JP4877612B2 - Wave plate, polarization conversion element, and projection display device - Google Patents

Description

The present invention relates to a wavelength plate that functions as a half-wave plate in a wide wavelength range of 400 to 700 nm and has a small wavelength dependency, a polarization conversion element using the same, and a projection display such as a liquid crystal projector including the same. Relates to the device.

In recent years, liquid crystal projectors capable of directly projecting a screen displayed on a personal computer or the like to a screen are becoming widespread for the purpose of presentations, etc., and are also reduced in size, improved in resolution, and used in light efficiency. Improvements are being made.
Therefore, a polarization conversion element is built in the liquid crystal projector, and the light beam output from the light source using a halogen lamp or the like is converted into a polarized light beam so that the polarization of the light beam incident on the liquid crystal panel is aligned. It has become so.

  FIG. 8 shows a configuration example of a conventional polarization conversion element. The polarization conversion element 1 has a structure including a half-wave plate 4 at a predetermined position of a prism array 3 in which an optical thin film 2 is formed on the slope of a prism. 8 will be described. A light beam emitted from a light source such as a halogen lamp includes an S-polarized component and a P-polarized component, and is input to the prism array 3 as incident light of the polarization conversion element 1. Here, since the light beam necessary for the projection of the screen using the liquid crystal panel is only one polarization component, the polarization component 1 is used to polarize the unnecessary polarization component to align the polarization of the outgoing light. , Functioning to use light energy efficiently.

  Therefore, the P-polarized component of incident light input to the prism array 3 is transmitted through the optical thin film 2 and input to the half-wave plate 4, and the polarization plane rotates 90 degrees when passing through the half-wave plate. Then, it is emitted as S-polarized light as the first path. On the other hand, the S-polarized component contained in the incident light input to the prism array 3 is reflected by the optical thin film 2 and emits S-polarized light as the second path. Therefore, the outgoing light output from the polarization conversion element 1 is aligned with the S-polarized light, and efficient use of light energy is achieved.

The wavelength range of a light source used in a liquid crystal projector is usually about 400 to 700 nm. As performance required for a polarization conversion element, an optical thin film and a half-wave plate are each in a wide wavelength range of 400 to 700 nm. It is necessary to limit the loss in light efficiency.
Therefore, hereinafter, a broadband half-wave plate which is a component of the above-described polarization conversion element will be described.

  A wave plate is an element made of a crystal material such as quartz, or a resin film, and uses the speed difference between ordinary and extraordinary rays due to their birefringence, and creates a phase difference between the two rays. This changes the polarization state of light. As is well known, the half-wave plate has a function of converting linearly polarized light obtained by rotating the polarization plane of incident light by 90 degrees. Further, the conventional wave plate has been functioning as a half wave plate at a specific wavelength due to the problem of wavelength dependency.

  FIG. 9 is a diagram illustrating an example of the retardation wavelength dependency of a conventional half-wave plate. FIG. 9 is a graph in which the vertical axis indicates the phase difference and the horizontal axis indicates the wavelength, and the change in the phase difference accompanying the change in the wavelength is obtained. As shown in FIG. 9, the conventional half-wave plate shows a phase difference of 180 deg in the vicinity of a wavelength of 500 nm, and increases or decreases by a predetermined inclination in the front and rear wavelength bands.

  However, the performance of the half-wave plate incorporated in the polarization conversion element used in the liquid crystal projector needs to be 180 degrees out of phase with respect to a wide wavelength range of 400 to 700 nm. Has a wavelength dependency, so it has been difficult to use as a polarization conversion element of a liquid crystal projector.

  Here, as a means for widening the wavelength plate, disclosed in Japanese Patent No. 3174367, a laminated wave plate formed by laminating a plurality of stretched films giving a half-wave phase difference has been proposed. The invention according to No. 3174367 uses a stretched film as the material of the wave plate and has a problem in heat resistance or reliability.

