Metalens design method and optical design software and system

Abstract

To provide a metalens design method for designing a metalens having an optical action equivalent to that of a single lens optically designed to achieve a desired optical action.SOLUTION: A method for designing a metalens equivalent in optical action to a simple lens optically designed to achieve a desired optical action includes a database preparing step S2, a flat glass specifying step S3, a phase-difference-distribution specifying step S4, and a metasurface-structure specifying step S5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to metalens design methods and optical design software and systems. [Background technology]

[0002] Recently, the application of metamaterials, which are artificial materials that do not exist in nature and have a fine periodic structure shorter than the wavelength of light, to various technologies has been proposed. However, because metamaterials have a three-dimensional fine periodic structure, it is not necessarily easy to actually fabricate them.

[0003] A two-dimensional fine periodic structure formed on the surface of a naturally occurring material is called a "metasurface," and because it is easier to manufacture than metamaterials, it is intended for application in the fields of communications and optics (Patent Document 1).

[0004] One possible use of metasurfaces in the optical field is to form a so-called "aspherical lens (which is widely used in various optical devices, but due to the special nature of the lens surface, it is not always easy to inexpensively realize the lens surface as designed)" by "forming a metasurface on the flat glass surface of flat glass" to achieve an optical effect equivalent to that of an aspherical lens.

[0005] A lens function equivalent to that of an aspherical lens, etc., achieved by forming a metasurface on the glass surface of a flat glass is referred to as a "metalens" below. The tiny units that make up a metasurface are called "metaatoms."

[0006] The FDTD method has been commonly used to design and analyze metasurfaces. While this method allows for "simulations close to reality," it has the drawback of requiring a long design time when used in a design method that combines metasurfaces with optical systems.

[0007] In addition, because aspherical surfaces and metalenses have different shapes, when designing equivalent metalenses, differences in the amount of sag will result in differences in the optical path. In order to compare the performance differences, it is necessary to create both models within the same software. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a metalens design method for designing a metalens that has an optical effect equivalent to that of a single lens that has been optically designed to achieve a desired optical effect. [Means for solving the problem]

[0009] The metalens design method of the present invention is a method for designing a metalens that is optically equivalent in terms of its optical effect to a single lens that has been optically designed to achieve a desired optical effect, and includes the following steps: a database preparation step of preparing a phase difference database containing correspondences between parameter information of meta-atoms that are arranged on a plane to form a metasurface and phase differences; a flat glass plate identification step of setting a flat mirror surface at a position within a design space equivalent to that of the single lens with respect to an image plane and identifying design parameters of the flat glass plate; a phase difference distribution identification step of setting a flat mirror surface at the position of the image plane, determining the phase distribution of a group of rays at the position of the surface on which the metasurface is formed via the flat glass plate from the side of the flat mirror surface, and identifying, as a phase difference distribution, the difference between this phase distribution and the incident-side phase distribution of a group of rays incident on the single lens at the surface on which the metasurface is formed; and a metasurface structure identification step of identifying a metasurface structure using the meta-atoms by comparing the phase difference distribution identified in the phase difference distribution identification step with the phase difference database. [Effects of the Invention]

[0010] According to the metalens design method of the present invention, it is possible to design a metalens using existing optical design software. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a process diagram of a metalens design method. [Figure 2] FIG. 1 is a diagram illustrating a metalens design method. [Figure 3] FIG. 1 is a diagram illustrating a method for designing a metalens having optical functions equivalent to those of a single lens. [Figure 4] FIG. 10 is a diagram for explaining a phase difference distribution. [Figure 5] FIG. 1 illustrates an example of a metalens design. [Figure 6] FIG. 10 is a diagram showing an example of a phase difference distribution using gradation. [Figure 7] FIG. 7 is a diagram showing the relationship between the diameter of the micropillar that gives the phase difference distribution shown in FIG. 6 and the phase difference. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following description will be made with reference to the drawings. Figure 1 is a process diagram of the metalens design method. The metalens design method is made up of steps S1 to S6.

[0013] Process S1 is the "start process" which starts the design process. Step S2 is a "database preparation step" in which the correspondence between the parameter information of meta-atoms arranged on a plane to form a metasurface and the phase difference is prepared as a "phase difference database."

[0014] Step S3 is the "flat glass identification step," which is a step of identifying the flat glass on which the metasurface is to be formed. Step S4 is a "phase difference distribution specification step" in which the phase difference distribution corresponding to the metasurface to be formed is specified.

