JP2006065247A - Polarizing beam splitter and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing beam splitter capable of utilizing s-polarized light and p-polarized light having different colors on one optical axis without using a color filter or else, to provide a manufacturing method of the polarizing beam splitter, and to provide an optical instrument having such a polarizing beam splitter. <P>SOLUTION: The polarizing beam splitter is provided with a pair of transparent base bodies 1a, 1b, and a multilayer film 2 consisting of a high refractive index layer and a low refractive index layer laminated between the transparent base bodies 1a, 1b. The polarizing beam splitter satisfies the relation (1):nL<nS, nH, the relation (2):θ>sin<SP>-1</SP>(nL/nS), and the relation (3):dLmax<λmax, the number of layers of the multilayer 2 is fifteen or more, transmittance Ts of s-polarized light is higher than transmittance Tp of p-polarized light in a first wavelength band W1, and transmittance Tp of p-polarized light is higher than transmittance Ts of s-polarized light in a second wavelength band W2. In the relations, nL denotes refractive index of the low refractive index layer, nS denotes refractive index of the transparent base body, nH denotes refractive index of the high refractive index layer, θ denotes reflection angle on the interface with the multilayer of light made vertically incident to one side transparent base body 1a, λmax denotes the maximum value of usage wavelength and dLmax denotes the maximum optical layer thickness of the low refractive index layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element, which is a constituent element of a projector, an optical disk device, a laser printer, a laser processing machine, a measuring device, and the like, an infrared cut filter, a polarizing beam splitter used as an infrared pass filter, and a manufacturing method thereof.

  The polarization beam splitter generally includes two prisms, and has a high refractive index material layer and a low refractive index material layer alternately stacked between the slopes or bottom surfaces of both prisms. Since the polarization beam splitter efficiently separates the incident light into P-polarized light and S-polarized light by interference of the multilayer film, it is used in an optical system such as an optical disk device or a projection display device.

  The wavelength range of the light to be separated and whether P-polarized light or S-polarized light is transmitted (or reflected) is determined by the combination of the high refractive index material and the low refractive index material constituting the multilayer film. For example, a polarizing beam splitter described in Japanese Patent Application Laid-Open No. 11-211946 (Patent Document 1) reflects S-polarized light and transmits P-polarized light in almost the entire visible light wavelength range. The polarizing beam splitter described in JP-A-9-184916 (Patent Document 2) also reflects S-polarized light and transmits P-polarized light, and exhibits predetermined polarization characteristics even when the incident beam has a divergence angle of ± 5 ° or more. . On the other hand, the polarization beam splitter described in US Pat. No. 5,912,762 (patent document 3) transmits S-polarized light and reflects P-polarized light.

  In recent years, in the field of liquid crystal projectors and the like, there is a need to use polarized light of different colors such as yellow S-polarized light and red P-polarized light on the same optical axis. However, the polarization beam splitters proposed so far, including the example above, (a) transmit only one of P-polarized light and S-polarized light in a specific wavelength region, and (b) only the other in a different wavelength region. There is no one that has a function of transmitting light. Therefore, when using polarized light of different colors on the same optical axis, it is necessary to combine a polarizing beam splitter, a color filter (dichroic filter), and a mirror.

  FIG. 10 shows a conventional example of an optical system that guides polarized light of different colors on the same optical axis. This optical system includes a polarizing beam splitter 3 composed of triangular prisms 3a and 3b and a multilayer film 4, a color filter 6 provided on the transmitted light side of the polarizing beam splitter 3, and reflected light from the polarizing beam splitter 3 at a predetermined angle. And a mirror 5. The color filter 6 has a function of reflecting red light and transmitting other light. Of the light L incident on the vertical surface 31 a of the triangular prism 3 a, S-polarized light is transmitted through the multilayer film 4, and P-polarized light is reflected by the multilayer film 4. The S-polarized light emitted from the vertical surface 31b is incident on the color filter 6, only the red light Sr is reflected by the color filter 6, and other light (Sg and Sb) is transmitted. The P-polarized light emitted from the horizontal plane 32a is reflected by the mirror 5, and then enters the color filter 6 from the opposite side of the S-polarized light incident surface. The red light Pr is reflected, and the green S-polarized light Sg and the blue S-polarized light Sb. Is transparent.