Accordingly, the present invention has been made to solve the above-described problems, and uses a quartz substrate having excellent heat resistance or reliability as a material for the wavelength plate, and a wavelength range of 400 to 700 nm. The objective of the present invention is to provide a wave plate that functions as a half-wave plate, a polarization conversion element using the wave plate, and a projection display device such as a liquid crystal projector provided with the polarization conversion element .

In order to achieve the above object, the wave plate according to the present invention crosses the first wave plate having the phase difference Γ1 and the second wave plate having the phase difference Γ2 with respect to the light having the wavelength λ. A wavelength plate that is converted into linearly polarized light obtained by rotating the polarization plane of linearly polarized light that is incident in the range of wavelengths λ1 to λ2 (where λ1 <λ <λ2), and rotated by 90 degrees,
The material of the first wave plate and the material of the second wave plate are quartz,
The angle formed between the polarization plane of the incident linearly polarized light and the optical axis of the first wave plate is defined as the optical axis azimuth angle θ1, and the angle formed between the incident plane of the linearly polarized light and the optical axis of the second wave plate is optical. When the axis azimuth θ2 is set, the optical axis azimuth θ1 and the optical axis azimuth θ2 are
θ2 = θ1 + 45 (1)
0 <θ1 <45 (2)
Satisfied,
Wavelength λ
λ1 <λ <(λ2-λ1) / 2 + λ1 (3)
To the range of
Phase difference Γ1 and phase difference Γ2 are
Γ1 = 180 deg + a (5)
Γ2 = 180 deg + b (6)
b = 2 × a (7)
0 deg ≦ a ≦ 10 deg
As well as
The optical axis azimuth θ1 is θ1 ≠ 22.5 deg, the amount of phase difference deviation of the first wave plate when the wavelength λ changes is ΔΓ1, and the second wave plate of the second wave plate when the wavelength λ changes. When the amount of phase difference deviation is ΔΓ2,
ΔΓ1 = ΔΓ2 (4)
It is characterized by satisfying.

In one embodiment, a = 0, and the optical axis azimuth angle θ1 formed by the incident polarization plane of the linearly polarized light and the optical axis of the first wave plate is set to be θ1 = 25 deg.
In another embodiment, a ≠ 0. In this case, θ1 = 19 deg can be further set.

Further, according to the present invention, it provided the first major surface and the flat plate-like transparent base to the light incident morphism surface Toshikatsu second main surface a light-emitting surface, while the substrate first 1 and a second optical thin film, and a wave plate provided on the second main surface of the substrate,
The first and second optical thin films are inclined with respect to the first and second main surfaces and arranged alternately and parallel to each other;
The first optical thin film separates light incident from the first main surface side into first linearly polarized light and second linearly polarized light that are orthogonal to each other, transmits the first linearly polarized light, and second Reflects linearly polarized light,
The second optical thin film reflects and emits the second linearly polarized light reflected by the first optical thin film from the second main surface;
The wave plate is the wave plate of the present invention described above, and there is provided a polarization conversion element disposed on a portion of the second main surface that emits the first linearly polarized light transmitted through the first optical thin film.

In one embodiment, the wave plate is a laminate of a first wave plate and a second wave plate.

In another embodiment, in the polarization conversion element of the present invention, the first linearly polarized light is P-polarized light and the second linearly polarized light is S-polarized light.

According to another aspect of the present invention, the light source, the polarization conversion element of the present invention that converts the light from the light source into the second linearly polarized light and emits the light, and the light emitted from the polarization conversion element, There is provided a projection display device including a modulation unit that modulates according to image information to be projected, and a projection optical system that projects light modulated by the modulation unit.

In one embodiment, the modulation means of the projection display device is a liquid crystal panel.

As described above, the wave plate of the present invention has a function as a half-wave plate over a wavelength range from 400 nm to 700 nm by laminating a predetermined first wave plate and a second wave plate. To do.
By using this wave plate, the polarization conversion element of the present invention can exhibit a remarkable effect when used in a liquid crystal projector or the like.