[0015] Step S5 is the "metasurface structure identification step," in which the phase difference distribution identified in step S4 is compared with the phase difference database prepared in step S2 to identify it as a metasurface structure made of meta-atoms. Step S6 is the "termination step," which ends the design method process with the metasurface structure identified in step S5.

[0016] These steps are carried out as a design process, and in particular, step S4, the "phase difference distribution specifying step," is carried out by automatic calculation using optical system design software.

[0017] As mentioned above, a "metasurface" is composed of a two-dimensional arrangement of tiny "protrusions" called "metaatoms" on the surface of an optical material. An example of a metaatom is a "micropillar." "Pillar" means a column, and a micropillar is a tiny column.

[0018] The micropillars can have a variety of columnar shapes, including cylindrical, elliptical, and rectangular shapes such as square pillars. The thickness of the pillars can be the same for all micropillars, or multiple types of micropillars with different thicknesses can be used. Furthermore, two-dimensional arrays of meta-atoms such as micro-pillars can take various forms, such as square matrix, concentric circles, and elliptical arrays.

[0019] The metasurface formed by the two-dimensional arrangement of meta-atoms has a fine periodic structure with a period shorter than the wavelength of light.

[0020] The following description will be given taking a micro-pillar as an example of a meta-atom. The thickness, shape, arrangement, etc. of the micropillars are parameters that specify the metasurface and are the "parameter information" mentioned above.

[0021] As is well known, the "phase difference" given to light passing through a metasurface can be determined by "determining the parameters such as thickness, shape, and arrangement" of the micropillars that make up the metasurface. The phase difference given to light by the metasurface corresponds to the "refractive index," and the larger the phase difference, the larger the refraction angle.

[0022] In the "database preparation step" of step S2, the database is prepared as a phase difference database that contains the correspondence between the parameter information (thickness, shape, arrangement, etc.) of the micropillars (metaatoms) that are arranged on a plane to form the metasurface and the "phase difference corresponding to the refractive index." This database may be newly created depending on the metalens to be designed, or existing data may be used.

[0023] "Flat glass" is a glass plate with both sides parallel to each other, and a metasurface is formed on one or both sides of it. The phase difference distribution created by the formed metasurface allows the metasurface to perform "an optical function equivalent to that of a lens surface."

[0024] In step S3, the "flat glass identification step," the flat glass on which the metasurface is to be formed is identified. In the flat glass specification process, a position equivalent to the "position relative to the image plane" of the single lens (which has been optically designed in advance to achieve the desired optical effect) to be replaced by the metalens is specified as the position of the flat glass in the "design space (space in the software)" where the design software is executed, and shape parameters such as the thickness of the flat glass and material parameters such as the refractive index are set as design parameters.

[0025] When a single lens is used alone, the "image plane" is the image plane of the image formed by the single lens. When the single lens is "one of a lens system consisting of multiple lenses," the image plane is "the image plane formed by this lens system."

[0026] In step S4, the "phase difference distribution identification step," the phase difference distribution of the metasurface that realizes an optical effect equivalent to that of the single lens is identified. The determination of the phase difference distribution will be described later.

[0027] Step S5, the "metasurface structure identification step," is a step of identifying the metasurface structure by comparing the phase difference distribution identified in step S4 with the phase difference database prepared in step S2. In other words, if a "two-dimensional array of micropillars (metaatoms)" that realizes the phase difference distribution determined in step S4 is formed on flat glass as a metasurface, the optical action of the flat glass can be made to match the "optical action of a single lens."

[0028] As the optical design software (ray tracing program) in the above description, for example, commercially available "CODEV (registered trademark)" can be used.

[0029] The following description will be made with reference to FIG. 2 and subsequent figures. FIG. 2 is a diagram illustrating the design of a metalens 20 that can achieve an optical effect equivalent to that of a single lens 10 that is rotationally symmetric about the optical axis. FIG. 2(a) is a diagram showing the optical action of the single lens 10 in the design space.

[0030] Figure 2 shows the design space. In FIG. 2(a), the symbol AX denotes the optical axis, the symbol p denotes an "object point on the optical axis AX", the symbol IS denotes an "imaging plane", and the symbol q denotes an image point corresponding to the object point p.

[0031] 2(a), the symbols L0 and L1 indicate maximum angle of view rays. That is, an aperture stop (not shown) is arranged on the object point side of the single lens 10, and among the rays limited by this aperture stop, the maximum angle of view rays L0 and L1 are those with the maximum angle of view. The single lens 10 (hereinafter also simply referred to as the lens 10) is a "plano-convex lens" in which the lens surface 11 on the object side is convex and the lens surface 12 on the image side is flat.

