Wave surface control element, lighting device and projector

Abstract

Wavefront control element, lighting device, and projector. Reduces the effects of positional deviation of light sources in optical communication modules. The metalens (wavefront control element) of the present invention controls the wavefront of incident light and has multiple metasurface regions. These multiple metasurface regions are arranged in an array.

Description

Technical Field

[0001] The invention relates to a wavefront control element, a lighting device and a projector. Background Art

[0002] Metamaterials are composed of structures smaller than the wavelength and are artificial substances that exhibit magnetic permeability or behavior not found in nature with respect to electromagnetic waves, including light. The use of such metamaterials makes it possible to realize optical elements, such as those with negative refractive indices, that are difficult to achieve with conventional refractive or diffractive optical elements. Furthermore, as described above, metamaterials are composed of microstructures (structures) finer than the wavelength, resulting in small, thin, microresonator structures. Metamaterials are primarily classified into one-dimensional structures such as multilayer films composed of periodic structures, two-dimensional structures such as nanoantennas or metasurface elements, and three-dimensional structures such as fishnet structures. The higher the dimensionality of a metamaterial, the more controllable optical properties can be, but the manufacturing errors of the microstructures may increase, leading to greater deviations from the desired optical properties. Because the visible light used in image display devices has a shorter wavelength than microwaves or infrared light, metamaterials used in image display devices require higher-precision manufacturing technology than metamaterials used in devices using microwaves or infrared light. Therefore, in practice, metamaterials used in image display devices have a one-dimensional structure or a two-dimensional structure such as a metasurface element.

[0003] For example, Patent Document 1 discloses a metalens for imaging. A metalens is a type of metasurface. The height, width, and rotation angle of the metalens structure are determined based on the amount of phase shift of light controlled by the metalens. By varying the shape of the nanometer-scale structures along the surface of a substrate, a phase distribution that achieves lens function is formed, thereby realizing a metalens.

[0004] For example, Patent Document 2 discloses a metalens for projectors. Furthermore, Patent Document 3 discloses a metalens for fluorescent illumination systems. These metalenses exhibit desired optical functions for visible light in projectors or fluorescent illumination systems.

[0005] Patent Document 1: Japanese Patent Application No. 2019-516128

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-086765

[0007] Patent Document 3: Japanese Patent Application Publication No. 2018-537804.

[0008] In the design of the metalenses disclosed in Patent Documents 1 to 3, the phase modulation corresponding to parameters related to the shape of the microstructure is calculated, and the microstructure that will achieve the calculated desired phase modulation is arranged on the surface of the substrate. Since the actual dimensions of the designed phase modulation and the shape of the microstructure are smaller than the wavelength of light, electromagnetic wave analysis such as the Finite Difference Time Domain Method (FDTD) is used. However, as the surface area of the substrate increases, the computational load and calculation time for design evaluation of the actual dimensions and arrangement of the microstructure increase. In particular, when the metalenses disclosed in Patent Documents 2 and 3 are subjected to visible light, the substrate surface has a size of centimeters (cm), so evaluating the actual dimensions and arrangement of the microstructure requires a huge computational load and time. Therefore, research has been conducted to introduce machine learning to calculate the actual dimensions and arrangement of microstructures for design evaluation, but this has not yet reached practical use. Summary of the Invention

[0009] To address the aforementioned issues, one embodiment of the present invention is a wavefront control element that controls the wavefront of incident light and includes multiple metasurface regions. The multiple metasurface regions are arranged in an array and each has a lens function. Each of the multiple metasurface regions converges or diverges incident light. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic structural diagram of a projector including the wavefront control element according to the first embodiment.

[0011] Figure 2 It is a side view of the wavefront control element of the first embodiment.

[0012] Figure 3 yes Figure 1 The front view of the wave front control element is shown.

[0013] Figure 4 yes Figure 1 A cross-sectional view of the metasurface region of the wavefront control element is shown.

[0014] Figure 5 Is used to illustrate Figure 1 A perspective view of the design of the metasurface region of the wavefront control element is shown.

[0015] Figure 6 Is used to illustrate Figure 1 A perspective view of another metasurface region design of a wavefront control element is shown.

[0016] Figure 7Is used to illustrate Figure 1 A perspective view of another metasurface region design of a wave front control element is shown.

[0017] Figure 8 It is a side view of a wavefront control element according to a modified example of the first embodiment.

[0018] Figure 9 It is a side view of the wavefront control element of the second embodiment.

[0019] Figure 10 yes Figure 9 A cross-sectional view of the metasurface region of the wavefront control element is shown.

[0020] Figure 11 It is a side view of the wavefront control element of the third embodiment.

[0021] Figure 12 It is a side view of the wavefront control element of the fourth embodiment.

[0022] Figure 13 It is a side view of the wavefront control element of the fifth embodiment.

[0023] Figure 14 It is a side view of the wavefront control element of the sixth embodiment.

[0024] Figure 15 It is a side view of the wavefront control element of the seventh embodiment.

[0025] Figure 16 It is a side view of the wavefront control element of the eighth embodiment.

[0026] Description of labels

[0027] 111, 112, 113, 114, 115, 116, 117, 118 metalens (wavefront control element); 120 metasurface region; 121 metasurface region (first metasurface region); 122, 123 metasurface regions (second metasurface region); PF, PF1, PF2, PF3 focal positions. DETAILED DESCRIPTION

[0028] [First embodiment]

[0029] Below, use Figures 1 to 8 A first embodiment of the present invention will be described.

[0030] Figure 1 1 is a schematic structural diagram of a projector 1 including a wavefront control element according to the first embodiment. In the following figures, the scale of each component may be changed to facilitate viewing of each component.

[0031] (Projector)

[0032] like Figure 1 As shown, the projector 1 includes an illumination device 100, a color separation optical system 200, light modulation devices 400R, 400G, and 400B, a cross dichroic prism 500, and a projection optical system 600. The illumination device 100 emits white light WL including red light (R), green light (G), and blue light (B).

[0033] The illumination device 100 includes a light source device 2 , a converging optical system 30 , a rotating fluorescent plate 40 , a pickup optical system 60 , a first lens array 70 , a second lens array 80 , a polarization conversion element 92 , and a superimposing lens 94 .

[0034] The light source device 2 includes a light source unit 10 and a collimating optical system 20. The light source unit 10 includes a substrate 11 and a plurality of light-emitting elements 12. The substrate 11 has a quadrilateral shape, such as a roughly square or roughly rectangular shape, when viewed from above. The substrate 11 has a mounting surface for mounting the light-emitting elements 12, and the mounting surface is, for example, a flat surface. In addition, a heat dissipation component such as a heat sink may be provided on the surface opposite to the mounting surface of the substrate 11. The substrate 11 is formed of a material with high heat dissipation properties, such as a metal material.

[0035] The plurality of light emitting elements 12 are arranged in an array on the mounting surface of the substrate 11. Figure 1 In the illustrated structure, four rows of light-emitting elements 12 are arranged along a direction parallel to the mounting surface of substrate 11, and four rows are arranged along a direction perpendicular to the direction. Light-emitting elements 12 are mounted on the mounting surface of substrate 11 via a supporting member (not shown). Light-emitting elements 12 are laser light sources and have an emission surface for emitting laser light. Light emitted by light-emitting elements 12 is, for example, blue light with a wavelength of 445 nm.

[0036] Each light beam emitted from the light source unit 10 enters the collimating optical system 20. The collimating optical system 20 includes a plurality of collimating lenses 21. The collimating lenses 21 correspond to the light emitting elements 12 in a one-to-one manner. Therefore, the light beam emitted from each light emitting element 12 is converted into parallel light by the corresponding collimating lens 21.

[0037] The light source device 2 emits a plurality of parallelized lights toward the converging optical system 30. Hereinafter, the plurality of lights emitted from the light source device 2 will be collectively referred to as a light beam LB.

