JP2001350024A - Polarizing beam splitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing beam splitter, having little dependence on the angle of incidence of an incident luminous flux on a surface of a polarization separating multilayered film and further having a high polarization separation ratio and a wide working band width. SOLUTION: The polarizing beam splitter is provided with a dielectric multilayered film, formed on a translucent substrate 1. The dielectric multilayer film consists of a first dielectric multilayer film 3 and a second dielectric multilayered film 4, with respectively different two designed reference wavelengths λ1, λ2. The first and the second dielectric multilayered films are provided with alternating layers 13, 23 laminated in n periods (n is an arbitrary integer) or two layers comprising high refractive index materials 11, 21 and low refractive index materials 12, 22 with optical film thickness λ1/4, λ2/4 at respective reference wavelengths λ1, λ2 as fundamental periods. The alternating layer 13 of the first dielectric multilayered film and the alternating layer 23 of the second dielectric multilayer film, respectively comprising combinations of substances of mutually different kinds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing beam splitter used for separating and combining both S and P polarization components.

[0002]

[Comparison technology] Generally, a polarizing beam splitter is used in which a dielectric multilayer film in which dielectric thin films of a high refractive index material and a low refractive index material are alternately stacked is interposed between two 45 ° prisms. Have been done. The material selection of the dielectric multilayer film is 45
(4) The process is performed so that the reflectance of the P-polarized light component of the incident light entering from the optical axis of the prism is the smallest and the reflectance of the S-polarized light component is the highest.

A polarizing beam splitter converts incident light into P and S
It is used in optical disk devices, projection display devices, and the like to separate the two polarization components with high efficiency. From the comparison, various proposals have been made for a dielectric multilayer structure in order to widen the wavelength band used by the polarizing beam splitter. For example, in Japanese Patent Application Laid-Open No. 61-141402, an intermediate layer is provided in a dielectric multilayer film having a basic period of two layers of a high refractive index material and a low refractive index material, and the thickness of this layer is adjusted. Broadening the bandwidth. Further, in the configuration example of the conventional polarizing beam splitter disclosed in JP-A-3-284705, the combination of a high-refractive-index material and a low-refractive-index material is the same in two dielectric multilayer films having different design reference wavelengths. It is a combination. With this configuration, the bandwidth of the used wavelength is widened and the polarization separation ratio is improved.

[0004]

However, in a conventional polarizing beam splitter having a dielectric multilayer structure,
Although the bandwidth widens with respect to the designed incident angle, if the incident angle of the light beam shifts even a little, the P / S polarization separation ratio becomes worse,
The problem is that the bandwidth is very narrow.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polarization beam splitter which has a small incident angle dependence of a light beam incident on a polarization separation multilayer film surface, a high polarization separation ratio, and a wide use bandwidth.

[0006]

According to the present invention, there is provided a polarizing beam splitter having a dielectric multilayer film laminated on a light-transmitting substrate, wherein the dielectric multilayer film has two different designs. First having reference wavelengths λ1, λ2
And a second dielectric multilayer film and a first dielectric multilayer film.
And the second dielectric multilayer film has respective reference wavelengths λ1,
an alternating layer in which two layers composed of a high-refractive-index substance and a low-refractive-index substance having an optical thickness of λ1 / 4 and λ2 / 4 at λ2 are stacked for n periods (n is an arbitrary integer) as a basic period; A thin film adjusting layer made of one of the high-refractive-index substance and the low-refractive-index substance having an optical film thickness of λ1 / 8 or λ2 / 8 on both sides of the alternating layer; Layer and second
Characterized in that the alternate layers of the dielectric multilayer film are formed of a combination of different kinds of substances.

[0007]

The polarizing beam splitter according to the present invention has a structure and a structure in which the bandwidth of the used wavelength region is not narrowed even if the incident angle of the light beam on the dielectric multilayer film is slightly changed. The substance used for the high refractive index layer and the low refractive index layer is selected. In order to perform polarization separation over a wide band, it is necessary to increase the wavelength band separating the P-polarized component and the S-polarized component from the wavelength of the light beam incident on the polarization separation film. For this purpose, according to Snell's law, the vicinity of the Brewster angle at which the polarization separation between the P-polarized light component and the S-polarized light component is the largest is set as the design incident angle so that the light enters the polarization separation film.

