JP2013025065A - Wave plate, polarization conversion element, polarization conversion unit and projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wave plate that corrects influences of rotatory power and reliably functions as a half-wave plate with respect to a wavelength band in a wide range.SOLUTION: The wave plate comprises a material having birefringence and optical rotation, in which a first wave plate showing a phase difference of 180°, a second wave plate showing a phase difference of 180°, and a third wave plate showing a phase difference of 180° with respect to light at a predetermined design wavelength λ are arranged with the respective optical axes intersecting one another. The wave plate is configured in such a manner that: in each wave plate, an angle β formed by the normal line on the major face and the optical axis satisfies A(deg)≤β<90(deg); an orientation angle θ1 of the optical axis of the first wave plate, an orientation angle θ2 of the optical axis of the second wave plate and an orientation angle θ3 of the optical axis of the third wave plate satisfy θ1=15.0°+a, θ2=45.0 and θ3=75°-b, respectively; and A and a satisfy A=-7E-06a+0.0006a+0.0132a+0.1204a+0.4284a+13.155 and -15.0≤a≤8.0.

Description

The present invention relates to a wavelength plate that emits by rotating a polarization plane of linearly polarized light of incident light, a polarization conversion element including the same, a polarization conversion unit, and a projection apparatus.

A projection type video device (projection device) such as a liquid crystal projector is a device that modulates light emitted from a light source device according to image information and enlarges and projects the modulated optical image on a screen.
In this projection device, random polarized light emitted from the light source device (P-polarized light and S-polarized light whose polarization planes are orthogonal to each other, and linearly polarized light having various polarization plane directions are mixed to improve the light utilization efficiency. Light (polarized light such as light, circularly polarized light, elliptically polarized light, etc.) (hereinafter referred to as random light) is divided into a plurality of intermediate light beams, and the divided intermediate light beams are converted into one type of linearly polarized light to be unified. Thus, a polarization conversion element is used to emit light.
Such a polarization conversion element generally has PBS functions on both main surfaces (an optical functional film having a function of transmitting either linearly polarized light of P-polarized light and S-polarized light orthogonal to each other and reflecting the other linearly polarized light). A so-called polarization separation film) and a transparent mirror made of a transparent mirror such as a transparent mirror film are formed on the incident surface (lamination surface). Polarizing beam splitter (PBS) array (prism array) obtained by cutting at a predetermined angle, for example, 45 (deg) (or 135 (deg))
Is provided with a structure in which an organic material, for example, a half-wave plate made of a polycarbonate film is bonded to the emission side surface with an organic adhesive, and the random light emitted from the light source is arranged on the optical path. The light is selectively incident on the PBS film by the light shielding plate and separated into an S-polarized light beam and a P-polarized light beam. For example, the P-polarized light beam is transmitted through the PBS film, and the S-polarized light beam is reflected on the PBS film.

When the P-polarized light beam transmitted through the PBS film enters the half-wave plate, the phase is 180 (d
eg) By shifting, the light is converted to S-polarized light and emitted from the half-wave plate.
The S-polarized light beam reflected from the BS film is further reflected by the reflection mirror film, and 1 of the PBS array.
/ 2 It radiates | emits from the output surface of the area | region where the wavelength plate is not arrange | positioned.
As a result, light emitted from the polarization conversion element is unified into S-polarized light.
As such a half-wave plate (retardation plate) used in the polarization conversion element, a wideband so as to be applicable to a liquid crystal projector using three wavelength bands of R, G, and B which are the three primary colors of light. The phase difference is 180 (deg) at the wavelength, the polarization conversion efficiency is 1, and the P-polarized light is reliably converted to S-polarized light, or the broadband or wavelength-selective type 1 has a specification capable of converting S-polarized light to P-polarized light. / 2 wavelength plates are required.
Patent Document 1 discloses a plurality of half-wave plates that function as half-wave plates when light in each of the R, G, and B bands is transmitted. Each optical axis is at a predetermined angle with respect to each other. A laminated half-wave plate that functions as a half-wave plate in a wide band by laminating so as to cross each other has been proposed, but this also reduces the polarization conversion efficiency below 0.85 at all wavelengths. In other words, it is difficult to say that it functions completely as a half-wave plate in each wavelength band of R, G, and B. The same applies to the cited document 2.
Patent Document 3 describes the processing of each wave plate so that the processing errors of the thicknesses of the first and second wave plates to be laminated are corrected in a laminated broadband half-wave plate using quartz as a material. It is described that a predetermined polarization conversion efficiency can be satisfied by laminating first and second wavelength plates such that phase shift amounts ΔΓa and ΔΓb caused by an error satisfy a predetermined relational expression.
On the other hand, Patent Document 4 discloses that when light in each of the R, G, and B bands is transmitted, 1/2.
A half-wave plate made of a plurality of quartz crystals functioning as a wave plate is laminated so that the optical axes intersect each other at a predetermined angle, and the optical axis azimuth and multi-order mode of the wave plate are adjusted. This realizes high polarization conversion efficiency selectively in all wavelength bands (R, G, B bands).
A waveplate is described.

JP-A-5-100114 JP 59-60408 A JP 2008-268901 A JP 2007-304572 A JP 2005-158121 A

However, as listed as a problem in Patent Document 5 proposed for a quarter-wave plate using quartz, an optical crystal material (mainly made of a single crystal) having birefringence such as quartz is used. In particular, since it has optical rotation power, the cutting angle of each wave plate (intersection angle between the normal direction in the main surface of the crystal plate and the optical axis (Z axis)) is not 90 deg (also referred to as 90 deg Z), etc. Due to the influence of the optical rotation power, the polarization conversion efficiency is lowered, and there is a problem that it does not function as a half-wave plate that satisfies a desired polarization conversion efficiency in a certain wavelength range.
Therefore, the present invention corrects the influence of the optical rotation power in the quartz crystal having optical rotation and birefringence as described above, has a low incident angle dependency, and has a high polarization conversion efficiency (for example, 0) in a wide wavelength band. .8 or more) is intended to obtain a half-wave plate that can be realized.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1] This application example is made of a material having birefringence and optical rotation, and with respect to light having a wavelength λ, a first wave plate having a phase difference Γ1 and a second wave plate having a phase difference Γ2. And a third wave plate having a phase difference Γ3 so that their optical axes intersect with each other, and polarization of linearly polarized light of incident light with respect to light in a wavelength range of λ1 to λ2 (λ1 <λ2) A wave plate that emits light by rotating the surface by 90 (deg), and the wavelength λ satisfies λ1 ≦ λ ≦ λ2.
The phase difference Γ1, the phase difference Γ2, and the phase difference Γ3 are:
Γ1 = 2π / λ × (ne-no) × t1
Γ2 = 2π / λ × (ne-no) × t2
Γ3 = 2π / λ × (ne-no) × t3
Γ1 = Γ2 = Γ3 = 180 (deg)
Where ne is the extraordinary refractive index, no is the ordinary refractive index, t1 is the thickness of the first wave plate in the normal direction of the main surface, t2 is the thickness of the second wave plate in the direction of the main surface normal, and t3 Satisfies the relationship of the thickness of the third wave plate in the normal direction of the principal surface,
In each wave plate, the angle β formed by the principal surface normal and the optical axis is A when the lower limit of the angle β is A,
A ≦ β <90 (deg) is satisfied,
The optical axis azimuth angle θ1 of the first wave plate, the optical axis azimuth angle θ2 of the second wave plate, and the optical axis azimuth angle θ3 of the third wave plate are a correction value of the optical axis azimuth angle θ1, and When the correction value of the optical axis azimuth angle θ3 is b,
θ1 = 22.5 (deg) + a
θ2 = 45.0 (deg)
θ3 = 67.5 (deg) −b
However, a = b ≠ 0 (deg)
Satisfied,
The lower limit A of the angle β is
13 (deg) ≦ A
It is characterized by satisfying.

According to this application example, it is possible to realize a high polarization conversion efficiency (e.g., 0.8 or more) in a wide wavelength band by correcting the influence of the optical rotatory power in a quartz plate having optical rotation and birefringence.
It can be a wave plate.

[Application Example 2] In this application example, in the wave plate of Application Example 1, the lower limit value A of the angle β is:
A = -7E-06a ⁵ + 0.0006a ⁴ + 0.0132a ³ + 0.1204a ² +0
. 4284a + 13.155
Satisfied,
The correction value a of the optical axis azimuth angle θ1 is −15.0 (deg) ≦ a ≦ 8.0 (deg).
It is characterized by satisfying.

According to this application example, the average loss of the polarization conversion efficiency is 20% or less in the wavelength range of 400 nm to 700 nm, and the high polarization conversion in which the average loss of the changed conversion efficiency is 10% or less in the wavelength range of 500 nm to 600 nm. 1 / can achieve efficiency
A two-wave plate can be used.

Application Example 3 This application example is the wavelength plate according to Application Example 1 or 2, wherein the wavelength λ1 is:
400 nm, the wavelength λ2 is 700 nm, and the wavelength λ is λ = (λ1 + λ
2) / 2 = 550 nm is satisfied.

According to this application example, the polarization conversion efficiency can be maximized in the G band where the best characteristics are required in the projector by setting the design wavelength to the center of the G band.

[Application Example 4] In this application example, in the wave plate according to Application Example 1 or 2, the wavelength λ3 is 5
When the wavelength λ4 is 600 nm and the wavelength λ4 is 600 nm, the relationship between the wavelength λ and the wavelengths λ3 and λ4 satisfies λ3 ≦ λ ≦ λ4.

According to this application example, the polarization conversion efficiency can be maximized in the G band where the best characteristics are required in the projector by setting the design wavelength to the center of the G band.