[0038] The converging optical system 30 includes a meta-lens (wavefront control element) 111. The converging optical system 30 is positioned in the optical path from the light source device 2 to the rotating phosphor plate 40, and causes the light beam LB to be incident on the phosphor layer 42 of the rotating phosphor plate 40 in a substantially converging state as excitation light. The detailed structure of the meta-lens 111 will be described later.

[0039] The rotating fluorescent plate 40 includes a fluorescent layer 42 and a dichroic film 43. The fluorescent layer 42 is disposed on a circular plate 41, which is rotatable about the optical axis of the light beam LB by a motor 50, and is arranged along the circumference of the circular plate 41. The circular plate 41 is formed from a material that transmits blue light. Examples of materials for the circular plate 41 include quartz glass, quartz, sapphire, optical glass, and transparent resin.

[0040] As described above, the light beam LB emitted from the light source device 2 enters the phosphor layer 42 from the circular plate 41 side in the direction along the optical axis. The phosphor layer 42 is excited by the light beam LB. The phosphor layer 42 converts a portion of the light beam LB from the light source device 2 into fluorescent light and allows the remaining portion of the light beam LB to pass through without conversion. The phosphor layer 42 is made of, for example, (Y, Gd) 3 (Al, Ga) 5 O containing a YAG-based phosphor. 12 :Layer composition of Ce.

[0041] The dichroic film 43 is disposed between the phosphor layer 42 and the circular plate 41. It transmits the blue laser beam LB and reflects the fluorescence. The rotating phosphor plate 40 thus combines a portion of the blue laser beam LB that has passed through the phosphor layer 42 with the fluorescence emitted from the phosphor layer 42, emitting white light WL toward the pickup optical system 60.

[0042] The pickup optical system 60 includes a lens 201, and substantially collimates the white light WL emitted from the rotating fluorescent plate 40. The lens 201 is formed of, for example, a convex lens, but may be formed of a lens optical system including a plurality of convex lenses.

[0043] The white light WL collimated by the pickup optical system 60 is incident on the first lens array 70. The first lens array 70 has a plurality of small lenses 71 for dividing the light from the pickup optical system 60 into a plurality of partial light beams. The plurality of small lenses 71 are arranged in a matrix in a plane perpendicular to the illumination optical axis 100ax of the illumination device 100. The second lens array 80 has a plurality of small lenses 81 corresponding to the plurality of small lenses 71 of the first lens array 70. The second lens array 80, together with the overlapping lens 94, forms images of the respective small lenses 71 of the first lens array 70 near the image formation areas of the respective light modulating devices 400R, 400G, and 400B. The plurality of small lenses 81 are arranged in a matrix in a plane perpendicular to the illumination optical axis 100ax.

[0044] The polarization conversion element 92 converts each of the partial light beams split by the first lens array 70 into linearly polarized light. The polarization conversion element 92 comprises a polarization separation layer, a reflective layer, and a phase shift plate. The polarization separation layer of the polarization conversion element 92 transmits one linearly polarized component of the polarization components contained in the white light WL emitted from the lighting device 100 and reflects the other linearly polarized component in a direction perpendicular to the illumination optical axis 100ax. The reflective layer of the polarization conversion element 92 reflects the other linearly polarized component reflected by the polarization separation layer in a direction parallel to the illumination optical axis 100ax. The phase shift plate of the polarization conversion element 92 converts the other linearly polarized component reflected by the reflective layer into one linearly polarized component.

[0045] The superimposing lens 94 converges the partial light beams from the polarization conversion element 92 and superimposes them near the image formation areas of the light modulators 400R, 400G, and 400B. The first lens array 70, the second lens array 80, and the superimposing lens 94 form an integrating optical system that uniformizes the in-plane light intensity distribution of the white light WL from the illumination device 100 in the image formation areas.

[0046] The color separation optical system 200 includes dichroic mirrors 210 and 220, reflecting mirrors 230, 240, and 250, and relay lenses 260 and 270. The color separation optical system 200 separates the white light WL emitted from the illumination device 100 into red light R, green light G, and blue light B, and guides the red light R, green light G, and blue light B to the corresponding light modulators 400R, 400G, and 400B. Field lenses 300R, 300G, and 300B are arranged between the color separation optical system 200 and the light modulators 400R, 400G, and 400B.

[0047] The dichroic mirror 210 transmits the red light component and reflects the green and blue light components. The dichroic mirror 220 reflects the green light component and transmits the blue light component. The reflector 230 reflects the red light component. The reflectors 240 and 250 reflect the blue light component.

[0048] The light modulators 400R, 400G, and 400B each comprise a liquid crystal panel that modulates incident light of various colors according to image information to form an image. The operating mode of the liquid crystal panel can be any of the following: TN mode, VA mode, or transverse electric field mode, and is not limited to a specific mode. The light modulators 400R, 400G, and 400B each include an incident-side polarizing plate (not shown) disposed on the light incident side and an exit-side polarizing plate (not shown) disposed on the light exit side.

[0049] Cross dichroic prism 500 combines the image lights emitted from the light modulators 400R, 400G, and 400B to form a color image. Cross dichroic prism 500 is constructed by bonding four rectangular prisms together, and has a roughly square shape when viewed from above. In cross dichroic prism 500, a dielectric multilayer film is formed at the roughly X-shaped interface between the bonded rectangular prisms.

[0050] The color image emitted from the cross dichroic prism 500 is magnified and projected by the projection optical system 600 to form an image on the screen SCR.

[0051] (Wavefront Control Components)

[0052] Next, the metalens 111 used in the illumination device 100 of the projector 1 will be described. The metalens 111 of the first embodiment is a wavefront control element that controls the wavefront of the light beam (incident light) LB composed of blue light incident from the light source device 2. Specifically, the metalens 111 converts the substantially parallel wavefront of the light beam LB into a converging wavefront that converges toward a predetermined convergence point or region on the phosphor layer 42 of the rotating phosphor plate 40.

[0053] Hereinafter, the direction parallel to the optical axis AX of the light beam LB incident on the meta-lens 111 is referred to as the Z direction, the opposite side of the Z direction is referred to as the +Z side, and the opposite side of the Z direction is referred to as the -Z side. Furthermore, a direction perpendicular to the Z direction is referred to as the X direction, the opposite side of the X direction is referred to as the +X side, and the opposite side of the X direction is referred to as the -X side. Furthermore, a direction that exists within the same plane as the X direction and is perpendicular to both the X and Z directions is referred to as the Y direction, the opposite side of the Y direction is referred to as the +Y side, and the opposite side of the Y direction is referred to as the -Y side.

[0054] Figure 2 is a side view of the metalens 111. Figure 3 is the main view of the meta-lens 111. Figure 2 and Figure 3 As shown, the metalens 111 includes a plurality of metasurface regions 120. The plurality of metasurface regions 120 are arranged in an array on an XY plane including the X and Y directions. In other words, the metalens 111 includes a plurality of metasurface regions 120 arranged in a relative positional relationship with one another so that the metalens 111 can function as a single optical element as a whole, rather than having a plurality of metasurface regions arranged without any relation to one another.

[0055] The meta-lens 111 is formed by Figure 2 The metasurface regions 120 are arranged adjacent to each other in the X and Y directions as shown. Figure 2As shown, the meta-lens 111 is composed of four meta-surface regions 120 in the X direction and the Y direction, respectively. Figure 3 As shown, a total of 16 metasurface regions 120 are formed on the XY plane.

[0056] The metalens 111 is rectangular in a front view along the Z direction. Each metasurface region 120 is rectangular in a front view along the Z direction. If the size of the metalens 111 in the X and Y directions is defined as size S111, and the size of the metasurface region 120 in the X and Y directions is defined as size S120, then S111 = 4 × S120. Size S111 is on the order of centimeters (cm), while size S120 is on the order of micrometers (μm).

