KR20220035761A - Holographic optical element and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a holographic optical element and a method of manufacturing the same. Specifically, the present invention relates to a holographic optical element and a method of manufacturing the same. Specifically, the material of the photosensitive sheet applied to the holographic optical element is adjusted, and the incident angle of the reference beam is continuously adjusted during the recording process of the interference pattern. It relates to a holographic optical device that improves the reproducible angle of the device and a method of manufacturing the same.

Description

Holographic optical element and manufacturing method thereof {HOLOGRAPHIC OPTICAL ELEMENT AND MANUFACTURING METHOD THEREOF}

The present invention relates to a holographic optical element and a method of manufacturing the same. Specifically, the present invention relates to a holographic optical element and a method of manufacturing the same. Specifically, the material of the photosensitive sheet applied to the holographic optical element is adjusted, and the incident angle of the reference beam is continuously adjusted during the recording process of the interference pattern. It relates to a holographic optical device that improves the reproducible angle of the device and a method of manufacturing the same.

In general, holograms use a coherent light source to record the interference pattern of an object beam and reference beam containing image information on a photosensitive material, and the interference pattern is recorded on the recorded photosensitive material. This refers to a technology that reproduces image information recorded on photosensitive material by irradiating the same reproduction beam as the reference beam used during the photosensitive material. Since photosensitive materials with recorded interference patterns reproduce image information using diffraction instead of reflection or refraction, these photosensitive materials are also classified as a type of diffraction optical elements (DOEs).

Holographic optical elements increase the thickness of the optical element as an easy way to improve diffraction efficiency. However, as the thickness of the optical element increases, the irradiation angle of the reproduction beam that can emit the diffraction beam increases. There is a problem of narrowing.

However, in order to apply it to HUD, AR/VR glass or sensors, the diffraction efficiency must be improved, which causes the problem of increasing the thickness of the holographic optical element.

Figure 1 is a schematic diagram showing the ranges of the reproduction beam and diffraction beam of a holographic optical device according to the prior art. As the angle of incidence of the reproduction beam of the holographic optical element narrows as shown in Figure 1, there is a problem in that the angle of the reproduction beam must be precisely adjusted to emit a diffraction beam. Therefore, a holographic optical element with a wide reproduction angle and high diffraction efficiency is required. There was a need for technological development.

The technical problem to be achieved by the present invention is to provide a holographic optical element and a manufacturing method thereof that improve the irradiation angle of the reproduction beam that enables the operation of the holographic optical element and improve the diffraction efficiency of the diffracted beam of the reproduction beam.

However, the problem to be solved by the present invention is not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

One embodiment of the present invention is a holographic optical element in which an interference pattern is recorded due to the interference phenomenon of a reference beam incident on one side of a photosensitive sheet at a predetermined angle of incidence and an object beam incident on the other side of the photosensitive sheet, wherein an interference pattern is recorded at the incident angle. A holographic optical device is provided, wherein the diffraction efficiency of a diffraction beam with respect to a reproduction beam irradiated at a predetermined angle is 30% or more.

According to one embodiment of the present invention, the reference beam may be continuously incident at a predetermined angle based on the incident angle.

According to an exemplary embodiment of the present invention, the reference beam may be continuously incident at an angle of -11° or more and +11° or less based on the incident angle.

According to an exemplary embodiment of the present invention, the regenerative beam may be irradiated at an angle of -11° or more and +11° or less based on the incident angle.

One embodiment of the present invention includes the steps of incident a reference beam at a predetermined angle of incidence on one side of the photosensitive sheet and incident an object beam on the other side of the photosensitive sheet; and recording an interference pattern caused by interference between the reference beam and the object beam on the photosensitive sheet, wherein the diffraction efficiency of the diffracted beam for the reproduction beam irradiated at a predetermined angle with respect to the incident angle is 30. % or more, and provides a method for manufacturing a holographic optical element.

According to one embodiment of the present invention, the reference beam may be continuously incident at a predetermined angle based on the incident angle.

