Optical element, optical system, lens device, and imaging apparatus

Abstract

To provide an optical element that has a fine rugged structure with high stability.SOLUTION: An optical element (100) has a substrate (1), a ground layer (22) formed on the substrate, and a plurality of structures (21) including at least either one of concave elements or convex elements. The ground layer is arranged in a first area in a first ring zone and is not arranged in a second area in the first ring zone. The plurality of structures includes a plurality of first structures (215) arranged on the ground layer in the first area, and a plurality of second structures (216) arranged on the substrate in the second area. The plurality of first structures is different in width from each other. The plurality of second structures is different in width from each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical element, an optical system, a lens device, and an imaging device. [Background technology]

[0002] Conventionally, in order to miniaturize optical systems used in imaging devices, etc., optical elements (metalenses) that have a fine uneven structure formed on the surface of a substrate and have a light collecting or diverging effect by utilizing diffraction have been known. Patent Document 1 discloses a metalens used as a lens for terahertz waves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-99400 Summary of the Invention [Problem to be solved by the invention]

[0004] In an optical element having a fine concave-convex structure, in order to increase the diffraction efficiency (the ratio of the amount of light directed toward a specific diffraction angle to the amount of incident light), it is preferable to make the repeating period (pitch) of the fine concave-convex structure small relative to the wavelength of the incident light. It is also preferable to change the shape of the fine concave-convex structure for each pitch to realize a smooth phase distribution.

[0005] However, when the pitch is reduced, the aspect ratio of the fine concave-convex structure increases, which makes it difficult to form the fine concave-convex structure and to maintain the shape of the fine concave-convex structure, and the fine concave-convex structure is deformed by a slight load, temperature, pressure, or the like.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an optical element having a highly stable fine uneven structure. [Means for solving the problem]

[0007] An optical element as one aspect of the present invention has a substrate, an undercoat layer formed on the substrate, and a plurality of structures including at least one of concave elements or convex elements, wherein the undercoat layer is arranged in a first region of a first annular zone and is not arranged in a second region of the first zone, and the plurality of structures include a plurality of first structures arranged on the undercoat layer in the first region and a plurality of second structures arranged on the substrate in the second region, wherein each of the plurality of first structures has a width different from one another, and each of the plurality of second structures has a width different from one another.

[0008] Other objects and features of the present invention are illustrated in the following examples. Effect of the Invention

[0009] According to the present invention, it is possible to provide an optical element having a highly stable fine uneven structure. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram illustrating the configuration of an optical element in each embodiment. [Diagram 2] FIG. 13 is a diagram illustrating the configuration of an optical element according to a comparative example. [Diagram 3] 5A and 5B are diagrams showing the relationship between the shape of the concave and convex elements of the optical element and the amount of phase modulation in each example. [Figure 4] 13 is a diagram showing the relationship between the shape of the concave-convex elements of an optical element and the amount of phase modulation in a comparative example. FIG. [Diagram 5] 5A to 5C are explanatory diagrams of a method for manufacturing an optical element in each embodiment. [Figure 6] FIG. 4 is an explanatory diagram of an offset layer in each embodiment. [Figure 7] 5A to 5C are diagrams illustrating the modulation amount of the normalized phase with respect to the radial direction of the optical element in each embodiment. [Figure 8] 4A to 4C are diagrams illustrating the width of concave-convex elements in the radial direction of optical elements in each of the examples and comparative examples. [Figure 9] FIG. 1 is an explanatory diagram of element packing rates in each embodiment. [Figure 10(a)] FIG. 11 is an explanatory diagram of offset of the underlayer in each example. [Figure 10(b)] FIG. 11 is an explanatory diagram of offset of the underlayer in each example. [Figure 10(c)] FIG. 11 is an explanatory diagram of offset of the underlayer in each example. [Figure 10(d)] FIG. 11 is an explanatory diagram of offset of the underlayer in each example. [Figure 11] 4A to 4C are explanatory diagrams of shapes of concave and convex elements in each embodiment. [Figure 12] FIG. 23 is a diagram showing the configuration of an optical element in Example 16. [Figure 13] FIG. 23 is a diagram showing the configuration of an optical element in Example 19. [Figure 14] FIG. 2 is an explanatory diagram of an optical system including an optical element in each embodiment. [Figure 15] FIG. 2 is an explanatory diagram of an imaging device including the optical element in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] First, the optical element 100 in each embodiment will be described with reference to Figs. 1(a) to (c). Figs. 1(a) to (c) are configuration diagrams of the optical element 100. Fig. 1(a) shows an enlarged cross-sectional view of the optical element 100 (in the xz plane) as viewed from the y-axis direction, and Fig. 1(b) shows an enlarged top view of the optical element 100 (in the xy plane) as viewed from the z-axis direction (optical axis direction). Fig. 1(c) shows an overall top view of the optical element 100 (in the xy plane) as viewed from the z-axis direction (optical axis direction). In each embodiment, the optical axis direction of the optical element 100 and the thickness direction of the substrate 1 each coincide with the z-axis direction.