The structure of the dielectric multilayer film of the present invention has first and second dielectric multilayer films having different design reference wavelengths. The angle of incidence of the light beam incident on each of the first and second dielectric multilayer films is set to be different. The high refractive index and low refractive index substances of the first and second dielectric multilayer films were selected so that the following Brewster conditions (1) and (2) were different. For example, a combination of TiO ₂ and SiO ₂ as a high-refractive-index material is used for the alternate layers of one dielectric multilayer film, and TiO _{2 is} used as a high-refractive-index material for the alternate layers of the other dielectric multilayer film. Alternatively, a combination in which Al ₂ O ₃ is used as the low refractive index substance may be used.

The design reference wavelengths λ 1 and λ 2 (λ 1 ≠ λ 2) and the design reference incident angle θ are defined as incident angles θ 1 and θ 2 respectively. The Brewster condition in each case is given by the following equation (1).
It is represented by (2). λ1> λ2 λ1, θ1; nH1COSθH1 = nL1COSθL1 (1) λ2, θ2; nH2COSθH2 = nL2COSθL2 (2) θ1; Angles θ2; angles nH1, nL1 incident on the boundary surface between the second dielectric multilayer film and the light-transmitting substrate 2 from the light-transmitting substrate 2; alternation of the first dielectric multilayer film at the design reference wavelength λ1 NH2, nL2; refractive indices of high refractive index layer and low refractive index layer in alternate layers of second dielectric multilayer film at design reference wavelength λ2, θH1, θL1 The angles θH2, θL2 incident on the interface from each of the high refractive index layer and the low refractive index layer in the alternating layers of the first dielectric multilayer film at the design reference wavelength λ1; In the alternating layers of the dielectric multilayer film, light is incident on the interface from each of the high refractive index layer and the low refractive index layer. FIG. 3 is a diagram illustrating a state in which a light beam incident on the dielectric multilayer film is incident on a boundary surface from a high refractive index layer and a low refractive index layer. In the figure, θi, θHi, and θLi correspond to the first and second dielectric multilayer films i = 1 and 2, respectively.

The thicknesses of the high refractive index layer, low refractive index layer, and adjustment layer used in the alternating layers of the dielectric multilayer film of the present invention are λ / 4, λ / 4, and λ / 8, respectively. However, the actually formed film thickness is determined experimentally through trial and error, and may slightly deviate from the designed value. Further, the adjustment layer of the present invention is provided to reduce a ripple generated in the transmittance of the P-polarized light component. If there is a large ripple, the wavelength range that can be used as the polarizing beam splitter is limited, which is not preferable.

For comparison with the embodiment of the present invention, the configuration of the polarizing beam splitter is basically the same as that of FIG. 1, and the high refractive index layer Ti used for the alternating layers of the first and second dielectric multilayer films is used.
The transmittance characteristics in which the combination of the substance of O ₂ and the low refractive index layer SiO ₂ is the same are examined. FIG. 10 shows the incident angle dependence of the transmittance characteristics.

At a design standard incident angle of 45 °, a band having a high P / S polarization separation ratio is 160 nm, but the incident angle is ± 2.5.
If shifted, the bandwidth becomes 90 nm. A polarizing beam splitter using a dielectric multilayer film composed of only one type can obtain a wide usable wavelength range in which the S and P polarization components can be separated. However, even if the angle of incidence on the surface of the dielectric multilayer film is slightly shifted, the desired wavelength bandwidth becomes very narrow.

On the other hand, the working bandwidth of the embodiment of the present invention is very high while maintaining the separation ratio between the P-polarized component and the S-polarized component even if the angle of incidence of the light beam on the dielectric multilayer film surface is slightly shifted. Become wider. Further, the degree of freedom in the arrangement of the optical system incorporating the polarizing beam splitter is increased.

Next, a method of forming a dielectric multilayer film of the polarizing beam splitter of the present invention will be described. FIG. 1 shows that first and second dielectric multilayer films 3 and 4 of the present invention are formed on a prism 1 which is a translucent substrate, and each of them is bonded via an adhesive layer 5. Configuration.

