Imaging optical lens, and imaging device

Abstract

To provide an imaging optical lens capable of increasing the light reception using a non-circular lens area.SOLUTION: The imaging optical lens includes: a substrate; and multiple microstructures formed in a main range on the surface of the substrate. When expressing the main range using the polar coordinate system (r, θ) with the center of the optical axis of the imaging optical lens as the origin, the distance R from the origin to the edge of the primary range depends on θ over at least part of the range 0≤θ<2π.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to an imaging optical lens and an imaging device. [Background technology]

[0002] In recent years, research and development of metalenses with fine surface structures called metasurfaces has been progressing. A metasurface is a surface with a metamaterial structure that realizes optical functions that do not exist in nature. A metalense can realize optical functions equivalent to a combination of multiple conventional optical lenses with a single thin, flat structure. For this reason, a metalense can contribute to the miniaturization and weight reduction of devices equipped with lenses, such as cameras, LiDAR sensors, projectors, and AR (Augmented Reality) displays. Examples of metalenses and devices using metalenses are disclosed in, for example, Patent Documents 1 and 2.

[0003] Patent Document 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 brings about an optical phase shift that varies depending on its position, and the optical phase shift caused by 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. Nanofins and nanopillars are given as examples of nanostructures. Patent Document 1 describes that a desired phase shift can be achieved by adjusting the angle of the arrangement of each nanofin or the size of each nanopillar.

[0004] Patent Document 2 discloses a miniaturized lens assembly including a metalens, and an electronic device including the same. The metalens disclosed in Patent Document 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, the width of each of the multiple internal pillars included in the nanostructure array is appropriately determined according to the required phase delay amount in order to realize a desired phase delay profile. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2019-516128 [Patent Document 2] Patent Publication No. 2021-71727 [Non-patent literature]

[0006] [Non-Patent Document 1] JY Jung et al., "Wavelength-selective infrared metasurface absorber for multispectral thermal detection", IEEE Photon. J., vol. 7, no. 6, Dec. 2015. Summary of the Invention [Problem to be solved by the invention]

[0007] In a conventional metalens, a plurality of microstructures are arranged in a circle on the surface of a square substrate as a lens region having a desired lens function. In such a configuration, since the lens region has a circular shape, there is a limit to how wide the lens region can be in the metalens. As a result, it is not easy to increase the amount of received light.

[0008] The present disclosure provides an imaging optical lens that can increase the amount of received light by using a non-circular lens area. [Means for solving the problem]

[0009] An imaging optical lens according to one embodiment of the present disclosure comprises a substrate and a plurality of microstructures disposed within a lens region on a surface of the substrate, and when the lens region is represented by a polar coordinate system (r, θ) having the center of the optical axis of the imaging optical lens as its origin, a distance R from the origin to an edge of the lens region depends on θ in at least a part of the range 0≦θ<2π.

[0010] A comprehensive or specific aspect of the present disclosure may be realized in a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable recording disk, or may be realized in 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 apparatuses. When an apparatus is composed of two or more apparatuses, the two or more apparatuses may be arranged in one device, or may be arranged separately in two or more separate devices. In this specification and the claims, "apparatus" may mean not only one apparatus, but also a system consisting of multiple apparatuses. Effect of the Invention

[0011] According to one aspect of the present disclosure, it is possible to realize an imaging optical lens that is capable of increasing the amount of received light by using a non-circular lens region. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view illustrating a schematic example of a metalens. [Diagram 2] FIG. 2 is a perspective view that illustrates a schematic example of the structure of one unit cell. [Diagram 3] FIG. 3 is a schematic diagram showing the function of a metalens. [Figure 4] FIG. 4 is a schematic diagram illustrating the configuration of a metalens according to the first exemplary embodiment of the present disclosure. [Figure 5A] FIG. 5A is a diagram illustrating an example of an ideal phase profile in the unwrapped state. [Figure 5B] FIG. 5B is a schematic diagram of an ideal phase profile wrapped in the phase range from −π to π. [Figure 5C] FIG. 5C is a diagram illustrating an example of sampling for achieving an ideal phase profile. [Figure 6] FIG. 6 is a diagram illustrating an example of phase contours in a metalens according to embodiment 1. [Figure 7A] FIG. 7A is a schematic ray tracing diagram when light is vertically incident on a metalens according to embodiment 1. [Figure 7B] FIG. 7B is another schematic ray tracing diagram when light is perpendicularly incident on the metalens according to embodiment 1. [Figure 8] FIG. 8 is a diagram for explaining a method for producing a metalens according to embodiment 1. [Figure 9] FIG. 9 is a schematic diagram illustrating a metalens configuration according to exemplary embodiment 2 of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating an example of phase contours in a metalens according to embodiment 2. [Figure 11A] FIG. 11A is a schematic ray tracing diagram when light is perpendicularly incident on a metalens according to embodiment 2. [Figure 11B] FIG. 11B is another schematic ray tracing diagram when light is perpendicularly incident on the metalens according to embodiment 2. [Figure 11C] FIG. 11C is yet another schematic ray tracing diagram when light is perpendicularly incident on the metalens according to embodiment 2. [Figure 12]FIG. 12 is a schematic diagram illustrating a configuration of a metalens according to an exemplary embodiment 3 of the present disclosure. [Figure 13] FIG. 13 is a diagram illustrating an example of phase contours in a metalens according to embodiment 3. [Figure 14A] FIG. 14A is a schematic ray tracing diagram when light is normally incident on a metalens according to embodiment 3. [Figure 14B] FIG. 14B is another schematic ray tracing diagram when light is normally incident on a metalens according to embodiment 3. [Figure 14C] FIG. 14C is yet another schematic ray tracing diagram when light is perpendicularly incident on a metalens according to embodiment 3. [Figure 15A] FIG. 15A is a schematic diagram showing the configuration of a substrate and a microstructure in an example of a metalens. [Figure 15B] FIG. 15B is a graph showing the relationship between microstructure diameter and amount of phase shift, and the relationship between microstructure diameter and transmittance for an example metalens. [Figure 16A] FIG. 16A is a graph showing the phase profile of an embodiment of a metalens. [Figure 16B] FIG. 16B is another graph showing the phase profile of an embodiment of a metalens. [Figure 17A] FIG. 17A shows a ray tracing diagram for normal incidence on an embodiment of a metalens. [Figure 17B] FIG. 17B is another ray tracing diagram for light at normal incidence on an embodiment of a metalens. [Figure 18] FIG. 18 illustrates the intensity distribution of incident light focused onto an imaging plane of an image sensor in an embodiment of a metalens. [Figure 19A] FIG. 19A is a schematic cross-sectional view of an example metalens that includes a light modulating layer. [Figure 19B] FIG. 19B is a cross-sectional view that illustrates a schematic example of a metalens in which the light modulation layer includes a plurality of microstructures different from the microstructure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, exemplary embodiments of the present disclosure will be described. The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, arrangement and connection forms of components, steps, order of steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, components that are not described in the independent claims showing the highest concept are described as optional components. In addition, each figure is a schematic diagram and is not necessarily illustrated strictly. Furthermore, in each figure, the same reference numerals are given to the same or similar components. Duplicate explanations may be omitted or simplified.

