Metasurface reflector, projection device, near-to-eye wearable device, and method for manufacturing metasurface reflector

Abstract

The invention relates to a metasurface reflector, a projection device, a near-to-eye wearable device and a manufacturing method of the metasurface reflector. The metasurface reflector includes a first metal layer and a second metal layer stacked in a first direction, a dielectric layer provided between the first metal layer and the second metal layer in the first direction, and a protective layer covering the second metal layer, the dielectric layer having a main surface on which the second metal layer is provided. The metasurface reflector is divided into a plurality of unit regions arranged in a second direction and a third direction, the second direction is along the main surface, the third direction is along the main surface and intersects the second direction, and the second metal layer includes metal cells provided in all or some of the plurality of unit regions. The protective layer is formed of a metal having a standard electrode potential greater than a standard electrode potential of the metal constituting the second metal layer. The protective layer includes a first portion covering a top surface of the metal cell and a second portion covering a side surface of the metal cell.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of priority from Japanese Patent Application No. 2024-33223 filed with the Japan Patent Office on March 5, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a metasurface reflector, a projection device, a near-eye wearable device, and a method for manufacturing the metasurface reflector. Background Art

[0004] Reflectors utilizing metasurface technology are known. For example, U.S. Patent Application Publication No. 2018 / 0113310 describes a near-eye display assembly comprising an image source and a combiner including a nanostructured surface optically coupled to the image source. The unit cell of the nanostructured surface is constructed by sequentially stacking a base layer, a dielectric layer, and a meta-atomic layer. Summary of the Invention

[0005] In the near-eye display assembly described in U.S. Patent Application Publication No. 2018 / 0113310, the meta-atomic layer is exposed. When a metal layer, such as silver or aluminum, is used as the meta-atomic layer, exposure to air can sometimes cause the metal layer to oxidize or sulfide. This can alter optical properties and potentially degrade reflectivity.

[0006] The present disclosure describes a metasurface reflector, a projection device, a near-eye wearable device, and a method for manufacturing the metasurface reflector that can suppress degradation of reflective properties.

[0007] A metasurface reflector according to one aspect of the present disclosure comprises: a first metal layer and a second metal layer, the first metal layer and the second metal layer being stacked in a first direction; a dielectric layer disposed between the first metal layer and the second metal layer in the first direction; and a protective layer covering the second metal layer. The dielectric layer has a main surface on which the second metal layer is disposed. The metasurface reflector is divided into a plurality of unit regions arranged in a second direction and a third direction, the second direction being along the main surface, and the third direction being along the main surface and intersecting the second direction. The second metal layer includes metal units for each unit region of all or part of the unit regions disposed in the plurality of unit regions. The protective layer is composed of a metal having a standard electrode potential greater than the standard electrode potential of the metal constituting the second metal layer. The metal unit has a bottom surface facing the dielectric layer in the first direction, a top surface disposed on the opposite side of the bottom surface in the first direction, and a side surface connecting the top surface and the bottom surface. The protective layer includes a first portion covering the top surface and a second portion covering the side surface.

[0008] In this metasurface reflector, the protective layer covers the top and side surfaces of the metal units. Therefore, when the metasurface reflector is in use, the top and side surfaces of the metal units are not exposed to air, thereby reducing the likelihood of oxidation and sulfidation of the metal units. Furthermore, because the protective layer is composed of a metal with a standard electrode potential greater than that of the metal constituting the second metal layer, it is less susceptible to oxidation and sulfidation than the second metal layer. Consequently, in this metasurface reflector, the optical properties are less likely to change. Consequently, degradation of the reflective properties can be suppressed.

[0009] Alternatively, the thickness of the protective layer may be less than 20% of the sum of the length of the second metal layer in the first direction and the thickness of the protective layer. In this case, the protective layer can be provided to suppress the effect on the reflective properties of the metasurface reflector, thereby further suppressing degradation of the reflective properties.

[0010] Alternatively, the metal unit may be a metal body having a trapezoidal shape when viewed from the first direction. In this case, the structure of the metal unit can be simplified compared to a case where the metal unit is composed of multiple metal bodies. This can facilitate the manufacture of the metasurface reflector.

[0011] Alternatively, the length of the metal body in the second direction may be greater than 500nm and less than 2500nm. The length of the metal body in the first direction may be greater than 10nm and less than 100nm. Alternatively, the length of the short side of the metal body may be greater than 10nm and less than 200nm. Alternatively, the length of the long side of the metal body may be greater than the length of the short side, and may be greater than 100nm and less than 500nm. In this case, the reflection efficiency can be improved for visible light.

[0012] The protective layer may be made of a metal containing at least one element selected from the group consisting of gold, ruthenium, and iridium. In this case, degradation of the reflective characteristics can be suppressed compared to molybdenum, titanium, tungsten, and the like.

[0013] Alternatively, the second metal layer may be composed of a metal containing at least one element selected from the group consisting of silver, aluminum, and copper. In this case, a second metal layer having a relatively high reflectivity and a relatively high electrical conductivity can be obtained. This enhances the electromagnetic resonance between the first and second metal layers, improving reflection efficiency.

[0014] The dielectric layer may be made of a material that is transparent in the visible light region. In this case, since the absorption rate of visible light in the dielectric layer can be suppressed, the reflection efficiency of visible light can be improved.

[0015] Alternatively, the dielectric layer may be composed of a compound selected from the group consisting of silicon oxide, titanium oxide, magnesium oxide, and aluminum oxide. In this case, a dielectric layer having a dielectric constant that does not hinder electromagnetic interaction can be obtained. This enhances the electromagnetic resonance between the first and second metal layers, improving reflection efficiency.

[0016] Alternatively, the length of the dielectric layer in the first direction may be greater than 10 nm and less than 100 nm. Alternatively, the length of the first metal layer in the first direction may be greater than 50 nm and less than 1000 nm. In this case, the possibility of the dielectric layer obstructing electromagnetic interaction can be reduced, and the possibility of laser light passing through the first metal layer can be reduced. This can thereby improve reflection efficiency.

[0017] Alternatively, the thickness of the second portion may decrease as it moves away from the dielectric layer in the first direction. The thinner the thickness of the second portion, the higher the reflected electric field intensity. Therefore, the protective layer can be provided to suppress the impact on the reflective properties of the metasurface reflector. This can further suppress the deterioration of the reflective properties.

[0018] Another aspect of the present disclosure is a projection device mounted on a near-eye wearable device. The projection device includes: a light source that emits laser light; a movable mirror for scanning with the laser light; and a metasurface reflector that reflects the laser light after passing through the movable mirror, allowing a user wearing the near-eye wearable device to visually recognize an image. This projection device can also suppress degradation of reflection characteristics.

[0019] Another aspect of the present disclosure provides a near-eye wearable device comprising the above-described projection device and a lens provided with a metasurface reflector. This near-eye wearable device can also suppress degradation of reflective properties.

[0020] A method for manufacturing a metasurface reflector according to another aspect of the present disclosure includes the following steps: preparing a stacked body formed by stacking a first metal layer, a dielectric layer, a second metal layer, and a third metal layer in sequence in a first direction; forming a resist film on the third metal layer; forming a pattern on the resist film to form a metal unit, the metal unit constituting the metasurface reflector having a bottom surface facing the dielectric layer in the first direction, a top surface located opposite the bottom surface in the first direction, and a side surface connecting the top surface and the bottom surface; polishing the second metal layer and the third metal layer using the pattern to form the metal unit and forming a first protective film covering the top surface; and forming a second protective film covering the side surfaces of the metal unit. The first protective film and the second protective film are composed of a metal having a standard electrode potential greater than that of the metal constituting the second metal layer.

[0021] In the manufacturing method of this metasurface reflector, a pattern is formed on a resist film formed on the third metal layer of the stack, and the second and third metal layers are polished using the pattern, thereby forming a metal unit and a first protective film covering the top surface of the metal unit. A second protective film is then formed on the side of the metal unit. In the metasurface reflector manufactured in this way, since the top and side surfaces of the metal unit are not exposed to the air during use, the possibility of the metal unit being oxidized and sulfided can be reduced. Furthermore, since the first and second protective films are composed of a metal having a standard electrode potential greater than that of the metal constituting the second metal layer, the first and second protective films are less susceptible to oxidation and sulfidation than the second metal layer. Therefore, in the above-mentioned metasurface reflector, the optical properties are less likely to change. As a result, the deterioration of the reflection characteristics can be suppressed.

[0022] Alternatively, the step of forming the second protective film may include the following steps: removing the resist film; forming a metal film on the surface of the structure obtained by removing the resist film; and removing a portion of the metal film formed on the main surface of the dielectric layer to form the second protective film. In this case, the second protective film can be formed on the side surfaces of the metal unit using a relatively simple process.