FIG. 8 shows that a first dielectric multilayer film and a second dielectric multilayer film are continuously formed on a transparent substrate 1. Further, the light-transmissive substrate 12 is bonded thereon. In FIG. 9, the same performance can be obtained even when the transparent substrate is formed by applying a dielectric multilayer film on both surfaces of the flat glass 1 and immersing it in a liquid medium 6 having a refractive index similar to that of glass.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the polarizing beam splitter according to the present invention will be described. FIG. 1 shows a prism 1 in which an adjustment layer 1C and an alternating layer 13 of a first dielectric multilayer film 3 are stacked, and an adjustment layer 2C and an alternating layer 23 of a second dielectric multilayer film 4 stacked. This is a configuration of a polarization beam splitter in which a prism 2 and an optical adhesive 5 are joined. The prisms 1 and 2 have a refractive index nS of 1.84. The refractive index nb of the optical adhesive is 1.52. The drawing shows the reflected light R and the transmitted light T when the light beam is incident at 45 °. The transmitted light T has an S-polarized component TS and a P-polarized component TP.

The alternating layer 13 of the first dielectric multilayer film has a design reference wavelength λ1 = 680 nm and a high refractive index substance nH1 = 2.3.
8 of TiO ₂ 11 and low refractive index substance nL1 = 1.65 of Al ₂
O ₃ 12 has an optical thickness of λ1 / 4. Second
The alternate layer 23 of the dielectric multilayer film of the design reference wavelength λ2 = 4
TiO ₂ 21 with high refractive index material nH 2 = 2.38 at 20 nm
And the SiO ₂ 22 having a low refractive index material nL2 = 1.47 is constituted by an optical film thickness .lambda.2 / 4, respectively. Adjustment layers having a film thickness of λ1 / 8 and λ2 / 8 are provided between the alternating layers of the first and second dielectric multilayer films and the prisms 1 and 2, respectively.

Consider a case where the light beam has an incident angle deviated by ± 2.5 ° from a design reference incident angle of 45 °. The high-refractive-index material 11 and the low-refractive-index material 12 used in the alternating layers 13 of the first dielectric multilayer film corresponding to the high angle side (corresponding to the short wavelength side in the used wavelength range) transmit light. Θ1 from the transparent substrate 1 to the interface between the light-transmitting substrate 1 and the first dielectric multilayer film
47.5 ° so as to satisfy the Brewster condition (1). In this embodiment, as the material combination of the alternating layers of the first dielectric multilayer film, Ti
O ₂ and Al ₂ O ₃ were selected for the low refractive index layer 12.

The high refractive index substance 21 and the low refractive index substance 22 used for the alternating layers 23 of the second dielectric multilayer film corresponding to the low angle side (corresponding to the long wavelength side in the used wavelength region)
The angle is selected so that the Brewster condition (2) is satisfied at an angle θ2 = 42.5 ° at which a light beam enters the interface between the light-transmitting substrate 2 and the second dielectric multilayer film from the light-transmitting substrate 2. In this embodiment, as the substance a combination of alternating layers of the second dielectric multilayer film, TiO ₂ in the high refractive index layer 21, was chosen SiO ₂ for the low refractive index layer 22.

FIG. 4 shows the transmittance characteristics Tp and TS of the P and S polarization components of the dielectric multilayer structure of the first embodiment and the incident angle 4.
These are transmittance characteristics of 2.5 °, 45 °, and 47.5 °. The dependence of the transmittance of the P and S polarization components of the polarizing beam splitter having the dielectric multilayer structure of the first embodiment of the present invention on the incident angle will be compared with the comparative example of FIG.

The multilayer structure of the comparative example has a wavelength range of 480.
When the incident angle deviates from the design reference angle by several degrees from 550 nm to 550 nm, the bandwidth X becomes 70 nm, and the used band becomes very narrow. In contrast, the first embodiment of the present invention covers a wavelength range of 460 nm to 620 nm,
It shows a high polarization separation (TS / TP) of 0.1% or less.
The bandwidth X is 1 even if it deviates from the design standard incidence angle by ± 2.5 °.
A wide band of 60 nm is maintained.

