Planar super-structure lens array for hemispherical ultra-wide-angle imaging and preparation method of planar super-structure lens array

Abstract

The invention provides a planar super-structure lens array for hemispherical ultra-wide-angle imaging and a preparation method of the planar super-structure lens array. The planar super-structure lens array for hemispherical ultra-wide-angle imaging comprises a substrate; the array substrate comprises a substrate body and a plurality of plane super-structure lenses located on the substrate body, the plane super-structure lenses are arranged according to a preset period, the rotation angle of each plane super-structure lens corresponds to the position of the corresponding plane super-structure lens, and the position of each plane super-structure lens corresponds to the level of the corresponding plane super-structure lens. According to the invention, hemispherical ultra-wide-angle imaging can be realized through a planar optical element under an ultra-compact scale, and the integration of the system is improved while distortion is reduced.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a planar metalens array for hemispherical ultra-wide-angle imaging and a preparation method thereof. Background Art

[0002] Wide-angle imaging system is an imaging system that can provide a larger field of view. Compared with ordinary imaging systems, wide-angle imaging can capture more information, so it has attracted much attention in the fields of satellite positioning, unmanned driving, and real-time monitoring. However, the traditional wide-angle imaging system is composed of multiple optical lenses, which are large and heavy. The fisheye lens that can achieve a hemispherical field of view requires more precise assembly, and it is not easy to assemble the lens protection device because the front lens protrudes outward, which not only easily damages the system, but also limits the application of the system in integrated optics. Summary of the invention

[0003] The main purpose of the embodiments of the present invention is to provide a planar metalens array for hemispherical ultra-wide-angle imaging and a preparation method thereof, which improves the integration of the system while reducing distortion.

[0004] In order to achieve the above-mentioned object, an embodiment of the present invention provides a planar metalens array for hemispherical ultra-wide-angle imaging, comprising:

[0005] substrate; and

[0006] A plurality of planar metalenses are located on the substrate, wherein the plurality of planar metalenses are arranged according to a preset period, the rotation angle of the planar metalenses corresponds to the position of the planar metalenses, and the position of the planar metalenses corresponds to the order of the planar metalenses.

[0007] In one embodiment, the phase distribution of the planar metalens depends on the incident angle, the wavelength, the distance from the origin of the planar metalens, the focal length of the planar metalens, and the focal center distance.

[0008] In one embodiment, the focal center distance depends on the incident angle and the focal length of the planar metalens.

[0009] In one embodiment, the period of the planar metalens array corresponds to the wavelength of the planar metalens.

[0010] In one embodiment, the rotation angle of the planar metalens corresponding to the position of the planar metalens includes:

[0011] The rotation angle of the planar metalens corresponds to the angle between the position coordinates of the planar metalens and the horizontal axis.

[0012] The embodiment of the present invention further provides a method for preparing the planar metalens array for hemispherical ultra-wide-angle imaging as described above, comprising:

[0013] providing a substrate;

[0014] Taking the center of the substrate as the origin, arranging plane meta-lenses of various levels on the corresponding coordinate axes;

[0015] Determine the plane meta-lens of the corresponding order according to the position to be filled;

[0016] The planar metalens is rotated according to the rotation angle of the planar metalens to obtain a planar metalens array.

[0017] In one embodiment, it also includes:

[0018] The rotation angle of the planar metalens is determined according to the position of the planar metalens.

[0019] In one embodiment, arranging planar meta-lenses of various levels on corresponding coordinate axes includes:

[0020] Arranging plane metalenses of various levels in sequence on a coordinate axis in one direction in order of level to obtain a plane metalens coordinate axis array;

[0021] The planar meta-lens coordinate axis array is rotated 90° around the origin in sequence to arrange planar meta-lenses of various levels on the coordinate axes in various directions.

[0022] In one embodiment, determining a planar metalens of a corresponding order according to a position to be filled includes:

[0023] Determine the corresponding angle according to the distance from the position to be filled to the origin;

[0024] The plane meta-lens of the corresponding order is determined according to the angle.

[0025] In one embodiment, determining the corresponding angle according to the distance from the position to be filled to the origin includes:

[0026] Determine the corresponding basic coordinate axis distance according to the distance from the position to be filled to the origin;

[0027] The corresponding angle is determined according to the basic coordinate axis distance.