[0023] Alternatively, in the process of forming the resist film, a multilayer resist film including a lower resist film and an upper resist film is formed on the third metal layer. Alternatively, the process of forming the second protective film includes the following steps: forming a metal film on the surface of the structure obtained by the process of forming the first protective film; forming a second protective film by removing the portion of the metal film formed on the main surface of the dielectric layer; and removing the multilayer resist film after the second protective film is formed. In this case, the multilayer resist film is removed while the top surface of the metal unit is covered by the first protective film and the side surface of the metal unit is covered by the second protective film. Therefore, the top surface and side surface of the metal unit will not be exposed to the solvent used to remove the multilayer resist film, thereby reducing the possibility of corrosion of the metal unit. As a result, the deterioration of the reflection characteristics of the above-mentioned metasurface reflector can be further suppressed.

[0024] Alternatively, the metal film may be formed by oblique-incidence sputtering in the step of forming the metal film. In this case, the metal film is easily formed on the side surfaces of the metal unit, thereby shortening the time required to manufacture the metasurface reflector.

[0025] According to the aspects and embodiments of the present disclosure, it is possible to suppress deterioration of reflection characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a three-dimensional diagram showing the appearance of a near-eye wearable device using a metasurface reflector according to one embodiment.

[0027] Figure 2 It roughly indicates Figure 1 The structural diagram of the projection device shown.

[0028] Figure 3 It is magnified Figure 2 Diagram of the metasurface reflector shown.

[0029] Figure 4 It roughly indicates Figure 3 A stereogram of the unit area shown.

[0030] Figure 5 It is along Figure 4 Cross-sectional view of line VV.

[0031] Figure 6 Is used to illustrate Figure 2 Diagram of the reflection principle of the metasurface reflector shown.

[0032] Figure 7 Graph showing the amount of phase change of reflected light at positions in the X-axis direction of the metasurface reflector.

[0033] Figure 8 This is a diagram for explaining the relationship between the position in the X-axis direction and the length of the metal unit in the X-axis direction.

[0034] Figure 9 This is a graph showing the relationship between the ratio of the protective layer and the reflected electric field intensity.

[0035] Figure 10 This is a process diagram showing an example of a method for manufacturing a metasurface reflector.

[0036] Figure 11 Is used to illustrate Figure 10 FIG. 1 is a diagram showing a resist film forming process.

[0037] Figure 12 Is used to illustrate Figure 10 The diagram of the pattern forming process is shown.

[0038] Figure 13 Is used to illustrate Figure 10 FIG. 1 shows a diagram of the first protective film forming step.

[0039] Figure 14 Is used to illustrate Figure 10 FIG. 1 shows a diagram of the resist film removal process.

[0040] Figure 15 Is used to illustrate Figure 10 The figure shows the metal film forming process.

[0041] Figure 16 Is used to illustrate Figure 10Figure 2 shows the metal film removal process.

[0042] Figure 17 This is a process diagram showing another example of a method for manufacturing a metasurface reflector.

[0043] Figure 18 Is used to illustrate Figure 17 FIG. 1 is a diagram showing a resist film forming process.

[0044] Figure 19 Is used to illustrate Figure 17 The diagram of the pattern forming process is shown.

[0045] Figure 20 Is used to illustrate Figure 17 FIG. 1 shows a diagram of the first protective film forming step.

[0046] Figure 21 Is used to illustrate Figure 17 The figure shows the metal film forming process.

[0047] Figure 22 Is used to illustrate Figure 17 Figure 2 shows the metal film removal process.

[0048] Figure 23 Is used to illustrate Figure 17 FIG. 1 shows a diagram of the resist film removal process. DETAILED DESCRIPTION

[0049] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. In addition, the same elements are marked with the same figure marks in the description of the drawings, and repeated descriptions are omitted. In each figure, there is a case where an XYZ coordinate system is shown. The Y-axis direction (the third direction) is a direction that intersects (for example, is orthogonal to) the X-axis direction (the second direction) and the Z-axis direction (the first direction). The Z-axis direction is a direction that intersects (for example, is orthogonal to) the X-axis direction and the Y-axis direction. In this specification, the numerical range represented by "to" represents a range that includes the numerical values ​​recorded before and after the "to" as the minimum value and the maximum value, respectively. The upper limit value and the lower limit value recorded separately can be combined arbitrarily.

[0050] Reference Figure 1 A near-eye wearable device using a metasurface reflector according to one embodiment is described. Figure 1 This is a three-dimensional diagram showing the appearance of a near-eye wearable device using a metasurface reflector according to one embodiment. Figure 1The near-eye wearable device 1 shown is a device that overlaps an image with the field of view of the real world. The near-eye wearable device 1 is, for example, a head-mounted device (head-mounted device) and can be in the form of glasses, goggles, a hat, or a helmet. Examples of the near-eye wearable device 1 include smart glasses such as AR (Augmented Reality) glasses and MR (Mixed Reality) glasses. The near-eye wearable device 1 includes a frame 2, lenses 3, and a projection device 10.

[0051] The frame 2 includes a pair of rims 2a, a nose bridge 2b, and a pair of temples 2c. The rims 2a hold the lenses 3. The nose bridge 2b connects the rims 2a. The temples 2c extend from the rims 2a and hang on the user's ears. The frame 2 may also be a frame without rims. The lenses 3 have a shape that is aligned with the eyeball E of the user wearing the near-eye wearable device 1 (see Figure 6 ) facing inner surface 3a (refer to Figure 2 ).

[0052] In this embodiment, the projection device 10 projects (draws) an image directly onto the retina RE (refer to Figure 6 The projection device 10 is mounted on the near-eye wearable device 1. In this embodiment, in order to project images onto the left and right retinas RE, the near-eye wearable device 1 includes two projection devices 10, but it may also include only one projection device 10.

[0053] Next, refer to Figure 2 The projection device 10 will be described in detail. Figure 2 It roughly indicates Figure 1 The structural diagram of the projection device shown in FIG. Figure 2 As shown, the projection device 10 includes an optical engine 20 and a metasurface reflector 30.

[0054] The optical engine 20 is a device that generates laser light Ls of a color and intensity corresponding to the pixels of the image projected onto the retina RE and emits the laser light Ls toward the metasurface reflector 30. The optical engine 20 is mounted on each temple 2c. The optical engine 20 includes a light source unit 21 (light source), optical components 22, a movable mirror 23, a laser driver 24, a mirror driver 25, and a controller 26.

[0055] The light source unit 21 emits laser light. For example, a full-color laser module is used as the light source unit 21. The light source unit 21 includes a red laser diode, a green laser diode, a blue laser diode, and a combining unit that combines the laser light emitted from each laser diode into a single laser light. The light source unit 21 emits the combined laser light. The combined laser light includes a component with a red wavelength (red component), a component with a green wavelength (green component), and a component with a blue wavelength (blue component). The light source unit 21 emits laser light of a color and intensity corresponding to the pixel of the image projected onto the retina RE.

[0056] The optical component 22 optically processes the laser light emitted from the light source unit 21. In this embodiment, the optical component 22 includes a collimating lens 22a, an aperture 22b, and a neutral density filter 22c. The collimating lens 22a, the aperture 22b, and the neutral density filter 22c are arranged in sequence along the optical path of the laser light. The optical component 22 may also have other structures.

[0057] The movable mirror 23 is an optical component used for scanning with the laser light Ls. It is positioned in the direction of emission of the laser light processed by the optical component 22. The movable mirror 23 is configured, for example, to be able to swing about an axis extending transversely (in the X-axis direction) and longitudinally (in the Y-axis direction) of the lens 3, reflecting the laser light while varying its angle in the X- and Y-axis directions. A MEMS (Micro Electro Mechanical Systems) mirror is used as the movable mirror 23, for example.

[0058] The laser driver 24 is a drive circuit that drives the light source unit 21. The laser driver 24 drives the light source unit 21 based on, for example, the intensity of the laser light and the temperature of the light source unit 21. The mirror driver 25 is a drive circuit that drives the movable mirror 23. The mirror driver 25 causes the movable mirror 23 to oscillate within a predetermined angular range and at a predetermined timing. The controller 26 is a device that controls the laser driver 24 and the mirror driver 25.

[0059] In the optical engine 20, laser light of a color and intensity corresponding to the pixels of the image projected onto the retina RE is emitted from the light source unit 21, passes through the optical component 22, and is reflected by the movable mirror 23. The laser light reflected by the movable mirror 23 is emitted as laser light Ls toward the metasurface reflector 30.

[0060] The metasurface reflector 30 is an optical component that reflects the laser light Ls after passing through the movable reflector 23 so that the user wearing the near-eye wearable device 1 can visually recognize an image. No image is displayed on the metasurface reflector 30. The metasurface reflector 30 is provided on the inner surface 3a of the lens 3.

[0061] Next, refer to Figures 3 to 5 The structure of the metasurface reflector 30 will be described. Figure 3 It is magnified Figure 2 Diagram of the metasurface reflector shown. Figure 4 It roughly indicates Figure 3 A stereogram of the unit area shown. Figure 5 It is along Figure 4 Cross-sectional view of line VV.

[0062] like Figure 3 As shown, the metasurface reflector 30 is divided into a plurality of unit areas 31. The plurality of unit areas 31 are arranged along the inner surface 3a of the lens 3. The plurality of unit areas 31 are arranged in a two-dimensional array along the transverse direction (X-axis direction) and the longitudinal direction (Y-axis direction) of the lens 3.

