JP7331556B2 - Volume hologram, head-mounted sensor device - Google Patents

Description

The present invention relates to volume holograms and head-mounted sensor devices.

2. Description of the Related Art Conventionally, there has been known a device that detects a line of sight by irradiating an eye with infrared light. Japanese Patent Laid-Open No. 2002-200002 describes a spectacles-type line-of-sight detection device. In this line-of-sight detection device, an example is disclosed in which a hologram optical element is used to deflect the optical path of infrared light.

Volume holograms have been conventionally used as hologram optical elements. A volume hologram has a predetermined wavelength range in which the diffraction efficiency is high, and there have been cases where the diffraction efficiency drops significantly for wavelengths outside the corresponding wavelength range. If the diffraction efficiency is low, only a very small portion of the diffracted light emitted from the light source to the volume hologram can be used. When the diffraction efficiency is low and the amount of diffracted light is insufficient, the amount of diffracted light can be increased by increasing the amount of light irradiated to the volume hologram. However, when the amount of light irradiated to the volume hologram is increased, noise light scattered by portions other than the volume hologram increases, and this noise light sometimes hinders accurate detection.

JP-A-2003-230539

SUMMARY OF THE INVENTION An object of the present invention is to provide a volume hologram and a head-mounted sensor device with a large amount of diffracted light.

The present invention solves the above problems by means of the following solutions. In order to facilitate understanding, reference numerals corresponding to the embodiments of the present invention will be used for explanation, but the present invention is not limited thereto.

A first invention is a deflection unit ( 30), the volume hologram (30) having a half width of 10 nm or more in the spectral distribution curve.

A second invention provides a volume hologram (30) according to the first invention, wherein Δn≧1.0, where t (μm) is the film thickness of the volume hologram (30) and Δn is the refractive index modulation amount. 86×10 ⁻⁶ t ³ −1.56×10 ⁻⁴ t ² +4.37×10 ⁻³ t−3.56×10 ⁻² are satisfied. .

A third invention is the volume hologram (30) according to the first invention or the second invention, wherein when the film thickness of the volume hologram (30) is t (μm) and the refractive index modulation amount is Δn, , Δn≧0.140t ^(−1.07) .

A fourth invention is the volume hologram (30) according to any one of the first invention to the third invention, wherein the emission angle of infrared light incident on the volume hologram (30) at an incident angle θ ₁ is θ ₂ ≧−0.200 _{θ 1} ² +θ ₁ +1.10×10 ² within the range of 0°≦θ ₁ ≦85° and 100°≦θ ₂ ≦260° , θ ₂ ≦−2.48×10 ⁻⁴ θ ₁ ³ +3.51×10 ⁻² θ ₁ ² −1.06 θ ₁ +2.48×10 ^{2 .} (30).

A fifth invention is the volume hologram (30) according to any one of the first invention to the fourth invention, wherein the emission angle of infrared light incident on the volume hologram (30) at an incident angle θ ₁ is θ ₂ ≧8.08×10 ⁻⁴ θ _{1 3} −0.173 θ ₁ ² within the range of ⁰ °≦θ ₁ ≦85° and 100°≦θ ₂ ≦260° A volume hologram (30) characterized by satisfying the relationship +13.0θ ₁ -2.15×10 ² .

A sixth invention is a head-mounted sensor device including the volume hologram (30) according to any one of the first invention to the fifth invention in a deflection section.

A seventh invention is the head-mounted sensor device according to the sixth invention, comprising an infrared light source (10) for irradiating the volume hologram (30) with detection light, wherein the volume hologram ( The half-value width of 30), the half-value width of the illumination light of the light source, and the diffraction efficiency of the volume hologram (30) are (diffraction efficiency of volume hologram)×(half-value width of volume hologram)/(illumination light of light source The head-mounted sensor device is characterized by satisfying the relationship of (half width of )>8%.

According to the present invention, it is possible to provide a volume hologram and a head-mounted sensor device with a large amount of diffracted light.

1 is a diagram showing an overview of a line-of-sight detection device 1, which is a first embodiment of a head-mounted sensor device using a volume hologram according to the present invention; FIG. 3 is a diagram showing a superimposed spectral distribution curve of the light source 10 and an example distribution of the diffraction efficiency of the volume hologram 30. FIG. It is a figure which shows simulation conditions. FIG. 10 is a diagram summarizing the results of a simulation in which the half-value width was obtained by changing the film thickness t and Δn; 5 is a graph of an approximation formula showing a preferable combination range of the film thickness t and Δn obtained from the half-value width; FIG. 10 is a diagram summarizing the results of a simulation in which the maximum value of diffraction efficiency was obtained by changing the film thickness t and Δn; 4 is a graph of an approximation formula showing a preferable combination range of film thickness t and Δn obtained from the maximum value of diffraction efficiency; It is a figure which shows the simulation conditions which paid its attention to an incident angle and an output angle. FIG. 10 is a diagram summarizing the results of a simulation in which the half-value width was obtained by changing the incident angle θ ₁ and the output angle θ ₂ ; 5 is a graph of an approximation formula showing a preferable combination range of the film thickness t and Δn obtained from the half-value width; FIG. 10 is a diagram summarizing the results of a simulation in which the maximum value of diffraction efficiency was obtained by changing the incident angle θ ₁ and the output angle θ ₂ ; 3 is a graph of an approximation formula showing a preferable combination range of the incident angle θ ₁ and the output angle θ ₂ obtained from the maximum value of diffraction efficiency.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing an overview of a line-of-sight detection device 1, which is a first embodiment of a head-mounted sensor device using a volume hologram according to the present invention.
Each figure shown below including FIG. 1 is a schematic diagram, and the size and shape of each part are shown exaggerated or omitted as appropriate for easy understanding.
Also, in the following description, specific numerical values, shapes, materials, and the like are shown and described, but these can be changed as appropriate.
It should be noted that the specific numerical values defined in the specification and claims should be treated as including a general error range. That is, the difference of about ±10% is substantially no difference, and the numerical value set in a range slightly exceeding the numerical range of the present invention is substantially the difference of the present invention. should be interpreted as being within range.

The line-of-sight detection device 1 includes a light source 10, an imaging unit 20, and a deflection unit 30, and is worn on the head of a human body. The line-of-sight detection device 1 irradiates the eye E with infrared light from the light source 10 via the deflection unit 30, and photographs the eye E with the imaging unit 20, thereby detecting the position of the pupil. Detect line of sight.

The light source 10 is an infrared LED that emits infrared light toward the deflection section 30 . Examples of infrared LEDs include those with peak wavelengths of 850 nm and 940 nm.

