JP2006227361A - Polarized light transformation optical element, lighting system, and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarized light transformation optical element capable of enhancing the availability of light rays with a simple configuration, and to provide a lighting system and a projector. <P>SOLUTION: The optical element includes a polarized light separation section 35 having a polarized light separation surface 35a to separate the exit light emitted from a light source 31, to transmit the polarized light in a specific vibration direction out of the exit light and to reflect the polarized light in the other vibration direction different from the specific vibration direction; a reflection section 36 having a reflection surface 36a to reflect the polarized light component reflected by the polarized light separation surface 35a to a direction approximately parallel to the polarized light transmitted by the polarized light separation surface 35a; and a half-wave plate 37 provided on an optical path of the polarized light in the specific vibration direction or the polarized light in the other vibration direction, wherein the polarized light separation surface 35a is composed of an inorganic material and has a two-dimensional photonic crystal structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarization conversion optical element, an illumination device, and a projector.

  In recent years, the development of information equipment has been remarkable, and the demand for high-resolution, low power consumption and thin display devices has increased, and research and development have been promoted. 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-mentioned needs. As one form of such a liquid crystal display device, a projection type display device (projector) that enlarges and projects an image emitted from a video source including an optical system using a liquid crystal light valve onto a screen through a projection lens is known. . As an illumination device for a projection display device, for example, a device provided with a light source such as a metal halide lamp, an ultrahigh pressure mercury lamp, or a halogen lamp is known.

In order to effectively utilize the irradiation light emitted from such a light source, the projector is provided with a polarization conversion unit (polarization conversion optical element) that aligns the illumination light into s-polarized light or p-polarized light and enters the liquid crystal light valve. (For example, refer to Patent Document 1). For example, a polarization conversion unit that converts illumination light into s-polarized light includes a polarization separation film (polarization separation surface) that separates the illumination light into s-polarized light and p-polarized light, and a phase difference that converts the separated p-polarized light into s-polarized light. Layer (λ / 2 wave plate). As described above, the light converted into the s-polarized light or the p-polarized light in the polarization conversion unit is separated into three color lights of red light (R), green light (G), and blue light (B). The separated color light fluxes are modulated by three liquid crystal light valves corresponding to the respective color lights, synthesized, and projected onto a screen or the like.
JP-A-5-72417

By the way, when using a light source that has a very short arc length as a light source and can be regarded as a point light source in a simulated manner, substantially parallel light can be incident on the polarization converter. On the other hand, miniaturization by using a solid light source as a light source of a projector has been proposed. Solid light sources, including the power supply, are small in size, can be turned on / off instantaneously, have a wide color reproducibility and have a long lifetime, and have advantages as a projector light source. As described above, in the case of using a light source having a large etendue (the product of area and solid angle, the spatial extent in which an optical beam including an effective light source and a spatial light modulation device is present) is large. This makes it difficult for parallel light to enter the polarization converter, and the light utilization efficiency decreases.
In general, a dielectric multilayer film is used as the polarization separation film, and a polymer material having birefringence is used as the retardation layer. In addition, when a polarization conversion unit having a polarization separation film made of a dielectric multilayer film is used, incidence angle dependency occurs, so depending on the angle of incident light, light absorption occurs in the polarization separation film, The light transmittance and reflectance in the polarization separation film are lowered, and the light utilization efficiency is lowered.

  SUMMARY An advantage of some aspects of the invention is that it provides a polarization conversion optical element, an illumination device, and a projector that can improve light use efficiency with a simple configuration.

In order to achieve the above object, the present invention provides the following means.
The polarization conversion optical element of the present invention separates the emitted light emitted from the light source and transmits the polarized light having a specific vibration direction out of the emitted light, and has a different vibration direction different from the specific vibration direction. A polarization separation unit having a polarization separation surface for reflecting polarized light, and a reflection unit having a reflection surface for reflecting the polarization component reflected by the polarization separation surface in a direction substantially parallel to the polarized light transmitted by the polarization separation surface; A half-wave plate provided on the optical path of the polarized light having the specific vibration direction or the polarized light having the other vibration direction, and the polarization separation surface is made of an inorganic material and has a two-dimensional photo It has a nick crystal structure.