According to one embodiment of the present invention, the step of bleaching the photosensitive sheet on which the interference pattern is recorded by irradiating light having a wavelength in the visible to ultraviolet range may be further included.

The holographic optical element according to an embodiment of the present invention improves diffraction efficiency without adjusting the thickness, increases the reproduction operation angle, and realizes excellent diffraction performance with a thin thickness, thereby realizing miniaturization of the device to which the holographic optical element is applied. there is.

The method for manufacturing a holographic optical element according to an embodiment of the present invention can easily improve diffraction efficiency and manufacture the optical element in a simple method.

The effect of the present invention is not limited to the above-mentioned effect, and effects not mentioned will be clearly understood by those skilled in the art from the present specification and the attached drawings.

Figure 1 is a schematic diagram showing the ranges of the reproduction beam and diffraction beam of a holographic optical device according to the prior art.
Figure 2 is a schematic diagram showing the angle of incidence of a reference beam in the method of manufacturing a holographic optical element according to an exemplary embodiment of the present invention.
Figure 3 is a schematic diagram showing a reproduced beam and a diffracted beam of a holographic optical device according to an exemplary embodiment of the present invention.
Figure 4 is a graph showing the reproduction operation angle of a holographic optical element according to a comparative example.
Figure 5 is a graph showing the reproduction operation angle of a holographic optical element according to an embodiment.

The present invention will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. The present embodiments only serve to ensure that the disclosure of the present invention is complete and that common knowledge in the technical field to which the present invention pertains is not limited. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Meanwhile, the terms used in this specification are for describing embodiments and are not intended to limit the present invention. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used herein, “comprises” and/or “comprising” refers to the presence of one or more other components, steps, operations and/or elements. or does not rule out addition. Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. Terms are used only to distinguish one component from another.

Throughout the specification of the present application, when a part is said to “include” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

Throughout this specification, when a member is said to be located “on” another member, this includes not only the case where the member is in contact with the other member, but also the case where another member exists between the two members.

Throughout this specification, “A and/or B” means “A and B, or A or B.”

Throughout this specification, “interference pattern” refers to a pattern formed by interference between a reference beam and an object beam.

Throughout this specification, “angle of incidence” means the angle formed by an imaginary vertical line on the plane on which light is incident.

Throughout the specification of this application, “irradiation angle” means the angle formed with an imaginary vertical line on the surface on which light is irradiated.

Throughout the specification of this application, “reproduction angle” refers to the angle at which a diffraction beam can be emitted by the pattern of the optical element when the reproduction beam is irradiated by changing the angle.

Hereinafter, the present invention will be described in more detail.

One embodiment of the present invention is a holographic optical element in which an interference pattern is recorded due to the interference phenomenon of a reference beam incident on one side of a photosensitive sheet at a predetermined angle of incidence and an object beam incident on the other side of the photosensitive sheet, wherein an interference pattern is recorded at the incident angle. A holographic optical device is provided, wherein the diffraction efficiency of a diffraction beam with respect to a reproduction beam irradiated at a predetermined angle is 30% or more.

The holographic optical element according to an embodiment of the present invention improves diffraction efficiency without adjusting the thickness, increases the reproduction operation angle, and realizes excellent diffraction performance with a thin thickness, thereby realizing miniaturization of the device to which the holographic optical element is applied. there is.

According to one embodiment of the present invention, the holographic optical element records an interference pattern caused by interference between a reference beam incident at a predetermined angle of incidence on one side of the photosensitive sheet and an object beam incident on the other side of the photosensitive sheet. In this specification, a pattern formed by the interference phenomenon between a reference beam and an object beam is defined as an interference pattern. Specifically, after a reference beam is incident on one side of the photosensitive sheet, an object beam is incident on the other side forming an angle with the one side, and interference occurs between the reference beam and the object beam. Afterwards, the interference pattern is incident into the photosensitive sheet, and the overlapping portion of the interference phenomenon (the portion where constructive interference occurs) undergoes additional polymerization of components within the photosensitive sheet, thereby changing the refractive index. In addition, in the non-overlapping portion (the portion where destructive interference occurs), additional polymerization reaction occurs weakly and the refractive index is slightly changed, so that a pattern is recorded according to the interference pattern. Therefore, when light is incident on a pattern recorded on the photosensitive sheet, the light is consistently refracted by the pattern with a different refractive index.

