Optical element and light-receiving optical system

Abstract

To appropriately arrange a plurality of microstructures with respect to a shape of a light-receiving surface having a plurality of light-receiving elements.SOLUTION: A first parallel plate 3 is disposed closer to an object side than a light-receiving surface 50, and comprises a base material 3a and a planar optical functional layer 30 including a plurality of microstructures 32 arranged on the base material 3a. The light-receiving surface 50 is formed in a rectangular shape having a long axis d1 and a short axis d2, and a plurality of light-receiving elements 52 are arranged in a lattice pattern along the long axis d1 and the short axis d2. The plurality of microstructures 32 are arranged in a lattice pattern along two basic translation vectors e1 and e2. At least one of the two basic translation vectors e1 and e2 is parallel to at least one of the long axis d1 and the short axis d2 of the light-receiving surface 50.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an optical element and a light receiving optical system that include an optical function layer in which a plurality of microstructures are arranged. [Background technology]

[0002] A technology is known in which a plurality of microstructures arranged in a lattice pattern are used to provide phase modulation to light, thereby providing optical functions similar to those of a lens or prism. For example, Patent Document 1 discloses a metalens in which minute nanostructures are arranged in a square lattice pattern, and Patent Document 2 discloses a lens in which unit cells are arranged in a square lattice pattern or a hexagonal lattice pattern. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-110453 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-92234 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned Patent Documents 1 and 2 do not mention the relationship between the shape of the light-receiving surface having a plurality of light-receiving elements and the arrangement of the microstructure. Since the interaction between an optical element having a lattice-like microstructure and light changes depending on the orientation of the lattice, it is desirable to be able to optimize the arrangement of the microstructure to match the shape of the light-receiving surface. The present invention has been made in view of the above circumstances, and has as its object to suitably arrange a plurality of microstructures relative to the shape of a light-receiving region having a plurality of light-receiving elements. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides: It is located closer to the object than the light receiving surface, An optical element comprising a substrate and a planar optical functional layer including a plurality of microstructures arranged on the substrate, the light receiving surface is formed in a rectangular shape having a major axis and a minor axis, and a plurality of light receiving elements are arranged in a lattice pattern along the major axis and the minor axis; The plurality of microstructures include: are arranged in a grid along two primitive translation vectors, At least one of the two primitive translation vectors is parallel to at least one of the major and minor axes of the light-receiving surface. [Effects of the Invention]

[0006] According to the present invention, a plurality of microstructures can be suitably arranged relative to the arrangement of a plurality of light receiving elements. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram illustrating a light receiving optical system according to an embodiment. [Figure 2] FIG. 2 is a plan view of a light receiving surface according to the embodiment, showing an arrangement of a plurality of light receiving elements on the light receiving surface. [Figure 3] FIG. 2 is a plan view of an optical function layer in which a plurality of microstructures according to an embodiment are arranged in a square lattice pattern. [Figure 4] FIG. 4 is a partially enlarged view of FIG. [Figure 5] FIG. 10 is a plan view of an optical function layer according to a comparative example of the embodiment. [Figure 6] 1 is a plan view of an optical function layer in which a plurality of microstructures according to an embodiment are arranged in a face-centered rectangular lattice pattern. [Figure 7] FIG. 7 is a partially enlarged view of FIG. [Figure 8] FIG. 2 is a plan view of an optical function layer in which a plurality of microstructures according to an embodiment are arranged in a rectangular lattice pattern. [Figure 9] FIG. 10 is a plan view of an optical function layer according to a comparative example of the embodiment. [Figure 10A] FIG. 10 is a diagram showing an example of distribution of shapes of microstructures according to an embodiment, based on an XY polynomial. [Figure 10B] FIG. 10 is a diagram showing an example of distribution of shapes of microstructures according to a comparative example of the embodiment, based on an even-order aspheric surface. [Figure 11] FIG. 10 is a diagram showing a light receiving optical system according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] [Overall configuration of the light receiving optical system] FIG. 1 is a diagram showing a light receiving optical system 1 according to this embodiment. As shown in FIG. 1, the light receiving optical system 1 includes a lens 2, a first parallel plate 3, a second parallel plate 4, and a light receiving sensor 5, in this order from the object side (the left side in FIG. 1).