  In the polarization conversion optical element according to the present invention, the light emitted from the light source enters the polarization separation unit and reaches the polarization separation surface. At this time, polarized light in a specific vibration direction among the light reaching the polarization separation surface is transmitted, whereas light in other vibration directions other than the specific vibration direction is reflected by the polarization separation surface and reflected. Head to the club. The light directed toward the reflection surface of the reflection unit is reflected in a direction substantially parallel to the polarized light that vibrates in a specific direction transmitted by the polarization separation surface. When a half-wave plate is disposed on the optical path of polarized light in other polarization directions, the polarized light in other vibration directions is converted into a specific vibration direction and emitted from the polarization conversion optical element. Are aligned with polarized light in a specific vibration direction. On the other hand, when a half-wave plate is disposed on the optical path of polarized light having a specific polarization direction, the light emitted from the polarization conversion optical element is aligned with polarized light having another vibration direction. Since the polarization separation surface is made of an inorganic material and has a two-dimensional photonic crystal structure, the polarization conversion has excellent heat resistance and hardly causes light absorption compared to a conventional dielectric multilayer film. An optical element can be obtained. In other words, since it is possible to reduce the incident angle dependency of the light incident on the polarization separation surface, it is possible to reflect the light emitted from the light source to the transmission and reflection surfaces without reducing the amount of light, and to improve the light utilization efficiency. Can be increased.

In the polarization conversion optical element of the present invention, it is preferable that the half-wave plate is made of an inorganic material.
In the polarization conversion optical element according to the present invention, since the half-wave plate is made of an inorganic material in addition to the polarization separation surface, the light resistance is improved. Therefore, even when the incident light intensity is large, the incident polarized light It becomes possible to stably convert light into desired polarized light.

In addition, the polarization conversion optical element of the present invention preferably includes a substrate on which the polarization separation surface is formed, a substrate on which the reflection surface is formed, and a frame body that detachably holds the substrates. .
In the polarization conversion optical element according to the present invention, each substrate can be fitted into a frame that detachably holds the substrate, so that the polarization separation unit and the reflection unit can be replaced according to the application. Therefore, a polarization conversion optical element having desired polarization characteristics can be produced with a simple configuration.

In the polarization conversion optical element of the present invention, the polarization separation unit is formed of a triangular prism, the polarization separation surface is formed on the inclined surface of the triangular prism, and the inclined surface is 45 with respect to the optical axis of incident light. It is preferable that they are arranged at an angle of inclination.
In the polarization conversion optical element according to the present invention, by forming a polarization separation surface on the inclined surface of the triangular prism, the light reflected by the reflection surface after being reflected by the polarization separation unit and the light transmitted by the polarization separation unit are desired. It is possible to inject within the range. Thus, since it has an effect which collimates incident light, it becomes possible to improve the utilization efficiency of light.

An illumination device of the present invention includes the polarization conversion optical element described above and a light source that emits light to the polarization conversion optical element.
In the illuminating device according to the present invention, since the polarization conversion optical element that can reduce the incident angle dependency is used, the utilization efficiency of the light emitted from the light source can be improved.

Moreover, it is preferable that the illuminating device of this invention is equipped with a light beam width | variety conversion means on the optical path by the side of the incident end surface of the said polarization conversion optical element.
In the illuminating device according to the present invention, the light beam width converting means is provided on the optical path on the incident end face side of the polarization conversion optical element, so that the light beam emitted from the light source is narrowed down to the polarization separation unit of the polarization conversion optical element. Since the light is incident, it is possible to suppress the loss of light and improve the light utilization efficiency.

  A projector of the present invention includes the above-described illumination device, a spatial light modulation device that modulates light emitted from the illumination device according to an image signal, and a projection device that projects light modulated by the spatial light modulation device. It is characterized by providing.

