Optical lens and manufacturing method for same

Abstract

This optical lens comprises a plurality of substrates arranged two-dimensionally or one-dimensionally, wherein respective surfaces of the plurality of substrates are provided with a plurality of fine structures corresponding to a part of a single lens.

Description

Optical lens and method for manufacturing the same

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to optical lenses and methods for making the same.

[0002] In recent years, research and development of metalenses, which have fine surface structures known as metasurfaces, has progressed. Metasurfaces are surfaces with metamaterial structures that realize optical functions not found in nature. Metalenses can achieve optical functions equivalent to those achieved by combining multiple conventional optical lenses with a single thin, flat structure. Therefore, metalenses can contribute to the miniaturization and weight reduction of lens-equipped devices, such as cameras, LiDAR sensors, projectors, and augmented reality (AR) displays. Examples of metalenses and devices using metalenses are disclosed in, for example, Patent Documents 1 and 2.

[0003] Patent Literature 1 discloses a metalens including a substrate and a plurality of nanostructures arranged on the substrate. In this metalens, each of the plurality of nanostructures produces an optical phase shift that varies depending on its position, and the optical phase shift due to each nanostructure defines the phase profile of the metalens. The optical phase shift of each nanostructure depends on the position of the nanostructure and the size or orientation of the nanostructure. Examples of nanostructures given include nanofins and nanopillars. Patent Literature 1 describes that a desired phase shift can be achieved by adjusting the angle at which each nanofin is arranged or the size of each nanopillar.

[0004] Patent Literature 2 discloses a miniaturized lens assembly including a metalens, and an electronic device including the same. The metalens disclosed in Patent Literature 2 includes a nanostructure array and is configured to form the same phase delay profile for at least two different wavelengths of light included in incident light. In this metalens, to achieve a desired phase delay profile, the width of each of the multiple internal pillars included in the nanostructure array is appropriately determined according to the required amount of phase delay.

[0005] JP 2019-516128 A JP 2021-71727 A

[0006] JY Jung et al., "Wavelength-selective infrared metasurface absorber for multispectral thermal detection", IEEE Photonics Journal, vol. 7, no. 6,Dec. 2015.

[0007] While conventional metalenses have multiple microstructures on a single substrate, which limits the size of the metalense, the present disclosure provides optical lenses with larger sizes by arranging multiple substrates, each with multiple microstructures.

[0008] An optical lens according to one aspect of the present disclosure comprises a plurality of substrates arranged two-dimensionally or one-dimensionally, and the surface of each of the plurality of substrates is provided with a plurality of microstructures corresponding to portions of a single lens.

[0009] A general or specific aspect of the present disclosure may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable recording disk, or as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. The computer-readable recording medium may include a non-volatile recording medium such as a CD-ROM (Compact Disc-Read Only Memory). An apparatus may be composed of one or more devices. When an apparatus is composed of two or more devices, the two or more devices may be located in a single device or may be located separately in two or more separate devices. In this specification and claims, the term "apparatus" may refer not only to a single device but also to a system consisting of multiple devices.

[0010] According to one aspect of the present disclosure, a large-sized optical lens can be realized by arranging a plurality of substrates, each of which has a plurality of microstructures provided thereon.

[0011] FIG. 1 is a perspective view schematically illustrating an example of a metalens. FIG. 2 is a perspective view schematically illustrating an example of the structure of a unit cell. FIG. 3 is a diagram schematically illustrating the function of a metalens. FIG. 4 is a diagram schematically illustrating the configuration of a metalens according to a first exemplary embodiment of the present disclosure. FIG. 5A is a diagram schematically illustrating an example of an ideal phase profile in an unwrapped state. FIG. 5B is a diagram schematically illustrating an ideal phase profile wrapped in a phase range from -π to π. FIG. 5C is a diagram schematically illustrating an example of sampling for achieving an ideal phase profile. FIG. 6 is a diagram schematically illustrating an example of phase contours in a metalens according to the first embodiment. FIG. 7A is a diagram illustrating a method of fabricating a metalens according to the first embodiment. FIG. 7B is a diagram illustrating a method of fabricating a metalens according to the first embodiment. FIG. 8 is a side view schematically illustrating a modified example of a metalens according to the first embodiment. FIG. 9 is a diagram schematically illustrating the configuration of a metalens according to a second exemplary embodiment of the present disclosure. FIG. 10A is a diagram illustrating a method of fabricating a metalens according to the second embodiment. Fig. 10B is a diagram illustrating a method for fabricating a metalens according to embodiment 2. Fig. 10C is a diagram illustrating a method for fabricating a metalens according to embodiment 2. Fig. 10D is a diagram illustrating a method for fabricating a metalens according to embodiment 2.

[0012] Exemplary embodiments of the present disclosure will be described below. The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concepts will be described as optional components. Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Furthermore, in each figure, the same or similar components are assigned the same reference numerals. Duplicate descriptions may be omitted or simplified.

[0013] In this disclosure, the term "light" is not limited to visible light (wavelength of about 400 nm to about 700 nm) but also refers to invisible light. Invisible light refers to electromagnetic waves within the wavelength range of ultraviolet light (wavelength of about 10 nm to about 400 nm), infrared light (wavelength of about 700 nm to about 1 mm), or radio waves (wavelength of about 1 mm to about 1 m). The optical lenses in this disclosure can be used not only for visible light but also for invisible light such as ultraviolet light, infrared light, or radio waves.

[0014] (Findings that Form the Basis of the Present Disclosure) First, an example of the basic configuration of an optical lens and the findings of the present inventors will be described.

[0015] In the following description, optical lenses are also referred to as "metalens." A metalens is an optical element that has a plurality of microscopic structures on its surface that are smaller than the wavelength of incident light, and that achieves lens function by the phase shift caused by these microscopic structures. By appropriately designing the shape, size, orientation, and arrangement of each microscopic structure, it is possible to adjust the optical properties of incident light, such as the phase, amplitude, or polarization.

