Meta surface reflector, projection device, and near eye wearable device

Abstract

To reduce unnecessary scattering light.SOLUTION: A meta surface reflector includes a first metal layer and a second metal layer that are stacked in a first direction, and a dielectric layer provided between the first metal layer and the second metal layer in the first direction. The dielectric layer has a main surface where the second metal layer is provided. The meta surface reflector is sectioned into a plurality of unit regions that is arranged in a second direction extending along the main surface and a third direction extending along the main surface and intersecting with the second direction. The second metal layer includes a metal unit provided in all or some unit regions among the plurality of unit regions. The lengths of the metal units in the second direction set for the same wavelength among the metal units arranged in the second direction are different from each other.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to metasurface reflectors, projection devices, and near-eye wearable devices. [Background technology]

[0002] Reflectors using metasurface technology are known. For example, Non-Patent Document 1 describes a metasurface reflector in which multiple trapezoidal antennas are arranged two-dimensionally. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Zhiwei Li, Lirong Huang, Kun Lu, Yali Sun, Li Min, “Continuous metasurface for high-performance anomalous reflection”, Applied Physics Express, The Japan Society of Applied Physics, October 7, 2014, Volume 7 Summary of the Invention [Problem to be solved by the invention]

[0004] In the metasurface reflector described in Non-Patent Document 1, trapezoidal antennas of the same shape are regularly arranged in two dimensions. Therefore, the multiple trapezoidal antennas arranged in the vertical and horizontal directions have periodicity. This periodicity may cause unnecessary scattered light.

[0005] This disclosure describes metasurface reflectors, projection devices, and near-eye wearable devices that can reduce unwanted scattered light. [Means for solving the problem]

[0006] A metasurface reflector according to one aspect of the present disclosure includes a first metal layer and a second metal layer stacked in a first direction, and a dielectric layer provided between the first metal layer and the second metal layer in the first direction. 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 along the main surface and a third direction along the main surface and intersecting the second direction. The second metal layer includes metal units provided in all or some of the plurality of unit areas. The lengths in the second direction of the metal units set for the same wavelength among the metal units arranged in the second direction are different from each other.

[0007] In this metasurface reflector, the lengths in the second direction of the metal units set for the same wavelength among the metal units arranged in the second direction are different from each other. For example, when the lengths in the second direction of the metal units provided in a unit area within a certain range are made the same, the metal units of the same length are arranged in the second direction, and periodicity of the metal units occurs in the second direction. On the other hand, in the above metasurface reflector, periodicity of the metal units is unlikely to occur in the second direction, so that the possibility of unnecessary scattered light occurring in the second direction can be reduced. As a result, it is possible to reduce unnecessary scattered light.

[0008] The metal unit may be configured such that the amount of phase change of the reflected light changes linearly from the first end to the second end in the second direction of the unit area in which the metal unit is provided. The length of the metal unit in the second direction may be determined from the wavelength of the reflection target, the angle of incidence and the angle of reflection according to the position of the unit area in which the metal unit is provided. In this case, a plane wave may be generated having, as a wave vector, the slope of a function indicating the relationship between the position in the second direction and the amount of phase change of the reflected light. Therefore, by adjusting the length of the metal unit in the second direction, it is possible to obtain a desired angle of reflection for the angle of incidence according to the position of the unit area. Therefore, since the angle of reflection changes smoothly in the second direction, it is possible to suppress bleeding of light.

[0009] 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 when the metal unit is composed of multiple metal bodies. Therefore, it is possible to facilitate the manufacture of the metasurface reflector.

[0010] The length of the metal body in the second direction may be 500 nm or more and 2500 nm or less. The length of the metal body in the first direction may be 10 nm or more and 100 nm or less. The length of the short side of the metal body may be 10 nm or more and 200 nm or less. The length of the long side of the metal body may be greater than the length of the short side, and may be 100 nm or more and 500 nm or less. In this case, the reflection efficiency for visible light can be increased.

[0011] The multiple unit regions may include a reflective region in which a metal unit is provided, and a missing region in which no metal unit is provided. In the arrangement in the third direction, the reflective region and the missing region may be irregularly arranged. In this case, the metal units are irregularly arranged in the third direction. Therefore, the periodicity of the metal units is unlikely to occur in the third direction, and the possibility of unnecessary scattered light occurring in the third direction can be reduced. As a result, it is possible to further reduce unnecessary scattered light.

[0012] In the arrangement in the second direction, the reflective regions and the missing regions may be arranged irregularly. In this case, the metal units are arranged irregularly in the second direction. Therefore, the periodicity of the metal units is even less likely to occur in the second direction, so that the possibility of unwanted scattered light occurring in the second direction can be further reduced. As a result, it is possible to further reduce unwanted scattered light.

[0013] The number of missing regions may be 10% to 20% of the total number of unit regions included in the metasurface reflector, which can reduce unnecessary scattered light while suppressing a decrease in the intensity of the reflected light.

[0014] The plurality of unit regions may include a first unit region for a red component, a second unit region for a green component, and a third unit region for a blue component. The first unit region, the second unit region, and the third unit region may be arranged repeatedly in that order in the second and third directions. The lengths in the second direction of the metal units provided in the first unit regions arranged in the second direction may be different from each other. The lengths in the second direction of the metal units provided in the second unit regions arranged in the second direction may be different from each other. The lengths in the second direction of the metal units provided in the third unit regions arranged in the second direction may be different from each other. The reflection angle of the metal units varies depending on the wavelength. For this reason, there is a risk that the laser light having a plurality of wavelength components is not reflected at a desired reflection angle. In the above configuration, since the first unit region for the red component, the second unit region for the green component, and the third unit region for the blue component are provided, each component can be reflected at a desired reflection angle. Furthermore, since the lengths of the metal units for the same wavelength component are different from each other, periodicity of the metal units is unlikely to occur in the second direction. Therefore, it is possible to reduce the possibility of unwanted scattered light occurring in the second direction, which in turn makes it possible to reflect each component of the laser light at a desired reflection angle while reducing unwanted scattered light.