[0032] The lens surface 11 is an "aspherical surface (hereinafter also referred to as the aspherical surface 11)." In this example, the aspherical surface 11 is designed to correct spherical aberration. Therefore, the image-forming rays emitted from the object point p are imaged at the image point q on the image plane IS, and the phases of all the image-forming rays at the image point q are the same.

[0033] That is, the single lens 10 is optically designed in advance so as to realize the optical action shown in FIG. 2(a).

[0034] FIG. 2(b) shows, in solid lines, a metalens 20 that is optically equivalent to lens 10 shown in dashed lines.

[0035] As shown in FIG. 2(c), the metalens 20 has a metasurface MS formed on one surface of a flat glass, in this example, the incident surface 21. Hereinafter, surface 21 will also be referred to as the "metasurface surface 21." Surface 22 on the image side is the glass surface of the flat glass itself. To avoid any confusion, the flat glass on which the metasurface MS is to be formed will also be referred to as flat glass 20. The thickness of the metasurface MS is extremely thin, at only a few micrometers.

[0036] In the example shown in FIG. 2, the flat glass forming the metalens 20 is made of the same glass material as the lens 10, and its thickness is equal to the thickness of the lens 10 on the optical axis AX.

[0037] Therefore, as shown in Figure 2(b), the metasurface surface 21 coincides with the position on the optical axis AX of the object-side surface 11 of the lens 10, and the image-side surface 22 of the flat glass 20 coincides with the image-side flat lens surface 12 of the lens 10.

[0038] That is, in FIG. 2(b), in the "software design space" in which the design software is executed, a position equivalent to the "position relative to the image plane IS" of the single lens 10 replaced by the metalens 20 is specified as the position of the flat glass 20.

[0039] FIG. 2( c ) shows the optical effect of metalens 20. Metalens 20 is placed at a position "equivalent to single lens 10 in the design space" and forms an image q of object point p onto image plane IS.

[0040] This means that in FIG. 2(a), the wavefront of the imaging light beam at an arbitrary position (denoted as A) on the image plane IS side of lens 10 (temporarily referred to as the "fundamental wavefront") is identical to the wavefront of the imaging light beam at position A on the image plane IS side of metalens 20 (temporarily referred to as the "imitation wavefront").

[0041] In other words, the metalens 20, which achieves an optical effect equivalent to that of the lens 10, specifies the phase difference distribution (corresponding to the refractive index distribution) of the metasurface MS so that the above-mentioned imitation wavefront coincides with the fundamental wavefront, and it can be said that the metasurface structure is specified so that the specified phase difference distribution can be "realized as a metasurface MS by an array of micropillars."

[0042] The metasurface structure is identified as part of the design process by comparing the "correspondence between the parameter information of the micro-pillars (meta-atoms) arranged on the incident side of the flat glass 20 to form the metasurface MS and the phase difference distribution" prepared in the database during the database preparation process.

[0043] Below, an example of optically designing a metalens using a lens design program (lens design software) will be described for the example described above with reference to FIG. 2. Fig. 3(a) shows the imaging state (the state shown in Fig. 2(a)) which is the optical action of lens 10. Fig. 3(b) shows the optical action of metalens 20 shown in Fig. 2(c).

[0044] One method of "setting the single lens 10 and metalens 20 in a series in the design space" and running the lens design software is to set the mirror ML at the position of the image plane IS, as shown in Figure 3(c). The mirror surface of the mirror ML is a "planar mirror surface," i.e., a flat mirror surface.

[0045] In this way, metalens 20 becomes a mirror image 20' by mirror ML. To handle this on the object side of the mirror ML in the design space, the position of the metalens 20 can be set in the negative direction from the image plane IS in the lens design software.

[0046] That is, in FIG. 3(c), if the distance on the optical axis AX from surface 12 of lens 10 to image plane IS is l0, and the distance from image plane IS to surface 22' of mirror image 20' of the metalens is l1, then the position of surface 22 of metalens 20 is set to −l1 (=l0).

[0047] If the thickness of the flat glass 20 (denoted as dg) is equal to the lens surface distance on the optical axis of the lens 10, the position of the metasurface MS in the design space will be the position shown in Figure 3(d) (the object-side surface of the metalens 20). Therefore, the position of the metasurface MS in the design space is −(l0+dg).

