WO2013046921A1 - Polarizer, polarizing optical element, light source, and image display device - Google Patents

Polarizer, polarizing optical element, light source, and image display device Download PDF

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Publication number
WO2013046921A1
WO2013046921A1 PCT/JP2012/069768 JP2012069768W WO2013046921A1 WO 2013046921 A1 WO2013046921 A1 WO 2013046921A1 JP 2012069768 W JP2012069768 W JP 2012069768W WO 2013046921 A1 WO2013046921 A1 WO 2013046921A1
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WIPO (PCT)
Prior art keywords
light
polarizer
substrate
dielectric
optical element
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PCT/JP2012/069768
Other languages
French (fr)
Japanese (ja)
Inventor
友嗣 大野
雅雄 今井
鈴木　尚文
瑞穂 冨山
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日本電気株式会社
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Publication of WO2013046921A1 publication Critical patent/WO2013046921A1/en

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G03B21/2073—Polarisers in the lamp house
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3058—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state comprising electrically conductive elements, e.g. wire grids, conductive particles
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528—Polarisers
    • G02F1/133548—Wire-grid polarisers

Definitions

  • the present invention relates to a polarizer that polarizes light.
  • Such a projector includes a light source, an illumination optical system that receives light emitted from the light source, a modulation element that modulates and emits light from the illumination optical system according to a video signal, and light from the modulation element on a screen. And a projection optical system for projecting onto the screen.
  • LED Light Emitting Diode
  • a polarizing element such as a liquid crystal panel may be used as the modulation element.
  • the non-polarized light needs to be converted into a specific polarization state in order to efficiently use the emitted light of the LED as the projection light.
  • the light source may be provided with a polarizing optical element that converts non-polarized light from the LED into light having a specific polarization state and emits the light.
  • a polarizing optical element an element using a wire grid polarizer that is excellent in light utilization efficiency and can be easily reduced in thickness is attracting attention.
  • FIG. 1 is a diagram showing an example of a wire grid polarizer. As shown in FIG. 1, in the wire grid polarizer, a plurality of metal wires 102, which are linear metal members, are arranged on a substrate 101 in a grid.
  • TM polarized light that is a polarization component polarized in the direction A perpendicular to the extending direction of the metal wire 102 in the incident light 111. Passes through the wire grid polarizer and exits as transmitted light 112.
  • TE polarized light that is a polarization component polarized in a direction B orthogonal to the direction A in the incident light 111 is reflected by a wire grid polarizer and returned to the light incident side as reflected light 113 (Patent Document). 1 and 2).
  • FIGS. 2 and 3 are diagrams showing an example of a polarizing optical element using a wire grid polarizer.
  • the polarizing optical element shown in FIG. 2 includes a ⁇ / 4 plate 302 provided on a light emitting element 301 that is an LED, and a wire grid polarizer 303 provided on the ⁇ / 4 plate 302.
  • TM polarized light of the incident light is transmitted through the wire grid polarizer 303 and emitted from the polarizing optical element.
  • the TE polarized light in the incident light is reflected by the wire grid polarizer 303.
  • the reflected light enters the light emitting element 301 through the ⁇ / 4 plate 302, is further reflected by the light emitting element 301, and reenters the wire grid polarizer 303 through the ⁇ / 4 plate 302.
  • the light re-entering the wire grid polarizer 303 passes through the ⁇ / 4 plate 302 twice and becomes TM polarized light, so that it passes through the wire grid polarizer 303 and is emitted from the polarization optical element.
  • the light emitted from the light emitting element 301 is converted into TM polarized light and emitted.
  • the polarizing optical element shown in FIG. 3 has a depolarizing element 302 ′ that converts light into non-polarized light and emits it, instead of the ⁇ / 4 plate 302.
  • the light re-entering the wire grid polarizer 303 is unpolarized because it passes through the depolarization element 302 '. Therefore, TM polarized light of the re-incident light is transmitted through the wire grid polarizer 303, and TE polarized light is further reflected by the wire grid polarizer 303. By repeating such reflection, the light emitted from the light emitting element 301 is converted into TM polarized light and emitted.
  • the light loss can be reduced by re-entering the light returned to the light incident side into the wire grid polarizer.
  • the light extraction efficiency is not sufficient.
  • the present invention has been made in view of the above problems, and a polarizer, a polarizing optical element, and a light source capable of increasing light extraction efficiency when converting non-polarized light into light having a specific polarization state. And it aims at providing an image display device.
  • a first polarizer according to the present invention includes a substrate, a first dielectric portion provided on the substrate, and a metal portion provided on the first dielectric portion, the first dielectric The portion is provided so as to become smaller from the substrate toward the metal portion.
  • a second polarizer according to the present invention includes a substrate, a first dielectric part provided on the substrate, and a metal part provided on the first dielectric part,
  • the dielectric part has an inclined surface from the substrate toward the metal part, and the side surface of the first dielectric part is an inclined surface formed to incline from the substrate toward the metal part.
  • the surface of the dielectric portion on which the metal portion is provided is smaller than the surface on which the substrate of the first dielectric portion is provided.
  • the polarizing optical element according to the present invention includes a polarizer and a polarization state conversion element that is provided on the structure and emits light while changing the polarization state of incident light.
  • the light source of the present invention includes a polarizing optical element and a light emitting element that emits light to the polarizing optical element.
  • the image display device of the present invention has a light source.
  • the present invention it is possible to increase the light extraction efficiency when converting non-polarized light into light having a specific polarization state.
  • FIG. 1 is a layout diagram illustrating an example of a configuration of an image display device using a light source according to a first embodiment of the present invention.
  • FIG. 1 is a layout diagram illustrating an example of a configuration of an image display device using a light source according to a first embodiment of the present invention. It is a figure which shows the evaluation result of the integrated transmittance
  • FIG. 4 is a perspective view schematically showing the light source of the first embodiment of the present invention.
  • the thickness of each layer is very thin, and the difference in thickness between the layers is large, so it is difficult to illustrate each layer with an accurate scale and ratio. For this reason, in the drawings, the layers are not schematically drawn but are shown schematically.
  • the light source 10 of this embodiment includes a light emitting element 1 and a polarizing optical element 2 provided on the light emitting element 1.
  • the light emitting element 1 is, for example, an LED and emits light to the polarizing optical element 2.
  • emitted from the light emitting element 1 is non-polarized light, and assumes that it is visible light.
  • the polarizing optical element 2 converts the light from the light emitting element 1 into a specific polarization state and emits it.
  • the polarizing optical element 2 includes a wave plate 3 provided on the light emitting element 1 and a polarizer 4 which is a wire grid polarizer provided on the wave plate 3.
  • the light emitting element 1 and the wave plate 3 are in close contact with each other, but actually, they may not be in close contact.
  • the wave plate 3 is an example of a polarization state conversion element that changes the polarization state of light. More specifically, the wave plate 3 converts the linearly polarized light into circularly polarized light (elliptical polarized light) by generating a phase difference of 1 ⁇ 4 wavelength of the light between the linearly polarized light vibrating in directions perpendicular to each other.
  • the ⁇ / 4 plate converts circularly polarized light (elliptical polarized light) into linearly polarized light.
  • the wave plate 3 is preferably a zero order wave plate.
  • Examples of the material of the wave plate 3 include inorganic anisotropic crystals such as sapphire and quartz, anisotropic films such as polycarbonate, and nanostructure anisotropic media.
  • the polarizer 4 has a substrate 11 and a plurality of convex portions 15 laminated on the substrate 11 in the order of the first dielectric layer 12, the metal layer 13, and the second dielectric layer 14.
  • the first dielectric layer 12 is an example of a first dielectric part
  • the metal layer 13 is an example of a metal part
  • the second dielectric layer 12 is an example of a second dielectric part.
  • each convex portion 15 is an example of a structure.
  • the upper surface of the substrate 11 is the XY plane
  • the direction orthogonal to the XY plane is the Z direction.
  • the substrate 11 is formed of a substantially transparent material in the wavelength band of light emitted from the light emitting element 1.
  • the material of the substrate 11 include optical glass such as quartz glass and borosilicate crown, inorganic crystals such as sapphire and quartz, and transparent plastic such as polyetherimide resin and polystyrene resin.
  • Each convex portion 15 on the substrate 11 has a linear shape extended in the Y direction, which is the first direction in the upper surface of the substrate 11. Further, the plurality of convex portions 15 are periodically arranged in a grid shape, more specifically, in the X direction, which is a second direction different from the first direction.
  • the first dielectric layer 12 of each convex portion 15 has a tapered structure (inclined surface) in which the cross-sectional area of the first dielectric layer 12 decreases from the substrate 11 toward the metal layer 13.
  • the width of the first dielectric layer 12 is equal to the period of the protrusions 15 on the contact surface between the substrate 11 and the first dielectric layer 12, and the metal layer 13 of the first dielectric layer 12 is in contact with the taper structure. It is desirable that the surface and the surface of the metal layer 13 in contact with the first dielectric layer 12 have the same size.
  • the taper may be smooth as long as it is linear, exponential, or parabola.
  • the first dielectric layer 12 has a refractive index of 1.5 to 2.0, for example, and a height of about 10 nm to 150 nm.
  • the material of the first dielectric layer 12 is not particularly limited. For example, oxides such as silicon oxide, titanium oxide and aluminum oxide, nitrides such as silicon nitride, magnesium fluoride and calcium fluoride are used. And dielectric materials such as fluoride.
  • the metal layer 13 formed on the first dielectric layer 12 has a high light reflectance in the wavelength band of light emitted from the light emitting element 1, such as aluminum, silver, tin, and alloys thereof. It is desirable to be formed of a material.
  • the material of the second dielectric layer 14 formed on the metal layer 13 is not particularly limited.
  • oxides such as silicon oxide, titanium oxide and aluminum oxide, nitrides such as silicon nitride, and fluorine are used.
  • dielectric materials such as fluorides such as magnesium fluoride and calcium fluoride.
  • the second dielectric layer 14 has a refractive index of 1.0 to 2.0 and a height of 50 nm to 200 nm, for example.
  • the size of the second dielectric layer 14 in the XY direction is preferably equal to the size of the metal layer 13.
  • the second dielectric layer 14 is in close contact with the wave plate 3.
  • a protective material or an adhesive material may be inserted between the second dielectric layer 14 and the wave plate 3.
  • the non-polarized light emitted from the light emitting element 1 enters the surface on which the convex portion 15 of the polarizer 4 is formed via the wave plate 3. Since non-polarized light is non-polarized even after passing through the wave plate 3, light incident on the polarizer 4 is also non-polarized.
  • TM polarized light which is a polarization component perpendicular to the Y direction that is the extending direction of each convex portion 15, is transmitted through each convex portion 15 and further transmitted through the substrate 11 and emitted.
  • TE polarized light that is a polarization component parallel to the Y direction that is the extending direction of each convex portion 15 is reflected by the metal layer 13 of each convex portion 15.