[0014] In the present disclosure, the term "light" is not limited to visible light (having a wavelength of about 400 nm to about 700 nm) but is also used for invisible light. Invisible light refers to electromagnetic waves that fall within the wavelength range of ultraviolet light (having a wavelength of about 10 nm to about 400 nm), infrared light (having a wavelength of about 700 nm to about 1 mm), or radio waves (having a wavelength of about 1 mm to about 1 m). The optical lens in the present disclosure can be used not only for visible light but also for invisible light such as ultraviolet light, infrared light, or radio waves.

[0015] (Findings on which this disclosure is based) First, an example of the basic configuration of an optical lens and the findings of the present inventors will be described.

[0016] In the following description, the optical lens is also referred to as a "metalens." A metalens is an optical element that has a plurality of microstructures on its surface that are smaller than the wavelength of incident light, and that realizes a lens function by phase shift caused by these microstructures. By appropriately designing the shape, size, orientation, and arrangement of each microstructure, it is possible to adjust the optical properties, such as the phase, amplitude, or polarization, of the incident light.

[0017] Fig. 1 is a perspective view that illustrates a schematic diagram of an example of a conventional metalens. The metalens 90 illustrated in Fig. 1 includes a substrate 110 and a plurality of microstructures 120 provided on a 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 referred to as a "unit cell." The metalens 90 is an assembly of a plurality of unit cells.

[0018] 2 is a perspective view that illustrates a schematic example of the structure of one unit cell. One unit cell includes a part of a substrate 110 and one microstructure 120 that protrudes from the part of the substrate 110. Each unit cell generates a phase shift for incident light according to the structure of the microstructure 120.

[0019] FIG. 3 is a diagram showing a schematic diagram of the function of the metalens 90. In FIG. 3, the arrows indicate an example of light rays. The metalens 90 in this example has a characteristic of focusing incident light, similar to a conventional convex lens. In the example shown in FIG. 3, the incident light incident on the substrate side of the metalens 90 undergoes a different phase change depending on the position by the array of microstructures 120, and is focused. In order to achieve the desired focusing characteristics, the shape, width, height, orientation, and the like of each microstructure 120 are appropriately determined. The structure of each microstructure 120 can be appropriately determined based on, for example, data indicating the phase profile to be realized and the results of an electromagnetic field simulation.

[0020] Each of the microstructures 120 has a subwavelength size (e.g., width and height) that is shorter than the wavelength of light incident on metalens 90, and may be arranged with a subwavelength spacing or periodicity. 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 substrate 110.

[0021] Metalens 90 may be designed to achieve desired optical properties for light in a predetermined wavelength range of interest. The wavelength range of interest may be, for example, a wavelength range defined by a specification. If the lower limit of the wavelength range of interest 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 wavelength range of interest is in the infrared region of interest, the size and spacing of microstructures 120 may be greater than 1 μm.

[0022] 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 realized. The number of microstructures 120 is within a range of 100 to 10,000, for example, and may be less than 100 or more than 10,000 in some cases.

[0023] 1, metalens 90 has a lens region in which a plurality of microstructures 120 are arranged in a circular shape, and a non-lens region in which a plurality of microstructures 120 are not arranged. The lens region contributes to receiving light, while the non-lens region does not contribute to receiving light. The larger the lens region, the greater the amount of light received, but when the lens region has a circular shape, there is a limit to how wide the lens region can be in metalens 90.

[0024] The present inventors have found the above problem and have come up with an optical lens according to an embodiment of the present disclosure that solves this problem. In the imaging optical lens according to the embodiment of the present disclosure, the amount of received light can be increased by a non-circular lens region. The configuration of the optical lens according to this embodiment will be 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.

[0025] The imaging optical lens according to this embodiment is used for light in a predetermined target wavelength range. The imaging optical lens includes a substrate and a plurality of microstructures provided in a lens region on the surface of the substrate. When the lens region is expressed by a polar coordinate system (r, θ) with the center of the optical axis of the imaging optical lens as the origin, the distance R from the origin to the edge of the lens region depends on θ in at least a part of the range of 0≦θ<2π.

[0026] Here, the "target wavelength range" is a wavelength range of light in which the optical lens is intended to be used, and may be determined based on the specifications of the optical lens or the specifications of an apparatus in which the optical lens is mounted. The target wavelength range may include, for example, at least a portion of the visible light wavelength range (about 400 nm to about 700 nm). Alternatively, the target wavelength range may include at least a portion of the ultraviolet wavelength range (wavelengths of about 10 nm to about 400 nm). Alternatively, the target wavelength range may include at least a portion of the infrared wavelength range (about 700 nm to about 1 mm). Alternatively, the target wavelength range may include at least a portion of the radio wave wavelength range (wavelengths of about 1 mm to about 1 m). In an example, the target wavelength range may include at least a portion of the infrared wavelength range of 2.5 μm to 25 μm. The wavelength range of 2.5 μm to 25 μm may be suitably used for sensing devices that use infrared rays, such as LiDAR sensors or infrared cameras. In this disclosure, the term "wavelength" refers to the wavelength in free space unless otherwise specified.

[0027] The substrate and each microstructure may be made of a material that is translucent to light in the target wavelength range. Here, "translucent" means having a 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.