Application Example 5 This application example has a light incident surface and a light output surface that are substantially parallel to each other, and an adhesive is interposed between the light incident surface and a bonding surface having a predetermined inclination angle with respect to the light output surface. Two kinds of straight lines that are alternately provided at boundaries between the plurality of translucent substrates joined together and the plurality of translucent substrates, and whose polarization directions are orthogonal to each other. An optical device having a polarization separating unit that separates polarized light and transmits one linearly polarized light and reflects the other linearly polarized light, and a reflecting unit that reflects the other linearly polarized light beam reflected and changes the direction of the optical path. An element and the light exit surface, and disposed in an upper region of the polarization separation unit or an upper region of the reflection unit;
A wavelength plate that rotates the polarization plane of one of the two types of linearly polarized light, converts it into a linearly polarized light parallel to the polarization plane of the other linearly polarized light, and emits the waveplate, The wave plate according to any one of Application Examples 1 to 4, wherein the adhesive layer is an ultraviolet curable adhesive,
The thickness is 5 μm or more and 10 μm or less.

According to this application example, by using an ultraviolet curable resin adhesive excellent in heat resistance and light resistance performance as an adhesive when creating an optical element, it has high heat resistance and light resistance, and further, the optical axis azimuth is By setting as described above and correcting for the effect of optical rotation, the structure of a polarization conversion element equipped with a retardation plate that reliably functions as a half-wave plate for broadband light is realized. I can do it.
Further, since the thickness of the adhesive layer is 10 μm or less and is sufficiently thin, the corner portion of the translucent substrate is not scraped when the light incident surface or the like is polished. Therefore, there is no problem that the light transmission region becomes narrow.

Application Example 6 This application example is the polarization conversion element according to Application Example 5, wherein the adhesive layer contains a modified acrylate or a modified methacrylate as a main component.

According to this application example, by using an ultraviolet curable resin adhesive excellent in heat resistance and light resistance performance for adhesion of the transparent substrate, the polarization conversion element can have high heat resistance and high light resistance and can have a long life.

Application Example 7 This application example is characterized by a polarization conversion unit including the polarization conversion element according to Application Example 5 or 6, and a fixed frame for fixing the polarization conversion element.

According to this application example, by providing the polarization conversion element of the present invention, a polarization conversion unit having a long lifetime and excellent optical characteristics can be obtained.

Application Example 8 This application example includes a light source device that emits light, the polarization conversion unit according to Application Example 7 that converts light from the light source device into one type of polarized light, and the polarization conversion unit. A projection apparatus comprising: a light modulation device that forms an optical image of the polarized light according to image information; and a projection optical device that enlarges and projects the optical image formed by the light modulation device.

According to this application example, by providing the polarization conversion element of the present invention, a polarization conversion unit having a long lifetime and excellent optical characteristics can be obtained.

The figure which shows the structure of the lamination | stacking 1/2 wavelength plate as an example of the phase difference plate which concerns on embodiment of this invention. The figure explaining the polarization state in the laminated half-wave plate 1 shown in FIG. The figure which shows the polarization state at the time of considering the optical rotatory power of a waveplate. The graph which shows the lower limit of a cutting angle, the correction value of an optical axis azimuth, and the simulation result of thickness. The figure which shows the conversion efficiency of the lamination | stacking 1/2 wavelength plate with respect to wavelength 400nm to 700nm. The figure which shows the conversion efficiency of the lamination | stacking 1/2 wavelength plate with respect to wavelength 400nm to 700nm. The figure which shows the conversion efficiency of the lamination | stacking 1/2 wavelength plate with respect to wavelength 400nm to 700nm. The figure which shows an example of the polarization conversion element to which the laminated wave plate of this invention is applied. The figure explaining the problem of the conventional polarization conversion element in detail. The figure explaining the problem of the conventional polarization conversion element in detail. Schematic explaining the composition of a plasma polymerization film. The disassembled perspective view which shows the polarization conversion element which concerns on other embodiment. Sectional drawing which expanded and showed a part of polarization conversion element of FIG. The figure explaining the manufacturing process of a polarization conversion element. The figure explaining the manufacturing process of a polarization conversion element. The figure explaining the manufacturing process of a polarization conversion element. The figure explaining the manufacturing process of a polarization conversion element. The figure explaining the manufacturing process of a polarization conversion element. The figure explaining the manufacturing process of a polarization conversion element. The figure explaining the manufacturing process of a polarization conversion element. The figure which shows the heat resistance test of Example 1 and the prior art example 1. FIG. The figure which shows the result of the flatness test from Example 2 to Example 6 which concerns on this invention. The figure which shows the result of the flatness test from Example 7 to Example 11 which concerns on this invention. The figure which shows the result of the flatness test of the comparative example 2. The figure which shows the external appearance of the polarization conversion unit incorporating the polarization conversion element which concerns on embodiment of this invention. FIG. 26 is an exploded perspective view of the polarization conversion unit of FIG. 25. The figure which shows the liquid crystal projector as an example of the light projection apparatus to which the polarization conversion element which concerns on embodiment of this invention is applied.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

[Wave plate structure]
Below, the structure of the phase difference plate which concerns on embodiment of this invention is demonstrated.
1A and 1B are diagrams showing a configuration of a laminated half-wave plate as an example of a retardation plate according to an embodiment of the present invention, where FIG. 1A is a perspective view, FIG. 1B is an exploded perspective view, and FIG. ) Is a side view.
As shown in FIG. 1A, a laminated half-wave plate 1 according to the present invention includes a first wave plate 2 using an inorganic optical crystal such as quartz having optical rotation and birefringence, and a second wave plate 2. Linearly polarized light that is incident from the light source side as a whole, and has a structure in which the optical plate 3, the third optical plate 6, and the optical plate 3, the optical axis 5, and the optical axis 7 are crossed. The phase of the light A is shifted by 180 (deg), and the polarization plane is converted to linearly polarized light B rotated by θ = 90 (deg) to function as a half-wave plate that emits.
As shown in FIG. 1B, the optical axis azimuth of the first wave plate 2 is θ1, the optical axis azimuth of the second wave plate 4 is θ2, and the optical axis azimuth of the third wave plate 6 is Let θ3. The optical axis azimuth is an angle formed between the crystal optical axis and the polarization plane of linearly polarized light incident on the laminated wave plate.
In the present embodiment, the first wave plate 2, the second wave plate 4, and the third wave plate 6 are laminated. However, the present invention is not limited to this, and the above θ1, θ2, and θ3 are used in the present invention. Need only be set based on the optical design conditions proposed by, and the first wave plate 2, the second wave plate 4, and the third wave plate 6 may be spatially arranged without being stacked. Needless to say, it is good.

Further, as shown in FIG. 1C, the cutting angle of the first wave plate 2 (intersection angle between the normal direction on the main surface of the quartz plate and the crystal optical axis (Z axis)) and the second wavelength The cutting angle of the plate 4 and the cutting angle of the third wave plate 6 are both β (deg) Z (β <90 (deg)).
This is because a wave plate made of quartz or the like increases the thickness by making the cutting angle β smaller than 90 (deg) Z, and the handling in the manufacturing process and the assembling process becomes easy.
By the way, when the laminated half-wave plate 1 of the present invention is used for a polarization conversion element incorporated in a liquid crystal projector, each wavelength band (B (blue: 400 nm band), G (green: 500 nm band), R required for the liquid crystal projector is used. (Red: 675 nm)), it is required that the polarization conversion efficiency is 1 and the phase difference is 180 (deg).
Therefore, the phase difference of the first wave plate 2 with respect to a predetermined design wavelength λ, for example, light of 520 nm (green) is Γ1, the phase difference of the second wave plate 4 is Γ2, and the phase difference of the third wave plate 6 is When Γ3,
Γ1 = 180 (deg) (1)
Γ2 = 180 (deg) (2)
Γ3 = 180 (deg) (3)
The thicknesses of the first, second, and third wave plates 2, 4, and 6 are set so as to satisfy the above.

The relationship between the phase difference Γ for light of wavelength λ and the thickness t of the wave plate is
Γ = 2π / λ × (ne-no) × t
However, ne can be represented by the refractive index of extraordinary light, and ne can be represented by the refractive index of ordinary light.
Therefore, the thickness of the first wave plate 2 is t1, the thickness of the second wave plate 4 is t2, and the third wave plate 6
When the thickness of t3 is
Γ1 = 2π / λ × (ne-no) × t1
Γ2 = 2π / λ × (ne-no) × t2
Γ3 = 2π / λ × (ne-no) × t3
It becomes.
Further, the values of ne and no depend on the value of the design wavelength λ, and ne further depends on the cutting angle β of the wave plate. Therefore, depending on the cutting angle β and the design wavelength λ, Since ne and no change, the value of (ne-no) will change.

By the way, in the case shown in FIG. 1, assuming that the optical rotatory power of the quartz plate is not taken into account, in order to rotate the polarization plane of linearly polarized light by θ (deg), the optical axis azimuth angles θ1, θ2, θ
3 is | θ2−θ1 | = θ / 3, respectively.
| Θ3-θ2 | = θ / 3
However, it is sufficient that θ satisfies the relationship of the angle at which the polarization plane should be rotated.
For example, when the laminated wave plate of the present invention is used for a polarization conversion element, it should act as a half-wave plate for converting incident P-polarized light to S-polarized light, and therefore θ = 90 (deg). The difference between the obtained optical axis azimuth angles is | θ1−θ2 | = 30 (deg), | θ3−θ.
2 | = 30 (deg).
Thus, for example, θ1 = 15 (deg), θ2 = 45 (deg), θ3 = 75 (deg)
), It becomes possible to act as a half-wave plate.
The ranges of the optical axis azimuth angles θ1, θ2, and θ3 are effective within a range of ± 2 (deg) from the set angle in accordance with required specifications or as an allowable error.
However, as described with reference to FIG. 1 (c), by making the cutting angle β smaller than 90 (deg), it becomes easy to be influenced by the optical rotatory power of an optical crystal such as quartz, Since the optical rotation rotates when passing through each wave plate, there arises a problem that a desired polarization conversion efficiency cannot be obtained as a whole laminated wave plate.