  • the reflected TE polarized light passes through the wave plate 3 and becomes circularly polarized light, is reflected by the light emitting element 1, further passes through the wave plate 3, and becomes TM polarized light and reenters the polarizer 4. Therefore, the re-incident light is transmitted through the polarizer 4 and emitted. For this reason, the light emitted from the polarizer 4 becomes TM polarized light having a specific polarization state.
  • the incident side medium on the light incident side of the metal layer 13 is closer to the absolute value of the refractive index of the metal wire, the TE-polarized light absorption by the metal layer 13 increases, and the TE-polarized light reflectance is increased. Is reduced. For this reason, it is desirable that the incident side medium has a refractive index as small as possible.
  • the incident side medium becomes the wave plate 3. Since the degree of freedom with respect to the refractive index of the wave plate 3 is low, the incident side medium becomes large. For this reason, in the present embodiment, the second dielectric layer 14 having a refractive index of about 1.0 to 2.0 is provided on the metal layer 13, thereby reducing the refractive index of the incident side medium. The reflectance of polarized light is improved.
  • the first dielectric layer 12 having a taper between the substrate 11 and the metal layer 13
  • the first dielectric layer is formed on the metal layer 13 side of the first dielectric layer 12.
  • the volume occupied by air is larger than 12 and the volume occupied by the first dielectric layer 12 is larger on the substrate 11 side of the first dielectric layer 12 than air.
  • Fresnel reflection that occurs at the interface between media having different refractive indexes is less likely to occur as the difference in refractive index between the media is smaller. Therefore, the effective refractive index is directed from the substrate 11 toward the metal layer 13 as described above. If it changes continuously, it becomes possible to reduce reflection and to improve the transmittance of TM polarized light.
  • FIG. 5 is a diagram for explaining a manufacturing method for manufacturing the polarizer 4 included in the light source 10 shown in FIG.
  • the manufacturing method demonstrated below is only an example, Comprising: It is not limited to this.
  • the first dielectric layer 12 is formed on the substrate 11 by using, for example, a vapor deposition method, and then the first dielectric layer is formed by using, for example, a sputtering film forming method.
  • a metal layer 13 is formed on 12, and a second dielectric layer 14 is formed on the metal layer 13. Further, a resist layer 21A is laminated on the second dielectric layer 14 so as to be a thin film.
  • the resist layer 21A is patterned in a grid shape to form a plurality of resist layers 21B arranged in a grid shape.
  • the patterning method is not particularly limited, and examples thereof include a photolithography technique that is a mask exposure method, an imprint method, and the like.
  • etching is performed so as to penetrate the second dielectric layer 14, the metal layer 13, and the first dielectric layer 12, and arranged in a grid pattern. A plurality of convex portions 15 are formed.
  • the first dielectric layer 12 is removed so that the first dielectric layer 12 has a tapered structure.
  • a wet etching method or a dry etching method can be used depending on the materials of the first dielectric layer 12, the metal layer 13, and the second dielectric layer.
  • the resist layer 21B is combined with oxygen radicals, and is replaced with a gaseous reaction product such as CO or CO 2 and removed.
  • FIG. 6 is a layout diagram showing an example of the configuration of the image display apparatus having the light source 10 shown in FIG.
  • the image display apparatus shown in FIG. 6 is a projector that projects light onto a screen to form an image on the screen.
  • the projector 500 includes light sources 501R, 501G, and 501B, optical elements 502R, 502G, and 502B, liquid crystal panels 503R, 503G, and 503B, a cross dichroic prism 504, and a projection optical system 505.
  • Each of the light sources 501R, 501G, and 501B has the same structure as the light source 10 shown in FIG.
  • the light emitting elements 1 of the light sources 501R, 501G, and 501B generate light having different wavelengths.
  • red (R) light is emitted from the light source 501R
  • green (G) light is emitted from the light source 501G
  • blue (B) light is emitted from the light source 501B.
  • Each of the optical elements 502R, 502G, and 502B guides the respective color lights generated from the light sources 501R, 501G, and 501B to the liquid crystal panels 503R, 503G, and 503B, respectively, and enters the liquid crystal panels.
  • the liquid crystal panels 503R, 503G, and 503B are spatial light modulation elements that modulate and emit incident color light according to a video signal.
  • the cross dichroic prism 504 combines and outputs the modulated lights emitted from the liquid crystal panels 503R, 503G, and 503B.
  • the projection optical system 505 projects the combined light emitted from the cross dichroic prism 504 onto the screen 600 and displays an image corresponding to the video signal on the screen 600.
  • FIG. 7 is a layout diagram showing another example of the configuration of the projector according to the present embodiment.
  • the projector 500 ′ includes light sources 501 ⁇ / b> R, 501 ⁇ / b> G, and 501 ⁇ / b> B, a light guide 506, a liquid crystal panel 507, and a projection optical system 508.
  • the light guide 506 synthesizes each color light generated from the light sources 501R, 501G, and 501B and outputs the combined light to the liquid crystal panel 507.
  • the liquid crystal panel 507 is a spatial light modulation element that modulates incident combined light according to a video signal and emits the modulated light.
  • the projection optical system 508 projects the modulated light emitted from the liquid crystal panel 507 onto the screen 600 and displays an image corresponding to the video signal on the screen 600.
  • a liquid crystal panel is used as the spatial light modulation element.
  • the modulation element is not limited to the liquid crystal panel and can be changed as appropriate.
  • FIG. 8 is a diagram showing an evaluation result of the integrated transmittance in the light source 10 of the present embodiment.
  • the integrated transmittance indicates a ratio of light emitted from the polarizer 4 at an emission angle included in the usable angle range in the light emitted from the light emitting element 1.
  • the usable angle range is an angle range that can be actually used out of light emitted in various directions from the polarization conversion element.
  • the light sources 501R and 501G are used.
  • the range of the emission angle of light that can be taken into the optical elements 502R, 502G, and 502B.
  • the substrate 11 is a glass having a refractive index of 1.5
  • the first dielectric layer 12 is a dielectric having a refractive index of 1.8
  • the metal layer 13 is Al
  • the second dielectric layer 14 is a dielectric having a refractive index of 1.5. Formed with.
  • the width of the metal layer 13 was 42 nm, the height was 140 nm, and the period of the convex portions 15 was 110 nm.
  • the height of the first dielectric was 50 nm, the width was 110 nm on the substrate 11 side, and 42 nm on the metal layer 13 side.
  • the height of the second dielectric was 100 nm and the width was 42 nm.
  • the wave plate 3 is a zero order uniaxial quarter wave plate of quartz.
  • the light emitted from the light-emitting element 1 is assumed to be completely non-polarized, the light distribution is Lambertian, and the reflectance of the light-emitting element 1 is assumed to be 100%.
  • E is the evaluation result of the wire grid polarizer alone
  • F is the evaluation result of the light source 10
  • G is the evaluation result of the light source of the related technology shown in FIG. 1
  • H is the output light of the light emitting element 1. This is the result when all polarized light is emitted.
  • the integrated light transmittance of the light source 10 of this embodiment is improved by about 1% compared to the light source of the related art shown in FIG.
  • the first dielectric layer 12 is tapered, it is possible to improve the transmittance of TM polarized light. It is possible to increase the light extraction efficiency when converting to light.
  • the second dielectric layer 14 is provided on the metal layer 13, even if the polarizer 4 is brought into close contact with the wave plate 3, it is possible to suppress the decrease in the reflectance of TE-polarized light, or The reflectance of TE polarized light can be improved. Accordingly, it is possible to suppress a decrease in the reflectance of TE-polarized light or to improve the reflectance of TE-polarized light while suppressing leakage light, so that the light when converting non-polarized light into light of a specific polarization state can be obtained. The extraction efficiency can be increased.
  • FIG. 9 is a perspective view schematically showing a light source according to the second embodiment of the present invention.
  • a light source 10A of this embodiment shown in FIG. 9 has a depolarizing element 3A instead of the wave plate 3 with respect to the light source 10 shown in FIG.
  • the depolarization element 3A is an example of a polarization state conversion element that changes the polarization state of light. More specifically, the depolarizing element 3A emits incident light as non-polarized light.
  • Examples of the material for the depolarizing element 3A include inorganic anisotropic crystals such as sapphire and quartz, and anisotropic films such as polycarbonate, whose thickness varies depending on the position in the plane.
  • the light emitting element 1 and the depolarizing element 3 ⁇ / b> A are in close contact with each other, but actually, they may not be in close contact.
  • the non-polarized light emitted from the light emitting element 1 enters the surface on which the convex portion 15 of the polarizer 4 is formed via the depolarizing element 3A. Since non-polarized light is non-polarized even after passing through the depolarizer 3A, the light incident on the polarizer 4 is also non-polarized.
  • TM polarized light which is a polarization component perpendicular to the Y direction that is the extending direction of each convex portion 15, is transmitted through each convex portion 15 and further transmitted through the substrate 11 and emitted.
  • TE polarized light that is a polarization component parallel to the Y direction that is the extending direction of each convex portion 15 is reflected by the metal layer 13 of each convex portion 15.
  • the reflected TE-polarized light passes through the wave plate 3 to become non-polarized light, is reflected by the light emitting element 1, passes through the wave plate 3, and re-enters the polarizer 4 without being polarized. Therefore, TM polarized light out of the re-incident light is transmitted through the polarizer 4, and TE polarized light out of the re-incident light is reflected again.
  • FIG. 10 is a diagram showing an evaluation result of the integrated transmittance in the light source 10A of the present embodiment.
  • the depolarizing element 3A is assumed to make incident light completely non-polarized, and the configuration of other members is the same as that of the first embodiment.
  • E is the evaluation result of the wire grid polarizer alone
  • F is the evaluation result of the light source 10A
  • G is the evaluation result of the light source of the related technology shown in FIG. 1
  • H is the output of the light emitting element 1. This is the result when all the incident light is emitted in a polarized state.
  • FIG. 11 is a diagram showing a side surface and an upper surface of an optical element according to the third embodiment of the present invention.
  • the optical element 200 of the present embodiment includes a substrate 201, a dielectric part 202 provided on the substrate 201, and a metal part 203 provided on the dielectric part 202.
  • the dielectric portion 202 is an example of a first dielectric portion, and the dielectric portion 202 and the metal portion 203 constitute a structure 204.
  • the upper surface of the substrate 201 is the XY plane, and the direction orthogonal to the XY plane is the Z direction.
  • the dielectric part 202 has a structure that decreases from the substrate 201 toward the metal part 203.
  • the bottom surface that is a surface in contact with the substrate 201 of the dielectric portion 202 is rectangular, and the side surface along the Y direction of the dielectric portion 202 has a tapered structure.
  • the length of the metal part 203 in the Y direction is W1
  • the length of the metal part 203 in the X direction is W2.
  • the length in the Y direction of the upper surface which is the surface in contact with the metal portion 203 of the dielectric portion 202, is W1
  • the length in the X direction of the upper surface of the dielectric portion 202 is W2.