[0048] Referring to FIG. 4, FIG. 4(a) shows a state in which outermost angle rays L01 and L11, which have been subjected to the lens action of the lens 10, are imaged at an image point q on the image surface IS within the design space. In this state, if the flat mirror surface of mirror ML is set to coincide with image plane IS, as shown in Figure 4(b), the reflected light will follow the image-forming rays of lens 10 toward the negative side, be incident on image-side surface 22 of metalens 20, pass through metalens 20, and reach metasurface MS. Any one of these rays traveling in the negative direction will be called ray Li. The distance from optical axis AX to the point where ray Li is incident on metasurface MS will be called position ri.

[0049] Within the design space, the ray of light that enters the flat glass 20 from the mirror surface ML side and then enters the metasurface MS is called the "ray Li with i as a parameter," and the "phase" at the position ri where the ray Li reaches the metasurface MS is called φ(ri).

[0050] The parameter i is approximately i=5 to 20, and in the example being explained, it is set to i=5. The phases of the five light rays Li incident on the metasurface MS on the metasurface surface are denoted as φi (i = 1 to 5).

[0051] Then, the phase distribution φ(r) of the light beam Li at the position of the metasurface MS is expressed by the following polynomial, where r is the distance from the optical axis AX: φ(r)=(2π / λ0)·ΣC i r 2i (i=1~5) is defined as:

[0052] In this polynomial, λ0 is the "design wavelength", C i is the "phase coefficient".

[0053] Phase coefficient: C i is selected so that all φi (i=1 to 5) satisfy the above polynomial.

[0054] Phase coefficient of the phase distribution by the above polynomial: C i can be calculated automatically using geometric optical system design software such as the aforementioned CODEV.

[0055] On the other hand, if we consider a group of rays (denoted as Lj) incident on the lens 10 from the side of object point p, and the phase distribution of these rays Lj at the "position in the design space of the metasurface MS" is, as above, ψ(r), where r is the distance from the optical axis AX, then the phase distribution: ψ(r) is given by a polynomial similar to the phase distribution: φ(r). This phase distribution is called the "incident-side phase distribution."

[0056] The light rays incident on the lens 10 from the object point q are known as the design result of the single lens 10, and the position of the metasurface MS is determined as a position on the optical axis of the convex surface of the lens 10, so the incident side phase distribution: ψ(r) is known.

[0057] The difference between the absolute values ​​of these phase distributions: φ(r) and the incident side phase distribution: ψ(r), i.e. |ψ(r)|―|ψ(r)|(=Δφ(r).) is called the "phase difference distribution."

[0058] When this phase difference distribution: Δφ(r) is given by the metasurface MS, the absolute value of the phase distribution of the group of rays emerging from the metasurface MS from the image plane IS side through the flat glass 20 to the object point q side matches the incident side phase distribution: ψ(r).

[0059] Two light beams with the same phase distribution have the same wavefront, and therefore the light beam formed by the group of rays emerging from the metasurface MS from the image plane IS side through the flat glass 20 will trace the light beam incident on the single lens 10 in the reverse direction, and the "refractive action" of the metasurface MS will be the same as the refractive action of the single lens 10.

[0060] The correspondence between the phase difference and the parameter information of the meta-atoms (micro-pillars) is already provided as a "phase difference database" in the database preparation process. By comparing this parameter information with the phase difference distribution, the size and arrangement of the meta-atoms that make up the desired metasurface can be determined, and the "metasurface structure" can be specified. This specification process can also be performed automatically using design software.

[0061] The above explanation is about the light rays emitted from the object point p on the optical axis AX. However, for the light rays emitted from the object points (p1, P2, . . . Pk) off the optical axis, the phase difference distribution: Δψk(r) (k = 1, 2, . . . k) can be automatically calculated using the same calculation as above.

[0062] The k phase difference distributions Δψk(r) obtained in this way should be equal to the previously obtained phase difference distributions Δφ(r), but since the phase calculations are performed using a finite number of light rays, it is difficult to match them in a single calculation.

[0063] By repeating the automatic calculations of the lens design software by changing or increasing the number of light rays used in the calculation until Δφ(r) and Δψk(r) match each other within a specified tolerance range, the "desired phase difference distribution" can be obtained, and the metasurface structure that realizes the phase difference distribution obtained in this way can be identified. The optical paths before and after the conversion (the optical path formed by the single lens and the optical path refracted by the metasurface) can be viewed on the same screen on the design software display.