[0010] The lens 2 is, for example, a convex lens having a predetermined power. The first parallel plate 3 has a planar optical function layer (optical function surface) 30 that is perpendicular to the optical axis Ax of the light receiving optical system 1 on the image side (right side in FIG. 1) surface of a base material 3a such as a silicon substrate or a glass substrate. The first parallel plate 3 is an example of an optical element according to the present invention. The optical function layer 30 will be described later. The second parallel plate 4 is, for example, a cover glass that protects the light-receiving sensor 5 (light-receiving surface 50).

[0011] FIG. 2 is a plan view of the light-receiving sensor 5 (light-receiving surface 50), showing the arrangement of a plurality of light-receiving elements 52 on the light-receiving surface 50. As shown in FIG. The light receiving sensor 5 has a light receiving surface 50 as a photoelectric conversion section that photoelectrically converts incident light. 2, the light receiving surface 50 (the optical opening thereof) is planar and perpendicular to the optical axis Ax, and is formed in a rectangular shape having a major axis d1 and a minor axis d2. The light receiving surface 50 of this embodiment is rectangular, for example, with an aspect ratio of width (long side) to height (short side) of 16:9. On the light receiving surface 50, a plurality of light receiving elements 52, which are photoelectric conversion elements, are arranged in a grid pattern along a major axis d1 and a minor axis d2.

[0012] [Optical functional layer] FIG. 3 is a plan view of the optical function layer 30. As shown in FIG. As shown in this figure, the optical function layer 30 is a so-called metasurface, and includes a plurality of microstructures 32 arranged on a substrate 3a. The microstructures 32 are so-called meta-atoms, which are minute structures whose size is equal to or less than the main design wavelength of the optical function layer 30. The plurality of microstructures 32 exert a phase gradient on light due to the difference in shape between adjacent ones, thereby exhibiting various optical functions including refraction and diffraction. The optical function layer 30 (the optical opening thereof) has a planar shape perpendicular to the optical axis Ax and is formed in a rectangular shape having its major and minor axes in the same direction as the light-receiving surface 50. However, the planar shape of the optical function layer 30 is not particularly limited, and it may be a rectangular shape whose major and minor axes are oriented in different directions from the light-receiving surface 50, or it may not be a rectangular shape.

[0013] [Microstructure arrangement] The microstructures 32 are two-dimensionally arranged in a lattice pattern along two primitive translation vectors e1 and e2 in a plane perpendicular to the optical axis Ax, at least one of which is parallel to at least one of the major axis d1 and the minor axis d2 of the light-receiving surface 50.

[0014] The operation of this embodiment will be described. When multiple microstructures 32 exert optical functions by applying a phase gradient to light, a desired phase profile cannot be reproduced if there is a phase difference of π [rad] or more between two adjacent microstructures 32. Even if the phase difference is not so steep, a small phase difference between adjacent microstructures 32 is preferable to maintain good light utilization efficiency. Therefore, it is desirable to shorten the distance between adjacent microstructures 32 and precisely control the shape of the microstructures 32 that occupy the space in the microscopic region. However, microfabrication with such high precision is difficult, and in reality, stray light occurs in regions where the phase profile changes abruptly, and light utilization efficiency decreases. In general, a light-collecting element such as an optical element (metalens) having an optical function layer 30 requires a steeper phase change to interact with light as it moves away from the optical axis Ax. Therefore, as shown in Fig. 5, the largest phase change occurs in the peripheral portion of the light-receiving surface 50 in the diagonal direction. If the microstructures 32 are arranged such that the distance between adjacent microstructures 32 in the diagonal direction of the light-receiving surface 50 is large, stray light and a decrease in light utilization efficiency will occur in this peripheral region F. For example, when the microstructures 32 are arranged in a square lattice pattern, if the direction in which the distance between the microstructures 32 is shortest is aligned with the direction of one diagonal axis d3 of the light-receiving surface 50, the distance between the microstructures 32 will increase in the direction of the other diagonal axis d4. In this case, a peripheral region F with poor light utilization efficiency and poor imaging characteristics will be generated asymmetrically with respect to the light-receiving surface 50. In this regard, according to the present embodiment, at least one of the primitive translation vectors e1, e2 of the arrangement of the microstructures 32 is parallel to at least one of the major axis d1 and the minor axis d2 of the light-receiving surface 50. In other words, the arrangement direction of the microstructures 32 is set to correspond to the arrangement direction of the light-receiving elements 52 on the light-receiving surface 50. This makes it possible to suppress the asymmetric characteristic degradation described above.

