JP2020046525A - Polarization beam splitter - Google Patents

Abstract

To provide a polarization beam splitter that does not require alignment adjustment between a plurality of polarization beam splitters for aligning optical axes and can achieve high extinction ratio.SOLUTION: A polarization beam splitter 10 composed of a plurality of optical members (21-25) bonded to each other comprises: an incident surface 11 receiving incident light 6 from a certain direction; a first polarization separation film 31 provided on an optical path of the light incident from the incident surface 11; a first emission surface 12 emitting P-polarized light transmitting through the first polarization separation film 31; a fourth polarization separation film 34 reflecting S-polarized light reflected on the first polarization separation film 31; a second polarization separation film 32 provided on an optical path of the S-polarized light reflected by the fourth polarization separation film 34; and a second emission surface 13 emitting S-polarized light reflected by the second polarization separation film 32. Triple polarization separation provides S-polarized light with a high extinction ratio.SELECTED DRAWING: Figure 8

Description

  The present disclosure relates to a polarization beam splitter that achieves a high extinction ratio by performing polarization separation by a plurality of polarization separation films.

  2. Description of the Related Art As a polarization beam splitter used in a projection display device, a polarization separation film type beam splitter including two prisms and a polarization separation film provided between the two prisms is known (for example, Patent Documents 1 and 2). ). Also, a total reflection type polarization beam splitter utilizing two total reflection conditions of different birefringent materials is known (for example, Patent Documents 3 and 4).

JP-A-11-258422 JP-A-9-54213 JP-A-9-90111 JP 2013-15687 A

  A conventional polarization splitting film type beam splitter can increase the reflectance of S-polarized light by stacking several tens of polarization splitting films. However, even if dozens of polarization separation films are stacked, the extinction ratio can generally be increased only to about 30 dB. In the polarization beam splitter described in Patent Document 1, the reflectance of P-polarized light is 0.04%, and the extinction ratio of S-polarized light (the ratio of the intensity of S-polarized light to P-polarized light) is about 35 dB. The polarization beam splitter described in Patent Document 2 can realize a high extinction ratio by arranging a plurality of polarization separation film type polarization beam splitters. However, in this polarization beam splitter, since the range of the incident angle at which a high extinction ratio can be realized is narrow, it is difficult to adjust the alignment (array) of each polarization separation film type polarization beam splitter for aligning the optical axes.

  On the other hand, the conventional total reflection type polarization beam splitter can realize a high extinction ratio of 50 dB or more by using total reflection. However, the polarization separation angle generally does not reach 90 degrees (see Patent Document 3). The total reflection type polarization beam splitter described in Patent Document 4 realizes an extinction ratio of 50 dB or more and a polarization separation angle of 90 degrees by sandwiching a birefringent plate made of a different material between two prism materials having birefringence. ing. However, this total reflection type polarizing beam splitter cannot be applied to light in the ultraviolet wavelength region due to the light absorption of the material.

  In view of such a background, an object of the present invention is to provide a polarization beam splitter that can realize a high extinction ratio without having to adjust alignment between a plurality of polarization beam splitters in order to align optical axes.

  In order to solve such a problem, an embodiment of the present invention relates to a polarizing beam splitter (10) formed by joining a plurality of optical members (21 to 25), wherein incident light (6) is incident from a predetermined direction. An incident surface (11) through which light is incident, a first polarization separation film (31) provided in an optical path of light incident from the incident surface (11), and P-polarized light transmitted through the first polarization separation film (31). A first emission surface (12) for emitting the light of the first order, a reflection surface (14, 34) for reflecting the S-polarized light reflected by the first polarization separation film (31), and the reflection surface (14, 34). A second polarization splitting film (32) provided in the optical path of the S-polarized light reflected by the second polarization splitting film (32), and a second emission surface (13) for emitting the S-polarized light reflected by the second polarization splitting film (32). ).

  Light incident on the polarization beam splitter from the incident surface is separated by the first polarization separation film into P-polarized light transmitted through the first polarization separation film and S-polarized light reflected by the first polarization separation film. . Here, the light transmitted through the first polarization splitting film is, to be precise, a transmitted light containing a large amount of P-polarized light components, but may be simply referred to as “P-polarized light” in this specification. Similarly, the light reflected by the first polarization splitting film is reflected light containing a large amount of S-polarized components, but may be simply referred to as “S-polarized light” in this specification.

  In a polarization beam splitter using attenuated total internal reflection (Frustrated Total Internal Reflection), light transmitted through the polarization separation film can be S-polarized light, and reflected light can be P-polarized light. For example, see the following document (L. Li and JA Dobrowolski, "High-performance thin-film polarizing beam splitter operating at angles greater than the critical angle", Appl. Opt. 39, 2754-2771 (2000)). . In this specification, light transmitted through the polarization separation films 31 to 35 refers to “P-polarized light”, but when attenuated total reflection is used, light transmitted through the polarization separation films 31 to 35 is “S-polarized light”. Light (the oscillating electric field vibrates perpendicularly to the plane of incidence). " Further, in this specification, light reflected by the polarization separation films 31 to 35 refers to “S-polarized light”, but when attenuated total reflection is used, light reflected by the polarization separation films 31 to 35 is “P-polarized light”. (The oscillating electric field oscillates in the plane of incidence) ".

