JP2002328227A - Polarizing beam splitter, illumination optical system and liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing beam splitter with little variance of characteristics related to wavelength of incident p-polarized light deviating from the Brewster angle condition, an illumination optical system and a liquid crystal projector both using the polarizing beam splitter. SOLUTION: A polarization separating coat (4b) of the polarizing beam splitter (4) has laminated structure (4a) |M(λ0 )A×M(k×λ0 )A×M(k<2> ×λ0 )A×M(k<3> ×λ0 )A×...× M(kB<-1> ×λ0 )A| (4c) satisfying a conditional expression 2×A<=B. M(λ) is fundamental periodic structure expressed by (H×L), (L×H), (H/2×L×H/2), (L/2×H×L/2) corresponding to a wavelength region of a designed dominant wavelength λ (=λ0 , k×λ0 , k<2> ×λ0 , k<3> ×λ0 ,..., kB<-1> ×λ0 ), λ0 is a reference wavelength, k is a coefficient, A is the number of repeated periods, B is the number of sets for the whole multilayer film taking the fundamental periodic structure with the identical designed dominant wavelength λ, as one set and H and L are λ0 /4 layers with refractive indexes with respect to the reference wavelength λ0 being nH and nL respectively (nH>nL).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polarizing beam splitter, an illumination optical system having the same, and a liquid crystal projector.

[0002]

2. Description of the Related Art An illumination optical system of a liquid crystal projector is required to have a wide band polarization separation including angle characteristics. In order to satisfy this requirement, for example, a polarization beam splitter proposed in Japanese Patent Application Laid-Open No. H11-23842 shifts a design dominant wavelength and overlaps an opaque band of S-polarized light to widen a wavelength band in which polarization separation is possible. Is secured.

[0003]

However, Japanese Patent Application Laid-Open No.
In the polarization beam splitter proposed in Japanese Patent No. 23842, only S-polarized light is considered with respect to the incident angle width. For this reason, if the incident angle of the P-polarized light deviates from the Brewster angle condition, there is a large difference in the characteristics depending on the wavelength. The characteristic difference due to the wavelength of the P-polarized light that deviates from the Brewster angle condition is particularly remarkable in polarization separation in which the P-polarized light is transmitted twice through the multilayer film. Cause. Further, since the total number of layers is set to be relatively large in order to sufficiently secure the reflection characteristics of S-polarized light, the transmittance of P-polarized light that is outside the Brewster angle condition is low. Therefore, when the P-polarized light is transmitted through the multilayer film twice in the polarization separation, the influence of the decrease in the transmittance on the polarization separation performance becomes large.

The present invention has been made in view of such circumstances, and a polarization beam splitter having a small variation in characteristics with respect to wavelength with respect to P-polarized light incident outside the Brewster angle condition, and an illumination optical system using the same. It is an object to provide a system and a liquid crystal projector.

[0005]

In order to achieve the above object, a polarizing beam splitter according to a first aspect of the present invention is a polarizing beam splitter comprising a first transparent substrate and a second transparent substrate sandwiching a multilayer film. Multilayer structure with the following layers
(f) and the following conditional expression (1) is satisfied. (1st transparent substrate) | M (λ ₀ ) ^A · M (k · λ ₀ ) ^A · M (k ² · λ ₀ )
^A · M (k ³ · λ ₀ ) ^A ···· M (k ^B−1 · λ ₀ ) ^A | (second transparent substrate) (f) 2.A ≦ B (1) where M (λ ): Design dominant wavelength λ (= λ ₀ , k · λ ₀ , k ² · λ ₀ , k ³ ·
λ ₀ ,..., k ^B−1 · λ ₀ ), and (H · L), (L
.H), (H / 2.L.H / 2) or (L / 2.H.L /
2) Basic periodic structure represented by 2), λ ₀ : Reference wavelength, k: Coefficient, A: Repetition period, B: Multi-layer when basic periodic structure M (λ) of the same design main wavelength λ is set as one set The number of sets of the entire film, H, L: the refractive indexes for the reference wavelength λ ₀ are n _H and n
Is _{L λ 0/4} layers (where n _H> n _L), a.