[0015] The second metal layer may be made of a metal containing at least one element selected from the group consisting of silver, aluminum, copper, and gold. In this case, a second metal layer having a relatively high reflectance and a relatively high electrical conductivity is obtained. Therefore, the electromagnetic resonance between the first metal layer and the second metal layer can be strengthened, and the reflection efficiency can be increased.

[0016] The dielectric layer may be made of a material that is transparent in the visible light region, in which case the visible light absorption rate in the dielectric layer is reduced, thereby increasing the visible light reflection efficiency.

[0017] The dielectric layer may be made of one 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 inhibit electromagnetic action is obtained. Therefore, the electromagnetic resonance between the first metal layer and the second metal layer can be strengthened, and the reflection efficiency can be increased.

[0018] The length of the dielectric layer in the first direction may be 10 nm or more and 100 nm or less. The length of the first metal layer in the first direction may be 50 nm or more and 1000 nm or less. In this case, the possibility that the dielectric layer inhibits electromagnetic action can be reduced, and the possibility that the laser light transmits through the first metal layer can be reduced. Therefore, the reflection efficiency can be increased.

[0019] A projection device according to another aspect of the present disclosure is a projection device mounted on a near-eye wearable device, the projection device including 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 that has passed through the movable mirror and allows a user wearing the near-eye wearable device to view an image. This projection device can also reduce unnecessary scattered light.

[0020] According to yet another aspect of the present disclosure, there is provided a near-eye wearable device including the projection device and a lens having the metasurface reflector. This near-eye wearable device can also reduce unnecessary scattered light. Effect of the Invention

[0021] According to each aspect and embodiment of the present disclosure, unnecessary scattered light can be reduced. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a perspective view showing the appearance of a near-eye wearable device to which a metasurface reflector according to one embodiment is applied. [Diagram 2] FIG. 2 is a schematic diagram of the projection device shown in FIG. [Diagram 3] FIG. 3 is an enlarged view of the metasurface reflector shown in FIG. [Figure 4] FIG. 4 is a perspective view that illustrates a schematic representation of the reflective area shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a diagram for explaining the principle of reflection by the metasurface reflector shown in FIG. [Figure 7] FIG. 7 is a diagram showing the amount of phase change of reflected light at a position in the X-axis direction of the metasurface reflector. [Figure 8] FIG. 8 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. [Figure 9] FIG. 9 is a diagram showing the relationship between the proportion of missing areas and the intensities of unnecessary scattered light and reflected light. [Figure 10] FIG. 10 is a plan view that illustrates a schematic diagram of another example of the metasurface reflector shown in FIG. [Figure 11] FIG. 11 is a plan view that illustrates a schematic diagram of yet another example of the metasurface reflector shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same elements are given the same symbols, and duplicated descriptions are omitted. An XYZ coordinate system may be shown in each drawing. The Y-axis direction (third direction) is a direction that intersects (e.g., perpendicular to) the X-axis direction (second direction) and the Z-axis direction (first direction). The Z-axis direction is a direction that intersects (e.g., perpendicular to) the X-axis direction and the Y-axis direction. In this specification, a numerical range indicated using "~" indicates a range that includes the numerical values ​​written before and after "~" as the minimum and maximum values, respectively. Individually described upper and lower limit values ​​can be arbitrarily combined.

[0024] A near-eye wearable device to which a metasurface reflector according to an embodiment is applied will be described with reference to FIG. 1. FIG. 1 is a perspective view showing the appearance of a near-eye wearable device to which a metasurface reflector according to an embodiment is applied. The near-eye wearable device 1 shown in FIG. 1 is a device that overlays an image on a field of view in the real world. The near-eye wearable device 1 is, for example, a head-mounted device, and may take the form of glasses, goggles, hats, helmets, and the like. 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, a lens 3, and a projection device 10.

[0025] The frame 2 includes a pair of rims 2a, a bridge 2b, and a pair of temples 2c. The rims 2a are portions that hold the lenses 3. The bridge 2b is a portion that connects the pair of rims 2a. The temples 2c are portions that extend from the rims 2a and are hung on the ears of a user. The frame 2 may be a rimless frame. The lenses 3 have an inner surface 3a (see FIG. 2) that faces the eyeball E (see FIG. 6) of a user wearing the near eyewear wearable device 1.

[0026] In this embodiment, the projection device 10 is a device that directly projects (draws) an image onto the retina RE (see FIG. 6) of a user wearing the near-eye wearable device 1. The projection device 10 is mounted on the near-eye wearable device 1. In this embodiment, the near-eye wearable device 1 includes two projection devices 10 in order to project images onto both the left and right retinas RE, but may include only one of the projection devices 10.

[0027] Next, the projection device 10 will be described in detail with reference to Fig. 2. Fig. 2 is a schematic diagram of the projection device shown in Fig. 1. As shown in Fig. 2, the projection device 10 includes an optical engine 20 and a metasurface reflector 30.

[0028] The optical engine 20 is a device that generates laser light Ls with a color and intensity corresponding to the pixels of an image to be projected onto the retina RE, and emits the laser light Ls to 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), an optical component 22, a movable mirror 23, a laser driver 24, a mirror driver 25, and a controller 26.

[0029] 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 multiplexing section that multiplexes the laser light emitted from each laser diode into one laser light. The light source unit 21 emits the multiplexed laser light. The multiplexed laser light includes a component having a red wavelength (red component), a component having a green wavelength (green component), and a component having a blue wavelength (blue component). The light source unit 21 emits laser light of a color and intensity corresponding to the pixels of the image to be projected onto the retina RE.

[0030] The optical component 22 is a component that optically processes the laser light emitted from the light source unit 21. In this embodiment, the optical component 22 includes a collimator lens 22a, a slit 22b, and a neutral density filter 22c. The collimator lens 22a, the slit 22b, and the neutral density filter 22c are arranged in this order along the optical path of the laser light. The optical component 22 may have other configurations.

