JP2002071951A - Polarized light separating element, polarized light converting element and projection display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarized light separating element with which lowering of characteristic can be suppressed even when the incident angles are varied, a polarized light converting element provided with this polarized light separating element, and a projection display using the polarized light converting element. SOLUTION: The polarized light separating element 330 for separating incident light into two kinds of polarized lights is provided with plural translucent substrates 321, 322 and polarized light separating films 20 and reflection films 30 arranged alternately between the plural substrates 321 and 322. The translucent substrates consist of glass substrates 321 and 322 having a high refractive index. Even when the incident angle with respect to the element 330 is deviated and light is made incident, the incident angle approximates to an incident angle set by correcting the incident angle with respect to the films 20, thereby lowering of the separation characteristic of the films 20 can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization separation element for separating incident light into two kinds of polarized light, a polarization conversion element having the polarization separation element, and a projection type using the polarization conversion element. It relates to a display device.

[0002]

2. Description of the Related Art In a projection display device, an element called a light valve is used to modulate light in accordance with an image signal. As the light valve, a type that uses one type of linearly polarized light, such as a transmissive liquid crystal panel or a reflective liquid crystal panel, is often used. In a projection display device using one type of linearly polarized light, from the viewpoint of improving light use efficiency, a polarization conversion element for converting unpolarized incident light emitted from a light source into one type of linearly polarized light is used. May be provided. In this case, the polarization conversion element is a polarization separation element (PBS) for separating incident light into two types of polarized light and a selection for converting one of the two types of polarized light to the other polarized light. A phase difference plate is provided. That is, in the projection display device, the light (non-polarized light) of the lamp is separated into P-polarized light and S-polarized light, and thereafter, all the light from the lamp is converted by converting the P-polarized light into S-polarized light. Align with S-polarized light. Since a polarizing plate that transmits S-polarized light is attached to the light valve (liquid crystal panel), the use efficiency of the light emitted from the lamp is improved by this polarization conversion. Typically, 50% of the light is absorbed by the polarizing plate.)

[0003] The above-mentioned polarized light separating element is composed of an intermediate refractive material (n
= Approximately 1.7) and a low refractive index material (approximately n = 1.4)
The polarization separation film (PBS multilayer film) is composed of a multilayer film (about 40 to 50 layers in total) in which the above layers are alternately stacked. The thickness of each layer of the polarization splitting film is determined based on simulation optimization conditions, and is formed by deposition using a vapor deposition machine. The ideal conditions for the optimization at this time are: P-wave transmittance 100%, S-wave transmittance 0%
(Reflectance: 100%), and the incident angle to the polarization splitting film at that time is set to 45 °.

[0004]

In order to improve the polarization separation characteristics of the above-mentioned polarization separation element, it is necessary to increase the number of layers of the polarization separation film. However, as the number of layers increases, the angle of incidence increases. Dependency increases, and characteristics (transmittance / reflectance) decrease for incident angles other than 45 °.

FIG. 10 shows each incident angle (4
FIG. 11 is a characteristic diagram of the P-wave transmittance at 1 ° to 49 °), and FIG. 11 shows each incident angle (41 ° to 49 °) with respect to the polarization splitting film.
FIG. 7 is a characteristic diagram of the S-wave reflectivity in FIG. In any case, when the incident angle deviates from 45 °, the characteristics are deteriorated.

On the other hand, in the current optical system of the projection display device, it is impossible to make the light emitted from the lamp into a completely parallel light beam, and the light incident on the polarization splitting element varies.
For this reason, the incident light to the polarization splitting film of the polarization splitting element also varies with respect to the set incident angle of 45 °, so that the deterioration of the characteristics cannot be avoided.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a polarized light separating element capable of suppressing a deterioration in characteristics even when the incident angle varies, and a polarized light separating element. It is an object of the present invention to provide a polarization conversion device provided with the device, and a projection display device using the polarization conversion device.