In order to correct the influence of the optical rotatory power, that is, when considering the optical rotatory power possessed by the quartz plate, the inventor of the present application, the optical axis azimuth angles of the first wave plate 2 and the third wave plate 6 It came to mind that it is necessary to adjust the rotation axis (optical axis) by adjusting θ1 and θ3.
Based on this, the optical axis azimuth θ1 of the first wave plate and the optical axis azimuth θ3 of the third wave plate are adjusted by the adjustment value correction values a and b,
θ1 = 15 (deg) + a (deg) (4)
θ3 = 75 (deg) −b (deg) (5)
However, a = b
Set to satisfy.
In this case, | θ1-θ2 | <30 (deg) and | θ2-θ3 | <30 (deg).
However, depending on the magnitude of the effect of the optical rotation due to the value of the cutting angle β (the amount of deviation of the rotation of the linearly polarized light due to the optical rotation in the wave plate), depending on the adjustment of the optical axis azimuth, the effect of the optical activity may be reduced. In some cases, the correction cannot be partitioned.
Therefore, in the present invention, when the minimum value (lower limit value) A of the cutting angle β and the cutting angle β satisfy A ≦ β <90 (deg) that can correct the influence of the optical rotation power by adjusting the optical axis azimuth. In addition, the range of values that can be taken by the adjustment amount a of the optical axis azimuth was found by performing various simulations.
Furthermore, as the optimum range of the cutting angle β, by setting the upper limit of the cutting angle at which the thickness of the wave plate is a value that does not cause a problem in handling in order to prevent the wave plate from being broken or damaged during the processing process or the assembly process. In addition, it is possible to obtain a wave plate that achieves both measures for optical rotation and securing an optimum thickness for handling.

First, in the half-wave plate according to the present invention composed of the first wave plate 2, the second wave plate 4, and the third wave plate 6, linearly polarized light A incident from the light source side. The polarization plane of 90 (de
g) In order to realize that the light is converted into the linearly polarized light B that has been rotated and emitted, the basic configuration before correction is considered.
That is, in the first wave plate 2 and the third wave plate 6, the first wave plate 1 and the third wave plate 6 are considered without considering the effect of optical rotation.
The values of the optical axis azimuth θ1 of the wave plate 2 and the optical axis azimuth θ3 of the third wave plate 6 are values before adjustment.

The values of the phase difference and the optical axis azimuth in the above formulas (1), (2), and (3) are ½ as a whole using the first, second, and third wave plates 2, 4, 6. In order to set the phase difference to 180 (deg) in a wide wavelength band desired when the wave plate 1 is formed, the first, second, and third wave plates 2 that constitute the laminated half-wave plate 1; For 4 and 6, predetermined wavelength (for example, 520 nm)
The phase difference Γ1, Γ2, Γ3 and the optical axis azimuth angles θ1, θ2, θ3 are changed variously to obtain the optimum phase difference, conversion efficiency, and the like.
And
Γ1 = 180 (deg) (6)
Γ2 = 180 (deg) (7)
Γ3 = 180 (deg) (8)
θ1 = 15 (deg) (9)
θ2 = 45 (deg) (10)
θ3 = 75 (deg) (11)
When the values of the above formulas (6) to (8) are satisfied, it has been found that the phase difference is 180 (deg) with respect to the light in the three RGB wavelength bands, and the polarization conversion efficiency is almost 1.
Here, the range of values that the design wavelength λ can take is 510 ≦ λ ≦ 530 (nm).
In FIG. 1, the optical axis azimuth angles of the first wave plate 2 and the third wave plate 6 may be interchanged. In other words, the arrangement order of the first wave plate 2 and the third wave plate 6 may be changed with respect to the light incident direction.
Specifically, the optical axis azimuth θ1 of the first wave plate 2 and the optical axis azimuth θ of the second wave plate 4
2 is θ1 = 75 (deg) (9) ′
θ2 = 45 (deg) (10) ′
θ3 = 15 (deg) (11) ′
It can be.

Further, the optical axis azimuth θ1 of the first wave plate 2, the optical axis azimuth θ2 of the second wave plate 4, and the optical axis azimuth θ3 of the third wave plate 6 in FIG. 1 may be obtuse angles.
In this case, the optical axis azimuth θ1 of the first wave plate 2 and the optical axis azimuth θ2 of the second wave plate 4
, The optical axis azimuth θ3 of the third wave plate 6 is
θ1 = 105 (deg) (12)
θ2 = 135 (deg) (13)
θ3 = 175 (deg) (14)
By satisfying the above, the phase difference becomes 180 (deg) with respect to the light in the three wavelength bands, and the polarization conversion efficiency becomes almost 1.
Also in this case, the optical axis azimuth angles of the first wave plate 2 and the third wave plate 6 are expressed by the following formula (12).
The polarization conversion efficiency can be made substantially 1 even if they are interchanged as', (13) ', (14)'.
θ1 = 175 (deg) (12) ′
θ2 = 135 (deg) (13) ′
θ3 = 105 (deg) (14) ′

・・・（１６）

・・・（１７）

・・・（１８）
第１、第２、第３の波長板２、４、６夫々の位相差Γ１、Γ２、Γ３、光学軸方位角度
θ１、θ２、θ３を設定して、式（１６）〜（１８）よりミューラ行列Ｒ１、Ｒ２、Ｒ３
を求める。 Next, a description will be given of whether the above-mentioned optical axis azimuth angles θ1, θ2, and θ3 have been found.
First, a calculation method for finding an example of the laminated half-wave plate according to the present invention will be briefly described. The polarization state after the linearly polarized light passes through the two wave plates can be expressed using a Mueller matrix or a Johns matrix.
E = R3, R2, R1, I (15)
Here, I is a vector representing the polarization state of incident light, and E is a vector representing the polarization state of outgoing light. R1 is the Mueller matrix of the first wave plate 2 in the laminated half-wave plate 1, R2 is the Mueller matrix of the second wave plate 4, and R3 is the Mueller matrix of the third wave plate 6, respectively, It is represented by

... (16)

... (17)

... (18)
The phase differences Γ1, Γ2, Γ3 and optical axis azimuth angles θ1, θ2, θ3 of the first, second, and third wave plates 2, 4, and 6 are set, and a muler is obtained from the equations (16) to (18). Matrix R1, R2, R3
Ask for.

・・・（１９）
Ｅの行列要素Ｓ_０１、Ｓ_１１、Ｓ_２１、Ｓ_３１はストークスパラメータと呼ばれ、偏光
状態を表している。このストークスパラメータを用いて、波長板の位相差Γは次式のよう
に表される。

・・・（２０）
Γ＝（２ｍ−１）×π 但し、ｍは正の整数
このように、式（１９）を用いて位相差を算出することができる。
また、上記のように、図１に示す積層１／２波長板１は、直線偏光の偏光面を、所定の
回転角度θだけ回転させる機能を有しており、例えば、水平方向の振動面を持つ直線偏光
Ａを入力光として、偏光面をθ＝９０（ｄｅｇ）だけ回転（位相変調）させて水平方向の
振動面を持つ直線偏光Ｂとして出射させる。 When the polarization state I of the incident light is set, the polarization state E of the emitted light can be calculated from the equation (15).
The case where a Mueller matrix is used as the matrix will be described. The polarization state E of the emitted light is expressed by the following equation.

... (19)
The matrix elements S ₀₁ , S ₁₁ , S ₂₁ and S ₃₁ of E are called Stokes parameters and represent the polarization state. Using this Stokes parameter, the phase difference Γ of the wave plate is expressed as follows.

... (20)
Γ = (2m−1) × π where m is a positive integer. Thus, the phase difference can be calculated using the equation (19).
Further, as described above, the laminated half-wave plate 1 shown in FIG. 1 has a function of rotating the polarization plane of linearly polarized light by a predetermined rotation angle θ. Using the linearly polarized light A as input light, the plane of polarization is rotated (phase modulation) by θ = 90 (deg) and emitted as linearly polarized light B having a horizontal vibration plane.

FIG. 2 is a diagram for explaining a polarization state in the laminated half-wave plate 1 shown in FIG.
FIG. 4B is a diagram showing the locus of the polarization state on the Poincare sphere, and FIG. 5B is a diagram in which the locus of the polarization state in FIG.
Considering the Poincare sphere in FIG. 2, this phase modulation (90 (deg) rotation) is to modulate from the incident and polarization state P0 to P2, and the necessary phase difference is 180 (deg).
When the laminated half-wave plate 1 functions completely as a half-wave plate, light is incident as linearly polarized light A having a polarization direction parallel to the equator from a predetermined position P0 on the equator. Then, the first wave plate 2 rotates 180 (deg) around the optical axis R1 (2 · θ1) and is moved to P1 (up the equator), and further, the second wave plate 4 moves the optical axis R2 (2. Rotate 180 (deg) around θ2) and move to P2 (on the equator), and further rotate 180 (deg) around the optical axis R3 (2 · θ3) by the third wave plate 6 to P3 (On the equator)
The half-wave plate 1 becomes a linearly polarized light B rotated by θ = 90 (deg) with respect to the linearly polarized light A.
Will be emitted. Note that P3 is a point on the equator rotated 180 (deg) from P0.
As can be seen from FIGS. 2A and 2B, the optical axis R1, the optical axis R2, and the optical axis R3 intersect with the equator because the optical rotation of the quartz plate is not considered here.