According to one embodiment of the present invention, the diffraction efficiency of the diffracted beam for the reproduction beam irradiated at a predetermined angle with respect to the incident angle is 30% or more. Specifically, the holographic optical element irradiates the reproduction beam at a predetermined angle with respect to the incident angle at which the reference beam was incident on the photosensitive sheet, and then the reproduction beam is diffracted and the diffraction efficiency of the emitted diffraction beam is 30% or more. will be. As described above, by implementing a diffraction efficiency of 30% or more for the reproduction beam irradiated at a predetermined angle with respect to the incident angle, the reproduction angle range of the holographic optical element can be increased.

According to one embodiment of the present invention, the reference beam and the object beam irradiate the same surface of the photosensitive sheet to record an interference pattern. As described above, the reference beam and the object beam irradiate the same surface of the photosensitive sheet to record an interference pattern, thereby manufacturing a transmissive holographic optical element.

According to one embodiment of the present invention, the reference beam and the object beam irradiate different surfaces of the photosensitive sheet to record an interference pattern. As described above, a reflective holographic optical element can be manufactured by recording an interference pattern by irradiating different surfaces of the photosensitive sheet with the reference beam and the object beam.

According to one embodiment of the present invention, the photosensitive sheet may include a photopolymer resin. As described above, since the photosensitive sheet contains photopolymer resin, the interference pattern between the reference beam and the object beam can be effectively recorded.

According to an exemplary embodiment of the present invention, the photopolymer resin includes a photoreactive monomer; and a polymer of a photopolymer composition containing a photoinitiator. As described above, by using a photopolymer composition containing a photoreactive monomer and a photoinitiator, it is possible to realize the basic physical properties of the photopolymer resin and at the same time form a pattern on the photosensitive sheet by irradiating light.

According to one embodiment of the present invention, the photoreactive monomer may include a polyfunctional (meth)acrylate monomer or a monofunctional (meth)acrylate monomer. As described above, during the photopolymerization process of the photopolymer composition, monomers are polymerized and the refractive index increases in areas where there is a relatively large amount of polymer, and the refractive index is relatively low in areas where there is a relatively large amount of polymer binder, resulting in refractive index modulation. , a diffraction grating, or pattern, can be created by this refractive index modulation.

According to one embodiment of the present invention, the photoreactive monomer is a (meth)acrylate-based α,β-unsaturated carboxylic acid derivative, such as (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, or Examples include (meth)acrylic acid, or compounds containing a vinyl group or thiol group.

According to one embodiment of the present invention, the photoreactive monomer may include a polyfunctional (meth)acrylate monomer having a refractive index of 1.5 or more, and the polyfunctional (meth)acrylate monomer having a refractive index of 1.5 or more may include a halogen atom (bromine, iodine, etc.), sulfur (S), phosphorus (P), or an aromatic ring.

According to one embodiment of the present invention, the polyfunctional (meth)acrylate monomer having a refractive index of 1.5 or more includes sphenol A modified diacrylate series, fluorene acrylate series, bisphenol fluorene epoxy acrylate series (HR6100, HR6060, HR6042, etc. - Miwon), Halogenated epoxy acrylate series (HR1139, HR3362, etc. - Miwon), etc.

According to one embodiment of the present invention, the photoreactive monomer may include a monofunctional (meth)acrylate monomer. The monofunctional (meth)acrylate monomer may contain an ether bond and a fluorene functional group inside the molecule, and specific examples of such monofunctional (meth)acrylate monomer include phenoxy benzyl (meth)acrylate, o-phenyl. Examples include phenol ethylene oxide (meth)acrylate, benzyl (meth)acrylate, 2-(phenylthio)ethyl (meth)acrylate, or biphenylmethyl (meth)acrylate.