[0028] The planar metalens array for hemispherical ultra-wide-angle imaging and the preparation method thereof of the embodiments of the present invention can achieve hemispherical ultra-wide-angle imaging through planar optical elements at an ultra-compact scale, thereby reducing distortion and improving system integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 is a schematic diagram of a planar metalens array for hemispherical ultra-wide-angle imaging in an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the corresponding relationship between the field of view, the overshoot lens array and the image plane in one embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of the markings of the corresponding relationship between the field of view, the overshoot lens array and the image plane in one embodiment of the present invention;

[0033] Figure 4 is a schematic diagram of light convergence of a meta-lens in an embodiment of the present invention;

[0034] Figure 5 is d(θ i )=f·tanθ i Schematic diagram of the phase distribution on the meta-lens surface under the condition of φ(m / s);

[0035] Figure 6 is d(θ i )=f·sinθ i Schematic diagram of the phase distribution on the meta-lens surface under the condition of φ(m / s).

[0036] Figure 7 is d(θ i )=f·θ i Schematic diagram of the phase distribution on the meta-lens surface under the condition of φ(m / s);

[0037] Figure 8 is a schematic diagram of marking a planar metalens array in an embodiment of the present invention;

[0038] Fig. 9 is a schematic diagram of the origin rotation of a planar metalens in an embodiment of the present invention;

[0039] Fig.10 is a schematic diagram of the rotation of a planar metalens in an embodiment of the present invention;

[0040] Fig.11 is a flow chart of a method for preparing a planar metalens array for hemispherical ultra-wide-angle imaging in an embodiment of the present invention;

[0041] Fig.12is a flow chart of arranging planar meta-lenses of various levels in an embodiment of the present invention;

[0042] Fig.13 is a flow chart of S103 in an embodiment of the present invention;

[0043] Fig.14 is a schematic diagram of the phase distribution of the meta-lens in an embodiment of the present invention;

[0044] Fig.15 is a schematic diagram of a coordinate axis array of a planar metalens in an embodiment of the present invention;

[0045] Fig.16 is a schematic diagram of arranging various levels of planar meta-lenses on coordinate axes in various directions in an embodiment of the present invention;

[0046] Fig.17 is a schematic diagram of determining a planar meta-lens in an embodiment of the present invention;

[0047] Fig.18 Schematic diagram of a rotating metalens in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In view of the fact that traditional wide-angle imaging systems are not only prone to damage to the system, but also limit the application of the system in integrated optics, an embodiment of the present invention provides a planar metalens array for hemispherical ultra-wide-angle imaging and a preparation method thereof. Each metalens in the constructed planar metalens array can converge oblique incident light at different angles, thereby imaging different areas. Ultimately, hemispherical ultra-wide-angle imaging can be achieved through planar optical elements on an ultra-compact scale, thereby reducing distortion and improving the integration of the system.

[0050] Taking a one-dimensional linear metalens array as an example, the phase distribution of the metalens used in a conventional metalens array is completely consistent, and it can only respond to vertically incident light beams, so its imaging angle is greatly limited. Taking the imaging of 'ABCDEFGHIJKLMN' as an example, the imaging angle of a conventional metalens array is limited, and only the words 'EFGHIJ' near the center can be observed on the image plane.

[0051] The difference of the present application is that the phase distribution of each meta-lens is different. The central meta-lens is responsible for collecting the normal incident light, while the meta-lenses towards the edge can collect light with larger incident angles. For example, the leftmost and rightmost meta-lenses are responsible for imaging the words 'KLMN' and 'ABCD' respectively. The present invention is described in detail below with reference to the accompanying drawings.

[0052] Figure 1 Schematic diagram of a planar meta-lens array for hemispherical ultra-wide-angle imaging in an embodiment of the present invention. Figure 1 As shown, the planar meta-lens array for hemispherical ultra-wide-angle imaging includes:

[0053] Substrate ( Figure 1 not shown); and

[0054] A plurality of planar metalenses are located on the substrate, wherein the plurality of planar metalenses are arranged according to a preset period, the rotation angle of the planar metalenses corresponds to the position of the planar metalenses, and the position of the planar metalenses corresponds to the order of the planar metalenses.

[0055] In one embodiment, the period of the planar metalens array corresponds to the wavelength of the planar metalens.

[0056] In one embodiment, the phase distribution of the planar metalens depends on the incident angle, the wavelength, the distance from the origin of the planar metalens, the focal length of the planar metalens, and the focal center distance. The focal center distance depends on the incident angle and the focal length of the planar metalens.