  • TM polarized light which is a polarization component orthogonal to the Y direction, of incident light incident on the functional region 210 is transmitted through the substrate 201
  • TE polarized light which is a polarization component parallel to the Y direction, of the incident light is the metal portion 203. Reflect on.
  • the functional region 210 is a range within ⁇ W1 / 2 in the Y direction from the center of the upper surface of the dielectric part 202 and within ⁇ (W2 / 2 + S) in the X direction from the center of the upper surface of the dielectric part 202. Note that S is half ⁇ / 2 of the wavelength ⁇ of light incident on the optical element 200.
  • the optical element 200 functions as a polarizer and the dielectric portion 202 decreases from the substrate 201 toward the metal portion 203 as in the first and second embodiments. , It becomes possible to suppress Fresnel reflection of TM polarized light, and to increase the light extraction efficiency when converting non-polarized light into light of a specific polarization state.
  • FIGS. 12 to 19 are diagrams showing examples of other shapes of the optical element 200.
  • the side surface facing the Y direction on the substrate 201 has a tapered structure.
  • the bottom surface and the top surface of the dielectric 202 are elliptical. Note that, on the bottom surface and the top surface of the dielectric 202, the straight axis is provided along the Y direction.
  • the side surface of the dielectric 202 is perpendicular to the substrate 201 from the bottom surface to a certain position, and a tapered structure is provided from that position.
  • the side surface of the dielectric 202 has a staircase shape.
  • a plurality of structures 204 are provided.
  • the structures 204 are arranged in a one-dimensional direction.
  • the functional area 210 of the optical element 200 is a combination of the functional areas of the structures 204, and therefore, in the one-dimensional direction in which the structures 204 are juxtaposed, such as light from a line light source.
  • the optical element 200 can be made to function as a polarizer even for light having a large spread.
  • the optical element 200 can function as a polarizer.
  • the structures 204 are arranged in parallel so that there is no gap between the bottom surfaces of the dielectrics 202 of the structures 204. However, as shown in FIG. There may be a gap between the bottom surfaces of the body 202.
  • the structure 204 shown in FIGS. 11 and 12 is used as the structure 204.
  • the structure 204 has the structure shown in FIGS. 13, 14, and 15. There may be.
  • the structures 204 shown in FIG. 12 are juxtaposed in a two-dimensional direction.
  • the functional area 210 that functions as a polarizer and the non-functional area 211 that does not function as a polarizer are alternately provided, one of polarized light and non-polarized light depends on the incident position of light from the light source. Can be selectively output.
  • the illustrated configuration is merely an example, and the present invention is not limited to the configuration.
  • the numerical values, materials, and the like in the above-described embodiments are illustrative, and can be changed as appropriate.
  • the depolarizing element 3A can be omitted.

Abstract

There is provided a polarizer capable of increasing the light-extraction efficiency when non-polarized light is converted to light in a specified polarization state. The polarizer is provided with a substrate, a first dielectric part installed on the substrate, and a metal part installed on the first dielectric part, the first dielectric part being installed so as to decrease in size from the substrate toward the metal part.

Description

偏光子、偏光光学素子、光源および画像表示装置Polarizer, polarizing optical element, light source, and image display device
　本発明は、光を偏光させる偏光子に関する。 The present invention relates to a polarizer that polarizes light.
　近年、発光素子としてＬＥＤ（Light　Emitting　Diode）を有する光源を用いたプロジェクタが注目されている。このようなプロジェクタは、光源と、光源の出射光が入射される照明光学系と、照明光学系からの光を映像信号に応じて変調して出射する変調素子と、変調素子からの光をスクリーンに投射する投射光学系とを備えている。 In recent years, a projector using a light source having an LED (Light Emitting Diode) as a light emitting element has attracted attention. Such a projector includes a light source, an illumination optical system that receives light emitted from the light source, a modulation element that modulates and emits light from the illumination optical system according to a video signal, and light from the modulation element on a screen. And a projection optical system for projecting onto the screen.
　上記のプロジェクタでは、変調素子として液晶パネルなどの偏光依存性を有するものが使用されることがある。この場合、ＬＥＤの出射光は非偏光なので、ＬＥＤの出射光を効率良く投射光として利用するためには、非偏光が特定の偏光状態に変換される必要がある。 In the projector described above, a polarizing element such as a liquid crystal panel may be used as the modulation element. In this case, since the emitted light of the LED is non-polarized light, the non-polarized light needs to be converted into a specific polarization state in order to efficiently use the emitted light of the LED as the projection light.
　このため、光源には、ＬＥＤからの非偏光を特定の偏光状態の光に変換して出射する偏光光学素子が設けられることがある。このような偏光光学素子としては、光利用効率に優れ、薄型化が容易なワイヤグリッド偏光子を用いたものが注目されている。 For this reason, the light source may be provided with a polarizing optical element that converts non-polarized light from the LED into light having a specific polarization state and emits the light. As such a polarizing optical element, an element using a wire grid polarizer that is excellent in light utilization efficiency and can be easily reduced in thickness is attracting attention.
　図１は、ワイヤグリッド偏光子の一例を示す図である。図１に示すように、ワイヤグリッド偏光子では、基板１０１上に、線状の金属部材である金属ワイヤ１０２がグリッド（格子）状に複数配列されている。 FIG. 1 is a diagram showing an example of a wire grid polarizer. As shown in FIG. 1, in the wire grid polarizer, a plurality of metal wires 102, which are linear metal members, are arranged on a substrate 101 in a grid.
　ワイヤグリッド偏光子では、金属ワイヤ１０２が形成されている面に光が入射すると、その入射光１１１のうち、金属ワイヤ１０２の延伸方向に対して垂直な方向Ａに偏光した偏光成分であるＴＭ偏光は、ワイヤグリッド偏光子を透過して、透過光１１２として出射する。また、入射光１１１のうち、方向Ａと直交する方向Ｂに偏光した偏光成分であるＴＥ偏光は、ワイヤグリッド偏光子で反射して、反射光１１３として、光の入射側に戻される（特許文献１および２参照）。 In the wire grid polarizer, when light enters the surface on which the metal wire 102 is formed, TM polarized light that is a polarization component polarized in the direction A perpendicular to the extending direction of the metal wire 102 in the incident light 111. Passes through the wire grid polarizer and exits as transmitted light 112. In addition, TE polarized light that is a polarization component polarized in a direction B orthogonal to the direction A in the incident light 111 is reflected by a wire grid polarizer and returned to the light incident side as reflected light 113 (Patent Document). 1 and 2).
　図２および図３は、ワイヤグリッド偏光子を用いた偏光光学素子の一例を示す図である。 2 and 3 are diagrams showing an example of a polarizing optical element using a wire grid polarizer.
　図２に示す偏光光学素子は、ＬＥＤである発光素子３０１の上に設けられたλ／４板３０２と、λ／４板３０２の上に設けられたワイヤグリッド偏光子３０３とを有する。 The polarizing optical element shown in FIG. 2 includes a λ / 4 plate 302 provided on a light emitting element 301 that is an LED, and a wire grid polarizer 303 provided on the λ / 4 plate 302.
　図２に示す偏光光学素子では、発光素子３０１からの光がワイヤグリッド偏光子３０３に入射すると、入射光のうちのＴＭ偏光はワイヤグリッド偏光子３０３を透過して、偏光光学素子から出射され、入射光のうちのＴＥ偏光はワイヤグリッド偏光子３０３で反射する。この反射した光は、λ／４板３０２を介して発光素子３０１に入射し、発光素子３０１でさらに反射され、λ／４板３０２を介してワイヤグリッド偏光子３０３に再入射する。 In the polarizing optical element shown in FIG. 2, when light from the light emitting element 301 enters the wire grid polarizer 303, TM polarized light of the incident light is transmitted through the wire grid polarizer 303 and emitted from the polarizing optical element. The TE polarized light in the incident light is reflected by the wire grid polarizer 303. The reflected light enters the light emitting element 301 through the λ / 4 plate 302, is further reflected by the light emitting element 301, and reenters the wire grid polarizer 303 through the λ / 4 plate 302.
　ワイヤグリッド偏光子３０３に再入射された光は、λ／４板３０２を２回通過してＴＭ偏光となっているので、ワイヤグリッド偏光子３０３を介して透過して、偏光光学素子から出射される。これにより、発光素子３０１から出射された光がＴＭ偏光に変換されて出射されることになる。 The light re-entering the wire grid polarizer 303 passes through the λ / 4 plate 302 twice and becomes TM polarized light, so that it passes through the wire grid polarizer 303 and is emitted from the polarization optical element. The Thereby, the light emitted from the light emitting element 301 is converted into TM polarized light and emitted.
　また、図３に示す偏光光学素子は、λ／４板３０２の代わりに、光を非偏光に変換して出射する偏光解消素子３０２’を有する。 Further, the polarizing optical element shown in FIG. 3 has a depolarizing element 302 ′ that converts light into non-polarized light and emits it, instead of the λ / 4 plate 302.
　図３に示す偏光光学素子では、ワイヤグリッド偏光子３０３に再入射する光は、偏光解消素子３０２’を通過しているので、非偏光となっている。このため、再入射した光のうちＴＭ偏光はワイヤグリッド偏光子３０３を透過し、ＴＥ偏光はワイヤグリッド偏光子３０３でさらに反射される。このような反射が繰り返されることで、発光素子３０１から出射された光がＴＭ偏光に変換されて出射されることになる。 In the polarization optical element shown in FIG. 3, the light re-entering the wire grid polarizer 303 is unpolarized because it passes through the depolarization element 302 '. Therefore, TM polarized light of the re-incident light is transmitted through the wire grid polarizer 303, and TE polarized light is further reflected by the wire grid polarizer 303. By repeating such reflection, the light emitted from the light emitting element 301 is converted into TM polarized light and emitted.
特開２００６－３３０１７８号公報JP 2006-330178 A 特開２０１０－２３１２０３号公報JP 2010-231203 A
　上記のようなワイヤグリッド偏光子では、金属ワイヤ１０２間の空気と基板１０１との屈折率の差が大きいため、ＴＭ偏光が金属ワイヤ１０２間から基板１０１に入射したときに、そのＴＭ偏光の一部が反射されて、光の入射側に戻されてしまう。このため、光の取り出し効率が低いという問題がある。 In the wire grid polarizer as described above, since the refractive index difference between the air between the metal wires 102 and the substrate 101 is large, when TM polarized light is incident on the substrate 101 from between the metal wires 102, The part is reflected and returned to the light incident side. For this reason, there is a problem that the light extraction efficiency is low.
　なお、図２および図３で示したように、光の入射側に戻された光をワイヤグリッド偏光子に再入射させることで、光の損失を少なくすることはできる。しかしながら、反射時に金属ワイヤ１０２における吸収損失による光の減衰が生じるため、光の取り出し効率は十分ではない。 As shown in FIGS. 2 and 3, the light loss can be reduced by re-entering the light returned to the light incident side into the wire grid polarizer. However, since light attenuation occurs due to absorption loss in the metal wire 102 during reflection, the light extraction efficiency is not sufficient.