[0015] The following describes specific examples of the arrangement of the microstructures 32. The parallel relationships of the two primitive translation vectors e1 and e2 with respect to the major axis, minor axis, and diagonal axis of the light receiving surface 50 in each arrangement example are shown in Table 1 below. [Table 1]

[0016] <Arrangement example 1: square lattice> Fig. 3 is a plan view of an optical function layer 30 in which a plurality of microstructures 32 are arranged in a square lattice pattern, and Fig. 4 is a partially enlarged view of Fig. 3. The thin lines in Fig. 4 indicate the arrangement direction of the light-receiving elements 52 on the light-receiving surface 50. Note that although Figs. 3 and 4 illustrate each microstructure 32 as being square, this does not limit the shape of the microstructure 32. The same applies to the subsequent figures. 3 and 4, in this arrangement example, a plurality of microstructures 32 are arranged in a square lattice pattern. That is, two primitive translation vectors e1 and e2 of the microstructures 32 are orthogonal to each other and have the same length. The two primitive translation vectors e1 and e2 of the microstructure 32 are parallel to the major axis d1 and the minor axis d2, respectively, of the light-receiving surface 50. This allows the optical function layer 30 to act symmetrically with respect to the major axis d1 and the minor axis d2 of the light-receiving surface 50, thereby suppressing asymmetric image distortion.

[0017] <Arrangement example 2: face-centered rectangular lattice> Fig. 6 is a plan view of the optical function layer 30 in which a plurality of microstructures 32 are arranged in a face-centered rectangular lattice pattern, and Fig. 7 is a partially enlarged view of Fig. 6. The thin lines in Fig. 7 indicate the arrangement direction of the light-receiving elements 52 on the light-receiving surface 50. 6 and 7, in this arrangement example, a plurality of microstructures 32 are arranged in a face-centered rectangular lattice pattern. That is, the two primitive translation vectors e1 and e2 of the microstructures 32 have the same magnitude, but do not form a 90-degree angle. Note that the primitive translation vectors e1 and e2 of the face-centered rectangular lattice are not uniquely chosen. In the microstructure 32, one primitive translation vector e1 is parallel to the major axis d1 or minor axis d2 of the light-receiving surface 50, and the other primitive translation vector e2 is parallel to one of the two diagonal axes d3 and d4. In the examples of FIGS. 6 and 7, one primitive translation vector e1 is parallel to the minor axis d2 of the light-receiving surface 50, and the other primitive translation vector e2 is parallel to the diagonal axis d3. As a result, compared to a square lattice configuration, the microstructures 32 are densely arranged along the diagonal axes d3 and d4 of the light-receiving surface 50, where the largest phase change occurs. Therefore, it is possible to suppress the generation of stray light at the four corners of the light-receiving surface 50 and the decrease in light utilization efficiency. In a face-centered rectangular lattice, the difference vector e3 (= e1 - e2) between two primitive translation vectors e1 and e2 may be included in the primitive translation vectors. In this case, the primitive translation vector e3 is preferably parallel to a diagonal axis d4 different from the diagonal axis d3 parallel to the primitive translation vector e2.