According to a second aspect of the present invention, there is provided a polarization beam splitter according to the first aspect, further satisfying the following conditional expression (2). 1.4 <A · B · sin ⁻¹ [(n _H ² −n _L ² ) / (n _H ² + n _L ² )] · ln (n _H ² / n _L ² ) <2.0 (2)

An illumination optical system according to a third aspect of the present invention includes a first lens array for dividing incident light into a large number of light beams, and a second lens array for illuminating an area to be illuminated with the light beams divided by the first lens array. An integrator optical system, the polarizing beam splitter according to the first or second invention for separating incident light into two linearly polarized lights having different polarization directions between the first and second lens arrays, and the light is split by the polarizing beam splitter. A polarization conversion optical system comprising a half-wave plate for aligning the polarization direction of one linearly polarized light to the polarization direction of the other linearly polarized light, wherein the first transparent base is one or more. Wherein the second transparent substrate is a parallel flat plate.

[0008] A liquid crystal projector according to a fourth aspect of the present invention includes the illumination optical system according to the third aspect of the present invention.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a polarization beam splitter, an illumination optical system, and a liquid crystal projector embodying the present invention will be described with reference to the drawings. FIG. 1 schematically shows an embodiment of a liquid crystal projector, and FIG. 2 shows an expanded part of an illumination optical system in the liquid crystal projector. This liquid crystal projector comprises a light source (1), a reflector (2), a first lens array (3a), a second lens array (3b), a half-wave plate
(3c), polarizing beam splitter (4), dichroic mirror (5a, 5b), relay lens (6a, 6b), folding mirror (7a,
7b, 7c), condenser lens (8R, 8G, 8B), polarizing plate on the incident side
(9R, 9G, 9B), transmission type liquid crystal panel (10R, 10G, 10B), exit side polarizing plate (11R, 11G, 11B), cross dichroic prism (12), projection lens (13), etc. ing.

The illumination optical system of this liquid crystal projector includes an integrator optical system, a polarization conversion optical system, a color separation optical system,
A color combining optical system and the like are provided. The integrator optical system includes a first lens array (3) for dividing incident light into a large number of light beams.
a) and a second lens array (3b) that illuminates the liquid crystal panels (10R, 10G, 10B) by superposing the light beams split by the first lens array (3a). The polarization conversion optical system
A polarizing beam splitter (4) for separating incident light into two linearly polarized lights (P-polarized light and S-polarized light) having different polarization directions between the first and second lens arrays (3a, 3b), and a polarizing beam splitter (4). A half-wave plate (3c) for aligning the polarization direction of one of the separated linearly polarized light (P-polarized light) with the polarization direction of the other linearly polarized light (S-polarized light).
And it consists of The color separation optical system is composed of two dichroic mirrors (5a, 5b), and the color synthesis optical system is composed of a cross dichroic prism (12).

The light source (1) generates and emits white natural light (randomly polarized light), which is converted into substantially parallel light rays by the reflector (2). Then, the first and second lens arrays (3a, 3
The spatial energy distribution is made uniform by the integrator optical system consisting of b). This will be described in more detail. The first lens array (3a) is a liquid crystal panel to be illuminated.
(10R, 10G, 10B) has a plurality of lens cells having openings substantially similar in shape to each other. The lens cells divide the illumination light into a large number of light fluxes and collect the light at the opening of the second lens array (3b). Light up. The second lens array (3b) transmits a plurality of light beams split by the first lens array (3a) to the liquid crystal panels (10R, 10G, 1).
0B) The illumination distribution is made uniform by overlapping and illuminating. That is, the light source (1) and the second lens array (3b)
Are substantially conjugate, a plurality of secondary light source images are formed near the second lens array (3b), and the first lens array
Since (3a) and the liquid crystal panels (10R, 10G, 10B) are substantially conjugate, the liquid crystal panels (10R, 10G, 10B) are uniformly illuminated. Furthermore, the illumination light is telecentric toward the liquid crystal panel (10R, 10G, 10B) by each condenser lens (8R, 8G, 8B), so that the liquid crystal panel (1
0R, 10G, 10B) are uniformly illuminated.