According to an exemplary embodiment of the present invention, the photoreactive monomer may have a molecular weight of 50 g/mol or more and 1000 g/mol or less, or 200 g/mol or more and 600 g/mol or less.

According to one embodiment of the present invention, the photopolymer composition includes a photoinitiator. The photoinitiator is a compound that is activated by light or actinic radiation and initiates the polymerization of a compound containing a photoreactive functional group such as the photoreactive monomer.

According to one embodiment of the present invention, the photoinitiator may include a radical photopolymerization initiator and a photocationic polymerization initiator.

According to one embodiment of the present invention, the radical photopolymerization initiator is an imidazole derivative, a bisimidazole derivative, an N-aryl glycine derivative, an organic azide compound, titanocene, an aluminate complex, an organic peroxide, and an N-alkoxy pyrilicate. dinium salts, thioxanthone derivatives, etc. can be mentioned. More specifically, the photo radical polymerization initiator includes 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4''-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercapto benzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethane-1-one (Product name: Irgacure 651 / Manufacturer: BASF), 1-hydroxy-cyclohexyl-phenyl -ketone (product name: Irgacure 184 / manufacturer: BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (product name: Irgacure 369 / manufacturer: BASF), and bis(η5-2, 4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium (Product name: Irgacure 784 Manufacturer: BASF), etc.

According to one embodiment of the present invention, the photocationic polymerization initiator may include diazonium salt, sulfonium salt, or iodonium salt, for example, sulfonic acid ester, imide sulfonate, dialkyl-4-hydroxy sulfonium salt, aryl sulfonic acid-p-nitrobenzyl ester, silanol-aluminum complex, (η6-benzene)(η5-cyclopentadienyl)iron(II), etc. I can hear it. Additionally, benzoin tosylate, 2,5-dinitro benzyl tosylate, N-tosylphthalic acid imide, etc. are also included. More specific examples of the photocationic polymerization initiator include Cyracure UVI-6970, Cyracure UVI-6974 and Cyracure UVI-6990 (manufacturer: Dow Chemical Co. in USA), Irgacure 264 and Irgacure 250 (manufacturer: BASF), or CIT-1682. (Manufacturer: Nippon Soda).

According to one embodiment of the present invention, the photopolymer composition may use a monomolecular (Type I) or bimolecular (Type II) initiator. Monomolecular (Type I) initiators for the free radical photopolymerization include aromatic ketone compounds in combination with tertiary amines, such as benzophenone, alkylbenzophenone, 4,4'-bis(dimethylamino)benzophenone (Michler's) ketones), anthrones and halogenated benzophenones or mixtures of these types. The bimolecular (Type II) initiators include benzoin and its derivatives, benzyl ketals, acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylophosphine oxide, phenylgly Oxyl esters, camphorquinone, alpha-aminoalkylphenone, alpha-,alpha-dialkoxyacetophenone, 1-[4-(phenylthio)phenyl]octane-1,2-dione 2-(O-benzoyloxime) and alpha -Hydroxyalkylphenone, etc. can be mentioned.

According to one embodiment of the present invention, the photopolymer composition contains 10% by weight or more and 70% by weight or less of the photoreactive monomer; and 0.1% by weight or more and 15% by weight or less of a photoinitiator; or 20% by weight or more and 60% by weight or less of the photoreactive monomer; and a photoinitiator of 0.1% by weight or more and 10% by weight or less. As described later, when the photopolymer composition further includes an organic solvent, the content of the above-mentioned components is based on the total of these components (total of components excluding the organic solvent).

According to one embodiment of the present invention, the photopolymer composition may further include a photosensitive dye. The photosensitive dye serves as a sensitizing dye that sensitizes the photoinitiator. Specifically, the photosensitive dye can also serve as an initiator that initiates polymerization of monomers and crosslinking monomers by being stimulated by light irradiated to the photopolymer composition. The photopolymer composition may include 0.01 wt% to 30 wt% or 0.05 wt% to 20 wt% of photosensitive dye.