[0057] Figure 2 Schematic diagram of the corresponding relationship between the field of view, the overshoot lens array and the image plane in one embodiment of the present invention. Figure 3 FIG. 1 is a schematic diagram showing the corresponding relationship between the field of view, the overshoot lens array and the image plane in one embodiment of the present invention. Figure 2-Figure 3 As shown, each meta-lens M is responsible for imaging different areas in the hemispherical field of view S onto the P plane.

[0058] The position of each area of ​​the hemispherical field of view in space is determined by two parameters, such as Figure 3 As shown, the angle θ between the line connecting the center of the region and the center of the hemisphere O and the z-axis is i , and the angle between the projection of the line connecting the center of the region and the center of the hemisphere O on the xoy plane and the x-axis Mark a region of the hemispherical field of view as The meta-lens responsible for imaging this region is denoted as The corresponding image plane is The relationship between the field of view S, the meta-lens array M, and the image plane P follows the following formula:

[0059]

[0060] Figure 4 Schematic diagram of light convergence of the meta-lens in the embodiment of the present invention. Figure 4 As shown, the meta-lens M(θ i ,0) can be used to make the incident angle θ i The light rays converge at point F, then the optical path along GAF must be consistent with that along HKF, so the phase compensated by the meta-lens is:

[0061]

[0062] Let K be any point on the metalens, its distance from the origin A be r, the focal length of the metalens be f, and the distance between the focus and the center be d(θ i ), then the phase distribution on the metalens surface must satisfy:

[0063]

[0064] Among them, d(θ i ) with focal length f and incident angle θ i Related, usually can be set as:

[0065] d(θ i )=f·tanθ i ,f·sinθ i ,f·θ i ....

[0066] Figure 5 is d(θ i )=f·tanθ i Schematic diagram of the phase distribution on the metalens surface under . Figure 6 is d(θ i )=f·sinθ i Schematic diagram of the phase distribution on the metalens surface under . Figure 7 is d(θ i )=f·θ i Schematic diagram of the phase distribution on the surface of the meta-lens. Figure 5-Figure 7 As shown, d(θ i ) will affect the phase distribution required by the meta-lens. Under the conditions of incident light wavelength of 532nm, focal length of 10.64μm, and lens radius of 0.665μm, different d(θ i )’s surface phase distribution is inconsistent.

[0067] In one embodiment, the rotation angle of the planar metalens corresponding to the position of the planar metalens includes:

[0068] The rotation angle of the planar metalens corresponds to the angle between the position coordinates of the planar metalens and the horizontal axis.

[0069] Figure 8 Schematic diagram of the marking of the planar meta-lens array in the embodiment of the present invention. Fig. 9 Schematic diagram of the origin rotation of the planar metalens in an embodiment of the present invention. Fig.10 Schematic diagram of the rotation of the planar meta-lens in the embodiment of the present invention. Figure 8-Figure 10 As shown in the figure, according to the phase calculation formula of the single-chip meta-lens, the phase distribution is related to θ i Related to No. and M(θ i ,0) is consistent with the overall phase distribution, and only M(θ i ,0) perform the overall rotation operation. The specific rotation operation is as follows Fig. 9 As shown, firstly, M(θ i ,0) Rotate around point O Angle, at this time and M(θ i ,0) is as follows:

[0070]

[0071] Then Around point D Rotation Angle, such as Fig.10 , can be obtained and The coordinate correspondence between them is:

[0072]

[0073] Among them, r (distance from the center) and angle k (angle from the center) are used to mark the metalens The location of different points on the.

[0074] The specific structural units of the present invention can be changed arbitrarily according to preferences and goals. For example, if the super lens array is to work in the visible light band, its material can be selected from gallium nitride or titanium dioxide, and if the super lens array is to work in the near infrared, silicon and other materials can also be selected; if the geometric phase is to be used to achieve the corresponding phase distribution, the structural unit can be designed as a cuboid or a triangle; if the propagation phase is to be used to achieve the corresponding phase distribution, the structural unit can be designed as a cylinder.

[0075] Based on the same inventive concept, an embodiment of the present invention also provides a method for preparing a planar metalens array for hemispherical ultra-wide-angle imaging. Since the principle of solving the problem by this method is similar to that of the planar metalens array for hemispherical ultra-wide-angle imaging, the implementation of this method can refer to the implementation of the planar metalens array for hemispherical ultra-wide-angle imaging, and the repeated parts will not be repeated.