　本発明は、上記の問題点を鑑みてなされたものであり、非偏光を特定の偏光状態の光に変換する際の光の取り出し効率を高くすることが可能な偏光子、偏光光学素子、光源および画像表示装置を提供することを目的としている。 The present invention has been made in view of the above problems, and a polarizer, a polarizing optical element, and a light source capable of increasing light extraction efficiency when converting non-polarized light into light having a specific polarization state. And it aims at providing an image display device.
　本発明による第１の偏光子は、基板と、基板上に設けられた第１の誘電体部と、第１の誘電体部上に設けられた金属部と、を備え、第１の誘電体部は、基板から金属部に向かって小さくなるように設けられる。 A first polarizer according to the present invention includes a substrate, a first dielectric portion provided on the substrate, and a metal portion provided on the first dielectric portion, the first dielectric The portion is provided so as to become smaller from the substrate toward the metal portion.
　また、本発明による第２の偏光子は、基板と、基板上に設けられた第１の誘電体部と、第１の誘電体部上に設けられた金属部と、を備え、第１の誘電体部は、基板から金属部に向かって傾斜面を有し、第１の誘電体部の側面は、基板から金属部に向かって傾斜するように形成された傾斜面であり、第１の誘電体部の金属部が設けられた面は、第１の誘電部の基板が設けられた面より小さい。 A second polarizer according to the present invention includes a substrate, a first dielectric part provided on the substrate, and a metal part provided on the first dielectric part, The dielectric part has an inclined surface from the substrate toward the metal part, and the side surface of the first dielectric part is an inclined surface formed to incline from the substrate toward the metal part. The surface of the dielectric portion on which the metal portion is provided is smaller than the surface on which the substrate of the first dielectric portion is provided.
　また、本発明による偏光光学素子は、偏光子と、構造体上に設けられ、入射光の偏光状態を変化させて出射する偏光状態変換素子と、を有する。 The polarizing optical element according to the present invention includes a polarizer and a polarization state conversion element that is provided on the structure and emits light while changing the polarization state of incident light.
　また、本発明の光源は、偏光光学素子と、偏光光学素子に光を出射する発光素子と、を有する。 The light source of the present invention includes a polarizing optical element and a light emitting element that emits light to the polarizing optical element.
　また、本発明の画像表示装置は、光源を有する。 The image display device of the present invention has a light source.
　本発明によれば、非偏光を特定の偏光状態の光に変換する際の光の取り出し効率を高くすることが可能になる。 According to the present invention, it is possible to increase the light extraction efficiency when converting non-polarized light into light having a specific polarization state.
本発明の関連技術であるワイヤグリッド偏光子の構成を示す図である。It is a figure which shows the structure of the wire grid polarizer which is a related technique of this invention. 本発明の関連技術である偏光光学素子の一例を示す図である。It is a figure which shows an example of the polarizing optical element which is a related technique of this invention. 本発明の関連技術である偏光光学素子の他の例を示す図である。It is a figure which shows the other example of the polarizing optical element which is a related technique of this invention. 本発明の第１の実施形態の光源の構成を模式的に示す斜視図である。It is a perspective view which shows typically the structure of the light source of the 1st Embodiment of this invention. ワイヤグリッド偏光子の製造方法を説明するための工程図である。It is process drawing for demonstrating the manufacturing method of a wire grid polarizer. 本発明の第１の実施形態の光源を用いた画像表示装置の構成の一例を示す配置図である。1 is a layout diagram illustrating an example of a configuration of an image display device using a light source according to a first embodiment of the present invention. 本発明の第１の実施形態の光源を用いた画像表示装置の構成の一例を示す配置図である。1 is a layout diagram illustrating an example of a configuration of an image display device using a light source according to a first embodiment of the present invention. 本発明の第１の実施形態の光源における積算透過率の評価結果を示す図である。It is a figure which shows the evaluation result of the integrated transmittance | permeability in the light source of the 1st Embodiment of this invention. 本発明の第１の実施形態の光源の構成を模式的に示す斜視図である。It is a perspective view which shows typically the structure of the light source of the 1st Embodiment of this invention. 本発明の第２の実施形態の光源における積算透過率の評価結果を示す図である。It is a figure which shows the evaluation result of the integrated transmittance | permeability in the light source of the 2nd Embodiment of this invention. 本発明の第３の実施形態の光学素子の側面および上面を示す図である。It is a figure which shows the side surface and upper surface of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention. 本発明の第３の実施形態の光学素子の他の形状の一例を示す図である。It is a figure which shows an example of the other shape of the optical element of the 3rd Embodiment of this invention.
　以下、本発明の実施形態について図面を参照して説明する。なお、以下の説明では、同じ機能を有するものには同じ符号を付け、その説明を省略する場合がある。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, components having the same function may be denoted by the same reference numerals and description thereof may be omitted.
　図４は、本発明の第１の実施形態の光源を模式的に示す斜視図である。なお、実際の光源では、各層の厚さが非常に薄く、また各層の厚さの違いが大きいので、各層を正確なスケールや比率で図示するのは困難である。このため、図面では各層が実際の比率通りに描かれておらず、模式的に示されている。 FIG. 4 is a perspective view schematically showing the light source of the first embodiment of the present invention. In an actual light source, the thickness of each layer is very thin, and the difference in thickness between the layers is large, so it is difficult to illustrate each layer with an accurate scale and ratio. For this reason, in the drawings, the layers are not schematically drawn but are shown schematically.
　図４に示すように本実施形態の光源１０は、発光素子１と、発光素子１の上に設けられた偏光光学素子２とを有する。 As shown in FIG. 4, the light source 10 of this embodiment includes a light emitting element 1 and a polarizing optical element 2 provided on the light emitting element 1.
　発光素子１は、例えば、ＬＥＤであり、光を偏光光学素子２に出射する。なお、発光素子１から出射される光は、本実施形態では、非偏光であり、可視光であるとする。 The light emitting element 1 is, for example, an LED and emits light to the polarizing optical element 2. In addition, in this embodiment, the light radiate | emitted from the light emitting element 1 is non-polarized light, and assumes that it is visible light.
　偏光光学素子２は、発光素子１からの光を特定の偏光状態に変換して出射する。 The polarizing optical element 2 converts the light from the light emitting element 1 into a specific polarization state and emits it.
　より具体的には、偏光光学素子２は、発光素子１の上に設けられた波長板３と、波長板３の上に設けられたワイヤグリッド偏光子である偏光子４とを有する。なお、図４では、発光素子１と波長板３とが密着しているが、実際には、密着していなくてもよい。 More specifically, the polarizing optical element 2 includes a wave plate 3 provided on the light emitting element 1 and a polarizer 4 which is a wire grid polarizer provided on the wave plate 3. In FIG. 4, the light emitting element 1 and the wave plate 3 are in close contact with each other, but actually, they may not be in close contact.
　波長板３は、光の偏光状態を変化させる偏光状態変換素子の一例である。より具体的には、波長板３は、互いに直角な方向に振動する直線偏光の間にその光の１／４波長の位相差を生じさせることで、直線偏光を円偏光（楕円偏光）に変換し、円偏光（楕円偏光）を直線偏光に変換するλ／４板である。また、波長板３は、ゼロオーダー波長板であることが望ましい。 The wave plate 3 is an example of a polarization state conversion element that changes the polarization state of light. More specifically, the wave plate 3 converts the linearly polarized light into circularly polarized light (elliptical polarized light) by generating a phase difference of ¼ wavelength of the light between the linearly polarized light vibrating in directions perpendicular to each other. The λ / 4 plate converts circularly polarized light (elliptical polarized light) into linearly polarized light. The wave plate 3 is preferably a zero order wave plate.
　波長板３の材料としては、サファイアや水晶のような無機の異方性結晶、ポリカーボネートのような異方性フィルム、および、ナノ構造異方性媒体などが挙げられる。 Examples of the material of the wave plate 3 include inorganic anisotropic crystals such as sapphire and quartz, anisotropic films such as polycarbonate, and nanostructure anisotropic media.
　偏光子４は、基板１１と、その基板１１上に、第１誘電体層１２、金属層１３、第２誘電体層１４の順に積層されている複数の凸部１５とを有する。なお、第１誘電体層１２は、第１の誘電体部の一例であり、金属層１３は、金属部の一例であり、第２誘電体層１２は、第２の誘電体部の一例であり、各凸部１５は、構造体の一例である。また、本実施形態では、基板１１の上面をＸＹ平面とし、ＸＹ平面と直交する方向をＺ方向とする。 The polarizer 4 has a substrate 11 and a plurality of convex portions 15 laminated on the substrate 11 in the order of the first dielectric layer 12, the metal layer 13, and the second dielectric layer 14. The first dielectric layer 12 is an example of a first dielectric part, the metal layer 13 is an example of a metal part, and the second dielectric layer 12 is an example of a second dielectric part. Yes, each convex portion 15 is an example of a structure. In the present embodiment, the upper surface of the substrate 11 is the XY plane, and the direction orthogonal to the XY plane is the Z direction.
　基板１１は、発光素子１から出射される光の波長帯域において、実質的に透明な材料で形成される。基板１１の材料としては、例えば、石英ガラスおよびホウケイ酸クラウンのような光学ガラス、サファイアおよび水晶のような無機物結晶、ポリエーテルイミド樹脂およびポリスチレン樹脂のような透明プラスチックなどが挙げられる。 The substrate 11 is formed of a substantially transparent material in the wavelength band of light emitted from the light emitting element 1. Examples of the material of the substrate 11 include optical glass such as quartz glass and borosilicate crown, inorganic crystals such as sapphire and quartz, and transparent plastic such as polyetherimide resin and polystyrene resin.
　基板１１上の各凸部１５は、基板１１の上面内の第１方向であるＹ方向に延伸された線形形状を有する。また、複数の凸部１５は、グリッド状、より具体的には、第１方向とは異なる第２方向であるＸ方向に周期的に配置されている。 Each convex portion 15 on the substrate 11 has a linear shape extended in the Y direction, which is the first direction in the upper surface of the substrate 11. Further, the plurality of convex portions 15 are periodically arranged in a grid shape, more specifically, in the X direction, which is a second direction different from the first direction.
　各凸部１５の第１誘電体層１２は、基板１１から金属層１３に向かって、第１誘電体層１２の断面積が小さくなるテーパー構造（傾斜面）を有する。テーパー構造は、基板１１と第１誘電体層１２との接面において、第１誘電体層１２の幅が凸部１５の周期と同等になり、第１誘電体層１２の金属層１３と接する面と金属層１３の第１誘電体層１２と接する面とが同等な大きさになることが望ましい。また、テーパーは、線形、指数関数および放物線のような滑らかなものであればよい。 The first dielectric layer 12 of each convex portion 15 has a tapered structure (inclined surface) in which the cross-sectional area of the first dielectric layer 12 decreases from the substrate 11 toward the metal layer 13. In the taper structure, the width of the first dielectric layer 12 is equal to the period of the protrusions 15 on the contact surface between the substrate 11 and the first dielectric layer 12, and the metal layer 13 of the first dielectric layer 12 is in contact with the taper structure. It is desirable that the surface and the surface of the metal layer 13 in contact with the first dielectric layer 12 have the same size. The taper may be smooth as long as it is linear, exponential, or parabola.