  Thus, the red P-polarized light Pr and the cyan S-polarized light (Pg and Pb) can be guided on the same optical axis by the optical system shown in FIG. However, this optical system requires a color filter 6 and a mirror 5 in addition to the polarizing beam splitter 3 and has a problem that it is unsuitable for a small-sized optical apparatus because of many parts.

Japanese Patent Laid-Open No. 11-211946 JP-A-9-184916 U.S. Pat.No. 5,912,762

  Accordingly, an object of the present invention is to provide a polarizing beam splitter that makes it possible to use S-polarized light and P-polarized light having different colors on one optical axis without using a color filter or the like, and a manufacturing method thereof.

  As a result of diligent research in view of the above object, the present inventors have found that in a polarizing beam splitter composed of a transparent substrate and a multilayer film, the refractive index of each of the transparent substrate and each layer, the thickness of each layer, the refraction angle of the transparent substrate, and the wavelength used. (A) Reflect P-polarized light and transmit S-polarized light in a certain wavelength region, and (b) Reflect S-polarized light and transmit P-polarized light in other wavelength regions. Then, it was discovered that S-polarized light and P-polarized light having different colors can be used on the transmission optical axis of the polarizing beam splitter, and the present invention was conceived.

That is, the polarizing beam splitter of the present invention comprises a pair of transparent substrates and a multilayer film composed of a high refractive index layer and a low refractive index layer laminated between the transparent substrates, and the following formulas (1), (2) and (3)
nL <nS, nH (1)
θ > sin ^-1 (nL / nS) (2)
dLmax <λmax (3)
(Where nL represents the refractive index of the low refractive index layer, nS represents the refractive index of the transparent substrate, nH represents the refractive index of the high refractive index layer, and θ represents one transparent substrate. The angle of reflection of the perpendicularly incident light at the interface with the multilayer film, λmax indicates the maximum value of the used wavelength, and dLmax indicates the maximum optical layer thickness of the low refractive index layer. The number is 15 or more, the transmittance of S-polarized light is higher than the transmittance of P-polarized light in the first wavelength band, and the transmittance of P-polarized light is higher than the transmittance of S-polarized light in the second wavelength band. Features.

  The first and second wavelength bands are in a visible region, and in the first wavelength band, the transmittance of S-polarized light is 80% or more and the transmittance of P-polarized light is 20% or less. In the wavelength band, it is preferable that the transmittance of P-polarized light is 80% or more and the transmittance of S-polarized light is 20% or less.

The method for manufacturing a polarizing beam splitter according to the present invention is such that a multilayer film comprising a high refractive index layer and a low refractive index layer is provided on the bottom surface of the first transparent substrate, and the multilayer film is bonded to the bottom surface of the second transparent substrate. The number of layers of the multilayer film is 15 or more, and the following formulas (1), (2) and (3)
nL <nS, nH (1)
θ > sin ^-1 (nL / nS) (2)
dLmax <λmax (3)
(Where nL represents the refractive index of the low refractive index layer, nS represents the refractive index of the transparent substrate, nH represents the refractive index of the high refractive index layer, and θ represents one transparent substrate. The angle of reflection of the perpendicularly incident light at the interface with the multilayer film is shown, λmax shows the maximum value of the used wavelength, and dLmax shows the maximum optical layer thickness of the low refractive index layer. The transmittance of S-polarized light in the wavelength band is made higher than the transmittance of P-polarized light, and the transmittance of P-polarized light in the second wavelength band is made higher than the transmittance of S-polarized light.

  In the polarization beam splitter of the present invention, S-polarized light exhibits higher transmittance than P-polarized light in the first wavelength band, and P-polarized light exhibits higher transmittance than S-polarized light in the second wavelength band. In a preferred embodiment, the P-polarized light hardly transmits in the first wavelength band, and the S-polarized light hardly transmits in the second wavelength band. For this reason, S-polarized light and P-polarized light having different colors are guided on the transmitted optical axis. Therefore, when the polarizing beam splitter of the present invention is used, P-polarized light and S-polarized light having different colors can be used without requiring a color filter or the like.

