JP2003029032A - Polarizing separation and conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive polarizing separation and conversion element which can separate and convert polarized light with high accuracy. SOLUTION: The element satisfies the relation of t2/t1=4sin<2> x-1, wherein t1 is the distance (thickness of a transparent substrate 113a) between a polarizing separation film 111 and a reflecting film 112 in a polarizing separation part 110, t2 is the distance (thickness of a transparent substrate 113b) between the polarizing separation film 111 in the polarizing separation part 110 and the reflecting film 112 in the adjacent polarizing separation part or between the reflecting film 112 in the polarizing separation part 110 and the polarizing separation film 111 in the adjacent polarizing separation part, and x ( deg.) is the incident angle to the polarizing separation film (45 deg.<x<90 deg.). The element holds regions 110a and 110b where no film is formed on the transparent substrates so as to keep the optical path. The length w1 of the region where the film is formed in the polarizing separation part 110 and the length w2 of the region where the film is not formed are controlled to satisfy w2/w1=0.5-1/2tan<2> x.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization separation conversion element used for aligning natural light into a specific polarization state.

[0002]

2. Description of the Related Art P is a basic component of a liquid crystal projector.
S-polarized light separation conversion elements are widely used.

FIG. 26 is a diagram schematically showing the structure of a conventional PS polarization separation conversion element. As shown in FIG. 26, the PS polarization separation conversion element 1 includes a polarization separation section group 2 which has a substantially rectangular cross section and which has a light incident surface 2a and a light emission surface 2b parallel to the light incident surface 2a. A light-shielding mask 3 which is arranged at a predetermined position on the light incident surface 2a side of the polarization separation unit group 2 and blocks light from entering a predetermined region of the light incident surface 2a, and a light emission surface 2b of the polarization separation unit group 2. A phase plate arranged opposite to,
For example, it has a half-wave plate (hereinafter referred to as a λ / 2 plate) 4.

The polarization separation section group 2 is constituted by adhering a plurality of transparent substrates (glass substrates) 21 each having a cross section of a substantially parallelogram and a triangle. It has a cross-sectional structure in which the film 22 and the reflective film 23 are alternately sandwiched between the glass substrates 21. The polarization separation film 22 and the reflection film 23 form a polarization separation unit 20. Specifically, the thin film laminated polarization separation film 22 is formed on the glass substrate 21, a required number of the films are stacked and adhered, and cut obliquely at an angle of 45 °. Since the adhesive does not affect the optical characteristics, it will not be mentioned in the future.

The polarized light separating film 22 is formed of P as the first polarized light.
The polarized light is transmitted as it is, and the S-polarized light as the second polarized light functions as a reflection mirror. Therefore, the P-polarized component of the light that has entered the polarization separation film 22 via the light incident surface 2a is first separated, and the remaining S-polarized component is reflected twice to be emitted from the light emitting surface 2b. S by reflection
Since the P-polarized component should not be mixed in the region where the polarized light is emitted, the periodic light-shielding mask 3 is provided on the light incident surface 2a side. Then, P-polarized light and S-polarized light are provided on the light exit surface 2b side.
Since the polarized light comes out alternately, only one of them is made to pass through the phase plate (λ / 2 plate) 4 whose polarization direction is changed by 90 ° so that the polarized state is made uniform.

[0006]

The PS polarization separation conversion element described above is an excellent optical component, but has a big problem that the price is high. The step of attaching the λ / 2 plate 4 is not cheap, but more than that, in order to obtain a polarization separation film with sufficient performance at an incident angle of 45 °, 30 or more layers of precisely controlled thickness are laminated. The fact that it has to be done increases the manufacturing cost. Further, the difficulty of designing the polarization separation film is very high.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polarization separation conversion element which can be manufactured at a low price and which can separate and convert polarized light with high accuracy.

[0008]

In order to achieve the above object, the polarization splitting / converting element of the present invention transmits the first polarized light of the incident light incident at a predetermined angle with respect to the light incident surface, and transmits the second polarized light. A polarized light separation film that reflects the polarized light from the light incident surface in a direction different from the transmission direction, and a reflection surface is disposed so as to face the light incident surface of the polarized light separation film, and the polarized light is reflected by the polarized light separation film. A plurality of polarization splitting portions including a reflection film that reflects the second polarized light in a direction substantially parallel to the transmission direction of the first polarized light;
Of the polarized light and the second polarized light reflected by the reflection film, and the conversion means for emitting the polarized light in the same polarization direction, and the plurality of polarization splitting portions are arranged in a direction substantially orthogonal to the incident direction of the incident light. ,
The polarization separation films and the reflection films are arranged at predetermined intervals so as to be alternately arranged, and the incident angle of the incident light with respect to the light incident surface of each polarization separation film is larger than 45 degrees and smaller than 90 degrees. Is set to.

In the present invention, the distance between the polarization separation film and the reflection film in the polarization separation unit, and the reflection film of the polarization separation unit adjacent to the polarization separation film of the polarization separation unit or the reflection film of the polarization separation unit. The distance between the polarized light separating portion and the polarized light separating film is different.

Preferably, when the incident angle of the incident light on the polarization separation film of the polarization separation unit is x degrees (45 ° <x <90 °), the polarization separation film and the reflection film in the polarization separation unit are and the distance t _1, the distance t ₂ between the polarization separation film of the polarization separation unit adjacent to the reflective film or reflective film of the polarization separation section of the polarization separation section and an adjacent polarization separation film of the polarization separation section, t ₂ /
The relationship of t ₁ = 4sin ² x−1 is satisfied.

Further, according to the present invention, in the region where the polarization separation film and the reflection film in the polarization separation section face each other, on the light incident side, the reflection film should not block the incidence on the light incident surface of the polarization separation film. On the light emission side, there is a region where no film is formed so as not to block the emission of the second polarized light reflected by the reflection film by the polarization separation film.

Further, according to the present invention, the incident angle of the incident light on the polarization splitting film of the polarization splitting portion is x degrees (45 ° <x <90.
°), the length of the region where the film is formed is w ₁ and the length of the region where the film is not formed is w _{2 in the} polarization splitting section.
Then, the relationship of w ₂ / w ₁ = 0.5−½tan ² x is satisfied.

Further, in the present invention, the width of the opening through which the first polarized light passing through the polarization separating film of each of the above-mentioned polarization separating portions passes and the width of the opening through which the second polarized light reflected by the reflecting film passes through are the same. It is set to width.

Further, according to the present invention, the polarization of each of the above-mentioned polarization separation units is different.
Place the light separation film and the reflection film between the transparent substrates.
And the incident light is incident on the light incident surface of the polarization separation film.
The center value of the angle is set near 56 degrees,
The incident angle of the incident light on the polarization separation film of is x degree (45 ° <x
<90 °), the polarization component in the polarization separation section
The thickness t of the transparent substrate, which is the distance between the separation film and the reflection film₁ And this
Reflection of the polarized light separating part adjacent to the polarized light separating film of the polarized light separating part
Polarization separation part adjacent to the film or the reflection film of the polarization separation part
Thickness t of the transparent substrate, which is the distance from the polarization separation film of₂ Is t₂ 
/ T₁ = 1.75, and
The area where the polarization separation film and the reflection film face each other, and the light incident side
Does not block the incidence on the light incident surface of the polarization separation film with a reflective film.
Therefore, on the light output side, the polarization separation film prevents
Form a film so as not to block the output of the second polarized light
There is a non-existing area, and the film is
The length of the region forming₁ , The length of the area where the film is not formed
Sa w₂ Then, w₂ / W ₁ Satisfies the relationship of = 0.27
You

Further, the polarization splitting / converting element of the present invention is such that the first incident light incident on the light incident surface at a predetermined angle.
A polarized light separating film which transmits the polarized light of and the second polarized light is reflected from the light incident surface in a direction different from the transmission direction, and a reflecting surface is arranged so as to face the light incident surface of the polarized light separating film,
A reflection film that reflects the second polarized light reflected by the polarization separation film in a direction substantially parallel to the transmission direction of the first polarized light, a first polarization that has passed through the polarization separation film, and a reflection film by the reflection film. And a conversion means for emitting the polarized light of the second polarized light having the same polarization direction, and the incident angle of the incident light with respect to the light incident surface of the polarization separation film is larger than 45 degrees and smaller than 90 degrees. Is set to.