[0063] like Figure 4 and Figure 5 As shown, the metasurface reflector 30 includes a metal layer 41 (first metal layer), a dielectric layer 42, a metal layer 43 (second metal layer), and a protective layer 44 in sequence in the Z-axis direction.

[0064] The metal layer 41 serves as a base layer. It is provided on the inner surface 3a of the lens 3. The metal layer 41 is composed of a metal having high reflectivity in the visible light region. For example, the metal layer 41 is composed of a metal containing at least one element selected from the group consisting of gold (Au), copper (Cu), silver (Ag), and aluminum (Al). The length of the metal layer 41 in the Z-axis direction (thickness d1) is sufficient as long as the metal layer 41 can pass a resonant current and reflect light, and is, for example, 50 nm to 1000 nm.

[0065] The dielectric layer 42 is a layer that functions as a spacer. The dielectric layer 42 is provided between the metal layer 41 and the metal layer 43 in the Z-axis direction. In this embodiment, the dielectric layer 42 is provided on the metal layer 41. The dielectric layer 42 has a main surface 42a for providing the metal layer 43. The dielectric layer 42 has a dielectric constant that does not hinder the electromagnetic interaction generated by the metal layer 41 and the metal layer 43. The dielectric layer 42 is composed of a material that is transparent in the visible light region. The dielectric layer 42 can also be composed of a material with a higher dielectric constant to achieve higher reflective characteristics. For example, the dielectric layer 42 is composed of a compound selected from the group consisting of silicon oxide (e.g., SiO2), titanium oxide (e.g., TiO2), magnesium oxide (e.g., MgO), and aluminum oxide (e.g., Al2O3). The length (thickness d2) of the dielectric layer 42 in the Z-axis direction is, for example, 10 nm to 100 nm.

[0066] Metal layer 43 is a layer that excites electromagnetic resonance together with metal layer 41. Metal layer 41 and metal layer 43 are stacked in the Z-axis direction with dielectric layer 42 interposed therebetween. In this embodiment, metal layer 43 is provided on the main surface 42a of dielectric layer 42. Metal layer 43 is composed of a metal having high reflectivity in the visible light region. For example, metal layer 43 is composed of a metal containing at least one element selected from the group consisting of silver (Ag), aluminum (Al), and copper (Cu).

[0067] The metal layer 43 includes a plurality of metal units 45. The metal units 45 are provided in each of the plurality of unit regions 31. Each metal unit 45 is configured such that the phase change amount of the reflected light Lr caused by the metal unit 45 increases as it moves from one end 31a (first end) in the X-axis direction of the unit region 31 where the metal unit 45 is provided toward the other end 31b (second end). Each metal unit 45 is further configured so that the phase change of the reflected light Lr is The phase change of the reflected light Lr is substantially 360° (2π radians) from one end 31a to the other end 31b. It refers to the phase change of the reflected light Lr when the length of the metal unit 45 in the Y-axis direction is changed, based on the phase of the reflected light Lr at a certain length in the Y-axis direction of the metal unit 45. Hereinafter, the length in the Y-axis direction may be referred to as "width".

[0068] In this embodiment, each metal unit 45 is a single metal body having a trapezoidal shape when viewed from the Z-axis direction. The length (thickness d3) of each metal unit 45 in the Z-axis direction is, for example, 10 nm to 100 nm. The length of each metal unit 45 in the X-axis direction is the same as or slightly shorter than the length Lx of the unit area 31 in the X-axis direction. The length of each metal unit 45 in the X-axis direction is, for example, 500 nm to 2500 nm.

[0069] The length of the short side (width W1) of each metal element 45 is set, for example, to be approximately the resolution of the exposure device used to form the metal element 45. Width W1 is, for example, 10 nm to 200 nm. The length of the long side (width W2) of each metal element 45 is greater than width W1 and is set to a length that provides a phase difference of substantially 360° (2π radians) from the phase of the reflected light Lr at width W1. Width W2 is, for example, 100 nm to 500 nm. Each metal element 45 is formed, for example, by photolithography.

[0070] Metal unit 45 includes a top surface 45a, a bottom surface 45b, and side surfaces 45c. Bottom surface 45b is the surface facing dielectric layer 42 in the Z-axis direction. Top surface 45a is the surface located on the opposite side of bottom surface 45b in the Z-axis direction. Side surfaces 45c connect top surface 45a and bottom surface 45b. Side surfaces 45c connect the entire circumference of top surface 45a and the entire circumference of bottom surface 45b.

[0071] The protective layer 44 is a layer that protects the metal layer 43 (metal unit 45). The protective layer 44 is provided in a manner that covers the entirety of each metal unit 45. That is, the metal unit 45 is not exposed. The protective layer 44 is made of a metal that is less susceptible to oxidation and sulfidation and has higher corrosion resistance than the metal layer 43. In other words, the protective layer 44 is made of a metal having a standard electrode potential greater than the standard electrode potential of the metal constituting the metal layer 43. For example, the protective layer 44 is made of a metal containing at least one element selected from the group consisting of gold (Au), ruthenium (Ru) and iridium (Ir). In the combination of these metals with the metal constituting the metal layer 43 (e.g., silver), the attenuation of near-field light is small.

[0072] In this embodiment, protective layer 44 includes multiple metal bodies that respectively cover multiple metal elements 45. The thickness d4 of protective layer 44 (metal body) is less than 20% of the total thickness d5 (the sum of thickness d3 and thickness d4). Thickness d4 is, for example, 2.5 nm to 25 nm. The thickness d4 of protective layer 44 is not limited to the length in the Z-axis direction; it refers to the length (layer thickness) from the surface of metal element 45 to the surface of protective layer 44.

[0073] Protective layer 44 includes a first portion 44a and a second portion 44b. First portion 44a covers top surface 45a of metal unit 45. Second portion 44b covers side surface 45c of metal unit 45. The thickness of second portion 44b may decrease as it moves away from dielectric layer 42 in the Z-axis direction.

[0074] In addition, a close contact layer 46 may be provided between the inner surface 3a of the lens 3 and the metal layer 41 (see Figure 11 A close contact layer 47 may be provided between the metal layer 41 and the dielectric layer 42 (see Figure 11 A close contact layer 48 may be provided between the dielectric layer 42 and the metal layer 43 (see Figure 16 Adhesion layers 46 to 48 are layers for improving adhesion between two layers. Adhesion layers 46 to 48 are each made of, for example, chromium (Cr). The length (thickness) of each adhesion layer 46 to 48 in the Z-axis direction is approximately 3 nm.

[0075] Next, refer to Figures 5 to 8 The reflection principle of the metasurface reflector 30 and the method of determining the length Lx are described. Figure 6 Is used to illustrate Figure 2 Diagram of the reflection principle of the metasurface reflector shown. Figure 7 Graph showing the amount of phase change of reflected light at positions in the X-axis direction of the metasurface reflector. Figure 8 This is a diagram for explaining the relationship between the position in the X-axis direction and the length of the metal unit in the X-axis direction.

[0076] like Figure 5 and Figure 6 As shown, each unit area 31 is a nanostructure structured as follows: when the laser light Ls is incident at an angle θ corresponding to the position where the unit area 31 is provided, i When incident, each unit area 31 reflects at an angle θ corresponding to the position where the unit area 31 is set. r Reflected laser light Ls. Reflection angle θ of each unit area 31 r The angle of incidence θ is set so that the laser light Ls (reflected light Lr) reflected by each unit area 31 passes through the center of the pupil PP. i and the reflection angle θ r The unit area 31 is determined by the position where the unit area 31 is set. The unit area 31 is configured so that the incident angle θ corresponding to the position where the unit area 31 is set can be obtained. i and the reflection angle θ r .

[0077] Here, the incident angle θ i It is the angle between the normal line of the surface irradiated by the laser Ls and the incident direction of the laser Ls. r The angle θ is the angle between the normal line of the surface irradiated by the laser Ls and the emission direction of the reflected light Lr. In the plane containing the laser Ls and the reflected light Lr, when the reflected light Lr is emitted to the opposite side of the incident light (laser Ls) with the normal line as the boundary, the reflection angle θ is r In the case where the reflected light Lr is emitted to the same side as the incident light (laser light Ls) with the normal as the boundary, the reflection angle θ is expressed as a positive value. r Indicated by negative values.

[0078] For example, Figure 6 As shown, when the user's pupil PP faces forward, unit areas 31 are used, ranging from position Pa to position Pc in the X-axis direction. Laser light Ls reflected by unit area 31 at position Pa corresponds to the pixel at the right end of the image. Position Pb is located between positions Pa and Pc, and laser light Ls reflected by unit area 31 at position Pb corresponds to the pixel at the center of the image. Laser light Ls reflected by unit area 31 at position Pc corresponds to the pixel at the left end of the image.