The photographing unit 20 is equipped with an imaging element as a light receiving unit for receiving infrared light from the light source 10 that is reflected from the eye E and reaches the photographing unit 20, and is a small infrared camera capable of photographing infrared light. be. Based on the image of the eye E captured by the imaging unit 20, the line of sight of the wearer is detected by a computing unit (not shown). A known method can be appropriately used as a specific method of line-of-sight detection.

The deflection unit 30 diffracts and deflects the infrared light from the light source 10 and directs it to the eye E of the observer. The infrared light deflected by the deflection section 30 is reflected by the surface of the eye E, and part of it is captured by the imaging section 20 .
The deflection unit 30 of this embodiment is configured using a volume hologram 30 . The deflector 30 is arranged over a support (not shown) such as a glass plate. In addition, instead of using a glass plate as a substrate, a substrate made of PET (polyethylene terephthalate) resin, PC (polycarbonate) resin, COP (cycloolefin polymer) resin, PVA (polyvinyl alcohol) resin, thiourethane resin, etc. is used. may be used. By configuring the line-of-sight detection device 1 in the form of, for example, eyeglasses, the deflector 30 can be arranged at a position corresponding to the lens portion of the eyeglasses. Since the deflection unit 30 configured by the volume hologram 30 is thin film, it is small and lightweight. In this embodiment, the deflection unit 30 is entirely composed of the volume hologram 30, so the same reference numeral 30 is used in the following description.

As the hologram-forming photosensitive material for forming the volume hologram 30, for example, a known photosensitive material for the volume hologram 30 such as a silver salt material, a dichromate gelatin emulsion, a photopolymerizable resin, or a photocrosslinkable resin is used. can do.

[Photosensitive material for hologram formation]
A hologram-forming photosensitive material according to the present invention contains a photopolymerizable monomer, a photopolymerization initiator, a sensitizing dye that sensitizes the photopolymerization initiator, and a binder resin, and the photopolymerizable monomer contains at least a photoradical polymerizable monomer and a photocationically polymerizable monomer.

<Photopolymerizable Monomer>
The photopolymerizable monomer in the present invention is a compound that undergoes polymerization or dimerization reaction upon irradiation with light and that can diffuse and move in the hologram recording layer.
Examples of the photopolymerizable monomer in the present invention include photoradical polymerizable monomers, photocationically polymerizable monomers, photodimerizable compounds, and the like, including at least photoradical polymerizable monomers and photocationically polymerizable monomers .
The radical photopolymerizable monomer and the cationic photopolymerizable monomer are described below.

(Photoradical polymerizable monomer)
As the photoradical polymerizable monomer used in the present invention, when a hologram recording layer is formed using the hologram-forming photosensitive material of the present invention, an active monomer generated from a photoradical polymerization initiator described later by, for example, laser irradiation or the like. The compound is not particularly limited as long as it is a compound that polymerizes by the action of radicals, but it is preferable to use a compound having at least one ethylenically unsaturated double bond in the molecule. Examples include unsaturated carboxylic acids, unsaturated carboxylic acid salts, esters of unsaturated carboxylic acids and aliphatic polyhydric alcohol compounds, and amide bonds of unsaturated carboxylic acids and aliphatic polyvalent amine compounds. .

Examples of the photoradical polymerizable monomers include methyl methacrylate, hydroxyethyl methacrylate, lauryl acrylate, N-acryloylmorpholine, 2-ethylhexyl carbitol acrylate, isobornyl acrylate, methoxypropylene glycol acrylate, and 1,6-hexanediol diacrylate. , tetraethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, acrylamide, methacrylamide, styrene, 2-bromostyrene, phenyl acrylate, 2-phenoxyethyl acrylate, 2,3-naphthalene dicarboxylic acid Acid (acryloxyethyl) monoester, methylphenoxyethyl acrylate, nonylphenoxyethyl acrylate, β-acryloxyethyl hydrogen phthalate, phenoxypolyethylene glycol acrylate, 2,4,6-tribromophenyl acrylate, diphenic acid (2-methacryloxy ethyl) monoester, benzyl acrylate, 2,3-dibromopropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-naphthyl acrylate, N-vinylcarbazole, 2-(9-carbazolyl)ethyl acrylate, triphenylmethylthio Acrylates, 2-(tricyclo[5,2,102.6]dibromodecylthio)ethyl acrylate, S-(1-naphthylmethyl)thioacrylate, dicyclopentanyl acrylate, methylenebisacrylamide, polyethylene glycol diacrylate, trimethylol Propane triacrylate, pentaerythritol triacrylate, diphenic acid (2-acryloxyethyl) (3-acryloxypropyl-2-hydroxy) diester, 2,3-naphthalenedicarboxylic acid (2-acryloxyethyl) (3-acryloxy) propyl-2-hydroxy) diester, 4,5-phenanthenedicarboxylic acid (2-acryloxyethyl)(3-acryloxypropyl-2-hydroxy) diester, dibromo neopentyl glycol diacrylate, dipentaerythritol hexaacrylate, 1 , 3-bis[2-acryloxy-3-(2,4,6-tribromophenoxy)propoxy]benzene, diethylenedithioglycol diacrylate, 2,2-bis(4-acryloxyethoxyphenyl)propane, bis(4 -acryloxydiethoxyphenyl)methane, bis(4-acryloxyethoxy-3,5-dibromophenyl)methane, 2,2-bis(4-acryloxyethoxyphenyl)propane, 2,2-bis(4-acryloxyphenyl)methane oxydiethoxyphenyl)propane, 2,2-bis(4-acryloxyethoxy-3,5-dibromophenyl)propane, bis(4-acryloxyethoxyphenyl)sulfone, bis(4-acryloxydiethoxyphenyl)sulfone , bis(4-acryloxypropoxyphenyl)sulfone, bis(4-acryloxyethoxy-3,5-dibromophenyl)sulfone, and compounds in which acrylate is changed to methacrylate, and JP-A-2-247205. and an ethylenically unsaturated double bond-containing compound containing at least two S atoms in the molecule as described in JP-A-2-261808. They can be mixed and used.

Moreover, the average refractive index of the radically photopolymerizable monomer is preferably larger than the average refractive index of the cationic photopolymerizable monomer described later, and is preferably larger by 0.02 or more. This is because if the difference in average refractive index between the radically photopolymerizable monomer and the cationic photopolymerizable monomer is smaller than the above value, the desired refractive index modulation amount (Δn) may not be obtained. .