　また、第１誘電体層１２は、例えば、１．５～２．０の屈折率を有し、その高さが１０ｎｍ～１５０ｎｍ程度である。また、第１誘電体層１２の材料は、特に限定されないが、例えば、酸化シリコン、酸化チタンおよび酸化アルミニウムのような酸化物、窒化シリコンのような窒化物、フッ化マグネシウムおよびフッ化カルシウムのようなフッ化物などの誘電体材料が挙げられる。 The first dielectric layer 12 has a refractive index of 1.5 to 2.0, for example, and a height of about 10 nm to 150 nm. The material of the first dielectric layer 12 is not particularly limited. For example, oxides such as silicon oxide, titanium oxide and aluminum oxide, nitrides such as silicon nitride, magnesium fluoride and calcium fluoride are used. And dielectric materials such as fluoride.
　第１誘電体層１２上に形成される金属層１３は、例えば、アルミニウム、銀、錫およびそれらの合金のような、発光素子１から出射される光の波長帯域において、光の反射率が高い材料で形成されることが望ましい。 The metal layer 13 formed on the first dielectric layer 12 has a high light reflectance in the wavelength band of light emitted from the light emitting element 1, such as aluminum, silver, tin, and alloys thereof. It is desirable to be formed of a material.
　また、金属層１３上に形成される第２誘電体層１４の材料は、特に限定されないが、例えば、酸化シリコン、酸化チタンおよび酸化アルミニウムのような酸化物、窒化シリコンのような窒化物、フッ化マグネシウムおよびフッ化カルシウムのようなフッ化物などの誘電体材料が挙げられる。 The material of the second dielectric layer 14 formed on the metal layer 13 is not particularly limited. For example, oxides such as silicon oxide, titanium oxide and aluminum oxide, nitrides such as silicon nitride, and fluorine are used. And dielectric materials such as fluorides such as magnesium fluoride and calcium fluoride.
　また、第２誘電体層１４は、例えば、１．０～２．０の屈折率を有し、高さが５０ｎｍ～２００ｎｍである。ＸＹ方向における、第２誘電体層１４の大きさは、金属層１３の大きさと同等であることが望ましい。 The second dielectric layer 14 has a refractive index of 1.0 to 2.0 and a height of 50 nm to 200 nm, for example. The size of the second dielectric layer 14 in the XY direction is preferably equal to the size of the metal layer 13.
　第２誘電体層１４は、波長板３と密着されている。なお、第２誘電体層１４と波長板３との間には、保護材や粘着材が挿入されていてもよい。 The second dielectric layer 14 is in close contact with the wave plate 3. A protective material or an adhesive material may be inserted between the second dielectric layer 14 and the wave plate 3.
　以上のように構成された光源１０において、発光素子１から出射された非偏光は、波長板３を介して偏光子４の凸部１５が形成された面に入射する。なお、非偏光は波長板３を通過しても非偏光であるので、偏光子４に入射する光も非偏光である。 In the light source 10 configured as described above, the non-polarized light emitted from the light emitting element 1 enters the surface on which the convex portion 15 of the polarizer 4 is formed via the wave plate 3. Since non-polarized light is non-polarized even after passing through the wave plate 3, light incident on the polarizer 4 is also non-polarized.
　偏光子４に入射した非偏光のうち、各凸部１５の延伸方向であるＹ方向に垂直な偏光成分であるＴＭ偏光は、各凸部１５を透過し、さらに基板１１を透過して出射される。 Of the non-polarized light that has entered the polarizer 4, TM polarized light, which is a polarization component perpendicular to the Y direction that is the extending direction of each convex portion 15, is transmitted through each convex portion 15 and further transmitted through the substrate 11 and emitted. The
　一方、偏光子４に入射した非偏光のうち、各凸部１５の延伸方向であるＹ方向に平行な偏光成分であるＴＥ偏光は、各凸部１５の金属層１３で反射する。この反射したＴＥ偏光は、波長板３を通過して円偏光となり、発光素子１で反射し、さらに波長板３を通過して、ＴＭ偏光となって偏光子４に再入射する。したがって、再入射した光は、偏光子４を透過して出射される。このため、偏光子４から出射される光は、特定の偏光状態を有するＴＭ偏光となる。 On the other hand, among the non-polarized light incident on the polarizer 4, TE polarized light that is a polarization component parallel to the Y direction that is the extending direction of each convex portion 15 is reflected by the metal layer 13 of each convex portion 15. The reflected TE polarized light passes through the wave plate 3 and becomes circularly polarized light, is reflected by the light emitting element 1, further passes through the wave plate 3, and becomes TM polarized light and reenters the polarizer 4. Therefore, the re-incident light is transmitted through the polarizer 4 and emitted. For this reason, the light emitted from the polarizer 4 becomes TM polarized light having a specific polarization state.
　このとき、波長板３と偏光子４との間に間隙があると、波長板３から偏光子４に入射されず、外周部から漏れる漏れ光が多くなる。このため、波長板３と偏光子４とが密着されている。 At this time, if there is a gap between the wave plate 3 and the polarizer 4, the light that does not enter the polarizer 4 from the wave plate 3 and leaks from the outer peripheral portion increases. For this reason, the wave plate 3 and the polarizer 4 are in close contact with each other.
　しかしながら、金属層１３の光が入射する側の入射側媒体の屈折率が金属ワイヤの屈折率の絶対値に近いほど、金属層１３によるＴＥ偏光の吸収率が増大して、ＴＥ偏光の反射率が低減する。このため、入射側媒体は、屈折率ができるだけ小さいものが望ましい。 However, as the refractive index of the incident-side medium on the light incident side of the metal layer 13 is closer to the absolute value of the refractive index of the metal wire, the TE-polarized light absorption by the metal layer 13 increases, and the TE-polarized light reflectance is increased. Is reduced. For this reason, it is desirable that the incident side medium has a refractive index as small as possible.
　金属層１３に波長板３が直接密着されると、入射側媒体が波長板３となる。波長板３の屈折率に対する自由度は低いので、入射側媒体が大きくなってしまう。このため、本実施形態では、金属層１３の上に１．０～２．０程度の屈折率を有する第２誘電体層１４を設けることで、入射側媒体の屈折率を低くして、ＴＥ偏光の反射率を向上させている。 When the wave plate 3 is in direct contact with the metal layer 13, the incident side medium becomes the wave plate 3. Since the degree of freedom with respect to the refractive index of the wave plate 3 is low, the incident side medium becomes large. For this reason, in the present embodiment, the second dielectric layer 14 having a refractive index of about 1.0 to 2.0 is provided on the metal layer 13, thereby reducing the refractive index of the incident side medium. The reflectance of polarized light is improved.
　また、基板１１と各凸部の間の媒体である間隙媒体との屈折率との差が大きいと、ＴＭ偏光が基板１１で反射する反射率が増大して、ＴＭ偏光の透過率が低減する。このため、本実施形態では、基板１１と金属層１３との間にテーパーを有する第１誘電体層１２を設けることで、第１誘電体層１２の金属層１３側では、第１誘電体層１２に比べて空気の占める体積を大きくし、第１誘電体層１２の基板１１側では、空気に比べて第１誘電体層１２の占める体積を大きくしている。このため、基板１１上のＸＹ平面と平行な平面における平均的な屈折率である有効屈折率は、基板１１から金属層１３に向かって連続的に変化していることになる。互いに異なる屈折率を有する媒質間の界面で発生するフレネル反射は、その媒質間の屈折率の差が小さいほど発生しづらくなるので、上記のように有効屈折率が基板１１から金属層１３に向かって連続的に変化していると、反射を軽減することが可能になり、ＴＭ偏光の透過率を向上させることが可能になる。 Also, if the difference in refractive index between the substrate 11 and the gap medium, which is a medium between the convex portions, is large, the reflectance at which the TM polarized light is reflected by the substrate 11 increases, and the transmittance of the TM polarized light decreases. . Therefore, in the present embodiment, by providing the first dielectric layer 12 having a taper between the substrate 11 and the metal layer 13, the first dielectric layer is formed on the metal layer 13 side of the first dielectric layer 12. The volume occupied by air is larger than 12 and the volume occupied by the first dielectric layer 12 is larger on the substrate 11 side of the first dielectric layer 12 than air. For this reason, the effective refractive index that is an average refractive index in a plane parallel to the XY plane on the substrate 11 continuously changes from the substrate 11 toward the metal layer 13. Fresnel reflection that occurs at the interface between media having different refractive indexes is less likely to occur as the difference in refractive index between the media is smaller. Therefore, the effective refractive index is directed from the substrate 11 toward the metal layer 13 as described above. If it changes continuously, it becomes possible to reduce reflection and to improve the transmittance of TM polarized light.
　図５は、図４に示す光源１０に含まれる偏光子４を製造する製造方法を説明するための図である。なお、以下で説明する製造方法は、単なる一例であって、これに限定されるものではない。 FIG. 5 is a diagram for explaining a manufacturing method for manufacturing the polarizer 4 included in the light source 10 shown in FIG. In addition, the manufacturing method demonstrated below is only an example, Comprising: It is not limited to this.
　先ず、図５（ａ）に示すように、例えば蒸着法を用いて、基板１１の上に第１誘電体層１２を形成し、その後、例えばスパッタリング製膜法を用いて、第１誘電体層１２の上に金属層１３を製膜し、さらに、金属層１３の上に第２誘電体層１４を製膜させる。さらに、第２誘電体層１４の上にレジスト層２１Ａを薄膜になるように積層する。 First, as shown in FIG. 5A, the first dielectric layer 12 is formed on the substrate 11 by using, for example, a vapor deposition method, and then the first dielectric layer is formed by using, for example, a sputtering film forming method. A metal layer 13 is formed on 12, and a second dielectric layer 14 is formed on the metal layer 13. Further, a resist layer 21A is laminated on the second dielectric layer 14 so as to be a thin film.
　その後、図５（ｂ）に示すように、レジスト層２１Ａをグリッド状にパターニングして、グリッド状に配置された複数のレジスト層２１Ｂを形成する。パターニングの方法は、特に限定されないが、例えば、マスク露光法である光リソグラフィー技術やインプリント法などが挙げられる。 Thereafter, as shown in FIG. 5B, the resist layer 21A is patterned in a grid shape to form a plurality of resist layers 21B arranged in a grid shape. The patterning method is not particularly limited, and examples thereof include a photolithography technique that is a mask exposure method, an imprint method, and the like.