[0012] Between the first and second lens arrays (3a, 3b),
A polarizing beam splitter (4) is provided. The polarizing beam splitter (4) has a configuration in which a multilayer film is sandwiched between a first transparent substrate and a second transparent substrate. here,
The triangular prism array (4a) composed of a plurality of triangular prisms corresponds to a first transparent substrate, the parallel plate (4c) corresponds to a second transparent substrate, and the polarization separation coat (4b) corresponds to a multilayer film. Note that the first transparent base may be composed of one triangular prism.

The polarizing beam splitter (4) is a parallel flat plate (4
c) to form a polarization separation coat (4b),
Triangle prism array (4a) with UV curable resin on the surface of b)
Is obtained by molding. Triangular prism array (4
It is desirable that the refractive index of a) be set to a value that causes total reflection by the parallel flat plate (4c) without loss of light quantity. For example, when the incident angle with respect to the parallel plate (4c) is 45 °, the triangular prism array (4a)
Is preferably 1.59 or more including the angular width of the light beam. The polarized light separating coat (4b) composed of a multilayer film is an alternating laminated film formed by alternately laminating a high refractive index layer (refractive index: n _H ) and a low refractive index layer (refractive index: n _L ). (n _H > n
_L ). The film configuration will be described later in detail.

In the illumination light having passed through the first lens array (3a), S-polarized light is reflected by the polarization separation coat (4b), and P-polarized light passes through the polarization separation coat (4b). P polarized light is a parallel plate (4
After being totally reflected in c), the light passes through the polarization separation coat (4b) again. Then, only the P-polarized light is incident on the half-wave plate (3c) provided on the light emission side surface of the second lens array (3b), and is converted into S-polarized light. The P-polarized light separated by the polarization beam splitter (4) is converted into S-polarized light by the half-wave plate (3c), so that the illumination light exiting the polarization conversion optical system is linearly polarized light (polarized light) having the same polarization direction. (S-polarized light). Thus, by arranging the polarization directions of the illumination light in the polarization conversion optical system, the illumination light passes through the polarizing plates (9R, 9G, 9B) without waste, and the light use efficiency is improved.

The white illumination light emitted from the integrator optical system and the polarization conversion optical system is applied to a dichroic mirror (5).
a, 5b), three color lights corresponding to the three primary colors {that is, red (R)
Color light of green (G) and blue (B)}. That is,
The dichroic mirror (5a) performs color separation of the R and G color lights and the B color light, and the dichroic mirror (5b) performs the color separation of the R color light and the G color light. The B color light passes through the dichroic mirror (5a), is reflected by the return mirror (7c), and then passes through the condenser lens (8B). On the other hand, R,
The G color light is reflected by the dichroic mirror (5a). The G color light reflected by the dichroic mirror (5a) is reflected by the dichroic mirror (5b) and then condensed.
Pass (8G). The R color light reflected by the dichroic mirror (5a) passes through the dichroic mirror (5b),
The light passes through a relay optical system including a relay lens (6a, 6b) and a return mirror (7a, 7b), and passes through a condenser lens (8R).

The power of each of the condenser lenses (8R, 8G, 8B) is determined so that the emitted light enters the pupil of the projection lens (13). That is, as described above, the illumination light is telecentric toward the liquid crystal panels (10R, 10G, 10B).
After passing through the condenser lenses (8R, 8G, 8B), the RGB color lights pass through the polarizing plates (9R, 9G, 9B), and then the liquid crystal panels (10R, 10G, 10B) arranged near them. ). At this time, the G and B color lights are incident on the liquid crystal panels (10G and 10B) with the same optical path length, and the R color light is the G and B color lights.
The light enters the liquid crystal panel (10R) with an optical path length different from that of the B color light. Thus, even if there is a difference in the optical path length, the R color light is transmitted in the same magnification relay lens (6a, 6b) disposed in the optical path.
3 LCD panels (10R, 10R
G, 10B) are equivalent.

Each liquid crystal panel (10R, 10G, 10B) modulates each color light having a uniform polarization direction by selective polarization control according to the display of each pixel of a two-dimensional image (that is, ON / OFF for each pixel). Then, the transmitted light composed of two types of polarized light (P-polarized light and S-polarized light) is emitted. Only a specific polarization of the transmitted light is polarized (11R, 11R).
G, 11B) and enters the cross dichroic prism (12). The RGB color lights transmitted through the polarizing plates (11R, 11G, 11B) are combined in color by a cross dichroic prism (12) to become projection light, and are projected on a screen (not shown) by a projection lens (13). Cross dichroic prism (1
2) coaxially color-combines the light emitted from each of the liquid crystal panels (10R, 10G, 10B) so that a single projection lens (13) can project onto a screen. The projection lens (13) is an optical system that is telecentric on the liquid crystal panel (10R, 10G, 10B) side according to the illumination light.