[0031] The movable mirror 23 is an optical component for performing scanning with the laser light Ls. The movable mirror 23 is provided in the emission direction of the laser light processed by the optical component 22. The movable mirror 23 is configured to be swingable, for example, around an axis extending in the horizontal direction (X-axis direction) of the lens 3 and around an axis extending in the vertical direction (Y-axis direction) of the lens 3, and reflects the laser light by changing the angle in the X-axis direction and the Y-axis direction. For example, a MEMS (Micro Electro Mechanical Systems) mirror is used as the movable mirror 23.

[0032] 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 oscillates the movable mirror 23 within a predetermined angle range and at a predetermined timing. The controller 26 is a device that controls the laser driver 24 and the mirror driver 25.

[0033] In the optical engine 20, laser light having a color and intensity corresponding to the pixels of an image to be 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 to the metasurface reflector 30 as laser light Ls.

[0034] The metasurface reflector 30 is an optical component that reflects the laser light Ls that has passed through the movable mirror 23, allowing a user wearing the near-eye wearable device 1 to 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.

[0035] Next, the configuration of the metasurface reflector 30 will be described with reference to Figs. 3 to 5. Fig. 3 is an enlarged view of the metasurface reflector shown in Fig. 2. Fig. 4 is a perspective view that shows a schematic view of the reflection region shown in Fig. 3. Fig. 5 is a cross-sectional view taken along line VV in Fig. 4.

[0036] As shown in FIG. 3, the metasurface reflector 30 is divided into a plurality of unit regions 31. The plurality of unit regions 31 are provided along the inner surface 3a of the lens 3. The plurality of unit regions 31 are arranged in a two-dimensional array in the horizontal direction (X-axis direction) and vertical direction (Y-axis direction) of the lens 3. The plurality of unit regions 31 include a reflective region 32 and a missing region 33. The reflective region 32 is a unit region 31 in which a metal unit 45 described below is provided. The missing region 33 is a unit region 31 in which a metal unit 45 is not provided.

[0037] In the array in the Y-axis direction, the reflective regions 32 and the missing regions 33 are irregularly arranged. Hereinafter, the array in the X-axis direction may be referred to as a "row", and the array in the Y-axis direction may be referred to as a "column". The number of missing regions 33 is, for example, 10% to 20% of the total number of unit regions 31 included in the metasurface reflector 30. In this embodiment, all unit regions 31 in the array (one row) in the X-axis direction are set as reflective regions 32 or missing regions 33. For example, the row with the row number corresponding to the random value obtained by the random function is determined to be the row of the missing regions 33.

[0038] 4 and 5, the metasurface reflector 30 includes a metal layer 41 (first metal layer), a dielectric layer 42, and a metal layer 43 (second metal layer) in this order in the Z-axis direction. Note that, although the reflection region 32 is illustrated in Fig. 4 and Fig. 5, the missing region 33 has a similar configuration to the reflection region 32, except that it does not include the metal layer 43.

[0039] The metal layer 41 is a base layer. The metal layer 41 is provided on the inner surface 3a of the lens 3. The metal layer 41 is made of a metal having high reflectivity in the visible light region. The metal layer 41 is made of a metal containing at least one element selected from the group consisting of gold (Au), copper (Cu), silver (Ag), and aluminum (Al), for example. The length (thickness d1) of the metal layer 41 in the Z-axis direction may be a length that allows the metal layer 41 to pass a resonant current and reflect light, and is, for example, 50 nm to 1000 nm. Hereinafter, the length in the Z-axis direction may be referred to as "thickness".

[0040] 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 on which the metal layer 43 is provided. The dielectric layer 42 has a dielectric constant that does not inhibit the electromagnetic action of the metal layer 41 and the metal layer 43. The dielectric layer 42 is made of a material that is transparent in the visible light range. The dielectric layer 42 may be made of a material with a high dielectric constant to achieve high reflection characteristics. The dielectric layer 42 is made of one compound selected from a 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 thickness d2 of the dielectric layer 42 is, for example, 10 nm to 100 nm.

[0041] The metal layer 43 is a layer that excites electromagnetic resonance together with the metal layer 41. The metal layer 41 and the metal layer 43 are stacked in the Z-axis direction via the dielectric layer 42. In this embodiment, the metal layer 43 is provided on the main surface 42a of the dielectric layer 42. The metal layer 43 is made of a metal having high reflectivity in the visible light range. Like the metal layer 41, the metal layer 43 is made of a metal including at least one element selected from the group consisting of gold (Au), copper (Cu), silver (Ag), and aluminum (Al).

[0042] The metal layer 43 includes a metal unit 45. The metal unit 45 is provided in each of some unit regions 31 (reflective regions 32) among the plurality of unit regions 31. The metal unit 45 is configured such that the phase change amount φ of the reflected light Lr by the metal unit 45 changes linearly from one end 32a (first end) to the other end 32b (second end) in the X-axis direction of the reflective region 32 in which the metal unit 45 is provided. Furthermore, the metal unit 45 is configured such that the phase change amount φ of the reflected light Lr changes substantially by 360° (2π radians) from the one end 32a to the other end 32b. The phase change amount φ of the reflected light Lr is the phase change amount 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".

[0043] In this embodiment, the metal unit 45 is a single metal body having a trapezoidal shape when viewed from the Z-axis direction. The thickness d3 of the metal unit 45 is, for example, 10 nm to 100 nm. The length of the metal unit 45 in the X-axis direction is the same as or slightly shorter than the length Lx of the reflective area 32 in the X-axis direction. The length of the metal unit 45 in the X-axis direction is, for example, 500 nm to 2500 nm.