FIG. 5 is a diagram showing the wavelength λ on the long wavelength side according to the first embodiment of the present invention.
4 shows the incident angle dependence of the transmittance of the P-polarized light component at 620 nm. The present embodiment is different from the comparative example of FIG. 10 in which the combination of each of the alternating layers of the first dielectric multilayer film and the alternating layers of the second dielectric multilayer film uses the same kind of substances TiO ₂ and SiO ₂ . The bandwidth of the transmittance characteristics could be greatly expanded even if the incident angle dependence was taken into consideration.

This is because the alternating layers of the first dielectric multilayer film, which cause the drop in the P-polarized light transmittance on the long wavelength side,
The Brewster condition (1) is satisfied at 7.5 °, and the Brewster condition (2) is satisfied at 42.5 ° for the alternate layer of the second dielectric multilayer film which causes a decrease in the short wavelength side. This is because the film material of each dielectric multilayer film is selected so that

As described above, by using the polarizing beam splitter having the configuration of the present invention, it is possible to greatly widen the wavelength band to be used as compared with the conventional example, and to obtain a polarizing beam splitter having a high degree of freedom with respect to the incident angle of light. Was completed. Next, a second embodiment of the present invention will be described.

The structure of the dielectric multilayer film of the second embodiment is the same as that of the first embodiment.
This embodiment is basically the same as the above-described embodiment, except that the combination of substances used for the dielectric multilayer film is different. The configuration is the adjustment layer 1C
And a translucent substrate in which the alternating layer 13 of the first dielectric multilayer film 3 is laminated, and a translucent substrate in which the adjusting layer 2C and the alternating layer 23 of the second dielectric multilayer film 4 are laminated. 2 is a configuration of the polarization beam splitter joined by the optical adhesive 5. The translucent substrate 1 and the translucent substrate 2 have a refractive index nS of 1.52.

The alternating layers of the first dielectric multilayer film is a design wavelength .lambda.1 = 700 nm, is a TiO ₂ of high refractive index material NH1 = 2.38 and SiO ₂ with a low refractive index material n1 = 1.47 It has an optical thickness of λ1 / 4. The alternate layers of the second dielectric multilayer film are composed of ZrO ₂ having a high refractive index material nH2 = 2.02 and a low refractive index material nL2 = at a design reference wavelength λ2 = 430 nm.
1.37 MgF ₂ are each formed with an optical film thickness of λ2 / 4. Further, between each of the alternating layers of the first and second dielectric multilayer films and the prisms 1 and 2, a film thickness λ1 is provided.
/ 8 and λ2 / 8 adjustment layers are provided.

When the light flux is shifted by ± 4 ° in the vicinity of the design reference incident angle of 52 °, the alternating layers of the first dielectric multilayer film corresponding to the higher angle side (corresponding to the shorter wavelength side in the used wavelength range). Are selected so as to satisfy the Brewster condition (1) at an incident angle of 56 ° with respect to the normal to the film surface of the light beam. The material combination of the first dielectric multilayer film of the present embodiment is such that the high refractive index layer 11 is made of Ti.
O ₂ and SiO ₂ were selected for the low refractive index layer 12.

The high-refractive index material and the low-refractive index material used for the alternating layers of the second dielectric multilayer film corresponding to the low angle side (corresponding to the long wavelength side in the used wavelength region) receive a light beam. An angle of 48 ° is selected so as to satisfy the Brewster condition (2). The material combination of the second dielectric multilayer film of the present embodiment is such that ZrO ₂ is used for the high refractive index layer 21 and M
the gF ₂ was selected.

FIG. 6 shows the transmittance characteristics of P and S polarized light components and the incident angles 48 ° and 52 ° of the first embodiment of the dielectric multilayer structure.
{, 56} are transmittance characteristics. The incident angle dependence of the transmittance of the P and S polarization components of the polarization beam splitter having the dielectric multilayer structure of the second embodiment of the present invention will be compared with the comparative example of FIG.

The multilayer structure of the comparative example has a wavelength range of 480.
When the incident angle deviates from the design reference angle by several degrees from 550 nm to 550 nm, the bandwidth becomes 70 nm, and the used band becomes very narrow. In contrast, the second embodiment of the present invention covers a wavelength range of 460 nm to 620 nm,
This shows high polarization separation between the polarization component and the P polarization component.
Even if it deviates from the design standard incident angle by ± 4 °, the bandwidth X is 170
It maintains a wide band of nm.