[0028] 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.

[0029] The interval between the microstructures 120 is determined according to the phase profile that the optical lens is to realize. The phase profile represents the distribution in the lens surface of the shift amount of the phase of the outgoing light relative to the phase of the incoming light of the optical lens (hereinafter, may be simply referred to as "phase"). The phase profile can be expressed, for example, by a function of the phase with respect to the position in the lens surface or the distance from the optical axis. The phase indicated by the phase profile differs depending on the position in the lens surface. In the embodiment, the interval 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 realized.

[0030] The metalenses according to embodiments 1 to 3 are described in detail below. In the metalens according to embodiment 1, the substrate has a square shape, and the lens region of the surface of the substrate has a square shape. In the metalens according to embodiment 2, the substrate has a rectangular shape, and the lens region has a rectangular shape. In the metalens according to embodiment 3, the substrate has a rectangular shape, and the lens region has an elliptical shape. However, the shapes of the substrate and the lens region are not limited to these examples.

[0031] (Embodiment 1) [Example of metalens configuration] An example configuration of a metalens according to the first embodiment of the present disclosure is described below with reference to Figure 4. The metalens according to the first embodiment of the present disclosure may be used in combination with an image sensor, for example, in an imaging device. The metalens may also be used in a telescope, microscope, or scanning optical device.

[0032] FIG. 4 is a schematic diagram illustrating the configuration of a metalens according to exemplary embodiment 1 of the present disclosure. The metalens 100A shown in FIG. 4 includes a substrate 110 having a surface 112. The substrate 110 has a square shape. The surface 112 has a main area 112a and a peripheral area 112b located outside the main area 112a. The hatched area shown in FIG. 4 represents the main area 112a. The main area 112a has a square shape. The peripheral area 112b is more specifically located around and surrounds the main area 112a.

[0033] When the main range 112a is represented by a polar coordinate system (r, θ) with the optical axis center of metalens 100A as the origin, the distance R from the origin to the end of the main range 112a depends on θ in the range of 0≦θ<2π. That is, the main range 112a has a non-circular shape. In the polar coordinate system, the angle in one direction at which the distance R is shortest is set to θ=0. In the range of 0≦θ≦π / 2, the distance R is shortest at θ=0 and π / 2, and is longest at θ=π / 4. θ=0 represents the direction of one side of the square, and θ=π / 4 represents the diagonal direction of the square. The direction of one side is a direction parallel to one side of the square.

[0034] Metalens 100A further includes a plurality of microstructures 120 provided within a main area 112a of surface 112 of substrate 110. A plurality of microstructures 120 is not provided in a peripheral area 112b. For simplicity, FIG. 4 only shows a schematic representation of a plurality of microstructures 120 provided near the center and near the four corners of main area 112a.

[0035] The plurality of microstructures 120 may be provided directly on the surface 112 of the substrate 110, or may be indirectly provided on the surface 112 of the substrate 110 via another member. Alternatively, the plurality of microstructures 120 may be provided on the surface 112 of the substrate 110 at intervals, for example, by using a spacer.

[0036] In a top view seen from a direction perpendicular to surface 112, the region of metalens 100A that overlaps with main region 112a is referred to as lens region 122, and the region that overlaps with peripheral region 112b is referred to as non-lens region 124. In this case, metalens 100A can be said to comprise lens region 122 and non-lens region 124. Because a plurality of microstructures 120 is provided, main region 112a may also be referred to as the "lens region." Because a plurality of microstructures 120 is not provided, peripheral region 112b may also be referred to as the "non-lens region." In this specification, lens region 122 is also referred to as the "first region," and non-lens region 124 is also referred to as the "second region."

[0037] Lens region 122, which has a square shape, functions as a lens and shifts the phase of incident light. Lens region 122 includes a plurality of microstructures 120. The optical axis of metalens 100A passes through the center of lens region 122. Non-lens region 124 has peripheral area 112b as its surface and does not shift the phase of incident light. Non-lens region 124 does not include a plurality of microstructures 120. Non-lens region 124 is located outside lens region 122. More specifically, non-lens region 124 is located around lens region 122 and surrounds lens region 122. The inner edge of non-lens region 124 coincides with the edge of lens region 122. Non-lens region 124 is a marginal region remaining in the process of producing metalens 100A. A method of producing metalens 100A will be described later.

[0038] In the metalens 100 according to embodiment 1, the lens region 122 has a non-circular shape, such as a square shape, and therefore the lens region 122 can be made sufficiently larger than in a configuration in which the lens region 122 has a circular shape. As a result, it is possible to increase the amount of received light.

[0039] [Lens area design method] 5A to 6, a method for designing the lens region 122 will be described. The interval between two adjacent microscopic structures 120 in the lens region 122 is determined according to a phase profile for achieving a desired lens function.

[0040] FIG. 5A is a diagram showing 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 showing an ideal phase profile wrapped in a phase range from -π to π. FIG. 5C is a diagram showing an example of sampling for realizing an ideal phase profile. Black dots in FIG. 5C indicate examples of the positions (i.e., sampling points) of the microstructures 120. As shown in these figures, an appropriate number of microstructures 120 are arranged for each of a plurality of sections wrapped between -π and π. From the sampling theorem, two or more microstructures 120 are arranged for one continuous section from -π to π.

[0041] 5A to 5C, the phase steepness differs between near the center and near the edge of the lens region 122. The rate of change of the phase Φ with respect to the change in 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 made 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.

[0042] 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.

[0043] FIG. 6 is a diagram schematically showing an example of phase contour lines in the metalens 100A according to Embodiment 1. As shown in FIG. 6, the phase contour lines become denser as the position r increases, reflecting the phase profile shown in FIG. 5A. In the lens region 122, the phase changes according to the phase profile shown in FIG. 5A not only in the range of r≤Ra but also in the range of Ra<r≤Rb. The contour lines have a circular shape at r≤Ra and an arc shape near each of the four corners at Ra<r≤Rb. Therefore, the lens region 122 has a lens function not only in the range of r≤Ra but also in the range of Ra<r≤Rb.

[0044] For a more detailed design of the lens region 122, see, for example, 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 disclosures of these are incorporated herein by reference.