[0044] The length of the short side of the metal unit 45 (width W1) is set, for example, near the resolution of an exposure device used when forming the metal unit 45. The width W1 is, for example, 10 nm to 200 nm. The length of the long side of the metal unit 45 (width W2) is set to be greater than the width W1 and to a length that provides a phase difference of substantially 360° (2π radians) from the phase of the reflected light Lr at the width W1. The width W2 is, for example, 100 nm to 500 nm. The metal unit 45 is formed, for example, by photolithography.

[0045] Next, the principle of reflection by the metasurface reflector 30 and a method of determining the length Lx will be described with reference to Figs. 5 to 8. Fig. 6 is a diagram for explaining the principle of reflection by the metasurface reflector shown in Fig. 2. Fig. 7 is a diagram showing the amount of phase change of reflected light at a position in the X-axis direction of the metasurface reflector. Fig. 8 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.

[0046] As shown in FIGS. 5 and 6, each reflection area 32 has an incidence angle θ corresponding to the position where the reflection area 32 is provided. i When the laser light Ls is incident on the reflective area 32, the reflection angle θ r The nanostructure is configured to reflect the laser light Ls at a reflection angle θ of each reflection region 32 so that the laser light Ls (reflected light Lr) reflected by each reflection region 32 passes through the center of the pupil PP. r Therefore, the incidence angle θ i and reflection angle θ r is determined by the position where the reflection area 32 is provided. i and reflection angle θ r The reflective area 32 is configured so that:

[0047] Here, the incidence angle θ i is the angle between the normal to the surface onto which the laser light Ls is irradiated and the direction of incidence of the laser light Ls. r is the angle between the normal to the surface onto which the laser light Ls is irradiated and the direction of the reflected light Lr. In a plane including the laser light Ls and the reflected light Lr, when the reflected light Lr is emitted on the opposite side of the normal to the incident light (laser light Ls), the reflection angle θ r is expressed as a positive value, and when the reflected light Lr is emitted on the same side as the incident light (laser light Ls) with the normal as the boundary, the reflection angle θ r is expressed as a negative value.

[0048] For example, as shown in Fig. 6, when the user's pupil PP faces forward, the reflection area 32 provided from position Pa to position Pc in the X-axis direction is used. The laser light Ls reflected by the reflection area 32 provided at position Pa corresponds to the pixel at the right edge of the image. Position Pb is located midway between positions Pa and Pc, and the laser light Ls reflected by the reflection area 32 provided at position Pb corresponds to the pixel at the center of the image. The laser light Ls reflected by the reflection area 32 provided at position Pc corresponds to the pixel at the left edge of the image.

[0049] In the reflection area 32 provided at the position Pa, the incident angle θ of 30° i Laser light Ls is incident at a reflection angle of 5° r The laser light Ls is reflected by the reflection area 32 provided at the position Pb and emitted as reflected light Lr. i Laser light Ls is incident at a reflection angle of -5° θ r The laser light Ls is reflected by the reflection area 32 at the position Pc and emitted as reflected light Lr. i Laser light Ls is incident at a reflection angle of -10°. r The laser light Ls is reflected by the reflector 11 and emitted as reflected light Lr.

[0050] As shown in FIG. 7, the width of the metal unit 45 increases from width W1 to width W2 from one end 32a to the other end 32b. The phase change amount φ at each position in the X-axis direction of the metal unit 45 is substantially the same as the phase change amount φ of a square metal body having sides of the same length as the width at that position in a plan view. The larger the area of ​​the square metal body in a plan view, the larger the phase change amount φ (phase delay amount) at that position. Therefore, the laser light Ls is reflected with a phase change amount φ that differs depending on the position in the X-axis direction, and a wavefront is formed by interference between the reflected lights. That is, a plane wave is generated having a wave vector Φ that is the slope of a function φ(x) that indicates the relationship between the position x and the phase change amount φ in the X-axis direction.

[0051] Here, as shown in FIG. 5, Snell's law can be generalized as follows: i , reflection angle θ r and wave vector Φ, as expressed by equation (1).

number

[0052] The wave vector k0 is expressed as 2π / λ using the wavelength λ of the laser light Ls. The wave vector Φ is expressed as 2π / Lx using the length Lx in the X-axis direction of the reflection area 32. By transforming formula (1) using these relationships, formula (2) is obtained.

number

[0053] In formula (2), the wavelength λ of the laser light Ls and the incidence angle θ of the laser light Ls according to the position where the reflection area 32 is provided are i and reflection angle θ r By substituting the above, the length Lx of the reflective region 32 can be obtained. The laser light Ls contains red, green, and blue components, and the length Lx is determined by using, for example, the wavelength λ of the green component to which the human eye is most sensitive.

[0054] 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 32a to the other end 32b. 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 32a to the other end 32b.

[0055] The length Lx of the missing region 33 in the X-axis direction is determined by the wavelength λ of the laser light Ls and the incidence angle θ of the laser light Ls according to the position where the missing region 33 is provided when it is assumed that the missing region 33 is a reflective region 32. i and reflection angle θ r This can be obtained by substituting and into equation (2).

[0056] As described above, the length Lx of each unit area 31 is determined by the wavelength λ of the reflection target and the incident angle θ corresponding to the position where the unit area 31 is provided. i and 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 reflection area 32 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 reflection target and the incident angle θ i and reflection angle θ r It is determined from.

[0057] reflection angle θ r is the incidence angle θ i If the angle of incidence θ is less than θ, the length Lx will be a negative value. i and the reflection angle θ r As the difference between the reflection angle θ and the reflection angle θ increases, the absolute value of the length Lx decreases. r becomes smaller, and the incident angle θ i and the reflection angle θ r As the difference between them increases, the length Lx also decreases. Therefore, the lengths Lx of the unit areas 31 included in the same row are different from each other, and the lengths in the X-axis direction of the metal units 45 included in the same row are also different from each other.