[0057] The plurality of metasurface regions 120 of the metalens 111 are classified into four types of metasurface regions 121, 122, and 123. Each of the metasurface regions 121 to 123 is a transmissive metasurface region and is composed of each of the transmissive metalenses 151 to 153. Figure 3 As shown, the metasurface region 121 is arranged in the four metasurface regions 120 on the center side on the XY plane of the metalens 111. The metasurface regions 122 and 123 are arranged in a total of 12 metasurface regions 120 surrounding the four metasurface regions 120 on the center side on the XY plane of the metalens 111.

[0058] like Figure 2 and Figure 3 As shown, the centers of the meta-lens 111 in the X and Y directions overlap with the optical axis AX. The focus (point) F of the meta-lens 111 is set at the +Z side of the surface of the meta-lens 111 at a distance of focal length f from the surface. Figure 1 The predetermined convergence point of the phosphor layer 42 of the rotating phosphor plate 40 in the illumination device 100 of the projector 1 described above is the same. That is, the meta-lens 111 converges the incident light beam LB at the focal point F inside the phosphor layer 42 .

[0059] In the metalens 111, the focal positions PF of the multiple metasurface regions 120 are identical. Specifically, the focal position PF1 of the metasurface region (first metasurface region) 121 is identical to the focal position PF2 of the metasurface region (second metasurface region) 122 and the focal position PF3 of the metasurface region (third metasurface region) 123. Therefore, for each type of metasurface region, the center and focal point F of the metalens 151 constituting the metasurface region 121 on the XY plane are located at different positions in the X and Y directions. As described above, the metalens 111 is specifically composed of 4×4 metasurface regions 120. On the XY plane, the center and focal point F of the metalens 111 overlap. Therefore, when viewed along the Z direction, the focal point F of the metalens 151 is located at one of the four corners of the region.

[0060] The centers and focal points F of the metalenses 152 and 153 that constitute the metasurface regions 122 and 123 on the XY plane are located at different positions in the X and Y directions. When viewed along the Z direction, the focal points F of metalenses 152 and 153 are located outside their respective regions. In other words, metalenses 151 to 153 are off-axis lenses. Furthermore, metalenses 152 and 153 have a greater off-axis amount than metalens 151. Furthermore, metalens 153 has a greater off-axis amount than metalens 152.

[0061] Figure 4 : This is a cross-sectional view of the metasurface region 120 cut parallel to the XY plane. The metasurface region 120 includes a flat substrate 102 and a plurality of structures 103. The surface 102a on the +Z side and the back surface 102b on the -Z side of the substrate 102 are parallel to the XY plane and extend in the XY plane. The dimensions of the substrate 102 in the X and Y directions are dimensions S120. The dimension of the substrate 102 in the Z direction is not particularly limited and is appropriately set according to the wavelength of the light beam LB or the optical performance required of the projector 1. In addition, the substrates 102 of the plurality of metasurface regions 120 may be formed integrally with each other, or may be formed separately and joined when arranged in the X and Y directions.

[0062] The plurality of structures 103 are arranged on the surface 102a of the substrate 102 at intervals d from each other. Each structure 103 has a width t (not shown) in the X direction, a width w in the Y direction, and a height h in the Z direction. Figure 4In the example, the widths w of the plurality of structures 103 are shown as being substantially the same, but the widths t and w of the plurality of structures 103 are independently designed based on the principles described below. That is, the widths t and w of the structures 103, 103 adjacent to each other on the XY plane may be the same or different. Figure 3 、 Figures 5 to 7 In each of the figures, multiple structures 103 are omitted.

[0063] The substrate 102 and the plurality of structures 103 are formed of a material having high transmittance for the wavelength band of the light beam LB. If the wavelength of the light beam LB is in the visible wavelength region, for example, 445 nm, examples of the materials of the substrate 102 and the plurality of structures 103 include optical glass, silicon oxide (SiO2), titanium oxide (TiO2), and the like.

[0064] Figure 5 1 is a perspective view for explaining the design of the metalens 151 constituting the metasurface region 121. Figure 5 As shown, the center 121C of the metalens 151 in the X and Y directions is spaced apart from the focal point F at focal position PF1 by a dimension S120×(1 / 2) in the X and Y directions, respectively, and by a focal length f in the Z direction. The widths t and w of the multiple structures 103 (not shown), the spacing d between adjacent structures 103 in the XY plane, and the extension direction of the structures 103 are designed based on the dimension S120, the focal length f, and the center wavelength (wavelength, peak wavelength) of the light beam LB. This allows the light beam LB incident on the metasurface region 121 to converge at the focal point F on the +Z side, spaced apart by the respective dimensions in the X, Y, and Z directions. The height h of the multiple structures 103 in the metasurface region 121 is set based on the center wavelength of the light beam LB and the required phase modulation amount of the metalens 151.

[0065] exist Figure 5 In the illustrated metasurface region 121 , when viewed along the Z direction, the focal point F overlaps with the corner on the −X side and the −Y side of the metasurface region 121 . Figure 5 The illustrated metasurface region 121 corresponds to Figure 3 The shapes and distribution of the multiple structures 103 in the three metasurface regions 121 other than the +X and +Y metasurface regions 121 are obtained by inverting or rotating the shapes and distribution of the multiple structures 103 in the +X and +Y metasurface regions 121 according to their relative arrangement with the +X and +Y metasurface regions 121.

[0066] For example, Figure 3 The shapes and distributions of the multiple structures 103 in the metasurface regions 121 on the +X and -Y sides of the four illustrated metasurface regions 121 are the shapes and distributions obtained by inverting the shapes and distributions of the multiple structures 103 in the metasurface regions 121 on the +X and +Y sides about a virtual axis parallel to the X direction and passing through the center 111C on the XY plane of the metalens 111. By taking into account the symmetry about the center 111C in this way, the shapes and distributions of the multiple structures 103 in each of the four metasurface regions 121 are of a single type.

[0067] Figure 6 1 is a perspective view for explaining the design of the metalens 152 constituting the metasurface region 122. Figure 6 As shown, the center 121C of the metalens 152 in the X and Y directions is spaced apart from the focal point F at focal position PF2 by a dimension S120×(3 / 2) in the X direction, a dimension S120×(1 / 2) in the Y direction, and a focal length f in the Z direction. The widths t and w of the multiple structures 103 (not shown), the spacing d between adjacent structures 103 in the XY plane, and the extension direction of the structures 103 are designed based on the dimension S120, the focal length f, and the center wavelength (wavelength, peak wavelength) of the light beam LB. This allows the light beam LB incident on the metasurface region 122 to converge at the focal point F on the +Z side, spaced apart by the respective dimensions in the X, Y, and Z directions. The height h of the multiple structures 103 in the metasurface region 122 is set based on the center wavelength of the light beam LB and the phase modulation amount required by the metalens 152.

[0068] exist Figure 6 In the illustrated metasurface region 122 , when viewed along the Z direction, the focal point F is located on the −X side and the −Y side of the metasurface region 122 . Figure 6 The illustrated metasurface region 122 corresponds to Figure 3 The metasurface region 122 closest to the +X and +Y sides among the eight metasurface regions 122 shown in the example. The shapes and distribution of the multiple structures 103 in the seven metasurface regions 122 other than the metasurface region 122 closest to the +X and +Y sides are obtained by inverting or rotating the shapes and distribution of the multiple structures 103 in the metasurface region 122 closest to the +X and +Y sides in accordance with the relative arrangement with the metasurface region 122 closest to the +X and +Y sides.

[0069] For example, Figure 3The shape and distribution of the multiple structures 103 in the metasurface region 122 closest to the +Y and +X sides of the eight metasurface regions 122 are the shapes and distributions of the multiple structures 103 in the metasurface region 122 closest to the +X and +Y sides, respectively, inverted about an imaginary axis passing through the center 111C of the metalens 111 and oriented at 45° to the +X side in the X direction and the +Y side in the Y direction. By taking into account the symmetry about the center 111C in this manner, the shape and distribution of the multiple structures 103 in each of the eight metasurface regions 122 are of a single type.