[0018] In this arrangement example, one of the two primitive translation vectors e1 and e2 is inclined at an inclination angle θ of 29.36 degrees relative to the long axis d1 of the light-receiving surface 50. This is the direction of the diagonal axes d3 and d4 of the light-receiving surface 50, which has an aspect ratio of 16:9. In this case, the distance to each of the six neighboring microstructures 32 surrounding a single microstructure 32 is constant by the magnitude of the primitive translation vectors e1 and e2. Therefore, the optical function layer 30 can be fabricated with the same fineness as in the square lattice structure, i.e., the magnitude of the primitive translation vectors e1 and e2. In other words, the microstructures 32 can be densely arranged along the diagonal axes d3 and d4 of the light-receiving surface 50 without changing the fineness from the square lattice structure. The inclination angle θ may be within a range of 30±5 degrees.

[0019] <Arrangement example 3: hexagonal lattice> When the primitive translation vectors e1 and e2 of the arrangement of the microstructures 32 are inclined at an angle of 30 degrees with respect to the long axis d1 of the light-receiving surface 50, the arrangement becomes a hexagonal lattice, which is a special example of a face-centered rectangular lattice. The arrangement of the microstructures 32 in this case is almost the same as that in the case of a face-centered rectangular lattice (FIGS. 6 and 7), and therefore is not shown in the drawings. One of the two primitive translation vectors e1, e2 of the microstructure 32 is parallel to the long axis d1 or the short axis d2 of the light-receiving surface 50. In this case, the same effect as in the case of the face-centered rectangular lattice of Arrangement Example 2 can be obtained. That is, since the optical function layer 30 acts symmetrically with respect to the long axis d1 and the short axis d2 of the light-receiving surface 50, asymmetric image distortion can be suppressed. Furthermore, the microstructures 32 are densely arranged along the diagonal axes d3, d4 of the light-receiving surface 50, where the largest phase change occurs. Therefore, it is possible to suppress the generation of stray light at the four corners of the light-receiving surface 50 and the decrease in light utilization efficiency.

[0020] <Arrangement example 4: rectangular lattice> FIG. 8 is a plan view of the optical function layer 30 in which a plurality of microstructures 32 are arranged in a rectangular lattice pattern. As shown in Fig. 8, in this arrangement example, a plurality of microstructures 32 are arranged in a rectangular lattice pattern. That is, two primitive translation vectors e1 and e2 of the microstructures 32 are orthogonal to each other and have different lengths. In the example of Fig. 8, the microstructures 32 are arranged at high density along the direction of the minor axis d2 of the light-receiving surface 50. The two primitive translation vectors e1 and e2 of the microstructure 32 are parallel to the long axis d1 and short axis d2 of the light-receiving surface 50, respectively. This allows the microstructures 32 to be arranged more densely along the diagonal axes d3 and d4 of the light-receiving surface 50 than when the microstructures 32 are arranged in a square lattice pattern. Therefore, although finer processing may be required than in the case of a square lattice pattern, it is possible to suppress the generation of stray light at the four corners of the light-receiving surface 50 and the decrease in light utilization efficiency. Furthermore, since the optical function layer 30 acts symmetrically with respect to the long axis d1 and short axis d2 of the light-receiving surface 50, asymmetric image distortion can be suppressed.