  Since it is difficult for S-polarized light to be mixed with P-polarized light transmitted through the first polarization separation film, the extinction ratio of P-polarized light emitted from the first emission surface (the ratio of P-polarized light intensity to S-polarized light) is relatively high. Get higher. On the other hand, since the P-polarized light is easily mixed with the S-polarized light reflected by the first polarized light separating film, the extinction ratio (the ratio of the light intensity of the S-polarized light to the P-polarized light) reflected by the first polarized light separating film is compared. Target lower. The S-polarized light is reflected by the reflection surface and then further reflected by the second polarization separation film. That is, the light incident on the polarization beam splitter is double-polarized and separated by the first and second polarization separation films. Therefore, the extinction ratio of S-polarized light emitted from the second emission surface also increases. Also, since polarization can be separated by one polarization beam splitter formed by joining a plurality of optical members, high optical axis accuracy can be realized in accordance with the processing accuracy of the optical members. There is no need to adjust the alignment.

  In one embodiment of the present invention, in the above configuration, the first polarization separation film (31) and the second polarization separation film (32) are provided on the same plane.

  In one embodiment of the present invention, in the above configuration, the third polarization separation film is provided in the optical path of the P-polarized light transmitted through the first polarization separation film (31) in parallel with the first polarization separation film (31). It further comprises a membrane (33).

  In one embodiment of the present invention, in the above configuration, the plurality of optical members (21 to 25) have a trapezoidal first optical member (21) and a lower portion under the first optical member (21) in a side view. A second optical member (22) having a rectangular shape having a long side joined to the bottom, and a third trapezoid having a lower base joined to a side opposite to the long side of the second optical member (22). An optical member (23), wherein the incident surface (11) and the second emission surface (13) are provided on a side of the first optical member (21), and the first polarization separation film (31) and The second polarization separation film (32) is provided at an interface between the first optical member (21) and the second optical member (22), and the first emission surface (12) is on the side of the third optical member. It is provided on one of the sides. Here, “side” means a trapezoidal leg (a pair of opposite sides).

  In one aspect of the present invention, in the above-described configuration, the plurality of optical members (21 to 25) are trapezoidal in a side view, and a lower bottom of the first optical member (21). A second optical member (22) having a rectangular shape having one side parallel to the one side and the opposite side parallel to the one side, and a triangle having a hypotenuse joined to the opposite side of the second optical member (22). A third optical member (23), the incident surface (11) and the second exit surface (13) are provided on a side of the first optical member (21), and the first polarization separation film ( 31) and the second polarization splitting film (32) are provided at the interface between the first optical member (21) and the second optical member (22), and the first emission surface (12) is provided on the third optical member (12). The member (23) is provided on a side different from the oblique side.

  In one embodiment of the present invention, in the above configuration, the reflection surface is a total reflection surface (14).

  In one embodiment of the present invention, in the above-described configuration, the reflection surface includes a fourth polarization separation film (34) provided between a bonding surface of two optical members (21, 24) adjacent to each other.

  In one embodiment of the present invention, in the above-described configuration, a light absorbing member provided on an optical path of the P-polarized residual light reflected by the reflection surface (14, 34) and transmitted through the second polarization separation film (32). (43) is further provided.

  In one embodiment of the present invention, the antireflection film (41) or the light absorbing member (43) provided on the optical path of the residual light of the P-polarized light transmitted through the fourth polarization separation film (34) is further provided. Prepare.

  In one embodiment of the present invention, in the above configuration, the optical axis of the P-polarized light emitted from the first emission surface (12) and the optical axis of the S-polarized light emitted from the second emission surface (13) are arranged. The resulting polarization separation angle is 90 °.

  In one embodiment of the present invention, in the above structure, the first polarization separation film and the second polarization separation film include at least one material selected from the group consisting of a fluoride, an oxide, a sulfide, and a semiconductor.

  In one embodiment of the present invention, in the above structure, the plurality of optical members (21 to 25) include at least one material selected from the group consisting of an optical crystal, an optical glass, a ceramic, and a semiconductor.

  In one embodiment of the present invention, in the above configuration, the two optical members (21 to 25) adjacent to each other are joined to each other by any one of optical contact, surface activation joining, diffusion joining, and joining with an adhesive. .

  As described above, according to the present invention, it is not necessary to adjust the alignment between a plurality of polarizing beam splitters to align the optical axes, and it is possible to provide a polarizing beam splitter that can realize a high extinction ratio.

Schematic configuration diagram of a polarization separation device according to the first embodiment Side view of the polarizing beam splitter shown in FIG. Graph showing light transmission characteristics of a polarization separation film Schematic configuration diagram of a polarization beam splitter according to a second embodiment Illustration of the principle of stray light generation Schematic configuration diagram of a polarization beam splitter according to a third embodiment Schematic configuration diagram of a polarization beam splitter according to a fourth embodiment Schematic configuration diagram of a polarization beam splitter according to a fifth embodiment Schematic configuration diagram of a polarization beam splitter according to a sixth embodiment Schematic configuration diagram of a polarization beam splitter according to a seventh embodiment Schematic configuration diagram of a polarization beam splitter according to an eighth embodiment Schematic configuration diagram of a polarization beam splitter according to a ninth embodiment

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<< 1st Embodiment >>
First, a polarization separation device 1 according to a first embodiment will be described with reference to FIGS. FIG. 1 is a front view showing a schematic configuration of the polarization beam splitter 1 according to the first embodiment, and FIG. 2 is a side view of the polarization beam splitter 10 shown in FIG. As shown in FIGS. 1 and 2, a polarization separation device 1 according to the embodiment includes a light source 5 and a polarization beam splitter 10 that splits light emitted from the light source 5 into P-polarized light and S-polarized light. And

  The light source 5 may be a laser device that emits a laser beam having a predetermined wavelength in an ultraviolet wavelength range to an infrared wavelength range. In the present embodiment, the light source 5 oscillates a laser beam having a wavelength of 532 nm and irradiates the polarized beam splitter 10 as incident light 6.