[0070] Figure 7 1 is a perspective view for explaining the design of the metalens 153 constituting the metasurface region 123. Figure 7 As shown, the center 121C of the meta-lens 153 in the X and Y directions and the focal point F at the focal position PF3 are separated by a dimension S120×(3 / 2) in the X and Y directions, respectively, and by a focal length f in the Z direction. The widths t and w of the multiple structures 103 (not shown), the spacing d between adjacent structures 103 in the XY plane, and the extension direction of the structures 103 are designed based on the dimension S120, the focal length f, and the center wavelength (wavelength, peak wavelength) of the light beam LB. This allows the light beam LB incident on the meta-surface region 123 to converge at the focal point F on the +Z side, separated by the respective dimensions in the X, Y, and Z directions. The height h of the multiple structures 103 in the meta-surface region 123 is set based on the center wavelength of the light beam LB and the required phase modulation amount of the meta-lens 153.

[0071] exist Figure 7 In the illustrated metasurface region 123 , when viewed along the Z direction, the focal point F is located on the −X side and the −Y side of the metasurface region 123 . Figure 7 The illustrated metasurface region 123 corresponds to Figure 3 The shapes and distribution of the multiple structures 103 in the +X and +Y metasurface regions 123 are obtained by inverting or rotating the shapes and distribution of the multiple structures 103 in the +X and +Y metasurface regions 123 according to the relative arrangement with the +X and +Y metasurface regions 123.

[0072] For example, Figure 3The shapes and distributions of the multiple structures 103 in the metasurface regions 123 on the -Y and -X sides of the eight illustrated metasurface regions 123 are the shapes and distributions of the multiple structures 103 in the metasurface regions 123 on the +X and +Y sides, rotated 180° in the XY plane with respect to the center 111C of the metalens 111. By taking into account the symmetry about the center 111C in this way, the shapes and distributions of the multiple structures 103 in each of the four metasurface regions 123 are of a single type.

[0073] The shapes and distribution of the multiple metasurface regions 120 of the metalens 111 are designed by calculating the shapes and distributions of the three types of metasurface regions 121 to 123. The shapes of the structures 103 in each of the three types of metasurface regions 121 to 123 and the distribution of the multiple structures 103 are designed by determining the ideal phase distribution of each metalens 151 to 153 based on the aforementioned positional relationship between the positions of the corresponding metalenses 151 to 153 and the focal point F, and determining the dimensions of the structures 103, such as the width t, w, and spacing d, corresponding to the ideal phase distribution. The determination of the dimensions of the structures 103 corresponding to the ideal phase distribution can be performed in the same manner as in conventional metalens design. For the design of the shapes and distributions of the three types of metasurface regions 121 to 123 using electromagnetic wave analysis, reference can be made to, for example, Patent Document 1 mentioned above. The design evaluation of the shapes and distributions of the three types of metasurface regions 121 to 123 is performed using electromagnetic wave analysis, such as the FDTD method. The structure 103 is a fine structure having a size smaller than the central wavelength of the light beam LB. Therefore, the difference between the dimensions associated with the designed structure 103 and the actual dimensions of the structure 103 of the manufactured metalens 111 has a significant impact on the optical function of the metalens 111. Therefore, design evaluation using electromagnetic wave analysis is essential for the practical application of the metalens 111.

[0074] The metalens 111 of the first embodiment described above is a wavefront control element for controlling the wavefront of the light beam LB and includes multiple metasurface regions 120. These multiple metasurface regions 120 are arranged in an array on the XY plane. In the metalens 111 of the first embodiment, by designing the shapes and distribution of the structures 103 in each of the three metasurface regions 121 to 123, the structures constituting the metasurface of the entire metalens 111 can be designed. The widths t, w, and heights h of the structures 103 in each of the multiple metasurface regions 120 of the metalens 111 are less than the central wavelength of the light beam LB. Therefore, electromagnetic wave analysis is required when designing the shapes and distribution of the structures 103. The size S111 of the metalens 111 used in the projector 1 and controlling the wavefront of the light beam LB composed of blue light is on the order of centimeters. Conventional methods such as FDTD (Fluidized Time Domain) are used to uniformly design the shapes of the structures 103 and the distribution of the multiple structures 103 throughout the metalens 111, resulting in a significant increase in computational load and time, making this impractical. On the other hand, the metalens 111 of the first embodiment designs the shapes of the structures 103 and the distribution of the multiple structures 103 for each of the metasurface regions 120, specifically the three metasurface regions 121 to 123, at the μm level. This allows the computational load and time associated with electromagnetic wave analysis using methods such as FDTD to be reduced to practical levels. The metalens 111 of the first embodiment, by arraying multiple metasurface regions 120, i.e., μm-level metalenses 151 to 153, enables the realization of a cm-level lens for the projector 1 without increasing the computational load during design evaluation. The metalens 111 of the first embodiment eliminates the need for excessive computational load and time for design evaluation of the actual size and arrangement of the structures 103.

[0075] In the metalens 111 of the first embodiment, the plurality of metasurface regions 120 include a metasurface region 121 and metasurface regions 122 and 123. The focal position PF1 of the metasurface region 121 and the focal positions PF2 and PF3 of the metasurface regions 122 and 123 are identical. The metalens 111 converges the incident light beam LB at a focal point F on the +Z side, opposite to the incident side, along the Z direction of the optical axis AX of the incident light beam LB. Specifically, the metasurface regions 121 to 123 converge the light beam LB at the same, common focal point F. The metalens 111 of the first embodiment achieves a centimeter-level off-axis converging lens with a computational load and time for electromagnetic wave analysis that are practically low.

[0076] In the metalens 111 of the first embodiment, each of the plurality of metasurface regions 120 is a transmissive metasurface. The metalens 111 of the first embodiment can realize a transmissive converging lens with a practically low computational load and computational time for electromagnetic wave analysis.

[0077] In addition, regarding the metalens 111 of the first embodiment, as the plurality of metasurface regions 120 constituting the metalens 111, Figure 2 and Figure 3 As shown, a total of 16 metasurface regions 120 arranged in a 4×4 pattern on the XY plane are illustrated. However, the number of metasurface regions 120 included in the metalens 111 is not limited to 16. In order to perform design evaluation using electromagnetic wave analysis such as FDTD, it is preferable to set the size S120 of the plurality of metasurface regions 120 to an appropriate and practical size. If the size S111 of the metalens 111 is constant, the number of metasurface region 120 arrays increases as the size S120 of the metasurface region 120 decreases. In the metalens 111, if the number of metasurface region 120 arrays increases, the number of types of shapes and distributions of the plurality of structures 103 in the metasurface region 120 increases, and the number of calculations and the computational load of the electromagnetic wave analysis during the design evaluation increases rapidly. However, by arranging two or more of the multiple metasurface regions 120 at positions symmetrical to each other with respect to the center 111C of the metalens 111, the number of types of shapes and distributions of the multiple structures 103 in the metasurface region 120 can be suppressed, and the number of calculations and the computational load of the electromagnetic wave analysis during design evaluation can be suppressed to a practical level.

[0078] In the metalens 111 of the first embodiment, when viewed from the Z direction parallel to the light beam LB, the plurality of metasurface regions 120 are arranged symmetrically with respect to the center 111C of the metalens 111. Specifically, Figure 3As shown, the four metasurface regions 121 are symmetrical with each other about the X-direction or Y-direction passing through the center 111C, or are arranged in rotational symmetry about the center 111C. Furthermore, the eight metasurface regions 122 are symmetrical with each other about the X-direction or Y-direction passing through the center 111C, or are arranged in rotational symmetry about the center 111C. Furthermore, the metasurface region 123 is symmetrical with each other about the X-direction or Y-direction passing through the center 111C, or are arranged in rotational symmetry about the center 111C. Thus, the design and evaluation of the shapes of the structures 103 and the distribution of the multiple structures 103 in the metasurface regions 120 of the metalens 111, which has an array number of 16, can be performed by designing and evaluating the shapes of the structures 103 and the distribution of the multiple structures 103 in each of the metasurface regions 121 to 123, that is, the shapes of the structures 103 and the distribution of the multiple structures 103 in the three types of structures 103 and the distribution of the multiple structures 103. That is, by making the relative arrangement of the metasurface regions 121 to 123 symmetrical, the calculation time and computational load for design evaluation of a metalens 111 having an array of 16 can be reduced to approximately (3 / 16) of the calculation time and computational load for 16 types of metasurface regions 120.