(Photo cationic polymerizable monomer)
The cationic photopolymerizable monomer used in the present invention is a compound that undergoes cationic polymerization with a Bronsted acid or a Lewis acid generated by decomposition of a cationic photopolymerization initiator, which will be described later, when irradiated with energy. Examples thereof include cyclic ethers, thioethers and vinyl ethers having functional groups such as epoxy groups and oxetane groups.
Further, when a radically photopolymerizable monomer and a cationic photopolymerizable monomer are used in combination, the polymerization of the radically photopolymerizable monomer is preferably carried out in a composition having a relatively low viscosity. The photo-cationically polymerizable monomer is preferably liquid at room temperature.

Examples of the photocationically polymerizable monomer include diglycerol diether, pentaerythritol polydiglycidyl ether, 1,4-bis(2,3-epoxypropoxyperfluoroisopropyl)cyclohexane, sorbitol polyglycidyl ether, and 1,6-hexane. Diol glycidyl ether, polyethylene glycol diglycidyl ether, phenyl glycidyl ether and the like can be mentioned.

In the present invention, only one of the photocationically polymerizable monomers described above may be used, or two or more of them may be used in combination.

The total content of the photopolymerizable monomers in the hologram-forming photosensitive material of the present invention is preferably 8.5 to 85 parts by weight per 100 parts by weight of the total solid content of the hologram-forming photosensitive material. More preferably, it is 8.5 to 70 parts by mass. Here, the solid content refers to components other than the solvent, and the monomers that are liquid at room temperature are also included in the solid content.
This is because if the total content of the photopolymerizable monomers is less than the above range, a large refractive index modulation amount (Δn) cannot be obtained, and there is a possibility that a high-luminance volume hologram recording material cannot be obtained. be. On the other hand, if the content of the photopolymerizable monomer is larger than the above range, the content of the binder resin is relatively decreased, and the hologram recording layer may not be retained.

Further, in the photopolymerizable monomer in the hologram-forming photosensitive material of the present invention, the content ratio of the photoradical polymerizable monomer and the photocationically polymerizable monomer is set to 100 parts by mass of the photoradical polymerizable monomer. The content of the organic monomer is preferably within the range of 30 to 90 parts by mass, more preferably within the range of 50 to 80 parts by mass.

<Photoinitiator>
As the photopolymerization initiator constituting the hologram-forming photosensitive material of the present invention, a photoradical polymerization initiator and a photocationic polymerization initiator can be used.

(Photoradical polymerization initiator)
Photoradical polymerization initiators used in the present invention include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocenes, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives. and the like, and more specifically, 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3′,4,4′-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl -5-isoxazolone, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name Irgacure 651, manufactured by BASF) ), 1-hydroxy-cyclohexyl-phenyl-ketone (trade name Irgacure 184, manufactured by BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (trade name Irgacure 369, BASF), bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium (trade name Irgacure 784, BASF Corporation), etc., but are not limited to these.

Examples of photocationic polymerization initiators include sulfonic acid esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η6-benzene)(η5-cyclopentadienyl ) Iron (II) and the like, more specifically benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosiphthalimide and the like, but are not limited to these.

Aromatic iodonium salts, aromatic sulfonium salts, aromatic diazonium salts, aromatic phosphonium salts, triazine compounds, iron arene complexes, etc. are exemplified as photoradical polymerization initiators and photocationic polymerization initiators. and more specifically, chlorides, bromides, borofluorides, hexafluorophosphate salts of iodonium such as diphenyliodonium, ditolyliodonium, bis(p-tert-butylphenyl)iodonium, bis(p-chlorophenyl)iodonium, Iodonium salts such as hexafluoroantimonate salts, sulfonium chlorides such as triphenylsulfonium, 4-tert-butyltriphenylsulfonium, tris(4-methylphenyl)sulfonium, bromides, borofluorides, hexafluorophosphate salts, hexafluoro sulfonium salts such as antimonate salts, 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 2-phenyl-4,6-bis(trichloromethyl)-1,3,5-triazine, 2,4,6-substituted-1,3,5-triazine compounds such as 2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine, including but not limited to isn't it.

From the viewpoint of stabilizing the recorded hologram, the photopolymerization initiator is preferably one that is decomposed after the hologram is recorded.

The content of the photopolymerization initiator in the hologram-forming photosensitive material of the present invention is preferably 0.04 to 6.5 parts by weight per 100 parts by weight of the total solid content of the hologram-forming photosensitive material. It is more preferably 8 to 5.0 parts by mass.
This is because if the content of the photopolymerization initiator is less than the above range, the photopolymerizable monomer described above may not be sufficiently polymerized, and the desired refractive index modulation amount (Δn) may not be obtained. . On the other hand, if the amount is more than the above range, the unreacted photopolymerization initiator may deteriorate the hologram properties.

<Sensitizing dye>
The sensitizing dye in the present invention is generally a component that absorbs light and has the function of increasing the sensitivity of the photopolymerization initiator to recording light. This is because the hologram-forming photosensitive material becomes active with visible light by using a sensitizing dye, and it becomes possible to record a hologram using a visible laser beam.

Sensitizing dyes used in the present invention include thiopyrylium salt dyes, merocyanine dyes, quinoline dyes, styrylquinoline dyes, coumarin dyes, ketocoumarin dyes, thioxanthene dyes, xanthene dyes, oxonol dyes, Cyanine dyes, rhodamine dyes, pyrylium ion dyes, cyclopentanone dyes, cyclohexanone dyes, diphenyliodonium ion dyes and the like can be mentioned. Specific examples of cyanine dyes and merocyanine dyes include 3,3′-dicarboxyethyl-2,2′-thiocyanine bromide and 1-carboxymethyl-1′-carboxyethyl-2,2′-quinocyanine bromide. , 1,3′-diethyl-2,2′-quinothiacyanine iodide, 3-ethyl-5-[(3-ethyl-2(3H)-benzothiazolylidene)ethylidene]-2-thioxo-4- oxazolidine, 3,9-diethyl-3′-carboxymethyl-2,2′-thiacarbocyanine iodine salt, and specific examples of coumarin-based dyes and ketocoumarin-based dyes include 3-(2′-benzo imidazole)-7-diethylaminocoumarin, 3,3′-carbonylbis(7-diethylaminocoumarin), 3,3′-carbonylbiscoumarin, 3,3′-carbonylbis(5,7-dimethoxycoumarin), 3,3 '-Carbonylbis(7-acetoxycoumarin) and the like, but are not limited thereto.