Furthermore, in the polarization conversion element of the present invention , the wavelength plate is composed of a first wavelength plate and a second wavelength plate made of a quartz substrate, and provides a polarization conversion element with excellent heat resistance or reliability. It becomes possible to exert a remarkable effect.

It is a figure which shows the structure of one Embodiment of the 1/2 wavelength plate used for the polarization conversion element which concerns on this invention. The Poincare sphere of a half-wave plate used in the present invention is shown. It is a block diagram which shows one Example of the polarization conversion element which concerns on this invention. 6 is a graph showing the correlation between the phase difference and Ts of the outgoing light S component in the half-wave plate used in the present invention. It is a graph which shows a 1st simulation result in the half-wave plate used for this invention. It is a graph which shows a 2nd simulation result in the half-wave plate used for this invention. It is a graph which shows the wavelength dependence in one Example of the half-wave plate used for this invention. It is a figure which shows the structure of the conventional polarization conversion element. It is a graph which shows the phase difference wavelength dependence of the conventional 1/2 wavelength plate.

Hereinafter, the present invention will be described in detail based on illustrated embodiments.
FIG. 1 is a diagram showing the configuration of an embodiment of a half-wave plate used in the polarization conversion element of the present invention, FIG. 1 (a) is a perspective overview, and FIG. 1 (b) It is a disassembled perspective view. The half-wave plate 5 has a phase difference Γ1 of 190 deg with respect to a wavelength of 420 nm and an optical axis azimuth angle θ1 of 19 deg, and a phase difference Γ2 with respect to a wavelength of 420 nm of 200 deg. axis azimuth θ2 is a second quartz crystal wave plate 7 of 64Deg, each crystal optical axis 8 and 9 arranged to intersect at an angle of 45 deg, 1/2 wavelength plate in a broadband wavelength 400~700nm overall Are stacked to function as That is, when the linearly polarized light 10 that is the P-polarized component is incident on the half-wave plate 5, the phase is shifted by 180 deg at the exit surface, so that it is output as the linearly polarized light 11 that is the S-polarized component obtained by rotating the polarization plane of the incident light by 90 deg. It has a function to do.

Next, a method for calculating optical characteristics of the first quartz wavelength plate 6 and the second quartz wavelength plate 7 constituting the half-wave plate 5 used in this embodiment will be described.
In the numerical calculation, the following Mueller matrix is used to indicate each polarization state.

  The Mueller matrix A1 of the first quartz wave plate 6 can be expressed by the following equation (1).

  The Mueller matrix A2 of the second quartz wave plate 7 can be expressed by the following equation (2).

  The incident polarization state incident on the half-wave plate 5 is a Stokes vector T and is expressed by the following equation (3).

  The outgoing polarization state emitted from the half-wave plate 5 is a Stokes vector S and is expressed by the following equation (4).

  As described above, the Mueller determinant of the following equation (5) is obtained from the equations (1) to (4).

  In Equation (5), when T is an incident polarization state as in Equation (6) below,

Equation (5) is

と表すことが出来、この式をもとにシミュレーション解析を行う。 The phase difference Γ of the half-wave plate is

The simulation analysis is performed based on this formula.

  Therefore, θ1, Γ1, θ2, and Γ2 estimated by the above equation (8) are inputted to perform calculation and an optimum value is obtained. However, since the combinations are enormous, consideration on the Poincare sphere is added to some extent. Ask for a guide.

FIG. 2 shows a Poincare sphere of a half-wave plate used in the present invention. Therefore, a method for canceling the wavelength dependence of the half-wave plate using the present Poincare sphere will be described. First, the setting conditions
Incident polarization plane: horizontal direction in FIG.
First quartz wave plate: phase difference Γ1 = 180 deg
Optical axis azimuth: θ1
Second quartz wave plate: phase difference Γ2 = 180 deg
Optical axis azimuth: θ2
Then, the polarization state of the light transmitted through the first quartz wave plate and the second quartz wave plate can be considered as follows.