[0076] Fig.11 FIG. 1 is a flow chart of a method for preparing a planar metalens array for hemispherical ultra-wide-angle imaging in an embodiment of the present invention. Fig.11 As shown, the flow chart of the method for preparing a planar metalens array for hemispherical ultra-wide-angle imaging includes:

[0077] S101: providing a substrate.

[0078] S102: Arranging planar meta-lenses of various levels on corresponding coordinate axes with the center of the substrate as the origin.

[0079] Fig.12 FIG. 1 is a flow chart of arranging various levels of planar meta-lenses in an embodiment of the present invention. Fig.12 As shown, the planar meta-lenses of various levels arranged on the corresponding coordinate axes include:

[0080] S201: Arranging planar metalenses of various levels in sequence on a coordinate axis in one direction in order of level to obtain a planar metalens coordinate axis array.

[0081] In specific implementation, multiple levels can be designed within -90° to 0°, and the total number of levels is the size of the meta-lens array database. For example, in this example, [-90, 0] is divided into 10 levels, namely 0, -10, -20, -30, ... -80, -90. What this means is that the incident light angle responsible for imaging of each meta-lens is 0, -10, -20, -30... Although 10 equally spaced levels are set in this embodiment, this is not a mandatory condition to be achieved. The total number of levels and the interval between each level can be changed freely, but too few levels may lead to reduced imaging quality.

[0082] According to the phase distribution formula of the meta-lens surface:

[0083] The phase distribution of each order of meta-lens can be calculated. Fig.14 Schematic diagram of the phase distribution of the meta-lens in the embodiment of the present invention. Fig.14 As shown, the focal length, radius, working wavelength and period of each meta-lens are consistent. Here, it is assumed that the focal length is 500 microns, the radius is 250 microns, the unit period is 500 nanometers, the working wavelength is 532 nanometers, and d(θ) = f*θ.

[0084] Fig.15 Schematic diagram of the coordinate axis array of the planar meta-lens in an embodiment of the present invention. Fig.15 As shown, starting from the simplest -x axis arrangement, the [-90,0] plane metalenses are arranged in order on the -x axis, and the metalens corresponding to 0° is located at the origin.

[0085] S202: Rotate the planar metalens coordinate axis array 90° around the origin in sequence to arrange planar metalenses of various levels on the coordinate axes in various directions.

[0086] Fig.16 Schematic diagram of the arrangement of various levels of planar metalenses on the coordinate axes in various directions in an embodiment of the present invention. The present invention takes the metalens corresponding to -10° as an example to establish the arrangement of the metalens array on the +y, +x, and -y axes. Fig.16 As shown in the figure, auxiliary arrows are used to represent the definition of the operation of "rotating around the origin". The meta-lens rotates 90° clockwise around the origin to complete the +y-axis arrangement, rotates 180° clockwise around the origin to complete the +x-axis arrangement, and rotates 270° clockwise around the origin to complete the -y-axis arrangement. According to this method, the -20°, -30°, -90° meta-lenses are rotated and arranged around the origin in turn, and finally the wide-field image information on the x-axis and y-axis can be collected, corresponding to angles of -90° to 90°.

[0087] S103: Determine a planar meta-lens of a corresponding order according to the position to be filled.

[0088] Table 1

[0089]

[0090]

[0091] Table 1 is a table showing the relationship between d(θ) corresponding to each metalens in the embodiment of the present invention and the distance from the center of the metalens to the origin O. As shown in Table 1, f in Table 1 is the focal length, and r is the radius of the metalens.

[0092] In the specific implementation, first determine which metalens in the database needs to be filled at any position in the array. Select any position in the array that needs to be filled with a metalens, calculate the distance from the position to the origin, and assume that the distance is X. Find the distance G when the function F = |XG| reaches the minimum value in Table 1, and its corresponding angle θ, and then select the metalens corresponding to the angle in the database.

[0093] Fig.13 is a flow chart of S103 in an embodiment of the present invention. Fig.13 As shown, S103 includes:

[0094] S301: Determine a corresponding angle according to the distance from the position to be filled to the origin.

[0095] In one embodiment, S301 includes:

[0096] The corresponding basic coordinate axis distance is determined according to the distance from the to-be-filled position to the origin, and the corresponding angle is determined according to the basic coordinate axis distance.

[0097] S302: Determine a planar meta-lens of a corresponding order according to the angle.