When high transparency is required for the volume hologram recording material described later, it is preferable to use a material that is easily decolorized due to decomposition or the like during the heating process or the light irradiation process after the interference exposure process. In general, dyes that are easily decomposed by light are preferred. By leaving it under room light or sunlight for several hours to several days, the pigment in the volume hologram recording material is decomposed and does not have an absorption wavelength range in the visible light range, thereby obtaining a highly transparent volume hologram recording material. Because you can.

The content of the sensitizing dye is preferably 0.001 to 2.0 parts by mass, more preferably 0.001 to 1.2 parts by mass, based on 100 parts by mass of the total solid content of the photosensitive material for forming a hologram. is more preferred.
If the content of the sensitizing dye is more than the above range, when high transparency is required, the dye may not be sufficiently decomposed by light irradiation, resulting in a colored hologram recording layer. On the other hand, if the amount is less than the above range, the sensitivity of the photopolymerization initiator cannot be sufficiently sensitized, and the hologram-forming photosensitive material may become inactive to visible light.

<Binder resin>
The binder resin has the function of improving the film-forming property and the uniformity of the film thickness of the hologram recording layer, and stabilizing the hologram formed by polymerization by light irradiation. It contributes to an increase in the heat resistance and the improvement of mechanical properties.
As the binder resin used in the present invention, one or more selected from thermoplastic resins and thermosetting resins are preferably used. Among them, it is preferable to use at least a thermoplastic resin, and it is preferable to use a thermoplastic resin and a thermosetting resin together from the viewpoint of increasing the refractive index modulation amount (Δn) and improving heat resistance and mechanical properties.

(Thermoplastic resin)
Examples of thermoplastic resins include polyvinyl acetate, polyvinyl butyrate, polyvinyl formal, polyvinyl carbazole, polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polymethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polymethacrylonitrile, Polyethyl methacrylate, polybutyl methacrylate, polyacrylonitrile, poly-1,2-dichloroethylene, ethylene-vinyl acetate copolymer, syndiotactic polymethyl methacrylate, poly-α-vinyl naphthalate, polycarbonate, cellulose acetate, cellulose triacetate , cellulose acetate butyrate, polystyrene, poly-α-methylstyrene, poly-o-methylstyrene, poly-p-methylstyrene, poly-p-phenylstyrene, poly-2,5-dichlorostyrene, poly-p-chloro Styrene, poly-2,5-dichlorostyrene, polyarylate, polysulfone, polyethersulfone, styrene-acrylonitrile copolymer, styrene-divinylbenzene copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer Polymer, ABS resin, polyethylene, polyvinyl chloride, polypropylene, polyethylene terephthalate, polyvinylpyrrolidone, polyvinylidene chloride, hydrogenated styrene-butadiene-styrene copolymer, transparent polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, (meth) Copolymers of acrylic acid cycloaliphatic esters and methyl (meth)acrylate, and the like are included.
A thermoplastic resin can be used individually by 1 type or in combination of 2 or more types.

Among the thermoplastic resins used in the binder resin of the present invention, it is preferable to contain a polyacrylic acid ester from the viewpoint of increasing the amount of refractive index modulation (Δn).

Polyacrylic acid esters used in the present invention include, for example, polymethyl acrylate, polyethyl acrylate, poly n-propyl acrylate, poly n-butyl acrylate, polybenzyl acrylate, poly n-hexyl acrylate, polyisopropyl acrylate, polyisobutyl Acrylates, poly-t-butyl acrylate, polycyclohexyl acrylate, polyphenyl acrylate, poly-1-phenylethyl acrylate, poly-2-phenylethyl acrylate, polyfurfuryl acrylate, polydiphenylmethyl acrylate, polypentachlorophenyl acrylate, polynaphthyl acrylate, etc. is mentioned. The poly(meth)acrylic acid ester may further contain a hydrolyzate of the poly(meth)acrylic acid ester. The thermoplastic resin used for the binder resin in the present invention is, among others, polymethyl methacrylate, and polymethyl methacrylate and poly(meth)acrylic acid in terms of increasing the amount of refractive index modulation (Δn) and storage stability. Copolymers of esters are preferred.

The weight-average molecular weight of the thermoplastic resin used for the binder resin in the present invention is in the range of 20,000 to 150,000 in terms of diffusion mobility of the photopolymerizable monomer during hologram recording and high-temperature storage stability. is preferably in the range of 80,000 to 150,000, and more preferably in the range of 120,000 to 140,000.
The weight-average molecular weight in the present invention refers to the polystyrene-equivalent value of gel permeation chromatography (GPC) measurement.

The glass transition temperature (Tg) of the thermoplastic resin used for the binder resin in the present invention is preferably within the range of 60°C to 150°C, more preferably within the range of 70°C to 120°C.
If the glass transition temperature (Tg) is higher than the above range, the diffusion mobility of the photopolymerizable monomer is poor, the desired refractive index modulation amount (Δn) cannot be obtained, and a volume hologram recording material with high brightness cannot be obtained. Because it is possible. On the other hand, if the glass transition temperature (Tg) is lower than the above range, the binder resin softens and the interference fringes are disturbed under high-temperature storage, and the desired refractive index modulation amount (Δn) may not be obtained. Because there is
The glass transition temperature (Tg) can be measured using a differential thermal analyzer (DSC) or the like.

(Thermosetting resin)
When a thermosetting resin is used as the binder resin in the present invention, the strength of the hologram recording layer is increased, the volume hologram recording characteristics are improved, and a stable layer structure can be formed by curing in the heating process. Also, some of the functional groups of the thermosetting resin can interact with some of the functional groups of the photopolymerizable monomer by light irradiation to form chemical bonds. In this case, since the photopolymerizable monomer is fixed by the light irradiation step after the volume hologram recording, the strength of the volume hologram recording material can be increased.

The thermosetting resin used for the binder resin in the present invention is not particularly limited, and monomers, oligomers and polymers having thermosetting groups can be preferably used.
Examples of the thermosetting resin include compounds containing hydroxyl groups, mercapto groups, carboxyl groups, amino groups, epoxy groups, oxetane groups, isocyanate groups, carbodiimide groups, oxazine groups, metal alkoxides, and the like. can. In the present invention, among others, it is more preferable to use a compound containing an epoxy group and an oxetane group, and more preferably to use an epoxy group-containing compound. The epoxy group-containing compound used in the present invention is not particularly limited as long as it is a resin containing one or more epoxy groups in one molecule.