[0013] The optical element 100 of each embodiment has a substrate 1 and a concave-convex structure (pillars) 2 formed on the substrate 1. The concave-convex structure 2 has a plurality of concave-convex elements (a plurality of structures) 21 including at least one of concave elements or convex elements periodically arranged in the radial direction (e.g., the x-axis direction and the y-axis direction) of the substrate 1 (optical element 100), and an underlayer 22 having an approximately constant thickness in the thickness direction (z-axis direction) of the substrate 1. Note that "approximately constant" means that the underlayer 20 is preferably as constant in thickness as possible, but does not have to be strictly constant in thickness, for example, in the case where manufacturing errors are included. The thickness of the underlayer 22 is within a range that satisfies the following conditional formula, for example.

[0014] When the maximum and minimum values ​​of the thickness of the underlayer 22 in the region 1 are A and B, respectively, the following conditional formula (1) is satisfied.

[0015] 1.00≦ It is preferable that the numerical range of condition (1) satisfies the following condition (1a):

[0016] 1.00≦ It is more preferable that the numerical range of conditional expression (1) satisfies the following conditional expression (1b).

[0017] 1.00≦A / B<1.15 …(1b) It is more preferable that the numerical range of condition (1) satisfies the following condition (1c):

[0018] 1.00≦A / B<1.10 …(1c) It is more preferable that the numerical range of condition (1) satisfies the following condition (1d):

[0019] 1.00≦A / B<1.05 …(1d) ​​Forming a periodic phase difference (zone) in the radial direction of the substrate 1 provides a focusing or diverging effect to the incident light. The optical element 100 has a plurality of zones including a first zone (i-th zone) and a second zone ((i+1)-th zone) arranged along the radial direction so as to extend in the circumferential direction with respect to the center of the optical element 100. Each of the plurality of zones has a region 1 (first region) and a region 2 (second region) arranged along the radial direction of the optical element 100. In each embodiment, it is sufficient that at least one of the plurality of zones has the region 1 and the region 2, but it is preferable that the plurality of zones have the region 1 and the region 2, and it is more preferable that all of the zones have the region 1 and the region 2.

[0020] The multiple concave-convex elements (multiple structures) 21 have multiple first structures 215 arranged in region 1 and multiple second structures 216 arranged in region 2. In region 1, the multiple first structures 215 are formed on the substrate 1 via an underlayer 22. In region 2, the multiple second structures 216 are formed directly on the substrate 1 (without an underlayer). The multiple first structures 215 have mutually different widths in the radial direction. Similarly, the multiple second structures 216 have mutually different widths in the radial direction.

[0021] The substrate 1 is a transparent flat plate made of synthetic quartz. The substrate 1 may be a plane mirror that reflects incident light, or may be a curved surface having any curvature. The material of the substrate 1 is not limited to synthetic quartz, and may be inorganic glass, organic materials such as plastics, ceramics, metals, etc. The uneven structure 2 is formed on the surface of the substrate 1, and imparts a phase difference to light passing through the uneven structure 2, thereby providing a focusing or diverging effect. In each embodiment, a phase distribution is formed by annular zones in which a phase difference of 2nπ (n=1, 2, . . . is an integer that represents the design diffraction order or the diffraction order) is repeated periodically in a concentric manner, thereby obtaining a focusing effect approximately equivalent to that of a diffractive optical element.

[0022] The concavo-convex structure 2 has a concavo-convex element 21 and a base layer 22. The concavo-convex element 21 consists of periodically arranged concave or convex elements. In each embodiment, the concavo-convex element 21 consists of convex cylindrical elements of a dielectric material Si3N4. Note that the shape of the concavo-convex element 21 is not limited to convex cylindrical elements, and may be polygonal columns, polygonal pyramids, cones, any concave-shaped elements, or a combination of these elements. Also, the material of the concavo-convex element 21 may be TiO2, GaN, GaP, GaAs, Si, SiC, Al2O3, SiO2, etc.

[0023] The concavo-convex element 21 has a convex cylindrical element arranged at the center of a unit partition segment 11 that is divided into a square shape in the radial direction of the substrate 1. Note that by making the width (pitch) of the segment 11 smaller than the wavelength of the incident light, the light is phase-modulated according to the effective refractive index obtained from the element filling ratio in the unit partition (segment) regardless of the shape of the concavo-convex element 21. For example, when the incident light is in the visible light range (400 - 700 nm), the pitch (array period) P [nm] is preferably less than 400 nm, and it is more preferable to make the pitch P even smaller because unnecessary diffracted light can be suppressed. In the i-th zone (i = 1, 2,...), there are a region 1 having a substantially flat base layer 22 disposed between a plurality of concavo-convex elements 21 and the substrate 1, and a region 2 without the base layer 22.