  The polarization beam splitter 10 has an incident surface 11 on which light emitted from the light source 5 is incident as incident light 6, and is arranged in an optical path of the incident light 6 so that an optical axis of the incident light 6 is orthogonal to the incident surface 11. Is done. The polarization beam splitter 10 has a first emission surface 12 that emits P-polarized light by transmitting and reflecting light, which will be described later, and a second emission surface 13 that emits S-polarized light. The first exit surface 12 is provided at a position facing the entrance surface 11 in parallel with the entrance surface 11. The second exit surface 13 is provided in a direction orthogonal to the direction of the entrance surface 11 and the direction of the first exit surface 12 from the center of the polarizing beam splitter 10. The second exit surface 13 extends in a direction orthogonal to the entrance surface 11 and the first exit surface 12.

  The polarization beam splitter 10 includes three optical members (21 to 23) joined to each other. The three optical members are a first optical member 21 having a trapezoidal shape, a second optical member 22 having a rectangular shape, and a trapezoidal shape when viewed from the side of the polarizing beam splitter 10 (a direction orthogonal to an incident surface described later). The third optical member 23 has a constant thickness.

  The first optical member 21 has a pair of side edges each forming 45 ° with the lower bottom. One of the pair of sides of the first optical member 21 is the incident surface 11. The second optical member 22 has the same length as the lower base of the first optical member 21, and is opposed to a long side (referred to as an upper long side) joined to the lower base of the first optical member 21 and an upper long side. And the opposite long side (referred to as the lower long side) parallel to the upper long side. The length of the short side of the second optical member 22 is twice the height of the trapezoid of the first optical member 21 and ２１ of the length of the long side of the second optical member 22. The third optical member 23 has a lower base having the same length as the lower long side of the second optical member 22 and a pair of side sides each forming 45 ° with respect to the lower base. The optical member 22 is joined to a surface forming the lower long side. The third optical member 23 has the same shape as the first optical member 21.

  The interface between the first optical member 21 and the second optical member 22 (the joint surface formed by the surface forming the lower bottom of the first optical member 21 and the surface forming the upper long side of the second optical member 22) A first polarization separation film 31 is provided. The first polarization separation film 31 reflects a part of the light incident from the incident surface 11 and transmits the remaining part. Here, the first polarization separation film 31 means a film provided in (the area of) the optical path of the light incident from the incident surface 11 among the interfaces between the two optical members (21, 22). However, the polarization splitting film is provided on the entire area of the interface between the first optical member 21 and the second optical member 22, and the left portion in the figure of the polarization splitting film forms the first polarization splitting film 31, The right portion in the figure forms a second polarization separation film 32 described later. The plane including the optical axis of the light incident on the first polarization separation film 31 and the optical axis of the light reflected on the first polarization separation film 31 is the incident surface.

  The first polarized light separating film 31 allows the oscillating electric field to transmit P-polarized light within the plane of incidence (a component parallel to the plane of incidence), and causes the oscillating electric field to oscillate perpendicularly to the plane of incidence (a component perpendicular to the plane of incidence). ) S-polarized light is reflected. That is, the first polarization splitting film 31 converts the light incident from the incident surface 11 into P-polarized light transmitted through the first polarization splitting film 31 (accurately, transmitted light containing a large amount of P-polarized light components). The light is separated into S-polarized light (reflected light containing a large amount of S-polarized component) reflected by the film 31.

  The interface between the second optical member 22 and the third optical member 23 (the joint surface formed by the surface forming the lower long side of the second optical member 22 and the lower bottom surface of the third optical member 23) , A third polarized light separating film 33. The third polarized light separating film 33 reflects a part (S-polarized light) of the light transmitted through the first polarized light separating film 31, and transmits the remaining part (P-polarized light). The third polarized light separating film 33 may be provided on the optical path of the P-polarized light transmitted through the first polarized light separating film 31 at the interface between the two optical members (22, 23). In the present embodiment, the third polarization separation film 33 is provided on the entire area of the interface between the second optical member 22 and the third optical member 23.

  The third polarization separation film 33 is provided in parallel with the first polarization separation film 31. Therefore, the entrance plane for the third polarization separation film 33 is the same as the entrance plane for the first polarization separation film 31. Similarly to the first polarization separation film 31, the third polarization separation film 33 allows the oscillating electric field to transmit the P-polarized light existing in the incident plane, and reflects the S-polarized light whose oscillating electric field oscillates perpendicularly to the incident plane. That is, the third polarization separation film 33 converts the light transmitted through the first polarization separation film 31 into P-polarized light transmitted through the third polarization separation film 33 and S-polarized light reflected by the third polarization separation film 33. To separate.

  An anti-reflection film 41 is provided on a pair of side surfaces of the first optical member 21 and a pair of side surfaces of the third optical member 23. Thus, the polarization beam splitter 10 has a 180-degree rotationally symmetrical shape and a left-right symmetrical shape.