[1] Polarizing Beam Splitter FIG. 1 shows an example of the polarizing beam splitter of the present invention. This polarization beam splitter includes a trapezoidal prism 1a, 1b bonded to the bottom surfaces 10a, 10b, and a multilayer film 2 joined to the bottom surfaces 10a, 10b.

  Since the trapezoidal prisms 1a and 1b have the same shape, only the shape of the trapezoidal prism 1a will be described. As shown in FIG. 2, the trapezoidal prism 1a includes trapezoidal side surfaces 100a and 101a, horizontal bottom surface 10a and upper surface 13a, and inclined surfaces 11a and 12a. The side surface 100a and the back surface 101a shown in FIG. 1 are parallel.

  The trapezoidal prisms 1a and 1b may be made of the same material or different materials. The refractive indexes of the trapezoidal prisms 1a and 1b are not particularly limited as long as the relationship with the refractive index of the multilayer film 2 to be described later is satisfied. However, when the wavelength of incident light is 300 to 2000 nm, it is generally about 1.35 to 2.25. It is. Examples of the material of the trapezoidal prisms 1a and 1b include optical glass, transparent ceramics, and transparent plastic.

  The polarizing beam splitter is arranged so that light enters perpendicularly to the inclined surface 11a of the trapezoidal prism 1a. Part of the light L incident on the slope 11a passes through the multilayer film 2 and the trapezoidal prism 1b and exits from the slope 12b. The remaining light is reflected by the multilayer film 2 (reflection angle θ) and exits from the inclined surface 12a.

The multilayer film 2 has high refractive index layers and low refractive index layers alternately. When the high refractive index layer and the low refractive index layer are alternately stacked, an interference effect occurs at the boundary between the layers, and the transmittance of S-polarized light decreases and the transmittance of P-polarized light increases in a specific wavelength band. . The refractive indexes nS of the trapezoidal prisms 1a and 1b are larger than the refractive index nL of the low refractive index layer. Of course, since the refractive index nH of the high refractive index layer is larger than the refractive index nL of the low refractive index layer, the following formula (1)
nL <nS, nH (1)
(Where nL represents the refractive index of the low refractive index layer, nS represents the refractive index of the trapezoidal prisms 1a and 1b, and nH represents the refractive index of the high refractive index layer). Conditional expression (2) that when the refractive indexes nL and nS of the low refractive index layer and the trapezoidal prisms 1a and 1b do not satisfy the above formula (1), the reflection angle θ at the bottom surface 10a is not less than the critical angle of the low refractive index layer. Can not be satisfied.

The refractive index nH of the high refractive index layer and the refractive index nS of the trapezoidal prisms 1a and 1b are expressed by the following formula (4)
nS <nH (4)
(Where nS represents the refractive index of the trapezoidal prisms 1a and 1b, and nH represents the refractive index of the high refractive index layer). If the refractive index nH of the high refractive index layer and the refractive index nS of the trapezoidal prisms 1a and 1b are set so that the above formula (4) is satisfied, the reflectance of S-polarized light in a specific wavelength band can be increased efficiently.

Assuming that the reflection angle at the bottom surface 10a is θ, the following equation (2)
θ > sin ^-1 (nL / nS) (2)
(Where nL represents the refractive index of the low refractive index layer, nS represents the refractive index of the trapezoidal prisms 1a and 1b, and θ represents the reflection angle at the bottom surface 10a of the light L perpendicularly incident on the inclined surface 11a of the trapezoidal prism 1a. )) Is established. When the reflection angle θ is less than sin ⁻¹ (nL / nS), it is impossible to obtain a wavelength band in which the transmittance of S-polarized light is large and the transmittance of P-polarized light is small.