FIG. 2C is a diagram (projected on the S1S2 plane) of the locus of the polarization state of the light beam incident on the half-wave plate 1 viewed from the S3 axis direction in the Poincare sphere shown in FIG. is there.
Optical axis azimuth θ1 of the first wave plate 2, optical axis azimuth θ2 of the second wave plate 4, optical axis azimuth θ3 of the third wave plate 6, and linearly polarized light B with respect to linearly polarized light A (incident light) The relation of the rotation angle θ of (emitted light) can be expressed as shown in FIG. 2C on the Poincare sphere.
A triangle OP0P1 connecting the points O, P0, and P1 is an isosceles triangle having the point O as an apex, the optical axis R1 is a bisector of the triangle OP0P1, and the angle formed between the side OP0 and the optical axis R1 is 2θ.
1
A triangle OP1P2 formed by connecting the points O, P1, and P2 is an isosceles triangle having the point O as an apex, and the optical axis R2 is a bisector of the triangle OP1P2, and an angle formed between the side OP0 and the optical axis R2. Becomes 2θ2.
A triangle OP2P3 connecting the points O, P2, and P3 is an isosceles triangle having the point O as an apex, and the optical axis R3 is a bisector of the triangle OP2P3, and an angle formed between the side OP0 and the optical axis R3. Becomes 2θ3.

Furthermore, the product of the matrix E representing the polarization state of the emitted light and the matrix P of the polarizer is calculated, and the obtained light quantity is evaluated to determine the polarization state accurately. This is defined as conversion efficiency.
Specifically, the transmission axis of the matrix P of the polarizer is set to 90 (deg), and from the Stokes parameter of the matrix T obtained from the product of the matrix P and the matrix E representing the output light polarization state, 90 (deg)
) Direction polarization plane component light quantity can be calculated. The product of the matrix E representing the outgoing light polarization state and the polarizer matrix P is given by the following equation.
That is, when the transmission axis of the polarizer matrix P is set to a predetermined angle, and the product of the matrix E representing the polarization state E of the light radiation and the polarizer matrix P is T, T is expressed by the following equation. The

・・・（２２）
ここで、ベクトルＴのストークスパラメータのＳ_０２が光量を表している。入射光量を
１に設定すればＳ_０２が変換効率となる。
従って、積層１／２波長板１の変換効率Ｔは、第１、第２及び第３の波長板２、４、６
の高次モード次数ｎ、所定の波長（例えば波長が、設計波長λ＝５２０ｎｍのとき）での
位相差Γ１、Γ２、Γ３、光学軸方位角θ１、θ２、θ３を様々に変化させて、シミュレ
ーションすることができる。
位相差、変換効率とも積層１／２波長板を透過した後の偏光状態を表す行列Ｅから求め
ることができる。 T = P ・ E (21)
Here, the matrix T represents the conversion efficiency, and is represented by the following equation when represented by the Stokes parameter of the element.

(22)
Here, S ₀₂ of the Stokes parameters of the vector T represents the amount of light. If the amount of incident light is set to 1, S ₀₂ becomes the conversion efficiency.
Therefore, the conversion efficiency T of the laminated half-wave plate 1 is the first, second and third wave plates 2, 4, 6
The phase difference Γ1, Γ2, Γ3 and the optical axis azimuth angles θ1, θ2, θ3 at various wavelengths are varied and simulated at a predetermined wavelength (for example, when the wavelength is the design wavelength λ = 520 nm). can do.
Both the phase difference and the conversion efficiency can be obtained from the matrix E representing the polarization state after passing through the laminated half-wave plate.

Using the above conversion efficiency as an evaluation criterion, the first to third parameters which are various parameters of the laminated half-wave plate
The wave plate 2, 4 and 6 have different high-order mode orders n, respective phase differences Γ1, Γ2, and Γ3 at predetermined wavelengths (for example, a wavelength of 520 nm), and various optical axis azimuth angles θ1, θ2, and θ3. The simulation was performed using a computer.
The simulation was repeated and the above parameters were selected when the conversion efficiency was good in a desired plurality of wavelength bands.

The results will be described below.
The cut angles of the first to third wave plates 2, 4 and 6 of the laminated half-wave plate 1 shown in FIG.
0 (deg) Z (the intersection angle between the normal direction on the main surface of the quartz plate and the optical axis (Z axis) is 90 (
deg)), when the wavelength λ is 520 nm, the phase difference Γ1 and the optical axis azimuth angle θ1 of the first wave plate 2 are 180 (deg), 15.0 (deg), and the position of the second wave plate 4, respectively. The phase difference Γ2 and the optical axis azimuth angle θ2 are 180 (deg) and 45.0 (deg), respectively. The phase difference Γ3 of the third wave plate 6 and the optical axis azimuth angle θ3 are 180 (deg) and 75.0 (deg), respectively. ) If set,
As a result of obtaining the conversion efficiency of the laminated half-wave plate 1 by simulation, a good wavelength-conversion efficiency (polarization conversion efficiency) was obtained.
The ranges of the optical axis azimuth angles θ1, θ2, and θ3 are effective within a range of ± 2 (deg) from the set angle in accordance with required specifications or as an allowable error.

Next, the polarization state when considering the optical rotation power of the wave plate will be described.
FIG. 3 is a diagram showing the polarization state when the optical rotation power of the wave plate is taken into account, and FIG. 3A shows the polarization state of the polarization state when taking into consideration the optical rotation power of the wave plate using a Poincare sphere. Figure, (b)
These are the figures which projected the locus | trajectory of the polarization state in (a) on the S1S3 plane.
As described with reference to FIG. 2, when the laminated half-wave plate 1 functions completely as a half-wave plate, the polarization direction from the predetermined position P0 on the equator is parallel to the equator. When a light beam is incident as the linearly polarized light A, the first wavelength plate 2 causes the optical axis R1 to be centered at 180 degrees.
(Deg) rotated and moved to P1 (on the equator), and further rotated 180 (deg) around the optical axis R2 by the second wave plate 4 to reach P2 (on the equator), and further to the third wavelength. The plate 6 rotates 180 (deg) around the optical axis R3 to reach P3 (on the equator), and becomes a linearly polarized light B rotated by θ = 90 (deg) with respect to the linearly polarized light A to be ½ wavelength. The plate 1 is emitted.

However, in the case of FIG. 3, as shown in FIG. 3 (b), the optical axes R1, R2, and R3 are lifted to the north pole side compared to FIG. 3 (a) due to the effect of optical rotation (optical axis R1 ′). , Optical axis R2 '
, Optical axis R3 ′).
The angle that is the lift amount of the optical axes R1, R2, and R3 can be 2ρ. Here, ρ is the optical rotation angle of the crystal, and ρ depends on the value of the cutting angle β. As the value of β decreases, the lift amount increases and the influence of the optical rotation power increases.
For this reason, the light rotated 180 (deg) around the optical axes R1 ′, R2 ′, R3 ′ is shown in FIG.
Point P1 ′ (≠ P1) that cannot reach points P1 and P2 on the equator in (a) and is shifted to the north pole side
), Point P2 ′ (≠ P2), point P3 ′ (≠ P3).
Therefore, in this state, the laminated wave plate represented by the Poincare sphere in FIG. 3 cannot function completely as a half-wave plate.
In this case, the optical axis R1 ′ and the optical axis R3 ′ are adjusted by adjusting the optical axis azimuth angle of each wave plate.
Are shifted as shown in FIG. 3C (optical axis R1 ″, optical axis R3 ″) so that the linearly polarized light reaches the point P2.
Specifically, as described in FIG. 1, the optical axis azimuth θ1 of the first wave plate 2 and the optical axis azimuth θ2 of the second wave plate 4 are
θ1 = 15.0 (deg) + a (deg)
θ3 = 67.5 (deg) −b (deg)
a = b ≠ 0 (deg)
To satisfy. In this case, the optical axis R1 (optical axis R1 ″), the optical axis R3 (optical axis R3 ″)
Is closer to the P1 side and the P2 side than the case shown in FIG.
The ranges of the optical axis azimuth angles θ1, θ2, and θ3 are effective within a range of ± 2 (deg) from the set angle in accordance with required specifications or as an allowable error.

Next, in consideration of the optical rotatory power in the wave plate, the optical rotatory power can be corrected as a parameter in the first wave plate 2, the second wave plate 4, and the third wave plate 6 (the optical axis azimuth is changed). Adjust the value
1/2 that can achieve high average polarization conversion efficiency (for example, 0.8 or more) in a wide wavelength band
A wave plate can be realized) When the lower limit value A of the cutting angle β and the cutting angle β satisfy the lower limit value A ≦ β <90, the correction values a and b of the optical axis azimuth angles θ1 and θ2 can be obtained. It was.
Specifically, the average loss of polarization conversion efficiency is 20% or less from wavelength λ1 = 400 nm to wavelength λ2 = 700 nm, and the average loss of polarization conversion efficiency is 10% or less from wavelength λ3 = 500 nm to wavelength λ4 = 600 nm. The range of the above parameters was determined.
The polarization conversion efficiency can be obtained by a simulation using the Stokes parameter.
Since the calculation was performed so that the polarization conversion efficiency was good at a wavelength of 500 nm to 600 nm, G
A wave plate suitable for a projector that places importance on the (green) band can be obtained.

FIG. 4 shows the lower limit value A of the cutting angle, the correction value a (= b) of the optical axis azimuth, and the thickness t (t1,
It is a graph which shows the simulation result of t2, t3).
In the graph of FIG. 4, the lower limit value A of the cutting angle β that can correct the optical rotation power by adjusting the azimuth angle of the optical axis becomes smaller as the value of the cutting angle is decreased to increase the thickness of the wave plate. It shows that. The correction values (a, b) of the optical axis azimuth required for optical rotation correction are as follows:
It increases as the thickness of the wave plate increases.
As a result of simulation, when the lower limit value A of the cutting angle β satisfies 13 (deg) ≦ A,
It has been found that the optical rotation can be corrected by adjusting the optical axis azimuth.
In particular, as shown in the graph of FIG. 4, when the lower limit value A of the cutting angle satisfies the following approximate (5th order) polynomial, the above simulation condition is satisfied (from the wavelength λ1 = 400 nm to the wavelength λ2 = 700 nm). The average loss of polarization conversion efficiency is 20% or less, and the average loss of polarization conversion efficiency is 10% from the wavelength λ3 = 500 nm to the wavelength λ4 = 600 nm.
The optical rotation can be corrected as follows.
A = -7E-06a ⁵ + 0.0006a ⁴ + 0.0132a ³ + 0.1204a ² +0.
4284a + 13.155
In this case, the correction value a satisfies −15.0 (deg) ≦ a ≦ 8.0 (deg).
The lower limit A is A = 24.5 (deg) when a = -15.0 (deg),
When a = 3.0 (deg), A = 13.0 (deg), when a = 8.0 (deg), A =
33.0 (deg).
When the thicknesses t1, t2, and t3 of the first wave plate 2, the second wave plate 4, and the third wave plate 6 are set to t1 = t2 = t3 = t, the plate thickness t is a correction value a. And the following approximate (sixth order) polynomial:
t = 4E-07a ⁶ + 9E-06a ⁵ + 1E-05a ⁴ −0.0008a ³ −0.005
8a ² −0.0146a + 0.5443
In this case, when a = -15.0 (deg), the plate thickness t is 0.1650 (mm), and a
When == 3.0 (deg), the thickness t is 0.5538 (mm). Furthermore, a = 8.0
In (deg), the plate thickness t = 0.0956 (mm).