Among the above compounds having epoxy groups, examples of monofunctional epoxy compounds having one epoxy group include phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and allyl glycidyl ether. Ether, 1,2-butylene oxide, 1,3-butadiene monoxide, 1,2-epoxidedecane, epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide, especially containing polymerizable unsaturated bonds Examples thereof include 3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexene oxide, 3-vinylcyclohexene oxide, glycidyl (meth)acrylate and the like.

Examples of polyfunctional epoxy compounds having two or more epoxy groups include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, and brominated bisphenol F diglycidyl. Ether, brominated bisphenol S diglycidyl ether, epoxy novolak resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3′,4 '-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide , 4-vinylepoxycyclohexane, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, 3,4-epoxy-6-methylcyclohexyl-3′,4′-epoxy-6′-methylcyclohexanecarboxylate, Methylenebis(3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylenebis(3,4-epoxycyclohexanecarboxylate), dioctyl epoxyhexahydrophthalate , di-2-ethylhexyl epoxyhexahydrophthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8-diepoxyoctane, 1,2,5,6-diepoxycyclooctane and the like. be done.
In addition, epoxy group-containing polymers are also preferably used. The epoxy group-containing polymer includes, for example, a copolymer using a monomer having an epoxy group or a glycidyl group as a copolymerization component. Examples of the monomer having an epoxy group or a glycidyl group include glycidyl (meth)acrylate and glycidyl esters of α,β-unsaturated carboxylic acids such as glycidyl maleate.
These epoxy compounds may be used individually by 1 type, and may use 2 or more types together.

The weight average molecular weight of the thermosetting resin used for the binder resin in the present invention is preferably in the range of 5000 to 100000, and being in the range of 10000 to 50000 improves the refractive index modulation amount (Δn). It is more preferable from the viewpoint of performance and the film strength of the hologram recording layer.

When a thermoplastic resin and a thermosetting resin are used together as a binder resin, the compounding ratio of the thermoplastic resin and the thermosetting resin is determined from the viewpoint of improving the refractive index modulation amount (Δn) and strength of the volume hologram recording medium. , The thermoplastic resin / thermosetting resin in mass ratio is preferably in the range of 50/50 to 90/10, more preferably in the range of 60/40 to 90/10, 70/30 to More preferably, it is in the range of 80/20.

The content of the binder resin in the hologram-forming photosensitive material of the present invention is 100 parts by mass of the total solid content of the hologram-forming photosensitive material from the viewpoint of improving the refractive index modulation amount (Δn) and strength of the volume hologram recording material. is preferably 1 to 40 parts by mass, more preferably 25 to 35 parts by mass.

<Other ingredients>
The hologram-forming photosensitive material of the present invention may optionally contain fine particles, thermal polymerization inhibitors, silane coupling agents, colorants, etc., as long as the effects of the present invention are not impaired.
For example, fine particles are preferably used to impart good foil tearability.
Examples of fine particles that can be used include organic fine particles containing low-density polyethylene, high-density polyethylene, polypropylene, poly(meth)acryl as a resin skeleton, and inorganic particles such as silica, mica, talc, and titania. You may use 1 type or in mixture of 2 or more types of microparticles|fine-particles. Among the above, fluorine-containing fine particles, which are fine particles of a fluorine-containing resin in which some or all of the hydrogen atoms in the resin skeleton or side chains of the organic fine particles are substituted with fluorine atoms, or titania fine particles are preferable. .

The hologram-forming photosensitive material of the present invention may optionally be coated with a solvent. If the hologram-forming photosensitive material contains a component that is liquid at room temperature, the coating solvent may not be necessary at all.
Examples of the solvent include ketone solvents such as methyl ethyl ketone, acetone and cyclohexanone; ester solvents such as ethyl acetate, butyl acetate and ethylene glycol diacetate; aromatic solvents such as toluene and xylene; alcohol solvents such as methanol, ethanol and propanol; ether solvents such as tetrahydrofuran and dioxane; halogen solvents such as dichloromethane and chloroform;

The materials described above are merely examples of materials used as materials for forming a volume hologram, and the materials are not limited to these.
Further, the formation of the volume hologram 30 using such a hologram-forming photosensitive material can be performed in the same manner as a conventionally known method of forming a reflection hologram.

In addition, infrared light has an extremely narrow wavelength band and is substantially single wavelength light, and the volume hologram 30 also has wavelength selectivity. , the volume hologram 30 of the deflection unit 30 can be constructed so as to have almost no optical effect. Therefore, the line-of-sight detection device 1 of the present embodiment can be made smaller and lighter, and the deflection section 30 can be passed through.

As described above, in the line-of-sight detection device 1 of the present embodiment, by using the volume hologram 30 in the deflector 30, it is possible to obtain the excellent effects described above. If the band of the infrared light emitted by the light source 10 is narrowed and the volume hologram 30 capable of selectively diffracting and reflecting only the light in this band is used, the transparency is high and the line of sight can be detected appropriately. It is possible.

However, when the volume hologram 30 is used for deflecting infrared light in the line-of-sight detection device, if the diffraction efficiency is low, only a small portion of the diffracted light emitted from the light source to the volume hologram can be used. When the diffraction efficiency is low and the amount of diffracted light is insufficient, the amount of diffracted light can be increased by increasing the amount of light irradiated to the volume hologram. However, when the amount of light irradiated to the volume hologram is increased, noise light scattered by portions other than the volume hologram increases, and this noise light sometimes hinders accurate detection.

FIG. 2 is a diagram showing a spectral distribution curve of the light source 10 and an example distribution of the diffraction efficiency of the volume hologram 30 superimposed. The horizontal axis of FIG. 2 indicates the wavelength, and the vertical axis indicates the amount of infrared light from the light source 10 and the diffraction efficiency of the volume hologram 30 . FIG. 2 shows the distribution of infrared light emitted from the LED with a peak of 940 nm, the distribution of the diffraction efficiency of the volume hologram 30 with a half-value width of 10 nm, and the distribution of the diffraction efficiency of the volume hologram 30 with a half-value width of 70 nm. was written together.
As can be seen from this figure, even if the diffraction efficiency at the peak wavelength of the volume hologram is high, if the half-value width is less than 10 nm, the diffraction efficiency of the light of 935 nm or less and the light of 945 nm or more of the LED light is very small. As a result, the utilization efficiency is low when considering the entire infrared light emitted from the LED. Therefore, the half width of the volume hologram is preferably 10 nm or more.

More preferably, the volume hologram 30 has a spectral distribution curve with a half width of 20 nm or more.
More preferably, the volume hologram 30 has a half width of 30 nm or more in the spectral distribution curve.
More preferably, the volume hologram 30 has a spectral distribution curve with a half width of 50 nm or more.
More preferably, the volume hologram 30 has a half width of 70 nm or more in the spectral distribution curve.