　次に、図５（ｃ）に示すように、レジスト層２１Ｂをマスクとして、第２誘電体層１４、金属層１３および第１誘電体層１２を貫くようにエッチング処理を行い、グリッド状に配置された複数の凸部１５を形成する。このエッチング処理では、第１誘電体層１２がテーパー構造となるように、第１誘電体層１２を除去する。なお、エッチングの方法は、第１誘電体層１２、金属層１３および第２誘電体層１４の材料に応じて、ウェットエッチング法やドライエッチング法を用いることができる。 Next, as shown in FIG. 5C, using the resist layer 21B as a mask, etching is performed so as to penetrate the second dielectric layer 14, the metal layer 13, and the first dielectric layer 12, and arranged in a grid pattern. A plurality of convex portions 15 are formed. In this etching process, the first dielectric layer 12 is removed so that the first dielectric layer 12 has a tapered structure. As the etching method, a wet etching method or a dry etching method can be used depending on the materials of the first dielectric layer 12, the metal layer 13, and the second dielectric layer.
　そして、図５（ｄ）に示すように、レジスト層２１Ｂを酸素ラジカルと結合させて、ＣＯやＣＯ２などの気体状反応生成物に置換して除去する。 Then, as shown in FIG. 5D, the resist layer 21B is combined with oxygen radicals, and is replaced with a gaseous reaction product such as CO or CO 2 and removed.
　図６は、図４に示した光源１０を有する画像表示装置の構成の一例を示す配置図である。図６に示す画像表示装置は、光をスクリーンに投射してスクリーン上に画像を形成するプロジェクタである。 FIG. 6 is a layout diagram showing an example of the configuration of the image display apparatus having the light source 10 shown in FIG. The image display apparatus shown in FIG. 6 is a projector that projects light onto a screen to form an image on the screen.
　図６において、プロジェクタ５００は、光源５０１Ｒ、５０１Ｇおよび５０１Ｂと、光学素子５０２Ｒ、５０２Ｇおよび５０２Ｂと、液晶パネル５０３Ｒ、５０３Ｇおよび５０３Ｂと、クロスダイクロイックプリズム５０４と、投射光学系５０５とを備える。 6, the projector 500 includes light sources 501R, 501G, and 501B, optical elements 502R, 502G, and 502B, liquid crystal panels 503R, 503G, and 503B, a cross dichroic prism 504, and a projection optical system 505.
　光源５０１Ｒ、５０１Ｇおよび５０１Ｂのそれぞれは、図４に示した光源１０と同じ構造を有する。光源５０１Ｒ、５０１Ｇおよび５０１Ｂのそれぞれの発光素子１は、波長がそれぞれ異なる光を発生するものとする。以下、光源５０１Ｒから赤色（Ｒ）光が出射され、光源５０１Ｇから緑色（Ｇ）光が出射され、光源５０１Ｂから青色（Ｂ）光が出射されるものとする。 Each of the light sources 501R, 501G, and 501B has the same structure as the light source 10 shown in FIG. The light emitting elements 1 of the light sources 501R, 501G, and 501B generate light having different wavelengths. Hereinafter, it is assumed that red (R) light is emitted from the light source 501R, green (G) light is emitted from the light source 501G, and blue (B) light is emitted from the light source 501B.
　光学素子５０２Ｒ、５０２Ｇおよび５０２Ｂのそれぞれは、光源５０１Ｒ、５０１Ｇおよび５０１Ｂから発生した各色光を、液晶パネル５０３Ｒ、５０３Ｇおよび５０３Ｂのそれぞれに導いて入射する。 Each of the optical elements 502R, 502G, and 502B guides the respective color lights generated from the light sources 501R, 501G, and 501B to the liquid crystal panels 503R, 503G, and 503B, respectively, and enters the liquid crystal panels.
　液晶パネル５０３Ｒ、５０３Ｇおよび５０３Ｂは、入射された各色光を映像信号に応じて変調して出射する空間光変調素子である。 The liquid crystal panels 503R, 503G, and 503B are spatial light modulation elements that modulate and emit incident color light according to a video signal.
　クロスダイクロイックプリズム５０４は、液晶パネル５０３Ｒ、５０３Ｇおよび５０３Ｂのそれぞれから出射された各変調光を合成して出射する。 The cross dichroic prism 504 combines and outputs the modulated lights emitted from the liquid crystal panels 503R, 503G, and 503B.
　投射光学系５０５は、クロスダイクロイックプリズム５０４から出射された合成光をスクリーン６００に投射して、スクリーン６００上に映像信号に応じた映像を表示する。 The projection optical system 505 projects the combined light emitted from the cross dichroic prism 504 onto the screen 600 and displays an image corresponding to the video signal on the screen 600.
　図７は、本実施形態のプロジェクタの構成の別の例を示す配置図である。図７において、プロジェクタ５００’は、光源５０１Ｒ、５０１Ｇおよび５０１Ｂと、導光体５０６と、液晶パネル５０７と、投射光学系５０８とを有する。 FIG. 7 is a layout diagram showing another example of the configuration of the projector according to the present embodiment. In FIG. 7, the projector 500 ′ includes light sources 501 </ b> R, 501 </ b> G, and 501 </ b> B, a light guide 506, a liquid crystal panel 507, and a projection optical system 508.
　導光体５０６は、光源５０１Ｒ、５０１Ｇおよび５０１Ｂから発生した各色光を合成して液晶パネル５０７に出射する。 The light guide 506 synthesizes each color light generated from the light sources 501R, 501G, and 501B and outputs the combined light to the liquid crystal panel 507.
　液晶パネル５０７は、入射された合成光を映像信号に応じて変調して出射する空間光変調素子である。 The liquid crystal panel 507 is a spatial light modulation element that modulates incident combined light according to a video signal and emits the modulated light.
　投射光学系５０８は、液晶パネル５０７から出射された変調光をスクリーン６００に投射して、スクリーン６００上に映像信号に応じた映像を表示する。 The projection optical system 508 projects the modulated light emitted from the liquid crystal panel 507 onto the screen 600 and displays an image corresponding to the video signal on the screen 600.
　なお、図６および図７では、空間光変調素子として液晶パネルを用いたが、変調素子は液晶パネルに限らず適宜変更可能である。 In FIGS. 6 and 7, a liquid crystal panel is used as the spatial light modulation element. However, the modulation element is not limited to the liquid crystal panel and can be changed as appropriate.
　図８は、本実施形態の光源１０における積算透過率の評価結果を示す図である。ここで積算透過率とは、発光素子１から出射された光のうち、使用可能角度範囲に含まれる出射角で偏光子４から出射される光の割合を示す。使用可能角度範囲は、偏光変換素子から様々な方向に出射された光のうち、実際に使うことができる角度範囲のことであり、例えば、図６に示した画像表示装置において、光源５０１Ｒ、５０１Ｇおよび５０１Ｂから出射された光のうち、光学素子５０２Ｒ、５０２Ｇおよび５０２Ｂに取り込むことができる光の出射角度の範囲である。 FIG. 8 is a diagram showing an evaluation result of the integrated transmittance in the light source 10 of the present embodiment. Here, the integrated transmittance indicates a ratio of light emitted from the polarizer 4 at an emission angle included in the usable angle range in the light emitted from the light emitting element 1. The usable angle range is an angle range that can be actually used out of light emitted in various directions from the polarization conversion element. For example, in the image display apparatus illustrated in FIG. 6, the light sources 501R and 501G are used. Among the light emitted from 501B and 501B, the range of the emission angle of light that can be taken into the optical elements 502R, 502G, and 502B.
　なお、基板１１を屈折率１．５のガラス、第１誘電体層１２を屈折率１．８の誘電体、金属層１３をＡｌ、第２誘電体層１４を屈折率１．５の誘電体で形成した。 The substrate 11 is a glass having a refractive index of 1.5, the first dielectric layer 12 is a dielectric having a refractive index of 1.8, the metal layer 13 is Al, and the second dielectric layer 14 is a dielectric having a refractive index of 1.5. Formed with.
　金属層１３の幅を４２ｎｍ、高さを１４０ｎｍ、凸部１５の周期を１１０ｎｍとした。第１誘電体の高さを５０ｎｍ、幅を基板１１側で１１０ｎｍ、金属層１３側で４２ｎｍとした。第２誘電体の高さを１００ｎｍ、幅を４２ｎｍとした。さらに、波長板３は、水晶のゼロオーダーの一軸性１／４波長板とした。そして、発光素子１の出射光は、完全非偏光で配光分布はランバーシアンとし、発光素子１の反射率を１００％と仮定した。 The width of the metal layer 13 was 42 nm, the height was 140 nm, and the period of the convex portions 15 was 110 nm. The height of the first dielectric was 50 nm, the width was 110 nm on the substrate 11 side, and 42 nm on the metal layer 13 side. The height of the second dielectric was 100 nm and the width was 42 nm. Further, the wave plate 3 is a zero order uniaxial quarter wave plate of quartz. The light emitted from the light-emitting element 1 is assumed to be completely non-polarized, the light distribution is Lambertian, and the reflectance of the light-emitting element 1 is assumed to be 100%.
　図８では、Ｅは、ワイヤグリッド偏光子単独の評価結果、Ｆは光源１０の評価結果、Ｇは、図１で示した関連技術の光源の評価結果、Ｈは、発光素子１の出射光が全て偏光された出射されたときの結果である。 In FIG. 8, E is the evaluation result of the wire grid polarizer alone, F is the evaluation result of the light source 10, G is the evaluation result of the light source of the related technology shown in FIG. 1, and H is the output light of the light emitting element 1. This is the result when all polarized light is emitted.
　図８に示されたように、本実施形態の光源１０は、図１で示した関連技術の光源に比べて、積算透過率が１％程度向上している。 As shown in FIG. 8, the integrated light transmittance of the light source 10 of this embodiment is improved by about 1% compared to the light source of the related art shown in FIG.
　以上説明したように本実施形態によれば、第１誘電体層１２にテーパーが設けられているので、ＴＭ偏光の透過率を向上させることが可能になるので、非偏光を特定の偏光状態の光に変換する際の光の取り出し効率を高くすることが可能になる。 As described above, according to the present embodiment, since the first dielectric layer 12 is tapered, it is possible to improve the transmittance of TM polarized light. It is possible to increase the light extraction efficiency when converting to light.
　また、本実施形態では、金属層１３の上の第２誘電体層１４を設けているので、偏光子４を波長板３に密着させても、ＴＥ偏光の反射率の低下の抑制、または、ＴＥ偏光の反射率の向上が可能になる。したがって、漏れ光を抑制しつつ、ＴＥ偏光の反射率の低下の抑制、または、ＴＥ偏光の反射率の向上が可能になるので、非偏光を特定の偏光状態の光に変換する際の光の取り出し効率を高くすることが可能になる。 In the present embodiment, since the second dielectric layer 14 is provided on the metal layer 13, even if the polarizer 4 is brought into close contact with the wave plate 3, it is possible to suppress the decrease in the reflectance of TE-polarized light, or The reflectance of TE polarized light can be improved. Accordingly, it is possible to suppress a decrease in the reflectance of TE-polarized light or to improve the reflectance of TE-polarized light while suppressing leakage light, so that the light when converting non-polarized light into light of a specific polarization state can be obtained. The extraction efficiency can be increased.