  In the projector according to the present invention, the light emitted from the illumination device enters the spatial light modulation device. Then, the image modulated by the spatial light modulation device is projected by the projection device. At this time, since the light emitted from the illumination device is aligned with the light that vibrates in a specific direction as described above, the amount of light is not reduced when passing through the spatial light modulation device. The ratio can be maintained and an image with uniform brightness can be projected.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

A first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the projector 1 according to the present embodiment is a so-called front type projector that projects light according to an image signal onto a screen 42 and observes a projected image from the same side as the projector 1 with respect to the screen 42. is there.

  The projector 1 includes an R light illumination device (illumination device) 10R that emits red light (hereinafter referred to as “R light”) and a G light illumination that emits green light (hereinafter referred to as “G light”). A device (illumination device) 10G, a B light illumination device (illumination device) 10B for emitting blue light (hereinafter referred to as “B light”), and R emitted from each of the illumination devices 10R, 10G, and 10B. Transmission type liquid crystal light valves (spatial light modulators) 20R, 20G, and 20B that modulate the luminance of G and B according to an image signal, a dichroic prism 40 that combines the modulated color lights into a color image, and a dichroic A projection lens (projection device) 41 that projects a color image emitted from the prism 40 onto a screen 42 is provided.

The R light illumination device 10R includes a light source unit 11R and a rod integrator 21R provided on an emission end surface of the light source unit 11R. Similarly, the G light illumination device 10G and the B light illumination device 10B include light source units 11G and 11B and rod integrators 21G and 21B, respectively.
The rod integrator 21R is made of a transparent member such as solid glass or resin, and guides light emitted from the light source unit 11R to the transmissive liquid crystal light valve 20R and repeats total internal reflection. The illuminance distribution of the light emitted from the light source unit 11R is made substantially uniform.

  As shown in FIG. 2, the light source unit 11 </ b> R includes an R light LED (light source) 31 </ b> R that is a light emitting unit that emits light, and a collimator lens (parallelizing optics) that substantially parallelizes the light emitted from the R light LED 31 </ b> R. System) 32, a polarization conversion optical element 33 that transmits polarized light having a specific vibration direction among the light transmitted through the collimator lens 32, and reflects polarized light having another vibration direction different from the specific vibration direction, and polarized light And a condensing lens 34 for allowing the light transmitted through the conversion optical element 33 to enter the rod integrator 21R.

  The polarization conversion optical element 33 separates the emitted light emitted from the R light LED 31R and transmits polarized light in a specific vibration direction out of the emitted light, and polarization in another vibration direction different from the specific vibration direction. A cubic polarization separation unit 35 having a polarization separation surface 35a for reflecting light, and a reflection surface 36a for reflecting the polarization component reflected by the polarization separation surface 35a in a direction substantially parallel to the polarized light transmitted by the polarization separation surface 35a. And a half-wave plate 37 provided on the optical path of polarized light in a specific vibration direction.

Next, the polarization separation surface 35a of this embodiment will be described.
The polarization separation surface 35a is a wire grid type polarization filter, and is made of an inorganic material and has a two-dimensional photonic crystal structure as shown in FIG.
Specifically, the polarization separation surface 35a is a kind of structural birefringent polarizing plate, and has a structure in which fine ribs 41 extending in a predetermined direction are formed on a metal thin film formed on the glass substrate 40. ing. This metal thin film can be formed by vapor deposition or sputtering using aluminum, tungsten, or the like. The fine rib 41 can be formed by combining two-beam interference exposure method, electron beam drawing method, X-ray lithography method, and the like with etching. The pitch of the fine ribs 41 is shorter than the wavelength of light to be reflected. Thereby, the linearly polarized light parallel to the fine ribs 41 can be reflected and the linearly polarized light in the vertical direction can be transmitted. Since this wire grid type polarizing filter has a simple structure, it can be easily manufactured.

  The polarization separation unit 35 transmits polarized light having a specific vibration direction, for example, p-polarized light, and reflects polarized light having another vibration direction different from the specific vibration direction, for example, s-polarized light. The s-polarized light reflected by 35a is reflected toward the reflecting surface 36a of the reflecting portion 36.