[0079] In the unit area 31 provided at the position Pa, the laser light Ls is incident at an angle θ of 30°. i The incident laser Ls is reflected at an angle of θ of 5° r The laser beam Ls is reflected and emitted as reflected light Lr. In the unit area 31 provided at the position Pb, the laser beam Ls is incident at an angle θ of 40°. i The incident laser Ls is reflected at an angle of -5° r The laser beam Ls is reflected and emitted as reflected light Lr. In the unit area 31 provided at the position Pc, the laser beam Ls is incident at an angle θ of 50°. i The incident laser Ls is reflected at an angle of -10° r The light is reflected and emitted as reflected light Lr.

[0080] like Figure 7 As shown in FIG. 3 , the width of the metal unit 45 increases from width W1 to width W2 as it goes from one end 31a to the other end 31b. The phase change amount at each position in the X-axis direction of the metal unit 45 is Phase change caused by a square metal body having sides of the same length as the width at that position when viewed from above The larger the area of ​​the square metal body when viewed from above, the greater the phase change at that position. Therefore, the phase change amount varies with the position in the X-axis direction. The reflected laser light Ls forms a wavefront due to the interference between the reflected lights. That is, a wave number vector Φ is generated, which has the characteristics of the position x in the X-axis direction and the phase change amount. The function of the relationship (x) is the slope of the plane wave.

[0081] Here, if Figure 5 As shown, according to the generalized Snell's law, the wave number vector k0 of the laser Ls and the incident angle θ i , reflection angle θ r and the wave number vector Φ and is expressed by formula (1).

[0082] [Formula 1]

[0083] k0×sinθ i +Φ=k0×sinθ r (1)

[0084] The wave number vector k0 is expressed as 2π / λ using the wavelength λ of the laser light Ls. The wave number vector Φ is expressed as 2π / Lx using the length Lx in the X-axis direction of the unit area 31. By modifying the equation (1) using these relationships, the equation (2) is obtained.

[0085] [Formula 2]

[0086]

[0087] The wavelength λ of the laser light Ls and the incident angle θ of the laser light Ls corresponding to the position where the unit area 31 is provided are used to determine the wavelength λ of the laser light Ls. i and the reflection angle θ r Substituting into equation (2) yields the length Lx of the unit region 31. The laser light Ls contains red, green, and blue components, but the length Lx is determined using the wavelength λ of the green component, to which the human eye has the highest sensitivity.

[0088] When the length Lx is a positive value, the shape of the metal unit 45 is set to a trapezoidal shape in which the width of the metal unit 45 increases from one end 31a toward the other end 31b. When the length Lx is a negative value, the shape of the metal unit 45 is set to a trapezoidal shape in which the width of the metal unit 45 decreases from one end 31a toward the other end 31b.

[0089] As described above, the length Lx of each unit area 31 is determined by the wavelength λ of the reflection object and the incident angle θ corresponding to the position where the unit area 31 is provided. i and the reflection angle θ r The length of the metal unit 45 in the X-axis direction is equal to or slightly shorter than the length Lx of the unit area 31 in the X-axis direction. Therefore, the length of the metal unit 45 in the X-axis direction is determined by the wavelength λ of the reflected object and the incident angle θ corresponding to the position of the unit area 31 where the metal unit 45 is provided. i and the reflection angle θ r to decide.

[0090] At the reflection angle θ r Ratio of incident angle θ i When the incident angle θ is small, the length Lx becomes a negative value. i and reflection angle θ r As the difference increases, the absolute value of the length Lx decreases. Figure 8 As shown, in the near-eye wearable device 1, the reflection angle θ increases as the distance from the movable reflector 23 increases. r Decrease, the incident angle θ i and reflection angle θ r Therefore, the length Lx of the unit regions 31 included in the same arrangement in the X-axis direction is different from each other, and the length of the metal units 45 included in the same arrangement in the X-axis direction is also different from each other.

[0091] In addition, the length Ly of each unit area 31 is a predetermined fixed value. The length Ly is slightly larger than the width W2. The length Ly can be the length obtained by adding the resolution of the exposure device used when forming the metal unit 45 (for example, 100 nm) and the width W2, for example, it is set to 600 nm. The width W1 and width W2 of each metal unit 45 are predetermined fixed values. As described above, the width W1 is set to about the resolution of the exposure device used when forming the metal unit 45 (for example, 100 nm). The width W2 is set to a length (for example, 350 nm) that obtains a phase difference of substantially 360° (2π radians) from the phase of the reflected light Lr at the width W1.

[0092] Next, refer to Figure 9 The influence of the protective layer 44 on the intensity of the reflected light Lr will be described. Figure 9 This is a graph showing the relationship between the ratio of the protective layer and the reflected electric field intensity. Figure 9 The horizontal axis represents the ratio (unit: %) of the protective layer 44. The ratio of the protective layer 44 is represented by the ratio of the thickness d4 to the thickness d5. Figure 9 The vertical axis represents the reflected electric field intensity normalized by setting the reflected electric field intensity in the case where the protective layer 44 is not provided to 1.0.

[0093] Calculate Figure 9 The characteristics shown are shown. Specifically, silver is used as the constituent material of metal layer 41 and metal layer 43 (metal unit 45), and SiO2 is used as the constituent material of dielectric layer 42. Thickness d1 is set to 200nm, thickness d2 is set to 40nm, and thickness d3 is set to 40nm. Width W1 is set to 120nm, and width W2 is set to 300nm. The length of metal unit 45 in the X-axis direction is set to 2250nm. In addition, gold, ruthenium, and iridium are used as the constituent materials of protective layer 44. The thickness of protective layer 44 is changed for each constituent material to calculate the reflected electric field intensity at each thickness.

[0094] like Figure 9 As shown, for all constituent materials, as the proportion of protective layer 44 increases, the reflected electric field intensity decreases. When the proportion of protective layer 44 is less than 20%, the reflected electric field intensity hardly decreases compared to the reflected electric field intensity when no protective layer 44 is provided, maintaining above 90%. On the other hand, if the proportion of protective layer 44 exceeds 20%, the reflected electric field intensity drops sharply. If the proportion of protective layer 44 is above approximately 30% to 40%, the reflected electric field intensity is almost zero. Based on the above, it can be said that if the proportion of protective layer 44 is less than 20%, the intensity of reflected light Lr can be maintained.

[0095] Next, refer to Figures 10 to 16An example of a method for manufacturing the near-eye wearable device 1 will be described. Figure 10 This is a process diagram showing an example of a method for manufacturing a metasurface reflector. Figure 11 Is used to illustrate Figure 10 FIG. 1 is a diagram showing a resist film forming process. Figure 12 Is used to illustrate Figure 10 The diagram of the pattern forming process is shown. Figure 13 Is used to illustrate Figure 10 FIG. 1 shows a diagram of the first protective film forming step. Figure 14 Is used to illustrate Figure 10 FIG. 1 shows a diagram of the resist film removal process. Figure 15 Is used to illustrate Figure 10 The figure shows the metal film forming process. Figure 16 Is used to illustrate Figure 10 Figure 2 shows the metal film removal process.

[0096] Figure 10 The method M1 shown is a method for manufacturing the metasurface reflector 30. The method M1 includes a preparation step S11, a resist film forming step S12, a pattern forming step S13, a first protective film forming step S14, and a second protective film forming step S15.

[0097] <Preparation Step S11>

[0098] The preparation step S11 is a step of preparing the laminate 40. The laminate 40 is formed by sequentially stacking the substrate 50, the metal layer 41, the dielectric layer 42, the metal layer 143 (second metal layer) which serves as a precursor of the metal layer 43, and the metal layer 144 (third metal layer) which serves as a precursor of the first portion 44a of the protective layer 44 in the Z-axis direction. Here, an example in which the metasurface reflector 30 is formed on the substrate 50 instead of on the lens 3 will be described.

[0099] In the preparation step S11, a substrate 50 is first prepared and placed in a vacuum film forming device. As the substrate 50, a sapphire substrate can be exemplified. A flexible sheet can also be used as the substrate 50. Then, a metal layer 41 is formed on the surface 50a of the substrate 50. Specifically, the metal layer 41 is formed by vacuum film forming using means such as direct current sputtering. In order to form the metal layer 41, a metal material composed of any metal selected from the group consisting of gold (Au), copper (Cu), silver (Ag) and aluminum (Al) or a metal alloy containing at least one element selected from the above group is used. Here, silver is exemplified as the constituent material of the metal layer 41. The thickness d1 of the metal layer 41 is, for example, 200 nm.

[0100] Furthermore, to improve the adhesion between surface 50a of substrate 50 and metal layer 41, an adhesion layer 46 may be formed on surface 50a, and metal layer 41 may be formed on adhesion layer 46. Adhesion layer 46 is formed, for example, by sputtering or vapor deposition. Chromium (Cr) is used, for example, to form adhesion layer 46. The length (thickness) of adhesion layer 46 in the Z-axis direction is, for example, 3 nm.