[0016] FIG. 1 is a perspective view schematically illustrating an example of a conventional metalens. The metalens 90 shown in FIG. 1 includes a substrate 110 and a plurality of microstructures 120 provided on the surface of the substrate 110. In this example, each microstructure 120 is a columnar body (also called a "pillar") having a shape similar to a cylinder. A unit element in the metalens 90 that includes one microstructure 120 is called a "unit cell." The metalens 90 is an assembly of a plurality of unit cells.

[0017] 2 is a perspective view schematically illustrating an example of the structure of one unit cell. One unit cell includes a portion of a substrate 110 and one microstructure 120 protruding from the portion of the substrate 110. Each unit cell generates a phase shift in incident light according to the structure of the microstructure 120.

[0018] FIG. 3 is a diagram schematically illustrating the function of the metalens 90. In FIG. 3, arrows indicate exemplary light rays. The metalens 90 in this example has the property of focusing incident light, similar to a conventional convex lens. In the example shown in FIG. 3, incident light entering the substrate side of the metalens 90 is focused by undergoing a phase change that varies depending on the position due to the array of microstructures 120. The shape, width, height, orientation, and the like of each microstructure 120 are appropriately determined to achieve the desired focusing properties. The structure of each microstructure 120 can be appropriately determined, for example, based on data indicating the phase profile to be achieved and the results of an electromagnetic field simulation.

[0019] Each of the microstructures 120 has a subwavelength size (e.g., width and height) that is shorter than the wavelength of light incident on the metalens 90, and may be arranged at subwavelength intervals or periods. The "spacing" of the microstructures 120 is the distance between the centers of two adjacent microstructures 120 when viewed in a direction perpendicular to the surface of the substrate 110.

[0020] Metalens 90 may be designed to achieve desired optical properties for light in a predetermined target wavelength range. The target wavelength range may be, for example, a wavelength range defined by a specification. If the lower limit of the target wavelength range is, for example, 1 μm, the size and spacing of microstructures 120 may be set to a value less than 1 μm. Such microstructures with a nanoscale size less than 1 μm are sometimes referred to as "submicron structures" or "nanostructures." If the target wavelength range is in the infrared region, the size and spacing of microstructures 120 may be greater than 1 μm.

[0021] The number of microstructures 120 provided on the surface of metalens 90 is determined to an appropriate number depending on the lens function to be achieved. The number of microstructures 120 is, for example, within a range of 100 to 10,000, and may be less than 100 or more than 10,000 in some cases.

[0022] In conventional metalenses, multiple microstructures are provided on a single substrate. Therefore, the size of conventional metalenses is limited. The inventors have identified this problem and devised an optical lens according to an embodiment of the present disclosure that solves this problem. According to an embodiment of the present disclosure, by arranging multiple substrates, each of which has multiple microstructures provided thereon, it is possible to realize a large-sized optical lens that functions as a single lens. The configuration of the optical lens according to this embodiment is described below. Note that the structure of each microstructure 120 in the conventional metalens 90 and the design method thereof can also be applied to the optical lens according to this embodiment.

[0023] An optical lens according to an embodiment of the present disclosure is used for light in a predetermined target wavelength range, and includes a plurality of substrates arranged two-dimensionally or one-dimensionally, each of which has a surface provided with a plurality of microstructures corresponding to portions of a single lens.

[0024] Here, the "target wavelength range" refers to the wavelength range of light in which the optical lens is intended to be used, and can be determined based on the specifications of the optical lens or the specifications of the device in which the optical lens is installed. The target wavelength range may include, for example, at least a portion of the visible light wavelength range (approximately 400 nm to approximately 700 nm). Alternatively, the target wavelength range may include at least a portion of the ultraviolet wavelength range (wavelengths of approximately 10 nm to approximately 400 nm). Alternatively, the target wavelength range may include at least a portion of the infrared wavelength range (approximately 700 nm to approximately 1 mm). Alternatively, the target wavelength range may include at least a portion of the radio wave wavelength range (wavelengths of approximately 1 mm to approximately 1 m). In one example, the target wavelength range may include at least a portion of the infrared wavelength range from 2.5 μm to 25 μm. The 2.5 μm to 25 μm wavelength range may be suitable for use in sensing devices that utilize infrared light, such as LiDAR sensors or infrared cameras. In this disclosure, the term "wavelength" refers to the wavelength in free space unless otherwise specified. In addition, in this disclosure, the term "single lens" refers to one lens.

[0025] The substrate and each microstructure 120 may be made of a material that is translucent to light in the target wavelength range. Here, "translucent" means having the property of transmitting incident light with a transmittance of more than 50%. In an embodiment, the substrate 110 and each microstructure 120 may be made of a material that transmits light in the target wavelength range with a transmittance of 80% or more.

[0026] The "spacing" of the microstructures means the distance between the centers of two adjacent microstructures when viewed from a direction perpendicular to the surface of the substrate (hereinafter also referred to as the "lens surface"). If the shortest wavelength in the target wavelength range is, for example, 2.5 μm, the distance between the centers of any two adjacent microstructures among the multiple microstructures is shorter than 2.5 μm. Note that since the width of the microstructures is smaller than the spacing between the microstructures, the width of the microstructures is also shorter than the shortest wavelength in the target wavelength range.

[0027] The spacing between the microstructures 120 is determined according to the phase profile that the optical lens is to achieve. The phase profile represents the distribution within the lens surface of the amount of phase shift of the outgoing light relative to the phase of the incoming light of the optical lens (hereinafter, sometimes simply referred to as "phase"). The phase profile can be expressed, for example, by a function of the phase with respect to the position within the lens surface or the distance from the optical axis. The phase indicated by the phase profile differs depending on the position within the lens surface. In the embodiment, the spacing between the microstructures is determined to differ depending on the position on the lens surface (e.g., the distance from the optical axis) according to the phase profile that is to be achieved.