[0008]

Means for Solving the Problems (1) A polarized light separating element according to one aspect of the present invention is a polarized light separating element for separating incident light into two kinds of polarized light, wherein a plurality of transparent light transmitting elements are provided. The light-transmitting substrate includes a substrate, and a polarization separation film and a reflection film alternately arranged between the plurality of light-transmitting substrates. The incident angle of the light on the polarization separation film is set in advance, and the two kinds of polarized light (P-polarized light and S-polarized light) are most efficiently used when the light is incident at the incident angle.
It is designed to be separated. For this reason, when the angle of incidence of light on the polarization separation film deviates from a preset angle of incidence (that is, the angle of incidence on the polarization separation element), the separation characteristics of the polarization separation film deteriorates. Since an optical substrate having a high refractive index is used, it functions to correct the direction of the incident light even if the incident angle with respect to the polarization separating element is shifted (see FIG. 3 described later). The incident angle is corrected and approaches the set incident angle,
Deterioration of the separation characteristics of the polarization separation film is suppressed.

(2) In a polarization beam splitting element according to another aspect of the present invention, the light-transmitting substrate of (1) is formed of a glass substrate having a high refractive index. In the present invention, light incident on the polarization splitting element is incident on the polarization splitting film via a glass substrate having a high refractive index. Then, even if the incident light to the polarization separation element is shifted, the path of the light is corrected by the glass substrate having a high refractive index, and the incidence angle to the polarization separation film is corrected.

(3) The polarization beam splitting element according to another aspect of the present invention is the polarization beam splitting element according to the above (1) or (2),
The refractive index of the translucent substrate is 1.6 or more. In the present invention, by using a translucent substrate having a refractive index of 1.6 or more, even if the incident light to the polarization splitting element is deviated, the path of the light is corrected by the glass substrate having a high refractive index and the polarization separation is performed. The angle of incidence on the film is corrected.

(4) In the polarization beam splitting element according to another aspect of the present invention, in the polarization beam splitting element described in (3) above, the refractive index of the translucent substrate is 1.8 or more. In the present invention, by using a translucent substrate having a refractive index of 1.8 or more, even if the incident light to the polarization splitting element is shifted, the path of the light is corrected by the high refractive index glass substrate so that the polarization separation is performed. The incident angle with respect to the film is further corrected to approach the set incident angle, and a decrease in the separation characteristics of the polarization separation film is suppressed.

(5) The polarization beam splitting device according to another aspect of the present invention is the polarization beam splitting device of (1) to (4), wherein the polarization beam splitting film has a smaller refractive index than the refractive index of the transparent substrate. It has a multilayer structure in which a plurality of first layers having a high refractive index and second layers having a large refractive index are alternately laminated.

(6) A polarization beam splitting element according to another aspect of the present invention is the polarization beam splitting element according to any one of the above (1) to (5), wherein the polarization beam splitting film and the reflection film are arranged with respect to the incident surface of the polarization beam splitting element. Each is arranged at an angle of 45 °. In the present invention, when light is incident, for example, vertically on the incident surface of the polarization separation element, the light is incident on the polarization separation film at an incident angle of 45 °, and transmits, for example, P-polarized light and reflects S-polarized light.
Then, the S-polarized wave enters the reflection film at an incident angle of 45 ° and is reflected in a direction perpendicular to the incident surface of the polarization splitter.

(7) In the polarization beam splitting element according to another aspect of the present invention, in the polarization beam splitting element according to any one of the above (1) to (6), the polarization beam splitting film transmits P-polarized wave out of the incident light, and The polarized light is reflected, and the reflection film reflects the S polarized light. In the present invention, when light is incident on the incident surface of the polarization separation element, the polarization separation film transmits a P-polarized wave and reflects an S-polarized wave. And
The S-polarized wave enters the reflection film and is reflected.

(8) In the polarization beam splitting element according to another aspect of the present invention, in the polarization beam splitting element according to any one of the above (1) to (6), the polarization beam splitting film transmits the S-polarized wave out of the incident light, and The reflecting film reflects the polarized light, and the reflecting film reflects the P polarized light. In the present invention, when light is incident on the incident surface of the polarization separation element, the polarization separation film transmits S-polarized light and reflects P-polarized light. And
The P-polarized wave enters the reflection film and is reflected.