According to one embodiment of the present invention, the photosensitive dye is a sulfonium derivative of ceramidonin, new methylene blue, thioerythrosine triethylammonium, and 6-acetyl Amino-2-methylceramidonin (6-acetylamino-2-methylceramidonin), eosin, erythrosine, rose bengal, thionine, basic yellow, pina Pinacyanol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, Celestine blue, quinaldine red. (QuinaldineRed), crystal violet, brilliant green, Astrazon orange G, darrow red, pyronin Y, basic red 29), pyrylium iodide, Safranin O, cyanine, methylene blue, Azure A, or a combination of two or more thereof.

According to one embodiment of the present invention, the photopolymer composition may further include an organic solvent. Non-limiting examples of the organic solvent include ketones, alcohols, acetates, and ethers, or mixtures of two or more thereof.

According to an exemplary embodiment of the present invention, the organic solvent includes ketones such as methyl ethyl canone, methyl isobutyl ketone, acetylacetone, or isobutyl ketone; Alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or t-butanol; Acetates such as ethyl acetate, i-propyl acetate, or polyethylene glycol monomethyl ether acetate; ethers such as tetrahydrofuran or propylene glycol monomethyl ether; Or a mixture of two or more types thereof may be mentioned.

According to one embodiment of the present invention, the organic solvent may be added at the time of mixing each component included in the photopolymer composition, or may be included in the photopolymer composition while each component is added in a dispersed or mixed state in the organic solvent. there is. If the content of the organic solvent in the photopolymer composition is too small, the flowability of the photopolymer composition may decrease and defects such as streaks may occur in the final manufactured film. In addition, when an excessive amount of the organic solvent is added, the solid content is lowered, and coating and film formation are not sufficiently performed, which may deteriorate the physical properties or surface characteristics of the film, and defects may occur during drying and curing processes. Accordingly, the photopolymer composition may include an organic solvent so that the total solid concentration of the components included is 1% by weight to 70% by weight, or 2% by weight to 50% by weight.

According to one embodiment of the present invention, the photopolymer composition may further include other additives, catalysts, etc. The photopolymer composition may contain a commonly known catalyst to promote polymerization of photoreactive monomers. Examples of the catalyst include tin octanoate, zinc octanoate, dibutyltin dilaurate, dimethylbis[(1-oxoneodecyl)oxy]stanane, dimethyltin dicarboxylate, and zirconium bis(ethylhexadecyl). noate), zirconium acetylacetonate or tertiary amines such as 1,4-diazabicyclo[2.2.2]octane, diazabicyclononane, diazabicycloundecane, 1,1,3,3-tetramethylguanidine , 1,3,4,6,7,8-hexahydro-1-methyl-2H-pyrimido (1,2-a) pyrimidine, etc.

According to one embodiment of the present invention, the reference beam may be continuously incident at a predetermined angle based on the incident angle. Specifically, the reference beam can be continuously incident at a predetermined angle with respect to the incident angle incident on the photosensitive sheet. As described above, the reference beam is continuously incident at a predetermined angle based on the incident angle, thereby increasing the reproduction angle range of the reproduction beam that can emit a diffracted beam by incident the reproduction beam.

According to an exemplary embodiment of the present invention, the reference beam may be continuously incident at an angle of -11° or more and +11° or less based on the incident angle. Specifically, the reference beam is -12° or more and +12° or less, -13° or more and +13° or less, -14° or more and +14° or less, -15° or more and +15° or less, -20° based on the incident angle. It may be continuously incident at an angle of more than +20° or less than -25° and less than +25°. As described above, by adjusting the incident angle of the reference beam and making it continuously incident, the reproduction angle of the holographic optical element can be improved.

According to an exemplary embodiment of the present invention, the reproduction beam may be irradiated at an angle of -11° or more and +11° or less based on the incident angle. Specifically, the regenerative beam is -12° or more and +12° or less, -13° or more and +13° or less, -14° or more and +14° or less, -15° or more and +15° or less, -20° based on the incident angle. It can be irradiated at an angle of more than + 20 ° or less than - 25 ° and less than + 25 °. By adjusting the angle at which the reproduction beam is irradiated (irradiation angle) within the above-mentioned range, the diffraction efficiency of the holographic optical element can be improved.