[0024] The base layer 22 has a substantially constant thickness in the thickness direction of the substrate 1, and in each embodiment, it consists of the same Si3N4 as the material of the concavo-convex element 21. The regions 1 and 2 in the i-th zone each have a plurality of concavo-convex elements 21, and by making the widths in the radial direction of the substrate 1 different in shape, a phase distribution of 2nπ is formed within the zone. In the direction perpendicular to the optical axis, let the radii of the regions 1 and 2 of the i-th zone from the optical axis be RLi and RHi, respectively. As can be seen from FIG. 1(c), the regions 1 and 2 are alternately configured concentrically in the direction perpendicular to the optical axis (z-axis) such that RLi < RHi.

[0025] Next, as a comparative example, an optical element 101 without a base layer 22 will be described with reference to FIG. 2. FIG. 2 is a configuration diagram of the optical element 101 as a comparative example. In order to form a 2nπ phase distribution within the annular zone, the width (diameter) of the convex cylindrical element, which is the convex-convex element 21, is changed to change the element packing rate of the convex-convex element 21 within the segment. That is, the element packing rate decreases from the element with a large diameter to the element with a small diameter of the convex cylindrical element, forming a desired phase distribution. In the optical element 101 of FIG. 2, the element packing rate is adjusted only by the diameter of the convex cylindrical element, so the diameter is changed greatly. Therefore, the minimum diameter of the convex cylindrical element tends to be small, and the aspect ratio (the ratio of the height to the width of the convex-convex element 21 (height / width)) tends to be large. In the case of an element with a large aspect ratio and relatively elongated, the shape may be deformed, tilted, or peeled off when a load is applied due to contact or vibration, or when an external factor such as temperature or pressure changes. Therefore, in each embodiment, a base layer 22 is provided within the annular zone to increase the amount of phase modulation in region 2, thereby reducing the amount of change in width of the unevenness elements 21, thereby forming an unevenness structure 2 without increasing the aspect ratio.

[0026] FIG. 3 is a diagram showing the relationship between the shape of the concave-convex elements 21 of the optical element 100 in each embodiment and the amount of phase modulation, and relates to the diameter of the convex cylindrical elements, which are the concave-convex elements 21, and the amount of phase modulation. In FIG. 3, the horizontal axis shows the diameter W of the convex cylindrical elements (normalized diameter normalized by the pitch P of the segments), and the vertical axis shows the normalized phase normalized by 2π. When the normalized phase is in the range of 0 to 0.54, the normalized diameter of the convex cylindrical elements in the region 2 without the underlayer 22 is changed from 0.552 to 0.790. When the normalized phase is in the range of 0.54 to 1, the normalized diameter of the convex cylindrical elements in the region 1 having the underlayer 22 is changed from 0.253 to 0.790. As a result, a phase modulation amount of normalized phase 0 to 1 is obtained, and the maximum value A1 of the aspect ratio of the concave-convex elements 21 in the region 1 is 7.2, and the maximum value A2 of the aspect ratio of the concave-convex elements 21 in the region 2 is 6.6.

[0027] FIG. 4 is a diagram showing the relationship between the shape of the concave-convex elements 21 of the optical element 101 as a comparative example and the phase modulation amount, and relates to the diameter of the convex cylindrical elements and the phase modulation amount in the optical element 101 without the underlayer 22. In FIG. 4, the horizontal axis and the vertical axis are the same as those in FIG. 3. In FIG. 4, in order to obtain a phase modulation amount of normalized phase 0 to 1, it is necessary to change the normalized diameter from 0.177 to 0.823, and the aspect ratio is 20.7 at the maximum, which is larger than the aspect ratio in the case where the underlayer is provided. This shows that the aspect ratio of the concave-convex elements 21 can be suppressed by providing the underlayer 22.

[0028] Next, a method for manufacturing the optical element 100 of each embodiment will be described with reference to Figs. 5(a) to (c). The optical element 100 can be manufactured by lithography. Figs. 5(a) to (c) are explanatory diagrams of the method for manufacturing the optical element 100, showing the steps of manufacturing the optical element 100 by nanoimprint lithography. Fig. 5(a) shows a mold 31, which has a shape that is an inversion of the concave-convex shape of the concave-convex elements 21 formed by an electron beam, a laser, or the like. As shown in Fig. 5(b), a resist material 32 is applied to a film 33 deposited on a substrate 1, the mold 31 is pressed against the film 33, and ultraviolet rays or the like are irradiated to form a shape in which the concave-convex shape of the mold 31 is inverted in the resist material 32. Thereafter, as shown in Fig. 5(c), the mold 31 is peeled off, and development is performed so that the concave-convex shape of the resist material 32 is transferred to the film 33, thereby forming the concave-convex structure 2 on the substrate 1 of the optical element 100. In each embodiment, the method for manufacturing the concave-convex structure 2 is not limited to nanoimprint lithography, and other methods such as directly forming the concave-convex structure 2 with an electron beam, a laser, or the like may be used.