[0058] 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 may be a length obtained by adding the resolution (e.g., 100 nm) of the exposure device used when forming the metal unit 45 to the width W2, and is set to, for example, 600 nm. The widths W1 and W2 of each metal unit 45 are predetermined fixed values. As described above, the width W1 is set to a value close to the resolution (e.g., 100 nm) of the exposure device used when forming the metal unit 45. The width W2 is set to a length (e.g., 350 nm) that provides a phase difference of substantially 360° (2π radians) from the phase of the reflected light Lr at the width W1.

[0059] Next, the effect of the missing region 33 on the intensity of the unnecessary scattered light and the intensity of the reflected light will be described with reference to FIG. 9. FIG. 9 is a diagram showing the relationship between the ratio of the missing region and the intensity of the unnecessary scattered light and the intensity of the reflected light. The horizontal axis of FIG. 9 indicates the ratio (unit: %) of the missing region 33 to all the unit regions 31 included in the metasurface reflector 30. The vertical axis on the left side of FIG. 9 indicates the intensity of the unnecessary scattered light. The vertical axis on the right side of FIG. 9 indicates the intensity of the reflected light. The intensity of the unnecessary scattered light is expressed as a ratio (unit: %) to the intensity of the unnecessary scattered light when all the unit regions 31 included in the metasurface reflector 30 are the reflective regions 32. The intensity of the reflected light is expressed as a ratio (unit: %) to the intensity of the incident light.

[0060] Graph G1 is a graph showing the relationship between the ratio of missing area 33 and the intensity of unnecessary scattered light. Graph G2 is a graph showing the relationship between the ratio of missing area 33 and the intensity of reflected light. Graphs G1 and G2 were obtained by actual measurements.

[0061] As shown in FIG. 9, as the proportion of missing area 33 increases, the intensity of the unnecessary scattered light decreases exponentially. When the proportion of missing area 33 is 10% or more, the intensity of the unnecessary scattered light is 50% or less. On the other hand, the intensity of the reflected light hardly decreases from 100% if the proportion of missing area 33 is about 15% or less, and starts to decrease when the proportion of missing area 33 exceeds 15%. When the proportion of missing area 33 is 20% or less, the intensity of the reflected light is 50% or more. From the above, it can be seen that when the proportion of missing area 33 is in the range of 10% to 20%, the intensity of the unnecessary scattered light is suppressed to 50% or less, and the intensity of the reflected light is maintained at 50% or more.

[0062] Next, a manufacturing method of the near-eye wearable device 1 will be described. First, the lens 3 is prepared and set in a vacuum film-forming apparatus. Then, a metal layer 41 is formed in a desired area on the inner surface 3a of the lens 3. Specifically, the metal layer 41 is formed by vacuum film-forming using a method such as DC (Direct Current) sputtering. The metal layer 41 is formed using a metal material selected from a 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.

[0063] Subsequently, a dielectric layer 42 is formed on the metal layer 41. Specifically, the dielectric layer 42 is formed by vacuum film formation using a method such as RF (Radio Frequency) sputtering. The dielectric layer 42 is formed using a dielectric material such as silicon dioxide (SiO2), titanium oxide (TiO2), magnesium oxide (MgO), or aluminum oxide (Al2O3) that can be formed by a semiconductor process.

[0064] Next, a metal layer (hereinafter referred to as the "outermost metal layer") that will become metal layer 43 is formed on dielectric layer 42. The method for forming the outermost metal layer is similar to that for metal layer 41, and therefore a detailed description thereof will be omitted.

[0065] Next, a metal layer 43 (a plurality of metal units 45) is formed by a photolithography process and an etching process. Specifically, a liquid resist is applied onto the outermost metal layer using a spin coater or the like, and the applied liquid resist is dried to form a resist film (photoresist). Then, a pattern corresponding to the metal units 45 is transferred onto the resist film using an exposure device such as a KrF exposure device and an electron beam lithography device. Then, the pattern transferred onto the resist film is developed using a developing device. Then, a portion of the outermost metal layer that is not covered by the pattern is removed by ion milling, and then the resist film is removed. This forms the metal layer 43. As a result, a metasurface reflector 30 is formed on the inner surface 3a of the lens 3.

[0066] Next, a frame 2 on which an optical engine 20 is mounted is prepared, and a lens 3 on which a metasurface reflector 30 is formed is attached to a rim 2a of the frame 2. In this manner, the near-eye wearable device 1 is manufactured.

[0067] The metasurface reflector 30 does not have to be formed directly on the inner surface 3a of the lens 3. For example, the metasurface reflector 30 may be formed on a substrate such as a sapphire substrate or a flexible sheet. The method for forming the metasurface reflector 30 on the substrate is the same as the method for forming the metasurface reflector 30 on the lens 3. In this case, a plurality of metasurface reflectors 30 may be formed on the substrate. Then, the substrate is cut to obtain a portion including one metasurface reflector 30. Then, the substrate of that portion is attached to a predetermined region of the inner surface 3a of the lens 3, thereby forming the metasurface reflector 30 on the inner surface 3a of the lens 3.

[0068] In the near eyewear wearable device 1, the projection device 10, and the metasurface reflector 30 described above, the metasurface reflector 30 is divided into a plurality of unit areas 31 arranged in the X-axis direction along the main surface 42a and in the Y-axis direction along the main surface 42a and intersecting (perpendicular to) the X-axis direction, and metal units 45 are provided in the reflection areas 32 of the plurality of unit areas 31. All of the metal units 45 are set for the same wavelength λ. The lengths in the X-axis direction of the metal units 45 included in one arrangement (i.e., one row) in the X-axis direction are different from each other.

[0069] For example, when the lengths of the metal units 45 provided in the reflection region 32 within a certain range in the X-axis direction are made the same, the metal units 45 of the same length are arranged in the X-axis direction, and periodicity of the metal units 45 occurs in the X-axis direction. On the other hand, in the near eyewear device 1, the projection device 10, and the metasurface reflector 30, the metal units 45 of different lengths are arranged in the X-axis direction, so that periodicity of the metal units 45 is unlikely to occur in the X-axis direction. Therefore, it is possible to reduce the possibility of unnecessary scattered light occurring in the X-axis direction. As a result, it is possible to reduce unnecessary scattered light.