[0101] Next, dielectric layer 42 is formed on metal layer 41. Specifically, dielectric layer 42 is formed by vacuum film formation using methods such as radio frequency sputtering. Dielectric layer 42 is formed using dielectric materials such as silicon dioxide (SiO2), titanium oxide (TiO2), magnesium oxide (MgO), or aluminum oxide (Al2O3), which can be formed using semiconductor processes. Silicon dioxide is exemplified as the material constituting dielectric layer 42. The thickness d2 of dielectric layer 42 is, for example, 40 nm.

[0102] Furthermore, to improve the adhesion between metal layer 41 and dielectric layer 42, an adhesion layer 47 may be formed on metal layer 41, and dielectric layer 42 may be formed on adhesion layer 47. The method for forming adhesion layer 47 is the same as the method for forming adhesion layer 46, so a detailed description is omitted. Chromium (Cr) is used, for example, to form adhesion layer 47. The length (thickness) of adhesion layer 47 in the Z-axis direction is, for example, 3 nm.

[0103] Next, metal layer 143 is formed on dielectric layer 42. The method for forming metal layer 143 is the same as that for metal layer 41, so a detailed description is omitted. Metal layer 143 is formed using a metal material composed of any metal selected from the group consisting of copper (Cu), silver (Ag), and aluminum (Al), or a metal alloy containing at least one element selected from this group. Silver is exemplified as the material for metal layer 143. The length (thickness d3) of metal layer 143 in the Z-axis direction is, for example, 40 nm.

[0104] Furthermore, to improve adhesion between dielectric layer 42 and metal layer 143, an adhesion layer 148 may be formed on dielectric layer 42, and metal layer 143 may be formed on adhesion layer 148. The method for forming adhesion layer 148 is the same as the method for forming adhesion layer 46, and therefore a detailed description thereof will be omitted. Chromium (Cr), for example, is used to form adhesion layer 148.

[0105] Next, metal layer 144 is formed on metal layer 143. The method for forming metal layer 144 is the same as that for metal layer 41, so a detailed description is omitted. Furthermore, metal layer 144 is formed using a metal material composed of any metal selected from the group consisting of gold (Au), ruthenium (Ru), and iridium (Ir), or a metal alloy containing at least one element selected from the group consisting of gold (Au), ruthenium (Ru), and iridium (Ir). Gold is exemplified as the material for metal layer 144. The length of metal layer 144 in the Z-axis direction is, for example, 10 nm. The above steps yield laminate 40.

[0106] <Resist Film Formation Step S12>

[0107] After the preparation step S11, the resist film forming step S12 is performed. The resist film forming step S12 is a step of forming a resist film 51 (photoresist) on the metal layer 144. Figure 11 As shown, in the resist film forming step S12, a liquid resist is applied on the metal layer 144 using a spin coater or the like and then dried to form a resist film 51. The resist film 51 has a film thickness of, for example, 230 nm.

[0108] <Pattern Formation Step S13>

[0109] The pattern forming step S13 is performed after the resist film forming step S12. The pattern forming step S13 is a step of forming a pattern 51p on the resist film 51. The pattern 51p is used to form the metal unit 45 constituting the metasurface reflector 30. Figure 12 As shown, in the pattern forming step S13, a pattern 51p corresponding to the metal cell 45 is transferred to the resist film 51 using an exposure device such as a KrF exposure device or an electron beam exposure device. Then, the pattern 51p transferred to the resist film 51 is developed using a developing device.

[0110] <First Protective Film Formation Step S14>

[0111] Following the pattern forming step S13, the first protective film forming step S14 is performed. The first protective film forming step S14 is a step of polishing the metal layer 143 and the metal layer 144 using the pattern 51p to form the metal unit 45 in the metal layer 143 and forming the first portion 44a (first protective film) covering the top surface 45a of the metal unit 45 in the metal layer 144. Figure 13 As shown, in the first protective film forming step S14, ion beam irradiation is performed by ion milling until the dielectric layer 42 is exposed. As a result, the portions of the metal layers 144, 143, and the adhesion layer 148 not covered by the pattern 51p are removed, forming the first portion 44a, the metal unit 45, and the adhesion layer 48.

[0112] <Second Protective Film Formation Step S15>

[0113] Following the first protective film forming step S14, the second protective film forming step S15 is performed. The second protective film forming step S15 is a step for forming the second portion 44b (second protective film) on the side surface 45c of the metal element 45. The second protective film forming step S15 includes a resist film removing step S16, a metal film forming step S17, and a metal film removing step S18.

[0114] <Resist film removal step S16>

[0115] The resist film removal step S16 is a step of removing the resist film 51. Figure 14 As shown in FIG. 1 , the resist film 51 is removed using an organic solvent (NMP).

[0116] <Metal Film Formation Step S17>

[0117] Following the resist film removal step S16, a metal film forming step S17 is performed. The metal film forming step S17 is a step of forming a metal film 52 on the surface 130a of the structure 130. The surface 130a includes the top surface of the first portion 44a, the side surfaces of the first portion 44a, the side surfaces 45c of the metal unit 45, and the portion of the main surface 42a of the dielectric layer 42 not covered by the metal unit 45.

[0118] In the metal film forming step S17, the metal film 52 is formed by vacuum film formation using oblique incident sputtering. Figure 15 As shown, the rotation axis AX of the structure 130 is set in the normal direction of the main surface 42a of the dielectric layer 42. The target T is configured so that the metal particles emitted from the target T are incident at an angle of incidence α. In other words, the angle formed by the normal direction of the main surface Ta of the target T and the normal direction of the main surface 42a of the dielectric layer 42 (the rotation axis AX) is set as the angle of incidence α. The main surface Ta is the surface from which the metal particles are emitted. The angle of incidence α is, for example, 67°. In addition, sputtering is performed while the structure 130 is rotated about the rotation axis AX. As a result, the metal particles enter between two adjacent metal units 45 and form a metal film 52 in a manner that covers the entire surface 130a.

[0119] Metal film 52 is formed using a metal material composed of any metal selected from the group consisting of gold (Au), ruthenium (Ru), and iridium (Ir), or a metal alloy containing at least one element selected from this group. Gold is exemplified as the material for metal film 52. The thickness of metal film 52 is, for example, 10 nm.

[0120] <Metal film removal step S18>

[0121] The metal film forming step S17 is followed by the metal film removing step S18. The metal film removing step S18 is a step of removing the metal film 52 covering the main surface 42a between two adjacent metal units 45. Figure 16 As shown, anisotropic etching is performed in the direction normal to the main surface 42a (etchback). The entire surface of the metal film 52 is etched until the main surface 42a between two adjacent metal units 45 is exposed. As a result, the metal film 52 covering the upper surface of the first portion 44a and the metal film 52 covering the main surface 42a between the two adjacent metal units 45 are removed. The portion of the metal film 52 covering the side surface of the first portion 44a and the side surface 45c of the metal unit 45 remains, forming the second portion 44b. Through this etchback, the second portion 44b has a thickness that decreases as it moves away from the dielectric layer 42 in the Z-axis direction.

[0122] Through the above steps, the metasurface reflector 30 is formed on the surface 50 a of the substrate 50 .

[0123] Next, refer to Figures 17 to 23 Another example of a method for manufacturing the near-eye wearable device 1 will be described. Figure 17 This is a process diagram showing another example of a method for manufacturing a metasurface reflector. Figure 18 Is used to illustrate Figure 17 FIG. 1 is a diagram showing a resist film forming process. Figure 19 Is used to illustrate Figure 17 The diagram of the pattern forming process is shown. Figure 20 Is used to illustrate Figure 17 FIG. 1 shows a diagram of the first protective film forming step. Figure 21 Is used to illustrate Figure 17 The figure shows the metal film forming process. Figure 22 Is used to illustrate Figure 17 Figure 2 shows the metal film removal process. Figure 23 Is used to illustrate Figure 17 FIG. 1 shows a diagram of the resist film removal process.

[0124] Figure 17 The method M2 shown is a method for manufacturing the metasurface reflector 30. The method M2 includes a preparation step S21, a resist film forming step S22, a pattern forming step S23, a first protective film forming step S24, and a second protective film forming step S25.

[0125] <Preparation Step S21>

[0126] The preparation step S21 is a step of preparing the laminated body 40. The preparation step S21 is the same as the preparation step S11, and therefore detailed description thereof will be omitted.

[0127] <Resist Film Formation Step S22>

[0128] After the preparation step S21, the resist film forming step S22 is performed. The resist film forming step S22 is a step of forming a multilayer resist film 55 including a lower resist film 53 and an upper resist film 54 on the metal layer 144. Figure 18 As shown, in the resist film forming step S22, a liquid resist is applied to the metal layer 144 using a spin coater or the like and then dried to form a lower resist film 53. The thickness of the lower resist film 53 is, for example, 38 nm. Furthermore, a liquid resist is applied to the lower resist film 53 using a spin coater or the like and then dried to form an upper resist film 54. The thickness of the upper resist film 54 is, for example, 250 nm.