  The total number of layers of the high refractive index layer and the low refractive index layer is 15 or more. If the total number of layers is less than 15, the transmittance and reflectance of S-polarized light and P-polarized light are difficult to reverse at the wavelength of visible light. Each of the high refractive index layer and the low refractive index layer may be made of the same material, or may be made of different materials satisfying the above formulas (1) and (2). When the refractive index nS of the trapezoidal prisms 1a and 1b is 1.5 to 1.8, examples of the high refractive index layer include tantalum oxide layers, titanium oxide layers, lanthanum oxide layers, yttrium oxide layers, niobium oxide layers, cerium oxide layers, zirconium oxides. A layer, an ytterbium oxide layer, a hafnium oxide layer, and an aluminum oxide layer. Examples of the low refractive index layer include a silicon oxide layer, a magnesium fluoride layer, a calcium fluoride layer, and an aluminum fluoride layer.

The optical layer thickness of each high refractive index layer and low refractive index layer may be the same or different. The “optical layer thickness” of the high refractive index layer or the low refractive index layer means the optical thickness (optical film thickness) of the high refractive index layer or the low refractive index layer. However, the largest dLmax of the optical layer thickness of the low refractive index layer is expressed by the following formula (3) dLmax <λmax (3)
(However, λmax indicates the maximum value of the used wavelength λ and dLmax indicates the maximum optical layer thickness of the low refractive index layer). The utilization wavelength λ indicates the wavelength of light that is irradiated onto the polarization beam splitter and separated into each polarized light. If the maximum optical layer thickness dLmax of the low refractive index layer is not less than the maximum value λmax of the used wavelength, the incident light is totally reflected. When the utilization wavelength is 300 to 2000 nm, the optical layer thickness of the low refractive index layer is generally about 5 to 2000 nm, and the optical layer thickness of the high refractive index layer is also about 5 to 2000 nm. The optical film thickness of the multilayer film 2 is about 1 to 1000 μm.

  FIG. 3 schematically shows the spectral transmittance of the polarizing beam splitter. In FIG. 3, Ts indicates the transmittance of S-polarized light, and Tp indicates the transmittance of P-polarized light. In the first wavelength band W1, the transmittance Ts of S-polarized light is larger than the transmittance Tp of P-polarized light, and in the second wavelength band W2, the transmittance Tp of P-polarized light is larger than the transmittance Ts of S-polarized light. The boundary between the first and second wavelength bands W1 and W2 needs to be within the range of the use wavelength λ. If these boundaries are not within the range of the used wavelength λ, the reversal of the transmittance of S-polarized light and P-polarized light cannot be used. The first and second wavelength bands W1 and W2 are preferably both in the visible light region. When the first and second wavelength bands W1 and W2 are in the visible light region, S-polarized light and P-polarized light emitted from the inclined surface 12b exhibit different colors.

  For example, when the first wavelength band W1 is 400 to 600 nm and the second wavelength band W2 is 650 to 750 nm, as shown in FIG. 4, red P-polarized light Pr and green and blue S-polarized light Sg, Sb is transmitted through the multilayer film 2, and green and blue P-polarized light Pg and Pb and red S-polarized light Sr are reflected. Therefore, red P-polarized light Pr and green and blue S-polarized light Sg and Sb can be used on the optical axis orthogonal to the slope 12b, and green and blue P-polarized light Pg, on the optical axis orthogonal to the slope 12a. Pb and red S-polarized Sr can be used.

  The S-polarized light transmittance Ts in the first wavelength band W1 is preferably 80% or more, and the P-polarized light transmittance Tp in the second wavelength band W2 is preferably 80% or more. When the transmittances Ts and Tp are 80% or more, there is little loss due to reflection, and incident light can be used effectively. Further, the P-polarized light transmittance Tp in the first wavelength band W1 is preferably 20% or less, and the S-polarized light transmittance Ts in the second wavelength band W2 is preferably 20% or less. If the transmittance that is not substantially used in each of the wavelength bands W1 and W2 exceeds 20%, unnecessary polarized light is guided too much on the transmission optical axis. If the transmittance Tp of P-polarized light in the first wavelength band W1 and the transmittance Ts of S-polarized light in the second wavelength band W2 are 20% or more, these polarized lights can be used effectively on the reflected optical axis. It is.