In the polarization separation conversion element of the present invention, at least the polarization separation film of the polarization separation film and the reflection film is an optically transparent high refractive index layer having a predetermined refractive index with respect to the incident light. H, and an optically transparent first low-refractive index layer L and a second low-refractive index layer L that are arranged so as to sandwich the high-refractive index layer H and have a lower refractive index than the high-refractive index layer. It includes a basic structure film LHL and has a repeating structure (LHL) ^m of the above basic structure.

Further, in the polarization separation conversion element of the present invention, the thickness of the high refractive index layer and the thicknesses of the first low refractive index layer and the second low refractive index layer are set to the reference wavelength of incident light. It is set based on.

Further, the polarization separation conversion element of the present invention is preferably
Suitably, the reference wavelength of the incident light is λ ₀ And when above
The thickness of the high refractive index layer, and the first low refractive index layer and the second
The thickness of the low-refractive index layer of the reference wavelength is divided by a predetermined integer
It is set to the optical thickness corresponding to the value.

Further, in the polarization separation conversion element of the present invention, the number of repetitions m of the basic structure is an integer of 3 or more.
Preferably, the number of repetitions m of the basic structure is 3 or more and 7
The following integers.

Further, in the polarization separation conversion element of the present invention, the center value of the incident angle of the incident light on the optical film surface is set in the vicinity of 56 degrees.

Further, in the polarization separation conversion element of the present invention, the high refractive index layer has a wavelength dispersion characteristic of an optical constant n in a predetermined range including a reference wavelength of incident light and has a predetermined wavelength shorter than the reference wavelength. In the above, the first and second low-refractive index layers include a material having a characteristic that the extinction coefficient gradually approaches zero, and the first and second low refractive index layers have a wavelength dispersion characteristic of an optical constant n in a predetermined range including the reference wavelength of incident light. And a material having an extinction coefficient of substantially zero over substantially the entire wavelength range is included.

Further, in the polarization separation conversion element of the present invention, the polarization separation film and the reflection film of the polarization separation section are arranged so as to be sandwiched by the transparent substrates, and the refractive index of the high refractive index layer is:
The refractive index of the transparent substrate is set higher than that of the first and second low refractive index layers, and the refractive index of the first and second low refractive index layers is set lower than that of the transparent substrate.

Further, in the polarization separation conversion element of the present invention, the basic structure films adjacent to each other are formed so as to share the first low refractive index layer L and the second low refractive index layer L.

According to the present invention, for example, the distance (for example, the thickness of the transparent substrate) t ₁ between the polarization separation film and the reflection film in the polarization separation unit and the polarization separation unit adjacent to the polarization separation film of the polarization separation unit. The distance (for example, the thickness of the transparent substrate) t ₂ between the reflection film or the polarization film of the polarization separation unit and the polarization separation film of the adjacent polarization separation unit makes the incident angle to the polarization separation film x degrees (45 ° <x. <90 °), t ₂ / t ₁ = 4si
It is configured to satisfy the relationship of n ² x−1. Further, in order to secure the optical path, for example, a region where no film is formed is secured on the transparent substrate. Then, in the polarized light separating portion, if the length of the region where the film is formed is w ₁ and the length of the region where the film is not formed is w ₂ , the relationship of w ₂ / w ₁ = 0.5−½tan ² x Configured to meet. The polarization separation conversion element manufactured based on this design guide can deal with a specific incident angle of more than 45 ° and less than 90 °.

Further, according to the present invention, the polarization separation element is
An optically transparent high refractive index that has a specified refractive index
The high refractive index layer H and the high refractive index layer H sandwiching the high refractive index layer H are sandwiched between the high refractive index layer H and the high refractive index layer H.
Optically transparent first low refractive index having a refractive index lower than that of the refractive index layer H.
Basic structure film including a refractive index layer L and a second low refractive index layer L
Including LHL, a repeating structure of this basic structure (LHL)
^m (However, m is an integer of 2 or more, preferably 3 to 7)
To be configured. And, for example, a polarization separation element
Polarization separation element, which is in contact with the light incident surface and the light transmitting surface of
A transparent substrate made of, for example, glass is formed so that
Be done. The high refractive index layer H and the low refractive index layer L are
Reference wavelength λ₀ For example λ ₀ / 4 optical thickness
Composed. For example, as a low refractive index material for the polarization separation element
SiO₂ (N = 1.46) as a high refractive index material
iO₂ Using (n = 2.44) respectively, L is 94.2.
nm · H is 56.4 nm, and per repeat
Has a film thickness of about 250 nm. Common as a transparent substrate
Optical glass (BK7) can be used.
Is the maximum polarization separation for incident light at angles near 56 degrees
Show performance. For these combinations, the basics described above
There is no need to add any correction to the structure, it is extremely simple
High performance can be obtained with the configuration. Also, the number of repetitions of the film m
4 is sufficient for practical use, and the number of layers at this time is only 9 layers.
Therefore, the film thickness is only 1 μm.

According to the present invention, the incident light having the predetermined reference wavelength λ ₀ is incident on the transparent substrate. Then, the incident light including the first polarized light (P polarized light) and the second polarized light (S polarized light) is propagated through, for example, the transparent substrate to reach the light incident surface of the polarization separation film, and is incident at a predetermined angle with respect to the light incident surface. , Is incident on the polarization separation element at an angle of 56 degrees, for example. The light incident on the polarization splitting film is propagated through, for example, the first basic structure film, the second basic structure film, and the third basic structure film, while the second polarized light is propagated through the second basic structure film, for example. Is reflected at a predetermined angle with respect to the propagation direction (transmission direction) at the low-refractive index layer L that is the boundary between the third basic structure film and the third basic structure film, and reaches the reflection film. The first polarized light goes straight forward, passes through the third basic structure film or the further basic structure film, and is emitted from the light transmitting surface. On the other hand, the second polarized light that has reached the reflective film is reflected by the reflective film and is emitted in a direction substantially parallel to the transmission direction of the first polarized light of the polarization separation film. Then, the conversion means converts the second polarized light into the first polarized light or the first polarized light into the second polarized light.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in detail below with reference to the drawings.

First Embodiment FIG. 1 is a configuration diagram schematically showing a first embodiment of a PS polarization separation conversion device according to the present invention. Further, FIG. 2 is a diagram schematically showing an optical path of the PS polarization separation conversion device according to the first embodiment. In the present embodiment, an example of design completion based on the actually measured optical constants of the optical material is shown.
If the optical constants change, the optimum design result may deviate, but it goes without saying that the present invention is not limited to this example and can be arbitrarily changed without departing from the gist of the present invention.

As shown in FIGS. 1 and 2, the present PS polarization separation conversion device 10 has a substantially rectangular cross section, and has a light incident surface 11a and a light emitting surface 11 parallel to the light incident surface 11a.
b, and the light incident surface 11a disposed at a predetermined position on the light incident surface 11a side of the polarization separator portion 11.
Light-blocking mask 12 for blocking the incidence of light on a predetermined area of a
And a phase plate, for example, a λ / 2 plate (half-wave plate) 1 arranged to face the light exit surface 11b of the polarization splitting unit group 11.
Have three. In FIG. 1 and FIG. 2, the shading mask 12 and the λ / 2 plate 13 are shown in FIG.
Although it is drawn at a position apart from the light incident surface 11a and the light emitting surface 11b, the both may be directly bonded onto the element.