(9) A polarization conversion device according to another aspect of the present invention is a polarization conversion device for converting incident light into one type of polarized light, wherein any one of the above (1) to (8) is used. And a selective retardation plate for converting one of the two types of polarized light from the polarized light separating element into the other polarized light. In the present invention, when light is incident on the polarization separation element, it is divided into two types of polarized light (P-polarized light, S-polarized light).
(Polarized wave). Then, the incident light is converted into one type of polarized light by converting one of the two types of polarized light (for example, an S-polarized wave) into the other type of polarized light (a P-polarized wave) using a selective retardation plate. Output.

(10) A projection display apparatus according to another aspect of the present invention includes a light source unit, a polarization conversion element that converts light emitted from the light source unit into one type of polarized light, The optical system comprises: a modulating means for modulating light based on a given image signal; and a projection optical means for projecting the light modulated by the modulating means, wherein the polarization conversion element comprises the polarization conversion element of the above (9). is there. In the present invention, the polarization conversion element converts light emitted from the light source unit into one type of polarized light,
The modulating means modulates the light from the polarization conversion element based on the given image signal, and the projection optical means projects the light modulated by the modulating means to generate an image. Since the polarization conversion element uses a polarization separation element using a high refractive index transmissive substrate, the incident angle of light with respect to the polarization conversion element is set at a predetermined incident angle (that is, the incident angle with respect to the polarization separation element). Even if it deviates, the incident angle to the polarization separation element functions to be corrected, the incident angle to the polarization separation film is corrected and approaches the set incident angle, and the separation characteristics of the polarization separation film Is suppressed. For this reason, a decrease in brightness and a decrease in color purity of an image generated by the projection optical unit are also suppressed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. FIG. 1 is an explanatory diagram illustrating a polarization conversion element 320 according to Embodiment 1 of the present invention.
FIG. 1A is a plan view of the polarization conversion element 320, and FIG. 1B is a perspective view of the polarization conversion element 320. The polarization conversion element 320 separates the incident light into P-polarized light and S-polarized light and emits the polarized light. The polarization conversion element 320 converts the two types of linearly polarized light separated by the polarization separation element 330 into one type of light. A λ / 2 retardation plate 381 for converting the light into linearly polarized light. The λ / 2 phase plate 381 corresponds to the selected phase plate in the present invention.

The polarization separating element 330 has a shape in which first and second light-transmitting substrates (hereinafter, referred to as “substrates”) 321 and 322 each having a columnar shape having a parallelogram cross section are alternately bonded. ing. Further, between the substrate 321 and the substrate 322, a polarization splitting film (PBS multilayer film) 20 and a reflection film (mirror multilayer film) 30 are alternately arranged.

When light having a random polarization direction including an S-polarized component and a P-polarized component is incident on the polarization splitting film 20 of the polarization conversion element 320 shown in FIG. 1A, the incident light is first polarized. The light is separated into S-polarized light and P-polarized light by the separation film 20. The S-polarized light is reflected by the polarization splitting film 20 at a substantially right angle, and is further reflected by the reflective film 30 at a right angle before being emitted. On the other hand, the P-polarized light passes through the polarization separation film 20 as it is. A λ / 2 phase difference plate 381 is disposed on the exit surface of the P-polarized light that has passed through the polarization splitting film 20, and the P-polarized light is converted into S-polarized light and emitted. Therefore, most of the light that has passed through the polarization conversion element 320 is emitted as S-polarized light. When the light emitted from the polarization conversion element 320 is to be P-polarized light, the λ / 2 retardation plate 381 is arranged on the emission surface from which the S-polarized light reflected by the reflection film 30 is emitted. I just need.

FIG. 2 is an enlarged sectional view showing a part of the polarization splitting film 20. The polarization separating film 20 is formed of a light-transmitting substrate 32.
1 is a dielectric multi-layer film, which is composed of a multi-layer structure part 22 in which two kinds of materials are alternately stacked in a total of 49 layers, and a covering layer 24 formed on the multi-layer structure part 22. I have. The polarization separation film 20 is formed by sequentially laminating one layer on the surface of the substrate 321. The substrate 321 on which the polarization separation film 20 is laminated is bonded to the substrate 322 via the optical adhesive 18. The coating layer 24 has a function of increasing the adhesiveness between the polarization separation film 20 and the substrate 322.