[0028] The metalenses according to embodiments 1 and 2 are described in detail below. In embodiment 1, a metalens that functions as a single lens is obtained by arranging four substrates in a 2-row, 2-column arrangement. In embodiment 2, a metalens that functions as a single lens is obtained by arranging nine substrates in a 3-row, 3-column arrangement. However, the number of substrates is not limited to four or nine. The number of substrates may be two, three, five to nine, or ten or more. The multiple substrates may be arranged two-dimensionally or one-dimensionally.

[0029] (Embodiment 1) [Example of a Metalens Configuration] An example of a metalens configuration according to embodiment 1 of the present disclosure will be described below with reference to FIG. 4 . A metalens according to embodiment 1 of the present disclosure may be used in combination with an image sensor, for example, in an imaging device. Metalens may also be used in telescopes, microscopes, or scanning optical devices. However, metalens are not limited to these applications.

[0030] Figure 4 is a diagram schematically illustrating the configuration of a metalens according to exemplary embodiment 1 of the present disclosure. The metalens 100A shown in Figure 4 includes four substrates 110 arranged two-dimensionally, more specifically, in two rows and two columns. The side surfaces of two adjacent substrates 110 face each other.

[0031] Each substrate 110 has a square shape. The four substrates 110 form a square shape. Of the four substrates 110, the side surfaces of two adjacent substrates 110 are bonded to each other. This bonding may be, for example, bonding via an adhesive or direct bonding without an adhesive. In direct bonding, the side surfaces of the two adjacent substrates 110 are cleaned and surface-treated, and then bonded to each other while applying pressure and / or heat.

[0032] In the case of bonding via an adhesive, the side surfaces of two adjacent substrates 110 are separated from each other by the distance of the adhesive. In the case of direct bonding, the side surfaces of two adjacent substrates 110 are in contact with each other. In this specification, "two surfaces facing each other" refers not only to the case where the two surfaces are separated from each other, but also to the case where the two surfaces are in contact with each other.

[0033] The surface 112 of each substrate 110 has a main area 112a and a peripheral area 112b located outside the main area 112a. The hatched area shown in Figure 4 represents the main area 112a. The main area 112a has a quarter-circle shape. More specifically, the peripheral area 112b is located around the main area 112a and surrounds it.

[0034] A main area 112a of the surface 112 of each substrate 110 is provided with a plurality of microstructures 120 corresponding to portions of a single lens. For simplicity, FIG. 4 schematically illustrates the plurality of microstructures 120 provided near the right angle of a quarter circle of the main area 112a. The peripheral area 112b is not provided with a plurality of microstructures 120. However, as shown in FIG. 4, alignment marks 126 may be provided in the portion of the peripheral area 112b with a large margin. The alignment marks 126 are useful for properly orienting the substrate 110 to form a single lens. In the example shown in FIG. 4, the alignment marks 126 have a cross shape, but are not limited to this shape. The alignment marks 126 may have, for example, a circular shape, a star shape, or a line shape.

[0035] The plurality of microstructures 120 may be provided directly on the surface 112 of the substrate 110, or may be provided indirectly on the surface 112 of the substrate 110 via another member. Alternatively, the plurality of microstructures 120 may be provided at intervals on the surface 112 of the substrate 110 using, for example, spacers. The same applies to the alignment marks 126.

[0036] In a top view seen from a direction perpendicular to the surface 112, the region of the substrate 110 that overlaps with the main region 112a is the lens region 122, and the region that overlaps with the peripheral region 112b is the non-lens region 124. In this case, it can be said that the substrate 110 comprises the lens region 122 and the non-lens region 124.

[0037] Lens region 122 functions as part of a single lens and shifts the phase of incident light. Lens region 122 includes a plurality of microstructures 120. The lens regions 122 in metalens 100A have the same shape. Each lens region 122a corresponds to one of four equal parts of a circular single lens.

[0038] The non-lens region 124 has a peripheral area 112b as its surface and does not shift the phase of incident light. The non-lens region 124 does not include a plurality of microstructures 120. However, the non-lens region 124 may include an alignment mark 126, as shown in FIG. 4 . The multiple non-lens regions 124 in the metalens 100A have the same shape. The non-lens region 124 is located outside the lens region 122. More specifically, the non-lens region 124 is located around the lens region 122 and surrounds it. The inner edge of the non-lens region 124 coincides with the edge of the lens region 122. The non-lens region 124 is a margin region that remains in the process of fabricating the substrate 110. A method for fabricating the metalens 100A will be described below.

[0039] According to the first embodiment, by arranging four substrates 110 having lens regions 122 of the same shape in two rows and two columns in an appropriate orientation, it is possible to realize a large-sized metalens 100A that functions as a single lens.

[0040] 5A to 6, a method for designing the lens region 122 will be described. The intervals between the microstructures 120 in the lens region 122 are determined according to a phase profile for realizing a desired lens function.

[0041] FIG. 5A is a diagram schematically illustrating an example of an ideal phase profile in an unwrapped state. The horizontal axis represents the coordinate r, with the center of the lens region 122 as the origin, and the vertical axis represents the phase Φ. In the example shown in FIG. 5A, the phase Φ monotonically decreases in an upward convex manner as the position r increases, and the degree of decrease monotonically increases as the position r increases. FIG. 5B is a diagram schematically illustrating an ideal phase profile wrapped in a phase range from −π to π. FIG. 5C is a diagram schematically illustrating an example of sampling for achieving an ideal phase profile. The black dots in FIG. 5C indicate examples of the positions of the microstructures 120 (i.e., sampling points). As shown in these figures, an appropriate number of microstructures 120 are arranged for each of the multiple sections wrapped between −π and π. According to the sampling theorem, two or more microstructures 120 are arranged for each continuous section from −π to π.

[0042] 5A to 5C, the phase steepness differs near the center and near the edge of the lens region 122. The rate of change of the phase Φ with respect to a change in the position r is greater near the edge than near the center. In such a case, the spacing P2 of the microstructures 120 near the edge may be smaller than the spacing P1 of the microstructures 120 near the center. By arranging the microstructures 120 in this manner, the ideal phase profile can be reproduced more accurately.