[0129] <Pattern Formation Step S23>

[0130] The pattern forming step S23 is performed after the resist film forming step S22. The pattern forming step S23 is a step of forming a pattern 55p on the multilayer resist film 55. The pattern 55p is used to form the metal unit 45 constituting the metasurface reflector 30. Figure 19 As shown, in the pattern forming step S23, a pattern 55p corresponding to the metal element 45 is transferred to the upper resist film 54 using an exposure device such as a KrF exposure machine or an electron beam exposure device. The pattern 55p transferred to the upper resist film 54 is then developed using a developer. At this time, the lower resist film 53 is isotropically dissolved without causing a photoreaction, resulting in an overhang of the lower resist film 53 that is slightly smaller than the upper resist film 54 when viewed from the stacking direction. In other words, the edge of the lower resist film 53 is located inward of the side surface of the upper resist film 54. Furthermore, the position of the edge of the lower resist film 53 is adjusted by the duration of the development process.

[0131] <First Protective Film Formation Step S24>

[0132] Following the pattern forming step S23, the first protective film forming step S24 is performed. The first protective film forming step S24 is a step of polishing the metal layer 143 and the metal layer 144 using the pattern 55p to form the metal unit 45 in the metal layer 143 and forming the first portion 44a (first protective film) covering the top surface 45a of the metal unit 45 in the metal layer 144. Figure 20 As shown, in the first protective film forming step S24, ion beam irradiation is performed by ion milling until the dielectric layer 42 is exposed. As a result, the portions of the metal layers 144, 143, and the adhesion layer 148 not covered by the pattern 55p are removed, forming the first portion 44a, the metal unit 45, and the adhesion layer 48. This results in the structure 230.

[0133] <Second Protective Film Formation Step S25>

[0134] Following the first protective film forming step S24, the second protective film forming step S25 is performed. The second protective film forming step S25 is a step for forming the second portion 44b (second protective film) on the side surface 45c of the metal element 45. The second protective film forming step S25 includes a metal film forming step S26, a metal film removing step S27, and a resist film removing step S28.

[0135] <Metal Film Formation Step S26>

[0136] The metal film forming step S26 is a step of forming a metal film 56 on the surface 230a of the structure 230. The surface 230a includes the upper surface of the upper resist film 54, the side surfaces of the upper resist film 54, the side surfaces of the first portion 44a, the side surfaces 45c of the metal unit 45, and the portion of the main surface 42a of the dielectric layer 42 that is not covered by the metal unit 45.

[0137] In the metal film forming step S26, the metal film 56 is formed by vacuum film formation using oblique incident sputtering. Figure 21 As shown, the rotation axis AX of the structure 230 is set in the direction normal to the main surface 42a of the dielectric layer 42. The target T is configured so that the metal particles emitted from the target T are incident at an angle of incidence β. In other words, the angle formed by the normal direction of the main surface Ta of the target T and the normal direction of the main surface 42a of the dielectric layer 42 (the rotation axis AX) is set as the angle of incidence β. The angle of incidence β is, for example, 0° to 28°. Then, sputtering is performed while the structure 230 is rotated about the rotation axis AX. As a result, the metal particles enter between two adjacent metal units 45.

[0138] Since the edge of the lower resist film 53 is located inward of the side surface of the upper resist film 54, the metal film 56 is not formed at the edge of the lower resist film 53. Therefore, the metal film 56 is formed on the upper surface and side surfaces of the upper resist film 54, the side surfaces of the first portion 44a, the side surfaces 45c of the metal elements 45, and the portion of the main surface 42a of the dielectric layer 42 not covered by the metal elements 45. A gap 56a is formed in the metal film 56 along the edge of the lower resist film 53.

[0139] Metal film 56 is formed using a metal material composed of any metal selected from the group consisting of gold (Au), ruthenium (Ru), and iridium (Ir), or a metal alloy containing at least one element selected from this group. Gold is exemplified as the material for metal film 56. The thickness of metal film 56 is, for example, 10 nm.

[0140] <Metal Film Removal Step S27>

[0141] The metal film forming step S26 is followed by the metal film removing step S27. The metal film removing step S27 is a step of removing the metal film 56 covering the main surface 42a between two adjacent metal units 45. Figure 22 As shown, in the metal film removal step S27, an ion beam is irradiated onto the entire surface of the metal film 56 by ion milling until the main surface 42a between two adjacent metal units 45 is exposed. As a result, the metal film 56 covering the upper surface of the upper resist film 54 and the metal film 56 covering the main surface 42a between two adjacent metal units 45 are removed, leaving the metal film 56 covering the side surfaces of the first portion 44a and the side surfaces 45c of the metal units 45, thereby forming the second portion 44b. Furthermore, the metal film 56 covering the side surfaces of the upper resist film 54 also remains.

[0142] <Resist film removal step S28>

[0143] Following the metal film removal step S27, the resist film removal step S28 is performed. The resist film removal step S28 is a step for removing the multilayer resist film 55. Figure 23 As shown, the organic solvent (NMP) enters the gap 56a and reaches the edge of the lower resist film 53, thereby dissolving the lower resist film 53. As a result, the multilayer resist film 55 and the metal film 56 covering the side surfaces of the upper resist film 54 are removed together.

[0144] Through the above steps, the metasurface reflector 30 is formed on the surface 50 a of the substrate 50 .

[0145] By using the above-described method M1 or method M2, a plurality of metasurface reflectors 30 are formed on a substrate 50. Thus, by cutting the substrate 50, a portion containing one metasurface reflector 30 is obtained. This portion of the substrate 50 is then adhered to a predetermined area of ​​the inner surface 3a of the lens 3, thereby forming a metasurface reflector 30 on the inner surface 3a of the lens 3.

[0146] Next, a frame 2 equipped with the optical engine 20 is prepared, and the lens 3 having the metasurface reflector 30 formed thereon is mounted on the lens ring 2a of the frame 2. The near-eye wearable device 1 is manufactured through the above steps.

[0147] The metasurface reflector 30 can also be formed directly on the inner surface 3a of the lens 3. The method of forming the metasurface reflector 30 on the inner surface 3a of the lens 3 is the same as the method of forming the metasurface reflector 30 on the surface 50a of the substrate 50. In this case, the metasurface reflector 30 is formed in a desired area on the inner surface 3a.

[0148] In the near-eye wearable device 1, projection device 10, and metasurface reflector 30 described above, the metasurface reflector 30 is divided into a plurality of unit areas 31 arranged in the X-axis and Y-axis directions. The X-axis direction runs along the principal surface 42a, and the Y-axis direction runs along the principal surface 42a and intersects (is perpendicular to) the X-axis direction. A metal element 45 is provided in each unit area 31, and a protective layer 44 covers the top surface 45a and side surfaces 45c of the metal element 45. Therefore, when the near-eye wearable device 1, projection device 10, and metasurface reflector 30 are in use, the top surface 45a and side surfaces 45c of the metal element 45 are not exposed to air, thereby reducing the possibility of oxidation and sulfurization of the metal element 45. Furthermore, because the protective layer 44 is composed of a metal having a higher standard electrode potential than the metal constituting the metal layer 43, the protective layer 44 is less susceptible to oxidation and sulfurization than the metal layer 43. Consequently, the optical properties of the near-eye wearable device 1, projection device 10, and metasurface reflector 30 are less likely to change. As a result, it is possible to suppress deterioration of reflection characteristics.

[0149] As the proportion of thickness d4 in thickness d5 increases, the influence of protective layer 44 on the reflective characteristics of metasurface reflector 30 increases. For example, although gold (Au) reflects red light, it tends to absorb green and blue light. Ruthenium and iridium tend to absorb light in the visible light region. Therefore, if the proportion of thickness d4 in thickness d5 increases, the reflective characteristics of metasurface reflector 30 may deteriorate. In contrast, in metasurface reflector 30, thickness d4 is less than 20% of thickness d5. Therefore, protective layer 44 is provided to suppress the influence of protective layer 44 on the reflective characteristics of metasurface reflector 30. Thus, the deterioration of reflective characteristics can be further suppressed.

[0150] Although metals such as molybdenum, titanium, and tungsten are also not easily oxidized and sulfided and have high corrosion resistance, they have a large absorption coefficient in the visible light region. Therefore, when the protective layer 44 is composed of these metals, the reflective characteristics of the metasurface reflector 30 may deteriorate. The absorption coefficients of gold, ruthenium, and iridium in the visible light region are smaller than the absorption coefficients of metals such as molybdenum, titanium, and tungsten in the visible light region. Therefore, when the protective layer 44 is composed of a metal containing at least one element selected from the group consisting of gold, ruthenium, and iridium, the deterioration of the reflective characteristics of the metasurface reflector 30 can be further suppressed.

[0151] The metal unit 45 is a metal body having a trapezoidal shape when viewed from the Z-axis direction. Therefore, compared with a case where the metal unit is composed of multiple metal bodies, the structure of the metal unit 45 can be simplified. This can facilitate the manufacture of the metasurface reflector 30.