The polarization separation section group 11 transmits the P-polarized light as the first polarized light of the incident light IO which is incident on the light incident surface 111a at a predetermined angle, and transmits the S-polarized light as the second polarized light.
A polarization separation film 111 that reflects polarized light from the light incident surface 111a in a direction different from the transmission direction and a reflection surface 112a are arranged in parallel so as to face the light incident surface 111a of the polarization separation film 111. A plurality of polarization splitting sections 110 including a reflection film 112 that reflects the reflected S-polarized light toward the light exit surface 11b that is a direction substantially parallel to the transmission direction of the P-polarized light. The plurality of polarization separation units 110 are
In the direction (vertical direction in FIG. 1) orthogonal to the incident direction of incident light IO (from left to right in FIG. 1), the polarization separation film 111 is formed.
And the reflection films 112 are arranged at predetermined intervals so as to be alternately arranged. Then, the incident light I of each polarization separation unit 110
The incident angle of O with respect to the light incident surface 111a of each polarization separation film 111 is set to a specific angle larger than 45 degrees and smaller than 90 degrees, for example, 56 degrees.

Specifically, the polarized light separating section group 2 is constituted by adhering a plurality of transparent substrates (glass substrates) 113 each having a cross section of substantially parallelogram and triangle, and the incident angle x of the light ray is 45. The polarization separation film 111 and the reflection film 11 are set to have a specific angle larger than 90 degrees and smaller than 90 degrees.
2 has a cross-sectional structure in which two transparent substrates are alternately sandwiched.
More specifically, the polarization separation films 111 that are alternately arranged on the thin transparent substrate 113a and the thick transparent substrate 113b.
And a structure sandwiching the reflection film 112. Optical glass (BK7) is generally used for the transparent substrates 113, 113a, 113b.

FIG. 3 is a diagram showing various structural parameters of the PS polarization separation conversion device 10 according to the first embodiment.

Further, the polarization splitting unit group 11 includes the polarization splitting unit 1.
When the incident angle of the incident light on the polarization splitting film 111 of No. 10 is x degrees (45 ° <x <90 °), the polarization splitting unit 110
The thickness t ₁ of the thin transparent substrate 113a, which is the distance between the polarization separation film 111 and the reflection film 112, and the reflection film 112 of the polarization separation unit adjacent to the polarization separation film 111 of the polarization separation unit 110 or the polarization separation film. The thickness t ₂ of the thick transparent substrate 113b, which is the distance between the reflection film 112 of 110 and the polarization separation film 111 of the adjacent polarization separation unit, is configured to satisfy the following expression.

[0034]

[Number 1] ^{_{t 2 / t 1 = 4sin 2}} x-1 ... (1)

Further, the polarization separation section 110 includes the polarization separation film 1
11 and the reflection film 112, which are opposite to each other, on the light incident side, the reflection film 112 forms the light incident surface 11 of the polarization separation film 111.
It is formed so that there is a region 110a in which the reflection film 112 is not formed so as not to block the incident on 1a.
The polarization separation unit 110 is a region where the polarization separation film 111 and the reflection film 112 face each other, and on the light emission side, so as not to block the emission of the P-polarized light reflected by the reflection film 112 by the polarization separation film 111, It is formed so that there is a region 110b where the polarization separation film 111 is not formed.

Further, the polarization separation film 11 of the polarization separation unit 110
The incident angle of the incident light on 1 is x degree (45 ° <x <90 °)
Then, in the polarization separation section 110, the polarization separation film 1
11 When the length of the region where the film is formed is w ₁ and the length of the region where the film is not formed is w ₂ , the following formula is satisfied.

[0037]

[Number 2] _{w 2 / w 1 = 0.5-1 /} 2tan 2 x ... (2)

Further, the polarization splitting film 11 of the polarization splitting unit 110.
1 and the width of the opening through which the P-polarized light that passes through
The widths of the apertures through which S-polarized light reflected by all pass are the same width y
Is set to.

The polarization separation conversion element 1 having the above-mentioned structure
At 0, as shown in FIG. 2, the incident light IO is incident mainly from the end face of the thin transparent substrate 113a. The reflection film 112 is not formed on some of the lights. Although only the adhesive passes through the bonding surface of the transparent substrate, the optical constant of the adhesive is aligned with that of the substrate so that reflection at this interface
It is possible to suppress refraction. The regions 110a and 110b where the film is not formed are formed on the transparent substrate by PBS.
It can be ensured by applying a mask when forming the film, or removing the film by etching after forming the film.

Next, various structural parameters of the polarization splitting section 110 will be considered with reference to FIG.

As described above, the description is made using the elementary trigonometric function, where the incident angle is x degrees and the width of the opening through which light passes is y. The unit of angle is unified in degrees. Since the incident angle is x, a ₁ = 90 ° −x in FIG.
₂ = 2 × −90 °, which is uniquely determined. By defining the opening width as y, the sum of the film thicknesses of the two types of transparent substrates 113a and 113b is expressed by the following equation.

[0042]

[Mathematical formula-see original document] t ₁ + t ₂ = 2ysin x (3)

Further, the thickness t of the thinner transparent substrate 113a
₁ becomes as follows.

[0044]

(4) t ₁ = sin a ₁ × y / cos (a ₂ ) = y / 2sin x (4)

The thickness t ₂ of the thicker transparent substrate 113b is as follows.

[0046]

T ₂ = 2ysin xy− ₂ / 2sin x (5)

The thinner the ratio of thickness t ₂ of the thickness t ₁ and the thicker the transparent substrate 113b of the transparent substrate 113a of is expressed by the following equation.

[0048]

T ₂ / t ₁ = (2ysin x−y / 2sin x) × 2sin x / y = 4sin ² x−1 (6)

In the polarization splitting section 110, the length w _{1 of the} region where the film is formed and the length w _{2 of the} region where the film is not formed are as follows.

[0050]

## EQU00007 ## w ₁ = y / cos x (7)

[0051]

W ₂ = ytan a ₂ / sin x = −y / (tan 2x × sin x) (8)

The ratio of the length w _{1 of the} region where the film is formed to the length w ₂ of the region where the film is not formed is expressed by the following equation.

[0053]

[Equation 9] _{w 2 / w 1 = -1 /} (tan 2x × tan x) = 0.5-1 / 2tan 2 x ... (9)

By the way, the thickness of the polarization separation section group 11 is given by the following equation.

[0055]

[Mathematical formula-see original document] w ₃ + w ₄ = y (tan x + tan a ₂ ) (10)

For example, when 56 degrees is selected as the incident angle, a glass substrate having a substrate thickness ratio of t ₂ / t ₁ = 1.75 is prepared and w ₂ / w ₁ = 0.27. The polarization separation film may be formed so as to satisfy the relationship.

The PS polarization splitting / converting element 10 according to the above design guidelines can deal with a specific incident angle of more than 45 ° and less than 90 °. As a result, the degree of freedom in designing the polarization separation film is dramatically increased, and a high-performance polarization separation film can be used with a small number of layers. This will lead to the production of PS polarization separation conversion elements at a much lower cost than at present.

Hereinafter, an example of the structure of the polarization separation film 111 which constitutes the polarization separation section 110 applicable to the PS polarization separation conversion element 10 having such characteristics will be specifically described. Although the polarization separation film and the reflection film have been described in the present embodiment, the reflection film may be any one as long as it can reflect S-polarized light. Therefore, the polarization separation film described below is adopted as the reflection film 112. It is possible.

FIG. 4 is a diagram for explaining the structure of the polarization separation film according to the present invention.

As shown in FIG. 4, the present polarization separation film 111 is sandwiched between transparent substrates 113a and 113b having different thicknesses so as to be in contact with the light incident surface 111a and the light transmission surface 111b of the polarization separation film 111. Is formed.

The polarization separation film 111 is an optically transparent high refractive index layer H having a predetermined refractive index with respect to the incident light OI,
A basic structure film LHL composed of an optically transparent first low-refractive index layer L and a second low-refractive index layer L having a lower refractive index than the high-refractive index layers H arranged so as to sandwich the high-refractive index layer H. Including,
It has a repeating structure (LHL) ^m of this basic structure. Number of repetitions of lamination of the basic structure LHL of the polarization separation film 111 m
Is preferably an integer of 3 or more, as will be described later, and FIG. 4 shows the case where m = 3.