[0021] <About "Parallel"> The "parallel" relationship between the primitive translation vectors of the microstructure 32 and the axes of the light-receiving surface 50 includes not only perfect parallelism but also substantial parallelism, where the angle between them is within a predetermined range. The angular range that can be considered substantial parallelism is, for example, ±10 degrees, and more preferably ±5 degrees. This point will be explained below. In the example of FIG. 5 , unlike the microstructure 32 of this embodiment, one of the primitive translation vectors (g1) of the microstructure is parallel to one diagonal axis d3 of the light-receiving surface 50 and is inclined at 29.36 degrees with respect to the long axis d1 of the light-receiving surface 50. If this inclination is within ±10 degrees, the area on the light-receiving surface 50 where asymmetric distortion occurs can be reduced. Furthermore, the other primitive translation vector (g2) of the microstructure array is inclined at 31.28 degrees with respect to the other diagonal axis d4 of the light-receiving surface 50. This inclination increases the distance between adjacent microstructures when viewed in the direction of the diagonal axis d4 of the light-receiving surface 50, resulting in stray light and reduced light utilization efficiency. Furthermore, when the microstructures 32 are arranged in a square lattice pattern, the primitive translation vectors e1 and e2 are parallel to the long axis d1 and short axis d2 of the light-receiving surface 50. Consider a light-receiving sensor with a nearly square light-receiving surface and a diagonal axis h3 tilted at 40 degrees with respect to the primitive translation vectors of the microstructures, as shown in Figure 9. In this case, the diagonal axis h3 of the light-receiving surface 50 almost coincides with the 45-degree direction (solid arrow in the upper right corner of the figure) where the distance between adjacent microstructures is greatest. This results in stray light and a decrease in light utilization efficiency. 6, one primitive translation vector e1 is inclined at 29.36 degrees with respect to the long axis d1 of the light-receiving surface 50 and is parallel to one diagonal axis d3 of the light-receiving surface 50. The other primitive translation vector e2 is inclined at 150.64 degrees with respect to the long axis d1 of the light-receiving surface 50 and is parallel to the other diagonal axis d4 of the light-receiving surface 50. In this way, if the primitive translation vectors e1, e2 of the array of the microstructures 32 and the diagonal axes d3, d4 of the light-receiving surface 50 are within the range of ±10 degrees, the direction in which the distance between adjacent microstructures 32 is shortest will approximately coincide with the diagonal axes d3, d4 of the light-receiving surface 50 that require the largest phase change. This makes it possible to suppress a decrease in light utilization efficiency.

[0022] [Distribution of microstructure shapes] FIG. 10A is a diagram showing an example of the distribution of the shapes of the microstructures 32 based on an XY polynomial. FIG. 10B is a diagram showing an example of the distribution of the shapes of the microstructures of a comparative example of the embodiment based on an even-order aspheric surface. In these figures, a graph showing the distribution of the shapes (widths) of the microstructures is shown on the left, and a heat map of the phase profile of the microstructures is shown on the right. The X and Y axes in the figures correspond to, for example, the major axis d1 and minor axis d2 of the light receiving surface 50. The distribution of the shapes of the multiple microstructures 32 on the substrate 3a is defined by predetermined shape parameters. Here, the "shape" of the microstructures 32 includes at least one of the cross-sectional shape, size (width), height, orientation, and material of the microstructures 32. Specifically, the distribution of the shapes (e.g., widths) of the multiple microstructures 32 on the substrate 3a is set based on Zernike polynomials or XY polynomials. More specifically, the distribution of the shapes of the microstructures 32 is set to correspond to a phase profile defined by the Zernike polynomials or XY polynomials. As a result, as shown in FIG. 10A , the shapes of the multiple microstructures 32 are set to be distributed axially symmetrically with respect to each of the major axis d1 and the minor axis d2 of the light-receiving surface 50, with a point on the optical axis Ax as the origin. That is, unlike when the shape distribution is set based on a phase profile defined by an even-order aspheric surface as shown in FIG. 10B , the distribution of the shapes of the microstructures 32 is not point-symmetric with respect to the origin. Therefore, the shapes of the multiple microstructures 32 can be distributed corresponding to the major axis d1 and the minor axis d2 of the light-receiving surface 50. In this way, by applying different forces to light in the directions of the major axis d1 and the minor axis d2, improvement in light utilization efficiency can be expected. In addition, the distribution of the shapes of the multiple microstructures 32 need only be set so as to be axially symmetric with respect to each of the major axis d1 and minor axis d2 of the light receiving surface 50, with a point on the optical axis Ax as the origin, and does not have to be based on Zernike polynomials or XY polynomials.