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

[0046] According to JIS B 0621 "Definition and Representation of Geometric Deviations", flatness is defined as "the magnitude of deviation from the geometrically correct plane (geometric plane) of a planar body". Specifically, flatness corresponds to the distance between two virtual planes when the target surface is sandwiched from above and below by two completely flat virtual planes. Flatness can be measured non-contact using a laser beam.

[0047] The width of the non-lens region 124 is the smallest dimension from a point on the inner edge to the outer edge of the non-lens region 124. The gap between the two opposing arrows shown in Figure 4 represents an example of the width of the non-lens region 124. The width of the non-lens region 124 may or may not be constant.

[0048] In metalens 100A, when the width of non-lens region 124 is, for example, 200 μm or less, the width of non-lens region 124 can be made sufficiently narrow. As a result, lens region 122 becomes wider, allowing an increase in the amount of light received.

[0049] On the other hand, if the width of non-lens region 124 is too narrow, then when an object comes into contact with the edge of metalens 100A, there is a possibility that the microstructures 120 located near the edge of lens region 122 may be damaged. If the width of non-lens region 124 is wider than the maximum distance between two adjacent microstructures 120 among the multiple microstructures 120, this possibility can be reduced.

[0050] [Light collection] With reference to Figures 7A and 7B, how incident light is focused by the metalens 100A according to embodiment 1 will be described. Figures 7A and 7B are schematic ray tracing diagrams when light is perpendicularly incident on the metalens 100A according to embodiment 1. The ray tracing diagrams shown in Figures 7A and 7B are side views of substrate 110 having a square shape as viewed in a direction perpendicular to one side and a diagonal, respectively. The straight solid lines shown in Figures 7A and 7B represent incident light rays from an object.

[0051] 7A and 7B show not only metalens 100A, but also image sensor 130 having an imaging surface 132 and detecting 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.

[0052] The image sensor 130 includes a plurality of sensors arranged two-dimensionally. Each of the plurality of sensors is, for example, one selected from the group consisting of a thermopile, a pyroelectric sensor, a bolometer, a diode-type sensor, and a quantum sensor. These sensors are effective when the predetermined target wavelength range is, for example, a wavelength range of mid-infrared (about 2.5 μm to about 4 μm), far-infrared (about 4 μm to about 1 mm), terahertz wave (about 30 μm to about 3 mm), or radio wave (about 1 mm to about 1 m).

[0053] 7A and 7B, metalens 100A focuses incident light from an object onto imaging surface 132 of image sensor 130. Image sensor 130 detects the focused incident light. A configuration including metalens 100A and image sensor 130 corresponds to imaging device 200A that captures an image of an object.

[0054] In the example shown in Figure 7B, the number of incident light rays that are condensed is greater than in the example shown in Figure 7A. This is because incident light rays can be condensed even near both ends in the diagonal direction of lens region 122. Therefore, in metalens 100A, because lens region 122 has a square shape, lens region 122 can be made sufficiently wider than in a configuration in which lens region 122 has a circular shape. As a result, it is possible to increase the amount of light received.

[0055] In the example shown in FIG. 7A, the dimension in one side direction of lens region 122 is 2Ra, and in the example shown in FIG. 7B, the dimension in the diagonal direction is 2Rb. Thus, the numerical aperture NA of metalens 100A is Ra / f in the direction of one side of lens region 122, and is Rb / f in the diagonal direction of lens region 122. If the distance R defined according to θ is R(θ), and the numerical aperture NA defined according to θ is NA(θ), then NA(θ)=R(θ) / f. The larger R(θ) is, the larger NA(θ) is. In the range of 0≦θ≦π / 2, the numerical aperture NA(θ) of metalens 100B is minimum at θ=0 and π / 2, and maximum at θ=π / 4.

[0056] [How to make a metalens] Next, a method for producing the metalens 100A according to the first embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram for explaining the method for producing the metalens 100A according to the first embodiment.

[0057] In the first step, a circular semiconductor wafer 140 is prepared as shown in FIG. 8. 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. In 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. In the example shown in FIG. 8, the number of lens regions 122 is 24, but the actual number of lens regions 122 may be, for example, 10. 2 Over 10 4 The same can be said for the number of non-lens regions 124.

[0058] 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 shown in Fig. 8 represent areas of the semiconductor wafer 140 that are located around the lens regions 122 and the non-lens regions 124. These areas are not etched because they were covered with resist, and therefore do not change from the unprocessed semiconductor wafer.

[0059] As shown in the enlarged view, the metalens 100A is obtained by dicing the semiconductor wafer 140 into individual pieces. In dicing, the blade passes between the lens regions 122. The vertical and horizontal dotted lines in the lattice pattern shown in FIG. 8 represent the blade passing lines. The minimum gap between two adjacent lens regions 122 among the lens regions 122 is wider than the width of the blade. Therefore, even if the blade passes through, the possibility that the blade will come into contact with the microstructures 120 located near the ends of each lens region 122 and damage the microstructures 120 can be reduced. As shown in the enlarged view of FIG. 8, the non-lens regions 124 are marginal regions that remain when the semiconductor wafer 140 is diced into individual pieces.

[0060] As described above, in the metalens 100A according to embodiment 1, the lens region 122 has a non-circular shape, such as a square shape, and therefore the lens region 122 can be made sufficiently wide. As a result, it is possible to increase the amount of received light.

[0061] When the predetermined target wavelength range is, for example, the wavelength range of mid-infrared, far-infrared, terahertz waves, or radio waves, whether image sensor 130 is any of the sensors listed above, there is a need to further improve the light receiving sensitivity of image sensor 130. Metalens 100A, which can increase the amount of light received, is effective in these wavelength ranges.

[0062] (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. Metalens 100B illustrated in FIG. 9 differs from metalens 100A illustrated in FIG. 4 in that substrate 110 and lens region 122 have a rectangular shape rather than a square shape. If lens region 122 has a circular shape, lens region 122 will not be sufficiently wide even if the diameter of the circle approximately matches the short side of the rectangle. In contrast, if lens region 122 has a rectangular shape, lens region 122 can be made sufficiently wide, which allows for an increase in the amount of received light.