FIG. 5 is a diagram showing a stacking repeating structure of the polarization separation element when the stacking repeating number m is 3.

The polarization separation film 111, as shown in FIG.
For example, from the light incident surface 111a side to the first low refractive index layer L
It has a structure in which the basic structure consisting of 1, the high refractive index layer H, and the second low refractive index layer L2 is simply repeated three times to be laminated. That is, the first basic structure film LHL1, the second basic structure film LHL2, and the third basic structure film LHL3 are sequentially stacked from the light incident surface 111a side, and it is necessary to add some correction to the basic structure. It has a very simple structure. Since three basic structure films each having three layers are laminated, a simple consideration should be nine layers. However, in practice, as shown in FIG. 5, the second low refractive index layer L2 of the first basic structure film LHL1 and the first low refractive index film L1 of the second basic structure film LHL2 are shared. Can be formed as the same layer. Similarly, the second low refractive index layer L2 of the second basic structure film LHL2 and the first low refractive index film L1 of the third basic structure film LHL3 can be formed as the same layer so as to be shared. Therefore, the actual number of layers is 7 instead of 9.

FIG. 6 is a diagram showing a stacking repeating structure of the polarization separation element when the stacking repeating number m is 4.

In this case as well, the basic structure film consisting of three layers is divided into four layers.
Since two layers are stacked, a simple consideration should be 12 layers. However, in practice, as shown in FIG.
The second low refractive index layer L2 of the basic structural film LHL1 and the first low refractive index film L1 of the second basic structural film LHL2 can be formed as the same layer so as to be shared. Similarly, the second low refractive index layer L2 of the second basic structure film LHL2 and the first low refractive index film L1 of the third basic structure film LHL3 can be formed as the same layer so as to be shared, and Basic structure film LHL
Third low refractive index layer L2 and fourth basic structure film LHL4
The first low refractive index film L1 can be formed as the same layer so as to be shared. Therefore, the actual number of layers is 9 instead of 12.

The number M of stacked layers of the polarization separation film 111 is given by the following equation.

[0067]

[Equation 11] M = 3 × m− (m−1) (11)

That is, the polarization separation film 111 according to the present invention.
The number M of stacked layers is 2 layers less than the number considered when simply stacking the basic structure film LHL consisting of three layers. Therefore, the structure of the polarization splitting film 111 according to the present invention can contribute to simplification of the manufacturing process and thinning.

The high refractive index layer H of the polarization separation film 111 has a wavelength dispersion characteristic of an optical constant (refractive index) n in a predetermined range including the reference wavelength λ ₀ of the incident light IO, for example, 550 nm, and the reference wavelength λ. _It is made of a material having a characteristic that the extinction coefficient k gradually approaches zero at a predetermined wavelength shorter than ₀ .

The high refractive index layer H contains TiO ₂ (n = 2.3).
5 to 2.8), ITO (n = 1.95 to 2.1), Zn
O (n = 1.9), CeO ₂ (n = 1.95), SnO
₂ (n = 1.95), Al ₂ O ₃ (n = 1.63), L
a ₂ O ₃ (n = 1.95), ZrO ₂ (n = 2.0
5), Y ₂ O ₃ (n = 1.87) and the like are used.

In this embodiment, an example in which TiO ₂ having the highest refractive index is adopted as the high refractive index layer H is shown.

FIG. 7 shows the optical constant (refractive index) n of TiO ₂ .
It is a figure which shows the chromatic dispersion dependence of. In FIG. 7, the horizontal axis represents wavelength and the vertical axis represents optical constant (refractive index) n. As shown in FIG. 7, TiO ₂ used as the high refractive index layer H has a reference wavelength λ ₀ = 550n of incident light IO.
A predetermined range including m, specifically, approximately 380 nm to 770
In the range of nm, it has wavelength dispersion characteristics of n = 2.8 to 2.35.

FIG. 8 shows the optical constant (extinction coefficient) of TiO ₂ .
It is a figure which shows the chromatic dispersion dependence of k. In FIG. 8, the horizontal axis represents wavelength and the vertical axis represents optical constant (extinction coefficient) k. As shown in FIG. 8, in TiO ₂ used as the high refractive index layer H, the extinction coefficient k rapidly approaches zero near 380 nm, which is shorter than the reference wavelength λ ₀ = 550 nm of the incident light IO, and the wavelength is 500 nm. It has the property of becoming zero in the vicinity and above.

The first and second low refractive index layers L (L1, L2) of the polarization separation film 111 have wavelength dispersion of an optical constant (refractive index) n in a predetermined range including the reference wavelength of the incident light IO, for example, 550 nm. It is made of a material having characteristics and having an extinction coefficient of substantially zero in substantially the entire wavelength range k.

The low refractive index layer 2 is made of SiO.₂ (N = 1.4
54-1.473) and MgF₂ (N = 1.38), Li
F (n = 1.4), AlF₃ (N = 1.4), Na₃ A
IF ₆ (N = 1.33) or the like is used.

In this embodiment, as the low refractive index layer L, S
An example in which iO ₂ is adopted is shown.

FIG. 9 shows the optical constant (refractive index) n of SiO ₂ .
It is a figure which shows the chromatic dispersion dependence of. In FIG. 9, the horizontal axis represents wavelength and the vertical axis represents optical constant (refractive index) n. As shown in FIG. 9, SiO ₂ used as the low refractive index layer L has a reference wavelength λ ₀ = 550n of the incident light IO.
A predetermined range including m, specifically, approximately 380 nm to 770
It has a wavelength dispersion characteristic of n = 1.473 to 1.454 in the range of nm.

[0078] In addition, the extinction coefficient k of SiO ₂ is a zero in the entire wavelength range, there is no absorption by the SiO ₂ film.

The thickness h of the high-refractive index layer H and the thickness l of the first low-refractive index layer L and the second low-refractive index layer L of the polarization separation film 111 are determined by the reference wavelength of incident light, for example, 550 nm.
It is set based on. Specifically, when the reference wavelength λ _{0 of} incident light is 550 nm, the thickness h of the high refractive index layer H and the thickness l of the first low refractive index layer L and the second low refractive index layer L are set. Is a value obtained by dividing the reference wavelength λ ₀ by a predetermined integer,
It is set to an optical thickness for example corresponding to lambda _0/4

[0080] Thus, the high refractive index layer thickness of H of the polarization separation film 111, and the thickness of the first low refractive index layer L and the second low refractive index layer L is, lambda _0/4 equivalent Optical thickness. As a high-refractive index material, TiO ₂ (n = at reference wavelength λ ₀
2.44) and SiO ₂ (n = 1.46 at the reference wavelength λ ₀ ) as the low refractive index material, h is 56.
4 nm and l are 94.2 nm, and the film thickness per one repetition is about 250 nm. For example, when the number of repetitions m of the film is set to 4, the number of layers M is increased as described above.
Is only 9 layers and the film thickness is only 1 μm. And
In this embodiment, the polarization separation film 111 for the incident light IO is used.
The center value of the incident angle θ on the light incident surface 111a is set to near 56 degrees.

As the transparent substrates 113a and 113b, for example, glass (BK having an optical constant (refractive index) n of 1.52) is used.
7) is used.

As described above, in this embodiment, since the glass having the optical constant (refractive index) n of 1.52 is used as the transparent substrates 113a and 113b, the refractive index n3 of the transparent substrate and the polarized light separation are obtained. The refractive index n (H) of the high refractive index layer H and the refractive index n (L) of the low refractive index layer L of the film 111
The relationship with is as follows.

[0083]

[Equation 12]           n (L) <n3 <n (H) (12)

That is, in this embodiment, the refractive index n (H) of the high refractive index layer H of the polarization separation film 111 is set higher than the refractive index n3 of the transparent substrate 3, and the first and second low refractive indexes are set. Refractive index n (L) of the refractive index layer L Refractive index n3 of the transparent substrate 3
It is set lower.