[0023] [Technical effect of this embodiment] As described above, according to this embodiment, the planar optical function layer 30, which is disposed closer to the object side than the light receiving surface 50, has a plurality of microstructures 32 arranged in a lattice pattern along two primitive translation vectors e1 and e2. At least one of the two primitive translation vectors e1 and e2 is parallel to at least one of the major axis d1 and the minor axis d2 of the light receiving surface 50. That is, the arrangement direction of the microstructures 32 is set to correspond to the arrangement direction of the light-receiving elements 52 on the light-receiving surface 50. This makes it possible to suppress asymmetrical deterioration of characteristics caused by the light-receiving surface 50 being rectangular. Therefore, the multiple microstructures 32 can be suitably arranged with respect to the shape of the light-receiving surface 50 having the multiple light-receiving elements 52.

[0024] Furthermore, according to this embodiment, the multiple microstructures 32 may be arranged in a square lattice pattern, and the two primitive translation vectors e1 and e2 may be parallel to the major axis d1 and minor axis d2 of the light-receiving surface 50, respectively. This makes it possible to suppress asymmetric image distortion.

[0025] Furthermore, according to this embodiment, the multiple microstructures 32 may be arranged in a face-centered rectangular lattice pattern, with one primitive translation vector e1 parallel to the long axis d1 or short axis d2 of the light-receiving surface 50, and the other primitive translation vector e2 parallel to the diagonal axis d3 of the light-receiving surface 50. This allows the fine structures 32 to be densely arranged along the diagonal axes d3 and d4 of the light-receiving surface 50 where the largest phase change occurs, thereby suppressing the occurrence of stray light and the decrease in light utilization efficiency. In this case, one of the primitive translation vectors e2 is inclined at 30±5 degrees with respect to the long axis d1 of the light-receiving surface 50. This allows the microstructures 32 to be densely arranged along the diagonal axis d3 of the light-receiving surface 50 without changing the fineness from that in the square lattice case.

[0026] Furthermore, according to this embodiment, the multiple microstructures 32 may be arranged in a hexagonal lattice pattern, and one of the two primitive translation vectors e1 and e2 may be parallel to the major axis d1 or the minor axis d2 of the light receiving surface 50. This makes it possible to suppress asymmetric image distortion.

[0027] Furthermore, according to this embodiment, the multiple microstructures 32 are arranged in a rectangular lattice pattern, and the two primitive translation vectors e1 and e2 are parallel to the major axis d1 and minor axis d2 of the light-receiving surface 50, respectively. This allows the microstructures 32 to be arranged at a higher density along the diagonal axis d3 of the light-receiving surface 50 than in the case of a square lattice pattern.

[0028] Furthermore, according to this embodiment, the shapes of the multiple microstructures 32 are distributed symmetrically with respect to each of the major axis d1 and the minor axis d2 of the light receiving surface 50, with a point on the optical axis Ax as the origin. This allows the shapes of the multiple microstructures 32 to be suitably distributed in accordance with the long axis d1 and short axis d2 of the light receiving surface 50.

[0029] Furthermore, according to this embodiment, the distribution of the shapes of the plurality of microstructures 32 on the substrate 3a is set based on Zernike polynomials or XY polynomials. This allows the axisymmetric distribution of the microstructures 32 with respect to each of the major axis d1 and the minor axis d2 of the light receiving surface 50 to be suitably controlled.

[0030] [others] The above describes one embodiment of the present invention, but embodiments to which the present invention can be applied are not limited to the above-described embodiment and its variations, and can be modified as appropriate within the scope of the spirit of the present invention.