[0029] Fig. 6 is an explanatory diagram of the offset layer 34 in each embodiment. As shown in Fig. 6, instead of the configuration in which the concave-convex structure 2 is formed directly on the substrate 1 as in Fig. 5(c), an offset layer 34 may be provided so as to straddle both the region 1 and the region 2 as in Fig. 6. The substrate 1 may include the offset layer 34.

[0030] In each embodiment, the base layer 22 may be made of the same material as the concave-convex elements 21. As shown in Fig. 5(b), it is relatively easy to prepare a material with a uniform thickness, such as the film 33. For this reason, when the base layer 22 and the concave-convex structure 2 are formed based on the film 33, it is preferable that the base layer 22 is made of the same material as the concave-convex elements 21.

[0031] In each embodiment, when the height of the concave-convex elements 21 in region 1 (the height of each of the multiple first structures 215) is H1 and the height of the concave-convex elements 21 in region 2 (the height of each of the multiple second structures 216) is H2, it is preferable to satisfy the following conditional formula (2). By satisfying conditional formula (2), the manufacturing process is simplified and the formation of the concave-convex elements 21 becomes easier.

[0032] 0.20≦H1 / H2≦0.90 …(2) Conditional formula (2) relates to the shape of the concave-convex elements 21. Since the base layer 22 is disposed in the region 1, the amount of phase modulation can be made large even if the height H1 of the concave-convex elements 21 in the region 1 is made lower than that in the region 2. Therefore, it is possible to realize a shape in which the aspect ratio of the concave-convex elements 21 in the region 1 in particular is reduced.

[0033] If the lower limit of conditional formula (2) is not reached, the height H1 of the concave-convex elements 21 in region 1 becomes relatively low, and the phase modulation amount cannot be increased when the width of the concave-convex elements 21 in region 1 is changed. In this case, in order to obtain the desired phase modulation amount, the width of the concave-convex elements 21 in region 1 must be changed relatively largely, and the effect of reducing the aspect ratio in region 1 cannot be obtained. In each embodiment, it is more preferable that the lower limit of conditional formula (2) is set to 0.25, 0.30, 0.32, 0.34, 0.35, 0.36, 0.38, or 0.40 instead of 0.20.

[0034] On the other hand, when the upper limit value of conditional formula (2) is exceeded, the height H2 of the concave-convex elements 21 in region 2 becomes relatively low, and the phase modulation amount when the width of the concave-convex elements 21 in region 2 is changed cannot be made large. In this case, in order to obtain a desired phase modulation amount, it is necessary to change the width of the concave-convex elements 21 in region 2 relatively largely, so that the effect of reducing the aspect ratio in region 2 cannot be obtained. It is more preferable that the upper limit value of conditional formula (2) is set to 0.88, 0.86, 0.84, 0.82, 0.80, 0.78, 0.76, 0.74, 0.72, 0.70, 0.69, 0.68, 0.67, 0.66, or 0.65 instead of 0.90.

[0035] In each embodiment, the height H1 of each of the first structures 215 does not need to be the same, and may be different from each other. The same applies to the height H2 of the second structures 216.

[0036] In each embodiment, when the height of the underlayer 22 in the region 1 is HL, it is preferable to satisfy the following conditional formula (3). Note that the height HL is, for example, the average height of the underlayer 22 in the region 1. It is more preferable that the height HL satisfies the conditional formula (3) whether it is the minimum height or the maximum height.

[0037] 0.80≦(H1+HL) / H2≦1.20 …(3) Conditional formula (3) relates to the height of the unevenness elements 21 and the underlayer 22. By satisfying conditional formula (3), the tip position of the unevenness elements 21 in region 1 and the tip position of the unevenness elements 21 in region 2 with respect to the substrate 1 become substantially equal. Therefore, when the unevenness structure 2 is formed from a film of uniform thickness, a highly stable unevenness structure can be realized with a simple process. If the lower limit of conditional formula (3) is exceeded, the height H2 of the unevenness elements 21 in region 2 becomes relatively high, and the effect of reducing the aspect ratio in region 2 cannot be obtained. In addition, the difference in the tip positions of the unevenness elements 21 between region 1 and region 2 becomes large. Therefore, when the unevenness structure 2 is formed from a film of uniform thickness, it is necessary to include a process of providing a difference in height. On the other hand, if the upper limit of conditional formula (3) is exceeded, the height H1 of the unevenness elements 21 in region 1 becomes relatively high, and the effect of reducing the aspect ratio in region 1 cannot be obtained.