[0079] Figure 8 FIG. 1 is a side view of a metalens 112 which is a modified example of the metalens 111 of the first embodiment. Figure 2 In FIG, the focus F is shown as a point. That is, the size S120 of the metasurface region 120 of the metalens 111 is larger than the size of the focus F to the extent that the focus F can be regarded as a point. However, as Figure 8 As shown, the size S120 of the metasurface region 120 of the metalens 112 may also be equal to the size SF of the focus F in the X and Y directions. In the metalens 112, each metasurface region 121 to 123 is composed of a transmission type metagrating 154 to 156. Figure 8 In FIG. 1 , the metasurface region 122 and the metagrating 155 do not appear. Each of the metagratings 154 to 156 deflects the incident light beam LB as parallel light toward the focal point F.

[0080] In the metalens 112 of the modified example of the first embodiment, similarly to the metalens 111 of the first embodiment, it is preferable to set the size S120 of the plurality of metasurface regions 120 to an appropriate and practical size for design evaluation using electromagnetic wave analysis such as FDTD. Furthermore, it is preferable to reduce the number of possible shapes of the structures 103 in the metasurface region 120 and the number of possible distributions of the plurality of structures 103 by making the relative arrangement of the metasurface regions 121 to 123 symmetrical.

[0081] The lighting device 100 of the first embodiment includes a metalens 111 as the converging optical system 30. According to the lighting device 100 of the first embodiment, by using the metalens 111, which appropriately reduces the computational load and computation time / number of computations required for electromagnetic wave analysis during design evaluation to practical levels as described above, an ultrathin converging optical system 30 can be realized. According to the lighting device 100 of the first embodiment, the entire device can be miniaturized and thinned.

[0082] The projector 1 of the first embodiment includes the aforementioned metalens 111. According to the projector 1 of the first embodiment, various optical elements having a size in the cm range, such as the metalens 111 used in the lighting device 100, are arrayed according to the metasurface region 120 in the μm range. This allows the projector 1 to include various optical elements that are thinner than before, thereby achieving overall miniaturization and thinning without the computational load and computational time / number of calculations required for electromagnetic wave analysis during design evaluation.

[0083] Furthermore, in the projector 1 of the first embodiment, in addition to the converging optical system 30, the lens 201 of the pickup optical system 60 may also be configured as a metalens formed by an array of multiple metasurface regions 120, similarly to the metalens 111. Furthermore, in the projector 1 of the first embodiment, at least one of the relay lenses 260 and 270 of the color separation optical system 200 may also be configured as a metalens formed by an array of multiple metasurface regions 120, similarly to the metalens 111. Furthermore, in the projector 1 of the first embodiment, at least one of the multiple lenslets 71 of the first lens array 70 and the multiple lenslets 81 of the second lens array 80 may also be configured as a metalens formed by an array of multiple metasurface regions 120, similarly to the metalens 111.

[0084] [Second embodiment]

[0085] Next, use Figure 9 and Figure 10 A second embodiment of the present invention will be described.

[0086] Figure 9 This is a side view of a metalens (wavefront control element) 113 according to the second embodiment. In the wavefront control elements of the second and subsequent embodiments below, components common to those of the wavefront control elements of higher-level embodiments are denoted by the same reference numerals, and their descriptions are omitted. The wavefront control elements of the second and subsequent embodiments will be primarily described, with only those components that differ from those of the higher-level embodiments.

[0087] like Figure 9As shown, the metalens 113 has the same structure as the metalens 111, except that the transmissive metasurface regions 121 to 123 are replaced by reflective metalenses 157 to 159 constituting reflective metasurface regions 124 to 126. Figure 9 In the figure, the metasurface region 125 and the metalens 158 are not shown. A half mirror 186 is arranged near the front side of the metalens 113 in the direction of travel of the light beam LB incident on the metalens 113. In the second embodiment, the light beam LB emitted from the light source device 2 of the projector 1 is incident on the half mirror 186 and reflected toward the surface 113a on the +Z side of the metalens 113. The light beam LB incident on the metalens 113 from the surface 113a, i.e., from the +Z side, is reflected by the plurality of metasurface regions 124 to 126, passes through the half mirror 186, and converges in the Z direction to a focal point F on the +Z side (same side) as the incident side.

[0088] Figure 10 This is a cross-sectional view of the metasurface region 120 of the metalens 113, taken parallel to the XY plane. In the metasurface region 120 of the metalens 113, a reflective layer 105 made of a metal such as aluminum (Al) is provided within the substrate 102 in the Z direction. The shape of the structures 103 and the distribution of the plurality of structures 103 in the metasurface region (first metasurface region) 124 are designed similarly to the shape of the structures 103 and the distribution of the plurality of structures 103 in the metasurface region 121. The shape of the structures 103 and the distribution of the plurality of structures 103 in the metasurface regions (second metasurface regions) 125 and 126 are designed similarly to the shape of the structures 103 and the distribution of the plurality of structures 103 in the metasurface regions 122 and 123. However, since each of the metasurface regions 124 to 126 is reflective, the height h of the structure 103 of each of the metasurface regions 124 to 126 is approximately (1 / 2) the height h of the structure 103 of each of the transmissive metasurface regions 121 to 123 .

[0089] Regarding the common structure with the metalens 111 of the first embodiment, the metalens 113 of the second embodiment described above achieves the same functions and effects as the metalens 111 of the first embodiment. Furthermore, the lighting device 100 including the metalens 113 of the second embodiment and the projector 1 including the lighting device 100 achieve the same functions and effects as the lighting device 100 and the projector 1 described in the first embodiment.

[0090] In the metalens 113 of the second embodiment, each of the multiple metasurface regions 120 is a reflective metasurface. The metalens 113 of the second embodiment achieves a reflective converging lens that reduces the computational load and time required for electromagnetic wave analysis to practical levels. Furthermore, the metalens 113 of the second embodiment shares a common optical path in the Z direction between a portion of the light beam LB incident on the metalens 113 and a portion of the light beam LB emitted from the metalens 113. This allows for a more compact illumination device 100 and projector 1 equipped with the metalens 113, compared to the illumination device 100 and projector 1 of the first embodiment.

[0091] In reference Figure 1 In the projector 1 described above, the reflector 250 and relay lens 270 corresponding to blue light B may be integrated. Furthermore, the dichroic mirror 220 and relay lens 260 corresponding to green light G may also be integrated. In the projector 1 of the second embodiment, these integrated reflectors and relay lenses may be formed from a metalens or wavefront control element arrayed with multiple metasurface regions 120, similar to the metalens 113. This allows for further miniaturization of the illumination device 100 and projector 1 equipped with the metalens 113.

[0092] [Third embodiment]

[0093] Next, use Figure 11 A third embodiment of the present invention will be described.

[0094] Figure 11 : is a side view of the meta-lens (wavefront control element) 114 of the third embodiment. Figure 11 As shown, the metalens 114 has the same structure as the metalens 111 except that the metasurface regions 121 to 123 are replaced by the transmissive metalens 161 constituting the transmissive metasurface region 127. Figure 1 In the converging optical system 30 of the projector 1 shown, the metalens 114 is applied to at least one of the first lens array 70 and the second lens array 80. The metalens 161 of the metasurface regions 120, i.e., the metasurface regions 127, of the metalens 114 correspond to at least one of the lenslets 71 of the first lens array 70 and the lenslets 81 of the second lens array 80.