  The function of this half-wave plate is to rotate the polarization plane by 90 deg in the band of 400 to 700 nm, and this can be expressed by Poincare sphere with coordinates P0 (S1, S2, S3) = (1, 0, 0) is moved to P2 (-1, 0, 0). Therefore, the starting point is the intersection point P0 between the S1 axis and the spherical surface. Next, after setting the rotation axis R1 to the position where the S1 axis is rotated counterclockwise by 2θ1, the phase difference is rotated 180 deg clockwise with the R1 axis as the rotation axis, and the point reached is defined as P1. Next, after setting the rotation axis R2 at a position where the S1 axis is rotated counterclockwise by 2θ2, the phase difference is rotated clockwise by 180 deg using the R2 axis as a rotation axis, and the point reached is defined as P2.

According to this operation method, in order for P2 to reach (−1, 0, 0), the optical axis directions θ1 and θ2 only need to satisfy the following conditions.
θ2 = θ1 + 45 (9)
0 <θ1 <45 (10)

Further, the change in wavelength means that the phase difference between the first wave plate and the second wave plate is shifted from 180 deg. When the shift amounts at this time are ΔΓ1 and ΔΓ2, respectively, the operation method described above is used. From
ΔΓ1 = ΔΓ2 (11)
If so, the phase difference can be canceled out, and P2 always reaches the equator. For this reason, the first wave plate and the second wave plate need to have the same wavelength dependency.

  Further, if the phase difference is shifted, the S1 coordinate is affected, whereby P2 → P2 ', and a shift on the equator occurs, resulting in a rotational shift of the outgoing light polarization plane. Since this shift can reduce the influence as ΔΓ1 and ΔΓ2 are smaller, it is desirable to use the first wave plate and the second wave plate having the smallest wavelength dependency. Therefore, the first wave plate and the second wave plate can obtain the best characteristics by using a wave plate that functions in a single mode.

From the above results, the factor and the relational expression of the half-wave plate when performing the simulation analysis may be as follows.
Factor first wave plate optical axis azimuth: θ1
First wave plate phase difference: Γ1 (180 deg)
Second wave plate optical axis azimuth: θ2
Second wave plate phase difference: Γ2 (180 deg)
Polarization angle of outgoing light: φ (90 deg)

Relational expression θ2 = θ1 + φ / 2
0 <θ1 <45
ΔΓ1 = ΔΓ2

  Next, a method for evaluating the performance of a wave plate when used in a polarization conversion element will be described. In this case, the S-polarized light transmittance Ts is usually used as a rule for the wave plate. Therefore, Ts will be described below.

FIG. 3 is a block diagram showing an embodiment of a polarization conversion element using a half-wave plate according to the present invention. Similarly to the conventional polarization conversion element described above with reference to FIG. 8, the polarization conversion element 12 includes a half-wave plate 5 at a predetermined position of the prism array 3 in which the optical thin film 2 is formed on the slope of the prism. Structure. The polarization conversion element 12 is used in a projection display device such as a liquid crystal projector.

As is conventionally known, the prism array 3 is composed of a plate-shaped translucent base material having a first main surface as a light incident slope and a second main surface as a light output surface. In this translucent substrate, the first and second optical thin films 2 and 2 are formed on the inclined surface of the prism so as to be inclined with respect to the first and second main surfaces, They are arranged alternately and parallel to each other at intervals.

A light beam emitted from a light source such as a halogen lamp includes an S-polarized component and a P-polarized component that are orthogonal to each other, and is input to the prism array 3 as incident light of the polarization conversion element 1. The first optical thin film 2 separates light incident on the prism array 3 from the first main surface side into an S-polarized component and a P-polarized component, transmits the P-polarized component, and reflects the S-polarized component. . The half-wave plate 5 is disposed on the second main surface of the prism array 3 at a portion that emits a P-polarized component transmitted through the first optical thin film 2.