The multilayer structure 22 is formed of a transparent substrate 32
1, a layer having a relatively low refractive index with respect to the substrate (hereinafter, referred to as an L layer) and a layer having a relatively large refractive index (hereinafter, referred to as an H layer) are formed by lamination. . In the example of FIG. 2, L1, H2, L3, H4,.
9, a total of 49 layers are formed, and a coating layer (M layer) is formed thereon.
24 are formed. As the members of the substrates 321 and 322, a member having a refractive index higher than that of ordinary optical glass is used as described later.
8 or an optical glass such as BK7-S. The material of the L layer of the polarization separation film 20 is MgF ₂ , the material of the H layer is MgO, and the coating layer (M
As the material of the layer), SiO ₂ is used.

The polarization separation film 20 and the coating layer 2 shown in FIG.
In order to determine the film thickness of each layer of No. 4, for example, Film * Sta
r (Manufacturer: FTG Software Associates (POBox 57
9 Princeton, NJ, 08542)) It is assumed that commercially available software is used.

FIG. 3 shows the polarization separation element 330 shown in FIGS.
FIG. 4 is an explanatory diagram of the operation of the optical system of FIG. S for the polarization separation element 330
When light having a random polarization direction including a polarization component and a P-polarization component is incident in parallel (perpendicular to the incident surface of the polarization separation element 330), the polarization separation film 20 has the random polarization direction. Light enters at an incident angle of 45 °. Since the polarization splitting film 20 is designed to be optimal when the incident angle is 45 ° as described above, the characteristics at that time are the best. However, if the angle of incidence on the polarization separation element 330 is deviated (the component of light that is not orthogonal to the plane of incidence increases), the angle of incidence on the polarization separation film 20 will not be 45 °. The dashed line 1a in FIG. 3 is a case of ordinary optical glass (refractive index n = 1.52), and the solid line 1b is a case of high refractive index optical glass (refractive index n = 1.8).
As is clear from the figure, the deviation of the incident angle with respect to the polarization separating film 20 (deviation based on 45 °) is smaller in the high refractive index optical glass than in the ordinary optical glass, and the high refractive index optical glass is used. Thus, it can be seen that the variation in the incident angle is corrected. Therefore, even if the deviation of the incident angle with respect to the polarization separation element 330 is the same, the polarization separation film 20
It can be seen that the deviation of the incident angle with respect to the optical glass having a high refractive index is smaller than that of the ordinary optical glass, and the deterioration of the characteristics is relatively reduced.

The angle of incidence on the polarization splitting film 20 is determined by the following equation. Here, the refractive index of air is “1”.

Θ _i = 45 ± sin ⁻¹ ｛(1 / n _G ) · si
nθ _d ｝ (deg) θ _i : angle of incidence on the polarization splitting film 20 n _G : refractive index of glass θ _d : angle of incidence on the polarization splitting element 330

The incident angle θ _d to the polarization separation element 330 is 0 to
When the incident angle θ _i to the polarization splitting film 20 in the range of 7 ° is obtained by the above equation, it is as shown in Table 1.

[0028]

[Table 1]

The incident angle θ _d to the polarization beam splitter 330 shown in Table 1
Is 7 °, the refractive index n _G of the glass is 1.52.
Table 2 shows the total transmitted light amount for the cases of 1.8 and 1.8.

[0030]

[Table 2]

As is apparent from the characteristics shown in Table 2, when the refractive index n _{G of} glass is 1.52 and 1.8, the total transmitted light amount is 4%.
It can be seen that there is a difference of%. Therefore, when glass having a high refractive index is used, even when the light incident on the polarization beam splitter 330 deviates from the set incident angle, the deterioration of the characteristics is reduced.

FIGS. 4 and 5 are characteristic diagrams showing the influence of the refractive index of the substrate glass. FIG. 4 shows ordinary glass (glass refractive index n _G is 1.5), and the incident angle θi to the polarization separation film 20 is 45 ° (the incident angle θ _d to the polarization separation element 330 is 0).
It is the figure which showed the characteristic of the transmittance | permeability of P wave (1.5P-45) and the transmittance | permeability of S wave (1.5S-45) of (case of ゜). FIG. 5 shows ordinary glass (glass refractive index n _G is 1.5).
And glass having a high refractive index (glass refractive index 1.8), the incident angle θ _i to the polarization separation film 20 is 52 ° (the polarization separation element 33
P-wave transmittance of the incident angle theta _d to 0 if a 7 °) (1.5
P-52, 1.8P-52) and S wave transmittance (1.5
S-52, 1.8S-52).
4 and 5 and FIG. 6 described later,
1.5 and 1.8 represent the refractive index, and P and S represent the polarization directions,
Reference numeral 2 denotes an incident angle θ _i to the polarization separation film 20.