In the PS polarization splitting / converting element 10 having the above-described configuration, for example, the incident light IO having the reference wavelength λ ₀ of 550 nm is incident from the left side surface of the transparent substrate 113a in FIG. Then, P as the first polarized light
Incident light including polarized light and S-polarized light as the second polarized light is propagated through the transparent substrate 113a and reaches the light incident surface 111a of the polarization separation film 111, and is at a predetermined angle with respect to the light incident surface 111a, preferably 56 degrees. Is incident on the polarization separation film 111. The light that has entered the polarization separation film 111 propagates through the first basic structure film LHL1, the second basic structure film LHL2, and the third basic structure film LHL3, while the S-polarized light has, for example, the second basic structure film. The film LHL2 and the third basic structure film LHL
Propagation direction (transmission direction) in the low-refractive index layer L which is the boundary with
Is reflected at a predetermined angle with respect to, propagates through the transparent substrate 3a, and reaches the reflection film 112. The P-polarized light goes further straight, passes through the third basic structure film LHL3, and passes through the light transmitting surface 1
It is emitted from 11b, propagated through the transparent substrate 3, and emitted from the right side surface (light emission surface) 11b in FIG. On the other hand, the S-polarized light that has reached the reflection film 112 is reflected by the reflection film 112, is emitted in a direction substantially parallel to the transmission direction of the P-polarized light of the polarization separation film 111, and is incident on the λ / 2 plate 13. And
The λ / 2 plate 13 converts the S-polarized light into P-polarized light, and the P-polarized light separating / converting element 10 outputs the P-polarized light with its polarization direction aligned.

In this way, the P-polarized light and the S-polarized light are separated by the polarization separation film 111, but in the present embodiment,
The center value of the incident angle of the incident light IO on the light incident surface 111a of the polarization separation film 111 is set to around 56 degrees. The number m of repetitions of the basic structure film LHL in the polarization splitting film 111 and the incident angle of the incident light IO on the polarization splitting film 111 will be described below in association with the drawings.

First, the number of repetitions m of the basic structure film LHL in the polarization separation film 111 will be considered.

FIG. 10 is a diagram showing the wavelength dependence of the P-polarized light transmittance when the number of repetitions m is 3 to 7.
FIG. 3 is a diagram showing wavelength dependence of P-polarized light transmittance when the number of repetitions m is 1 and 2. FIG. 12 is a diagram showing the wavelength dependence of the P polarized light reflectance when the number of repetitions m is 3 to 7, and FIG. 13 is P when the number of repetitions m is 1 and 2.
It is a figure which shows the wavelength dependence of polarized light reflectance.

10 and 11, the horizontal axis represents wavelength and the vertical axis represents transmittance. In addition, FIG.
In FIG. 13 and FIG. 13, the horizontal axis represents wavelength and the vertical axis represents reflectance. In FIG. 10 and FIG. 12, solid lines respectively indicate the transmittance characteristics and reflectance characteristics when the number of repetitions m = 3, and broken lines indicate the transmittance characteristics and the reflectance characteristics when the number of repetitions m = 4. In the figure, the broken line indicated by indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 5, and the broken line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 6. Shows the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 7. In addition, FIG.
In FIG. 13 and FIG. 13, the solid line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 1, and the broken line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 2. There is.

As can be seen from FIGS. 11 to 13, in the polarization splitting film 111 according to the present embodiment, the reflection of P-polarized light as the first polarized light is very small, and the wavelength of 400 nm.
In the above, most of the light is transmitted through the polarization separation element film. From FIGS. 10 and 11, it can be seen that as the number of repetitions m increases, the wavelength at which the polarization separation element film starts to be transmitted shifts to the long wavelength side.

FIG. 14 is a diagram showing the wavelength dependence of the S-polarized light transmittance when the number of repetitions m is 3 to 7.
FIG. 4 is a diagram showing wavelength dependency of S-polarized light transmittance when the number of repetitions m is 1 and 2. 16 is a diagram showing the wavelength dependence of the S-polarized reflectance when the number of repetitions m is 3 to 7, and FIG. 17 shows the wavelength dependency of the S-polarized reflectance when the number of repetitions m is 1 and 2. It is a figure.

14 and 15, the horizontal axis represents wavelength and the vertical axis represents transmittance. In addition, FIG.
In FIG. 17 and FIG. 17, the horizontal axis represents wavelength and the vertical axis represents reflectance. In FIGS. 14 and 16, the solid line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 3, and the broken line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 4. In the figure, the broken line indicated by indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 5, and the broken line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 6. Shows the transmittance characteristic and the reflectance characteristic when the number of repetitions m = 7. In addition, FIG.
In FIG. 17 and FIG. 17, the solid line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions is m = 1, and the broken line indicates the transmittance characteristic and the reflectance characteristic when the number of repetitions is m = 2. There is.

As can be seen from FIG. 17, the number of repetitions m
When the value is 1, the reflectance of S-polarized light is lower than 70% at maximum, which is not practical. On the other hand, as can be seen from FIGS. 14 to 17, when the number of repetitions m is 2 or more, most of the light is reflected in the wavelength range of 400 nm to 720 nm,
It is clear that it cannot penetrate. When the number of repetitions m is increased, the upper edge of the opaque region becomes steep.

Considering the characteristics shown in FIGS. 10 to 17, the polarization separation film 111 according to the present embodiment is 400 nm thick.
P-polarized light and S-polarized light can be separated with high accuracy in the above range of 150 nm to 300 nm. Here, as the characteristics of the polarization beam splitter, the transmittance of P-polarized light is 83% or more, and S
Assuming that the transmittance of polarized light is 5% or less, the number m of stacking repetitions is considered from the characteristics of FIGS.
It is preferably an integer of 3 or more and 7 or less. in this case,
It is possible to realize a polarization beam splitter capable of supporting an extremely wide wavelength range of 400 nm to 700 nm.

FIG. 18 shows the wavelength widths that can be separated by polarization when the width of a continuous wavelength range satisfying the conditions of the transmittance of P-polarized light of 83% or more and the transmittance of S-polarized light of 5% or less is used as the evaluation function. It is a figure which shows the repetition frequency dependence of. In FIG. 18, the horizontal axis represents the number of repetitions m, and the vertical axis represents the polarization separable wavelength width.

As can be seen from FIG. 18, in order to realize a polarization beam splitter capable of supporting a certain wavelength width, the number of repetitions m of the basic structure of the polarization separation film 111 should be 2 or more, which is 400 nm to 700 nm. In order to realize a polarization beam splitter capable of supporting a wide wavelength range, the number of repetitions m is preferably 3 or more (up to 10 in the data of FIG. 18), and preferably 3 or more as described above. It is preferably an integer of 7 or less.

Further, as can be seen from FIG. 18, there is a peak around m = 5, and there is a tendency that the peak decreases slightly thereafter. Therefore, practically, the number of repetitions m of 4 or 5 is sufficient.

FIG. 19 is a diagram showing the wavelength dependence of the transmittance of P-polarized light and S-polarized light when the number of times m of stacking is repeated is 4. In FIG. 19, the horizontal axis represents wavelength and the vertical axis represents transmittance. Further, in FIG. 19, the broken line is P
The transmittance characteristic of polarized light is shown, and the solid line shows the transmittance characteristic of S polarized light.

As shown in FIG. 19, the number of stacking repetitions m
When 4 is set as the characteristic of the polarization beam splitter,
Assuming that the transmittance of P-polarized light is 83% or more and the transmittance of S-polarized light is 5% or less, an extremely wide wavelength range of 400 nm to 700 nm can be supported, and a very practical polarization beam splitter can be realized.

Next, the incident angle of the incident light IO on the polarization separation film 111 will be considered. In the present embodiment, as described above, the light incident surface 11 of the polarization separation film 111 for the incident light IO.
The center value of the incident angle θ to 1a is set near 56 degrees.

Needless to say, in practice, it is desirable that the polarized light can be separated even for a light beam that is slightly deviated from the vicinity of the optimum incident angle of 56 degrees.