[0038] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expression (3) be set to 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.95, 0.96, 0.97, 0.98, or 0.99, instead of 0.80, and the upper limit of conditional expression (3) be set to 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.05, 1.04, 1.03, 1.02, or 1.01, instead of 1.20.

[0039] In addition, when the heights of the unevenness elements 21 and the underlayer 22 are slightly wavy in the radial direction of the substrate 1, it is preferable that the average value of the heights of the unevenness elements 21 and the underlayer 22 within the annular zone satisfies conditional formula (3). Moreover, in areas where the effects of each embodiment are not expected, such as unintended local unevenness due to manufacturing errors or structures outside the effective light beam area, it is not necessary to satisfy conditional formula (3).

[0040] With respect to light traveling in the thickness direction of the substrate 1, it is preferable that the amount of phase modulation (amount of phase delay) by the unevenness structure 2 is greater in region 1 than in region 2. FIG. 7 is an explanatory diagram of the amount of modulation of the normalized phase with respect to the radial direction of the substrate 1. In FIG. 7, the vertical axis indicates the normalized phase, and the horizontal axis indicates the radial position. FIG. 8 is an explanatory diagram of the unevenness element width (e.g., the diameter of a convex cylindrical element, etc.). In FIG. 8, the vertical axis indicates the unevenness element width, and the horizontal axis indicates the radial position. In FIG. 8, the configuration of the optical element 100 of each embodiment is shown by a solid line, and the optical element 101 of the comparative example without the underlayer 22 is shown by a dotted line.

[0041] In each embodiment, by disposing the underlayer 22 in region 1, the amount of phase modulation can be made larger than in region 2. Also, in each embodiment, by changing the uneven element width in each region, the amount of change in the uneven element width can be made smaller than in the comparative example, thereby suppressing the aspect ratio of the uneven elements 21 in region 1 and region 2. When the phase modulation by the uneven structure 2 in region 1 is smaller than that in region 2, the amount of change in the uneven element width in regions 1 and 2 must be configured relatively larger to obtain a desired phase distribution, and the aspect ratio suppression effect cannot be obtained.

[0042] Next, the element packing ratio will be described with reference to Figures 9(a) and 9(b). Figures 9(a) and 9(b) are explanatory diagrams of the element packing ratio, with Figure 9(a) showing the element packing ratio in region 1 where underlayer 22 is arranged, and Figure 9(b) showing the element packing ratio in region 2 where underlayer 22 is not present.

[0043] The element packing ratio is the ratio of the volume occupied by the concave-convex structure 2 per segment. The element packing ratio of the surface of the substrate 1 in region 1 and region 2 and the range from the surface position of the substrate 1 to the position of height HL is the ratio of the base layer 22 or the concave-convex elements 21 to the volume Vs of the bottom surface P×P and height HL, as shown in Figures 9(a) and (b). The element packing ratio of the range from the position of height HL to the tip position of the concave-convex elements 21 in region 1 and region 2 is the ratio of the base layer 22 or the concave-convex elements 21 to the volume Va of the bottom surface P×P and height H1, as shown in Figures 9(a) and (b).

[0044] Here, the maximum value of the element packing rate from the surface position of the substrate 1 to the position of height HL in region 1 is defined as V1s, and the maximum value of the element packing rate from the surface position of the substrate 1 to the position of height HL in region 2 is defined as V2s. Furthermore, the maximum value of the element packing rate from the position of height HL to the tip position of the concave-convex structure 2 (structure) in region 1 is defined as V1a, and the maximum value of the element packing rate from the position of height HL to the tip position of the concave-convex structure 2 (structure) in each of region 1 and region 2 is defined as V2a. In this case, it is preferable to satisfy at least one of the following conditional expressions (4) to (6).

[0045] 0.50≦V1s≦1.00 …(4) 0.80≦V2a / V2s≦1.20 …(5) 0.20≦V1a / V1s≦0.80 …(6) Conditional formula (4) relates to the element packing rate of the underlayer 22 in region 1. If the lower limit of conditional formula (4) is exceeded, the desired phase modulation amount cannot be obtained unless the uneven element widths in region 1 and region 2 are changed relatively significantly, and the aspect ratio cannot be suppressed. From the definition of the element packing rate, V1s is maximized when it is equal to Vs, so it does not exceed the upper limit of conditional formula (4). It is more preferable that the lower limit of conditional formula (4) is set to 0.54, 0.58, 0.62, 0.64, 0.68, 0.72, 0.76, 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, or 0.96, instead of 0.50.