[0043] The more the number of microstructures 120 included in one continuous section from -π to π, i.e., the number of samples, is increased, the more the reproducibility of the phase profile improves. For example, by arranging three or more or four or more microstructures 120 in each section, the reproducibility of the phase profile can be further improved.

[0044] More detailed designs of the lens region 122 are disclosed, for example, in Japanese Patent Application No. 2022-058051 (filing date: March 31, 2022), Japanese Patent Application No. 2022-058052 (filing date: March 31, 2022), and Japanese Patent Application No. 2022-058053 (filing date: March 31, 2022), the entire contents of which are incorporated herein by reference.

[0045] [Configuration of Non-Lens Region] The configuration of the non-lens region 124 will be described. The peripheral area 112b, which is the surface of the non-lens region 124, is flat. The non-lens region 124, which has a flat surface, does not shift the phase of incident light. Here, "flat" means that the flatness is 25 μm or less when expressed by TTV (Total Thickness Variation).

[0046] According to JIS B 0621 "Definition and Display of Geometric Deviation," flatness is defined as "the magnitude of deviation of a flat object from a geometrically correct plane (geometric plane)." Specifically, flatness corresponds to the distance between two imaginary planes when the target surface is sandwiched between two perfectly flat planes from above and below. Flatness can be measured non-contact using laser light.

[0047] [Spacing Between Two Adjacent Microstructures 120] The total microstructures in the four substrates 110 include a plurality of microstructures 120 within each substrate 110. Of the four substrates 110, there is a boundary between any two adjacent substrates. As shown in FIG. 4 , the spacing d1 between any two adjacent microstructures across the boundary is different from the spacing d2 between any two adjacent microstructures within each substrate 110. More specifically, the minimum value of spacing d1 is greater than the maximum value of spacing d2. This is because non-lens regions 124 are located around the lens regions 122. If the maximum value of spacing d1 is not more than five times the maximum value of spacing d2, metalens 100A will function without any problems as a single lens.

[0048] How incident light is focused by the metalens 100A according to embodiment 1 will be described with reference to Fig. 6. Fig. 6 is a schematic ray tracing diagram when light is perpendicularly incident on the metalens 100A according to embodiment 1. The solid straight lines shown in Fig. 6 represent incident light rays from an object.

[0049] 6 shows not only metalens 100A, but also image sensor 130 having an imaging surface 132 that detects light in a predetermined wavelength range of interest. Metalens 100A and image sensor 130 are spaced apart by the specified focal length f of metalens 100A. The focal point of metalens 100A is located on imaging surface 132 of image sensor 130.

[0050] 6 , metalens 100A focuses incident light rays from an object onto imaging surface 132 of image sensor 130. Image sensor 130 detects the focused incident light rays. A configuration including metalens 100A and image sensor 130 corresponds to an imaging device that captures an image of an object.

[0051] [Method of Fabricating Metalens] Next, a method of fabricating the metalens 100A according to embodiment 1 will be described with reference to Figures 7A and 7B. Figures 7A and 7B are diagrams for explaining the method of fabricating the metalens 100A according to embodiment 1.

[0052] In the first step, a circular semiconductor wafer 140 is prepared, as shown in FIG. 7A . The semiconductor wafer 140 includes a plurality of lens regions 122 arranged two-dimensionally and a plurality of non-lens regions 124 arranged two-dimensionally. Each non-lens region 124 is located around the corresponding lens region 122 and surrounds the corresponding lens region 122. On the surface 142 of the semiconductor wafer 140, a plurality of microstructures 120 are provided in each lens region 122, and a plurality of microstructures 120 are not provided in each non-lens region 124. However, as shown in FIG. 7A , an alignment mark 126 may be provided in each non-lens region 124. In the example shown in FIG. 7A , the number of lens regions 122 is 24, but the actual number of lens regions 122 may be, for example, 10. ２ 10 above ４ The same can be said for the number of non-lens regions 124.

[0053] The semiconductor wafer 140 is obtained by providing a patterned resist on an unprocessed semiconductor wafer, removing unnecessary portions from the unprocessed semiconductor wafer by etching, and then removing the patterned resist. The darkly hatched areas in Figure 7A represent areas of the semiconductor wafer 140 that are located around the plurality of lens regions 122 and the plurality of non-lens regions 124. These areas are not etched because they were covered with resist, and therefore remain unchanged from the unprocessed semiconductor wafer.

[0054] The patterned resist is obtained by processing resist applied to an unprocessed semiconductor wafer using photolithography. In photolithography, the resist is exposed to light through a photomask and a projection lens, in that order, and this operation is repeated with the exposure location changed. The photomask has patterns of the lens regions 122 and alignment marks 126 on one substrate 110. The projection lens reduces the pattern of the photomask and transfers it to the resist. The exposed resist is developed to obtain the patterned resist.

[0055] In the next step, the semiconductor wafer 140 is diced into individual pieces to obtain multiple substrates 110. Each substrate 110 is shown in an enlarged view. The blade passes between the multiple lens regions 122. The multiple dotted lines in the vertical and horizontal grid pattern shown in FIG. 7A represent the blade's passage lines. The smallest gap between two adjacent lens regions 122 among the multiple lens regions 122 is wider than the blade width. Therefore, even if the blade passes through, the possibility of the blade contacting the microstructures 120 located near the edges of each lens region 122 and damaging the microstructures 120 is reduced. The non-lens regions 124 are marginal regions remaining around the substrates 110 obtained by dicing the semiconductor wafer 140.

[0056] The non-lens region 124 has two elongated portions adjacent to the two straight portions of the lens region 122 having a quarter-circle shape, and a wide portion adjacent to the arc portion of the lens region 122. When the width of the elongated portions of the non-lens region 124 is, for example, 10 μm or less, the lens region 122 can be widened. The width of the elongated portions may or may not be constant.