As described above, according to the embodiment of the present invention, the alternating layers of the first dielectric multilayer film and the alternating layers of the second dielectric multilayer film are of the same type of material combination, ie, TiO ₂ and SiO _2. As compared with the comparative example using (1) and (2), the bandwidth of the transmittance characteristics could be greatly expanded even when the incident angle dependency was taken into consideration.

This is due to the fact that the P-polarized light transmittance on the long wavelength side is reduced by 5% in the alternate layers of the first dielectric multilayer film.
6 ° satisfies the Brewster condition (1), and the alternate dielectric layer of the second dielectric multilayer film which causes the short-wavelength drop has a dielectric material which satisfies the Brewster condition (2) at 48 °. This is because the film material of the multilayer film is selected.

As described above, by making the design reference wavelength of each of the first dielectric multilayer film and the second dielectric multilayer film different and the combination of the low refractive index material and the high refractive index material,
It is possible to obtain a high-bandwidth polarization beam splitter having a high degree of freedom with respect to the incident angle and a high polarization separation ratio S / P.

FIGS. 7 and 8 show a third embodiment. The present embodiment is a modified example regarding the arrangement of the polarization beam splitter of the present invention. A first dielectric multilayer film 3 and a second dielectric multilayer film 4 are continuously laminated on a light-transmitting substrate 1, and the light-transmitting substrate 2 is formed via an adhesive layer 5.

According to this configuration, there is an advantage that the formation of the low refractive index layer and the high refractive index layer can be performed in one batch. FIG. 9 shows a fourth embodiment of the polarization beam splitter according to the present invention. The polarizing beam splitter of this embodiment uses a transparent flat substrate 1 as a light-transmitting substrate, and includes a first and a second dielectric multilayer film filled with a liquid medium 6 having substantially the same refractive index as the flat substrate. It is configured. The first dielectric multilayer film 3 and the second
Are disposed on both sides of the transparent flat substrate. Examples of the liquid medium include ethylene glycol (refractive index: 1.43) and benzene (refractive index: 1.51).

In general, when a prism is used as a light-transmitting substrate, birefringence occurs due to non-uniformity of the material in the prism. It is known that when a light beam passes through a substrate, the state of polarization changes and linear polarization characteristics deteriorate. In such a case, the problem of birefringence of the light-transmitting substrate can be avoided by the structure using the liquid medium.

With the polarization beam splitter having the configuration and arrangement as in the third embodiment, the formation of the dielectric multilayer film is completed in one batch, and an improvement in productivity can be expected. In the polarization beam splitter having the configuration and arrangement of the fourth embodiment, cost reduction can be expected because an expensive prism is not required.

[0038]

As described above, according to the polarizing beam splitter of the present invention, the combination of the low refractive index material and the high refractive index material and the first and second dielectric multilayer films having different design reference wavelengths are provided. By using the above configuration, the degree of freedom with respect to the incident angle is high, and the S-polarized component and the P-polarized component can be separated or synthesized in a wide wavelength range.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a polarization beam splitter of the present invention.

FIG. 2 is a configuration sectional view of first and second dielectric multilayer films of the present invention.

FIG. 3 is an explanatory diagram of a state of a light beam incident on a dielectric multilayer structure of the present invention.

FIG. 4 is a transmittance characteristic diagram of a dielectric multilayer structure according to the first embodiment of the present invention.

FIG. 5 is a graph showing the incident angle dependence of the transmittance characteristic of the dielectric multilayer structure according to the first embodiment of the present invention.

FIG. 6 is a transmittance characteristic diagram of a P-polarized light component of a dielectric multilayer structure according to a second embodiment of the present invention.

FIG. 7 is a configuration sectional view of a polarization beam splitter according to a third embodiment of the present invention.

FIG. 8 is a sectional view showing the configuration of first and second dielectric multilayer films according to a third embodiment of the present invention.

FIG. 9 is a configuration sectional view of a polarization beam splitter according to a fourth embodiment of the present invention.