FIG. 5 is a diagram showing the conversion efficiency of the laminated half-wave plate 1 of the present invention for wavelengths from 400 nm to 700 nm. The design wavelength λ of each wavelength plate is 520 nm, and the correction value a is −3.0 (de
It is a graph which shows the change of the polarization conversion efficiency for every wavelength when it is set as g) and an incident angle is changed from -10 (deg) to +10 (deg).
The laminated half-wave plate 1 of the present invention has an incident angle of −5 (in the range of 450 nm to 650 nm.
deg) to 10 (deg), the polarization conversion efficiency is 0.8 or more, indicating high polarization conversion efficiency.
Furthermore, in the range of 550 nm to 600 nm (G band), the polarization conversion efficiency is approximately 0.8 to 1.0 or more at each incident angle, and very high conversion efficiency is exhibited.
In this case, the minimum value A of the cutting angle β is 13.0 (deg).
The blue, green, and red wavelengths used in the liquid crystal projector are 400 nm band, 500 nm band, 6
Since it is a 75 nm band, the laminated half-wave plate 1 having the above parameters can be satisfactorily applied to a liquid crystal projector or the like.
Note that the upper limit of the cutting angle β is preferable in terms of handling, for example, as in the case of FIG.
To be 3mm or more,
Γ = 2π / λ × (ne-no) × t
It can be derived from the equation.

FIG. 6 is a diagram showing the conversion efficiency of the laminated half-wave plate 1 according to the present invention for wavelengths from 400 nm to 700 nm. The design wavelength λ of each wavelength plate is also 520 nm, and the correction value a is −15.
It is a graph which shows the change of the polarization conversion efficiency for every wavelength when it is set to 0 (deg) and an incident angle is changed from -10 (deg) to +10 (deg).
The laminated half-wave plate 1 of the present invention exhibits a high polarization conversion efficiency with a polarization conversion efficiency of 0.7 or more at an incident angle of 0 (deg) to 10 (deg) at wavelengths in the entire range of 400 nm to 700 nm. ing.
Further, when the incident angle is -5 deg to 10 deg, the polarization conversion efficiency is approximately 0.9 or more in the range of 500 nm to 600 nm (G band).
In this case, the minimum value A of the cutting angle β is 24.5 (deg).
The blue, green, and red wavelengths used in the liquid crystal projector are 400 nm band, 500 nm band, 6
Since it is a 75 nm band, the laminated half-wave plate 1 having the above parameters can be satisfactorily applied to a liquid crystal projector or the like.

FIG. 7 is a graph showing the conversion efficiency of the laminated half-wave plate 1 of the present invention for wavelengths from 400 nm to 700 nm. The design wavelength λ of each wave plate is also 520 nm, and the correction value a is 8.0 (
deg), and the incident angle is changed from −10 (deg) to +10 (deg).
It is a graph which shows the change of the polarization conversion efficiency for every wavelength.
The laminated half-wave plate 1 of the present invention has a polarization conversion efficiency of 0.7 or more at each incident angle,
Even in the range of 500 nm to 600 nm (G band), the incident angle is −5 (deg) to 10 (d
eg), the polarization conversion efficiency is approximately 0.9 or more.
In this case, the minimum value A of the cutting angle β is 24.5 (deg).
The blue, green, and red wavelengths used in the liquid crystal projector are 400 nm band, 500 nm band, 6
Since it is a 75 nm band, the laminated half-wave plate 1 having the above parameters can be satisfactorily applied to a liquid crystal projector or the like.
The wavelength band to which the laminated half-wave plate should correspond is not only RGB but also other colors added.
It may be possible to cope with four wavelengths and five wavelengths.
If the design wavelength λ is designed to be 550 nm, the polarization conversion efficiency is most favorable at the center wavelength in the G band, and a more suitable wave plate for use in a projector can be realized.
As described above, according to the present invention, the optical performance of a wave plate made of an inorganic crystal material such as quartz is corrected, the incident angle dependency is improved, and a high-performance wave plate having high polarization conversion efficiency is obtained. I can do it.

FIG. 8 is a diagram showing an example of a polarization conversion element to which the laminated wave plate of the present invention is applied.
The polarization conversion element shown in FIG. 8 includes an element body (optical element) 10 that is the above-described PBS array,
A phase difference plate (laminated 1 / layer) made of an inorganic optical crystal such as quartz, which is selectively bonded to the element body 10.
2 wavelength plate) 1.
Since inorganic optical crystals such as quartz are excellent in thermal conductivity, they are superior in heat resistance and have no fear of deterioration of optical properties due to high heat, compared to a phase plate made of an organic material described in the background art.
In addition to quartz, lithium tantalate, sapphire, etc. can be applied as the material of the retardation film.
As shown in FIG. 26, which will be described later, in the polarization conversion element, the two element bodies 10 are connected and incorporated, but only a part is shown in FIG.
As shown in FIG. 1, the element body 10 includes a plurality of translucent substrates 11 and a plurality of translucent substrates 11.
Are provided between the plurality of light-transmitting substrates 11 and the light-transmitting substrates 11 are bonded to each other. And an adhesive layer 14.

The element body 10 includes a light incident surface 16 and a light emitting surface 17 that are substantially parallel to each other.
Further, the element body 10 has a plurality of light-transmitting substrates 11 formed of a polarization separation film (polarization separation unit) 12 and a reflection film (reflection film) by a joint surface 11 a having a predetermined inclination angle with respect to the light incident surface 16 or the light emitting surface 17. Bonded by the adhesive layer 14 with the reflective portions 13 alternately interposed therebetween.
The polarization separation film 12 selectively transmits P-polarized light and reflects S-polarized light among input light (S-polarized light and P-polarized light) from the outside.
The reflection film 13 reflects the S-polarized light reflected by the polarization separation film 12 toward the light exit surface 17.
Here, the adhesive layer 14 has a thickness of 5 μm or more and 10 μm or less.
Since the adhesive layer 14 is formed of an ultraviolet curable adhesive mainly composed of modified acrylate or modified methacrylate, the thickness can be set as described above.
Conventional ultraviolet curable adhesives do not have modified acrylate or modified methacrylate as a main component, and thus have a high viscosity and have an adhesive layer thickness of 10 μm to 20 μm.

Thus, when the thickness of the adhesive layer exceeds 10 μm, distortion occurs at the end of the adhesive layer in the manufacturing process of the polarization conversion element described later with reference to FIGS. 14 to 20. Therefore, when the light incident surface 16 and the light emitting surface 17 are polished (FIG. 20), the translucent substrate 11 in the vicinity of the strain is used.
The corners of will be shaved. As a result, when the phase difference plate 1 is bonded to the light emitting surface 17 of the light transmissive substrate 11, a gap is generated between the light transmissive substrate 11 and the phase difference plate 1, and bubbles are generated. .
Thereby, the translucent board | substrate 11 and the phase difference plate 1 are not fully joined, but the phase difference plate 1 becomes easy to peel off.
Further, the light transmittance is reduced by the bubbles generated between the translucent substrate 11 and the phase difference plate 1.
9 and 10 are diagrams for explaining the problem of the conventional polarization conversion element in detail.
Further, in the conventional polarization conversion element shown in FIG. 9, the adhesive layer 93 is thick as described above. When the laminate is cut out in such a state that the adhesive layer 93 is thick, the adhesive layer 93 is formed at the end of the adhesive layer 93. Distortion will occur. If the cut surface is polished in a state where this distortion occurs, the corner portion 981 of the translucent substrate 98 in the vicinity of the adhesive layer 93 is scraped off as shown in FIG. This
A gap is generated in the bonding layer 96 for bonding the retardation plate 97 to the element body 95, and the retardation plate 97.
Are easily peeled off, and bubbles 961 are formed, resulting in a decrease in light transmittance.
In addition, there is a problem in that a region where light is effectively transmitted is reduced by cutting off the corner portion 981 of the translucent substrate 98 in the vicinity of the adhesive layer 93.

On the other hand, when the thickness of the adhesive layer is less than 5 μm, when dust or the like is mixed into the adhesive layer, the adhesive strength of the adhesive layer is reduced by the dust or the like.
However, if the thickness of the adhesive layer is 5 μm or more and 10 μm or less, the corners of the light-transmitting substrate 11 are difficult to be scraped, so that no bubbles are generated, and the retardation plate 1 is easily peeled off from the light-transmitting substrate 11.
It is possible to solve the problem that the light transmittance is lowered.
Examples of the adhesive used in the present embodiment include UT20, HR54 (trade name, manufactured by Adel Co., Ltd.), and the like.