[0064] For the sake of simplicity, the above describes a design method for achieving an imaging function equivalent to that of a single lens 10 by forming a metasurface MS on flat glass 20. However, this is not limited to this, and it is also possible to design a lens system consisting of multiple lenses to replace a specific single lens with a metalens made of flat glass.

[0065] That is, in this case, the phase difference distribution specifying step is as follows. In the design space, a flat mirror is set at the position of the image plane, and the position of the flat glass is set to the minus side of the position of the flat mirror, and the position of the flat glass is set to "a minus side position equivalent to the position of the single lens."

[0066] The structure of the metasurface MS can be determined so that the difference between the phase distribution of the group of light rays incident on the metasurface surface of the flat glass from the image plane side and the "phase distribution of the group of light rays incident on the single lens" on the metasurface surface matches the phase difference distribution.

[0067] In the example described above with reference to Figure 2, the thickness of the flat glass forming metalens 20 was set equal to the "thickness on the optical axis" of the single lens 10 that it replaces. Therefore, as shown in Figure 2(b), metasurface 21 coincides with the position on the optical axis of object-side surface 11 of lens 10, and image-side surface 22 of flat glass 20 coincides with image-side flat lens surface 12 of lens 10.

[0068] It is not necessary that the surface on which the metasurface MS is formed and the lens surface 12 abut each other within the design space. However, it is preferable that the glass surface and the lens surface are “close to or abutting” each other. If the surface of the flat glass on which the metasurface MS is to be formed is separated from the surface of the lens 10, the sag, which is the amount of deviation between the two surfaces, will cause errors in the calculation of the phase difference, so it must be made as small as possible.To achieve this, it is preferable to have the glass surface and the lens surface "close to or abutting" each other within the design space.

[0069] As an example, the design of a metalens having an optical effect equivalent to that of a single lens (plano-convex lens) will be described with reference to FIG. 5.

[0070] Figure 5 shows the design of a metalens 200 that has the optical equivalent of the plano-convex singlet lens 100. The left side of the figure is object space and the right side is image space. Single lens 100 is an aspherical lens, with an aspherical convex lens surface on the object side. The image side surface is flat. The object side surface of the glass plate that forms metalens 200 (on which the metasurface is formed) coincides with the "position on optical axis AX" of the convex lens surface of single lens 100, and the image side surface coincides with the image side surface of single lens 100.

[0071] Image point q1 on image plane IS is an image point corresponding to an object point on the optical axis AX, and image points q2 and q3 are image points corresponding to two object points outside the optical axis AX.

[0072] The single lens 100 has a lens diameter of 20 mm, a lens thickness on the optical axis AX of 5 mm, a focal length of 96.71 mm, and is made of BK7 material.

[0073] A metalens 200 having an optical function equivalent to that of the single lens 100 was designed using the design method described above. The flat glass used was made of the same glass material (BK7) as the single lens 100 and had a thickness of 5 mm.

[0074] As explained above, Figure 6 shows the results of calculating the "phase difference distribution to be formed as a metasurface" on the object side of a flat glass, using a gradation. Since the single lens 100 is symmetric about the optical axis, the phase difference distribution is also symmetric about the optical axis. As the distance r from the optical axis position located at the center of FIG. 6 increases, the phase difference gradually increases from the center, drops to 0 when it reaches a maximum value, increases to the maximum value as the distance r increases, drops to 0 when it reaches a further maximum value, and increases again as the distance r increases.

[0075] The refractive index distribution determined from the phase distribution shown in Figure 6 is constructed as a "metasurface made of an array of micro-pillars."

[0076] The relationship between the diameter of the micropillar and the phase difference is shown in Figure 7. The micropillars were assumed to be cylindrical, and the diameter of their cross section was changed as the pillar diameter. The horizontal axis of Figure 7 represents the pillar diameter (0 to 0.4 μm), and the vertical axis represents the phase delay (degrees). The height of all the micropillars is the same, 1.5 μm.

[0077] A phase difference is generated between adjacent micropillars to change the direction of light refraction. The phase difference changes when the volume of the micropillar (i.e., pillar diameter) is changed. Figure 7 shows the phase change for each pillar diameter with a pitch of 0.4 μm and material of BK7 as an example.

[0078] As the pillar diameter on the horizontal axis in Figure 7 increases, the phase delay increases, but at a certain pillar diameter the phase reaches a maximum value (360 degrees), and at pillar diameters larger than that the phase changes beyond 360 degrees. This is sometimes expressed as a notation of more than 360 degrees, but in Figure 7 the plot starts from 0 degrees.