  In the example shown in FIG. 3, the first wavelength band W1 is on the short wavelength side and the second wavelength band W2 is on the long wavelength side, but the first and second wavelength bands W1 and W2 are not limited to this. The second wavelength band W2 may be on the short wavelength side, and the first wavelength band W1 may be on the long wavelength side. In this case, S-polarized light having a longer wavelength is emitted from the inclined surface 12b, and P-polarized light having a shorter wavelength is emitted from the inclined surface 12a.

[2] Manufacturing method of polarizing beam splitter
(1) Design of multilayer film Refractive indexes nH, nL, nS and the reflection angle θ of the transparent substrate are expressed by the following equations (1) and (2)
nL <nS, nH (1)
θ > sin ^-1 (nL / nS) (2)
(Where nL represents the refractive index of the low refractive index layer, nS represents the refractive index of the transparent substrate, nH represents the refractive index of the high refractive index layer, and θ represents one transparent substrate. The reflection angle at the interface with the multilayer film of vertically incident light must be satisfied.

The number of layers (the total of the low refractive index layer and the high refractive index layer) is determined by a number of 15 or more, and the following formula (3)
dLmax <λmax (3)
(However, λmax indicates the maximum value of the used wavelength, and dLmax indicates the maximum optical layer thickness of the low refractive index layer.) And is processed by simulation software for optical thin film design. The simulation conditions are, for example, that the transmittance of S-polarized light is 80% or more and the transmittance of P-polarized light is 20% or less at a wavelength of 400 to 600 nm, and the transmittance of P-polarized light is 80% or more at a wavelength of 650 to 750 nm. And the transmittance of S-polarized light is 20% or less. The simulation software performs optimization by changing the optical layer thickness of each layer.

(2) Formation of multilayer film The method of forming the low refractive index layer and the high refractive index layer is not particularly limited, and can be produced by a general method. For example, physical vapor deposition methods such as vapor deposition, sputtering, and ion plating, and chemical vapor deposition such as thermal CVD, plasma CVD, and photo-CVD are listed. From the viewpoint of refractive index stability and film thickness controllability, sputtering and ion plating are preferred.

  When a low refractive index layer or a high refractive index layer is formed by a sputtering method or an ion plating method, a layer having a desired thickness can be formed by appropriately setting a deposition time, a heating temperature, and the like.

(3) Adhesion of transparent base material To attach the trapezoid prism 1b to the multilayer film 2 formed on one surface of the trapezoid prism 1a, (a) Apply the adhesive to the surface of the multilayer film 2 and bond the trapezoid prism 1b together. However, it is preferable to vacuum-bond (b) the multilayer film 2 and the trapezoidal prism 1b. According to the vacuum bonding, it is not necessary to use an adhesive, so that the obtained polarizing beam splitter is not affected by refraction by the adhesive.

  In order to join the multilayer film 2 and the trapezoidal prism 1b by vacuum bonding, first, the surface of the multilayer film 2 and the bottom surface 10b of the trapezoidal prism 1b are brought into contact with each other and placed in a vacuum chamber. Next, the vacuum chamber is evacuated to about 1 Pa to 1 kPa. Since the surfaces of the multilayer film 2 and the trapezoidal prism 1b are very smooth, they can be bonded by bringing them into close contact in a reduced pressure atmosphere.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1

A trapezoidal prism made of SiO _{2 as} the material of the low refractive index layer, Ta ₂ O ₅ as the material of the high refractive index layer, and the transparent substrate 1a made of optical glass S-BSL7 (made by OHARA, refractive index nd = 1.516). 48 layers of multilayer film 2 were designed with 1a and a wavelength λ of 350 to 750 nm. The shape of the trapezoidal prism 1a was the same as that shown in FIGS. 1 and 2 except that the reflection angle at the bottom surface 10a was 85 °. The structure of the multilayer film 2 is shown in Table 1. The refractive index of the low refractive index layer and the high refractive index layer of this multilayer film 2 and the refractive index of the transparent substrate clearly satisfy the above formula (1), and sin ⁻¹ (nL / nS) is 74.38 (<85). Therefore, the above equation (2) is also satisfied. Since dLmax is 351.6, the above equation (3) is also satisfied.