As is clear from the characteristics shown in FIGS. 4 and 5,
When the incident angle θ _i to the polarization separation film 20 deviates from 45 ° (the incident angle θ _d to the polarization separation element 330 is 0 °),
As the P-wave transmittance decreases and the S-wave transmittance increases, the characteristics decrease (1.5P-52, 1.5S-5).
2) By using a glass having a high refractive index, the degree of the decrease is relatively suppressed (1.8P-52, 1.8S-5).
2) It can be seen that the characteristics are improved.

FIG. 6 is a graph showing the characteristics of the transmittance of P-polarized light and S-polarized light with respect to the incident angle of ordinary glass and high refractive index glass. The wavelength used in this calculation is 60
0 nm. The characteristics (1.8P-52, 1.8S-52) when using a glass with a high refractive index are the characteristics (1.5P-52, 1.5S-5) when using ordinary glass.
The characteristics are improved compared to 2).

Embodiment 2 FIG. FIG. 7 is a schematic configuration diagram showing a main part of a projection display device 800 including the polarization conversion element shown in FIG. The projection display device 800 includes a polarization illumination device 50, dichroic mirrors 801 and 804, reflection mirrors 802, 807 and 809, and a relay lens 80.
6,808,810 and three liquid crystal light valves 80
3, 805, 811, a cross dichroic prism 813, and a projection lens 814.

FIG. 8 is a schematic structural view of a principal part of the polarized light illuminating device 50 of FIG. This polarized illumination device 50
Includes a light source unit 60 and a polarization generator 70.
The light source unit 60 emits a light beam having a random polarization direction including an S-polarized component and a P-polarized component. The light beam emitted from the light source unit 60 is one type of linearly polarized light (S-polarized light in the present embodiment) whose polarization direction is almost aligned by the polarization generator 70.
To illuminate the illumination area 80. The illumination area 80 corresponds to the three liquid crystal light valves 803, 805, and 811 in the projection display device of FIG.

The light source section 60 includes a light source lamp 101 and a parabolic reflector 102. Light source lamp 10
The light radiated from 1 is reflected in one direction by the parabolic reflector 102, becomes a substantially parallel light flux, and enters the polarization generator 70.

The polarization generator 70 is provided for the first optical element 20.
0 and a second optical element 400. FIG.
FIG. 3 is a perspective view of a first optical element 200. The first optical element 200 has a configuration in which minute light beam splitting lenses 201 having a rectangular outline are arranged in a matrix of M rows in the vertical direction and 2N columns in the horizontal direction. Therefore, from the center line CL in the lateral direction of the lens, N columns in the left direction and N columns in the right direction
Column exists. In this example, M = 10 and N = 4. The first optical element 200 is arranged such that the optical axis coincides with the center of the first optical element 200. The external shape of each light beam splitting lens 201 as viewed from the Z direction is set to be similar to the shape of the illumination area 80. In the present embodiment, since the illumination region 80 has a horizontally long shape that is long in the x direction, the outer shape of the light beam splitting lens 201 on the XY plane is also horizontally long.

The second optical element 400 (FIG. 7) includes an optical element 300 and an exit lens 390. The optical element 300 and the emission-side lens 390 are arranged such that the centers thereof coincide with the optical axis.