[0063] [Lens area design method] A method for designing the lens region 122 will be described with reference to Fig. 10. The interval between two adjacent microstructures 120 in the lens region 122 is determined according to the phase profile shown in Fig. 5A. However, the phase contour line has an elliptical shape instead of a circular shape.

[0064] 10 is a diagram illustrating an example of phase contours in the metalens 100B according to embodiment 2. The distance R at θ=0 is Ra1, the distance R at θ=π / 2 is Ra2, and the distance R at θ=arctan(Ra2 / Ra1) is Rb. θ=0, π / 2, and arctan(Ra2 / Ra1) respectively represent the short side direction, long side direction, and diagonal direction of the rectangle. The axis parallel to the short side of the rectangle is the X-axis, the axis parallel to the long side is the Y-axis, the center of the lens region 122 is the origin, and a point in the XY coordinate system is (X, Y)=(x, y).

[0065] As shown in Figure 10, the contour line is (x / Ra1) 2 +(y / Ra2) 2 ≦1. The ellipse has an elliptical shape when (x / Ra1) 2 +(y / Ra2) 2 =1. The contour lines are further divided into (x / Ra1) 2 +(y / Ra2) 2 > 1 and r ≤ Rb, it has the shape of an elliptical arc near each of the four corners. The elliptical arc is (x / Ra1) 2 +(y / Ra2) 2 = 1. Therefore, the lens area 122 is a part of an ellipse that is similar to (x / Ra1) 2 +(y / Ra2) 2 Not only ≦1, but also (x / Ra1) 2 +(y / Ra2) 2 >1 and r≦Rb also have a lens function.

[0066] The configuration of the non-lens area 124 is as described in the first embodiment.

[0067] [Light collection] With reference to Figures 11A to 11C, how incident light is focused by the metalens 100B according to embodiment 2 will be described. Figures 11A to 11C are schematic ray tracing diagrams when light is perpendicularly incident on the metalens 100B according to embodiment 2. The ray tracing diagrams shown in Figures 11A to 11C are side views of a rectangular substrate 110 as viewed in directions perpendicular to the short side, long side, and diagonal, respectively. An imaging device 200B shown in Figures 11A to 11C includes a metalens 100B and an image sensor 130.

[0068] In the example shown in Fig. 11B, the number of incident light rays that are condensed is greater than that in the example shown in Fig. 11A. This is because incident light rays can be condensed even near both ends in the long side direction of lens region 122. In the example shown in Fig. 11C, the number of incident light rays that are condensed is greater than that in the example shown in Fig. 11B. This is because incident light rays can be condensed even near both ends in the diagonal direction of lens region 122.

[0069] In the example shown in Figure 11A, the dimension in the short side direction of lens region 122 is 2Ra1, in the example shown in Figure 11B, the dimension in the long side direction is 2Ra2, and in the example shown in Figure 11C, the dimension in the diagonal direction is 2Rb. Thus, the numerical aperture NA of metalens 100B is Ra1 / f in the short side direction of lens region 122, Ra2 / f in the long side direction of lens region 122, and Rb / f in the diagonal direction of lens region 122. In the range 0≦θ≦π / 2, the numerical aperture NA(θ)=R(θ) / f of metalens 100B is minimum when θ=0 and maximum when θ=arctan(Ra2 / Ra1).

[0070] As described above, in metalens 100B according to embodiment 2, lens region 122 has a non-circular shape, such as a rectangular shape, and therefore lens region 122 can be made sufficiently wide. As a result, it is possible to increase the amount of received light.

[0071] (Embodiment 3) [Metalens configuration] An example configuration of a metalens according to embodiment 3 of the present disclosure will be described below with reference to FIG. 12. FIG. 12 is a schematic diagram illustrating the configuration of a metalens according to exemplary embodiment 3 of the present disclosure. Metalens 100C shown in FIG. 12 differs from metalens 100B shown in FIG. 9 in that lens region 122 has an elliptical shape rather than a rectangular shape. In metalens 100C, lens region 122 is narrower than in metalens 100B. Even so, lens region 122 is wider than in a configuration in which lens region 122 has a circular shape. Therefore, metalens 100C allows for an increased amount of received light compared to a configuration in which lens region 122 has a circular shape.

[0072] [Lens area design method] A method for designing the lens region 122 will be described with reference to Fig. 13. Fig. 13 is a diagram illustrating an example of phase contour lines in the metalens 100C according to embodiment 3. The distance R at θ=0 is Ra1, and the distance R at θ=π / 2 is Ra2. θ=0 and π / 2 represent the minor axis direction and major axis direction of the ellipse, respectively. The axis parallel to the minor axis of the ellipse is the X-axis, the axis parallel to the major axis is the Y-axis, the center of the lens region 122 is the origin, and a point in the XY coordinate system is (X, Y) = (x, y).

[0073] As shown in FIG. 13, the contour line is (x / Ra1) 2 +(y / Ra2) 2 ≦1. The ellipse has an elliptical shape when (x / Ra1) 2 +(y / Ra2) 2 =1. (x / Ra1) 2 +(y / Ra2) 2 =1 includes a circle where r=Ra1. Therefore, the lens area 122 includes not only a circle where r≦Ra1, but also a circle where r>Ra1 and (x / Ra1) 2 +(y / Ra2) 2 Even if the value is less than or equal to 1, the lens function is maintained.

[0074] As described above, the width of non-lens region 124 is the smallest dimension from a point on the inner edge of non-lens region 124 to the outer edge. The double-headed arrow in FIG. 12 represents an example of the width of non-lens region 124. In metalenses 100A and 100B according to embodiments 1 and 2, the width of non-lens region 124 can be, for example, 200 μm or less. In contrast, in metalens 100C according to embodiment 3, the width of non-lens region 124 is not necessarily 200 μm or less.

[0075] [Light collection] With reference to Figures 14A to 14C, how incident light is focused by the metalens 100C according to embodiment 3 will be described. Figures 14A to 14C are schematic ray tracing diagrams when light is perpendicularly incident on the metalens 100C according to embodiment 3. The ray tracing diagrams shown in Figures 14A to 14C are side views of a rectangular substrate 110 as viewed in directions perpendicular to the short side, long side, and diagonal, respectively. An imaging device 200C shown in Figures 14A to 14C includes a metalens 100C and an image sensor 130.