Furthermore, as shown in FIG. 2, the polarization separation unit 35 is disposed on the optical axis O of the light emitted from the R light LED 31R. In addition, the polarization separation surface 35a provided in the polarization separation unit 35 and the reflection surface 36a provided in the reflection surface 36 are arranged with an inclination of 45 degrees with respect to the optical axis O and are substantially parallel to each other. It is arranged.
The reflecting surface 36a is made of a member having a high light reflectance, for example, a metal member such as aluminum or silver. Further, the half-wave plate 37 is provided in direct contact with the emission end face 36 b of the reflecting portion 36.

  The light source unit 11G has a G light LED 31G instead of the R light LED 31R, and the light source unit 11B has a B light LED 31B instead of the R light LED 31R. It has the same composition as.

  As shown in FIG. 1, the R light emitted from the rod integrator 21R enters the transmissive liquid crystal light valve 20R. The cross section of the portion where the light of the rod integrator 21R propagates has substantially the same shape as the modulation region of the transmissive liquid crystal light valve 20R. The transmissive liquid crystal light valve 20R is a transmissive liquid crystal display device that modulates R light according to an image signal, and the light modulated by the transmissive liquid crystal light valve 20R is a dichroic prism that is a color synthesis optical system. 40 is incident.

  The light emitted from the light source unit 11G of the G light illumination device 10G is incident on the transmissive liquid crystal light valve 20G by the rod integrator 21G. The transmissive liquid crystal light valve 20G is a transmissive liquid crystal display device that modulates G light according to an image signal, and the light modulated by the G light spatial light modulator 20G is a color synthesis optical system. The light enters the dichroic prism 40.

  Similarly, the light emitted from the light source unit 11B of the B light illumination device 10B is incident on the transmissive liquid crystal light valve 20B by the rod integrator 21B. The transmissive liquid crystal light valve 20B is a transmissive liquid crystal display device that modulates G light according to an image signal, and the light modulated by the B light spatial light modulator 20B is a color synthesis optical system. The light enters the dichroic prism 40.

  The dichroic prism 40 includes a dichroic film that reflects B light and transmits R light and G light, and a dichroic film that reflects R light and transmits B light and G light. Configured. The dichroic prism 40 combines the R light, G light, and B light modulated by the spatial light modulators 20R, 20G, and 20B, respectively. The light synthesized by the dichroic prism 40 is projected onto the screen 42 by the projection lens 41.

Next, a method for projecting an image onto the screen 42 using the projector 1 of the present embodiment having the above configuration will be described.
Since the operation for each color light emitted from the R light LED 31R, the G light LED 31G, and the B light LED 31B is the same, the operation for the red light emitted from the R light LED 31R will be described. The description of the action of green light and blue light is omitted.

First, when a current is supplied to the R light LED 31R of the R light illumination device 10R, red light is emitted from the R light LED 31R toward the collimator lens 32 as shown in FIG.
The red light incident on the collimator lens 32 is collimated and incident on the polarization conversion optical element 33. Then, only the p-polarized light is transmitted through the polarization separation surface 35 a of the polarization separation unit 35, and the s-polarized light is reflected toward the reflection surface 36 a of the reflection unit 36. The s-polarized light reflected by the reflecting surface 36a travels substantially in parallel with the p-polarized light transmitted through the polarization separating surface 35a because the polarization separating surface 35a and the reflecting surface 36a are arranged substantially in parallel. Next, when the s-polarized light is emitted from the emission end face 36 b of the reflecting portion 36, it is converted into p-polarized light by the half-wave plate 37 and emitted. In this way, the light transmitted through the polarization separation surface 35a of the polarization separation unit 35 and the light emitted from the exit end surface 36b of the reflection unit 36 are light having the same polarization direction. Thereafter, the light whose polarization direction is aligned is made uniform in illuminance distribution by the rod integrator 21R, emitted from the rod integrator 21R, and then incident on the transmissive liquid crystal light valve 20R. Then, it is modulated based on the video signal input to the projector 1 and emitted toward the dichroic prism 40.