The optical element 300 includes the condenser lens array 31
0, a light shielding plate 315, and two polarization conversion elements 320a,
320b (see FIG. 1). The condensing lens array 310 is a lens array having the same configuration as the first optical element 200, and is arranged in a direction facing the first optical element 200. The condensing lens array 310 condenses the plurality of split light beams split by the respective light beam splitting lenses 201 together with the first optical element 200, and the polarization conversion elements 320a, 3
20b. The polarization conversion element 320a,
Reference numeral 320b denotes an arrangement in which two polarization conversion elements having the configuration shown in FIG. 1 are arranged such that the respective polarization separation films and reflection films face each other. The polarization conversion element 32
0a and 320b are the polarization separation elements 33 as described above.
The λ / 2 phase difference plate 381 is selectively disposed on the emission surfaces of the reference numerals 0a and 330b. The light-shielding plate 315 is formed by the condenser lens array 310 and the polarization conversion elements 320a and 320b.
This is arranged to prevent light that could not be collected on the polarization separation film from directly entering the reflection film. The polarization conversion elements 320a and 320b are provided with the polarization separation film 20 and the reflection film 30 described above. Therefore, the light source unit 60
Can be converted into one type of linearly polarized light (in this embodiment, S-polarized light) with high efficiency and emitted.

The exit lens 390 shown in FIG.
00, a plurality of split light beams (the polarization conversion element 32
0a and 320b) are superimposed on the illumination area 80, that is, on the liquid crystal light valves 803, 805 and 811.

The dichroic mirrors 801 and 80 shown in FIG.
Reference numeral 4 denotes a light beam emitted from the polarized light illuminating device 50 for red, blue,
It has a function as a color light separation unit that separates into three green color lights. Three liquid crystal light valves 803, 805, 81
Reference numeral 1 has a function as a modulating unit that forms an image by modulating three color lights in accordance with given image information (image signals). Cross dichroic prism 81
Reference numeral 3 has a function as color light combining means for forming a color image by combining three color lights. The projection lens 814 is
It has a function as projection optical means for projecting the light representing the synthesized color image on the screen 815.

A blue light green light reflecting dichroic mirror 801
Transmits the red light component of the light beam emitted from the polarized light illuminating device 50 and reflects the blue light component and the green light component. The transmitted red light is reflected by the reflection mirror 802 and reaches the red light liquid crystal light valve 803. Ten thousand,
Of the blue light and the green light reflected by the first dichroic mirror 801, the green light is reflected by the green light reflecting dichroic mirror 804, and the green light liquid crystal light valve 8.
Reach 05. The 10,000 blue light also passes through the second dichroic mirror 804.

In this embodiment, the optical path length of the blue light is 3
It is the longest of the two colored lights. Therefore, for blue light, after the dichroic mirror 804, a light guide unit 850 including an entrance lens 806, an intermediate lens 808, and an exit lens 810 is provided. That is, after transmitting the blue light through the green light reflecting dichroic mirror 804, first, the incident lens 806 and the reflecting mirror 807
, The light is guided to the intermediate lens 808. Further, the light is reflected by the reflection mirror 809 and guided to the emission lens 810, and reaches the liquid crystal light valve for blue light 811.

The three liquid crystal light valves 803, 805,
811 modulates each color light in accordance with an image signal (image information) provided from an external control circuit (not shown), and generates color light including image information of each color component. These liquid crystal light valves are usually provided with a polarizing plate (not shown) on each of the incident side and the exit side.
Therefore, predetermined polarized light (S-polarized light in this embodiment)
Only the light passes through the polarizer on the incident side of the liquid crystal light valve and is modulated.

The modulated three color lights enter the cross dichroic prism 813. In the cross dichroic prism 813, a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape. The three color lights are combined by these dielectric multilayer films to form light representing a color image. The synthesized light is projected on a screen 815 by a projection lens 814 as a projection optical system, and an image is displayed in an enlarged manner.

The polarized illumination device 50 of the projection display device 800
The polarization conversion element 320 according to the present invention as described above
Since a and 320b are used, even if the incident angle of the light from the light source unit 60 is slightly shifted, the light is converted into a desired linearly polarized light (in this embodiment, S-polarized light) with high efficiency and emitted. You. Therefore, such a polarization conversion element 320a,
In the projection type display device including 320b, the brightness of the image projected on the screen 815 can be increased.

Embodiment 3 FIG. In the above-described embodiment, an example of a glass substrate having a refractive index of 1.8 has been described, but the high refractive index in the present invention is in the range of 1.6 to 1.9, preferably 1.7 to 1.9. 1.9, or 1.8-1.
9 is in the range. Further, in the above-described embodiment, an example has been described in which the polarization separation film transmits the P-polarized wave and reflects the S-polarized wave, and the reflection film reflects the S-polarized wave. Alternatively, the P-polarized wave may be used by transmitting the S-polarized wave and reflecting the P-polarized wave, so that the reflection film reflects the P-polarized wave.