FIG. 20 is a diagram showing the incident angle dependence of the polarization separable wavelength width. In FIG. 20, the horizontal axis represents the deviation from the central angle, and the vertical axis represents the polarization separable wavelength width. As can be seen from FIG. 20, it is possible to realize polarized light separation in a wavelength range of 150 nm to 300 nm, which is a light beam that is incident at an angle that is deviated from the center value of the incident angle by approximately ± 5 degrees.

When the deviation is ± 3 degrees from the optimum condition, and ±
21 to 24 show the simulation results of the wavelength dependence of the transmittances of P-polarized light and S-polarized light when they are deviated by 5 degrees.

FIG. 21 shows the wavelength dependence of the transmittance of P-polarized light and S-polarized light when the incident angle of the incident light IO on the polarization beam splitter with the number of repetitions m of 4 deviates by +3 degrees from the optimum condition of 56 degrees. FIG. 22 is a diagram showing the wavelengths of the transmittances of P-polarized light and S-polarized light when the incident angle of the incident light IO on the polarization beam splitting element having the number of repetitions m of 4 deviates from the optimum condition of 56 degrees by −3 degrees FIG. 23 is a diagram showing the dependence, and FIG. 23 is a transmittance of P-polarized light and S-polarized light when the incident angle of the incident light IO to the polarization beam splitting element with the number of repetitions m of 4 deviates by +5 degrees from the optimum condition of 56 degrees 24 is a diagram showing the wavelength dependence of P polarization and S polarization in the case where the incident angle of the incident light IO on the polarization separation element having the number of repetitions m of 4 deviates by −5 degrees from the optimum condition of 56 degrees. It is a figure which shows the wavelength dependence of the transmittance of a.

21 to 24, the horizontal axis represents wavelength,
The vertical axis represents the transmittance. Further, in FIGS. 21 to 24, the broken line shows the transmittance characteristic of P-polarized light, and the solid line shows the transmittance characteristic of S-polarized light.

As can be seen from FIGS. 21 and 22, when the incident angles are 59 ° and 56 ° which are deviated from the optimum condition by ± 3 °, the waveform is slightly disturbed as compared with FIG. 19 showing the characteristic under the optimum condition. However, the condition that the transmittance of P-polarized light is 83% or more and the transmittance of S-polarized light is 5% or less is satisfied over a wide wavelength range.

As can be seen from FIGS. 23 and 24, the incident angles 61 ° and 5 ° deviated from the optimum condition by ± 5 °.
In the case of 1 degree, compared to FIG. 19 showing the characteristic under the optimum condition,
Furthermore, the waveform is disturbed, but it becomes narrower than when it is deviated by ± 3 degrees, but the transmittance of P-polarized light is still 8 over a wide wavelength range.
The conditions of 3% or more and S-polarized light transmittance of 5% or less are satisfied.

As described above, according to the first embodiment, the distance (for example, the thickness of the transparent substrate 113a) t ₁ between the polarization separation film 111 and the reflection film 112 in the polarization separation unit 110, and the polarization separation. The polarization separation film 111 of the part 110 and the reflection film 112 of the polarization separation part adjacent to the polarization separation film 111 or the polarization separation part 11
Polarization separation film 1 of the polarization separation unit adjacent to the 0 reflection film 112
Distance from 11 (for example, thickness of transparent substrate 113b) t ₂
However, the incident angle to the polarization separation film is x degrees (45 ° <x <90
°), the relationship of t ₂ / t ₁ = 4sin ² x−1 is satisfied, and in order to secure the optical path, for example, the regions 110a and 110b where no film is formed are secured on the transparent substrate, and the polarization separation unit 110 is further secured. Where, the length of the region forming the film is w
₁ and w ₂ is the length of the region where the film is not formed, w ₂ /
Since it is configured to satisfy w ₁ = 0.5−½tan ² x, it is possible to cope with a specific incident angle of more than 45 ° and less than 90 °. As a result, the degree of freedom in designing the polarization separation film is dramatically increased, and a high-performance polarization separation film can be used with a small number of layers. There is an advantage that it leads to the production of the PS polarization separation conversion element at a much lower cost than the current state.

Further, according to the first embodiment, the polarization separation film 111 includes the optically transparent high refractive index layer H having a predetermined refractive index with respect to the incident light OI and the high refractive index layer H. Optically transparent first low-refractive index layer L and second low-refractive index layer L having a lower refractive index than the high-refractive index layer H arranged so as to sandwich
Since it has a basic structure film LHL consisting of, and has a repeating structure (LHL) ^m (where m is an integer of 2 or more, preferably 3 to 7) of this basic structure, the film structure is extremely simple and It has the advantage of being able to be manufactured at low cost, since the number of layers required is small. If this configuration is used, the cost of the entire optical element incorporating the polarization separation conversion element can be reduced.

Further, this polarization separation element has excellent polarization separation characteristics at an incident angle of 56 degrees. In addition, the polarization separation film 11
SiO ₂ (n = 1.46) as a low refractive index material of 1,
When TiO ₂ (n = 2.44) is used as the high refractive index material, L is 94.2 nm and H is 56.4 nm,
The film thickness per one repetition is about 250 nm. A common optical glass (BK7) can be used as the transparent substrate, and this element exhibits the maximum polarization separation performance for incident light at an angle near 56 degrees. In the case of these combinations, it is not necessary to make any correction to the basic structure described above, and high performance can be obtained with an extremely simple configuration. Further, the number of repetitions m of the film is practically sufficient to be 4, and the number of laminated layers at this time is only 9 layers and the film thickness is only 1 μm. The polarization separation conversion element according to the present invention configured as described above has high productivity and can be provided to the market at low cost by mass production.

Second Embodiment FIG. 25 is a schematic diagram showing a second embodiment of a PS polarization separation conversion device according to the present invention.

The difference of the second embodiment from the above-mentioned first embodiment is that, as shown in FIG.
In A, the polarization separation films 111 and the reflection films 112 are alternately arranged at substantially equal intervals by the transparent substrate 114 having the same thickness,
In addition, the regions 110a and 110b without the film are not provided on the transparent substrate for ensuring the optical path. The polarization separation film 111 is the same as that of the first embodiment.

According to the second embodiment, not only is it possible to deal with a specific incident angle of more than 45 ° and less than 90 °, but also the thickness of the polarization separation section group 11A can be reduced, which in turn results in polarization separation. There is an advantage that the conversion element can be thinned.

[0114]

As described above, according to the present invention,
There is an advantage that it is possible to realize a polarization splitting / converting element that can be manufactured at a low price and that can split and convert polarized light with high accuracy. That is, it is possible to deal with a specific incident angle of more than 45 ° and less than 90 °, and as a result, the degree of freedom in designing the polarization separation film is dramatically increased, and the use of a high-performance polarization separation film with a small number of layers is possible. It will be possible. Therefore, the polarization separation conversion element can be manufactured at a much lower cost than the current one.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a first embodiment of a PS polarization separation conversion device according to the present invention.

FIG. 2 is a diagram schematically showing an optical path of a PS polarization separation conversion device according to the first embodiment.

FIG. 3 is a diagram showing various structural parameters of the PS polarization separation conversion element according to the first embodiment.

FIG. 4 is a diagram for explaining the structure of a polarization separation film according to the present invention.

FIG. 5 is a diagram showing a stacking repeating structure of a polarization separation element in the case where the stacking repeating number m is 3.

FIG. 6 is a diagram showing a stacking repeating structure of a polarization separation element when the stacking repeating number m is 4.

FIG. 7 is a diagram showing the wavelength dispersion dependence of the optical constant (refractive index) n of TiO ₂ .

FIG. 8 is a diagram showing wavelength dispersion dependence of an optical constant (extinction coefficient) k of TiO ₂ .

FIG. 9 is a diagram showing wavelength dependence of an optical constant (refractive index) n of SiO ₂ .