[0057] On the other hand, if the width of the elongated portion of the non-lens region 124 is too narrow, there is a possibility that the microstructures 120 located near the straight portion of the lens region 122 may be damaged when an object comes into contact with the edge of the substrate 110. If the width of the non-lens region 124 is wider than the maximum value of the interval between two adjacent microstructures 120 in the lens region 122, this possibility can be reduced.

[0058] In the next step, as shown in FIG. 7B , four substrates 110 are prepared from the plurality of substrates 110 obtained by singulation. These four substrates 110 constitute the metalens 100A. A plurality of microstructures 120 are provided on the surface 112 of each substrate 110, as shown in FIG.

[0059] In the next step, four substrates 110 are arranged in two rows and two columns in the appropriate orientation, as shown in Figure 4. Of the four substrates 110, the sides of two adjacent substrates 110 are joined together.

[0060] When the arc portions of each lens region 122 face outward in the square shape formed by the four substrates 110, the four lens regions 122 function as a single lens. When the four alignment marks 126 are located at the four corners of the square, the arc portions of each lens region 122 face outward.

[0061] In the example shown in Figure 7B, the upper left substrate 110 corresponds to the upper right substrate 110 rotated 90° counterclockwise. The lower left substrate 110 corresponds to the upper right substrate 110 rotated 180° counterclockwise. The lower right substrate 110 corresponds to the upper right substrate 110 rotated 270° counterclockwise.

[0062] Through the above steps, the metalens 100A according to embodiment 1 can be produced. In photolithography, the area exposed per exposure via a photomask and projection lens is approximately several centimeters square. In photolithography, when the photomask has a single lens pattern, each of the multiple lens regions on the semiconductor wafer functions as a single lens. Although metalenses that function as single lenses can be obtained by singulating the semiconductor wafer, there are limitations on the size of the metalens.

[0063] In contrast, in photolithography, if a photomask has a pattern of part of a single lens, each of the multiple lens regions 122 in the semiconductor wafer 140 functions as part of a single lens. Of the multiple substrates 110 obtained by singulating the semiconductor wafer 140, by arranging four substrates 110 in two rows and two columns in an appropriate orientation, it is possible to produce a large-sized metalens 100A that functions as a single lens. The metalens 100A makes it possible to increase the amount of light received.

[0064] Modification of Embodiment 1 Next, a modification of the metalens 100A according to embodiment 1 will be described with reference to FIG. 8 . FIG. 8 is a side view that schematically illustrates a modification of the metalens 100A according to embodiment 1. The metalens 100A-1 shown in FIG. 8 includes another substrate 150 in addition to the four substrates 110. Four more substrates 110 are disposed on the surface 152 of the other substrate 150. The back surface 114 of each substrate 110 is bonded to face a portion of the surface 152 of the other substrate 150. This bonding may be via an adhesive, or may be direct bonding without an adhesive.

[0065] If the other substrate 150 has a certain level of rigidity or more, the other substrate 150 may function as a support substrate that supports the four substrates 110. Such an other substrate 150 can improve the mechanical strength of the metalens 100A-1. If the four substrates 110 are supported by the other substrates 150, the sides of two adjacent substrates 110 among the four substrates 110 may or may not be bonded to each other. If the sides of two adjacent substrates 110 are not bonded to each other, the two adjacent substrates 110 may be spaced apart by a distance that does not adversely affect the function of the single lens. The other substrate 150 having a certain level of rigidity or more may be made of a material whose Young's modulus is, for example, 1 GPa or more, 10 GPa or more, 50 GPa or more, or 100 GPa or more.

[0066] The other substrate 150 may have an anti-reflection function for light incident on the rear surface 154. Even if the other substrate 150 does not have an anti-reflection function sufficient to suppress the reflection of incident light to several percent or less, as long as the refractive index of the other substrate 150 is lower than the refractive index of each substrate 110, the reflection of light incident on the rear surface 154 of the other substrate 150 can be reduced.

[0067] The other substrate 150 may have a function other than anti-reflection. The other substrate 150 may function as, for example, a high-pass filter, low-pass filter, or band-pass filter that transmits only light in a target wavelength range. Alternatively, the other substrate 150 may be a polarizing filter that transmits only specific polarized light of incident light. The other substrate 150 may also be a filter that attenuates or amplifies the transmission intensity of incident light in a specific wavelength range. The other substrate 150 may also be an ND (Neutral Density) filter. The other substrate 150 may also have a function of refracting incident light at a specific angle. The other substrate 150 may be composed of a single layer or multiple layers depending on the desired light modulation function. The other substrate 150 may also be formed using a film formation method such as vacuum deposition or sputtering.

[0068] As described above, in a modified example of metalens 100A according to embodiment 1, when the other substrate 150 functions as a support substrate, the mechanical strength of metalens 100A-1 can be improved. In addition to the function of a support substrate, the other substrate 150 may have a function of, for example, anti-reflection, transmission, polarization, or refraction of incident light. Alternatively, the other substrate 150 may not have the function of a support substrate, but may have a function of, for example, anti-reflection, transmission, polarization, or refraction of incident light.

[0069] (Embodiment 2) [Metalens Configuration] An example configuration of a metalens according to embodiment 2 of the present disclosure will be described below with reference to FIG. 9 . FIG. 9 is a schematic diagram illustrating the configuration of a metalens according to exemplary embodiment 2 of the present disclosure. The metalens 100B shown in FIG. 9 includes nine substrates 110a-110c arranged two-dimensionally, more specifically, in three rows and three columns. The nine substrates 110a-110c include a central substrate 110a, four substrates 110b positioned above, below, left, and right, and four substrates 110c positioned at the top left, top right, bottom left, and bottom right. The side surfaces of two adjacent substrates 110a, 110b face each other. The same applies to the side surfaces of two adjacent substrates 110b, 110c. The metalens 100B may further include another substrate 150, similar to the metalens 100A-1 shown in FIG. 8 .