These polarization separation films (31 to 33) are made of fluorides such as AlF ₃ , MgF ₂ , Na ₃ AlF ₆ , LaF ₃ , GdF ₃ and YF ₃ , or SiO ₂ , AlO ₃ , HfO ₂ , ZrO ₂ , It contains at least one material selected from the group consisting of oxides such as Ta ₂ O ₅ and TiO ₂ , sulfides such as ZnS, and semiconductors. In the present embodiment (FIG. 3), the polarization separation films (31 to 33) are made of HfO ₂ and SiO ₂ . From these materials, it is preferable to select a film material having a small light absorption for incident light having a wavelength in the ultraviolet wavelength range to the infrared wavelength range. Thereby, the polarizing beam splitter 10 can be applied to a wide wavelength range from the ultraviolet wavelength range to the infrared wavelength range.

  These optical members (21 to 23) are made of optical crystals such as sapphire, calcium fluoride, magnesium fluoride and ZnSe, or optical glasses such as synthetic quartz and BK7, ceramics such as YAG ceramics, and semiconductors. At least one material selected from the group consisting of: In the present embodiment, these optical members (21 to 23) are formed of synthetic quartz. From these materials, it is preferable to select an optical material having a small light absorption with respect to incident light having a wavelength in a range from the ultraviolet wavelength range to the infrared wavelength range. Thereby, the polarizing beam splitter 10 can be applied to a wide wavelength range from the ultraviolet wavelength range to the infrared wavelength range.

  Adjacent ones of these optical members (21 to 23) are bonded to each other by any one of optical contact, surface activation bonding, diffusion bonding, and bonding with an adhesive. The adhesive preferably has low light absorption. Thereby, even if the incident light 6 has a wavelength in the range from the ultraviolet wavelength range to the infrared wavelength range, the absorption of light by the bonding surfaces of the optical members (21 to 23) is suppressed. Therefore, the polarizing beam splitter 10 can be applied to a wide wavelength range from the ultraviolet wavelength range to the infrared wavelength range.

  Therefore, even if the incident light 6 has a wavelength in the range from the ultraviolet wavelength range to the infrared wavelength range, depending on the polarization separation films (31 to 33), the optical members (21 to 23), and the bonding surfaces of the optical members (21 to 23). Light absorption is suppressed. Therefore, the polarization beam splitter 10 can be applied to a wide wavelength range from the ultraviolet wavelength range to the infrared wavelength range.

  The light incident from the incident surface 11 is separated by the first polarization splitting film 31 into light that is transmitted and light that is reflected. The light transmitted through the first polarization separation film 31 is separated by the third polarization separation film 33 into light that is transmitted and light that is reflected. The light transmitted through the third polarization separation film 33 is transmitted from the first emission surface 12 provided on one of the trapezoidal sides of the third optical member 23 at a position facing the incidence surface 11 in parallel with the incidence surface 11. The light exits perpendicular to the first exit surface 12. That is, the optical axis of the light emitted from the first emission surface 12 is the same as the optical axis of the incident light 6.

  On the other hand, the light reflected by the first polarization splitting film 31 is totally reflected by the trapezoidal upper base surface of the first optical member 21 (total reflection surface 14). The light reflected by the total reflection surface 14 enters the second polarization separation film 32 in parallel with the optical axis of the incident light 6, and is separated by the second polarization separation film 32 into light that is transmitted and light that is reflected. The second polarized light separating film 32 is formed of the polarized light separating film provided on the entire area of the interface between the first polarized light separating film 31 and the first optical member 21 and the second optical member 22. Means provided in (area of) the optical path. That is, the second polarized light separating film 32 is substantially the same as the first polarized light separating film 31, and transmits P-polarized light and reflects S-polarized light.

  Since the first polarization separation film 31 and the second polarization separation film 32 are provided on the same plane as described above, the first optical elements disposed on both sides of the first polarization separation film 31 and the second polarization separation film 32 are provided. Processing of the member 21 and the second optical member 22 is easy. In addition, the first polarization separation film 31 and the second polarization separation film 32 can be made parallel with high accuracy.

  The light reflected by the second polarization splitting film 32 is transmitted from the second exit surface 13 orthogonal to the incident surface 11 provided on a side different from the incident surface 11 among the pair of trapezoidal sides of the first optical member 21. The light exits perpendicularly to the second exit surface 13. That is, the optical axis of the light emitted from the second emission surface 13 is orthogonal to the optical axes of the incident light 6 and the light emitted from the first emission surface 12. Further, since the height of the trapezoid of the first optical member 21 is 短 of the length of the short side of the second optical member 22, the optical axis of the light emitted from the second emission surface 13 is the second optical member. The center of the member 22 is orthogonal to the optical axis of the incident light 6. Since the third optical member 23 has the same shape as the first optical member 21, the center of the second optical member 22 forms the center of the polarization beam splitter 10.

  The polarization separation film can increase the reflectance of S-polarized light by stacking several tens of layers to form a thick film. Therefore, it is relatively easy to reduce the transmittance of the S-polarized light (reduce the S-polarized light mixed with the P-polarized light transmitted through the polarization separation film). On the other hand, in order to increase the transmittance of P-polarized light, it is necessary to adjust the refractive index and the thickness of the film so as to satisfy the Brewster condition. (Reducing P-polarized light mixed with S-polarized light) is relatively difficult. Therefore, there is a tendency that P-polarized light mixed with S-polarized light increases.