One embodiment of the present invention includes the steps of incident a reference beam at a predetermined angle of incidence on one side of the photosensitive sheet and incident an object beam on the other side of the photosensitive sheet; and recording an interference pattern caused by interference between the reference beam and the object beam on the photosensitive sheet, wherein the diffraction efficiency of the diffracted beam for the reproduction beam irradiated at a predetermined angle with respect to the incident angle is 30. % or more, and provides a method for manufacturing a holographic optical element.

The method for manufacturing a holographic optical element according to an embodiment of the present invention can easily improve diffraction efficiency and manufacture the optical element in a simple method.

According to one embodiment of the present invention, it includes the step of incident a reference beam at a predetermined angle of incidence on one side of the photosensitive sheet and incident an object beam on the other side of the photosensitive sheet. As described above, by making the reference beam and the object beam incident on the photosensitive sheet, the interference pattern within the photosensitive sheet can be efficiently improved.

According to one embodiment of the present invention, the method includes recording an interference pattern caused by interference between the reference beam and the object beam on the photosensitive sheet. As described above, by recording an interference pattern caused by interference between the reference beam and the object beam on the photosensitive sheet, the diffraction efficiency of the holographic optical element can be improved and the reproduction angle range can be increased.

According to one embodiment of the present invention, the reference beam may be continuously incident at a predetermined angle based on the incident angle. As described above, the reference beam is continuously incident at a predetermined angle based on the incident angle, thereby increasing the reproduction angle range of the reproduction beam that can emit a diffracted beam by incident the reproduction beam.

According to one embodiment of the present invention, the method may further include bleaching the photosensitive sheet on which the interference pattern is recorded by irradiating light having a wavelength in the visible to ultraviolet range. As described above, by including the step of bleaching the photosensitive sheet on which the pattern is recorded, the reaction of unreacted photoreactive monomers in the photopolymer resin contained in the photosensitive sheet can be completed.

According to one embodiment of the present invention, the wavelength of light irradiated in the bleaching step may be the visible light region or the ultraviolet light region. As described above, by adjusting the wavelength of light irradiated in the bleaching step, the reaction of unreacted photoreactive monomers in the photopolymer resin can be effectively completed.

According to one embodiment of the present invention, the step of additionally curing the photosensitive sheet may be included after the bleaching step. The curing may be thermal curing or photo curing. By additionally curing the photopolymer resin as described above, high-temperature durability can be improved by further fixing the interference pattern recorded on the photopolymer.

Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those skilled in the art.

Figure 2 is a schematic diagram showing the angle of incidence of a reference beam in the method of manufacturing a holographic optical element according to an exemplary embodiment of the present invention. Specifically, referring to FIG. 2, the reference beam (RB) is irradiated to one surface of the photosensitive sheet 101 at a predetermined angle of incidence (θ _i ), and at the same time, the one surface of the photosensitive sheet 101 on which the reference beam (RB) is incident. An object beam (OB) is incident on the opposite side. Thereafter, the reference beam (RB) is rotated at a predetermined angle based on the incident angle, and an interference pattern caused by interference between the reference beam (RB) and the object beam (OB) is recorded on the photosensitive sheet 101. Let's do it.

Figure 3 is a schematic diagram showing a reproduction beam (PB) and a diffraction beam (DB) of a holographic optical device according to an exemplary embodiment of the present invention. Referring to FIG. 3, the reference beam RB is incident on the photosensitive sheet 101 at an incident angle θ i that is a predetermined range rather than an incident angle θ _i , which is a specific value, and an interference pattern is recorded, thereby recording the reproduction beam PB _. ) Even if the beam is irradiated at a wide range of angles, a diffraction beam (DB) may be emitted.