　次に本発明の第２の実施形態について説明する。 Next, a second embodiment of the present invention will be described.
　図９は、本発明の第２の実施形態の光源を模式的に示す斜視図である。図９に示す本実施形態の光源１０Ａは、図４に示した光源１０に対して、波長板３の代わりに偏光解消素子３Ａを有する。 FIG. 9 is a perspective view schematically showing a light source according to the second embodiment of the present invention. A light source 10A of this embodiment shown in FIG. 9 has a depolarizing element 3A instead of the wave plate 3 with respect to the light source 10 shown in FIG.
　偏光解消素子３Ａは、光の偏光状態を変化させる偏光状態変換素子の一例である。より具体的には、偏光解消素子３Ａは、入射された光を非偏光にして出射するものである。 The depolarization element 3A is an example of a polarization state conversion element that changes the polarization state of light. More specifically, the depolarizing element 3A emits incident light as non-polarized light.
　偏光解消素子３Ａの材料としては、厚みが面内の位置に応じて異なる、サファイアや水晶のような無機の異方性結晶や、ポリカーボネートのような異方性フィルムが挙げられる。 Examples of the material for the depolarizing element 3A include inorganic anisotropic crystals such as sapphire and quartz, and anisotropic films such as polycarbonate, whose thickness varies depending on the position in the plane.
　なお、図９では、発光素子１と偏光解消素子３Ａとが密着しているが、実際には、密着していなくてもよい。 In FIG. 9, the light emitting element 1 and the depolarizing element 3 </ b> A are in close contact with each other, but actually, they may not be in close contact.
　以上のように構成された光源１０Ａにおいて、発光素子１から出射された非偏光は、偏光解消素子３Ａを介して偏光子４の凸部１５が形成された面に入射する。なお、非偏光は偏光解消素子３Ａを通過しても非偏光であるので、偏光子４に入射する光も非偏光である。 In the light source 10A configured as described above, the non-polarized light emitted from the light emitting element 1 enters the surface on which the convex portion 15 of the polarizer 4 is formed via the depolarizing element 3A. Since non-polarized light is non-polarized even after passing through the depolarizer 3A, the light incident on the polarizer 4 is also non-polarized.
　偏光子４に入射した非偏光のうち、各凸部１５の延伸方向であるＹ方向に垂直な偏光成分であるＴＭ偏光は、各凸部１５を透過し、さらに基板１１を透過して出射される。 Of the non-polarized light that has entered the polarizer 4, TM polarized light, which is a polarization component perpendicular to the Y direction that is the extending direction of each convex portion 15, is transmitted through each convex portion 15 and further transmitted through the substrate 11 and emitted. The
　一方、偏光子４に入射した非偏光のうち、各凸部１５の延伸方向であるＹ方向に平行な偏光成分であるＴＥ偏光は、各凸部１５の金属層１３で反射する。この反射したＴＥ偏光は、波長板３を通過して非偏光となり、発光素子１で反射し、さらに波長板３を通過して、非偏光のまま偏光子４に再入射する。したがって、再入射した光のうちＴＭ偏光は、偏光子４を透過して出射され、再入射した光のうちＴＥ偏光は再度反射される。 On the other hand, among the non-polarized light incident on the polarizer 4, TE polarized light that is a polarization component parallel to the Y direction that is the extending direction of each convex portion 15 is reflected by the metal layer 13 of each convex portion 15. The reflected TE-polarized light passes through the wave plate 3 to become non-polarized light, is reflected by the light emitting element 1, passes through the wave plate 3, and re-enters the polarizer 4 without being polarized. Therefore, TM polarized light out of the re-incident light is transmitted through the polarizer 4, and TE polarized light out of the re-incident light is reflected again.
　図１０は、本実施形態の光源１０Ａにおける積算透過率の評価結果を示す図である。なお、偏光解消素子３Ａは、入射光を完全な非偏光にするものと仮定し、他の各部材の構成は、第１の実施形態と同様としている。また、図１０において、Ｅは、ワイヤグリッド偏光子単独の評価結果、Ｆは光源１０Ａの評価結果、Ｇは、図１で示した関連技術の光源の評価結果、Ｈは、発光素子１の出射光が全て偏光された出射されたときの結果である。 FIG. 10 is a diagram showing an evaluation result of the integrated transmittance in the light source 10A of the present embodiment. The depolarizing element 3A is assumed to make incident light completely non-polarized, and the configuration of other members is the same as that of the first embodiment. 10, E is the evaluation result of the wire grid polarizer alone, F is the evaluation result of the light source 10A, G is the evaluation result of the light source of the related technology shown in FIG. 1, and H is the output of the light emitting element 1. This is the result when all the incident light is emitted in a polarized state.
　図１０に示すように、本実施形態の光源１０は、図１で示した関連技術の光源に比べて、積算透過率が向上していることがわかる。 As shown in FIG. 10, it can be seen that the integrated light transmittance of the light source 10 of this embodiment is improved as compared with the light source of the related art shown in FIG.
　次に本発明の他の実施形態について説明する。 Next, another embodiment of the present invention will be described.
　図１１は、本発明の第３の実施形態の光学素子の側面および上面を示す図である。図１１に示すように本実施形態の光学素子２００は、基板２０１と、基板２０１上に設けられた誘電体部２０２と、誘電体部２０２上に設けられた金属部２０３とを有する。なお、誘電体部２０２は、第１の誘電体部の一例であり、誘電体部２０２および金属部２０３は構造体２０４を構成する。また、本実施形態では、基板２０１の上面をＸＹ平面とし、ＸＹ平面と直交する方向をＺ方向とする。 FIG. 11 is a diagram showing a side surface and an upper surface of an optical element according to the third embodiment of the present invention. As shown in FIG. 11, the optical element 200 of the present embodiment includes a substrate 201, a dielectric part 202 provided on the substrate 201, and a metal part 203 provided on the dielectric part 202. The dielectric portion 202 is an example of a first dielectric portion, and the dielectric portion 202 and the metal portion 203 constitute a structure 204. In the present embodiment, the upper surface of the substrate 201 is the XY plane, and the direction orthogonal to the XY plane is the Z direction.
　誘電体部２０２は、基板２０１から金属部２０３に向かって小さくなる構造を有する。 The dielectric part 202 has a structure that decreases from the substrate 201 toward the metal part 203.
　より具体的には、誘電体部２０２の基板２０１と接する面である底面は、矩形であり、誘電体部２０２のＹ方向に沿った側面がテーパー構造を有する。 More specifically, the bottom surface that is a surface in contact with the substrate 201 of the dielectric portion 202 is rectangular, and the side surface along the Y direction of the dielectric portion 202 has a tapered structure.
　また、金属部２０３のＹ方向（反射偏光方向）の長さをＷ１、金属部２０３のＸ方向（透過偏光方向）の長さをＷ２とする。 Further, the length of the metal part 203 in the Y direction (reflection polarization direction) is W1, and the length of the metal part 203 in the X direction (transmission polarization direction) is W2.
　また、誘電体部２０２の金属部２０３と接する面である上面のＹ方向の長さをＷ１、誘電体部２０２の上面のＸ方向の長さをＷ２とする。このとき、長さＷ１が光学素子２００に入射される光の波長λより長く、長さＷ２が波長λよりも短いと、光学素子２００における機能領域２１０が偏光子として機能する。つまり、機能領域２１０に入射した入射光のうちＹ方向と直交する偏光成分であるＴＭ偏光が基板２０１を透過し、その入射光のうちＹ方向と平行な偏光成分であるＴＥ偏光は金属部２０３で反射する。 Also, the length in the Y direction of the upper surface, which is the surface in contact with the metal portion 203 of the dielectric portion 202, is W1, and the length in the X direction of the upper surface of the dielectric portion 202 is W2. At this time, when the length W1 is longer than the wavelength λ of the light incident on the optical element 200 and the length W2 is shorter than the wavelength λ, the functional region 210 in the optical element 200 functions as a polarizer. That is, TM polarized light, which is a polarization component orthogonal to the Y direction, of incident light incident on the functional region 210 is transmitted through the substrate 201, and TE polarized light, which is a polarization component parallel to the Y direction, of the incident light is the metal portion 203. Reflect on.
　機能領域２１０は、誘電体部２０２の上面の中心からＹ方向に±Ｗ１／２以内、かつ、誘電体部２０２の上面の中心からＸ方向に±（Ｗ２／２＋Ｓ）以内の範囲である。なお、Ｓは、光学素子２００に入射される光の波長λの半分λ／２である。 The functional region 210 is a range within ± W1 / 2 in the Y direction from the center of the upper surface of the dielectric part 202 and within ± (W2 / 2 + S) in the X direction from the center of the upper surface of the dielectric part 202. Note that S is half λ / 2 of the wavelength λ of light incident on the optical element 200.
　本実施形態でも、第１および第２の実施形態と同様に、光学素子２００が偏光子として機能し、誘電体部２０２が基板２０１から金属部２０３に向かって小さくなる構造を有しているので、ＴＭ偏光のフレネル反射を抑制することが可能になり、非偏光を特定の偏光状態の光に変換する際の光の取り出し効率を高くすることが可能になる。 Also in this embodiment, since the optical element 200 functions as a polarizer and the dielectric portion 202 decreases from the substrate 201 toward the metal portion 203 as in the first and second embodiments. , It becomes possible to suppress Fresnel reflection of TM polarized light, and to increase the light extraction efficiency when converting non-polarized light into light of a specific polarization state.
　なお、光学素子２００の形状は、図１１に示したような形状に限らず、適宜変更可能である。以下では、図１２～図１９は、光学素子２００の他の形状の一例を示す図である。 It should be noted that the shape of the optical element 200 is not limited to the shape shown in FIG. In the following, FIGS. 12 to 19 are diagrams showing examples of other shapes of the optical element 200. FIG.
　図１２の例では、誘電体部２０２は、基板２０１上のＸ方向を向いた側面に加えて、基板２０１上のＹ方向を向いた側面もテーパー構造を有する。 In the example of FIG. 12, in addition to the side surface facing the X direction on the substrate 201, the side surface facing the Y direction on the substrate 201 has a tapered structure.
　図１３の例では、誘電体２０２の底面および上面が楕円形状をしている。なお、誘電体２０２の底面および上面では、直軸がＹ方向に沿って設けられている。 In the example of FIG. 13, the bottom surface and the top surface of the dielectric 202 are elliptical. Note that, on the bottom surface and the top surface of the dielectric 202, the straight axis is provided along the Y direction.
　図１４の例では、誘電体２０２の側面が底面からある位置まで基板２０１に対して直交し、その位置からテーパー構造が設けられている。 In the example of FIG. 14, the side surface of the dielectric 202 is perpendicular to the substrate 201 from the bottom surface to a certain position, and a tapered structure is provided from that position.