[0095] The center 127C and focal point F of the metalens 161 in the X and Y directions overlap in the X and Y directions and are separated by a focal length f in the Z direction. The widths t and w of the multiple structures 103 (not shown), the spacing d between adjacent structures 103 in the XY plane, and the extension direction of the structures 103 are designed based on the dimension S120, the focal length f, and the center wavelength (wavelength, peak wavelength) of the light beam LB. This allows the light beam LB incident on the metasurface region 127 to converge at the focal point F on the +Z side, separated by the respective dimensions in the X, Y, and Z directions, as described above. The height h of the multiple structures 103 in the metasurface region 127 is set based on the center wavelength of the light beam LB and the required phase modulation amount of the metalens 161.

[0096] In the metalens 114, the focal points PF of the multiple metasurface regions 120 are mutually different in the XY plane. Specifically, in the metalens 114, there are the same number of focal points (multiple points) F as there are metasurface regions 120 and 127. Furthermore, in the metalens 114, the relative positions of the focal points F with respect to each of the multiple metasurface regions 127 are the same for each of the multiple metasurface regions 127. Therefore, the shapes and distributions of the multiple metasurface regions 120 in the multiple metalenses 114 are designed by calculating the shape and distribution of only one type of metasurface region 127.

[0097] Regarding the common structure with the metalens 111 of the first embodiment, the metalens 114 of the third embodiment described above achieves the same functions and effects as the metalens 111 of the first embodiment. Furthermore, the lighting device 100 including the metalens 114 of the third embodiment and the projector 1 including the lighting device 100 achieve the same functions and effects as the lighting device 100 and the projector 1 described in the first embodiment.

[0098] In the metalens 114 of the third embodiment, each of the multiple metasurface regions 120 includes a metasurface region 127. The focal positions of the multiple metasurface regions 127 differ from one another in the XY plane. Specifically, the multiple metasurface regions 127 converge the light beam LB at respective focal points F. That is, the metalens 114 converges the light beam LB at a number of focal points F equal to the number of metasurface regions 120, on the +Z side, opposite to the incident side, along the Z direction of the optical axis AX of the incident light beam LB. The metalens 114 of the third embodiment achieves a centimeter-level on-axis converging lens with a computational load and computational time for electromagnetic wave analysis that are practically low. Furthermore, the metalens 114 of the third embodiment enables a thinner lens array to be constructed using the metasurface regions 120 having nanometer-level structures 13.

[0099] Although not shown, as a modification of the metalens 114 of the third embodiment, the plurality of metasurface regions 120 of the metalens 114 may also include a first metasurface region and a second metasurface region, similar to the metalens 111 of the first embodiment. In this case, the focal position of the first metasurface region and the focal position of the second metasurface region may be different from each other.

[0100] [Fourth embodiment]

[0101] Next, use Figure 12 A fourth embodiment of the present invention will be described.

[0102] Figure 12 : is a side view of the meta-lens (wavefront control element) 115 of the fourth embodiment. Figure 12 As shown, the metalens 115 has the same structure as the metalens 114 except that the transmissive metasurface region 127 is replaced by a reflective metalens 162 constituting a reflective metasurface region 128. Figure 1 In the projector 1 described above, the reflective mirror 250 and relay lens 270 corresponding to blue light B may be integrated. Alternatively, the dichroic mirror 220 and relay lens 260 corresponding to green light G may be integrated. As described above, the metalens 115 is applied to the reflective mirror and relay lens integrated with each other in the projector 1.

[0103] A half mirror 186 is disposed on the near side of the metalens 115 in the direction of travel of the light beam LB incident on the metalens 115. In the fourth embodiment, the light beam LB emitted from the light source device 2 of the projector 1 is incident on the half mirror 186 and reflected toward the surface 115a on the +Z side of the metalens 115. The light beam LB incident on the metalens 115 from the surface 115a, i.e., from the +Z side, is reflected by the plurality of metasurface regions 128, passes through the half mirror 186, and converges in the Z direction to a focal point F on the +Z side (same side) as the incident side.

[0104] Although not shown, a reflective layer 105 made of a metal such as Al is provided inside the substrate 102 in the Z direction in the metasurface region 120 of the metalens 115. The shape of the structures 103 in the metasurface region 128 and the distribution of the plurality of structures 103 are designed similarly to the shape of the structures 103 in the metasurface region 127 and the distribution of the plurality of structures 103. However, since the metasurface region 128 is reflective, the height h of the structures 103 in the metasurface region 128 is approximately (1 / 2) the height h of the structures 103 in the transmissive metasurface region 127.

[0105] The metalens 115 of the fourth embodiment described above, having the same structure as the metalens 114 of the third embodiment, exhibits the same functions and effects as the metalens 114 of the third embodiment. Furthermore, the lighting device 100 including the metalens 115 of the fourth embodiment and the projector 1 including the lighting device 100 exhibit the same functions and effects as the lighting device 100 and the projector 1 described in the first embodiment.

[0106] In the metalens 115 of the fourth embodiment, each of the multiple metasurface regions 120 is a reflective metasurface. The metalens 115 of the fourth embodiment enables a reflective lens array with a computational load and time for electromagnetic wave analysis that are practically low. Furthermore, the metalens 115 of the fourth embodiment allows a portion of the light beam LB incident on the metalens 115 and a portion of the light beam LB emitted from the metalens 115 to share a common optical path in the Z direction. This allows for a more compact illumination device 100 and projector 1 equipped with the metalens 115, compared to the illumination device 100 and projector 1 of the third embodiment.

[0107] [Fifth embodiment]

[0108] Next, use Figure 13 A fifth embodiment of the present invention will be described.

[0109] Figure 13 : is a side view of the meta-lens (wavefront control element) 116 of the fifth embodiment. Figure 13 As shown, the metalens 116 has the same structure as the metalens 111 except that the metasurface regions 121 to 123 are replaced by transmissive metalenses 163 to 165 constituting transmissive metasurface regions 131 to 133. Figure 13 In Figure 1, the metasurface region 132 and the metalens 164 are not shown. Figure 1 In the projector 1 shown, the meta-lens 116 is used as a diffusion element (not shown) arranged to appropriately diffuse the light beam LB consisting of blue light.

[0110] Each metalens 163-165 has a negative focal length and divergence function (not shown). The focal points (not shown) of each metalens 163-165 are identical and located on the -Z side of the back surface 116b on the side where the light beam LB enters the metalens 116. The X and Y centers 163C of the metalens 163 are spaced from the focal point F (not shown) by a distance of S120×(1 / 2) in the X and Y directions, respectively, and by a focal length of -f in the Z direction. The X and Y centers 164C of the metalens 164 are spaced from the focal point F by a distance of S120×(3 / 2) in the X direction, S120×(1 / 2) in the Y direction, and by a focal length of -f in the Z direction. The X and Y centers 165C of the metalens 165 are spaced from the focal point F by a distance of S120×(3 / 2) in the X and Y directions, respectively, and by a focal length of -f in the Z direction. The widths t and w of the multiple structures 103 (not shown) in each of the metasurface regions 131 to 133, the spacing d between adjacent structures 103 in the XY plane, and the extension direction of the structures 103 are designed based on the size S120, the focal length f, and the center wavelength (wavelength, peak wavelength) of the light beam LB, so that the light beam LB incident on each metasurface region 131 to 133 diverges toward the +Z side from the focus F on the -Z side of the respective sizes in the X direction, the Y direction, and the Z direction, as described above.

[0111] Regarding the common structure with the metalens 111 of the first embodiment, the metalens 116 of the fifth embodiment described above achieves the same functions and effects as the metalens 111 of the first embodiment. Furthermore, the lighting device 100 including the metalens 116 of the fifth embodiment and the projector 1 including the lighting device 100 achieve the same functions and effects as the lighting device 100 and the projector 1 described in the first embodiment.

[0112] In the metalens 116 of the fifth embodiment, the focal positions of the metasurface region (first metasurface region) 131 and the metasurface regions (second metasurface regions) 132 and 133 are identical, but located closer to the -Z side of the metalens 116. Therefore, the metasurface regions 131-133 diverge the incident light beam LB toward the +Z side, assuming the same common focal point F. That is, the metalens 116 diverges the light beam LB toward the +Z side, opposite to the incident side, along the Z direction along the optical axis AX of the incident light beam LB. The metalens 116 of the fifth embodiment achieves a centimeter-level off-axis diverging lens that reduces the computational load and computational time for electromagnetic wave analysis to practically low levels.