[0076] In the example shown in Fig. 14B, the number of incident light rays that are focused is greater than that in the example shown in Fig. 14A. This is because incident light rays can be focused even near both ends in the long axis direction of lens region 122. In the example shown in Fig. 14C, the number of incident light rays that are focused is smaller than that in the example shown in Fig. 14B, but the number of incident light rays that are focused is greater than that in the example shown in Fig. 14A. This is because the aforementioned distance R increases as θ changes from 0 to π / 2.

[0077] In the example shown in Figure 14A, the dimension along the minor axis of lens region 122 is 2Ra1, and in the example shown in Figure 14B, the dimension along the major axis is 2Ra2. Thus, the numerical aperture NA of metalens 100C is Ra1 / f along the minor axis of lens region 122, and Ra2 / f along the major axis of lens region 122. The numerical aperture NA(θ)=R(θ) / f of metalens 100C is minimum at θ=0 and maximum at θ=π / 2.

[0078] As described above, in metalens 100C according to embodiment 3, lens region 122 has a non-circular shape such as an elliptical shape, and therefore lens region 122 can be made relatively wide. As a result, it is possible to increase the amount of light received.

[0079] In the metalenses 100A-100C according to the above embodiments 1-3, the substrate 110 has a square or rectangular shape, but is not limited to these shapes. The substrate 110 may have any shape, such as, for example, an elliptical or polygonal shape. Furthermore, the lens region 122 has a square, rectangular, or elliptical shape, but is not limited to these shapes. The lens region 122 may have any shape, such as a polygonal shape, except for a circular shape.

[0080] In the metalenses 100A-100C according to embodiments 1-3 above, the distance R described above depends on θ in the range of 0≦θ<2π, but does not need to depend on θ throughout this range. For example, in the metalens 100A shown in FIG. 4A , the four corners of the lens region 122 may be rounded like a circular arc. That is, in the vicinity of θ=π / 4, 3π / 4, 5π / 4, and 7π / 4, the distance R may be constant regardless of θ. If the distance R depends on θ throughout some or all of the range of 0≦θ<2π, i.e., at least in part of this range, a non-circular lens region 122 can be realized.

[0081] (Example) Next, examples of metalens 100A will be described. The examples shown below are the results of simulations. The wavelength of incident light in the simulations is λ=10 μm.

[0082] Hereinafter, with reference to FIGS. 15A to 18, an embodiment of the metalens 100A will be described. FIG. 15A is a diagram schematically showing the structures of the substrate 110 and the microstructure 120 in the embodiment of the metalens 100A. The substrate 110 and the microstructure 120 are made of the same material. As the material, a material mainly composed of silicon with a crystal plane orientation of (100) is used. Note that the crystal plane orientation of silicon may be (110) or (111). Also, a material different from silicon may be used.

[0083] The thickness of the substrate 110 is 500 μm. The substrate 110 and the lens region 122 have a square shape. The size of the lens region 122 is 4 mm × 4 mm. The diameter of the microstructure 120 in the lens region 122 is D = 1.0 μm to 2.4 μm, the height is H = 8.5 μm, and the period is P = 4.6 μm.

[0084] FIG. 15B is a graph showing the relationship between the diameter D of the microstructure 120 and the phase shift amount, and the relationship between the diameter D of the microstructure 120 and the transmittance in the embodiment of the metalens 100A. The phase shift amount is displayed within the range from -π to π. The transmittance varies within the range of 0.58 or more and 0.8 or less with respect to the diameter D = 1.0 μm to 2.4 μm of the microstructure 120.

[0085] FIGS. 16A and 16B are graphs showing the phase profile in the embodiment of the metalens 100A. The coordinates of the graphs shown in FIGS. 16A and 16B are the coordinates in one side direction and the diagonal direction of the lens region 122, respectively. In these coordinates, the center of the lens region 122 is taken as the origin. The phase at the origin is set to 0 (rad). As shown in FIGS. 16A and 16B, the phase in the lens region 122 monotonically decreases with an upward convexity as the position r increases. The phase in the lens region 122 depends on the position r while not depending on θ. Therefore, the contour lines of the phase in the lens region 122 have a circular shape when r ≦ Ra and an arc shape near each of the four corners when Ra < r ≦ Rb, as shown in FIG. 6.

[0086] Figures 17A and 17B are ray tracing diagrams, respectively, for light normally incident on an example of metalens 100A. The ray tracing diagrams shown in Figures 17A and 17B are side views taken in a direction perpendicular to one side and a diagonal, respectively, of square-shaped lens region 122.

[0087] As shown in FIGS. 17A and 17B, metalens 100A functions as a convex lens that focuses incident light rays. The incident light rays are focused on the imaging surface of image sensor 130. Metalens 100A has a focal length of 4.0217 mm. In the example shown in FIG. 17B, the number of focused incident light rays is greater than in the example shown in FIG. 17A. The numerical aperture of metalens 100A is NA=2.0 mm / 4.0217 mm=0.497 in the direction of one side of lens region 122, and NA=2.0 mm×2 in the diagonal direction of lens region 122. 1 / 2 / 4.0217mm=0.703.

[0088] FIG. 18 illustrates the intensity distribution of incident light focused on imaging surface 132 of image sensor 130 in an embodiment of metalens 100A. The central portion is a portion that is 50% or more of the maximum intensity of the intensity distribution of the focused incident light. As shown in FIG. 18, the central portion has a shape that is closer to a square than a circle, reflecting the square shape of lens region 122. Therefore, the amount of received light can be increased compared to a configuration in which lens region 122 has a circular shape.

[0089] As described above, in metalens 100A, because lens region 122 has a non-circular shape, such as a square shape, it is possible to widen lens region 122, thereby enabling an increase in the amount of light received.

[0090] (Modification) Below, modified examples of the metalenses 100A to 100C will be described.

[0091] In the above embodiment, each microstructure 120 is a convex body having a cylindrical shape, but 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 pyramid body having an elliptical cone (including a 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 body 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 pyramid body having an elliptical cone or polygonal pyramid shape.

[0092] In the above embodiment, the substrate 110 and each microstructure 120 are made of the same material, but they may be made of different materials. To suppress unwanted reflection or refraction between the substrate 110 and the array of microstructures 120, the difference between the refractive index of the substrate 110 and the refractive index of each microstructure 120 may be, for example, 10% or less, 5% or less, or 3% or less of the smallest refractive index of the refractive index of the substrate 110 and the refractive index of each microstructure.