[0031] For example, in the above embodiment, the light receiving optical system 1 is exemplified as including the lens 2, the first parallel plate 3, the second parallel plate 4, and the light receiving sensor 5. However, the present invention can be widely applied to optical elements and light receiving optical systems that include an optical function layer (optical function surface) on which a plurality of microstructures are arranged, and is not particularly limited to optical elements other than those that include an optical function layer. For example, as shown in FIG. 11, a light-receiving optical system 1A may be configured such that an optical functional layer 30 is provided on a cover glass 3A (optical element) that protects a light-receiving sensor 5. The specific configuration of the optical system 2A, which is disposed closer to the object than the cover glass 3A, is not particularly limited. In this case, the cover glass 3A may be, for example, a metalens capable of correcting aberrations. This allows for improved resolution characteristics while minimizing costs and changes in the optical system 2A. [Explanation of symbols]

[0032] 1, 1A light receiving optical system 3. First parallel plate (optical element) 3a Base material 3A Cover Glass (Optical Element) 5 Light receiving sensor 30 Optical functional layer 32 Microstructure 50 Photosensitive surface 52 light-receiving elements d1 major axis d2 minor axis d3 Angle axis e1, e2 are basically parallel to each other Ax optical axis θ tilt angle

Claims

1. It is located closer to the object than the light receiving surface, An optical element comprising a substrate and a planar optical functional layer including a plurality of microstructures arranged on the substrate, the light receiving surface is formed in a rectangular shape having a major axis and a minor axis, and a plurality of light receiving elements are arranged in a lattice pattern along the major axis and the minor axis; The plurality of microstructures include: are arranged in a grid along two primitive translation vectors, At least one of the two primitive translation vectors is parallel to at least one of the major axis and the minor axis of the light receiving surface. Optical elements.

2. the plurality of microstructures are arranged in a square lattice pattern, and the two primitive translation vectors are parallel to the major axis and the minor axis of the light-receiving surface, respectively; The optical element according to claim 1 .

3. the plurality of microstructures are arranged in a face-centered rectangular lattice pattern, one of the two primitive translation vectors is parallel to a major axis or a minor axis of the light-receiving surface, and the other of the two primitive translation vectors is parallel to a diagonal axis of the light-receiving surface; The optical element according to claim 1 .

4. the other of the two primitive translation vectors is inclined at 30±5 degrees with respect to the major axis of the light receiving surface; The optical element according to claim 3 .

5. the plurality of microstructures are arranged in a hexagonal lattice pattern, and one of the two primitive translation vectors is parallel to a major axis or a minor axis of the light-receiving surface; The optical element according to claim 1 .

6. the plurality of microstructures are arranged in a rectangular lattice pattern, and the two primitive translation vectors are parallel to the major axis and the minor axis of the light-receiving surface, respectively; The optical element according to claim 1 .

7. the plurality of microstructures each have a size equal to or less than a main design wavelength of the optical function layer, and a shape distribution on the substrate is defined by predetermined shape parameters; the shapes of the plurality of microstructures are distributed symmetrically with respect to each of the major axis and the minor axis of the light-receiving surface, with a point on the optical axis as the origin; The optical element according to claim 2 .

8. The plurality of microstructures have a shape distribution on the substrate set based on a Zernike polynomial or an XY polynomial. The optical element according to claim 7 .

9. a light receiving surface; a planar optical function layer disposed on the object side of the light receiving surface and including a plurality of microstructures arranged on a substrate; A light receiving optical system comprising: the light receiving surface is formed in a rectangular shape having a major axis and a minor axis, and a plurality of light receiving elements are arranged in a lattice pattern along the major axis and the minor axis; The plurality of microstructures include: are arranged in a grid along two primitive translation vectors, At least one of the two primitive translation vectors is parallel to at least one of the major axis and the minor axis of the light receiving surface. Light receiving optical system.

10. a cover glass disposed on the object side of the light receiving surface, The optical functional layer is formed on the surface of the cover glass. The light receiving optical system according to claim 9 .

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