The P-polarized component of the incident light input to the prism array 3 is transmitted through the first optical thin film 2 and input to the half-wave plate 5. As shown in FIG. The S-polarized component of the incident light input to the prism array 3 is reflected by the first and second optical thin films 2 and 2 and is emitted from the second path as S-polarized light. Therefore, the light output from the polarization conversion element 12 is aligned with the S-polarized light. As described above, the light emitted from the polarization conversion element 12 is aligned with the S-polarized light, so that the light energy can be used efficiently.

In a liquid crystal projector using a liquid crystal panel, a light beam necessary for projecting a screen is only one polarization component, that is, an S polarization component or a P polarization component. Therefore, when the polarization conversion element 12 of the present invention is used in a projection display device such as a liquid crystal projector, the energy of light can be used efficiently by polarizing unnecessary polarization components and aligning the polarization of outgoing light. Can function.

  Therefore, in FIG. 3, the phase difference of the half-wave plate becomes a problem for the path 1, and the path 1 is the phase difference between Tp which is the P-polarized light transmittance of the optical thin film and the half-wave plate. In general, the average transmittance required for the path 1 is 93%. On the other hand, as the Tp of the optical thin film, an average of 98% is obtained. From the above, the simulation formula for the required Ts emission characteristics of the half-wave plate is as follows.

  The emission characteristic of Ts is obtained by converting the phase difference value (Equation 8) obtained by the aforementioned Mueller matrix calculation into Jones matrix calculation. Therefore, when the phase difference of the half-wave plate is δ and the optical axis azimuth is θ, a Jones vector determinant as shown in the following equation (12) is obtained.

Next, when the obtained matrix solution is squared to obtain the intensity, the following equation is obtained.
Ts = 4 sin 2θ cos 2 sin 2δ / 2 (13)

Therefore, if the Tp of the optical thin film is 98%, the S-polarized component Ts of the emitted light is as follows:
Ts = (4 sin 2θ cos 2 sin 2δ / 2) × 0.98 (14)
The simulation of the emission characteristic of Ts is performed using Expression (14).

  Next, in equation (14), when the correlation between the phase difference and Ts of the emitted light S component is determined by setting the optical axis azimuth angle to θ = 45 deg and changing the phase difference δ, Ts is shown in FIG. It is as follows.

FIG. 4 is a graph showing the correlation between the phase difference and Ts of the outgoing light S component in the half-wave plate used in the present invention. From this result, in order to satisfy Ts ≧ 0.93, it is understood that the phase difference δ only needs to be in the range of 156 ≦ δ ≦ 204.

Next, the results of simulation analysis of the phase difference of the half-wave plate and the S-polarized light transmittance using the above-described equations (8) and (14) are shown.
First, from the results discussed on the Poincare sphere described above as the first step, the optimum factor of the half-wave plate is estimated, and simulation analysis is performed using it. As a result, the optimum simulation result based on the following factors is obtained. Which is shown in FIG.
θ1 = 25, θ2 = 70, Γ1 = 180 (λ = 490 nm), Γ2 = 180 (λ = 490 nm)

FIG. 5 is a graph showing a first simulation result in the half-wave plate used in the present invention. FIG. 5A shows the retardation wavelength dependency, and FIG. 5B shows the S polarization transmittance wavelength dependency. Since the wavelength dependence varies greatly on the short wavelength side near 500 nm, the simulation was performed with emphasis on the short wavelength side. As shown in FIG. 5, the bandwidth was significantly increased compared to the conventional half-wave plate.

  Next, a halogen lamp, which is a light source used in a liquid crystal projector, has a wavelength range of 400 to 700 nm and a light spread of ± 5 deg. There is a need to prevent the phase difference from changing even if the incident angle of light changes. Therefore, in the first simulation described above, a simulation is performed when the incident light changes by ± 5 degrees, and the result is shown in FIG.