[0093] The substrate 110 and each microstructure 120 may be made of a material mainly composed of at least one selected from the group consisting of silicon, germanium, chalcogenide, chalcohalide, zinc sulfide, zinc selenide, fluoride compounds, thallium halides, sodium chloride, potassium chloride, potassium bromide, cesium iodide, and plastic (polyethylene, etc.). Here, the term "main component" refers to a component that is contained in the largest proportion of the material, expressed in mole percent. When the substrate 110 and each microstructure 120 are made of the above-mentioned materials, the transmittance of infrared rays from 2.5 μm to 25 μm can be increased.

[0094] In order to improve the transmittance, an AR (Anti-Reflection) functional film may be additionally formed. In addition to the AR functional film, various light modulation layers having a light modulation function may be provided on the metalens 100.

[0095] FIG. 19A is a cross-sectional view that shows a schematic example of metalenses 100A to 100C that include a light modulation layer 150. The metalenses 100A to 100C in this example include a light modulation layer 150 having a light modulation function on the surface of the substrate 110 opposite to the surface on which the microstructure 120 is provided. The light modulation layer 150 may have an anti-reflection function for incident light, or may have other functions. For example, the light modulation layer 150 may have the function of any of a high-pass filter, a low-pass filter, or a band-pass filter that transmits only light in a target wavelength range. Alternatively, the light modulation layer 150 may be a polarizing filter that transmits only specific polarized light of the incident light. The light modulation layer 150 may also be a filter that attenuates or amplifies the transmission intensity of incident light in a specific wavelength range. The light modulation layer 150 may be an ND (Neutral Density) filter. The light modulation layer 150 may have a function of refracting the incident light at a specific angle. The light modulating layer 150 may be composed of a single layer or multiple layers depending on the desired light modulating function. The light modulating layer 150 may be formed by a film forming method such as a vacuum deposition method or a sputtering method.

[0096] FIG. 19B is a cross-sectional view showing an example of metalenses 100A to 100C in which the light modulation layer 150 includes a plurality of other microstructures 160 different from the microstructures 120. In this example, an array of the microstructures 120 is provided on one surface of the substrate 110, and an array of the other microstructures 160 is provided on the opposite surface of the substrate 110. Each of the other microstructures 160 may be a convex or concave body. The convex or concave body may be, for example, a cone-shaped body having an elliptical cone or polygonal pyramid shape, or a columnar body having an elliptical cylinder or polygonal cylinder shape. The shape, size, and arrangement of the other microstructures 160 may be different from the shape, size, and arrangement of the microstructures 120. The other microstructures 160 can be produced by the same production process as each microstructure 120 described in the above example. By providing an array of microstructures (i.e., a metasurface) on both sides of the substrate 110 as in this example, it becomes easy to realize a lens function that is difficult to realize on only one side.

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

[0098] [Technology 1] A substrate; A plurality of microstructures provided in a lens region on the surface of the substrate; Equipped with When the lens area is represented by a polar coordinate system (r, θ) having the optical axis center of the imaging optical lens as the origin, a distance R from the origin to an end of the lens area depends on θ in at least a part of the range of 0≦θ<2π. Imaging optical lenses.

[0099] In this imaging optical lens, the amount of received light can be increased by the non-circular lens area.

[0100] [Technology 2] The imaging optical lens has a first region which is the lens region, and a second region which is located outside the first region and has a flat surface. The imaging optical lens according to claim 1.

[0101] In this imaging optical lens, the second region does not function as a lens.

[0102] [Technology 3] the width of the second region is greater than the maximum distance between two adjacent microstructures among the plurality of microstructures; The imaging optical lens according to claim 2.

[0103] With this imaging optical lens, even if an object comes into contact with the edge of the imaging optical lens, the possibility of damage to the microstructure located near the edge of the lens region can be reduced.

[0104] [Technology 4] The width of the second region is 200 μm or less. The imaging optical lens according to claim 2 or 3.

[0105] In this imaging optical lens, the width of the second region can be made sufficiently narrow, so that the lens region becomes wider, enabling an increase in the amount of received light.

[0106] [Technology 5] the first region includes the plurality of microstructures; The second region does not include the plurality of microstructures. The imaging optical lens according to any one of Techniques 2 to 4.

[0107] In this imaging optical lens, a desired lens function can be achieved by appropriately designing the multiple microstructures in the first region.

[0108] [Technology 6] The imaging optical lens is used in the wavelength range of mid-infrared, far-infrared, terahertz waves, or radio waves. The imaging optical lens according to any one of the first to fifth aspects.

[0109] The imaging optical lens is effective in these wavelength ranges.

[0110] [Technology 7] When the focal length of the imaging optical lens is f and the distance R defined according to the θ is R(θ), the numerical aperture defined according to the θ is NA(θ)=R(θ) / f. The imaging optical lens according to any one of the first to sixth aspects.

[0111] In this imaging optical lens, the larger R(θ) is, the larger NA(θ) is.

[0112] [Technology 8] The first region has a square shape. The imaging optical lens according to any one of claims 2 to 5.

[0113] In this imaging optical lens, when the substrate has a square shape, the amount of received light can be effectively increased.

[0114] [Technology 9] The first region has a rectangular shape. The imaging optical lens according to any one of claims 2 to 5.

[0115] In this imaging optical lens, when the substrate has a rectangular shape, the amount of received light can be effectively increased.

[0116] [Technology 10] The first region has an elliptical shape. The imaging optical lens according to any one of claims 2 to 5.

[0117] In this imaging optical lens, when the substrate has a rectangular shape, the elliptical lens region can increase the amount of received light compared to a circular lens region.

[0118] [Technology 11] The first region has a polygonal shape. The imaging optical lens according to any one of claims 2 to 5.

[0119] In this imaging optical lens, the polygonal lens area can increase the amount of received light compared to a circular lens area.

[0120] [Technology 12] An imaging optical lens according to any one of techniques 1 to 11; an image sensor for detecting light in a predetermined target wavelength range; Equipped with Imaging device.