  A multilayer film shown in Table 1 was formed on the bottom surface 10a of the trapezoidal prism 1a.

注 但し、層No.は台形プリズム1a側からNo.１、２・・・・47、48とする。

Note However, the layer numbers are No. 1, 2, ... 47, 48 from the trapezoidal prism 1a side.

  The bottom layer 10b of the trapezoidal prism 1b having the same shape and material as the trapezoidal prism 1a is brought into contact with the 48th layer of the multilayer film 2 into the vacuum chamber, and the inside of the chamber is evacuated to bond the multilayer film and the trapezoid prism. A polarizing beam splitter was produced.

Example 2
The multilayer film 2 shown in Table 2 is formed on the bottom surface 10a of the trapezoidal prism 1a using the trapezoidal prisms 1a and 1b made of optical glass S-LAL56 (made by OHARA INC., Refractive index nd = 1.68) and θ = 65 °. A polarizing beam splitter was produced in the same manner as in Example 1 except that. The multilayer film 2 of this polarizing beam splitter also satisfied the above equations (1) to (3).

注 但し、層No.は台形プリズム1a側からNo.１、２・・・・47、48とする。

Note However, the layer numbers are No. 1, 2, ... 47, 48 from the trapezoidal prism 1a side.

Example 3
The multilayer film 2 shown in Table 3 is formed on the bottom surface 10a of the trapezoidal prism 1a using the trapezoidal prisms 1a and 1b made of optical glass S-LAH59 (made by OHARA INC., Refractive index nd = 1.82) and θ = 55 °. A polarizing beam splitter was produced in the same manner as in Example 1 except that. The multilayer film 2 of this polarizing beam splitter also satisfied the above equations (1) to (3).

注 但し、層No.は台形プリズム1a側からNo.１、２・・・・47、48とする。

Note However, the layer numbers are No. 1, 2, ... 47, 48 from the trapezoidal prism 1a side.

Example 4
The multilayer film shown in Table 4 was formed on the bottom surface 10a of the trapezoidal prism 1a using optical glass S-BSL7 (made by OHARA INC., Refractive index nd = 1.516) and using trapezoidal prisms 1a and 1b with θ = 85 °. A polarizing beam splitter was produced in the same manner as in Example 1 except that. The multilayer film 2 of this polarizing beam splitter also satisfied the above equations (1) to (3).

注 但し、層No.は台形プリズム1a側からNo.１、２・・・・16とする。

Note However, the layer number is No. 1, 2, ... 16 from the trapezoidal prism 1a side.

Comparative Example 1
The multilayer film shown in Table 5 is formed on the vertical surface 31a of the triangular prism 3a using optical prism S-LAL18 (made by OHARA INC., Refractive index nd = 1.73) and triangular prisms 3a and 3b with θ = 45 °. A polarizing beam splitter having the shape shown in FIG. 10 was produced in the same manner as in Example 1 except that. This multilayer film 4 had sin ⁻¹ (nL / nS) of 57.55 (> 45), and did not satisfy the above formula (2).

注 但し、層No.は台形プリズム1a側からNo.１、２・・・・36、37とする。

Note, however, the layer numbers are No. 1, 2, ... 36, 37 from the trapezoidal prism 1a side.

  The inclined surface 11a of Examples 1 to 4 and the vertical surface 31a of Comparative Example 1 were vertically irradiated with light having a wavelength of 350 to 750 nm, and the spectral transmittance of each polarized light was measured. The results are shown in FIGS. For simplicity, the value excluding the contribution of reflection at the interface between air and the transparent substrates 1a and 1b is shown on the vertical axis of each graph as the transmittance of the polarizing beam splitter.

  As shown in FIGS. 5 to 8, the transmittances of S-polarized light and P-polarized light in Examples 1 to 4 were reversed around a wavelength of 550 nm. For example, in Example 1, S-polarized light exhibits a transmittance of 85% or more in the wavelength range of 410 to 550 nm, whereas the transmittance of P-polarized light is less than 5%, and in the wavelength range of 580 to 740 nm. P-polarized light showed a transmittance of 80% or higher, whereas the transmittance of S-polarized light was almost 0% (FIG. 5). On the other hand, as shown in FIG. 9, in Comparative Example 1, the transmittance of P-polarized light was larger than that of S-polarized light over the entire range of the used wavelength λ.