[0049]

As described above, according to the present invention, since a member having a high refractive index is used for the transmissive substrate of the polarization beam splitting element, the angle of incidence of light on the polarization beam splitting element (that is, the incidence angle on the polarization beam splitting film). Angle) deviates from the preset incident angle, the transmissive substrate functions to correct the direction of the incident light, and the incident angle with respect to the polarization splitting film is corrected and the incident angle is set. As the angle approaches the angle, a decrease in the separation characteristics of the polarization separation film is suppressed. Therefore, a decrease in the light utilization rate can be avoided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a polarization conversion element according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a part of a polarization splitting film of the polarization conversion element of FIG.

FIG. 3 is an explanatory diagram of an operation of the polarization beam splitter of FIG. 1;

FIG. 4 is a characteristic diagram of a conventional polarization splitting element.

FIG. 5 is a characteristic diagram of the polarization beam splitter of FIG. 1 and a conventional polarization beam splitter.

FIG. 6 is a characteristic diagram showing a relationship between a change in an incident angle and a transmittance in the polarization beam splitter of FIG.

FIG. 7 is a schematic configuration diagram showing a main part of a projection display device including the polarization conversion element shown in FIG.

8 is a schematic configuration diagram of a main part of the polarized light illuminating device of FIG.

FIG. 9 is a perspective view of the first optical element of FIG. 7;

FIG. 10 shows incident angles (41 ° to 49 °) with respect to the polarization splitting film.
It is a characteristic diagram of P wave transmittance in ゜).

FIG. 11 shows incident angles (41 ° to 49 °) with respect to the polarization splitting film.
It is a characteristic diagram of S wave reflectance in ゜).

[Explanation of symbols]

 Reference Signs List 20: polarized light separating film 22: multilayer structure part 24: coating layer (M layer) 30: reflective film 320: polarized light converting element 321, 322: glass substrate with high refractive index 330: polarized light separating element 381: λ / 2 retardation plate

Claims (10)

[Claims] 1. A polarization separation element for separating incident light into two types of polarized light, comprising: a plurality of translucent substrates;
A polarized light separating element, comprising: a polarized light separating film and a reflective film alternately arranged between the plurality of light transmitting substrates, wherein the light transmitting substrate is made of a high refractive index light transmitting substrate. 2. The polarization separation element according to claim 1, wherein the light-transmitting substrate is formed of a glass substrate having a high refractive index. 3. The polarization splitting device according to claim 1, wherein the transmissive substrate has a refractive index of 1.6 or more. 4. The polarization separation element according to claim 3, wherein the transmissive substrate has a refractive index of 1.8 or more. 5. The polarization separation film has a multilayer structure in which a plurality of first layers having a smaller refractive index and a plurality of second layers having a larger refractive index are alternately stacked as compared with the refractive index of the transparent substrate. The polarization separation element according to claim 1, wherein 6. The polarization separation element according to claim 1, wherein the polarization separation film and the reflection film are disposed at an angle of 45 ° with respect to an incident surface. 7. The polarizing beam splitter according to claim 1, wherein the polarized light separating film transmits a P-polarized wave and reflects an S-polarized wave in the incident light, and the reflecting film reflects the S-polarized wave. Polarization separation element. 8. The method according to claim 1, wherein the polarization separating film transmits an S-polarized wave and reflects a P-polarized wave in the incident light, and the reflecting film reflects the P-polarized wave. The polarized light separating element according to any one of the above. 9. A polarization conversion device for converting incident light into one type of polarized light, wherein the polarization separation device according to claim 1 and two types of polarization separation devices. And a selective phase difference plate for converting one of the polarized lights into the other polarized light. 10. A light source section, a polarization conversion element for converting light emitted from the light source section into substantially one type of polarized light, and modulating light from the polarization conversion element based on a given image signal. And a projection optical unit for projecting light modulated by the modulation unit, wherein the polarization conversion element comprises the polarization conversion element according to claim 9.