Further, it is desirable that the half-value width of the volume hologram, the half-value width of the irradiation light from the light source, and the diffraction efficiency of the volume hologram in the spectral distribution curve satisfy the following relationship.
(Peak diffraction efficiency of volume hologram) x (Half width of volume hologram)/(Half width of irradiation light from light source) > 8%
By satisfying this relationship, the amount of diffracted light can be equal to or greater than the amount of interface-reflected light on the front and back surfaces of the transparent substrate, and sufficient sensitivity to noise light due to interface reflection can be obtained.
More preferably, it is desirable to satisfy the following relationship.
(Peak diffraction efficiency of volume hologram)×(Half width of volume hologram)/(Half width of irradiation light of light source)>10%
More preferably, it is desirable to satisfy the following relationship.
(Peak diffraction efficiency of volume hologram)×(Half width of volume hologram)/(Half width of irradiation light of light source)>15%
More preferably, it is desirable to satisfy the following relationship.
(Peak diffraction efficiency of volume hologram)×(Half width of volume hologram)/(Half width of irradiation light of light source)>20%

Next, a more specific configuration of the volume hologram 30 having a wide half width in the spectral distribution curve as described above will be described.
Since the half-value width of the diffracted light of the volume hologram 30 is considered to be greatly affected by the film thickness and the refractive index modulation amount Δn, these optimum ranges are defined first.
FIG. 3 is a diagram showing simulation conditions. FIG. 3(a) shows a list of simulation conditions, and FIG. 3(b) shows the conditions of the incident angle and the outgoing angle.
Here, the volume hologram 30 was simulated under the conditions shown in FIG. 3, and the effects of the film thickness and the refractive index modulation amount Δn on the half-value width were investigated. The amount of refractive index modulation Δn varies greatly depending on the selection and composition of materials before exposure, but can be changed depending on the exposure conditions, so it is possible to obtain a desired value. Note that the simulation results shown below use the average values of the P-polarized light and the S-polarized light.

The reflection hologram was simulated based on Kogelnik's Coupled Wave theory (The Bell System Technical Journal Vol.48, No.9, pp.2909-2947 (Nov.1969)).
The diffraction efficiency η of the reflection hologram is given by the following equation (A) when the absorption in the medium can be ignored.

η=1/[1+(1−ξ ² /ν ² )/sinh ² {√(ν ² −ξ ² )}] (A)
where ν and ξ are given by

ν=πtΔn/{λ√(cos θ _R ·cos θ _S )}
ξ=t/2×( _kRz +Kz _{-kSz )}
however,
t: Thickness of photosensitive material λ: Wavelength in vacuum θ _R : Angle between incident light and hologram surface normal vector θ _S : Angle between diffracted light and hologram surface normal vector k _Rz : Wave vector hologram of incident light Component in the direction normal to the surface k _Sz : Component of the wave vector of the diffracted light in the direction normal to the hologram surface K _z : Component of the diffraction grating vector in the direction normal to the hologram surface Δn : Amplitude of refractive index modulation of the hologram medium n : Hologram medium is the average refractive index of

Here, the wave vector k of the light is given by |k|=2πn/λ, and the diffraction grating vector K is a vector perpendicular to the interference fringe plane of the volume hologram. , |K|=2π/Λ.

(Half width simulation with film thickness t and Δn as variables)
FIG. 4 is a diagram summarizing the results of a simulation in which the half-value width was obtained by changing the film thickness t and Δn. In FIG. 4, 15 types of film thickness t and 20 types of Δn are combined, and the results of 300 types of simulations in total are summarized.
As can be seen from FIG. 4, a thinner film thickness t is desirable and a higher Δn value is desirable, but it is difficult to quantitatively grasp them. Therefore, from the results shown in FIG. 4, a preferable range of the combination of the film thickness t and Δn was mathematically expressed.
Specifically, the half-value width shown in FIG. 4 can be divided into a plurality of regions within the numerical range. We collected the data and found an approximation that represents the data group. As the boundaries, boundaries with half widths of 10 nm, 20 nm, 30 nm, 50 nm, and 70 nm were set.

FIG. 5 is a graph of an approximation formula showing a preferable combination range of the film thickness t and Δn obtained from the half width.
FIG. 5 also shows the results of polynomial approximation performed for each of the half-value widths of 10 nm, 20 nm, 30 nm, 50 nm, and 70 nm, which are the boundary values described above.

From the approximation result with a half width of 10 nm,
Δn≧1.86×10 ⁻⁶ t ³ −1.56×10 ⁻⁴ t ² +4.37×10 ⁻³ t−3.56×10 ⁻²
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the half width can be 10 nm or more.
However, since Δn cannot be a negative value, Δn=0 when Δn<0 in the above equation.

More desirably, from the approximation result with a half width of 20 nm,
Δn≧4.72×10 ⁻⁶ t ³ −3.62×10 ⁻⁴ t ² +9.60×10 ⁻³ t−6.38×10 ⁻²
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the half width can be 20 nm or more.
However, in the above formula, if Δn<0, then Δn=0.

More desirably, from the approximation result with a half width of 30 nm,
Δn≧1.10×10 ⁻⁵ t ³ −7.57×10 ⁻⁴ t ² +1.70×10 ⁻² t−8.52×10 ⁻²
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the half width can be 30 nm or more.
However, in the above formula, if Δn<0, then Δn=0.

More desirably, from the approximation result with a half width of 50 nm,
Δn≧9.11×10 ⁻⁶ t ³ −6.08×10 ⁻⁴ t ² +1.32×10 ⁻² t−1.73×10 ⁻²
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the half width can be 50 nm or more.
However, in the above formula, if Δn<0, then Δn=0.

More desirably, from the approximation result of the half width of 70 nm,
Δn≧9.75×10 ⁻⁸ t ⁵ −9.55×10 ⁻⁶ t ⁴ −3.60×10 ⁻⁴ t ³ −6.53×10 ⁻³ t ² +5.66×10 ⁻² t− 9.22× ^10-2
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the half width can be 70 nm or more.
However, in the above formula, if Δn<0, then Δn=0.