[0070] Each of the substrates 110a to 110c has a square shape. The nine substrates 110a to 110c form a square shape. Of the nine substrates 110a to 110c, the side surfaces of two adjacent substrates 110a, 110b are bonded to each other. The same is true for the side surfaces of two adjacent substrates 110b, 110c. This bonding may be, for example, bonding via an adhesive or direct bonding without an adhesive.

[0071] Substrate 110a has lens region 122a and non-lens region 124a located outside thereof. Similarly, substrate 110b has lens region 122b and non-lens region 124b located outside thereof. Substrate 110c has lens region 122c and non-lens region 124c located outside thereof. More specifically, non-lens region 124a is located around lens region 122a and surrounds lens region 122a. Similarly, non-lens region 124b is located around lens region 122b and surrounds lens region 122b. Non-lens region 124c is located around lens region 122c and surrounds lens region 122c. Each of lens regions 122a to 122c includes a plurality of microstructures 120, and each of non-lens regions 124a to 124c does not include a plurality of microstructures 120. However, each of the non-lens regions 124a-124c may include an alignment mark 126, as shown in FIG.

[0072] The nine lens regions 122a to 122c are not identical in shape. Lens region 122a corresponds to the center of a single circular lens divided into nine parts in a grid pattern. The four lens regions 122b have the same shape and correspond to the top, bottom, left, and right parts of the single lens divided into nine parts in a grid pattern. The four lens regions 122c have the same shape and correspond to the upper left, upper right, lower left, and lower right parts of the single lens divided into nine parts in a grid pattern. Because the nine lens regions 122a to 122c are not identical in shape, the nine non-lens regions 124a to 124c are not identical in shape either.

[0073] The total microstructures in the nine substrates 110a-110c include a plurality of microstructures 120 within each of the nine substrates 110a-110c. Of the nine substrates 110a-110c, there is a boundary between any two adjacent substrates 110a, 110b, and there is a boundary between any two adjacent substrates 110b, 110c. As with metalens 100A according to embodiment 1, the spacing d1 between any two adjacent microstructures across the boundary among all the microstructures is different from the spacing d2 between any two adjacent microstructures within each of the substrates 110a-110c among all the microstructures. More specifically, the minimum value of spacing d1 is greater than the maximum value of spacing d2. The maximum value of spacing d1 can be, for example, five times or less the maximum value of spacing d2.

[0074] According to embodiment 2, by arranging nine substrates 110a-110c, each having a lens region 122a-122c that is not identical in shape, in three rows and three columns in an appropriate orientation, it is possible to realize a larger-sized metalens 100B that functions as a single lens. Because the size of metalens 100B according to embodiment 2 is larger than the size of metalens 100A according to embodiment 1, it is possible to further increase the amount of light received.

[0075] [Method of manufacturing metalens] Next, a method of manufacturing the metalens 100B according to embodiment 2 will be described with reference to Figures 10A to 10D. Figures 10A to 10D are diagrams for explaining the method of manufacturing the metalens 100B according to embodiment 2.

[0076] In the first step, a circular semiconductor wafer 140a is prepared, as shown in FIG. 10A . The semiconductor wafer 140a includes a plurality of lens regions 122a arranged two-dimensionally and a plurality of non-lens regions 124a arranged two-dimensionally. Each non-lens region 124a is located around and surrounds the corresponding lens region 122a. In the next step, the semiconductor wafer 140a is diced into individual pieces with a blade passing between the lens regions 122a, thereby obtaining a plurality of substrates 110a. Each substrate 110a is as shown in an enlarged view.

[0077] The above two steps are also performed on circular semiconductor wafers 140b, 140c shown in Figures 10B and 10C. Semiconductor wafer 140b has a plurality of lens regions 122b arranged two-dimensionally and a plurality of non-lens regions 124b arranged two-dimensionally. Each non-lens region 124b is located around and surrounds the corresponding lens region 122a. Semiconductor wafer 140c has a plurality of lens regions 122c arranged two-dimensionally and a plurality of non-lens regions 124c arranged two-dimensionally. Each non-lens region 124c is located around and surrounds the corresponding lens region 122c.

[0078] The method for forming the lens regions 122a to 122c is the same as the method for forming the lens region 122 shown in Fig. 7A. The width of the elongated portions of the non-lens regions 124a to 124c is the same as the width of the elongated portions of the non-lens region 124 shown in Fig. 7A. That is, the width of the elongated portions of each of the non-lens regions 124a to 124c may be, for example, 10 µm or less. The width of the elongated portions of each of the non-lens regions 124a to 124c is, for example, wider than the maximum distance between two adjacent microstructures 120 in the corresponding lens region 122a to 122c.

[0079] It should be noted that a single semiconductor wafer having one or more lens regions 122a, four or more lens regions 122b, and four or more lens regions 122c can also be singulated to obtain the nine substrates 110a-110c included in metalens 100B. However, when forming the semiconductor wafer, the resist is exposed while changing photomasks according to the lens regions 122a-122c.

[0080] In contrast, in the case of the semiconductor wafer 140a shown in Fig. 10A, the resist can be exposed in photolithography without changing the photomask. Therefore, the semiconductor wafer 140a is easily fabricated. The same is true for the semiconductor wafers 140b and 140c shown in Fig. 10B and Fig. 10C.

[0081] In the next step, the nine substrates 110a-110c that constitute the metalens 100B are prepared from the multiple substrates 110a-110c obtained by singulating the semiconductor wafers 140a-140c, as shown in Figure 10D. In the next step, the nine substrates 110a-110c are arranged in three rows and three columns in an appropriate orientation, as shown in Figure 9. Of the nine substrates 110a-110c, the side surfaces of two adjacent substrates 110a, 110b are bonded to each other, and the side surfaces of two adjacent substrates 110b, 110c are bonded to each other.

[0082] In the square shape formed by the nine substrates 110a-110c, the arc portions of the four lens regions 122b on the top, bottom, left, and right sides face outward, and the arc portions of the four lens regions 122c on the top left, top right, bottom left, and bottom right sides face outward. In the above-mentioned square shape, the central lens region 122a has four-fold symmetry, so the lens region 122a may be rotated 90°, 180°, or 270°. Such nine lens regions 122a-122c function as a single lens.