  FIG. 3 is a graph showing light transmission characteristics of the polarization separation films (31 to 33). The horizontal axis indicates wavelength, and the vertical axis indicates light transmittance. As shown in FIG. 3, the light transmittance of the polarization separation film changes according to the wavelength. The transmittance of the S-polarized light is about 0% when the wavelength is 540 nm or less, and increases as the wavelength becomes longer when the wavelength exceeds 540 nm, and becomes the largest around 590 nm (99% or more). If it exceeds that, it will decrease. On the other hand, the transmittance of P-polarized light is the smallest around a wavelength of 475 nm (about 10%), monotonically increases as the wavelength increases from 475 nm, and reaches a maximum (about 99.5%) around a wavelength of 520 nm. Becomes

  Here, the P-polarized light transmittance is Tp, the P-polarized light reflectance is Rp, the S-polarized light transmittance is Ts, and the S-polarized light reflectance is Rs. In the polarization separation film having the characteristics shown in FIG. 3, for light having a wavelength of 532 nm, Tp = 99.5%, Rp = 0.5%, Ts = 0.1%, and Rs = 99.9%.

  In this case, the P-polarized light mixed with the S-polarized light emitted from the second emission surface 13 is Rp × Rp = 0.5% × 0.5% = 0.0025% (extinction ratio of S-polarized light: 46 dB) ). As described above, in this embodiment, since the light reflected by the first polarization separation film 31 is again polarized and separated by the second polarization separation film 32, the light is reflected only by the first polarization separation film 31 (Rp = 0.5%). (Extinction ratio: 23 dB)), the extinction ratio of S-polarized light is doubled.

The S-polarized light mixed with the P-polarized light emitted from the first emission surface 12 is Ts × Ts = 0.1% × 0.1% = 10 ⁻⁴ % (extinction ratio of P-polarized light: 60 dB). And the extinction ratio of P-polarized light is sufficiently small. If the third polarization separation film 33 is not provided at the interface between the second optical member 22 and the third optical member 23, the S-polarized light mixed with the P-polarized light emitted from the first emission surface 12 Light has Ts = 0.1% (extinction ratio of P-polarized light: 30 dB). Even in this case, the extinction ratio of P-polarized light is higher than the extinction ratio of S-polarized light in the case of single reflection (23 dB). In the present embodiment, since the third polarized light separating film 33 parallel to the first polarized light separating film 31 is provided in the optical path of the P-polarized light transmitted through the first polarized light separating film 31, the light exits from the first exit surface 12. The extinction ratio of P-polarized light becomes 60 dB.

  As described above, in one polarization beam splitter 10 formed by joining a plurality of optical members (21 to 23), high optical axis accuracy can be realized according to the processing accuracy of the optical members (21 to 23). Therefore, there is no need to adjust the alignment between the plurality of polarizing beam splitters in order to align the optical axes.

  In the present embodiment, the polarizing beam splitter 10 includes a first optical member 21 having a trapezoidal shape in a side view, and a second optical member 22 having a rectangular shape joined to a lower bottom surface of the first optical member 21. And a trapezoidal third optical member 23 joined to the lower long side surface of the second optical member 22. Then, the entrance surface 11 and the first exit surface 12 are provided on the side of the first optical member 21, and the first polarization separation film 31 and the second polarization separation film 32 are formed by the first optical member 21 and the second optical member 22. And the second emission surface 13 is provided on one of the sides of the third optical member 23. Therefore, the shape of the first to third optical members 23 is simple, the processing of these optical members (21 to 23) is easy, and the optical members (21 to 23) can be manufactured with high accuracy. is there. Further, the alignment adjustment of the polarizing beam splitter 10 is also easy.

  In the present embodiment, since the reflection surface that reflects the S-polarized light reflected by the first polarization separation film 31 is the total reflection surface 14, the reflection surface can be easily formed on the first optical member 21. .

  Further, in the present embodiment, the polarization separation angle formed by the optical axis of the P-polarized light emitted from the first emission surface 12 and the optical axis of the S-polarized light emitted from the second emission surface 13 is 90 °. Therefore, when other optical elements utilizing the S-polarized light and the P-polarized light are provided around the polarization beam splitter 10, the alignment of these optical elements can be easily adjusted. That is, the usability of the polarization beam splitter 10 is high.

  As described above, the polarizing beam splitter 10 is applicable to a wide wavelength range from the ultraviolet wavelength range to the infrared wavelength range. Therefore, if the light source 5 emits light in the wavelength range from the ultraviolet wavelength range to the infrared wavelength range, the light in the wavelength range from the ultraviolet wavelength range to the infrared wavelength range can be separated into the S wave and the P wave with a high extinction ratio. .

<< 2nd Embodiment >>
Next, a polarization beam splitter 10 according to a second embodiment will be described with reference to FIG. Note that the same or similar elements as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The same applies to the following embodiments.

  In the polarization beam splitter 10 of the present embodiment, a pair of fourth optical members 24 are joined to a surface forming a lower bottom of the first optical member 21 and a surface forming a lower bottom of the third optical member 23. The fourth optical member 24 in the illustrated example has a rectangular shape (that is, a plate shape) in a side view. At the interface between the fourth optical member 24 and the first optical member 21 or the third optical member 23, the fourth polarized light that reflects a part of the light reflected by the first polarization separation film 31 and transmits the remaining part. A separation film 34 is provided. That is, the reflection surface that reflects the S-polarized light reflected by the first polarization separation film 31 is configured by the fourth polarization separation film 34 instead of the total reflection surface 14 of the first embodiment. Here, the fourth polarized light separating film 34 means a film provided in (an area of) the optical path of the light reflected by the first polarized light separating film 31 at the interface between the two optical members. In the present embodiment, a polarization splitting film is provided on the entire area of the interface. The polarization beam splitter 10 has a 180-degree rotationally symmetrical and left-right symmetrical shape as in the first embodiment.