(Diffraction efficiency simulation with film thickness t and Δn as variables)
When the film thickness t and Δn are changed, not only the half-value width described above but also the diffraction efficiency is affected. Therefore, considering the diffraction efficiency, the appropriate range of the film thickness t and Δn is further limited.
FIG. 6 is a diagram summarizing the results of a simulation in which the maximum value of diffraction efficiency was obtained by changing the film thickness t and Δn. As in the case of FIG. 5, FIG. 6 also summarizes the results of a total of 300 types of simulations performed by combining 15 types of film thickness t and 20 types of Δn.
From FIG. 6, it can be seen that a thicker film thickness t is desirable and a higher Δn value is desirable, but it is difficult to grasp them quantitatively. Therefore, as in the case of FIG. 5, a preferable range of the combination of the film thickness t and Δn was formulated from the results shown in FIG.
Specifically, the boundaries were set such that the maximum value of the diffraction efficiency was 0.2, 0.4, 0.6, and 0.8.

FIG. 7 is a graph of an approximation formula showing a preferable combination range of the film thickness t and Δn obtained from the maximum value of the diffraction efficiency.
FIG. 7 also shows the results of polynomial approximation for each of the maximum diffraction efficiency values of 0.2, 0.4, 0.6, and 0.8, which are the boundary values described above.

From the approximation result of the maximum diffraction efficiency of 0.2,
Δn≧0.140t ^(-1.07)
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum diffraction efficiency can be 0.2 or more.

More preferably, from the approximation result of the maximum diffraction efficiency of 0.4,
Δn≧0.259t ^(−1.12)
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum value of the diffraction efficiency can be 0.4 or more.

More preferably, from the approximation result of the maximum diffraction efficiency of 0.6,
Δn≧0.324t ^(−1.06)
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum diffraction efficiency can be 0.6 or more.

More preferably, from the approximation result of the maximum diffraction efficiency of 0.8,
Δn≧0.473t ^(−1.07)
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum value of diffraction efficiency can be 0.8 or more.

(Half width simulation with the incident angle θ ₁ and the output angle θ ₂ as variables)
In the simulations described above, the incident and exit angles were fixed at 0° and 120°, respectively. This incident angle of 0° and outgoing angle of 120° is one of the most suitable combinations, assuming the head-mounted line-of-sight detection device 1 . However, of course, the combination of the incident angle and the outgoing angle is not limited to this, and can be appropriately changed in design. Therefore, a simulation was performed assuming that the incident angle and the output angle are changed.

FIG. 8 is a diagram showing simulation conditions focusing on the incident angle and the outgoing angle. FIG. 8(a) shows a list of simulation conditions, and FIG. 8(b) shows a state in which the incident angle _θ1 and the outgoing angle _θ2 are changed.
Here, the volume hologram 30 was simulated under the conditions shown in FIG. 8, and the effects of the incident angle θ ₁ and the output angle θ ₂ on the half-value width were investigated.

FIG. 9 is a diagram summarizing the results of a simulation in which the half-value width was obtained by changing the incident angle _θ1 and the output angle _θ2 . FIG. 9 summarizes the results of a total of 306 simulations performed by combining 18 types of incident angle θ ₁ from 0° to 85° and 17 types of output angle θ ₂ from 100° to 260°.
Looking at FIG. 9, the larger the incident angle θ ₁ (closer to 85°), the wider the half-value width, and the smaller the output angle θ ₂ (closer to 100°), the wider the half-value width. I understand that it can be done, but it is difficult to grasp it quantitatively. Therefore, from the results shown in FIG. 9, a preferable range for the combination of the incident angle _.theta.1 and the outgoing angle _.theta.2 was mathematically expressed in the same manner as the case of the film thickness t and .DELTA.n described above. As the boundaries, the boundaries with the half-value widths of 28 nm, 30 nm, 32 nm, and ₃₄ nm were set. It exists in two areas. Therefore, there are two approximation formulas with the half-value width of 15 nm as the boundary.

FIG. 10 is a graph of an approximation formula showing a preferable combination range of the film thickness t and Δn obtained from the half width.
Two half widths of 28 nm (28 nm-A, 28 nm-B) that are the boundary values described above,
Two half widths of 30 nm (30 nm-A, 30 nm-B), 32 nm, and 34 nm
The results of polynomial approximation for each of the are also shown in FIG.

From the results of the half width of 28 nm, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260°,
θ ₂ ≧−0.200 _{θ 1} ² +θ ₁ +1.10×10 ²
and,
θ ₂ ≦−2.48×10 ⁻⁴ θ ₁ ³ +3.51×10 ⁻² θ ₁ ² −1.06 _{θ 1} +2.48×10 ²
It can be said that it is desirable to satisfy both relationships. By satisfying this relationship, the half width can be 28 nm or more.

Further, from the result of the half width of 30 nm, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260°,
θ ₂ ≧−6.67×10 ⁻³ θ ₁ ³ +0.143 θ ₁ ² −0.976 _{θ 1} +1.41×10 ²
and,
θ ₂ ≦−2.02×10 ⁻⁴ θ ₁ ³ +2.75×10 ⁻² θ ₁ ² −0.599 _{θ 1} +2.16×10 ²
It can be said that it is desirable to satisfy both relationships. By satisfying this relationship, the half width can be 30 nm or more.

Further, from the result of the half width of 32 nm, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260°,
θ ₂ ≦9.29×10 ⁻⁶ θ ₁ ⁵ −2.83×10 ^{−3 θ 1 4 +0.337 θ 1 3 −19.6 θ 1 2} ₊ ^{5.59 ×} _{10 2} ^θ ₁ −6.03×10 ³
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the half width can be 32 nm or more.

Further, from the result of the half width of 34 nm, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260°,
θ ₂ ≦1.90×10 ⁻³ θ ₁ ³ −0.431 θ ₁ ² +32.9 θ ₁ −6.45×10 ²
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the half width can be 34 nm or more.

(Diffraction Efficiency Simulation with Incident Angle _θ1 and Output Angle _θ2 as Variables)
When the incident angle θ ₁ and the exit angle θ ₂ change, not only the half-value width mentioned above but also the diffraction efficiency is affected. Therefore, considering the diffraction efficiency, the appropriate range of the incident angle _θ1 and the output angle _θ2 is further limited.
FIG. 11 is a diagram summarizing the results of a simulation in which the maximum value of diffraction efficiency was obtained by changing the incident angle _θ1 and the output angle _θ2 . 11, 18 types of incident angle _θ1 from 0° to 85° and 17 types of output angle _θ2 from 100° to 260° were combined in the same manner as in FIG. 9, for a total of 306 types of simulations. I am summarizing the results.
Looking at FIG. 11, it can be seen that a smaller incident angle _θ1 (closer to 0°) is desirable, and a larger outgoing angle _θ2 (closer to 260°) is desirable. difficult to do Therefore, as in the case of FIG. 9, from the results shown in FIG. 11, the preferable range of the combination of the incident angle _.theta.1 and the outgoing angle _.theta.2 was formulated.
Specifically, the boundaries were set such that the maximum value of the diffraction efficiency was 0.6, 0.7, 0.8, and 0.9.

