and 35 is combined by a cross dichroic prism 37 that is a light combining member and emitted from one side surface. The combined light image emitted from the cross dichroic prism 37 enters the projection lens 40 which is a projection optical system and is projected at a suitable magnification on a screen (not shown) provided outside the projector 10. That is, the projector 10 projects a color image obtained by combining the images of the respective colors R, G, and B appropriately formed on the liquid crystal light valves 31, 33, and 35 on the screen. Although not shown in the drawing, polarizing plates are arranged at appropriate positions in the vicinity of the liquid crystal light valves 31, 33, 35 in order to illuminate and read the liquid crystal light valves 31, 33, 35 with polarized light. ing.
[0034]
The control device 50 is composed of a microcomputer or the like, and outputs control signals to the light source driving device 27 and the element driving device 38 to operate the light illumination devices 21, 23, 25 and liquid crystal light valves 31, 33, 35 of the respective colors. Is controlled indirectly. Thus, for example, a color moving image or still image is projected and displayed on the screen with high luminance in accordance with an image signal input to the projector 10 from the outside via the control device 50, for example.
[0035]
[Second Embodiment]
Hereinafter, the projector according to the second embodiment will be described. The projector according to the second embodiment is a modification of the illumination devices 21, 23, 25 of the projector according to the first embodiment.
[0036]
FIG. 3 is a diagram illustrating a part of the R light illumination device incorporated in the projector according to the second embodiment. This R light illuminating device includes a scattering member 121g on the incident surface side of the polarization conversion element 21e. However, unlike the first embodiment shown in FIG. 2, the conical minute protrusions PP ′ are formed at an appropriate density. Randomly arranged. The light that passes through the scattering member 121g and enters the polarization conversion element 21e has a relatively uniform incident angle distribution within a desired incident angle range. Further, the light that passes through the scattering member 121g and returns to the rod integrator 21d (see FIG. 2) also has a relatively uniform incident angle distribution within a certain incident angle range. As a result, the uniformity of illumination of the polarization conversion element 21e can be increased, the intensity distribution of the illumination light emitted from the polarization conversion element 21e and the uniformity of the emission angle are increased, and the liquid crystal light valve 31 is uniform and efficient. Lighting is possible.
[0037]
Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments. For example, in the first embodiment and the second embodiment, a grid-type polarizer is used as the polarization conversion element 21e. Instead, a polarization conversion element composed of an array of polarization beam splitters or other reflective polarizing plates is used. be able to.
[0038]
In the above embodiment, the rod integrator 21d is provided between the concave reflecting mirror 21b and the polarization conversion element 21e. However, the rod integrator 21d is omitted and the concave reflecting mirror 21b and the polarization conversion element 21e are directly connected. You can also In this case, the lighting device for each color can be reduced in size. At this time, the concave reflecting mirror 21b functions as an optical confinement container or an optical integrator, and makes the illumination light emitted from the light source 21a enter the polarization conversion element 21e without omission and is converted into P-polarized light by the polarization conversion element 21e. The return reflected light LR that has not been generated is superimposed while being divided into wavefronts with low loss, and is incident again on the polarization conversion element 21e. When the rod integrator 21d is left, the presence of the scattering members 21g and 121g makes it possible to shorten the rod integrator 21d while maintaining the uniformity of illumination. Therefore, it is possible to reduce the size of the illumination device and thus the projection device. it can.
[0039]
In the above-described embodiment, output light from the polarization conversion element 21e is directly incident on the liquid crystal light valve 31, but an appropriate relay lens can be inserted between them.
[0040]
In the projector 10 of the above-described embodiment, the light modulation device 30 is configured by the transmissive liquid crystal light valves 31, 33, and 35. However, it can be configured by a reflective liquid crystal element. Further, the liquid crystal light valve can be an optical writing type liquid crystal light valve or the like.
[0041]
Moreover, in the said embodiment, although the light source is comprised using LED, it replaced with LED and other solid light sources, such as EL light emitting element and LD, can also be used.
[0042]
Further, the scattering member 21g incorporated in the apparatus of the first embodiment can have a lens-shaped minute recess, that is, a minute concave surface, instead of the lens-shaped minute protrusion PP, and the second embodiment. The scattering member 121g in the form may also have a conical or pyramid minute concavity instead of the conical minute protrusion PP ′. Moreover, a scattering member shall consist of an aggregate | assembly which mixed the unevenness | corrugation of various shapes and sizes. Further, the scattering member can be constituted by a stripe pattern in which large and small ridges having a hemispherical section or a wedge-shaped section are randomly arranged in the short direction.
[0043]
Further, the scattering members 21g and 121g are not limited to the above methods, and can be manufactured by various methods. For example, random and minute protrusions can be formed here by treating the back surface of the transparent substrate TP with a chemical or mechanically processing it with an abrasive. Further, a scattering plate provided with a large number of random microprotrusions PP and PP ′ can be separately prepared, and this scattering plate can be attached to the back surface of the transparent substrate TP of the polarization conversion element 21e.
[Brief description of the drawings]
FIG. 1 is a diagram showing a structure of a projector according to a first embodiment.
FIG. 2 is a diagram illustrating the structure of a light illumination device in the device of FIG.
FIG. 3 is a diagram illustrating a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Projector 20 Illuminating device 21 R light illuminating device 23 G light illuminating device 25 B light illuminating device 21a Light source 21b Concave reflector 21c ((lambda) / 4) board 21d Rod integrator 21e Polarization conversion element 21g Scattering members 31, 33, 35 Liquid crystal light Valve 37 Cross dichroic prism 40 Projection lens 50 Control device PP Small protrusion SC Striped conductor TP Transparent substrate

Claims (8)

A light source that generates illumination light;
A polarization conversion element that reflects a part of the illumination light from the light source and transmits the remaining light to convert it into polarized light in a specific direction;
A scattering member which is provided on the incident surface side of the polarization conversion element and scatters light passing therethrough;
Light feedback means for returning the illumination light reflected by the polarization conversion element to the polarization conversion element again via the scattering member;
The polarization conversion element is a grid-type polarizer in which conductor lines are formed in a stripe shape on a transparent substrate,
The said scattering member has the surface uneven | corrugated pattern formed in the back surface of the said transparent substrate, The illuminating device characterized by the above-mentioned. The lighting device according to claim 1 , wherein the surface uneven pattern is an aggregate including at least one of a lens-shaped protrusion and a recessed portion. The lighting device according to claim 1 , wherein the surface uneven pattern is an aggregate including at least one of a conical protrusion and a recessed portion. Between the optical feedback means and the polarization conversion element, any one of claims 1 to 3, characterized by further comprising a wave plate for changing the polarization state of the reflected light from the polarization conversion element The lighting device described. The illumination device according to any one of claims 1 to 4, wherein the light feedback means is a concave reflecting mirror that collects illumination light emitted from the light source. 6. The optical integrator according to claim 1 , further comprising an optical integrator that causes the illumination light from the light source to be incident on the polarization conversion element via the scattering member in a state where the illumination light is divided and superimposed . The lighting device according to one item . The lighting device according to any one of claims 1 to 6 ,
A spatial light modulator illuminated by illumination light from the illumination device;
A projection apparatus comprising: a projection optical system that projects image light from the spatial light modulator. A plurality of image forming units for each color each having the illumination device according to any one of claims 1 to 6 and a spatial light modulation device illuminated by illumination light from the illumination device;
A light combining member that combines and emits image light from the plurality of image forming units;
A projection apparatus comprising: a projection optical system that projects image light combined through the light combining member.

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