FIG. 10 is a diagram showing the wavelength dependence of P-polarized light transmittance when the number of times m of stacking is repeated is 3 to 7.

FIG. 11 is a diagram showing the wavelength dependence of P-polarized light transmittance when the number of times m of lamination is 1, 2;

FIG. 12 is a diagram showing wavelength dependence of P-polarized light reflectance when the number of times m of lamination is repeated 3 to 7.

FIG. 13 is a diagram showing the wavelength dependence of the P-polarized light reflectance when the number of times m of stacking is repeated is 1 and 2.

FIG. 14 is a diagram showing the wavelength dependence of S-polarized light transmittance when the number of times m of lamination is repeated 3 to 7.

FIG. 15 is a diagram showing the wavelength dependence of S-polarized light transmittance when the number of times m of lamination is 1 and 2;

FIG. 16 is a diagram showing the wavelength dependence of S-polarized reflectance when the number of times m of stacking is repeated is 3 to 7.

FIG. 17 is a diagram showing the wavelength dependence of the S-polarized reflectance when the number of times m of lamination is repeated 1 and 2.

FIG. 18 is the number of repetitions of the wavelength range that can be separated by polarization when the width of a continuous wavelength range satisfying the conditions of the transmittance of P-polarized light of 83% or more and the transmittance of S-polarized light of 5% or less is used as the evaluation function. It is a figure which shows a dependency.

FIG. 19 is a diagram showing the wavelength dependence of the transmittance of P-polarized light and S-polarized light in the case where the stacking repetition number m is 4.

FIG. 20 is a diagram showing an incident angle dependency of a polarization separable wavelength width.

FIG. 21 is a diagram showing the wavelength dependence of the transmittance of P-polarized light and S-polarized light when the incident angle of the incident light on the polarization separation element having the number of repetitions m of 4 deviates by +3 degrees from the optimum condition of 56 degrees. .

FIG. 22 is a diagram showing the wavelength dependence of the transmittance of P-polarized light and S-polarized light when the incident angle of the incident light on the polarization separation element having the number of repetitions m of 4 deviates from the optimum condition of 56 degrees by −3 degrees. is there.

FIG. 23 is a diagram showing the wavelength dependence of the transmittance of P-polarized light and S-polarized light when the incident angle of incident light on the polarization beam splitting element having the number of repetitions m of 4 deviates from the optimum condition of 56 ° by + 5 °. .

FIG. 24 is a diagram showing the wavelength dependence of the transmittance of P-polarized light and S-polarized light when the incident angle of the incident light on the polarization separation element with the number of repetitions m of 4 deviates by −5 degrees from the optimum condition of 56 degrees. is there.

FIG. 25 is a configuration diagram schematically showing a second embodiment of a PS polarization separation conversion device according to the present invention.

FIG. 26 is a diagram schematically showing a configuration of a conventional PS polarization separation conversion element.

[Explanation of symbols]

10, 10A ... Polarization separation / conversion element, 11, 11A ... Polarization separation section, 12 ... Light-shielding mask, 13 ... λ / 2 plate, 111 ...
Polarization separation film, 111a ... Light incident surface, 111b ... Light transmitting surface, 3 ... Transparent substrate, H ... High refractive index layer, L ... Low refractive index layer,
L1 ... first low refractive index layer, L2 ... second low refractive index layer, L
HL1 ... First basic structure film, LHL2 ... Second basic structure film, LHL3 ... Third basic structure film, LHL4 ... Fourth basic structure film, 113a ... Thin transparent substrate, 113b ... Thick transparent substrate, 114 ... Transparent substrate.

Claims (32)