  As described above, the reflection surface that reflects the light reflected by the first polarization separation film 31 includes the fourth polarization separation film 34 provided between the joining surfaces of two optical members adjacent to each other. Therefore, the S-polarized light included in the P-polarized light reflected by the first polarization separation film 31 is reduced by the polarization separation in the fourth polarization separation film 34. In other words, the P-polarized light is emitted from the second emission surface 13 even with a higher extinction ratio by performing triple polarization separation by the polarization separation film.

Specifically, the P-polarized light mixed with the S-polarized light emitted from the second emission surface 13 is Rp × Rp × Rp = 0.5% × 0.5% × 0.5% = 1.3. × 10 ⁻⁵ % (extinction ratio of S-polarized light: 69 dB). As described above, in this embodiment, the P-polarized light is triple-polarized and separated by the first, second, and third polarization separation films 31, 32, and 34. Therefore, the total reflection surface of the first embodiment is used. The extinction ratio of S-polarized light is 1.5 times that of the case of 14 (extinction ratio: 46 dB).

<< 3rd Embodiment >>
Next, a polarization beam splitter 10 according to a third embodiment will be described with reference to FIGS. FIG. 5 is an explanatory diagram of the generation principle of stray light, taking the polarization beam splitter 10 according to the first embodiment as an example. As shown in FIG. 5, the light reflected by the first polarization separation film 31 also includes P-polarized light, and this light is reflected by the total reflection surface 14 and irradiated on the second polarization separation film 32. You. Then, most of the P-polarized light passes through the second polarization separation film 32 and is totally reflected by the right surface (the surface forming the short side of the rectangle) of the second optical member 22. Therefore, the P-polarized light is repeatedly reflected by the total reflection surface 14 while passing through the polarization separation film, and remains as stray light inside the polarization beam splitter 10.

  To deal with this problem, in the polarization beam splitter 10 of the present embodiment, as shown in FIG. 6, a pair of light absorbing members 43 is provided instead of the pair of fourth optical members 24 of the second embodiment. In addition, a polarization separation film 34 is formed on the interface between the first optical member 21 or the third optical member 23 and the light absorbing member 43. Further, a pair of light absorbing members 43 is also provided on the surface forming the short side of the second optical member 22, and the fifth polarization separation is provided at each of the interfaces between the second optical member 22 and the pair of light absorbing members 43. A film 35 is formed. The light absorbing member 43 is made of, for example, black quartz glass. The polarization beam splitter 10 of the present embodiment also has a 180-degree rotationally symmetric and left-right symmetrical shape.

  As described above, in the present embodiment, the light absorbing member 43 is provided in the optical path of the P-polarized residual light transmitted through the fourth polarization separation film 34. Therefore, the residual P-polarized light transmitted through the fourth polarization separation film 34 is prevented from becoming stray light and remaining inside the polarization beam splitter 10.

  Also, a light absorbing member 43 is provided on the optical path of the P-polarized residual light reflected by the fourth polarization separation film 34 and transmitted through the second polarization separation film 32. Therefore, the residual light of the P-polarized light transmitted through the second polarization separation film 32 is also prevented from becoming stray light and remaining inside the polarization beam splitter 10.

<< 4th Embodiment >>
Next, a polarization beam splitter 10 according to a fourth embodiment will be described with reference to FIG. In the polarization beam splitter 10 of the present embodiment, the pair of fourth optical members 24 joined to the lower base of the first optical member 21 and the lower base of the third optical member 23 are arranged in a side view. To form a right-angled isosceles triangle with the joining surface as a slope. An anti-reflection film 41 is provided on a surface (front surface) forming two sides sandwiching the right angle. Also in this embodiment, the polarization beam splitter 10 has a 180-degree rotationally symmetrical and left-right symmetrical shape. In the present embodiment, similarly to the second embodiment, a fourth polarization separation film 34 is provided at the interface between the fourth optical member 24 and the first optical member 21 or the third optical member 23.

  The P-polarized residual light reflected by the first polarization separation film 31 and transmitted through the fourth polarization separation film 34 is perpendicularly incident on the surface of the upper fourth optical member 24 on which the antireflection film 41 is provided. From the surface. On the other hand, the P-polarized residual light reflected by the fourth polarized light separating film 34 and transmitted through the second polarized light separating film 32 is totally reflected on the surface forming the short side of the second optical member 22 which enters at an incident angle of 45 degrees. I do. After that, the residual light of the P-polarized light sequentially passes through the third polarized light separating film 33 and the fourth polarized light separating film 34 and is perpendicular to the surface of the fourth optical member 24 on the lower side in the figure where the antireflection film 41 is provided. And exits from this surface.

  As described above, the optical path of the P-polarized residual light transmitted through the fourth polarization separation film 34 (the surface of the upper fourth optical member 24 in the drawing) and the P-polarized residual light transmitted through the second polarization separation film 32 Surfaces perpendicular to the optical axis are formed on the optical path (the surface of the fourth optical member 24 on the lower side in the figure), and the antireflection film 41 is provided on these surfaces. Therefore, the residual P-polarized light transmitted through the fourth polarization separation film 34 and the third polarization separation film 33 is prevented from becoming stray light and remaining inside the polarization beam splitter 10.