FIG. 10 is a diagram illustrating a comparison of transmittance characteristics based on the configuration of a conventional polarization beam splitter.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 first light-transmitting substrate (prism) 2 second light-transmitting substrate (prism) 3 first dielectric multilayer film 4 second dielectric multilayer film 5 adhesive layer 6 liquid medium 11 optical film thickness High refractive index substance of λ1 / 4 12 Low refractive index substance of λ1 / 4 optical thickness 13 Alternate layer 1C composed of high refractive index substance and low refractive index substance of optical thickness λ1 / 4 respectively Adjusting layer having a thickness of λ1 / 8 21 High refractive index substance having an optical thickness of λ2 / 4 22 Low refractive index substance having an optical thickness of λ2 / 4 23 High refraction having an optical thickness of λ2 / 4 Layer composed of a high-refractive-index substance and a low-refractive-index substance 2C An adjustment layer having an optical film thickness of λ2 / 8

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[Procedure amendment]

[Submission date] April 17, 2001 (2001.4.1
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, there is provided a polarizing beam splitter having dielectric multilayer films 3 and 4 formed on light-transmitting substrates 1 and 2, respectively. A first dielectric multilayer film 3 composed of alternating layers of a first high refractive index material and a first low refractive index material having λ1 as a design reference wavelength; λ1
A second dielectric multilayer film 4 composed of alternating layers of a second high-refractive-index substance and a second low-refractive-index substance having a reference wavelength of λ2 different from the first dielectric substance. The alternate layers of the multilayer film 3 and the alternate layers of the second dielectric multilayer film 4 are made of a combination of different kinds of substances. According to a second aspect of the present invention, in the polarization beam splitter according to the first aspect, the alternating layers of the first dielectric multilayer film 3 are formed of a first high refractive index material having an optical film thickness of λ1 / 4 and an optical layer. N layers (n is an arbitrary integer) with two layers composed of a first low-refractive-index substance having a target film thickness of λ1 / 4 as a basic period, and the second dielectric multilayer film is alternately formed. The layer has a basic period of two layers composed of a second high refractive index material having an optical thickness of λ2 / 4 and a second low refractive index material having an optical thickness of λ2 / 4. Period (n is an arbitrary integer) is assumed to be laminated. According to a third aspect of the present invention, in the polarization beam splitter of the first aspect, the first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material. Is composed of a combination of at least three or more types of substances. According to a fourth aspect of the present invention, in the polarization beam splitter according to the third aspect, one of the first high refractive index material and the first low refractive index material is formed of the first material, and the other is formed of the second material. One of the second high-refractive-index substance and the second low-refractive-index substance is composed of the first substance, and the other is composed of the third substance, and is composed of the first substance and the second substance. The polarizing beam splitter, wherein the substance and the third substance are different kinds of substances. According to a fifth aspect of the present invention, in the polarization beam splitter according to the third aspect, one of the first high refractive index material and the first low refractive index material is the first high refractive index material.
And the other is composed of a second substance, the second
One of the high-refractive-index substance and the second low-refractive-index substance is composed of a third substance, and the other is composed of a fourth substance. The first substance, the second substance, the third substance, And the fourth substance is a different kind of substance.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

The design reference wavelengths λ 1 and λ 2 (λ 1 ≠ λ 2) and the design reference incident angle θ are defined as incident angles θ 1 and θ 2 respectively. The Brewster condition in each case is given by the following equation (1).
It is represented by (2). λ1> λ2 λ1, θ1: nH1 / COSθH1 = nL1 / COSθL1 (1) λ2, θ2: nH2 / COSθH2 = nL2 / COSθL2 (2) θ1: From the light-transmitting substrate 1 to the first dielectric multilayer film and light-transmitting Angle θ2 incident on the boundary surface with the base 1 θ2: Angle incident on the boundary surface between the second dielectric multilayer film and the light-transmitting substrate 2 from the light-transmitting substrate 2 nH1, nL1: The angle at the design reference wavelength λ1 The refractive indices nH2 and nL2 of the high refractive index layer and the low refractive index layer in the alternating layers of the first dielectric multilayer film nH2, nL2: the high refractive index layers and the low refractive index in the alternating layers of the second dielectric multilayer film at the design reference wavelength λ2 Refractive indices θH1 and θL1: Angles of incidence of the high refractive index layer and low refractive index layer on each of the alternating layers of the first dielectric multilayer film at the design reference wavelength λ1 from the respective layers θH2 and θL2: design In the alternate layers of the second dielectric multilayer film at the reference wavelength λ2, the interface between the high refractive index layer and the low refractive index layer FIG. 3 is a diagram illustrating a state in which a light beam incident on the dielectric multilayer film is incident on a boundary surface from a high refractive index layer and a low refractive index layer. In the figure, θi, θHi, and θLi correspond to the first and second dielectric multilayer films i = 1 and 2, respectively.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