As described above, if the incident angle of the P-polarized light deviates from the Brewster's angle condition, a large difference occurs in the characteristics depending on the wavelength, which causes color unevenness in the liquid crystal projector. This will be described in more detail. As shown in FIG. 2, a light ray (solid line) arriving at position i of the liquid crystal panel (10G) is incident on the polarization separation coat (4b) at an incident angle θi, and reaches a position j of the liquid crystal panel (10G) ( The dashed line) enters the polarization separation coat (4b) at an incident angle θj. As described above, the angle of incidence of the light beam on the polarizing beam splitter (4) determines the illumination position on the liquid crystal panel (10G) to be illuminated by the light beam. Unevenness will occur.

When the P-polarized light enters the polarization separation coat (4b) outside the Brewster angle condition, reflection occurs in a specific wavelength range corresponding to the design dominant wavelength. When the number of repetitions of the basic period is increased, the reflection becomes more remarkable, and the characteristic difference due to the wavelength of the P-polarized light increases. In the polarization beam splitter (4) of the present embodiment, in order to prevent the transmission characteristics of the P-polarized light incident out of the Brewster angle condition from varying with wavelength, the number of repetitions of the basic period is reduced, and By slightly varying the design dominant wavelength, an increase in the reflection of P-polarized light in a specific wavelength range is prevented. Specifically, the polarization separation coat (4b) composed of a multilayer film has the following laminated structure (f) and satisfies the following conditional expression (1).

(First transparent substrate) | M (λ ₀ ) ^A · M (k · λ ₀ ) ^A
· M (k ² · λ ₀ ) ^A · M (k ³ · λ ₀ ) ^A ···· M (k ^B-1 · λ ₀ ) ^A |
(Second transparent substrate) (f) 2 · A ≦ B (1) where M (λ): design dominant wavelength λ (= λ ₀ , k · λ ₀ , k ² · λ ₀ , k ³ ·
λ ₀ ,..., k ^B−1 · λ ₀ ), and (H · L), (L
.H), (H / 2.L.H / 2) or (L / 2.H.L /
2) Basic periodic structure represented by 2), λ ₀ : Reference wavelength, k: Coefficient, A: Repetition period, B: Multi-layer when basic periodic structure M (λ) of the same design main wavelength λ is set as one set The number of sets of the entire film, H, L: the refractive indexes for the reference wavelength λ ₀ are n _H and n
Is _{L λ 0/4} layers (where n _H> n _L), a.

The polarizing beam splitter (4) has a laminated structure (f).
And the conditional expression (1) is satisfied, so that there is little wavelength dependence of the P-polarized light depending on the incident angle, and good polarization separation can be achieved. If the above conditional expression (1) is not satisfied, the transmission characteristics of the P-polarized light incident out of the Brewster angle condition vary depending on the wavelength, and the characteristic difference due to the wavelength of the P-polarized light increases.
In the polarization separation configuration in which P-polarized light transmits twice through the multilayer film and S-polarized light is reflected once by the multilayer film as in this embodiment, P-polarized light is more susceptible to the influence of the multilayer film than S-polarized light. It is particularly preferable to use a polarization beam splitter (4) having a small characteristic difference depending on the wavelength of P-polarized light, in order to achieve good polarization conversion.