FIG. 12 is a graph of an approximation formula showing a preferable combination range of the incident angle θ ₁ and the output angle θ ₂ obtained from the maximum diffraction efficiency.
FIG. 12 also shows the results of polynomial approximation of the maximum diffraction efficiency values 0.6, 0.7, 0.8, and 0.9, which are the boundary values described above.

From the approximation result of the maximum diffraction efficiency value of 0.6, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260°,
θ ₂ ≧8.08×10 ⁻⁴ θ ₁ ³ −0.173 θ ₁ ² +13.0 _{θ 1} −2.15×10 ²
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum diffraction efficiency can be 0.6 or more.

More desirably, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260° from the approximation result of the maximum diffraction efficiency value of 0.7,
θ ₂ ≧6.94×10 ⁻⁴ θ ₁ ³ −0.137 _{θ 1} ² +9.27 θ ₁ −75.1
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum diffraction efficiency can be 0.7 or more.

More preferably, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260° from the approximation result of the maximum diffraction efficiency value of 0.8,
θ ₂ ≧3.44×10 ⁻⁴ θ ₁ ³ −6.30×10 ⁻² θ ₁ ² +3.82 θ ₁ +91.0
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum value of diffraction efficiency can be 0.8 or more.

More preferably, within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260° from the approximation result of the maximum diffraction efficiency value of 0.9,
θ ₂ ≧3.52×10 ⁻⁴ θ ₁ ³ −4.89×10 ⁻² θ ₁ ² +1.03 _{θ 1} +2.80×10 ²
It can be said that it is desirable to satisfy the relationship of By satisfying this relationship, the maximum diffraction efficiency can be 0.9 or more.

As for the volume hologram 30 used in the deflection unit 30 in this embodiment, the preferable range of the film thickness t and Δn and the preferable range of the incident angle θ ₁ and the output angle θ ₂ are appropriately combined to obtain an optimal volume hologram 30 for the usage conditions. A volume hologram 30 can be used.
In order to measure the film thickness of an actually produced volume hologram, it is preferable to observe the cross section with an SEM. As a method for measuring Δn, simulation calculation of diffraction efficiency is performed based on measurement results of film thickness, diffraction angle, and wavelength, and Δn is calculated from fitting with the measurement result of diffraction efficiency.

As described above, the line-of-sight detection device 1 of the present embodiment uses the volume hologram 30 in the deflection unit 30, and the half width of the diffracted light is 10 nm or more. Is possible. Further, since the volume hologram 30 used in the deflection unit 30 of the present embodiment is within the preferable ranges of the film thickness t and Δn and the preferable ranges of the incident angle θ ₁ and the output angle θ ₂ described above, the half width is A wide volume hologram 30 with good diffraction efficiency can be realized.

(deformed form)
Various modifications and changes are possible without being limited to the embodiments described above, and they are also within the scope of the present invention.

(1) In the embodiments, each numerical range defined as a desirable range does not have to be satisfied in the entire area of the volume hologram. For example, the angle of incidence and the angle of emergence with respect to the volume hologram may not satisfy the desired numerical range over the entire area of the volume hologram. For example, it is preferable that the center of the line of sight (the center of the volume hologram) satisfies the conditions of the angle range defined this time.

(2) In the embodiment, an example in which the volume hologram 30 is applied to a head-mounted display device has been described. For example, the volume hologram of the present invention may be used in a display device that is not worn on the head.

(3) In the embodiment, an example in which the volume hologram 30 is arranged in the optical path between the light source 10 and the eye E has been described. Not limited to this, for example, a volume hologram may be arranged between the imaging unit as the light receiving unit and the eye.

In addition, although each embodiment and modification can also be combined and used suitably, detailed description is abbreviate|omitted. Moreover, the present invention is not limited to each embodiment described above.

1 line-of-sight detection device 10 light source 20 imaging unit 30 deflection unit (volume hologram)

Claims (6)

A volume hologram placed in an optical path between at least one of an infrared light source and a light receiving unit and an eye of a sensing target and used as a deflection unit for deflecting the direction of infrared light,
The spectral distribution curve has a half width of 30 nm or more ,
When the emission angle of the infrared light incident on the volume hologram at the incident angle θ ₁ is θ ₂ ,
Within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260°,
θ ₂ ≧−6.67×10 ⁻³ θ ₁ ³ +0.143 θ ₁ ² −0.976 _{θ 1} +1.41×10 ²
and,
θ ₂ ≦−2.02×10 ⁻⁴ θ ₁ ³ +2.75×10 ⁻² θ ₁ ² −0.599 _{θ 1} +2.16×10 ²
A volume hologram that satisfies both relationships . The volume hologram according to claim 1,
When the film thickness of the volume hologram is t (μm) and the refractive index modulation amount is Δn,
Δn≧1.86×10 ⁻⁶ t ³ −1.56×10 ⁻⁴ t ² +4.37×10 ⁻³ t−3.56×10 ⁻²
satisfying the relationship of
A volume hologram characterized by In the volume hologram according to claim 1 or claim 2,
When the film thickness of the volume hologram is t (μm) and the refractive index modulation amount is Δn,
Δn≧0.140t ^(-1.07)
satisfying the relationship of
A volume hologram characterized by In the volume hologram according to any one of claims 1 to 3 ,
When the emission angle of the infrared light incident on the volume hologram at the incident angle θ ₁ is θ ₂ ,
Within the ranges of 0° ≤ θ ₁ ≤ 85° and 100° ≤ θ ₂ ≤ 260°,
θ ₂ ≧8.08×10 ⁻⁴ θ ₁ ³ −0.173 θ ₁ ² +13.0 _{θ 1} −2.15×10 ²
satisfying the relationship of
A volume hologram characterized by A head-mounted sensor device comprising the volume hologram according to any one of claims 1 to 4 in a deflection section. In the head-mounted sensor device according to claim 5 ,
An infrared light source that irradiates the volume hologram with detection light,
The half-value width of the volume hologram in the spectral distribution curve, the half-value width of the irradiation light of the infrared light source, and the peak diffraction efficiency of the volume hologram are:
( Peak diffraction efficiency of volume hologram) × (Half width of volume hologram) / (Half width of irradiation light of infrared light source) > 8%
satisfying the relationship of
A head-mounted sensor device characterized by:

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