[0046] Conditional formula (5) relates to the element packing rate of region 2. If the lower limit of conditional formula (5) is exceeded, V2s becomes relatively large, and the desired phase modulation amount cannot be obtained unless the width of the uneven elements of region 2 is significantly changed, and the aspect ratio suppression effect cannot be obtained. On the other hand, if the upper limit of conditional formula (5) is exceeded, V2a becomes relatively large, and the desired phase modulation amount cannot be obtained unless the width of the uneven elements 21 of region 1 is significantly changed, and the aspect ratio suppression effect cannot be obtained. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (5) is set to 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, or 0.96 instead of 0.80. Moreover, it is more preferable that the upper limit value of conditional expression (5) be set to 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04 or 1.02, instead of 1.20.

[0047] Conditional formula (6) relates to the element packing rate of the region 1. If the lower limit of conditional formula (6) is not satisfied, V1s becomes relatively large, and the desired phase modulation amount cannot be obtained unless the width of the uneven elements 21 in the region 2 is significantly changed, and the aspect ratio suppression effect cannot be obtained. On the other hand, if the upper limit of conditional formula (6) is exceeded, V1a becomes relatively large, and the desired phase modulation amount cannot be obtained unless the width of the uneven elements 21 in the region 1 is significantly changed, and the aspect ratio suppression effect cannot be obtained. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (6) is set to 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.30, instead of 0.20. Moreover, it is more preferable that the upper limit value of conditional expression (6) is set to 0.78, 0.76, 0.74, 0.72, 0.70, 0.68, 0.66, or 0.65, instead of 0.80.

[0048] In each embodiment, the maximum width (maximum diameter of the cylinders among the plurality of first structures) of the concave-convex elements 21 in region 1 is defined as Wmax1, and the minimum width (minimum diameter of the cylinders) is defined as Wmin1. Also, the maximum width (maximum diameter of the cylinders among the plurality of second structures) of the concave-convex elements 21 in region 2 is defined as Wmax2, and the minimum width (minimum diameter of the cylinders) is defined as Wmin2. In this case, it is preferable to satisfy the following conditional expressions (7) and (8).

[0049] 1.05≦Wmax1 / Wmin1≦6.00 …(7) 1.05≦Wmax2 / Wmin2≦6.00 …(8) Conditional expressions (7) and (8) relate to the shapes of the concave-convex elements 21 in region 1 and region 2, respectively. If the lower limit of each of conditional expressions (7) and (8) is not satisfied, a slight change in the concave-convex element width will relatively increase the phase modulation, and the influence of manufacturing variations when forming the concave-convex structure 2 will increase, making manufacturing difficult. On the other hand, if the upper limit of each of conditional expressions (7) and (8) is exceeded, the amount of change in the concave-convex element width will increase, making it impossible to obtain the effect of suppressing the aspect ratio.

[0050] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expression (7) be set to 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, or 1.45 instead of 1.05, and it is more preferable that the upper limit of conditional expression (7) be set to 5.50, 5.00, 4.50, 4.00, or 3.50 instead of 6.00.

[0051] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expression (8) be set to 1.06, 1.08, 1.12, 1.16, 1.20, 1.24, 1.26, 1.28, 1.30, 1.32, 1.34, or 1.36 instead of 1.05, and the upper limit of conditional expression (8) be set to 5.50, 5.00, 4.50, 4.00, 3.50, 3.00, 2.50, 2.00, 1.80, 1.70, or 1.60 instead of 6.00.

[0052] In each embodiment, the concave-convex elements 21 in the region 1 and the region 2 preferably have a phase modulation that monotonically increases or decreases along the radial direction of the substrate 1 within the annular zone. That is, in each of the multiple annular zones, the multiple first structures 215 and the multiple second structures 216 are configured so that the phase of the light passing through the concave-convex structure 2 monotonically increases or decreases in the radial direction. If the phase modulation increases or decreases discretely, it is necessary to change the concave-convex element width relatively greatly, and the aspect ratio suppression effect cannot be obtained. In the case where the optical element 100 of each embodiment has a light-collecting effect when a plane wave is incident on the optical element 100 in the thickness direction of the substrate 1, the phase delay of the phase modulation monotonically decreases in the radial direction from the inside to the outer periphery of the substrate 1 within the annular zone. In addition, in the case where the optical element 100 has a diverging effect, the phase delay of the phase modulation monotonically increases in the radial direction from the inside to the outer periphery of the substrate within the annular zone.

[0053] In each embodiment, when the maximum value of the aspect ratio of the concave-convex elements 21 in the region 1 is A1 and the maximum value of the aspect ratio of the concave-convex elements 21 in the region 2 is A2, it is preferable to satisfy the following conditional formula (9).

[0054] 0.35≦A1 / A2≦2.00 …(9) Condition (9) relates to the shape of the concave-convex element 21. If the lower limit of condition (9) is exceeded, the amount of change in the concave-convex element width in region 2 increases, making it impossible to obtain the effect of suppressing the aspect ratio in region 2. On the other hand, if the upper limit of condition (9) is exceeded, the amount of change in the concave-convex element width in region 1 increases, making it impossible to obtain the effect of suppressing the aspect ratio in region 1.