In FIG. 8, the phase difference plate 1 has a light emitting surface 1 of the translucent substrate 11 by the bonding layer 21.
7 is bonded to the upper region of the polarization separation film 12.
The retardation plate 1 is a half-wave plate made of quartz as described above, and converts P-polarized light transmitted through the polarization separation film 12 into S-polarized light.
However, in the polarization conversion element 1, when the P polarization light is emitted in a unified manner, the phase difference plate 1
Is provided above the reflective film 13.
The bonding layer 21 is a plasma polymerized film for molecular bonding, and its main material is polyorganosiloxane. The plasma polymerized film includes a Si skeleton formed by a plasma polymerization method and including a siloxane bond and a crystallinity of 45% or less, and a desorber made of an organic group bonded to the Si skeleton. Then, by applying energy, the leaving group existing in the vicinity of the surface is released from the Si skeleton, thereby exhibiting adhesiveness.

FIG. 11 is a schematic diagram illustrating the composition of the plasma polymerized film, where (A) shows the composition before applying energy, and (B) shows the composition after applying energy.
As described above, as shown in FIG. 11A, the plasma polymerized film includes the siloxane bond (Si—O) 21A including the Si skeleton 21B and the leaving group 21C bonded to the Si skeleton 21B. .
When energy is applied to the bonding layer 21 made of a plasma polymerized film as shown in FIG. 11A, as shown in FIG. 2B, the leaving group 21C shown in FIG. Si skeleton 2
Desorb from 1B. Thereby, active hands 21D are generated on the surface and inside of the bonding layer 21 and are activated.
As a result, adhesiveness is developed on the surface of the bonding layer 21. When such adhesiveness is expressed, the bonding layer 21 can be strongly bonded. The crystallinity of the Si skeleton 21B of the bonding layer 21 is 45.
% Or less is preferable, and 40% or less is more preferable. As a result, Si
The skeleton 21B includes a sufficiently random atomic structure, whereby the Si skeleton 21B
The characteristic of becomes obvious.
Here, “activate” means that the bonding groups 21C on the surface and inside of the bonding layer 21 are desorbed and bonds that are not terminated in the Si skeleton 21B (hereinafter referred to as “unbonded hands” or “dangling hands”). It is also referred to as a “ring bond”), a state in which this dangling bond is terminated by a hydroxyl group (OH group), or a state in which these states are mixed.
Accordingly, the active hand 21D means an unbonded hand (dangling bond) or a bond in which the unbonded hand is terminated by a hydroxyl group. According to such an active hand 21D, the bonding layer 2
1 can be firmly joined.

As described above, when energy is applied to the plasma polymerized film, active hands are generated on the surface and inside thereof, so that strong adhesiveness is exhibited in the plasma polymerized film.
Moreover, since it is an inorganic joining method that does not use an adhesive, the optical characteristics are not affected by the deterioration of the adhesive.
Further, since the thickness of the adhesive layer 14 is not less than 5 μm and not more than 10 μm, the corners of the translucent substrate 11 are hard to be scraped, so that the bonding layer 21 is formed without a gap by the plasma polymerization method. And the phase difference plate 1 can be strongly bonded.
In addition, the joining method of the phase difference plate 1 and the light emission surface 17 is not restricted to this plasma polymerization method, You may join by the adhesive agent which has the above-mentioned modified methacrylate or modified acrylate as a main component.

Further, the bonding layer 21 may be formed not only by a plasma polymerization method but also by an atomic diffusion bonding method.
In the atomic diffusion bonding method, first, a microcrystalline continuous thin film is formed on each of the light-transmitting substrate 11 and the phase difference plate 1 constituting the element body 10 by vacuum film formation such as sputtering or ion plating in a vacuum vessel. Film. Then, the microcrystalline continuous thin films are overlapped during film formation or after film formation to cause atomic diffusion at the bonding interface and the crystal grain boundary, so that the light-transmitting substrate 11 and the phase difference plate 1 are firmly fixed. It is a method of joining.
In addition to superimposing the microcrystalline continuous thin films, the translucent substrate 11 and the retardation plate 1
An atomic diffusion bonding can also be performed by forming a microcrystalline continuous thin film on one of them, forming a microcrystalline structure on the other, and superimposing these microcrystalline continuous thin films on the microcrystalline structure.
Also in this case, since it is an inorganic joining method that does not use an adhesive, the optical characteristics are not affected by the deterioration of the adhesive.

FIG. 12 is an exploded perspective view showing a polarization conversion element according to another embodiment.
FIG. 13 is an enlarged cross-sectional view of a part of the polarization conversion element of FIG.
In addition, about the structure similar to FIG. 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.
The polarization conversion element shown in FIGS. 12 and 13 is joined to the element body 10 as a PBS array, and functions as a half-wave plate, and the polarization plane of incident linearly polarized light is 90 (de).
g) A quartz phase difference plate 1 that emits light after rotation.
The element main body 10 has a substantially rectangular parallelepiped shape, and the end portions in the longitudinal direction where the two element main bodies 10A and 10B face each other are bonded to each other, and are in a symmetrical relationship with respect to the bonding surface 10C.
The element body 10 has a light incident surface 10D and a light emitting surface 10E that are substantially parallel to each other.
In addition, the element body 10 includes the polarization separation films 12 and the reflection films 13 that are alternately arranged along the longitudinal direction between the plurality of translucent substrates 11.
The plurality of translucent substrates 11 are bonded to each other by a bonding surface 11a having a predetermined inclination angle with respect to the light incident surface 10D or the light emitting surface 10E.

The polarization separation film 12 and the reflection film 13 are alternately provided at the boundary portion 11 </ b> B between the plurality of translucent substrates 11.
The polarization separation film 12 separates the light incident on the light incident surface 10D into two different types of linearly polarized light whose polarization directions are orthogonal to each other, transmits one linearly polarized light, and reflects the other linearly polarized light.
In the present embodiment, the polarization separation film 12 selectively transmits P-polarized light among the randomly polarized light incident on the light incident surface 10D and reflects S-polarized light.
The reflective film 13 reflects the other linearly polarized light reflected by the polarization separation film 12 and changes the direction of the optical path. That is, the reflection film 13 converts the S-polarized light reflected by the polarization separation film 12 into the light exit surface 10.
Reflect toward E.
As shown in FIG. 13, the element body 10 includes an adhesive layer 14 that joins a plurality of translucent substrates 11 to each other.

Here, the adhesive layer 14 can use an optical adhesive such as an ultraviolet curing type. When an ultraviolet curable adhesive is used, the viscosity is high, and the thickness of the adhesive layer 14 is about 10 μm or more 2
0 μm or less.
Further, when an ultraviolet curable adhesive mainly composed of modified acrylate or modified methacrylate is used, the thickness of the adhesive layer 14 can be reduced to 5 μm or more and 10 μm. Examples of the UV curable adhesive mainly composed of modified acrylate or modified methacrylate include UT20.
HR154 (trade name, manufactured by Adel Co., Ltd.) and the like.
The adhesive layer 14 has a predetermined thickness W1.

The phase difference plate 1 (20A, 20B) is disposed on each of the light emitting surfaces 10E of the two element bodies 10A, 10B.
The phase difference plate 1 causes a phase difference of 180 (deg) to occur in the P-polarized light transmitted through the polarization separation film 12 and rotates the polarization plane of the P-polarized light by 90 (deg), so that it is reflected by the reflection film 13. It is converted into linearly polarized light parallel to the polarization plane of the S-polarized light, that is, converted into S-polarized light and emitted.
Moreover, as shown in FIG. 12, the phase difference plate 1 has a comb shape (border shape).
The phase difference plate 1 (20A, 20B) is bonded to the element body 10 and does not transmit light.
0C (1C1, 1C2) and a phase difference portion 1D extending from the base portion 20C and transmitting light (
1D1, 1D2).
That is, the base portion 20 </ b> C is disposed outside the effective area (E) that is the optical region of the element body 10. The base 20C is joined along the longitudinal direction, that is, along the direction in which the polarization separation film 12 and the reflection film 13 are alternately arranged.

The base portion 1C1 of one retardation plate 1A is joined to one end portion 10F among the end portions parallel to the longitudinal direction of the element body 10, and the base portion 1C2 of the other retardation plate 1B is The phase difference plate 1A is close to the tip portion 1E1 of the phase difference portion 1D1.
That is, the base portion 1C1 of one phase difference plate 1A is the phase difference portion 1D of the other phase difference plate 1B.
2 is close to the tip portion 1E2, and the base portion 1C2 of the other phase difference plate 1B is close to the tip portion 1E1 of the phase difference portion 1D1 in the one phase difference plate 1A.
Note that the base 20C has a long rectangular main plane and a width of, for example, about 3 mm to 4 mm.

The base 20C is bonded to the element body 10 by a bonding film (not shown).
Similar to the adhesive layer 14, this bonding film is provided by an optical adhesive such as an ultraviolet curing type or a plasma polymerization film. The bonding film is not disposed on the optical path, and is an effective area E that is an optical region.
Therefore, it is desirable to form only between the base 20C and the end edges 10F and 10G parallel to the longitudinal direction of the element body 10.
The phase difference plate 1 (phase difference portion 1D) has a so-called strip shape, and the thickness thereof is the same as that of the base portion 20C. The phase difference portion 1 </ b> D extends from the base portion 20 </ b> C and is disposed in an upper region of the polarization separation film 12 on the light exit surface 10 </ b> E of the element body 10. A plurality of adjacent phase difference portions 1D are arranged with a gap W2 having a predetermined width from each other, and the S reflected by the reflective film 13 is reflected in the gap W2.
The polarized light passes as it is.
As shown in FIG. 13, the phase difference portion 1 </ b> D has a light incident surface 1 </ b> F that faces the light emitting surface 10 </ b> E of the element body 10.

A slight gap W3 is provided between the light incident surface 1F of the phase difference portion 1D and the light emitting surface 10E of the element body 10. Therefore, the light incident surface 1F of the phase difference portion 1D and the optical element 310
It is desirable that an antireflection film (not shown) is formed on each of the light emitting surfaces 10E.
According to the configuration of FIGS. 12 and 13, the phase difference portion 1 </ b> D of the phase difference plate 1 is not bonded to the element main body 10 with an adhesive, and therefore it is possible to avoid deterioration of optical characteristics due to deterioration of the adhesive.
Further, since the plurality of phase difference portions 1D are integrated with the base portion 20C, the phase difference plate 1 can be easily assembled to the element body 10.