[0098] Fig.17 Schematic diagram of determining a planar meta-lens in an embodiment of the present invention. Fig.17 As shown in the figure, when the meta-lens at (4r, 6r) is determined (as shown in the dotted box), the calculated distance X is 7.21r. When the distance G is 8r, the function F has a minimum value, and the corresponding angle is -40°, then the -40° meta-lens in the database is selected, and the arrow auxiliary shows that the phase distribution of the meta-lens at point M is completely consistent with that of the -40° meta-lens in the database (located on the -x axis).

[0099] S104: Rotate the planar metalens according to the rotation angle of the planar metalens to obtain a planar metalens array.

[0100] In one embodiment, before executing S104, the method further includes: determining a rotation angle of the planar metalens according to a position of the planar metalens.

[0101] In order to achieve hemispherical imaging, the metalens needs to be rotated. If the coordinates of the metalens are M(x0, y0), then atan(y0, x0) is used to calculate the angle between the line MO connecting the position and the origin and the -x axis. The calculated angle is the rotation angle. Fig.18 Schematic diagram of a rotating meta-lens in an embodiment of the present invention. Fig.18 As shown, at this time, the angle between MO and the -x axis is 124°, so the metalens at M needs to rotate 124° clockwise around its center position. It can be found that the direction of the arrow has changed.

[0102] In summary, the planar metalens array for hemispherical ultra-wide-angle imaging and the preparation method thereof provided by the embodiments of the present invention can realize hemispherical ultra-wide-angle imaging at an ultra-compact scale, facilitate integration, have no spherical aberration and distortion, and play a corresponding role in unmanned driving, real-time monitoring, and satellite positioning. In addition, the present invention can realize multi-wavelength or even broadband achromatic hemispherical ultra-wide-angle imaging by reasonably setting the material of the metalens, the arrangement of the metaunits, and optimizing the corresponding structural dimensions.

[0103] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A planar metalens array for hemispherical ultra-wide-angle imaging, characterized in that: include: substrate; as well as A plurality of planar metalenses are located on the substrate, wherein the plurality of planar metalenses are arranged according to a preset period, the rotation angle of the planar metalenses corresponds to the position of the planar metalenses, and the position of the planar metalenses corresponds to the order of the planar metalenses.

2. The planar metalens array for hemispherical ultra-wide-angle imaging according to claim 1, characterized in that: The phase distribution of the planar metalens depends on the incident angle, wavelength, distance from the origin of the planar metalens, focal length of the planar metalens and focal center distance.

3. The planar metalens array for hemispherical ultra-wide-angle imaging according to claim 2, characterized in that: The focal center distance depends on the incident angle and the focal length of the planar metalens.

4. The planar metalens array for hemispherical ultra-wide-angle imaging according to claim 1, characterized in that: The period of the planar metalens array corresponds to the wavelength of the planar metalens.

5. The planar metalens array for hemispherical ultra-wide-angle imaging according to claim 1, characterized in that: The rotation angle of the planar metalens corresponding to the position of the planar metalens includes: The rotation angle of the planar metalens corresponds to the angle between the position coordinates of the planar metalens and the horizontal axis.

6. A method for preparing a planar metalens array for hemispherical ultra-wide-angle imaging according to any one of claims 1 to 5, characterized in that: include: providing a substrate; Taking the center of the substrate as the origin, arranging plane meta-lenses of various levels on the corresponding coordinate axes; Determine the plane meta-lens of the corresponding order according to the position to be filled; The planar metalens is rotated according to the rotation angle of the planar metalens to obtain a planar metalens array.

7. The method for preparing a planar metalens array according to claim 6, characterized in that: Also includes: The rotation angle of the planar metalens is determined according to the position of the planar metalens.

8. The method for preparing a planar metalens array according to claim 6, characterized in that: Planar meta-lenses of various levels arranged on the corresponding coordinate axes include: Arranging plane metalenses of various levels in sequence on a coordinate axis in one direction in order of level to obtain a plane metalens coordinate axis array; The planar meta-lens coordinate axis array is rotated 90° around the origin in sequence to arrange planar meta-lenses of various levels on the coordinate axes in various directions.

9. The method for preparing a planar metalens array according to claim 6, characterized in that: The planar meta-lenses of corresponding order determined according to the position to be filled include: Determine the corresponding angle according to the distance from the position to be filled to the origin; The plane meta-lens of the corresponding order is determined according to the angle.

10. The method for preparing a planar metalens array according to claim 9, characterized in that: Determining the corresponding angle according to the distance from the position to be filled to the origin includes: Determine the corresponding basic coordinate axis distance according to the distance from the position to be filled to the origin; The corresponding angle is determined according to the basic coordinate axis distance.

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