Generally, in a basic periodic structure composed of a high refractive index layer (refractive index: n _H ) and a low refractive index layer (refractive index: n _L ) satisfying the Brewster angle condition, the opaque band width of S-polarized light is si.
Since it is proportional to n ⁻¹ [(n _H ² −n _L ² ) / (n _H ² + n _L ² )], the number I of sets of the basic periodic structure required for the required wavelength band is
It is inversely proportional to sin ⁻¹ [(n _H ² −n _L ² ) / (n _H ² + n _L ² )]. Further, the required number of repetition periods J for the reflectance at the center of the opaque band of the S-polarized light is inversely proportional to ln (n _H ² / n _L ² ). Therefore, the total number I · J of the required number of multilayer films for the required wavelength band is expressed by the following formula: I · J = α / {sin ⁻¹ [(n _H ² −n)
_L ² ) / (n _H ² + n _L ² )] · ln (n _H ² / n _L ² )}. Here, when the value of α is large, the reflection of the P-polarized light increases, and when the value of α is small, the transmission of the S-polarized light increases. Range (1.4 <α <
If it is set to 2.0), it is possible to obtain a polarization beam splitter (4) that can perform good polarization separation.

In view of the above, the polarizing beam splitter (4)
Preferably satisfies the following conditional expression (2). If the lower limit of conditional expression (2) is exceeded, the reflectance of S-polarized light will be too low overall. If the upper limit of conditional expression (2) is exceeded, the transmittance of P-polarized light will be reduced overall. Would be too much. 1.4 <A · B · sin ⁻¹ [(n _H ² −n _L ² ) / (n _H ² + n _L ² )] · ln (n _H ² / n _L ² ) <2.0 (2)

The polarization beam splitter (4) of the present embodiment
According to the method, it is possible to reduce the variation in the transmission characteristics with respect to the wavelength of the P-polarized light that is incident out of the Brewster angle condition. Then, the number of repetition periods of the basic periodic structure {M (λ)} of the multilayer film in the polarizing beam splitter (4)
(A) is reduced and the number of sets (B) of fundamental periodic structures {M (λ)} having different design dominant wavelengths (λ) is increased, so that an appropriate layer for a necessary wavelength band is provided. Number can be set. Therefore, the number of layers of the multilayer film can be reduced, and cost reduction and improvement in reliability can be achieved. According to the liquid crystal projector using the polarizing beam splitter (4), the dispersion of the characteristics of the P-polarized light that deviates from the Brewster angle condition in the polarization separation is reduced, so that there is no color unevenness and good color reproducibility. The projected image can be obtained. In addition, in the polarization separation, the reflection characteristic of S-polarized light is slightly reduced, and the transmission characteristic of P-polarized light that deviates from the Brewster angle condition is increased, so that the polarization conversion efficiency is improved and a bright projected image can be obtained.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a polarizing beam splitter embodying the present invention will be described more specifically with reference to its optical configuration and spectral characteristics. Tables 1 to 7 show the optical configurations (multilayer film configurations) of the polarizing beam splitters of Examples 1 to 5 and Comparative Example, respectively.
In Tables 1 to 7, n _G is the refractive index of the triangular prism array (4a) or the parallel plate (4c) corresponding to the first and second transparent substrates,
A and B are the number of repetition periods and the number of sets in the conditional expression (1), and α is the corresponding value of the conditional expression (2): α = A · B · sin ⁻¹ [(n _H ² −
n _L ²⁾ is ^{_{/ (n H 2 + n L}} 2)] · ln (n H 2 / n L 2). 3 to 8 show the polarization separation characteristics of the polarization beam splitters of Examples 1 to 5 and Comparative Example in terms of spectral transmittance. FIG.
8, P (θ) indicates the transmittance of P-polarized light at the incident angle θ (°) to the film surface, and S (θ) indicates S at the incident angle θ (°) to the film surface. It shows the transmittance of polarized light.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

[Table 7]

[0033]

As described above, according to the polarizing beam splitter according to the present invention, it is possible to reduce the variation of the characteristics with respect to the wavelength with respect to the P-polarized light incident outside the Brewster angle condition. In addition, since the number of repetition periods of the basic periodic structure of the multilayer film in the polarization beam splitter is reduced and the number of sets of the basic periodic structures having different design dominant wavelengths is increased, an appropriate number is set for a necessary wavelength band. The number of layers can be set. Therefore, the number of layers of the multilayer film can be reduced, and cost reduction and improvement in reliability can be achieved. According to the liquid crystal projector of the present invention, the dispersion of the characteristics of the P-polarized light that deviates from the Brewster angle condition in the polarization separation is reduced, so that a good projected image with no color unevenness and good color reproducibility can be obtained. In addition, since the reflection characteristic of S-polarized light is slightly reduced in polarization separation, and the transmission characteristic of P-polarized light that deviates from the Brewster angle condition is increased,
The polarization conversion efficiency is improved and a bright projected image is obtained.