Figure 4 is a graph showing the reproduction operation angle of a holographic optical element according to a comparative example. In the comparative example, an interference pattern was recorded on the photosensitive sheet by using a reference beam with an incident angle of 0° on one side of the photosensitive sheet and by using an object beam with an incident angle of 50° on the opposite side of the side of the photosensitive sheet on which the reference beam was incident. A holographic optical element was manufactured in which, when a reproduction beam with an incident angle of 0° is irradiated on one side of a photosensitive sheet, a diffraction beam with a diffraction angle of 50° is reproduced with respect to one side of the photosensitive sheet on which the reference beam is incident. Afterwards, the diffraction efficiency was measured by changing the irradiation angle of the regenerative beam in the comparative example. Referring to Figure 4, it was confirmed that the comparative example, which is a holographic optical device of the prior art, had a diffraction efficiency of more than 30% from -3.5 ° to +3.5 °.

Figure 5 is a graph showing the reproduction operation angle of a holographic optical element according to an embodiment. In the above embodiment, an interference pattern is formed using a reference beam with an incident angle of 0° on one side of the photosensitive sheet and an object beam with an incident angle of 50° on the opposite side of the side of the photosensitive sheet on which the reference beam is incident. The interference pattern is recorded on the photosensitive sheet by continuously irradiating the reference beam to form a predetermined angle based on the incident angle, so that when a reproduction beam with an incident angle of 0° is irradiated on one side of the photosensitive sheet, the reference beam is incident. A holographic optical device was manufactured in which a diffraction beam with a diffraction angle of 50° was recorded on one side of a photosensitive sheet. Afterwards, the diffraction efficiency was measured by changing the irradiation angle of the reproduction beam in the above example. Referring to Figure 5, it was confirmed that the comparative example, which is a holographic optical device of the prior art, had a diffraction efficiency of more than 30% from -11 ° to +11 °.

Referring to the above example and the comparative example, it was confirmed that when irradiated with a reproduction beam, the diffraction efficiency was similar, but the reproduction angle of the holographic optical element significantly increased.

Therefore, according to the present invention, the diffraction efficiency of the diffracted beam can be improved and the reproduction angle can be increased by continuously changing the incident angle of the reference beam and recording the reproduction pattern on the photosensitive sheet.

Although the present invention has been described in terms of limited embodiments in the above, the present invention is not limited thereto, and the technical idea of the present invention and the patent claims described below will be understood by those skilled in the art in the technical field to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equality.

1O: Conventional holographic optical element
100: Holographic optical element
101: Photosensitive sheet
PB: Playback beam
DB: diffracted beam
RB: reference beam
OB: object beam
θ _i : Incident angle of reference beam

Claims (7)

A holographic optical element in which an interference pattern is recorded due to the interference phenomenon of a reference beam incident on one side of a photosensitive sheet at a predetermined angle of incidence and an object beam incident on the other side of the photosensitive sheet,
The diffraction efficiency of the diffracted beam for the reproduction beam irradiated at a predetermined angle with respect to the incident angle is 30% or more,
Holographic optical device. In claim 1,
The reference beam is continuously incident at a predetermined angle based on the incident angle,
Holographic optical device. In claim 2,
The reference beam is continuously incident at an angle of -11° or more and +11° or less based on the incident angle,
Holographic optical device. In claim 1,
The reproduction beam is irradiated at an angle of -11 ° or more and +11 ° or less based on the incident angle,
Holographic optical device. making a reference beam incident on one side of the photosensitive sheet at a predetermined angle of incidence and making an object beam incident on the other side of the photosensitive sheet; and
It includes recording an interference pattern caused by interference between the reference beam and the object beam on the photosensitive sheet,
The diffraction efficiency of the diffracted beam for the reproduction beam irradiated at a predetermined angle with respect to the incident angle is 30% or more,
Method for manufacturing holographic optical elements. In claim 5,
The reference beam is continuously incident at a predetermined angle based on the incident angle,
Method for manufacturing holographic optical elements. In claim 5,
Further comprising the step of bleaching the photosensitive sheet on which the interference pattern is recorded by irradiating light having a wavelength in the visible to ultraviolet range.
Method for manufacturing holographic optical elements.