<< 5th Embodiment >>
Next, a polarization beam splitter 10 according to a fifth embodiment will be described with reference to FIG. In the polarization beam splitter 10 of the present embodiment, in addition to the configuration of the fourth embodiment (FIG. 7), the joining surface is formed as an inclined surface in a pair of surfaces forming the short side of the second optical member 22 in a side view. A pair of fifth optical members 25 forming a right-angled isosceles triangle are provided. A fifth polarization separating film 35 that transmits P-polarized light and reflects S-polarized light is also provided at the interface between the fifth optical member 25 and the second optical member 22. Further, an antireflection film 41 is also provided on a surface (front surface) forming two sides sandwiching the right angle of the pair of fifth optical members 25 joined to the second optical member 22. Also in the present embodiment, the polarization beam splitter 10 has a 180-degree rotationally symmetric and left-right symmetric shape.

  In the present embodiment, the P-polarized residual light transmitted through the fourth polarization separation film 34 is transmitted from an anti-reflection film 41 provided on the optical path (the surface of the upper fourth optical member 24 in the figure) perpendicular to the optical axis. Emitted to the outside. On the other hand, the P-polarized residual light reflected by the fourth polarization separation film 34 and transmitted through the second polarization separation film 32 has a fifth surface on the short side of the second optical member 22 which enters at an incident angle of 45 degrees. The light passes through the polarization separation film 35. Thereafter, the P-polarized residual light is perpendicularly incident on the surface of the fifth optical member 25 on the right side where the antireflection film 41 is provided, and exits from this surface. Therefore, the residual P-polarized light transmitted through the fourth polarization splitting film 34 and the residual P-polarized light reflected by the fourth polarization splitting film 34 are prevented from remaining as stray light inside the polarization beam splitter 10. .

<< 6th Embodiment >>
Next, a polarization beam splitter 10 according to a sixth embodiment will be described with reference to FIG. The polarization beam splitter 10 of the present embodiment is different from the polarization beam splitter 10 of the first embodiment (FIG. 1) in that a pair of surfaces forming the short sides of the second optical member 22 and the upper bottom of the third optical member 23 are provided. The difference is that the light absorbing member 43 is joined to the surface forming the. The light absorbing member 43 is made of, for example, black quartz glass. The surface forming the upper bottom of the first optical member 21 is the total reflection surface 14 as in the first embodiment. The polarization beam splitter 10 of the present embodiment is not a rotationally symmetric shape but a left-right symmetric shape.

  The light reflected by the first polarization splitting film 31 is totally reflected by the trapezoidal upper bottom surface of the first optical member 21 (the total reflection surface 14) and is incident on the second polarization splitting film 32, where the second polarization splitting is performed. The light is separated into transmitted light and reflected light by the film 32. Most of the light transmitted through the second polarization separation film 32 is absorbed by the light absorbing member 43 provided on the right surface of the second optical member 22 in the drawing. Even if a part of the light transmitted through the second polarization separation film 32 is reflected by the light absorbing member 43 on the right side in the figure, this light is transmitted by the lower light absorbing member 43 joined to the third optical member 23 in the figure. Absorbed.

  As described above, in the present embodiment, the light absorbing member 43 is provided on the optical path of the P-polarized residual light reflected by the total reflection surface 14 and transmitted through the second polarization separation film 32. Therefore, it is possible to suppress the residual P-polarized light reflected on the total reflection surface 14 from becoming stray light and remaining inside the polarization beam splitter 10.

{Seventh embodiment}
Next, a polarization beam splitter 10 according to a seventh embodiment will be described with reference to FIG. In the polarization beam splitter 10 of the present embodiment, the third optical member 23 has the same shape as the fourth optical member 24 of the fourth embodiment (FIG. 7) or the fifth embodiment (FIG. 8) (ie, a right angle in side view). Isosceles triangle) and the same size. The third optical member 23 is joined to the second optical member 22 with its oblique side facing the right side of the lower long side in the drawing. An anti-reflection film 41 is provided on a surface on the right side of the drawing, which forms the first emission surface 12, of two surfaces sandwiching the right angle of the third optical member 23.

  In this manner, the third optical member 23 forms a triangle having a hypotenuse joined to the lower long side of the second optical member 22, and the second emission surface 13 is provided on a side different from the hypotenuse of the third optical member 23. ing. Therefore, the size of the third optical member 23 is reduced, and the size and weight of the polarization beam splitter 10 are reduced.

  In another embodiment, of the two sides sandwiching the right angle of the third optical member 23, the surface on the left side in the drawing such that the P-polarized residual light transmitted through the second polarization separation film 32 is emitted to the outside. May also be provided with an anti-reflection film 41. In the illustrated example, the surface forming the upper bottom of the first optical member 21 is the total reflection surface 14. However, a fourth polarization separating film 34 may be provided on this surface to join the fourth optical member 24. .

<< Eighth Embodiment >>
Next, a polarization beam splitter 10 according to an eighth embodiment will be described with reference to FIG. In the polarization beam splitter 10 of the present embodiment, the length of the short side of the second optical member 22 is の of that of the above embodiment, and the size of the third optical member 23 in the side view is the seventh embodiment. It is twice as large as the form (FIG. 10).

  With such a configuration, the second optical member 22 can be reduced in size, and the polarization beam splitter 10 can be reduced in size and weight.