[0113] [Sixth embodiment]

[0114] Next, use Figure 14 A sixth embodiment of the present invention will be described.

[0115] Figure 14 : is a side view of the meta-lens (wavefront control element) 117 of the sixth embodiment. Figure 14 As shown, the metalens 117 has the same structure as the metalens 116 except that the transmissive metasurface regions 131 to 133 are replaced by reflective metalenses 166 to 168 constituting reflective metasurface regions 134 to 136. Figure 14 In the figure, the metasurface region 135 and the metalens 167 are not present. The metalens 117 is Figure 1 In the projector 1 shown, a diffusion element (not shown) is provided to appropriately diffuse the light beam LB composed of blue light.

[0116] A half mirror 186 is disposed near the front of each meta-lens 166-168 in the direction of travel of the light beam LB incident on each meta-lens 166-168. In the sixth embodiment, in the projector 1, the light beam LB consisting of blue light to be diffused is incident on the half mirror 186 and reflected toward the +Z-side surface 117a of the meta-lens 117. The light beam LB incident on the meta-lens 117 from the surface 117a, i.e., from the +Z side, passes through the plurality of metasurface regions 134-136, exits toward the +Z side, passes through the half mirror 186, and then diverges in the Z direction toward the same +Z side (the same side) as the incident side. As a result, the light beam LB emitted from the meta-lens 117 toward the +Z side is diffused at least with respect to the optical axis AX.

[0117] Although not shown, a reflective layer 105 made of a metal such as Al is provided within the substrate 102 in the Z direction in the metasurface region 120 of the metalens 117. The shape of the structures 103 in each of the metasurface regions 134 to 136 and the distribution of the multiple structures 103 are designed similarly to the shape of the structures 103 in each of the metasurface regions 131 to 133 and the distribution of the multiple structures 103. However, since each of the metasurface regions 134 to 136 is reflective, the height h of the structures 103 in each of the metasurface regions 134 to 136 is approximately (1 / 2) the height h of the structures 103 in each of the transmissive metasurface regions 131 to 133.

[0118] Regarding the common structure with the metalens 116 of the fifth embodiment, the metalens 117 of the sixth embodiment described above achieves the same functions and effects as the metalens 116 of the fifth embodiment. Furthermore, the lighting device 100 including the metalens 117 of the sixth embodiment and the projector 1 including the lighting device 100 achieve the same functions and effects as the lighting device 100 and the projector 1 described in the first embodiment.

[0119] In the metalens 117 of the sixth embodiment, each of the multiple metasurface regions 120 is a reflective metasurface. The metalens 117 of the sixth embodiment achieves a reflective diverging lens that reduces the computational load and time required for electromagnetic wave analysis to practical levels. Furthermore, the metalens 117 of the sixth embodiment shares a common optical path in the Z direction between a portion of the light beam LB incident on the metalens 117 and a portion of the light beam LB emitted from the metalens 117. This allows for a more compact illumination device 100 and projector 1 equipped with the metalens 117, compared to the illumination device 100 and projector 1 of the fifth embodiment.

[0120] [Seventh embodiment]

[0121] Next, use Figure 15 A seventh embodiment of the present invention will be described.

[0122] Figure 15 : is a side view of the meta-lens (wavefront control element) 118 of the seventh embodiment. Figure 3 It can be seen that the meta-lens 118 has 16 meta-surface regions 120 on the XY plane. In the meta-lens 118, the 16 meta-surface regions 120 are composed of 16 types of meta-surface regions 141A to 141P. The 16 types of meta-surface regions 141A to 141P are composed of 16 types of meta-lenses 171A to 171P. The focal points F (omitted from the figure) of the 16 types of meta-surface regions 141A to 141P and the meta-lenses 171A to 171P are different from each other in the XY plane and in the Z direction and are randomly arranged. Figure 1 In the projector 1 shown, a diffusion element (not shown) is provided to appropriately diffuse the light beam LB composed of blue light.

[0123] exist Figure 15, metasurface regions 141A, 141E, 141I, and 141M are exemplified as the four metasurface regions 120 closest to the -Y side among the 16 types of metasurface regions 141A to 141P. The focus F (not shown) of metasurface region 141A exists at least on the +X side in the X direction and the +Z side in the Z direction relative to metasurface region 141A. The focus F (not shown) of metasurface region 141E exists at two points in the X direction, one located at least on the +X side in the X direction and the +Z side in the Z direction relative to metasurface region 141E. The focus F (not shown) of metasurface region 141I exists at least on the +X side in the X direction and the +Z side in the Z direction relative to metasurface region 141I. The focus F (not shown) of metasurface region 141M exists at least on the +X side in the X direction and the -Z side in the Z direction relative to metasurface region 141M. The meta-lens 118 as a whole diffuses (diversifies) the incident light beam LB on the +Z side, which is the opposite side to the incident side, in the Z direction along the optical axis AX of the incident light beam LB.

[0124] The widths t and w of the multiple structures 103 (not shown), the spacing d between adjacent structures 103 in the XY plane, and the extension direction of the structures 103 of each of the metasurface regions 141A to 141P are designed based on the size S120, the focal length f or the focal length -f, and the center wavelength (wavelength, peak wavelength) of the light beam LB, so that the light beam LB incident on each of the metasurface regions 141A to 141P converges to a focal point F on the +Z side of the respective size in the X direction, the Y direction, and the Z direction, or diverges toward the +Z side.

[0125] Regarding the common structure with the metalens 116 of the fifth embodiment, the metalens 118 of the seventh embodiment described above achieves the same functions and effects as the metalens 116 of the fifth embodiment. Furthermore, the lighting device 100 including the metalens 118 of the seventh embodiment and the projector 1 including the lighting device 100 achieve the same functions and effects as the lighting device 100 and the projector 1 described in the first embodiment.

[0126] In the metalens 118 of the seventh embodiment, the focal points F (not shown) of the 16 metasurface regions 141A-141P and the metalenses 171A-171P are randomly arranged in the XY plane and in the Z direction. The metalens 118 of the seventh embodiment can improve the divergence of the incident light beam LB compared to the metalens 116 of the fifth embodiment.

[0127] [Eighth embodiment]

[0128] Next, use Figure 16 An eighth embodiment of the present invention will be described.

[0129] Figure 16 : is a side view of the meta-lens (wavefront control element) 119 of the eighth embodiment. Figure 16 As shown, the metalens 119 has the same structure as the metalens 118 except that the transmissive metasurface regions 141A to 141P are replaced by reflective metalenses 172A to 172P constituting reflective metasurface regions 142A to 142P. Figure 16 In FIG, only the metasurface regions 142A, 142E, 142I, and 142M and the metalenses 172A, 172E, 172I, and 172M among the metasurface regions 142A to 142P and the metalenses 172A to 172P are illustrated. Figure 1 In the projector 1 shown, the meta-lens 119 is used as a diffusion element (not shown) arranged to appropriately diffuse the light beam LB consisting of blue light.

[0130] A half mirror 186 is disposed near the front of each meta-lens 172A-172P in the direction of travel of the light beam LB incident on each meta-lens 172A-172P. In the eighth embodiment, in the projector 1, the light beam LB consisting of blue light to be diffused is incident on the half mirror 186 and reflected toward the +Z-side surface 119a of the meta-lens 119. The light beam LB incident on the meta-lens 119 from the surface 119a, i.e., from the +Z side, passes through the plurality of metasurface regions 142A-142P and is emitted toward the +Z side. After passing through the half mirror 186, the light beam LB is converged in the Z direction to the +Z side, the same side as the incident side, or is diverged toward the +Z side. As a result, the light beam LB emitted from the meta-lens 118 to the +Z side (the same side as the incident side) is diffused (diverged) at least with respect to the optical axis AX.