[0152] When the length of the metal unit 45 in the X-axis direction is greater than 500nm and less than 2500nm, a reflected light Lr corresponding to a field of view angle of 40° to 60° can be obtained. When the thickness d3 is greater than 10nm and less than 100nm, electromagnetic resonance with the metal layer 41 via the dielectric layer 42 can be effectively generated, resulting in a reflected light Lr with a strong electric field intensity. When the width W1 is greater than 10nm and less than 200nm and the width W2 is greater than 100nm and less than 500nm, the phase difference between the reflected light Lr at the width W1 and the reflected light Lr at the width W2 can be made 360° (2π radians) relative to the visible light laser Ls. As described above, by setting the various dimensions of the metal unit 45 within the above-mentioned range, the reflection efficiency can be improved for visible light.

[0153] Metal layer 43 is composed of a metal containing at least one element selected from the group consisting of silver, aluminum, and copper. Therefore, metal layer 43 can have a relatively high reflectivity in the visible light region and a relatively high electrical conductivity. This enhances the electromagnetic resonance between metal layer 41 and metal layer 43, improving reflection efficiency.

[0154] The dielectric layer 42 is made of a material that is transparent in the visible light region. Therefore, the absorption rate of visible light in the dielectric layer 42 can be suppressed, thereby improving the reflection efficiency of visible light.

[0155] Dielectric layer 42 is composed, for example, of a compound selected from the group consisting of silicon oxide, titanium oxide, magnesium oxide, and aluminum oxide. In this case, dielectric layer 42 has a dielectric constant that does not hinder electromagnetic interaction. This enhances electromagnetic resonance between metal layer 41 and metal layer 43, improving reflection efficiency.

[0156] Thickness d1 is, for example, not less than 50 nm and not more than 1000 nm. Thickness d2 is, for example, not less than 10 nm and not more than 100 nm. In this case, the possibility of dielectric layer 42 obstructing electromagnetic interaction can be reduced, and the possibility of laser light Ls passing through metal layer 41 can be reduced. This can improve reflection efficiency.

[0157] The thinner the second portion 44b, the higher the reflected electric field intensity. Therefore, when the protective layer 44 is configured such that the thickness of the second portion 44b decreases as it moves away from the dielectric layer 42 in the Z-axis direction, the protective layer 44 can be provided to suppress the effect on the reflective characteristics of the metasurface reflector 30. This further suppresses degradation of the reflective characteristics.

[0158] In method M1 of manufacturing a metasurface reflector 30, a pattern 51p is formed on a resist film 51 formed on a metal layer 144 of a stacked body 40, and the metal layers 143 and 144 are polished using the pattern 51p, thereby forming metal units 45 and first portions 44a covering the top surfaces 45a of the metal units 45. In method M2 of manufacturing a metasurface reflector 30, a pattern 55p is formed on a multilayer resist film 55 formed on a metal layer 144 of a stacked body 40, and the metal layers 143 and 144 are polished using the pattern 55p, thereby forming metal units 45 and first portions 44a covering the top surfaces 45a of the metal units 45. Furthermore, second portions 44b are formed on the side surfaces 45c of the metal units 45. In the metasurface reflector 30 manufactured in this manner, since the top surfaces 45a and side surfaces 45c of the metal units 45 are not exposed to air during use, the possibility of oxidation and sulfidation of the metal units 45 is reduced. Furthermore, because the protective layer 44 is composed of a metal having a higher standard electrode potential than the metal constituting the metal layer 43, the protective layer 44 is less susceptible to oxidation and sulfurization than the metal layer 43. Consequently, the optical properties of the metasurface reflector 30 are less likely to change. Consequently, degradation of the reflective properties can be suppressed.

[0159] As described above, in the manufacturing process of the metasurface reflector 30, the resist film is removed using an organic solvent (NMP). At this time, when the metal layer 43 (metal unit 45) is exposed, the metal layer 43 may be corroded by the organic solvent. In contrast, in methods M1 and M2, the resist films 51 and 55 are removed while the top surface 45a of the metal unit 45 is covered by the first portion 44a of the protective layer 44. Since the first portion 44a is composed of a metal having a standard electrode potential greater than that of the metal constituting the metal layer 43, the first portion 44a is less susceptible to corrosion than the metal layer 43. Therefore, in the manufacturing process of the metasurface reflector 30, the possibility of corrosion of the metal layer 43 (metal unit 45) can be reduced, and the corrosion resistance can be improved.

[0160] In method M1, metal film 52 is formed on surface 130a of structure 130 obtained by removing resist film 51, and the portion of metal film 52 formed on main surface 42a of dielectric layer 42 is removed to form second portion 44b. In this way, second portion 44b can be formed on side surface 45c of metal unit 45 using a relatively simple process.

[0161] In method M2, the multilayer resist film 55 is removed while the top surface 45a of the metal unit 45 is covered by the first portion 44a and the side surface 45c of the metal unit 45 is covered by the second portion 44b. Therefore, the top surface 45a and side surface 45c of the metal unit 45 are not exposed to the organic solvent used to remove the multilayer resist film 55, thereby reducing the possibility of corrosion of the metal unit 45. As a result, the deterioration of the reflective characteristics of the metasurface reflector 30 can be further suppressed.

[0162] In the metal film forming step S17, the metal film 52 is formed using oblique-incidence sputtering. This allows metal particles to enter between adjacent metal units 45, making it easier to form the metal film 52 on the side surfaces 45 c of the metal units 45. Similarly, in the metal film forming step S26, the metal film 56 is formed using oblique-incidence sputtering. This allows metal particles to enter between adjacent metal units 45, making it easier to form the metal film 56 on the side surfaces 45 c of the metal units 45. This shortens the time required to manufacture the metasurface reflector 30.

[0163] In addition, the metasurface reflector, projection device, near-eye wearable device, and method for manufacturing the metasurface reflector disclosed herein are not limited to the above-mentioned embodiments.

[0164] The near-eye wearable device 1 may also be VR (Virtual Reality) glasses.

[0165] In the above embodiment, the projection device 10 projects (draws) the image directly onto the retina RE of the user of the near-eye wearable device 1, but the image may also be projected onto the metasurface reflector 30.

[0166] The metasurface reflector 30 may also be applied to devices other than the projection device 10. For example, the metasurface reflector 30 may also be applied to a common image projection surface such as an image screen.

[0167] The plurality of unit regions 31 may include a unit region 31 for a red component, a unit region 31 for a green component, and a unit region 31 for a blue component. The unit regions 31 for the red component, the unit regions 31 for the green component, and the unit regions 31 for the blue component may be arranged in sequence and repeatedly in the X-axis direction. Alternatively, the unit regions 31 for the red component, the unit regions 31 for the green component, and the unit regions 31 for the blue component may also be arranged in sequence and repeatedly in the Y-axis direction.

[0168] In the above embodiment, the metal unit 45 is provided in each unit region 31 of all the unit regions 31 . However, the metal unit 45 may be provided in each unit region 31 of some of the unit regions 31 .

[0169] The method for determining the length Lx is not limited to the method described in the above embodiment. For example, the length Lx of the unit regions 31 located at both ends of the metasurface reflector 30 in the X-axis direction may be determined using the above method, and the length Lx of the unit regions 31 located therebetween may be determined to gradually change from the length Lx of the unit region 31 located at one end of the metasurface reflector 30 in the X-axis direction to the length Lx of the unit region 31 located at the other end.

[0170] The metal unit 45 is not limited to a single trapezoidal metal body, and may be composed of, for example, a plurality of metal bodies arranged in the X-axis direction.

[0171] (Note)

[0172] [Project 1]

[0173] A metasurface reflector, wherein:

[0174] The metasurface reflector has:

[0175] a first metal layer and a second metal layer, wherein the first metal layer and the second metal layer are stacked in a first direction;

[0176] a dielectric layer provided between the first metal layer and the second metal layer in the first direction; and

[0177] a protective layer covering the second metal layer,

[0178] The dielectric layer has a main surface on which the second metal layer is provided.

[0179] The metasurface reflector is divided into a plurality of unit areas arranged in a second direction and a third direction, wherein the second direction is along the main surface, and the third direction is along the main surface and intersects with the second direction.

[0180] The second metal layer includes metal units provided in each unit area of ​​all or part of the plurality of unit areas.

[0181] The protective layer is composed of a metal having a standard electrode potential greater than that of the metal constituting the second metal layer.

[0182] The metal unit has a bottom surface facing the dielectric layer in the first direction, a top surface provided on the opposite side of the bottom surface in the first direction, and a side surface connecting the top surface and the bottom surface.

[0183] The protection layer includes a first portion covering the top surface and a second portion covering the side surface.

[0184] [Project 2]

[0185] The metasurface reflector according to item 1, wherein:

[0186] The thickness of the protective layer is 20% or less of the sum of the length of the second metal layer in the first direction and the thickness of the protective layer.

[0187] [Item 3]

[0188] The metasurface reflector according to item 1 or 2, wherein:

[0189] The metal unit is a metal body having a trapezoidal shape when viewed from the first direction.

[0190] [Item 4]

[0191] The metasurface reflector according to item 3, wherein:

[0192] The length of the metal body in the second direction is 500 nm or more and 2500 nm or less,

[0193] The length of the metal body in the first direction is not less than 10 nm and not more than 100 nm,

[0194] The length of the short side of the metal body is not less than 10 nm and not more than 200 nm,

[0195] The length of the long side of the metal body is greater than the length of the short side and is 100 nm to 500 nm inclusive.