[0083] When the alignment marks 126 on the four substrates 110b are located near the edges of the square, the arc portions of the lens regions 122b face outward. When the alignment marks 126 on the four substrates 110c are located at the four corners of the square, the arc portions of the lens regions 122c face outward.

[0084] In the example shown in Figure 10D, the left substrate 110b corresponds to the top substrate 110b rotated 90° counterclockwise. The bottom substrate 110b corresponds to the top substrate 110b rotated 180° counterclockwise. The right substrate 110b corresponds to the top substrate 110b rotated 270° counterclockwise. Similarly, the top left substrate 110c corresponds to the top right substrate 110c rotated 90° counterclockwise. The bottom left substrate 110c corresponds to the top right substrate 110c rotated 180° counterclockwise. The bottom right substrate 110c corresponds to the top right substrate 110c rotated 270° counterclockwise.

[0085] Through the above steps, the metalens 100B according to embodiment 2 can be produced.

[0086] Although the metalenses 100A, 100B according to embodiments 1 and 2 above have a square shape, they are not limited to a square shape. The metalenses may have any shape, such as a rectangular, circular, elliptical, or polygonal shape.

[0087] Furthermore, in metalenses 100A, 100B according to embodiments 1 and 2, the single lens has a circular shape, but is not limited to a circular shape. The single lens may have any shape, such as a rectangular shape, an elliptical shape, or a polygonal shape.

[0088] Furthermore, in the metalenses 100A and 100B according to embodiments 1 and 2, the single lens is divided into four or nine segments, but is not limited to such divisions. The single lens may also be divided into two, three, five to eight segments, or ten or more segments.

[0089] Furthermore, in the metalenses 100A and 100B according to embodiments 1 and 2, the plurality of substrates 110, 110a to 110c are arranged two-dimensionally, but the present invention is not limited to such an arrangement. The plurality of substrates 110, 110a to 110c may also be arranged one-dimensionally.

[0090] (Shape and Material of Components) Each microstructure 120 may be, for example, a convex body having a cylindrical shape. Alternatively, each microstructure 120 may have a shape other than a cylindrical shape. For example, each microstructure 120 may be a columnar body having an elliptical cylinder or polygonal cylinder shape other than a cylindrical shape. Alternatively, each microstructure 120 may be a pyramidal body having an elliptical cone (including a circular cone) or a polygonal pyramid shape. Furthermore, each microstructure 120 is not limited to a convex body, but may also be a concave body. The convex or concave body constituting the microstructure 120 may have any structure, such as a columnar body having an elliptical cylinder or polygonal cylinder shape, or a pyramidal body having an elliptical cone or polygonal pyramid shape.

[0091] The substrate 110 can be divided into a flat portion having a surface 112 and a plurality of microstructures 120 provided on the surface 112. The flat portion and each of the microstructures 120 may be made of the same material, or they may be made of different materials. To suppress unwanted reflection or refraction between the flat portion and the array of the plurality of microstructures 120, the difference between the refractive index of the flat portion and the refractive index of each of the microstructures 120 may be, for example, 10% or less, 5% or less, or 3% or less of the smallest refractive index between the refractive index of the flat portion and the refractive index of each of the microstructures.

[0092] The materials of the flat plate portion, each microstructure 120, the other substrate 150, and the adhesive are as follows.

[0093] When the predetermined target wavelength range is ultraviolet, visible light, or near-infrared (approximately 700 nm to approximately 2.5 μm), the flat plate portion may be made of a material containing, as a main component, at least one selected from the group consisting of glass, cycloolefin copolymer, cycloolefin polymer, polycarbonate, and fluorene-based polyester. Here, the "main component" refers to the component that is contained in the material in the highest proportion expressed in mole percent. Each microstructure 120 may be made of TiO ２ , Si ３ N ４ , GaN, GaP, diamond, HfO ２ , AlN, and Si. When the flat plate portion and each microstructure 120 are made of the above-mentioned materials, the refractive index of each microstructure 120 is higher than the refractive index of the flat plate portion. The material of the other portions of the substrate 150 may be the same as the material of the flat plate portion, for example.

[0094] When the specified target wavelength range is mid-infrared (approximately 2.5 μm to approximately 4 μm) and far-infrared (approximately 4 μm to approximately 1 mm), the flat portion, each microstructure 120, and other substrates 150 may be made of a material whose main component is at least one selected from the group consisting of, for example, silicon, germanium, chalcogenide, chalcohalide, zinc sulfide, zinc selenide, fluoride compounds, thallium halide, sodium chloride, potassium chloride, potassium bromide, cesium iodide, and plastic (such as polyethylene).

[0095] When the predetermined target wavelength range is ultraviolet light, visible light, near infrared light, mid-infrared light, or near infrared light, the adhesive may be made of a material containing polyimide resin as a main component, for example.

[0096] The refractive index and material of the substrates 110 a to 110 c are the same as those of the substrate 110 .

[0097] [Additional Notes] The above description of the embodiments discloses the following techniques.

[0098] [Technology 1] An optical lens comprising a plurality of substrates arranged two-dimensionally or one-dimensionally, and a plurality of microstructures corresponding to portions of a single lens are provided on the surface of each of the plurality of substrates.

[0099] In this optical lens, the size of the optical lens can be increased by arranging a plurality of substrates.

[0100] [Technology 2] The optical lens according to Technology 1, wherein the side surfaces of two adjacent substrates among the plurality of substrates face each other.

[0101] In this optical lens, the size of the optical lens can be increased by arranging a plurality of substrates so that the side surfaces of two adjacent substrates face each other.

[0102] [Technology 3] The optical lens according to Technology 1 or 2, wherein the side surfaces of two adjacent substrates among the plurality of substrates are bonded to each other.

[0103] In this optical lens, the size of the optical lens can be increased by arranging a plurality of substrates so that the side surfaces of two adjacent substrates are joined to each other.