Next, the manufacturing process of the element body 10 will be described in more detail.
The manufacturing process is roughly divided into a film forming process, an adhesion process, a cutting process, and a polishing process.
14 to 19 are diagrams for explaining a manufacturing process of the polarization conversion element according to the present embodiment, particularly the element body.
[Film formation process]
In the first film formation step, as shown in FIG. 14, first, a plurality of translucent substrates (colorless and transparent substrates such as glass) 11A are prepared. These translucent substrates 11A have first surfaces 1 that are substantially parallel to each other.
1A1 and second surface 11A2.
Among the plurality of translucent substrates 11A, on the first surface 11A1 of some translucent substrates 11A,
A polarization separation film 12 is formed, and a reflection film 13 is formed on the second surface 11A2.
Any of these films is formed on the first surface 11A1 and the second surface 11A2 of the other translucent substrate 11A, or any film is not formed.

[Adhesion process]
In the bonding step shown in FIG. 15, the translucent substrate 1 on which the polarization separation film 12 and the reflection film 13 are formed.
1A and the translucent substrate 11A on which these films are not formed are alternately bonded by an adhesive 14A. At this time, the polarization separation films 12 and the reflection films 13 are alternately stacked with the light-transmitting substrate 11A interposed therebetween.
Here, an adhesive mainly composed of a modified acrylate or a modified methacrylate is used as the adhesive 14A, and the coating amount is adjusted so that the thickness after curing is 5 to 10 μm.

Next, as shown in FIG. 16, ultraviolet rays are irradiated from a direction substantially perpendicular to the first surface 11A1 of the translucent substrate 11A. In addition, since ultraviolet rays pass through the polarization separation film 12 and the reflection film 13,
In FIG. 16, all the adhesives 14A are cured simultaneously.
Thereby, the adhesive layers 14 are formed between the polarization separation film 12 and the translucent substrate 11A and between the reflective film 13 and the second translucent substrate, respectively. And the laminated body 400 with which the some translucent board | substrate 11A was joined is formed.
In addition, you may irradiate an ultraviolet-ray from the direction substantially parallel to 1st surface 11A1 of 11 A of translucent board | substrates.

Here, the relationship between the curing conditions of the adhesive 14A and the adhesive strength of the adhesive layer 14 obtained by each curing condition will be described.
As shown in Table 1 below, curing test 1 to curing test 7 were carried out by changing the amount of ultraviolet (UV) irradiation. As a result, the tensile strength was as shown in Table 1 and FIGS. 17 (A) and (B), and the shear strength was as shown in Table 1 and FIGS. 18 (A) and (B).
That is, as shown in FIGS. 17A and 17B, the ultraviolet irradiation amount is 15,000 mJ / c.
m ² or more 45,000mJ / cm ² or less, particularly 20,000mJ / cm ² or more 35,00
The case of 0 mJ / cm ² or less is preferable because the tensile strength of the adhesive layer 14 is increased. Also, FIG.
As shown in (A) and (B), the ultraviolet irradiation amount is 15,000 mJ / cm ² or more and 60,00.
In the case of 0 mJ / cm ² or less, especially 25,000 mJ / cm ² or more and 50,000 mJ / cm ² or less, the shear strength of the adhesive layer 14 is increased, which is preferable. In Table 1, each curing test is performed twice.

The tensile strength test and the shear strength test were carried out by the following test methods. 10mm x
A test product prepared by bonding two white glass plates of 10 mm in size with an adhesive 14A is subjected to a tensile load in a direction perpendicular or parallel to the bonding surface with a tensile tester, and the two white glass plates are The weight when separated was measured.

















[Table 1]

Next, as shown in FIG. 19, as a cutting process, the first surface 11A1 and a predetermined angle θ (about 45).
The laminated body 400 is cut almost in parallel at a cutting plane forming a degree), and the laminated block 410 is cut out.
In the subsequent polishing step shown in FIG. 20, the cut surface 410A of the cut laminated block 410 is cut.
Is polished by the polishing apparatus 500, whereby the element body 10 of the polarization conversion element 1 is obtained.

[Heat resistance test]
According to Example 1 and Comparative Example 1, the heat resistance of the adhesive (adhesive layer) used in the present invention was evaluated.
FIG. 21 is a diagram showing a heat resistance test of Example 1 and Conventional Example 1.
In Example 1, two glass plates were bonded together with an adhesive (UT20, manufactured by Adel Co., Ltd.) and irradiated with a predetermined amount of ultraviolet rays. Thereby, the test piece 600 of Example 1 was produced.
On the other hand, in Comparative Example 1, two glass plates were bonded together with a conventional adhesive (PHOTO Bond 300 Sunrise MSI Co., Ltd.) and irradiated with a predetermined amount of ultraviolet rays. This
A test piece 601 of Comparative Example 1 was produced.
When these test pieces 600 and 601 are fixed in the fixed frame 610, the test pieces 600 and 601 are assembled in a place where the polarization conversion element of the projector is to be installed, and the light from the light source lamp is irradiated on the test pieces 600 and 601. The projector cooling mechanism was adjusted so that the temperature of the test piece was 120 ° C. FIG. 21 shows the test results when left in this environment for 3800 hours.

As shown in FIG. 21, yellowing 620 was partially observed in the adhesive layer of the test piece 601, while yellowing was not observed in the adhesive layer of the test piece 600.
Furthermore, as a result of continuing to leave the test pieces 600 and 601 in this environment, after 4800 hours,
In the adhesive layer of Test 601, severe yellowing was observed. On the other hand, in the adhesive layer of the test piece 600, a slight yellowing was observed so as not to affect the optical characteristics.
Therefore, it can be seen that the adhesive layer formed by the adhesive of the present invention is excellent in heat resistance.

[Flatness test]
(Example 2 to Example 11 and Comparative Example 2)
From Example 2 to Example 11 and Comparative Example 2, the flatness of the light incident surface and the light exit surface of the polarization conversion element of the present invention was evaluated.
FIG. 22 is a diagram showing the results of flatness tests from Example 2 to Example 6 according to the present invention, and FIG. 23 is the results of flatness tests from Examples 7 to 11 according to the present invention. FIG. 24 is a diagram showing the results of the flatness test of Comparative Example 2.
(Example 2 to Example 6)
In Example 2, an element body 10 as shown in FIG. 26 described later was produced using the same adhesive as in Example 1. And the left element main body 10 was used among two right and left element main bodies 10 shown by FIG. Then, the light incident surface 1 of the element body 10 is measured by the following measurement method.
A cross-sectional view at the approximate center of 6 was obtained. Here, the cross-sectional view is a cross-sectional view in the left-right direction of FIG.
In the obtained cross-sectional view, a convex portion that swelled relatively upward was selected, and the vertices of the concave portions near the left and right of the convex portion were connected by lines. The distance from this line to the top of the convex portion was converted on the scale of the vertical axis to calculate the “height difference”.

In Example 3 to Example 6, the element body 10 was produced in the same manner as in Example 2, and the light incident surface 16 was measured to obtain a cross-sectional view. From the cross-sectional view, two “height differences” were calculated in the same manner as in Example 2. FIG. 22 shows the results.
(Examples 7 to 11 and Comparative Example 2)
In Example 7 to Example 11, sectional views were obtained in the same manner as in Example 2 for the light emitting surface 17 of the element body 10 produced in Examples 2 to 6, respectively. From the obtained cross-sectional view, two “level differences” were calculated in the same manner as in Example 2.
In Comparative Example 2, an element body was prepared in the same manner as in Example 2 except that the same adhesive as in Comparative Example 1 was used as the adhesive, and a cross-sectional view of the light emission surface was obtained. Two points of “height difference” were calculated from the obtained cross-sectional view in the same manner as in Example 2.

The results of Example 7 to Example 11 and Comparative Example 2 are shown in FIGS.
As a method for measuring the cross-sectional view, a laser interferometer G102S (Fujinon Co., Ltd. (currently manufactured by Fuji Film Co., Ltd.)) is used to irradiate the light incident surface or light output surface of the device body, and the reflected light from the device body is originally Interference fringes are obtained by interfering with the parallel light. The wavelength of light set by the laser interferometer is 685 nm.
By analyzing the obtained interference fringes with interference fringe analysis software (Fujinon Co., Ltd. (currently Fuji Film Co., Ltd.)), a cross-sectional view of the light incident surface or the light emitting surface is obtained.
As shown in FIGS. 22 and 23, in Examples 2 to 11 using the adhesive of the present invention, the flatness is excellent because the height difference between the light incident surface and the light exit surface is small. all right.
On the other hand, as shown in FIG. 24, in the comparative example using the conventional adhesive agent, it was found that the flatness was poor because the height difference on the light incident surface was large.

FIG. 25 is a diagram illustrating an appearance of a polarization conversion unit incorporating the polarization conversion element according to the embodiment of the present invention.
FIG. 26 is an exploded perspective view of the polarization conversion unit of FIG.
The polarization conversion unit 120 shown in FIGS. 25 and 26 includes a unit frame 200, the polarization conversion element 1 of the present invention, a light shielding plate 210, a lens array 220, and a clip 230. A polarization conversion element 1 having two polarization conversion element bodies to be described later is inserted from one opening surface (lower surface in FIG. 26) side of the unit frame 200, and the other opening surface (upper surface in FIG. 26).
From the side, the light shielding plate 210 and the lens array 220 are inserted in this order. These optical elements 210 and 220 are sandwiched from four directions by four clips 230 in a state of being accommodated in the unit frame 200. Since the clip 230 is formed of an elastic body, it can be easily attached and detached, and each component of the polarization conversion unit 120 can be easily attached to and detached from the unit frame.
The unit frame 200 allows the polarization conversion element 1 to be placed on the liquid crystal projector in such a posture that the angle at which the light beam from the light source is incident on the polarization conversion element 1 (especially a PBS film described later) is always constant and PS conversion can be performed accurately. Can be incorporated.