[0131] Although not shown, in the metasurface region 120 of the metalens 119, a reflective layer 105 made of a metal such as Al is provided within the substrate 102 in the Z direction. The shape of the structures 103 and the distribution of the multiple structures 103 in each of the metasurface regions 142A to 142P are designed similarly to the shape of the structures 103 and the distribution of the multiple structures 103 in each of the metasurface regions 141A to 141P. However, since each of the metasurface regions 142A to 142P is reflective, the height h of the structures 103 in each of the metasurface regions 142A to 142P is approximately (1 / 2) the height h of the structures 103 in each of the transmissive metasurface regions 141A to 141P.

[0132] Regarding the common structure with the metalens 118 of the seventh embodiment, the metalens 119 of the eighth embodiment described above achieves the same functions and effects as the metalens 118 of the seventh embodiment. Furthermore, the lighting device 100 including the metalens 119 of the eighth embodiment and the projector 1 including the lighting device 100 achieve the same functions and effects as the lighting device 100 and the projector 1 described in the first embodiment.

[0133] In the metalens 119 of the eighth embodiment, each of the multiple metasurface regions 120 is a reflective metasurface. The metalens 119 of the eighth embodiment achieves a reflective diverging lens with a practically low computational load and time for electromagnetic wave analysis, and a higher degree of divergence than the metalens 117 of the fifth embodiment. Furthermore, the metalens 119 of the eighth embodiment shares a common optical path in the Z direction between a portion of the light beam LB incident on the metalens 119 and a portion of the light beam LB emitted from the metalens 119. This allows for a more compact illumination device 100 and projector 1 equipped with the metalens 119, compared to the illumination device 100 and projector 1 of the seventh embodiment.

[0134] While the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments and various modifications and alterations can be made within the scope of the gist of the present invention as described in the claims. Furthermore, the constituent elements of multiple embodiments can be appropriately combined.

[0135] For example, in the metalens (wavefront control element) of the above-described embodiments, the metasurface regions 120 are illustrated as being arranged in four rows by four columns when viewed along the Z direction, aligned with each other in the X and Y directions. However, the relative arrangement and number of the multiple metasurface regions 120 are not particularly limited, and can be freely designed as appropriate, as long as they collectively constitute a single metalens (wavefront control element) and are arranged in an array as described above. For example, the multiple metasurface regions 120 may be arranged in a staggered pattern in the X and Y directions. In this case, as described in the above-described embodiments, the multiple metasurface regions 120 are symmetrical about the center of the metalens on the XY plane. This allows for a reduction in the number of different patterns of the multiple structural bodies 103 in the multiple metasurface regions 120 subject to design evaluation, thereby reducing the computational load and time required for electromagnetic wave analysis during design evaluation.

[0136] Furthermore, in the metalens (wavefront control element) of each of the above-described embodiments, the shape of each of the plurality of metasurface regions 120 as viewed from the Z direction is not limited to a rectangle, but may be any shape such as a circle or a parallelogram.

[0137] Furthermore, in the metalens (wavefront control element) of the present invention, each of the multiple metasurface regions may not have a converging or diverging function, and may deflect a light beam (incident light) in a direction intersecting the direction of incidence into the metalens. In this case, the metalens as a whole can constitute an ultrathin lens array composed of multiple metasurface regions having nanometer-scale structures.

[0138] For example, the metalenses of the aforementioned embodiments can also be used in an illumination device or light source device of a scanner optical system (not shown). In this case, a scanning device can be realized that includes a smaller and thinner metalens and metasurface optical element than conventional ones, while reducing the computational load and time required for electromagnetic wave analysis during design evaluation.

[0139] In addition, the metalenses of the above-mentioned embodiments can also be used in projection optical systems for sensing that operate in the infrared band. In this case, an interactive projector is realized that has a metalens and metasurface optical element that is smaller and thinner than before, and that reduces the computational load and time during design evaluation. Furthermore, the metalenses of the above-mentioned embodiments can also be applied to light source devices or projection devices of display devices such as head-mounted displays (HMDs). As a result, the light source device or projection device of the HMD can be miniaturized and made ultra-thin, and the computational load and time of electromagnetic wave analysis during design evaluation of the metalens can be reduced to a practical level.

[0140] The wavefront control element according to the embodiment of the present invention may have the following structure.

[0141] A wavefront control element according to one embodiment of the present invention controls the wavefront of incident light and comprises multiple metasurface regions. The multiple metasurface regions are arranged in an array and each has a lens function. Each of the multiple metasurface regions converges or diverges incident light.

[0142] In the wavefront control element according to one embodiment of the present invention, the plurality of metasurface regions include a first metasurface region and a second metasurface region, and the focal position of the first metasurface region and the focal position of the second metasurface region are identical to each other.

[0143] In the wavefront control element according to one embodiment of the present invention, the plurality of metasurface regions include a first metasurface region and a second metasurface region, and the focal position of the first metasurface region and the focal position of the second metasurface region are different from each other.

[0144] In the wavefront control element according to one embodiment of the present invention, each of the plurality of metasurface regions is a transmission-type metasurface.

[0145] In the wavefront control element according to one embodiment of the present invention, each of the plurality of metasurface regions is a reflective metasurface.

[0146] In the wavefront control element according to one embodiment of the present invention, the plurality of metasurface regions are arranged symmetrically with respect to the center.

[0147] In the wavefront control element according to one embodiment of the present invention, the incident light is converged to a point on the side opposite to the incident side or on the same side as the incident side in the direction along the optical axis of the incident light.

[0148] In the wavefront control element of one embodiment of the present invention, the incident light is focused on a plurality of points along the optical axis of the incident light, the same number as the plurality of metasurface regions, on the opposite side to the incident side or on the same side as the incident side.

[0149] In the wavefront control element according to one embodiment of the present invention, the incident light is diverged on the side opposite to the incident side or on the same side as the incident side in the direction along the optical axis of the incident light.

[0150] The lighting device according to the embodiment of the present invention may have the following structure.

[0151] A lighting device according to one aspect of the present invention includes the wavefront control element described above.

[0152] The projector according to the embodiment of the present invention may have the following configuration.

[0153] A projector according to one embodiment of the present invention includes: the aforementioned illumination device; a light modulator that modulates light from the illumination device according to image information to form image light; and a projection optical system that projects the image light.

Claims

1. A wavefront control element for controlling the wavefront of incident light, wherein: The wavefront control element has a plurality of metasurface regions. The plurality of metasurface regions are arranged in an array and each has a lens function. In each of the plurality of metasurface regions, the incident light is converged or diverged, Each of the plurality of metasurface regions is a reflective metasurface, A half mirror is arranged on the front side of the wavefront control element in the traveling direction of the light beam incident on the wavefront control element.

2. The wavefront control element according to claim 1, wherein: The plurality of metasurface regions include a first metasurface region and a second metasurface region, The focal position of the first metasurface region and the focal position of the second metasurface region are identical to each other.

3. The wavefront control element according to claim 1, wherein: The plurality of metasurface regions include a first metasurface region and a second metasurface region, The focal position of the first metasurface region and the focal position of the second metasurface region are different from each other.

4. The wavefront control element according to any one of claims 1 to 3, wherein: The plurality of metasurface regions are arranged symmetrically with respect to a center.

5. The wavefront control element according to any one of claims 1 to 3, wherein: The incident light is converged to a point on the same side as the incident side in a direction along the optical axis of the incident light.

6. The wavefront control element according to any one of claims 1 to 3, wherein: The incident light is converged on a plurality of points, the number of which is the same as the number of the metasurface regions, on the same side as the incident side in a direction along the optical axis of the incident light.

7. The wavefront control element according to any one of claims 1 to 3, wherein: The incident light is diverged on the same side as the incident side in a direction along the optical axis of the incident light. 8 . A lighting device comprising the wavefront control element according to claim 1 .

9. A projector comprising: The lighting device according to claim 8; a light modulation device for modulating the light from the illumination device according to image information to form image light; and A projection optical system projects the image light.

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