[0104] [Technology 4] The optical lens according to any one of Technologies 1 to 3, wherein an alignment mark is provided on the surface of each of the plurality of substrates.

[0105] This optical lens allows multiple substrates to be positioned in the appropriate orientation.

[0106] [Technology 5] The optical lens according to any one of Technologies 1 to 4, further comprising another substrate, the plurality of substrates being disposed on a surface of the other substrate.

[0107] In this optical lens, new functions can be realized by using other substrates.

[0108] [Technology 6] The optical lens according to Technology 5, wherein the refractive index of the other substrate is lower than the refractive index of each of the plurality of substrates.

[0109] In this optical lens, the reflection of incident light can be suppressed by the other substrate.

[0110] [Technology 7] The optical lens according to Technology 5 or 6, wherein the other substrate functions as a support substrate that supports the plurality of substrates.

[0111] In this optical lens, the mechanical strength of the optical lens can be improved by the additional substrate.

[0112] [Technology 8] The optical lens according to any one of Technologies 5 to 7, wherein the other substrate has a function of anti-reflection, transmission, polarization, or refraction of incident light.

[0113] In this optical lens, other substrates can prevent reflection of incident light, or transmit, polarize, or refract incident light.

[0114] [Technology 9] An optical lens according to any one of Technologies 1 to 8, wherein all microstructures in the plurality of substrates include the plurality of microstructures in each substrate, there is a boundary between two adjacent substrates among the plurality of substrates, and the spacing between two adjacent microstructures across the boundary among all the microstructures is different from the spacing between two adjacent microstructures within each substrate among all the microstructures.

[0115] Even in the above case, this optical lens can function as a single lens.

[0116] [Technology 10] A method for producing an optical lens, comprising the steps of: preparing a plurality of substrates that constitute an optical lens; and arranging the plurality of substrates two-dimensionally or one-dimensionally, wherein a plurality of microstructures corresponding to portions of a single lens are provided on a surface of each of the plurality of substrates.

[0117] This method for producing an optical lens makes it possible to produce a large-sized optical lens.

[0118] [Technology 11] The method for producing an optical lens according to Technology 10, further comprising, before the step of preparing the plurality of substrates, a step of dicing a semiconductor wafer having a plurality of lens regions arranged two-dimensionally into individual pieces, wherein each of the plurality of lens regions includes the plurality of microstructures.

[0119] In this method for producing an optical lens, a semiconductor wafer is diced into individual pieces, thereby forming a plurality of substrates.

[0120] The imaging optical lens of the present disclosure is widely applicable to devices that utilize lenses, such as cameras, LiDAR sensors, projectors, AR displays, telescopes, microscopes, or scanning optical devices.

[0121] 90, 100A, 100B, 100A-1 Metalens 110 Substrate 112 Surface of substrate 114 Back surface of substrate 120 Microstructure 122, 122a to 122c Lens region 124, 124a to 124c Non-lens region 126 Alignment mark 130 Image sensor 132 Imaging surface 140, 140a to 140c Semiconductor wafer 142 Surface of semiconductor wafer 150 Other substrate 152 Surface of other substrate 154 Back surface of other substrate

Claims

1. An optical lens that functions as a single lens with respect to incident light using multiple different substrates, The first substrate of the plurality of substrates has a surface onto which the light is incident, a main area in which a plurality of microstructures are provided at predetermined intervals and which forms a part of the single lens; a peripheral area outside the single lens where the microstructure is not provided, a plurality of substrates including the first substrate having the main area and the peripheral area are arranged two-dimensionally or one-dimensionally in a direction parallel to the surface, so that the main areas of the plurality of substrates form a single lens, and the peripheral areas of the plurality of substrates form the periphery of the single lens; Optical lens.

2. the first substrate has an end region at an end of the first substrate in the main range where the microstructure is not provided, and the end region has an area smaller than that of the peripheral region; The optical lens according to claim 1 .

3. a distance between the microstructures of the substrate adjacent to the first substrate via the end region is greater than the predetermined distance and is not more than five times the predetermined distance; The optical lens according to claim 2 .

4. alignment marks are provided in the peripheral region of each of the plurality of substrates, and the alignment marks are located at four corners of the optical lens; The optical lens according to claim 1 .

5. Further, another substrate is provided on the opposite side of the surface of the plurality of substrates, the other substrate being sized to accommodate the plurality of substrates. The optical lens according to any one of claims 1 to 3.

6. the refractive index of the other substrate is lower than the refractive index of each of the plurality of substrates; The optical lens according to claim 5 .

7. The other substrate functions as a support substrate for supporting the plurality of substrates. The optical lens according to claim 5 .

8. The other substrate has a function of anti-reflection, transmission, polarization, or refraction of incident light. The optical lens according to claim 5 .

9. Among the plurality of substrates, the side surfaces of two adjacent substrates are joined to each other.

3. The optical lens according to claim 1.

10. A method for fabricating an optical lens in which a plurality of different substrates function as a single lens to incident light, comprising the steps of: A first substrate of the plurality of substrates has, on the surface: a main area in which a plurality of microstructures are provided at predetermined intervals and which forms a part of the single lens; a peripheral area outside the single lens where the microstructure is not provided, providing the plurality of substrates; a step of two-dimensionally or one-dimensionally arranging a plurality of substrates including the first substrate having the main area and the peripheral area in a direction parallel to the surface on which the light is incident; Including, the arranging step causes the main areas of the plurality of substrates to form a single lens, and the peripheral areas of the plurality of substrates to form a periphery of the single lens. How optical lenses are made.

11. The method further includes, before the step of preparing the plurality of substrates, a step of dicing a semiconductor wafer having a plurality of lens regions two-dimensionally arranged to produce the plurality of substrates. A method for producing the optical lens according to claim 10.

12. the plurality of substrates includes a second substrate disposed in a central portion of the single lens and having no outer peripheral area; The optical lens according to any one of claims 1 to 3.