The thicknesses of the high refractive index layer, low refractive index layer, and adjustment layer used in the alternating layers of the dielectric multilayer film of the present invention are preferably λ / 4, λ / 4, and λ / 8, respectively. However, the actually formed film thickness is determined experimentally through trial and error, and may slightly deviate from the designed value. The adjustment layer is provided to reduce a ripple generated in the transmittance of the P-polarized light component. If there is a large ripple, the wavelength range that can be used as the polarizing beam splitter is limited, which is not preferable.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

FIG. 8 shows that a first dielectric multilayer film and a second dielectric multilayer film are continuously formed on a transparent substrate 1. Further, the light-transmissive substrate 12 is bonded thereon. In FIG. 9, the same performance can be obtained even when the transparent substrate is formed by applying a dielectric multilayer film on both surfaces of the flat glass 2 and immersing it in a liquid medium 6 having a refractive index similar to that of the glass.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

FIG. 6 shows transmittance characteristics of P and S polarization components and incident angles of 48 ° and 52 ° in the second embodiment of the dielectric multilayer structure.
{, 56} are transmittance characteristics. The incident angle dependence of the transmittance of the P and S polarization components of the polarization beam splitter having the dielectric multilayer structure of the second embodiment of the present invention will be compared with the comparative example of FIG.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

According to this configuration, there is an advantage that the formation of the low refractive index layer and the high refractive index layer can be performed in one batch. FIG. 9 shows a fourth embodiment of the polarization beam splitter according to the present invention. The polarizing beam splitter of this embodiment uses a transparent flat base 2 as a light-transmitting base, and includes a first and a second dielectric multilayer film filled with a liquid medium 6 having substantially the same refractive index as the flat base. It is configured. The first dielectric multilayer film 3 and the second
Are disposed on both sides of the transparent flat substrate. Examples of the liquid medium include ethylene glycol (refractive index: 1.43) and benzene (refractive index: 1.51).

Claims (4)

[Claims] 1. A polarizing beam splitter having a dielectric multilayer film formed on a transparent substrate, wherein the dielectric multilayer film has two different design reference wavelengths λ1, λ2.
A first dielectric multilayer film and a second dielectric multilayer film having the following formulae, wherein the first and second dielectric multilayer films have respective reference wavelengths λ
An alternating layer in which two layers composed of a high-refractive-index substance and a low-refractive-index substance having an optical thickness of λ1 / 4 and λ2 / 4 at 1 and λ2 are stacked for n periods (n is an arbitrary integer) as a basic period; A thin film adjusting layer formed of one of the high-refractive-index material and the low-refractive-index material having an optical thickness of λ1 / 8 or λ2 / 8 formed on both sides of the alternating layer; A polarizing beam splitter, wherein the alternating layers of the body multilayer film and the alternating layers of the second dielectric multilayer film are formed of a combination of different kinds of substances. 2. A high-refractive-index material TiO ₂ and a low-refractive-index material SiO ₂ in alternating layers of the first dielectric multilayer film, and a high-refractive-index material TiO _{2 in} alternating layers of the second dielectric multilayer film. _2. The polarization beam splitter according to claim 1, wherein the polarization beam splitter is a combination using a low refractive index material Al ₂ O ₃ . 3. A high-refractive-index material TiO ₂ and a low-refractive-index material SiO ₂ in alternating layers of the first dielectric multilayer film, and a high-refractive-index material ZrO _{2 in} alternating layers of the second dielectric multilayer film. _2. The polarization beam splitter according to claim 1, wherein the polarization beam splitter is a combination using a low refractive index material MgF2. 4. The polarization beam splitter according to claim 1, wherein said first and second dielectric multilayer films are filled with a liquid medium having a refractive index substantially the same as that of the light-transmitting substrate. .