FIG. 6 is a graph showing a second simulation result in the half-wave plate used in the present invention, FIG. 6 (a) shows phase difference wavelength dependence, and FIG. 6 (b) shows S-polarized light. The transmittance wavelength dependency is shown. 6A, the curve 13 indicates the incident angle of 0 deg, the curve 14 indicates the incident angle of +5 deg, and the curve 15 indicates the incident angle of −5 deg. In FIG. 6B, the curve 16 indicates the incident angle of 0 deg and the curve. 17 shows an incident angle of +5 deg, and a curve 18 shows an incident angle of -5 deg. As shown in FIG. 6, the wavelength dependency is degraded in the wavelength range of 500 nm to 550 nm, but the wavelength range of the halogen lamp as the light source is 400 nm to 700 nm, but particularly light near the wavelength of 550 nm is 80%. Therefore, it is necessary to reduce the deterioration of the wavelength dependence at this wavelength.

  In order to reduce the angle dependency of incident light, it is necessary to reduce the angle dependency of the first quartz wavelength plate and the second quartz wavelength plate. In quartz, Y-cut has the smallest angle dependency, but the thickness of the quartz substrate needs to be several tens of microns, which is not practical from the viewpoint of processing the quartz substrate. Therefore, if the thickness of the quartz substrate is set to 0.1 t on the assumption that the quartz wavelength plate is mass-produced, the cut-out angle β from the raw quartz substrate may be 27 degZ.

On the other hand, the reason why the angle dependency of incident light deteriorates is that the condition of ΔΓ1 = ΔΓ2 cannot be satisfied when the angle changes. This is because the optical axis azimuth angles of the two quartz wavelength plates are different, so that the amount of change in phase difference when the angle is changed is different. Therefore, the optimum value of the factor of the half-wave plate was obtained by simulation analysis so that the amount of phase change did not differ, and the optimum factor of the half-wave plate as shown below was obtained.
θ1 = 19, θ2 = 64, Γ1 = 190 (λ = 420 nm), Γ2 = 200 (λ = 420 nm)

Accordingly, FIG. 7 shows the retardation wavelength dependency and S-polarized light transmittance wavelength dependency of a half-wave plate using this factor.
FIG. 7 is a graph showing the wavelength dependence in one embodiment of the half-wave plate used in the present invention, FIG. 7 (a) shows the phase difference wavelength dependence, and FIG. S-polarized light transmittance wavelength dependence is shown. Further, in FIG. 7A, a curve 19 shows an incident angle of 0 deg, a curve 20 shows an incident angle of +5 deg, and a curve 21 shows an incident angle of -5 deg. In FIG. 7B, a curve 22 shows an incident angle of 0 deg and a curve. Reference numeral 23 denotes an incident angle of +5 deg, and curve 24 denotes an incident angle of -5 deg. By applying the factor as shown in this example to the half-wave plate, a half-wave plate excellent in wavelength dependency in the vicinity of the wavelength of 550 nm could be configured. Therefore, by repeating the simulation analysis using a predetermined calculation formula as described above, it is possible to obtain a half-wave plate configuration having desired performance in the wavelength region of 400 to 700 nm.

DESCRIPTION OF SYMBOLS 1 ... Polarization conversion element, 2 ... Optical thin film, 3 ... Prism array, 4 ... 1/2 wavelength plate, 5 ... 1/2 wavelength plate, 6 ... 1st quartz wavelength plate, 7 ... 2nd quartz wavelength plate, DESCRIPTION OF SYMBOLS 8 ... Crystal optic axis, 9 ... Crystal optic axis, 10 ... Linearly polarized light, 11 ... Linearly polarized light, 12 ... Polarization conversion element, 13 ... Wavelength dependence curve in + 0deg incident angle, 14 ... Wavelength dependence in + 5deg incident angle 15 ... wavelength dependence curve at -5 deg incidence angle, 16 ... wavelength dependence curve at ± 0 deg incidence angle, 17 ... wavelength dependence curve at +5 deg incidence angle, 18 ... wavelength at -5 deg incidence angle Dependency curve, 19 ... wavelength dependence curve at ± 0 deg incidence angle, 20 ... wavelength dependence curve at +5 deg incidence angle, wavelength dependence curve at 21-5 deg incidence angle, 22 ... wavelength at ± 0 deg incidence angle Dependence curve, wavelength dependence at 23 ... + 5deg incident angle Curve, the wavelength dependence curve at 24-5deg incident angle.