　図１５の例では、誘電体２０２の側面が階段形状になっている。 In the example of FIG. 15, the side surface of the dielectric 202 has a staircase shape.
　図１６～図１９の例では、構造体２０４が複数設けられている。 In the examples of FIGS. 16 to 19, a plurality of structures 204 are provided.
　図１６の例では、構造体２０４が一次元方向に並設されている。この場合、光学素子２００の機能領域２１０は、各構造体２０４の機能領域を合わせたものとなるため、線光源からの光のように、構造体２０４が並設されている１次元方向に対して広がりを有する光に対しても、光学素子２００を偏光子として機能させることが可能になる。また、構造体２０４が一つの場合に比べて、ＴＭ偏光のフレネル反射の低減率を高くすることが可能になる。さらに、図１７に示すように、Ｙ方向の光の広がりに対して構造体２０４のＹ方向を十分長くすれば、面光源からの光のように、２次元方向に対して広がりを有する光に対しても、光学素子２００を偏光子として機能させることが可能になる。 In the example of FIG. 16, the structures 204 are arranged in a one-dimensional direction. In this case, the functional area 210 of the optical element 200 is a combination of the functional areas of the structures 204, and therefore, in the one-dimensional direction in which the structures 204 are juxtaposed, such as light from a line light source. Thus, the optical element 200 can be made to function as a polarizer even for light having a large spread. In addition, it is possible to increase the reduction rate of the TM polarized Fresnel reflection as compared with the case where there is one structure 204. Furthermore, as shown in FIG. 17, if the Y direction of the structure 204 is sufficiently long with respect to the spread of light in the Y direction, light having a spread in the two-dimensional direction, such as light from a surface light source, is obtained. In contrast, the optical element 200 can function as a polarizer.
　なお、図１６および図１７の例では、各構造体２０４の誘電体２０２の底面の間に間隙がないように、各構造体２０４が並設されていたが、図１８に示すように、誘電体２０２の底面の間に間隙があってもよい。 In the examples of FIGS. 16 and 17, the structures 204 are arranged in parallel so that there is no gap between the bottom surfaces of the dielectrics 202 of the structures 204. However, as shown in FIG. There may be a gap between the bottom surfaces of the body 202.
　また、図１６および図１７の例では、構造体２０４として、図１１や図１２に示す構造のものを用いているが、構造体２０４は図１３、図１４、図１５に示す構造のものであっても良い。 In the examples of FIGS. 16 and 17, the structure 204 shown in FIGS. 11 and 12 is used as the structure 204. However, the structure 204 has the structure shown in FIGS. 13, 14, and 15. There may be.
　図１９の例では、図１２で示した構造体２０４が２次元方向に並設されている。この場合、偏光子として機能する機能領域２１０と、偏光子として機能しない非機能領域２１１とが交互に設けられることになるので、光源からの光の入射位置に応じて、偏光および非偏光の一方を選択的に出力することが可能になる。 In the example of FIG. 19, the structures 204 shown in FIG. 12 are juxtaposed in a two-dimensional direction. In this case, since the functional area 210 that functions as a polarizer and the non-functional area 211 that does not function as a polarizer are alternately provided, one of polarized light and non-polarized light depends on the incident position of light from the light source. Can be selectively output.
　以上説明した各実施形態において、図示した構成は単なる一例であって、本発明はその構成に限定されるものではない。例えば、上記実施の形態における数値、材質などは例示的なものであり、適宜変更して実施することが可能である。 In each embodiment described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration. For example, the numerical values, materials, and the like in the above-described embodiments are illustrative, and can be changed as appropriate.
　例えば、図４に示した発光素子１の上面に光を非偏光にして反射する機能を持たせることで、偏光解消素子３Ａを含まない構成とすることができる。 For example, by providing the light emitting element 1 shown in FIG. 4 with a function of reflecting light with non-polarized light, the depolarizing element 3A can be omitted.
　この出願は、２０１１年９月２７日に出願された日本出願特願２０１１－２１１５０５号公報を基礎とする優先権を主張し、その開示の全てをここに取り込む。 This application claims priority based on Japanese Patent Application No. 2011-21505 filed on Sep. 27, 2011, the entire disclosure of which is incorporated herein.
　１　　　　発光素子
　２　　　　偏光光学素子
　３　　　　波長板
　３Ａ　　　偏光解消素子
　４　　　　ワイヤグリッド偏光子
　１１、２０１　　　基板
　１２　　　第１誘電体層
　１３　　　金属層
　１４　　　第２誘電体層
　１５　　　凸部
　２０２　　誘電体部
　２０３　　金属部
　２０４　　構造体 DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Polarization optical element 3 Wave plate 3A Depolarization element 4 Wire grid polarizer 11, 201 Substrate 12 1st dielectric layer 13 Metal layer 14 2nd dielectric layer 15 Convex part 202 Dielectric part 203 Metal part 204 Structure body

Claims (17)

  1. 　基板と、
    　前記基板上に設けられた第１の誘電体部と、
    　前記第１の誘電体部上に設けられた金属部と、を備え、
    　前記第１の誘電体部は、前記基板から前記金属部に向かって小さくなるように設けられる、偏光子。     A substrate,
    A first dielectric portion provided on the substrate;
    A metal part provided on the first dielectric part,
    The first dielectric part is a polarizer provided so as to become smaller from the substrate toward the metal part.
  2. 　請求項１に記載の偏光子において、
    　前記第１の誘電体部の側面に、前記基板から前記金属部に向かって傾斜面が形成されている、偏光子。     The polarizer according to claim 1,
    The polarizer which the inclined surface is formed in the side surface of the said 1st dielectric material part toward the said metal part from the said board | substrate.
  3. 　請求項２に記載の偏光子において、
    　前記傾斜面は、前記第１の誘電体部の側面のうち、少なくとも互いに対向する２つの側面に形成されている、偏光子。     The polarizer according to claim 2,
    The inclined surface is a polarizer that is formed on at least two side surfaces facing each other among the side surfaces of the first dielectric part.
  4. 　請求項２に記載の偏光子において、
    　前記傾斜面は、前記第１の誘電体部の全ての側面に形成されている、偏光子。     The polarizer according to claim 2,
    The inclined surface is a polarizer formed on all side surfaces of the first dielectric portion.
  5. 　請求項１ないし４のいずれか１項に記載の偏光子において、
    　前記第１の誘電体部と前記金属部とを備える構造体が前記基板上に複数形成されている、偏光子。     The polarizer according to any one of claims 1 to 4,
    A polarizer, wherein a plurality of structures each including the first dielectric part and the metal part are formed on the substrate.
  6. 　請求項５に記載の偏光子において、
    　前記複数の構造体は、前記基板上の１次元方向に並設されている、偏光子。     The polarizer according to claim 5,
    The plurality of structures are polarizers arranged in a one-dimensional direction on the substrate.
  7. 　請求項５に記載の偏光子において、
    　前記複数の構造体は、前記基板上の２次元方向に並設されている、偏光子。     The polarizer according to claim 5,
    The plurality of structures are polarizers arranged side by side in a two-dimensional direction on the substrate.
  8. 　請求項５ないし７のいずれか１項に記載の偏光子において、
    　前記複数の構造体は、前記第１の誘電体の前記基板と接する面が間隙なく並設されている、偏光子。     The polarizer according to any one of claims 5 to 7,
    The plurality of structures are polarizers in which surfaces of the first dielectric that are in contact with the substrate are juxtaposed without a gap.
  9. 　請求項１ないし８のいずれか１項に記載の偏光子において、
    　前記構造体は、前記金属部上に設けられた第２の誘電体部をさらに有する、偏光子。     The polarizer according to any one of claims 1 to 8,
    The structure is a polarizer, further including a second dielectric portion provided on the metal portion.
  10. 　請求項１ないし９に記載の偏光子において、
    　前記第１の誘電体部の前記金属部と接する面と、前記金属部の前記第１の誘電体部と接する面とが同じ大きさである、偏光子。     The polarizer according to any one of claims 1 to 9,
    A polarizer, wherein a surface of the first dielectric part in contact with the metal part and a surface of the metal part in contact with the first dielectric part have the same size.
  11. 　基板と、
    　前記基板上に設けられた第１の誘電体部と、
    　前記第１の誘電体部上に設けられた金属部と、を備え、
    　前記第１の誘電体部は、前記基板から前記金属部に向かって傾斜面を有し、
    　前記第１の誘電体部の側面は、前記基板から前記金属部に向かって傾斜するように形成された傾斜面であり、
    　前記第１の誘電体部の前記金属部が設けられた面は、前記第１の誘電部の前記基板が設けられた面より小さい、偏光子。     A substrate,
    A first dielectric portion provided on the substrate;
    A metal part provided on the first dielectric part,
    The first dielectric part has an inclined surface from the substrate toward the metal part,
    The side surface of the first dielectric part is an inclined surface formed to be inclined from the substrate toward the metal part,
    The surface of the first dielectric part provided with the metal part is smaller than the surface of the first dielectric part provided with the substrate.
  12. 　請求項１ないし１１のいずれか１項に記載の偏光子と、
    　前記構造体上に設けられ、入射光の偏光状態を変化させて出射する偏光状態変換素子と、を有する偏光光学素子。     The polarizer according to any one of claims 1 to 11,
    A polarization optical element having a polarization state conversion element that is provided on the structure and emits light by changing a polarization state of incident light.
  13. 　請求項１２に記載の偏光光学素子において、
    　前記構造体と前記偏光状態変換素子とが密着している、偏光光学素子。     The polarizing optical element according to claim 12,
    A polarizing optical element in which the structure and the polarization state conversion element are in close contact.
  14. 　請求項１２または１３に記載の偏光光学素子において、
    　前記偏光状態変換素子は、前記入射光に位相差を与えて出射する波長板である、偏光光学素子。     The polarizing optical element according to claim 12 or 13,
    The polarization state conversion element is a polarization optical element that is a wavelength plate that emits a phase difference to the incident light.
  15. 　請求項１２または１３に記載の偏光光学素子において、
    　前記偏光状態変換素子は、前記入射光を非偏光にして出射する偏光解消素子である、偏光光学素子。     The polarizing optical element according to claim 12 or 13,
    The polarization state conversion element is a polarization optical element that is a depolarization element that emits the incident light in a non-polarized state.
  16. 　請求項１２ないし１５のいずれか１項に記載の偏光光学素子と、
    　前記偏光光学素子に光を出射する発光素子と、を有する光源。     The polarizing optical element according to any one of claims 12 to 15,
    A light source that emits light to the polarizing optical element.
  17. 　請求項１６に記載の光源を有する画像表示装置。 An image display device having the light source according to claim 16.
PCT/JP2012/069768 2011-09-27 2012-08-02 Polarizer, polarizing optical element, light source, and image display device WO2013046921A1 (en)

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