  Similarly, p-polarized light of green light and p-polarized light of blue light modulated based on the video signal are also incident on the dichroic prism 40. These color lights are combined by a blue light reflecting dichroic film that reflects blue light and a red light reflecting dichroic film that reflects red light to form light representing a color image and emitted toward the projection lens 41. The projection lens 41 enlarges and projects light representing a color image toward the screen 42 to display a color image.

  Specifically, in this embodiment, a polarization separation surface 35a having incident angle dependency characteristics and wavelength dependency characteristics as shown in FIG. 4 is used. This is the case where the incident angle (the angle formed by the optical axis O of the p-polarized light or s-polarized light incident on the polarization separation surface 35a and the polarization separation surface 35a) is 45 degrees (solid line) and 30 degrees (dashed line). The characteristic in is shown. As can be seen from FIG. 4, with respect to p-polarized light, the transmittance is a stable value of approximately 0.9 over a wide wavelength range in both cases where the incident angle is 45 degrees and 30 degrees. For s-polarized light, the transmittance is 0 over a wide wavelength range. Therefore, it can be seen that there is almost no variation in transmittance with respect to the incident angle.

(Comparative example)
Here, as a comparative example for explaining the incident angle dependency characteristic and wavelength dependency characteristic of the polarization separation surface 35a of the present invention, the characteristic of a conventional structure, that is, a PBS (polarization beam splitter) formed of a dielectric multilayer film is illustrated. This is shown in the graph of FIG.
As can be seen from FIG. 5, for p-polarized light, the transmittance is approximately 1.0 when the incident angle is 45 degrees (solid line), but the transmittance when the incident angle is 30 degrees (dashed line). And the transmittance is 0.8 or less depending on the incident wavelength band. For s-polarized light, the transmittance is substantially 0 when the incident angle is 45 degrees, but when the incident angle is 30 degrees, the transmittance varies greatly, and the transmittance varies depending on the incident wavelength band. Exceeds 0.1. Therefore, since there is a variation in transmittance with respect to the incident angle, it is difficult to obtain stable characteristics.

  According to the projector 1 and the illumination devices 10R, 10G, and 10B according to the present embodiment, the polarization separation surface 35a of the polarization conversion optical element 33 is made of an inorganic material and has a two-dimensional photonic crystal structure. Compared to a dielectric multilayer film, it is extremely excellent in heat resistance and hardly absorbs light. Further, since the incident angle dependency of the light incident on the polarization separation surface 35a can be reduced, it is possible to reflect the light emitted from the R light LED 31R to the transmission and reflection surface 36a without reducing the light amount. Become.

(Second Embodiment of Projector)
Next, a second embodiment according to the present invention will be described with reference to FIG. In each embodiment described below, portions having the same configuration as those of the projector 1 according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.
In the projector according to the present embodiment, the second embodiment differs from the first embodiment in the configuration of the polarization conversion optical element 50.

The polarization conversion optical element 50 includes a hollow frame 60 having a polarization separation part 51 and a reflection part 52, and respective substrates 53 and 54 on which a polarization separation surface 53a and a reflection surface 54a are formed. Are formed with insertion holes 60a and 60b that can hold the substrates 53 and 54, respectively. Further, the polarization separation unit 51 and the reflection unit 52 are formed integrally with the frame body 60.
In addition, the insertion holes 60a and 60b are arranged with an inclination of 45 degrees with respect to the optical axis O. Further, since the insertion holes 60a and 60b have the same size as the substrates 53 and 54, the substrates 53 and 54 can be held. It has become.

  Furthermore, as shown in FIG. 7, the substrate 53 on which the polarization separation surface 53 a is formed has a rib 56 similar to that of the first embodiment formed on a flat glass substrate 55. Moreover, the board | substrate 54 with which the reflective surface 54a was formed is flat form, and is comprised by members with high light reflectivity, for example, metal members, such as aluminum and silver.

  According to the projector and the illuminating devices 10R, 10G, and 10B according to the present embodiment, by inserting the substrates 53 and 54 into the insertion holes 60a and 60b formed in the hollow frame 60, the polarization separation unit according to the application. 51 and the reflection part 52 can be substituted. Accordingly, the polarization conversion optical element 50 having desired polarization characteristics can be manufactured with a simple configuration.