<< Ninth embodiment >>
Next, a polarization beam splitter 10 according to a ninth embodiment will be described with reference to FIG. In the polarization beam splitter 10 of the present embodiment, the second optical member 22 has the same shape as the first optical member 21 (that is, a trapezoid having a pair of sides forming 45 ° with respect to the lower bottom in side view) and They are the same size. The second optical member 22 is joined to the first optical member 21 with the lower bases facing each other. The third optical member 23 has the same shape and the same size as the seventh embodiment (FIG. 10). Therefore, the polarizing beam splitter 10 has a diamond shape in a side view.

  An anti-reflection film 41 is provided on a surface of the pair of sides of the second optical member 22 that forms the same right side as the first emission surface 12. The P-polarized residual light that has passed through the second polarization separation film 32 is emitted to the outside from the surface forming the right side of the second optical member 22. Therefore, the residual P-polarized light transmitted through the second polarization separation film 32 does not become stray light.

  As described above, in this embodiment, the second optical member 22 has a side (lower bottom) joined to the lower bottom of the first optical member 21 and a square (upper bottom) having the opposite side parallel to the lower bottom (upper bottom). Trapezoid). Further, the third optical member 23 forms a triangle having an oblique side joined to the opposite side (upper bottom) of the second optical member 22. With these configurations, the polarizing beam splitter 10 can be reduced in size and weight by making the second optical member 22 and the third optical member 23 smaller.

  Although the description of the specific embodiments has been completed above, the present invention can be widely modified without being limited to the above embodiments. A part of the configuration of the above embodiment may be appropriately combined. In addition, the specific configuration, arrangement, quantity, angle, material, wavelength, and the like of each member and portion can be appropriately changed within a range not departing from the gist of the present invention. On the other hand, all of the components shown in the above embodiment are not necessarily essential, and can be appropriately selected.

DESCRIPTION OF SYMBOLS 1 Polarization separation apparatus 5 Light source 6 Incident light 10 Polarization beam splitter 11 Incident surface 12 First exit surface 13 Second exit surface 14 Total reflection surface (reflection surface)
Reference Signs List 21 first optical member 22 second optical member 23 third optical member 24 fourth optical member 25 fifth optical member 31 first polarized light separating film 32 second polarized light separating film 33 third polarized light separating film 34 fourth polarized light separating film ( Reflective surface)
35 Fifth polarization splitting film 41 Antireflection film 43 Light absorbing member

Claims (13)

A polarizing beam splitter formed by joining a plurality of optical members,
An incident surface on which incident light is incident from a predetermined direction,
A first polarization separation film provided in an optical path of light incident from the incident surface;
A first emission surface for emitting P-polarized light transmitted through the first polarization separation film;
A reflection surface for reflecting the S-polarized light reflected by the first polarization separation film;
A second polarization separation film provided in an optical path of the S-polarized light reflected by the reflection surface;
A second emission surface for emitting the S-polarized light reflected by the second polarization separation film.   The polarization beam splitter according to claim 1, wherein the first polarization separation film and the second polarization separation film are provided on the same plane.   The polarization beam according to claim 2, further comprising a third polarization separation film provided in parallel with the first polarization separation film in an optical path of the P-polarized light transmitted through the first polarization separation film. Splitter. A plurality of optical members having a trapezoidal shape in a side view, a second optical member having a long side joined to a lower bottom of the first optical member, and a second optical member having a rectangular shape; A third optical member having a trapezoidal shape having a lower bottom joined to the opposite side opposite to the long side,
The entrance surface and the second exit surface are provided on a side of the first optical member,
The first polarization separation film and the second polarization separation film are provided at an interface between the first optical member and the second optical member,
4. The polarization beam splitter according to claim 2, wherein the first emission surface is provided on one of sides of the third optical member. 5. The plurality of optical members are a first optical member having a trapezoidal shape in a side view, and a quadrangular shape having one side joined to a lower base of the first optical member and an opposite side parallel to the one side opposed thereto. A second optical member and a third optical member having a triangular shape having a hypotenuse joined to the opposite side of the second optical member,
The entrance surface and the second exit surface are provided on a side of the first optical member,
The first polarization separation film and the second polarization separation film are provided at an interface between the first optical member and the second optical member,
The polarization beam splitter according to claim 2, wherein the first emission surface is provided on a side different from the oblique side of the third optical member.   The polarizing beam splitter according to claim 1, wherein the reflection surface is a total reflection surface.   The polarization beam splitter according to any one of claims 1 to 5, wherein the reflection surface is formed of a fourth polarization separation film provided at an interface between two optical members adjacent to each other.   7. The light-absorbing member according to claim 1, further comprising a light absorbing member provided on an optical path of the residual light of the P-polarized light that has been reflected by the reflection surface and transmitted through the second polarization separation film. A polarizing beam splitter as described.   The polarization beam splitter according to claim 7, further comprising an antireflection film or a light absorbing member provided on an optical path of the residual light of the P-polarized light transmitted through the fourth polarization separation film.   2. The polarization separation angle between the optical axis of the P-polarized light emitted from the first emission surface and the optical axis of the S-polarized light emitted from the second emission surface is 90 °. The polarizing beam splitter according to claim 9.   The first polarization separation film and the second polarization separation film include at least one material selected from the group consisting of a fluoride, an oxide, a sulfide, and a semiconductor. The polarizing beam splitter according to any one of the above.   The polarization beam splitter according to claim 1, wherein the plurality of optical members include at least one material selected from the group consisting of an optical crystal, an optical glass, a ceramic, and a semiconductor. .   The two optical members adjacent to each other are joined to each other by any one of optical contact, surface activation joining, diffusion joining, and joining with an adhesive. A polarizing beam splitter as described.

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