[Brief description of the drawings]

FIG. 1 is an optical configuration diagram schematically showing an embodiment of a liquid crystal projector.

FIG. 2 is a sectional view showing a part of an illumination optical system in the liquid crystal projector shown in FIG.

FIG. 3 is a graph showing the polarization separation characteristics of Example 1 in terms of spectral transmittance.

FIG. 4 is a graph showing polarization separation characteristics of Example 2 in terms of spectral transmittance.

FIG. 5 is a graph showing the polarization separation characteristics of Example 3 in terms of spectral transmittance.

FIG. 6 is a graph showing polarization separation characteristics of Example 4 in terms of spectral transmittance.

FIG. 7 is a graph showing the polarization separation characteristics of Example 5 in terms of spectral transmittance.

FIG. 8 is a graph showing polarization separation characteristics of a comparative example as spectral transmittance.

[Explanation of symbols]

 3a ... first lens array 3b ... second lens array 3c ... 1/2 wavelength plate 4 ... polarizing beam splitter 4a ... triangular prism array (first transparent substrate) 4b ... polarization separating coat (multilayer film) 4c ... parallel plate (second (2 transparent substrate)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 19/00 G02F 1/13 505 2K009 G02F 1/13 505 1/1335 1/1335 510 510 G03B 21/00 E G03B 21/00 21/14 Z 21/14 G02B 1/10 Z F term (reference) 2H042 CA10 CA12 CA17 2H049 BA05 BA46 BB03 BC01 BC09 BC22 2H052 BA02 BA03 BA09 BA14 2H088 EA14 EA15 HA13 HA16 HA18 HA20 HA21 HA05 HA25 KA28 KA30 MA04 MA20 2H091 FA05Z FA08X FA08Z FA10Z FA14Z FA26X FA26Z FA29Z FA41Z KA01 KA10 LA15 LA16 MA07 2K009 BB02 CC01 EE00

Claims (4)

[Claims] 1. A polarizing beam splitter comprising a first transparent substrate and a second transparent substrate sandwiching a multilayer film, wherein the multilayer film has the following laminated structure (f), and the following conditional expression (1): (1st transparent substrate) | M (λ ₀ ) ^A · M (k · λ ₀ ) ^A · M (k ² · λ ₀ )
^A · M (k ³ · λ ₀ ) ^A ···· M (k ^B−1 · λ ₀ ) ^A | (second transparent substrate) (f) 2.A ≦ B (1) where M (λ ): Design dominant wavelength λ (= λ ₀ , k · λ ₀ , k ² · λ ₀ , k ³ ·
λ ₀ ,..., k ^B−1 · λ ₀ ), and (H · L), (L
.H), (H / 2.L.H / 2) or (L / 2.H.L /
2) Basic periodic structure represented by 2), λ ₀ : Reference wavelength, k: Coefficient, A: Repetition period, B: Multi-layer when basic periodic structure M (λ) of the same design main wavelength λ is set as one set The number of sets of the entire film, H, L: the refractive indexes for the reference wavelength λ ₀ are n _H and n
Is _{L λ 0/4} layers (where n _H> n _L), a. 2. The polarization beam splitter according to claim 1, further satisfying the following conditional expression (2). 1.4 <A · B · sin ⁻¹ [(n _H ² −n _L ² ) / (n _H ² + n _L ² )] · ln (n _H ² / n _L ² ) <2.0 (2) 3. An integrator optical system comprising: a first lens array for dividing incident light into a number of light beams; a second lens array for illuminating an illuminated area with the light beams split by the first lens array; And separating the incident light into two linearly polarized lights having different polarization directions between the second lens array and the second lens array.
Or a polarization conversion optical system comprising a half-wave plate for aligning the polarization direction of one linearly polarized light separated by the polarization beam splitter with the polarization direction of the other linearly polarized light. An illumination optical system, wherein the first transparent substrate includes one or a plurality of triangular prisms,
An illumination optical system, wherein the second transparent base is made of a parallel plate. 4. A liquid crystal projector comprising the illumination optical system according to claim 3.