It is a side view which shows an example of the polarizing beam splitter of this invention. It is a perspective view which shows a trapezoid prism. It is the schematic which shows the spectral transmittance of the polarizing beam splitter of this invention. It is a side view which shows the transmitted light and reflected light of a polarization beam splitter. 3 is a graph showing the spectral transmittance of each polarized light in the polarizing beam splitter of Example 1. FIG. 6 is a graph showing the spectral transmittance of each polarized light in the polarizing beam splitter of Example 2. 10 is a graph showing the spectral transmittance of each polarized light in the polarizing beam splitter of Example 3. 10 is a graph showing the spectral transmittance of each polarized light in the polarizing beam splitter of Example 4. 6 is a graph showing the spectral transmittance of each polarized light in the polarizing beam splitter of Comparative Example 1. It is the schematic which shows an example of the optical system which guide | induces the polarized light from which a color differs on the same optical axis.

Explanation of symbols

1a, 1b ... Trapezoidal prism
10a, 10b ... Bottom
11a, 12a ... Slope
13a ・ ・ ・ Top surface
100a, 101a ... Side 2 ... Multilayer film
3a, 3b ... Prism 5 ... Mirror 6 ... Color filter
S ... S-polarized light
P ... P polarized light
Ts ・ ・ ・ S-polarized light transmittance
Tp ・ ・ ・ P-polarized light transmittance

Claims (3)

A polarizing beam splitter comprising a pair of transparent substrates and a multilayer film composed of a high refractive index layer and a low refractive index layer provided between the transparent substrates, the following formulas (1), (2) and (3 )
nL <nS, nH (1)
θ > sin ^-1 (nL / nS) (2)
dLmax <λmax (3)
(Where nL represents the refractive index of the low refractive index layer, nS represents the refractive index of the transparent substrate, nH represents the refractive index of the high refractive index layer, and θ represents one transparent substrate. The angle of reflection of the perpendicularly incident light at the interface with the multilayer film, λmax indicates the maximum value of the used wavelength, and dLmax indicates the maximum optical layer thickness of the low refractive index layer. The number is 15 or more, the transmittance of S-polarized light is higher than the transmittance of P-polarized light in the first wavelength band, and the transmittance of P-polarized light is higher than the transmittance of S-polarized light in the second wavelength band. Characteristic polarization beam splitter.   2. The polarizing beam splitter according to claim 1, wherein the first and second wavelength bands are in a visible region, and in the first wavelength band, the transmittance of S-polarized light is 80% or more and transmission of P-polarized light. A polarizing beam splitter, wherein the transmittance is 20% or less, and in the second wavelength band, the transmittance of P-polarized light is 80% or more and the transmittance of S-polarized light is 20% or less. A method of manufacturing a polarizing beam splitter, wherein a multilayer film comprising a high refractive index layer and a low refractive index layer is provided on the bottom surface of a first transparent substrate, and the multilayer film is bonded to the bottom surface of a second transparent substrate, comprising: The number of layers of the film is 15 or more, and the following formulas (1), (2) and (3)
nL <nS, nH (1)
θ > sin ^-1 (nL / nS) (2)
dLmax <λmax (3)
(Where nL represents the refractive index of the low refractive index layer, nS represents the refractive index of the transparent substrate, nH represents the refractive index of the high refractive index layer, and θ represents one transparent substrate. The angle of reflection of the perpendicularly incident light at the interface with the multilayer film is shown, λmax shows the maximum value of the used wavelength, and dLmax shows the maximum optical layer thickness of the low refractive index layer. A method of manufacturing a polarizing beam splitter, characterized in that the transmittance of S-polarized light in the wavelength band is higher than the transmittance of P-polarized light, and the transmittance of P-polarized light in the second wavelength band is higher than the transmittance of S-polarized light.

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