[0079] By forming a metasurface using this "correspondence relationship between pillar diameter and phase data" as parameter information to realize the phase distribution shown in Figure 6, it is possible to design a metalens 200 that is optically equivalent to the target single lens 100.

[0080] As mentioned earlier, the "optical path before and after conversion" can be confirmed on the same screen on the design software display. Figure 5 shows the optical path before and after the conversion mentioned above on the display. As shown in this figure, the optical path before and after conversion can be confirmed by "superimposing the single lens 100 and the metalens 200 on the same screen."

[0081] Furthermore, as mentioned earlier, if the surface of the flat glass on which the metasurface is to be formed is separated from the surface of the single lens, the sag, which is the amount of deviation between the two surfaces, will cause errors in the calculation of the phase difference.

[0082] In the example of Figure 5, the aspherical surface on the object side of the single lens 100 is a "convex surface," and the surface of the flat glass on which the metasurface is to be formed is a "flat surface." Therefore, there is inevitably a sag, which is a deviation between the convex surface of the single lens 100 and the flat surface on the object side of the flat glass, which causes errors. However, as shown in Figure 5, "the optical paths before and after the transformation can be simultaneously checked on the display of the design software," so it is possible to adjust the behavior of the light rays that are subjected to the refraction effect of the metasurface at this time, and it is also possible to investigate what measures should be taken to address the errors caused by the sag.

[0083] The metalens design method described above can be implemented as optical design software that realizes this, or as a system such as a DVD.

[0084] Although the preferred embodiment of the invention has been described above, the invention is not limited to the specific embodiment described above, and unless otherwise specifically limited in the above description, various modifications and changes are possible within the spirit of the invention as described in the claims. The effects described in the embodiments of the present invention are merely a list of preferred effects resulting from the invention, and the effects of the invention are not limited to "those described in the embodiments." [Explanation of symbols]

[0085] 10 Single Lens 20 Flat lens (Metasurface MS is formed) p Object point on the optical axis q Image point IS image plane ML A mirror set in the design space by matching the flat mirror surface with the image plane IS. [Prior art documents] [Patent documents]

[0086] [Patent Document 1] Special Publication No. 2022-502715

Claims

1. A method for designing a metalens that is optically equivalent to a single lens that has been optically designed to achieve a desired optical effect, comprising: a database preparation step of preparing a database of phase differences that contains correspondences between parameter information of meta-atoms arranged on a plane to form a metasurface and phase differences; a flat glass specification process for setting a flat glass at a position within the design space equivalent to the single lens with respect to the image plane and specifying design parameters of the flat glass; a phase difference distribution specification process for setting a flat mirror surface at the position of the image plane, determining the phase distribution of a group of light rays at the position of the surface on which the metasurface is formed from the side of the flat mirror surface via the flat glass, and specifying the difference between this phase distribution and the incident-side phase distribution of the group of light rays incident on the single lens at the surface on which the metasurface is formed as a phase difference distribution; a metasurface structure identification step of identifying a metasurface structure using the meta-atoms by comparing the phase difference distribution identified by the phase difference distribution identification step with a database of phase differences; METALENS DESIGN METHOD

2. 10. The metalens design method of claim 1, comprising: The phase difference distribution specifying step is a metalens design method in which, in a design space, a flat mirror surface is placed at the position of the image plane, the position of the flat glass is set to the negative side, and the position of the flat glass is set to a negative side position equivalent to the position of the single lens, and the phase difference distribution is specified as the difference between the absolute value of the phase distribution at the surface on which the metasurface is formed of a group of rays that enter the surface from the image plane side via the flat glass, and the absolute value of the phase distribution of a group of rays that are incident on the single lens at the surface.

3. 3. The metalens design method of claim 2, comprising: A metalens design method in which a single lens optically designed to achieve a desired optical effect is an aspherical lens.

4. 4. The metalens design method of claim 3, comprising: a metalens design method in which the flat glass is set in a position where its incident side surface is close to or abuts the incident side surface of the single lens;

5. 5. The metalens design method of claim 4, comprising: a metalens design method in which the single lens has a convex aspherical entrance side and a flat exit side, and the exit-side surface of the flat glass is set to coincide with the flat surface.

6. 10. The metalens design method of claim 1, comprising: A metalens design method that allows the imaging light path through the single lens and the light path refracted by the metasurface to be confirmed on the same screen of the display when the single lens and the metalens are superimposed on the display of the design software.

7. Optical design software and a system for implementing the metalens design method of any one of claims 1 to 6.

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