(Third embodiment of projector)
Next, a third embodiment according to the present invention will be described with reference to FIG.
The projector according to this embodiment is different from the first embodiment in that the polarization separation unit 71 of the polarization conversion optical element 70 is formed of a triangular prism.

The polarization separation unit 71 has a right-angled isosceles triangle in cross section, and the polarization separation surface 72 is bonded to the inclined surface 71a. The polarization separation surface 72 is not limited to adhesion, and may be formed directly. The polarization separation unit 71 is arranged such that the inclined surface 71a is inclined 45 degrees with respect to the optical axis O of the incident light.
Similarly to the polarization separation unit 71, the reflection unit 73 is also formed of a triangular prism, and a reflection surface 74 is formed on the inclined surface 73a. In the present embodiment, the reflecting portion 73 is also composed of a triangular prism. However, the reflecting portion 73 may be a cubic reflecting portion 36 similar to that in the first embodiment.

  According to the projector and the illuminating devices 10R, 10G, and 10B according to the present embodiment, by forming the polarization separation surface 72 on the slope of the polarization separation unit 71, the light incident on the polarization separation unit 71 can be suppressed to a desired range. It can be reflected on the reflecting surface 74. Moreover, since it has the effect of collimating incident light, it becomes possible to improve the light utilization efficiency.

The technical scope of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, the light beam width converting means 80 may be provided on the optical path on the incident end face 35 b side of the polarization separation unit 35 of the polarization conversion optical element 33. As shown in FIG. 9, the light beam width conversion means 80 is composed of two lenses between the R light LED 31R and the polarization separation unit 35, and the light beam width of the light emitted from the R light LED 31R. Overall reduction. By providing such a light beam width conversion means 80, even when the light beam width is wide, the light beam emitted from the R light LED 31R is focused and incident only on the polarization separation unit 35 side. Loss can be suppressed and light utilization efficiency can be improved.
The same effect can be obtained by using the above-described polarization conversion optical elements 50 and 70 instead of the polarization conversion optical element 33. Further, the light beam width conversion means 80 may be constituted by one lens or three or more lenses. Moreover, the structure which reduces the light beam of the light inject | emitted from LED31R for R light in any one direction of a X direction or a Y direction using a cylindrical lens may be sufficient.

The polarization conversion optical elements 33, 50, and 70 are configured such that the half-wave plate 37 is arranged on the optical path of the light reflected by the reflection surfaces 36a, 54a, and 74. A configuration may be adopted in which light is transmitted through the separation surfaces 35a, 53a, and 72 on the optical path. Further, the half-wave plate 37 may be made of an inorganic material, and may have, for example, a two-dimensional photonic crystal structure like the polarization separation surface 35a. In the case of this configuration, the light resistance of the half-wave plate 37 is improved, so that it is possible to stably convert the incident polarized light into desired polarized light even when the intensity of the incident light is large. Become.
In addition, although the light source unit 11R includes the single polarization conversion optical element 33, a configuration in which the light source unit 11R is arrayed in a direction perpendicular to the optical axis O may be employed.
Furthermore, although the reflecting surfaces 36a, 54a, 74 are made of metal members such as aluminum and silver, they are not limited to this and may be made of a metal reflecting film, a dielectric multilayer film, and an inorganic polarizing plate.

  Furthermore, although an LED is used as the light source, a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, a halogen lamp, or the like may be used. When these lamps are used, as shown in FIG. 10, the projector 90 has a first configuration that transmits red light contained in white light emitted from the light source 90a and reflects blue light and green light. The dichroic mirror 91, the reflection mirror 92 that causes the transmitted red light to enter the transmissive liquid crystal light valve 20R, the blue light reflected by the first dichroic mirror 91, the green light is reflected, and the transmissive liquid crystal light valve The second dichroic mirror 93 that is incident on 20G and the reflection mirrors 94 and 95 that allow the transmitted blue light to enter the transmissive liquid crystal light valve 20B are provided. In this configuration, by arranging the above-described polarization conversion optical element 33 between the light source 90a and the first dichroic mirror 91, it is possible to realize the projector 90 with improved light utilization efficiency. Instead of the polarization conversion optical element 33, the polarization conversion optical element 50 or the polarization conversion optical element 70 may be used.