[0055] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expression (9) be set to 0.36, 0.38, 0.40, 0.42, 0.43, or 0.44 instead of 0.35, and the upper limit of conditional expression (9) be set to 1.90, 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.25, or 1.20 instead of 2.00.

[0056] In each embodiment, it is preferable to satisfy the following conditional expressions (10) and (11).

[0057] 1.50≦A1≦20.00 …(10) 1.50≦A2≦20.00 …(11) Conditional expressions (10) and (11) relate to the shapes of the concave-convex elements 21 in region 1 and region 2. When the lower limit of each of conditional expressions (10) and (11) is not satisfied, a slight change in the width of the concave-convex elements results in relatively large phase modulation, and the influence of manufacturing variations when forming the concave-convex structure 2 becomes large, making manufacturing difficult. On the other hand, when the upper limit of each of conditional expressions (10) and (11) is exceeded, the aspect ratio becomes large, making the structure more susceptible to collapse due to external factors.

[0058] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expressions (10) and (11) be set to 2.00, 3.00, 3.40, 3.80, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00, or 5.20, instead of 1.50, and the upper limit of conditional expressions (10) and (11) be set to 18.00, 16.00, 15.00, 14.00, 13.0, 12.0, 11.0, 10.0, 9.0, or 8.0, instead of 20.00.

[0059] In the optical element 100 of each embodiment, the phase distribution depends on the reference wavelength λ 0. In this case, it is preferable to satisfy the following conditional expression (12).

[0060] 0.50≦H2 / λ0≦4.00 …(12) Conditional expression (12) relates to the shape of the concave-convex element 2. With regard to the phase distribution, the annular zones are determined based on the phase relative to the reference wavelength λ0. If the lower limit of conditional expression (12) is exceeded, the amount of change in the concave-convex element width increases, making it impossible to obtain the effect of suppressing the aspect ratio in region 2. On the other hand, if the upper limit of conditional expression (12) is exceeded, the aspect ratio becomes large, making the structure more susceptible to collapse due to external factors.

[0061] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expression (12) be set to 0.60, 0.70, 0.80, 0.90, 0.95, or 1.00, instead of 0.50, and the upper limit of conditional expression (12) be set to 3.80, 3.60, 3.40, 3.20, 3.00, 2.80, 2.60, 2.40, 2.20, or 2.00, instead of 4.00.

[0062] It is preferable that the optical element 100 in each embodiment satisfies the following conditional expression (13).

[0063] 0.15≦Wmin1 / Wmin2≦4.00 …(13) Condition (13) relates to the shape of the concave-convex element 21. When the lower limit of condition (13) is exceeded, the concave-convex element width in region 1 becomes relatively small, making it difficult to obtain the effect of suppressing the aspect ratio in region 1. On the other hand, when the upper limit of condition (13) is exceeded, the concave-convex element width in region 2 becomes relatively small, making it difficult to obtain the effect of suppressing the aspect ratio in region 2.

[0064] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expression (13) be set to 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, or 0.29 instead of 0.15, and the upper limit of conditional expression (13) be set to 3.75, 3.50, 3.25, 3.00, 2.75, 2.50, or 2.25 instead of 4.00.

[0065] Furthermore, it is preferable that the optical element of the present invention satisfies the following conditional expression (14).

[0066] 0.70≦Wmax1 / Wmax2≦1.40 …(14) Conditional formula (14) relates to the shape of the concave-convex elements 21. When the lower limit of conditional formula (14) is exceeded, the maximum width of the concave-convex elements 21 in region 1 becomes relatively small. Therefore, in order to change the specified normalized phase in region 1, it is necessary to reduce the minimum width of the concave-convex elements 21, making it difficult to obtain the effect of suppressing the aspect ratio in region 2. On the other hand, when the upper limit of conditional formula (14) is exceeded, the maximum width of the concave-convex elements 21 in region 2 becomes relatively small. Therefore, in order to change the specified normalized phase in region 2, it is necessary to reduce the minimum width of the concave-convex elements 21, making it difficult to obtain the effect of suppressing the aspect ratio in region 2.

[0067] In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional expression (14) be set to 0.74, 0.78, 0.82, 0.84, 0.85, 0.86, or 0.87 instead of 0.70, and the upper limit of conditional expression (14) be set to 1.36, 1.32, 1.30, 1.28, 1.26, 1.24, 1.22, or 1.20 instead of 1.40.

[0068] It is preferable that the optical element 100 in each embodiment satisfies the following conditional expression (15).