FIG. 27 is a diagram showing a liquid crystal projector as an example of a light projecting device to which the polarization conversion element according to the embodiment of the present invention is applied.
A projection display apparatus (liquid crystal projector) 100 shown in FIG. 27 includes a light source 110, a first lens array 111, and a polarization conversion unit 120 incorporating the polarization conversion element according to the present invention.
And a superimposing lens 121 are provided. Further, a color light separation optical system 130 including dichroic mirrors 131 and 132 and a reflection mirror 133 is provided. Furthermore, a light guiding optical system including an incident side lens 140, a relay lens 141, and reflection mirrors 142 and 143 is provided. Three field lenses 144, 145, 146
And three liquid crystal light valves 150R, 150G, and 150B, a cross dichroic prism 160, and a projection lens 170.
The reflection mirror 146 has a function of reflecting the light emitted from the superimposing lens 121 in the direction of the color light separation optical system 130. The color light separation optical system 130 has a function of separating light emitted from the superimposing lens 121 into three color lights of red, green, and blue by two dichroic mirrors 131 and 132. The first dichroic mirror 131 includes a superimposing lens 121.
The red light component of the light emitted from the light is transmitted, and the blue light component and the green light component are reflected. The red light transmitted through the first dichroic mirror 131 is reflected by the reflection mirror 133, passes through the field lens 144, and reaches the liquid crystal light valve 150R for red light. The field lens 144 converts each partial light beam emitted from the superimposing lens 121 into a light beam parallel to the central axis (principal light beam). The same applies to the field lenses 145 and 146 provided in front of the other liquid crystal light valves.

Of the blue light and green light reflected by the first dichroic mirror 131, the green light is reflected by the second dichroic mirror 132, passes through the field lens 145, and reaches the liquid crystal light valve 150G for green light. On the other hand, the blue light passes through the second dichroic mirror 132, passes through the light guide optical system, that is, the incident side lens 140, the reflection mirror 142, the relay lens 141, and the reflection mirror 143, and further passes through the field lens 146. The liquid crystal light valve 150B for blue light is reached.
The light guide optical system is used for blue light because the optical path length of the blue light is longer than the optical path lengths of the other color lights, thus preventing a reduction in light utilization efficiency due to light diffusion or the like. It is to do.
That is, this is to transmit the light beam incident on the incident side lens 140 to the field lens 146 as it is.

The three liquid crystal light valves 150R, 150G, and 150B have a function as light modulation means for modulating incident light according to given image information (image signal). As a result, the color lights incident on the three liquid crystal light valves 150R, 150G, and 150B are modulated in accordance with given image information to form images of the respective color lights.
The three colors of modulated light emitted from the three liquid crystal light valves 150R, 150G, and 150B are incident on the cross dichroic prism 160.
The cross dichroic prism 160 has a function as a color light combining unit that combines three colors of modulated light to form a color image. In the cross dichroic prism 160, a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a substantially X shape at the interface of four right-angle prisms. These dielectric multilayer films combine three colors of modulated light to form combined light for projecting a color image. The combined light generated by the cross dichroic prism 160 is emitted in the direction of the projection lens 170. Projection lens 170
Has a function of projecting the combined light on the projection screen, and displays a color image on the projection screen.

In addition, by incorporating a polarization conversion unit equipped with the polarization conversion element of the present invention having excellent heat resistance and light resistance as described later, a clear image can be projected for a long time using a light source with high brightness and high heat generation. It can be a liquid crystal projector.
Further, as in the present invention, the polarization conversion element of the present invention includes a retardation plate (laminated half-wave plate) that reliably functions as a half-wave plate in a wide wavelength band. A liquid crystal projector capable of projecting bright and clear images can be realized.

1 1/2 wavelength plate, 2, 4, 6 wavelength plate, 10 PBS array (element main body), 10A element main body, 10C joint surface, 10D light incident surface, 10E light exit surface, 10F edge, 11
Translucent substrate, 11A translucent plate material, 12 polarized light separation film, 13 reflective film, 14 adhesive layer,
14A adhesive, 16 light incident surface, 17 light emitting surface, 20 wavelength plate, 20A phase difference plate,
1B phase difference plate 1C base, 1C1 base, 1C2 base, 1D phase difference, 1D1 phase difference, 1D2 phase difference, 1E tip, 1E1 tip, 1E2 tip, 1F light incident surface, 21 bonding layer, 91 Polarization separation film, 92 reflection film, 93 adhesive layer, 95 element body, 96 bonding layer, 97 retardation plate, 98 translucent substrate, 110 light source, 111 lens array, 120 polarization conversion unit, 121 superposition lens, 130 color light separation Optical system, 1
31 Dichroic mirror, 132 Dichroic mirror, 133 Reflective mirror, 1
40 incident side lens, 141 relay lens, 142 reflecting mirror, 143 reflecting mirror, 144 field lens, 145 field lens, 146 field lens,
146 Reflective mirror, 150B liquid crystal light valve, 150G liquid crystal light valve, 15
0R liquid crystal light valve, 160 cross dichroic prism, 170 projection lens, 200 unit frame, 210 optical element, 210 light shielding plate, 220 lens array, 2
30 clips, 310 optical elements, 400 laminates, 410 laminate blocks, 410A
Cut surface, 500 polishing device, 600 test piece, 601 test, 601 test piece, 610
Fixed frame, 620 Yellowing, 951 Light incident surface, 952 Light exit surface, 961 Bubble, 981
Corner

Claims (8)

Consists of a material having birefringence and optical rotation,
A first wave plate having a phase difference Γ1, a second wave plate having a phase difference Γ2, and a third wave plate having a phase difference Γ3 are arranged so that their optical axes intersect each other with respect to light having a wavelength λ. ,
A wave plate that emits light by rotating the polarization plane of linearly polarized light of incident light by 90 (deg) with respect to light in the range of wavelengths λ1 to λ2 (λ1 <λ2),
The wavelength λ is
λ1 ≦ λ ≦ λ2
Satisfied,
The phase difference Γ1, the phase difference Γ2, and the phase difference Γ3 are:
Γ1 = 2π / λ × (ne-no) × t1
Γ2 = 2π / λ × (ne-no) × t2
Γ3 = 2π / λ × (ne-no) × t3
Γ1 = Γ2 = Γ3 = 180 (deg)
Where ne is the extraordinary refractive index, no is the ordinary refractive index, t1 is the thickness of the first wave plate in the normal direction of the main surface, t2 is the thickness of the second wave plate in the direction of the main surface normal, and t3 Satisfies the relationship of the thickness of the third wave plate in the normal direction of the principal surface,
In each wave plate, the angle β formed by the principal surface normal and the optical axis is A when the lower limit of the angle β is A,
A ≦ β <90 (deg) is satisfied,
The optical axis azimuth angle θ1 of the first wave plate, the optical axis azimuth angle θ2 of the second wave plate, and the optical axis azimuth angle θ3 of the third wave plate are a correction value of the optical axis azimuth angle θ1, and When the correction value of the optical axis azimuth angle θ3 is b,
θ1 = 22.5 (deg) + a
θ2 = 45.0 (deg)
θ3 = 67.5 (deg) −b
However, a = b ≠ 0 (deg)
Satisfied,
The lower limit A of the angle β is
13 (deg) ≦ A
A wave plate characterized by satisfying The wave plate according to claim 1,
The lower limit A of the angle β is
A = -7E-06a ⁵ + 0.0006a ⁴ + 0.0132a ³ + 0.1204a ² +0
. 4284a + 13.155
Satisfied,
The correction value a of the optical axis azimuth angle θ1 is
−15.0 (deg) ≦ a ≦ 8.0 (deg)
A wave plate characterized by satisfying The wave plate according to claim 1 or 2,
The wavelength λ1 is 400 nm,
The wavelength λ2 is 700 nm,
The wavelength λ is
λ = (λ1 + λ2) / 2 = 550 nm
A wave plate characterized by satisfying The wave plate according to claim 1 or 2,
The wavelength λ3 is 500 nm,
When the wavelength λ4 is 600 nm,
The relationship between the wavelength λ and the wavelengths λ3 and λ4 is as follows:
λ3 ≦ λ ≦ λ4
A wave plate characterized by satisfying A plurality of translucent substrates having a light entrance surface and a light exit surface that are substantially parallel to each other and bonded via an adhesive by a joint surface having a predetermined inclination angle with respect to the light incident surface or the light exit surface And separating the light incident on the light incident surface into two different types of linearly polarized light whose polarization directions are orthogonal to each other, and converting one of the linearly polarized light An optical element having a polarization separating unit that transmits and reflects the other linearly polarized light; and a reflecting unit that reflects the reflected light beam of the other linearly polarized light and changes the direction of the optical path; and the light emitting surface. , Disposed in an upper region of the polarization separation unit or an upper region of the reflection unit, and rotating one of the two types of linearly polarized light and rotating the polarization surface of the other linearly polarized light A wave plate that converts to parallel linearly polarized light and emits it; Wherein the wave plate is a wave plate according to any one of claims 1 to 4, wherein the adhesive layer is an ultraviolet-curing adhesive, thickness of 5μm or 10μm
A polarization conversion element characterized by the following. 6. The polarization conversion element according to claim 5, wherein the adhesive layer contains a modified acrylate or a modified methacrylate as a main component. A polarization conversion unit comprising the polarization conversion element according to claim 5 and a fixed frame for fixing the polarization conversion element. 8. A light source device that emits light, and converts light from the light source device into one type of polarized light.
A polarization conversion unit described in the above, a light modulation device that forms an optical image of polarized light from the polarization conversion unit according to image information, and projection optics that enlarges and projects the optical image formed by the light modulation device And a projection device.

Images