[0070] For example, it is possible to make the lengths in the X-axis direction of the metal units 45 provided in the reflective region 32 within a certain range the same for each range. In this case, metal units 45 of the same length in the X-axis direction are arranged within the same range, and the reflection angle θ of the reflected light Lr reflected by these metal units 45 r Therefore, the reflection angle θ between two adjacent ranges is r When the reflected light Lr is combined with the reflected light Lb, a large change occurs, and there is a risk of light bleeding occurring.

[0071] On the other hand, in the near eyewear wearable device 1, the projection device 10, and the metasurface reflector 30, each metal unit 45 is configured so that the phase change amount φ of the reflected light Lr changes linearly from one end 32a to the other end 32b of the reflection area 32 in which the metal unit 45 is provided. This configuration generates a plane wave having a wave vector Φ that is the slope of a function φ(x) that indicates the relationship between the position x in the X-axis direction and the phase change amount φ of the reflected light Lr. In this case, since the above formulas (1) and (2) are satisfied, the incidence angle θ according to the wavelength λ of the reflection target and the position of the reflection area 32 in which the metal unit 45 is provided varies linearly. i and reflection angle θ r Therefore, by adjusting the length of the metal unit 45 in the X-axis direction, the incident angle θ i , the desired reflection angle θ r Therefore, the reflection angle θ r Since the difference between the light intensity and the reflection intensity changes smoothly, it is possible to suppress light bleeding.

[0072] In the arrangement in the Y-axis direction, the reflective regions 32 and the missing regions 33 are irregularly arranged. Therefore, the metal units 45 are irregularly arranged in the Y-axis direction. Therefore, the periodicity of the metal units 45 is unlikely to occur in the Y-axis direction, so that the possibility of unnecessary scattered light occurring in the Y-axis direction can be reduced. As a result, it is possible to further reduce unnecessary scattered light.

[0073] The number of missing regions 33 is 10% or more and 20% or less of the total number of unit regions 31 included in the metasurface reflector 30. With this configuration, it is possible to reduce unnecessary scattered light while suppressing a decrease in the intensity of the reflected light.

[0074] The metal unit 45 is a metal body having a trapezoidal shape when viewed from the Z-axis direction. Therefore, the structure of the metal unit 45 can be simplified compared to a case where the metal unit is composed of multiple metal bodies. Therefore, it is possible to facilitate the manufacture of the metasurface reflector 30.

[0075] When the length of the metal unit 45 in the X-axis direction is 500 nm or more and 2500 nm or less, the reflected light Lr corresponding to a viewing angle of 40° to 60° can be obtained. When the thickness d3 is 10 nm or more and 100 nm or less, electromagnetic resonance with the metal layer 41 via the dielectric layer 42 is effectively generated, and the reflected light Lr with a strong electric field intensity can be obtained. When the width W1 is 10 nm or more and 200 nm or less, and the width W2 is 100 nm or more and 500 nm or less, it is possible to make the phase difference between the phase of the reflected light Lr at the width W1 and the phase of the reflected light Lr at the width W2 360° (2π radians) for the visible laser light Ls. From the above, by setting each dimension of the metal unit 45 within the above-mentioned range, the reflection efficiency for visible light can be increased.

[0076] The metal layer 43 is made of a metal containing at least one element selected from the group consisting of silver, aluminum, copper, and gold. Therefore, the metal layer 43 has a relatively high reflectance in the visible light region and a relatively high electrical conductivity. Therefore, the electromagnetic resonance between the metal layer 41 and the metal layer 43 can be strengthened, and the reflection efficiency can be increased.

[0077] The dielectric layer 42 is made of a material that is transparent in the visible light region, which reduces the visible light absorption rate in the dielectric layer 42, thereby improving the visible light reflection efficiency.

[0078] The dielectric layer 42 is made of, for example, one compound selected from the group consisting of silicon oxide, titanium oxide, magnesium oxide, and aluminum oxide. In this case, the dielectric layer 42 has a dielectric constant that does not inhibit electromagnetic action. Therefore, the electromagnetic resonance between the metal layer 41 and the metal layer 43 can be strengthened, and the reflection efficiency can be increased.

[0079] The thickness d1 is, for example, 50 nm or more and 1000 nm or less. The thickness d2 is, for example, 10 nm or more and 100 nm or less. In this case, the possibility that the dielectric layer 42 inhibits the electromagnetic action can be reduced, and the possibility that the laser light Ls transmits through the metal layer 41 can be reduced. Therefore, the reflection efficiency can be increased.

[0080] It should be noted that the metasurface reflector, projection device, and near-eye wearable device according to the present disclosure are not limited to the above embodiments.

[0081] The near-eye wearable device 1 may be a pair of virtual reality (VR) glasses.

[0082] In the above embodiment, the projection device 10 projects (draws) an image directly onto the retina RE of the user of the near eyewear wearable device 1, but the image may also be projected onto the metasurface reflector 30.

[0083] The metasurface reflector 30 may be applied to devices other than the projection device 10. For example, the metasurface reflector 30 may be applied to a general image projection surface such as a video screen.

[0084] The multiple unit regions 31 may not include a missing region 33. That is, the metal units 45 may be provided in each of all of the multiple unit regions 31. Even in this case, the lengths in the X-axis direction of the metal units 45 included in one array in the X-axis direction (i.e., one row) are different from each other. Therefore, periodicity of the metal units 45 in the X-axis direction is unlikely to occur, and it is possible to reduce the possibility of unnecessary scattered light occurring in the X-axis direction.