[Claims] 1. A polarization splitting film that transmits a first polarized light of incident light incident at a predetermined angle with respect to a light incident surface and reflects a second polarized light from the light incident surface in a direction different from a transmission direction. And a reflection surface is disposed so as to face the light incident surface of the polarization splitting film, and the second polarized light reflected by the polarization splitting film is reflected in a direction substantially parallel to the transmission direction of the first polarized light. A plurality of polarization splitting units including a reflection film, and a conversion unit that outputs the first polarization transmitted through the polarization splitting films of the respective polarization splitting units and the polarization directions of the second polarizations reflected by the reflection film in alignment with each other. The plurality of polarization splitting portions are arranged at predetermined intervals so that the polarization splitting films and the reflection films are alternately arranged in a direction substantially orthogonal to the incident direction of the incident light, The angle of incidence of each polarization separation film on the light incident surface is larger than 45 degrees. Polarization separation conversion element is set to a smaller specific angle than 90 degrees. 2. The distance between the polarization separation film and the reflection film in the polarization separation unit, the reflection film of the polarization separation unit adjacent to the polarization separation film of the polarization separation unit, or the polarization adjacent to the reflection film of the polarization separation unit. The polarization separation conversion element according to claim 1, wherein the separation section has a different distance from the polarization separation film. 3. When the incident angle of the incident light on the polarization separation film of the polarization separation section is x degrees (45 ° <x <90 °),
Distance t between the polarization separation film and the reflection film in the polarization separation section
The distance t ₂ between ₁ and the reflection film of the polarization separation unit adjacent to the polarization separation film of the polarization separation unit or the reflection film of the polarization separation unit adjacent to the polarization separation film of the polarization separation unit is t ₂ / t ₁ = polarization separation conversion element according to claim 2, wherein satisfying 4sin ² x-1 the relationship. 4. The light exit side of the polarization splitting part in the area where the polarization splitting film and the reflecting film face each other, and the light exiting side of the light splitting part is arranged so that the reflection film does not block the light entering surface of the polarization splitting film. 2. The polarization separation conversion element according to claim 1, wherein a region where no film is formed exists so as not to block the emission of the second polarized light reflected by the reflection film by the polarization separation film. 5. The light exiting side of the polarization splitting part in a region where the polarization splitting film and the reflecting film are opposed to each other so that the light entering side does not block the light entering surface of the polarization splitting film by the reflecting film. 4. The polarization separation conversion element according to claim 3, wherein there is a region where the film is not formed so as not to block the emission of the second polarized light reflected by the reflection film by the polarization separation film. 6. When the incident angle of the incident light on the polarization separation film of the polarization separation section is x degrees (45 ° <x <90 °),
In the above-mentioned polarized light separating section, the length of the region where the film is formed is
_1, when the length of the region that does not form a film and _{w 2, w 2 / w 1} = 0.5-1 / 2tan 2 x becomes polarization separation conversion element according to claim 4, wherein satisfying the relationship. 7. The polarization separating section, w ₁ the length of the region for forming the film, when the length of the region that does not form a film and _{w 2, w 2 / w 1} = 0.5-1 / 2tan The polarization separation conversion element according to claim 5, wherein the relationship of ² x is satisfied. 8. The width of the opening through which the first polarized light passing through the polarization separating film of each of the polarization separating portions passes and the width of the opening through which the second polarized light reflected by the reflecting film passes through are set to the same width. The polarization separation conversion element according to claim 6. 9. The width of the opening through which the first polarized light passing through the polarization separating film of each of the polarization separating sections and the width of the opening through which the second polarized light reflected by the reflecting film passes are set to the same width. The polarization separation conversion element according to claim 7. 10. At least the polarization separation film of the polarization separation film and the reflection film of each polarization separation unit is an optically transparent high refractive index layer H having a predetermined refractive index with respect to the incident light.
And a first low-refractive index layer L and a second low-refractive index layer L which are arranged so as to sandwich the high-refractive index layer H and which have a lower refractive index than the high-refractive index layer and which are optically transparent. Structure film LH
The polarization splitting conversion element according to claim 1, further comprising L, having a repeating structure (LHL) ^m of the basic structure. 11. The thickness of the high refractive index layer and the thicknesses of the first low refractive index layer and the second low refractive index layer are set based on a reference wavelength of incident light. The polarization separation conversion element described. 12. When the reference wavelength of the incident light is λ ₀ , the thickness of the high refractive index layer and the thicknesses of the first low refractive index layer and the second low refractive index layer are the reference wavelength. The polarization separation conversion element according to claim 10, wherein the polarization separation conversion element is set to an optical thickness corresponding to a value obtained by dividing by. 13. The number of repetitions m of the basic structure is 3
The polarization separation conversion element according to claim 10, wherein the polarization separation conversion element is an integer equal to or greater than the above. 14. The polarization separation / separation device according to claim 10, wherein a center value of an incident angle of the incident light on the light incident surface of the polarization separation film is set to around 56 degrees. 15. The high refractive index layer has wavelength dispersion characteristics of an optical constant n in a predetermined range including a reference wavelength of incident light, and has an extinction coefficient of substantially zero at a predetermined wavelength shorter than the reference wavelength. The first and second low refractive index layers each include a material having an asymptotic characteristic, have wavelength dispersion characteristics of an optical constant n in a predetermined range including a reference wavelength of incident light, and extinguish in a substantially entire wavelength range. The polarization separation conversion element according to claim 10, comprising a material having an extinction coefficient of substantially zero. 16. The polarization separation film and the reflection film of each of the polarization separation sections are arranged so as to be sandwiched between transparent substrates, and the high refractive index layer has a refractive index set higher than that of the transparent substrate. The polarization separation conversion element according to claim 10, wherein the first and second low refractive index layers have a refractive index lower than that of the transparent substrate. 17. The polarization separation film and the reflection film of each of the polarization separation sections are arranged so as to be sandwiched between transparent substrates, and the high refractive index layer has a refractive index set higher than that of the transparent substrate. The polarization splitting conversion element according to claim 15, wherein the first and second low refractive index layers have a refractive index lower than that of the transparent substrate. 18. The polarization separation conversion element according to claim 10, wherein the basic structure films adjacent to each other are formed so as to share the first low refractive index layer L and the second low refractive index layer L. 19. The polarization separation film and the reflection film of each polarization separation unit are arranged so as to be sandwiched by transparent substrates, and the center value of the incident angle of the incident light on the light incident surface of the polarization separation film is 5.
The incident angle of the incident light on the polarization splitting film of the polarization splitting part is set to around 6 degrees and x
When the degree (45 ° <x <90 °) is set, the thickness t ₁ of the transparent substrate, which is the distance between the polarization separation film and the reflection film in the polarization separation unit, is adjacent to the polarization separation film of the polarization separation unit. The thickness t ₂ of the transparent substrate, which is the distance between the polarization film of the polarization splitting unit or the polarization film of the polarization splitting unit and the polarization film of the adjacent polarization splitting unit, has a ratio of t ₂ / t ₁ = 1.75. In the area where the polarization separation film and the reflection film in the polarization separation section face each other, on the light incidence side, the polarization separation is performed on the light emission side so that the reflection film does not block the incidence on the light incidence surface of the polarization separation film. In order not to block the emission of the second polarized light reflected by the reflecting film by the film, there is a region where the film is not formed, and the length of the region where the film is formed in the polarization splitting part is w ₁ ,
If the length of the region where no film is formed is w ₂ , then w ₂ / w ₁
The polarization separation / conversion device according to claim 1, wherein the relationship of 0.27 is satisfied. 20. The polarization separation film and the reflection film of each of the polarization separation sections are arranged so as to be sandwiched by transparent substrates, and the center value of the incident angle of the incident light on the light incident surface of the polarization separation film is 5.
The incident angle of the incident light on the polarization splitting film of the polarization splitting part is set to around 6 degrees and x
When the degree (45 ° <x <90 °) is set, the thickness t ₁ of the transparent substrate, which is the distance between the polarization separation film and the reflection film in the polarization separation unit, is adjacent to the polarization separation film of the polarization separation unit. The thickness t ₂ of the transparent substrate, which is the distance between the polarization film of the polarization splitting unit or the polarization film of the polarization splitting unit and the polarization film of the adjacent polarization splitting unit, has a ratio of t ₂ / t ₁ = 1.75. In the region where the polarization separation film and the reflection film in the polarization separation unit face each other, on the light incidence side, the polarization separation is performed on the light emission side so that the reflection film does not block the incidence on the light incidence surface of the polarization separation film. In order not to block the emission of the second polarized light reflected by the reflecting film by the film, there is a region where the film is not formed, and the length of the region where the film is formed in the polarization splitting part is w ₁ ,
If the length of the region where no film is formed is w ₂ , then w ₂ / w ₁
The polarization separation conversion element according to claim 10, wherein the relationship of 0.27 is satisfied. 21. A polarization separation film which transmits a first polarized light of incident light incident at a predetermined angle with respect to a light incident surface and reflects a second polarized light from the light incident surface in a direction different from a transmission direction. And a reflection surface is arranged so as to face the light incident surface of the polarization separation film, and the second polarized light reflected by the polarization separation film is reflected in a direction substantially parallel to the transmission direction of the first polarized light. The polarization separation film for the incident light, which has a reflection film and a conversion unit for emitting the first polarization transmitted through the polarization separation film and the second polarization reflected by the reflection film in the same polarization direction. A polarization separation conversion element in which an incident angle with respect to a light incident surface is set to a specific angle larger than 45 degrees and smaller than 90 degrees. 22. At least the polarization separation film of the polarization separation film and the reflection film is an optically transparent high refractive index layer H having a predetermined refractive index with respect to the incident light, and the high refractive index layer H. The first low refractive index layer L and the second optically transparent low refractive index layer L having a refractive index lower than that of the high refractive index layer.
22. The polarization separation / conversion device according to claim 21, further comprising a basic structure film LHL including the low refractive index layer L, and having a repeating structure (LHL) ^m of the basic structure. 23. The thickness of the high refractive index layer and the thicknesses of the first low refractive index layer and the second low refractive index layer are set based on a reference wavelength of incident light. The polarization separation conversion element described. 24. When the reference wavelength of the incident light is λ ₀ , the thickness of the high refractive index layer and the thickness of the first low refractive index layer and the second low refractive index layer are the reference wavelength. 23. The polarization separation conversion element according to claim 22, wherein the polarization separation conversion element is set to an optical thickness corresponding to a value obtained by dividing by. 25. The number of repetitions m of the basic structure is 3
The polarization splitting conversion element according to claim 22, wherein the polarization splitting conversion element is an integer not less than the above. 26. The number of repetitions m of the basic structure is 3
The polarization separation conversion element according to claim 22, wherein the polarization separation conversion element is an integer of 7 or more and 7 or less. 27. The polarization beam splitting device according to claim 22, wherein the center value of the incident angle of the incident light on the optical film surface is set to around 56 degrees. 28. The polarization beam splitting element according to claim 26, wherein the center value of the incident angle of the incident light on the optical film surface is set in the vicinity of 56 degrees. 29. The high refractive index layer has a wavelength dispersion characteristic of an optical constant n in a predetermined range including a reference wavelength of incident light, and has an extinction coefficient of substantially zero at a predetermined wavelength shorter than the reference wavelength. The first and second low refractive index layers each include a material having an asymptotic characteristic, have wavelength dispersion characteristics of an optical constant n in a predetermined range including a reference wavelength of incident light, and extinguish in a substantially entire wavelength range. The polarization splitting conversion element according to claim 22, comprising a material having an extinction coefficient of substantially zero. 30. The polarization separation film and the reflection film of the polarization separation section are arranged so as to be sandwiched between transparent substrates, and the high refractive index layer has a refractive index higher than that of the transparent substrate. The polarization separation conversion element according to claim 22, wherein the first and second low refractive index layers have a refractive index lower than that of the transparent substrate. 31. The polarization separation film and the reflection film are formed on surfaces of a transparent substrate which face each other, and a refractive index of the high refractive index layer is set to be higher than a refractive index of the transparent substrate. 30. The polarization separation conversion element according to claim 29, wherein the refractive index of the second low refractive index layer is set lower than the refractive index of the transparent substrate. 32. The polarization separation conversion element according to claim 22, wherein the basic structure films adjacent to each other are formed so as to share the first low refractive index layer L and the second low refractive index layer L.