  In each of the above-described embodiments, a transmissive liquid crystal display device is used as the spatial light modulator, but a reflective liquid crystal display device, a digital micromirror device (DMD, registered trademark), or the like can be used. Moreover, although the projection lens 41 was used as a projection apparatus, it is also possible to use a mirror projection system combining several mirrors. Moreover, it is good also as a structure which excluded the rod integrator from the illuminating device. The image display device of the present invention can also be applied to a direct-view display device other than the projection display device such as the projector described above.

1 is a schematic diagram showing a projector according to a first embodiment of the invention. It is a figure explaining the structure of the illuminating device of FIG. It is a figure explaining the polarization splitting surface of FIG. It is a graph which shows the transmittance | permeability characteristic of the polarization splitting surface of FIG. It is a graph which shows the transmittance | permeability characteristic of the conventional polarization splitting surface. It is a perspective view which shows the polarization conversion optical element of the projector which concerns on 2nd Embodiment of this invention. It is a perspective view which shows the board | substrate with which the polarization separation surface of the polarization conversion optical element of FIG. 6 was formed. It is sectional drawing which shows the polarization conversion optical element of the projector which concerns on 3rd Embodiment of this invention. It is a figure which shows the modification of the projector which concerns on each embodiment of this invention. It is the schematic which shows the modification of the projector of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,90 ... Projector, 10R ... R light illumination device (illumination device), 10G ... G light illumination device (illumination device), 10B ... B light illumination device (illumination device), 20R, 20G, 20B ... Transmission type Liquid crystal light valve (spatial light modulation device), 31R ... LED for R light (light source), 31G ... LED for G light (light source), 31B ... LED for B light (light source), 33, 50, 70 ... Polarization conversion optical element 35a ... Polarization separation surface, 35 ... Polarization separation portion, 36a ... Reflection surface, 36 ... Reflection portion, 37 ... Half-wave plate, 41 ... Projection lens (projection device), 60 ... Frame, 53, 54 ... Substrate , 60a, 60b ... insertion hole, 71 ... polarization separation part (prism), 70a ... slope, 80 ... beam width conversion means

Claims (7)

A polarization separation surface that separates the emitted light emitted from the light source, transmits polarized light in a specific vibration direction of the emitted light, and reflects polarized light in another vibration direction different from the specific vibration direction. A polarization separation unit,
A reflecting portion having a reflecting surface that reflects the polarization component reflected by the polarization separating surface in a direction substantially parallel to the polarized light transmitted by the polarization separating surface;
A half-wave plate provided on the optical path of the polarized light in the specific vibration direction or the polarized light in the other vibration direction,
The polarization conversion optical element, wherein the polarization separation surface is made of an inorganic material and has a two-dimensional photonic crystal structure.   The polarization conversion optical element according to claim 1, wherein the half-wave plate is made of an inorganic material. A substrate on which the polarization separation surface is formed;
A substrate on which the reflective surface is formed;
The polarization conversion optical element according to claim 1, further comprising a frame that detachably holds each of the substrates. The polarization separation unit is composed of a triangular prism,
3. The polarized light separation surface is formed on the inclined surface of the triangular prism, and the inclined surface is inclined by 45 degrees with respect to the optical axis of incident light. The polarization conversion optical element described. The polarization conversion optical element according to any one of claims 1 to 4,
An illumination device comprising: a light source that emits light to the polarization conversion optical element.   The illumination apparatus according to claim 5, further comprising a light beam width conversion unit on an optical path on an incident end face side of the polarization conversion optical element. The lighting device according to claim 5 or 6,
A spatial light modulation device that modulates light emitted from the illumination device in accordance with an image signal;
A projector comprising: a projection device that projects light modulated by the spatial light modulation device.

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