[0085] As shown in Fig. 10, the reflective regions 32 and the missing regions 33 may be irregularly arranged in the arrangement in the X-axis direction as well. In this case, the number of missing regions 33 is, for example, 10% to 20% of the total number of unit regions 31 included in the metasurface reflector 30. In the example shown in Fig. 10, all the unit regions 31 in one column are set as reflective regions 32 or as missing regions 33. For example, the column with the column number corresponding to the random value obtained by the random function is determined as the column of missing regions 33.

[0086] According to the configuration in which the reflective regions 32 and the missing regions 33 are irregularly arranged in the array in the X-axis direction, the metal units 45 are irregularly arranged in the X-axis direction. Therefore, the periodicity of the metal units 45 in the X-axis direction is further unlikely to occur, so that the possibility of unnecessary scattered light occurring in the X-axis direction can be further reduced. In this case, too, by setting the number of missing regions 33 to be 10% or more and 20% or less of the total number of unit regions 31 included in the metasurface reflector 30, unnecessary scattered light can be reduced while suppressing a decrease in the intensity of the reflected light.

[0087] 11, the multiple unit areas 31 may include a unit area 31R (first unit area) for a red component, a unit area 31G (second unit area) for a green component, and a unit area 31B (third unit area) for a blue component. In the X-axis direction, the unit area 31R, the unit area 31G, and the unit area 31B are repeatedly arranged in that order. In the Y-axis direction, the unit area 31R, the unit area 31G, and the unit area 31B are also repeatedly arranged in that order.

[0088] The plurality of unit regions 31R include a reflective region 32R and a missing region 33R. The reflective region 32R is the unit region 31R in which the metal unit 45 is provided. The missing region 33R is the unit region 31R in which the metal unit 45 is not provided. The plurality of unit regions 31G include a reflective region 32G and a missing region 33G. The reflective region 32G is the unit region 31G in which the metal unit 45 is provided. The missing region 33G is the unit region 31G in which the metal unit 45 is not provided. The plurality of unit regions 31B include a reflective region 32B and a missing region 33B. The reflective region 32B is the unit region 31B in which the metal unit 45 is provided. The missing region 33B is the unit region 31B in which the metal unit 45 is not provided.

[0089] As in the example shown in FIG. 3, the reflective regions 32R, 32G, 32B and the missing regions 33R, 33G, 33B may be irregularly arranged in the Y-axis direction. The total number of the missing regions 33R, 33G, 33B is, for example, 10% to 20% of the total number of the unit regions 31 included in the metasurface reflector 30. In the example shown in FIG. 11, the row with the row number corresponding to the random value obtained by the random function is determined to be the row of the missing regions 33R, 33G, 33B. As in the example shown in FIG. 10, the reflective regions 32R, 32G, 32B and the missing regions 33R, 33G, 33B may be irregularly arranged in the X-axis direction.

[0090] In this modification, the incidence angle θ i and reflection angle θ r The reflective areas 32R, 32G, and 32B are configured so as to obtain the above. Therefore, the lengths in the X-axis direction of the metal units 45 provided in the unit areas 31R (reflective areas 32R) included in one row are different from each other. Similarly, the lengths in the X-axis direction of the metal units 45 provided in the unit areas 31G (reflective areas 32G) included in one row are different from each other. The lengths in the X-axis direction of the metal units 45 provided in the unit areas 31B (reflective areas 32B) included in one row are different from each other.

[0091] Reflection angle θ by metal unit 45 r varies depending on the wavelength λ. Therefore, the laser light Ls having red, green, and blue components is reflected at a desired reflection angle θ r In the configuration of the above modification, the unit area 31R for the red component, the unit area 31G for the green component, and the unit area 31B for the blue component are provided, so that each component can be reflected at a desired reflection angle θ r In addition, since the lengths in the X-axis direction of the metal units 45 for the same wavelength component are different from each other, periodicity of the metal units 45 in the X-axis direction is unlikely to occur. Therefore, it is possible to reduce the possibility of unwanted scattered light occurring in the X-axis direction. As a result, each component of the laser light Ls can be reflected at a desired reflection angle θ while reducing unwanted scattered light. r It is possible to reflect the light.

[0092] The method of determining the length Lx is not limited to the method described in the above embodiment. For example, the length Lx of the unit area 31 located at both ends in the X-axis direction of the metasurface reflector 30 may be determined by the above-mentioned method, and the length Lx of the unit area 31 located therebetween may be determined so as to gradually change from the length Lx of the unit area 31 located at one end in the X-axis direction of the metasurface reflector 30 to the length Lx of the unit area 31 located at the other end.

[0093] The metal unit 45 is not limited to a single trapezoidal metal body, and may be configured, for example, by a plurality of metal bodies arranged in the X-axis direction.

[0094] (Additional Note) [Clause 1] A metasurface reflector, 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; Equipped with 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 along the main surface and a third direction along the main surface and intersecting the second direction; the second metal layer includes metal units provided in all or some of the unit areas, A metasurface reflector, wherein the lengths in the second direction of the metal units set for the same wavelength among the metal units arranged in the second direction are different from each other.

[0095] [Clause 2] The metal unit is configured such that an amount of phase change of reflected light changes linearly from a first end to a second end in the second direction of a unit area in which the metal unit is provided, The metasurface reflector described in clause 1, wherein the length of the metal unit in the second direction is determined from the wavelength to be reflected, the angle of incidence and the angle of reflection depending on the position of the unit area in which the metal unit is provided.

[0096] [Clause 3] The metasurface reflector described in clause 1 or clause 2, wherein the metal unit is a metal body having a trapezoidal shape when viewed from the first direction.

[0097] [Article 4] 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 10 nm or more and 200 nm or less, The metasurface reflector described in clause 3, wherein the length of the long side of the metal body is greater than the length of the short side and is greater than or equal to 100 nm and less than or equal to 500 nm.

[0098] [Article 5] the plurality of unit areas include a reflective area in which the metal unit is provided and a missing area in which the metal unit is not provided, The metasurface reflector described in any one of clauses 1 to 4, wherein in the arrangement in the third direction, the reflective regions and the missing regions are irregularly arranged.