Claims (9)

A first wave plate having a phase difference Γ1 and a second wave plate having a phase difference Γ2 are arranged so that optical axes intersect each other with respect to light having a wavelength λ, and wavelengths λ1 to λ2 (where, a wavelength plate that converts linear polarized light that is incident in the range of λ1 <λ <λ2) into a linearly polarized light obtained by rotating the polarization plane by 90 deg;
The material of the first wave plate and the material of the second wave plate are quartz,
An angle formed between the polarization plane of the incident linearly polarized light and the optical axis of the first wave plate is an optical axis azimuth angle θ1, and the angle of polarization of the incident linearly polarized light and the optical axis of the second wave plate is When the angle formed is the optical axis azimuth angle θ2, the optical axis azimuth angle θ1 and the optical axis azimuth angle θ2 are
θ2 = θ1 + 45 (1)
0 <θ1 <45 (2)
Satisfied,
The wavelength λ
λ1 <λ <(λ2-λ1) / 2 + λ1 (3)
To the range of
The phase difference Γ1 and the phase difference Γ2 are
Γ1 = 180 deg + a (5)
Γ2 = 180 deg + b (6)
b = 2 × a (7)
0 deg ≦ a ≦ 10 deg
As well as
The optical axis azimuth θ1 is θ1 ≠ 22.5 deg, the amount of phase difference deviation of the first wave plate when the wavelength λ changes is ΔΓ1, and the first when the wavelength λ changes When the amount of phase difference between the two wave plates is ΔΓ2,
ΔΓ1 = ΔΓ2 (4)
A wave plate characterized by satisfying 2. The wave plate according to claim 1, wherein a = 0 and θ1 = 25 deg. The wave plate according to claim 1, wherein a ≠ 0. 4. The wave plate according to claim 3, wherein [theta] 1 = 19 deg. A flat translucent substrate to the first major surface light emitting surface light entrance morphism surface Toshikatsu second main surface, and first and second optical thin film provided in said base material A wave plate provided on the second main surface of the base material,
The first and second optical thin films are inclined with respect to the first and second main surfaces and alternately and parallel to each other;
The first optical thin film separates light incident from the first main surface side into first linearly polarized light and second linearly polarized light orthogonal to each other, and transmits the first linearly polarized light; Reflects the second linearly polarized light,
The second optical thin film reflects and emits the second linearly polarized light reflected by the first optical thin film from the second main surface;
The wave plate is a polarization conversion element disposed on a portion of the second main surface that emits the first linearly polarized light that has passed through the first optical thin film;
The polarization plate according to claim 1 , wherein the wave plate is the wave plate according to claim 1 . The polarization conversion element according to claim 5, wherein the wave plate is a laminate of the first wave plate and the second wave plate. The polarization conversion element according to claim 5 or 6 , wherein the first linearly polarized light is P-polarized light, and the second linearly polarized light is S-polarized light. A light source;
The polarization conversion element according to any one of claims 5 to 7 , wherein the light from the light source is converted into the second linearly polarized light and emitted.
Modulation means for modulating light emitted from the polarization conversion element according to image information to be projected;
And a projection optical system for projecting the light modulated by the modulating means. 9. The projection display device according to claim 8 , wherein the modulation means is a liquid crystal panel.

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