[0121] In this imaging device, the amount of received light can be increased by detecting light through the imaging optical lens.

[0122] [Technology 13] the imaging optical lens and the image sensor are disposed at an interval equal to a focal length specified by the imaging optical lens; The greater the distance R, the greater the numerical aperture defined according to θ. The imaging device according to claim 12.

[0123] In this imaging device, light incident on the imaging optical lens can be condensed onto the imaging surface of the image sensor with a sufficient amount of received light.

[0124] [Technology 14] The image sensor includes a plurality of sensors arranged two-dimensionally, Each of the plurality of sensors is one selected from the group consisting of a thermopile, a pyroelectric sensor, a bolometer, a diode-type sensor, and a quantum-type sensor. 14. The imaging device according to claim 12 or 13.

[0125] This imaging device is effective when the predetermined target wavelength range is the wavelength range of mid-infrared rays, far-infrared rays, terahertz waves, or radio waves. [Industrial Applicability]

[0126] 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. [Explanation of symbols]

[0127] 90, 100A~100C Metalens 110 Substrate 112 Surface of the board 112a Main Scope 112b Periphery 120 Microstructure 122 Lens area 124 Non-lens area 130 Image Sensor 132 Imaging surface 140 Semiconductor Wafers 142 Surface of semiconductor wafer 150 Light Modulation Layer 160 Microstructure 200A~200C Imaging area

Claims

1. circuit board and A plurality of microstructures provided within the lens region on the surface of the substrate, An optical lens for imaging, comprising: When the lens region is represented by a polar coordinate system (r, θ) with the optical axis center of the imaging optical lens as the origin, the distance R from the origin to the edge of the lens region depends on θ in at least part of the range 0 ≤ θ < 2π. Let f be the specified focal length of the imaging optical lens, and let R(θ) be the distance R defined according to θ. Then the numerical aperture defined according to θ is NA(θ) = R(θ) / f. The phase profile is determined according to θ such that the numerical aperture at the focal length is satisfied. An imaging optical lens in which the plurality of microstructures are arranged such that the shape and / or period of each of the plurality of microstructures is modulated according to the θ based on the phase profile.

2. The imaging optical lens has a first region which is the lens region and a second region located outside the first region and having a planar surface. The imaging optical lens according to claim 1.

3. The width of the second region is wider than the maximum distance between two adjacent microstructures among the plurality of microstructures. The imaging optical lens according to claim 2.

4. The width of the second region is 200 μm or less. The imaging optical lens according to claim 2.

5. The first region includes the plurality of microstructures, The second region does not include the plurality of microstructures. The imaging optical lens according to claim 2.

6. The aforementioned imaging optical lens is used in the wavelength range of mid-infrared, far-infrared, terahertz waves, or radio waves. The imaging optical lens according to claim 1.

7. The first region has a square shape, The imaging optical lens according to claim 2.

8. The phase contour lines obtained from the phase profile corresponding to θ become denser as the position r in the polar coordinate system (r, θ) increases, Let 2Ra be the dimension in each of the two mutually orthogonal side directions of the square shape, and let 2Rb be the dimension in the diagonal direction of the square shape. The aforementioned contour lines have a circular shape for r ≤ Ra, and the relationship r = Ra holds. The imaging optical lens according to claim 7, wherein the contour lines further have the shape of an arc near each of the four corners of the lens region when Ra < r ≤ Rb, and the arc is part of a circle where r = Ra.

9. The first region has a rectangular shape, The imaging optical lens according to claim 2.

10. The phase contour lines obtained from the phase profile corresponding to θ become denser as the position r in the polar coordinate system (r, θ) increases, The dimensions in the short side direction, long side direction, and diagonal direction of the aforementioned rectangular shape are 2Ra1, 2Ra2, and 2Rb, respectively. When the axes parallel to the short side direction and the long side direction are defined as the X-axis and Y-axis, respectively, and the coordinate point in the XY coordinate system with the center of the lens region as the origin is (X, Y) = (x, y), The aforementioned contour lines have an elliptical shape where (x / Ra1)² + (y / Ra2)² ≤ 1, and are similar to (x / Ra1)² + (y / Ra2)² = 1. The imaging optical lens according to claim 9, wherein the contour lines further have the shape of an elliptical arc near each of the four corners of the lens region when (x / Ra1)² + (y / Ra2)² > 1 and r ≤ Rb, and the elliptical arc is a part of an ellipse that is similar to (x / Ra1)² + (y / Ra2)² = 1.

11. The first region has an elliptical shape, The imaging optical lens according to claim 2.

12. The phase contour lines obtained from the phase profile corresponding to θ become denser as the position r in the polar coordinate system (r, θ) increases, The dimensions in the short axis direction and the long axis direction of the elliptical shape are 2Ra1 and 2Ra2, respectively. When the axes parallel to the short axis and the long axis are defined as the X axis and Y axis, respectively, and the coordinate point in the XY coordinate system with the center of the lens region as the origin is (X, Y) = (x, y), The imaging optical lens according to claim 11, wherein the contour lines have an elliptical shape when (x / Ra1)² + (y / Ra2)² ≤ 1 and are similar to (x / Ra1)² + (y / Ra2)² = 1.

13. The first region has a polygonal shape, The imaging optical lens according to claim 2.

14. An imaging optical lens according to any one of claims 1 to 13, An image sensor that detects light in a predetermined target wavelength range, Equipped with, Imaging device.

15. The imaging optical lens and the image sensor are arranged at intervals corresponding to the focal length of the imaging optical lens according to its specifications. The larger the distance R, the larger the numerical aperture defined according to θ. The imaging apparatus according to claim 14.

16. The aforementioned image sensor comprises a plurality of sensors arranged in two dimensions, Each of the aforementioned plurality of sensors is selected from the group consisting of thermopiles, pyroelectric sensors, bolometers, diode-type sensors, and quantum-type sensors. The imaging apparatus according to claim 14.

17. The imaging device according to claim 14, wherein the imaging surface of the image sensor is square in shape.

18. The imaging device according to claim 14, wherein the imaging surface of the image sensor has a rectangular shape.

19. The imaging device according to claim 16, wherein the plurality of sensors arranged two-dimensionally on the image sensor have a rectangular shape.

Images