[0099] [Article 6] The metasurface reflector described in clause 5, wherein in the arrangement in the second direction, the reflective regions and the missing regions are irregularly arranged.

[0100] [Article 7] The metasurface reflector described in clause 5 or clause 6, wherein the number of missing regions is greater than or equal to 10% and less than or equal to 20% of the total number of unit regions included in the metasurface reflector.

[0101] [Article 8] the plurality of unit areas include a first unit area for a red component, a second unit area for a green component, and a third unit area for a blue component; the first unit area, the second unit area, and the third unit area are repeatedly arranged in that order in the second direction and the third direction; The lengths in the second direction of the metal units provided in the first unit regions arranged in the second direction are different from each other, The lengths in the second direction of the metal units provided in the second unit areas arranged in the second direction are different from each other, The metasurface reflector described in any one of clauses 1 to 7, wherein the lengths in the second direction of the metal units provided in the third unit regions arranged in the second direction are different from each other.

[0102] [Article 9] The metasurface reflector of any one of clauses 1 to 8, wherein the second metal layer is composed of a metal including at least one element selected from the group consisting of silver, aluminum, copper, and gold.

[0103] [Article 10] The metasurface reflector of any one of claims 1 to 9, wherein the dielectric layer is made of a material that is transparent in the visible light region.

[0104] [Article 11] The metasurface reflector of claim 10, wherein the dielectric layer is composed of a compound selected from the group consisting of silicon oxide, titanium oxide, magnesium oxide, and aluminum oxide.

[0105] [Article 12] the length of the dielectric layer in the first direction is not less than 10 nm and not more than 100 nm; The metasurface reflector of any one of clauses 1 to 11, wherein the length of the first metal layer in the first direction is 50 nm or more and 1000 nm or less.

[0106] [Article 13] A projection device mounted on a near-eye wearable device, A light source that emits laser light; a movable mirror for performing scanning with the laser light; A metasurface reflector according to any one of clauses 1 to 12, which reflects the laser light passing through the movable mirror to allow a user wearing the near-eye wearable device to view an image; A projection device comprising:

[0107] [Article 14] A projection device according to clause 13, A lens provided with the metasurface reflector; A near-eye trouble device comprising: [Explanation of symbols]

[0108] 1...Near eyewear error device, 3...Lens, 10...Projection device, 21...Light source unit (light source), 23...Movable mirror, 30...Metasurface reflector, 31...Unit area, 32...Reflective area, 31B...Unit area (third unit area), 31G...Unit area (second unit area), 31R...Unit area (first unit area), 32a...One end (first end), 32b...Other end (second end), 33...Missing area, 41...Metal layer (first metal layer), 42...Dielectric layer, 42a...Main surface, 43...Metal layer (second metal layer), 45...Metal unit.

Claims

1. A metasurface reflector, 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; Equipped with 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 along the main surface and a third direction along the main surface and intersecting the second direction, the second metal layer includes metal units provided in all or some of the unit areas, A metasurface reflector, wherein the lengths in the second direction of the metal units set for the same wavelength among the metal units arranged in the second direction are different from each other.

2. The metal unit is configured such that an amount of phase change of reflected light changes linearly from a first end to a second end in the second direction of a unit area in which the metal unit is provided, The metasurface reflector of claim 1 , wherein the length of the metal unit in the second direction is determined from the wavelength to be reflected and the angle of incidence and angle of reflection according to the position of the unit region in which the metal unit is provided.

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 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 equal to or greater than 10 nm and equal to or less than 100 nm, The length of the short side of the metal body is 10 nm or more and 200 nm or less, The metasurface reflector of claim 3 , wherein the length of the long side of the metal body is greater than the length of the short side and is 100 nm or more and 500 nm or less.

5. the plurality of unit areas include a reflective area in which the metal unit is provided and a missing area in which the metal unit is not provided, The metasurface reflector of claim 1 or 2, wherein in the arrangement in the third direction, the reflective regions and the missing regions are irregularly arranged.

6. The metasurface reflector of claim 5 , wherein in the arrangement in the second direction, the reflective regions and the missing regions are irregularly arranged.

7. The metasurface reflector of claim 5 , wherein the number of the missing regions is greater than or equal to 10% and less than or equal to 20% of the total number of unit regions included in the metasurface reflector.

8. the plurality of unit areas include a first unit area for a red component, a second unit area for a green component, and a third unit area for a blue component; the first unit area, the second unit area, and the third unit area are repeatedly arranged in that order in the second direction and the third direction; the lengths in the second direction of the metal units provided in the first unit regions arranged in the second direction are different from each other, The lengths in the second direction of the metal units provided in the second unit regions arranged in the second direction are different from each other, The metasurface reflector of claim 1 or 2, wherein the lengths in the second direction of the metal units provided in the third unit regions arranged in the second direction are different from each other.

9. The metasurface reflector of claim 1 or 2, wherein the second metal layer is composed of a metal including at least one element selected from the group consisting of silver, aluminum, copper, and gold.

10. The metasurface reflector of claim 1 or 2, wherein the dielectric layer is made of a material that is transparent in the visible light region.

11. The metasurface reflector of claim 10, wherein the dielectric layer is composed of a compound selected from the group consisting of silicon oxide, titanium oxide, magnesium oxide, and aluminum oxide.

12. the length of the dielectric layer in the first direction is not less than 10 nm and not more than 100 nm; The metasurface reflector of claim 1 or 2, wherein the length of the first metal layer in the first direction is 50 nm or more and 1000 nm or less.

13. A projection device mounted on a near-eye wearable device, A light source that emits laser light; a movable mirror for performing scanning with the laser light; 3. The metasurface reflector according to claim 1 or 2, which reflects the laser light passing through the movable mirror to allow a user wearing the near-eye wearable device to view an image; A projection device comprising:

14. A projection device according to claim 13; A lens provided with the metasurface reflector; A near-eye trouble device comprising:

Images