[0196] [Item 5]

[0197] The metasurface reflector according to any one of items 1 to 4, wherein

[0198] The protective layer is composed of a metal including at least one element selected from the group consisting of gold, ruthenium, and iridium.

[0199] [Item 6]

[0200] The metasurface reflector according to any one of items 1 to 5, wherein

[0201] The second metal layer is composed of a metal containing at least one element selected from the group consisting of silver, aluminum, and copper.

[0202] [Item 7]

[0203] The metasurface reflector according to any one of items 1 to 6, wherein

[0204] The dielectric layer is composed of a material that is transparent in the visible light region.

[0205] [Item 8]

[0206] The metasurface reflector according to item 7, wherein:

[0207] The dielectric layer is composed of a compound selected from the group consisting of silicon oxide, titanium oxide, magnesium oxide, and aluminum oxide.

[0208] [Item 9]

[0209] The metasurface reflector according to any one of items 1 to 8, wherein

[0210] The length of the dielectric layer in the first direction is not less than 10 nm and not more than 100 nm,

[0211] The length of the first metal layer in the first direction is greater than or equal to 50 nm and less than or equal to 1000 nm.

[0212] [Item 10]

[0213] The metasurface reflector according to any one of items 1 to 9, wherein

[0214] The thickness of the second portion decreases as it moves away from the dielectric layer in the first direction.

[0215] [Item 11]

[0216] A projection device is mounted on a near-eye wearable device, wherein:

[0217] The projection device has:

[0218] a light source that emits laser light;

[0219] a movable mirror for scanning with the laser light; and

[0220] The metasurface reflector according to any one of items 1 to 10 reflects the laser light after passing through the movable reflector, so that a user wearing the near-eye wearable device can visually recognize an image.

[0221] [Item 12]

[0222] A near-eye wearable device, wherein:

[0223] The near-eye wearable device has:

[0224] The projection device described in item 11; and

[0225] A lens is provided with the metasurface reflector.

[0226] [Item 13]

[0227] A method for manufacturing a metasurface reflector, wherein:

[0228] The manufacturing method of the metasurface reflector comprises the following steps:

[0229] preparing a laminated body in which a first metal layer, a dielectric layer, a second metal layer, and a third metal layer are sequentially laminated in a first direction;

[0230] forming an anti-etching film on the third metal layer;

[0231] forming a pattern for forming a metal unit on the resist film, wherein the metal unit constitutes a metasurface reflector and has a bottom surface facing the dielectric layer in the first direction, a top surface provided on the opposite side of the bottom surface in the first direction, and a side surface connecting the top surface and the bottom surface;

[0232] forming the metal unit and forming a first protective film covering the top surface by grinding the second metal layer and the third metal layer using the pattern; and

[0233] forming a second protective film covering the side surface of the metal unit,

[0234] The first protective film and the second protective film are made of a metal having a standard electrode potential greater than a standard electrode potential of a metal constituting the second metal layer.

[0235] [Item 14]

[0236] The method for manufacturing a metasurface reflector according to item 13, wherein:

[0237] The process of forming the second protective film includes the following steps:

[0238] removing the resist film;

[0239] forming a metal film on the surface of a structure obtained by removing the resist film; and

[0240] The second protective film is formed by removing a portion of the metal film formed on the main surface of the dielectric layer.

[0241] [Item 15]

[0242] The method for manufacturing a metasurface reflector according to item 13, wherein:

[0243] In the step of forming the resist film, a multilayer resist film including a lower resist film and an upper resist film is formed on the third metal layer.

[0244] The process of forming the second protective film includes the following steps:

[0245] forming a metal film on the surface of the structure obtained by the step of forming the first protective film;

[0246] forming the second protective film by removing a portion of the metal film formed on the main surface of the dielectric layer; and

[0247] After the second protective film is formed, the multilayer resist film is removed.

[0248] [Item 16]

[0249] The method for manufacturing a metasurface reflector according to item 14 or 15, wherein:

[0250] In the step of forming the metal film, the metal film is formed by oblique-incidence sputtering.

Claims

1. A metasurface reflector, wherein: The metasurface reflector has: a first metal layer and a second metal layer, wherein the first metal layer and the second metal layer are stacked in a first direction; a dielectric layer provided between the first metal layer and the second metal layer in the first direction; and a protective layer covering the second metal layer, The dielectric layer has a main surface on which the second metal layer is provided. The metasurface reflector is divided into a plurality of unit areas arranged in a second direction and a third direction, wherein the second direction is along the main surface, and the third direction is along the main surface and intersects with the second direction. The second metal layer includes metal units provided in each unit area of ​​all or part of the plurality of unit areas. The protective layer is composed of a metal having a standard electrode potential greater than that of the metal constituting the second metal layer. The metal unit has a bottom surface facing the dielectric layer in the first direction, a top surface provided on the opposite side of the bottom surface in the first direction, and a side surface connecting the top surface and the bottom surface. The protection layer includes a first portion covering the top surface and a second portion covering the side surface.

2. The metasurface reflector according to claim 1, wherein: The thickness of the protective layer is 20% or less of the sum of the length of the second metal layer in the first direction and the thickness of the protective layer.

3. The metasurface reflector according to claim 1 or 2, wherein: The metal unit is a metal body having a trapezoidal shape when viewed from the first direction.

4. The metasurface reflector according to claim 3, wherein: The length of the metal body in the second direction is 500 nm or more and 2500 nm or less, The length of the metal body in the first direction is not less than 10 nm and not more than 100 nm, The length of the short side of the metal body is not less than 10 nm and not more than 200 nm, The length of the long side of the metal body is greater than the length of the short side and is 100 nm to 500 nm inclusive.

5. The metasurface reflector according to any one of claims 1 to 4, wherein: The protective layer is composed of a metal including at least one element selected from the group consisting of gold, ruthenium, and iridium.

6. The metasurface reflector according to any one of claims 1 to 5, wherein: The second metal layer is composed of a metal containing at least one element selected from the group consisting of silver, aluminum, and copper.

7. The metasurface reflector according to any one of claims 1 to 6, wherein: The dielectric layer is composed of a material that is transparent in the visible light region.

8. The metasurface reflector according to claim 7, wherein: The dielectric layer is composed of a compound selected from the group consisting of silicon oxide, titanium oxide, magnesium oxide, and aluminum oxide.

9. The metasurface reflector according to any one of claims 1 to 8, wherein: The length of the dielectric layer in the first direction is not less than 10 nm and not more than 100 nm, A length of the first metal layer in the first direction is greater than or equal to 50 nm and less than or equal to 1000 nm.

10. The metasurface reflector according to any one of claims 1 to 9, wherein: The thickness of the second portion decreases as it moves away from the dielectric layer in the first direction.

11. A projection device, mounted on a near-eye wearable device, wherein: The projection device has: a light source that emits laser light; a movable mirror for scanning with the laser light; and The metasurface reflector according to any one of claims 1 to 10, which reflects the laser light after passing through the movable reflector, allowing a user wearing the near-eye wearable device to visually recognize an image.

12. A near-eye wearable device, wherein: The near-eye wearable device has: The projection device according to claim 11; and A lens is provided with the metasurface reflector.

13. A method for manufacturing a metasurface reflector, wherein: The manufacturing method of the metasurface reflector comprises the following steps: preparing a laminated body in which a first metal layer, a dielectric layer, a second metal layer, and a third metal layer are sequentially laminated in a first direction; forming an anti-etching film on the third metal layer; forming a pattern for forming a metal unit on the resist film, wherein the metal unit constitutes a metasurface reflector and has a bottom surface facing the dielectric layer in the first direction, a top surface provided on the opposite side of the bottom surface in the first direction, and a side surface connecting the top surface and the bottom surface; grinding the second metal layer and the third metal layer using the pattern to form the metal unit and form a first protective film covering the top surface; as well as forming a second protective film covering the side surface of the metal unit, The first protective film and the second protective film are made of a metal having a standard electrode potential greater than a standard electrode potential of a metal constituting the second metal layer.

14. The method for manufacturing a metasurface reflector according to claim 13, wherein: The process of forming the second protective film includes the following steps: removing the resist film; forming a metal film on the surface of the structure obtained by removing the resist film; as well as The second protective film is formed by removing a portion of the metal film formed on the main surface of the dielectric layer.

15. The method for manufacturing a metasurface reflector according to claim 13, wherein: In the step of forming the resist film, a multilayer resist film including a lower resist film and an upper resist film is formed on the third metal layer. The process of forming the second protective film includes the following steps: forming a metal film on the surface of the structure obtained by the step of forming the first protective film; forming the second protective film by removing a portion of the metal film formed on the main surface of the dielectric layer; as well as After the second protective film is formed, the multilayer resist film is removed.

16. The method for manufacturing a metasurface reflector according to claim 14 or 15, wherein: In the step of forming the metal film, the metal film is formed by oblique-incidence sputtering.

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