[0069] 0.10≦P / H2≦0.60 …(15) Condition (15) relates to the shape of the concave-convex elements 21 and the segments. Below the lower limit of condition (15), the segments of the concave-convex elements 21 become relatively small, and a slight change in the width of the concave-convex elements increases the phase modulation. As a result, the influence of manufacturing variations when forming the concave-convex structure 2 increases, making manufacturing difficult. On the other hand, above the upper limit of condition (15), the height of the concave-convex elements 21 in region 2 becomes large, making it difficult to fully obtain the effect of suppressing the aspect ratio.

[0070] In order to further ensure the effects of each embodiment, it is preferable that the lower limit of conditional expression (15) be set to 0.12, 0.14, 0.15, 0.16, 0.17, or 0.18 instead of 0.10, and the upper limit of conditional expression (15) be set to 0.58, 0.56, 0.54, 0.52, 0.50, 0.48, 0.46, 0.44, or 0.42 instead of 0.60.

[0071] When the normalized phase at the boundary between region 1 and region 2 in the same annular zone is E and the designed diffraction order is n, it is preferable to satisfy the following conditional expression (16).

[0072] 0.15≦E / n≦0.95 …(16) Conditional formula (16) relates to the normalized phase of the diffraction action. If the lower limit of conditional formula (16) is not reached, the amount of change in the normalized phase in region 1 increases, and the amount of change in the width of the uneven elements 21 in region 1 must be increased, making it difficult to control the aspect ratio. On the other hand, if the upper limit of conditional formula (16) is reached, the amount of change in the normalized phase in region 2 increases, and the amount of change in the width of the uneven elements 21 in region 2 must be increased, making it difficult to control the aspect ratio.

[0073] In order to further ensure the effects of each embodiment, it is preferable that the lower limit of conditional expression (16) be set to 0.16, 0.20, 0.24, 0.28, 0.30, 0.32, 0.34, 0.36, or 0.38 instead of 0.15, and the upper limit of conditional expression (16) be set to 0.94, 0.93, 0.92, 0.91, 0.90, 0.89, 0.88, 0.87, 0.86, 0.85, 0.84, 0.83, or 0.82 instead of 0.95.

[0074] In each embodiment, when the thickness of the substrate 1 in the optical axis direction is t, it is preferable to satisfy the following conditional expression (17).

[0075] 0.0≦H2 / t≦0.1 …(17) Conditional formula (17) relates to the shape of the optical element 100. The height H2 of the concave-convex elements 21 in region 2 and the thickness t of the substrate 1 are both numerical values ​​indicating lengths and are greater than 0. Therefore, the lower limit of conditional formula (17) will not be exceeded. If the upper limit of conditional formula (17) is exceeded, the thickness of the substrate will be relatively thin, and deformation due to its own weight when held by a holding member will no longer be suppressed, or deformation of the substrate will occur when manufactured using lithography techniques.

[0076] In order to further ensure the effects of each embodiment, it is preferable that the lower limit of conditional expression (17) be set to 0.000001, 0.000005, 0.00001, or 0.0001 instead of 0.0, and the upper limit of conditional expression (17) be set to 0.08, 0.06, 0.04, 0.02, 0.01, 0.008, 0.006, or 0.004 instead of 0.1.

[0077] At the boundary between regions 1 and 2 within the same annular zone, when the length from the segment boundary of pitch P to the end of the underlayer 22 in a direction perpendicular to the thickness direction of the substrate 1, i.e., in the direction perpendicular to the optical axis, is S, it is preferable to satisfy the following conditional formula (18):

[0078] 0.00≦S / P≦0.40 …(18) Conditional formula (18) relates to the shape of the underlayer 22. Here, the offset of the underlayer 22 will be described with reference to Figures 10(a) to (d). Figures 10(a) to (d) are explanatory diagrams of the offset of the underlayer 22.

[0079] 10(a), at the boundary between Region 1 and Region 2 in the same annular zone, an end of base layer 22 is offset by a distance S from the segment boundary in the direction perpendicular to the optical axis, thereby ensuring a sufficient gap between the concave-convex elements 21 in Region 2 and base layer 22. This makes it possible to make the gap between the concave-convex elements 21 or the gap between the concave-convex elements 21 and base layer 22 relatively wide when forming the concave-convex elements 21 by lithography technology, facilitating processing.

[0080] FIG. 10(b) is an xy plan view of the boundary between region 1 and region 2 in the first ring zone of Example 18 described later. Each segment is a square with a side length of P, and the center coordinates (x, y) of the segment are ((j-0.5)×P, (k-0.5)×P) where j and k are integers. In a segment including a concave-convex element 211 that contacts region 1 at one vertex of the segment, the base layer is offset by S in the x direction and the y direction from the segment vertex that contacts region 1. In a segment including a concave-convex element 212 that contacts region 1 at one side of the segment, the base layer is offset by S in the x direction or the y direction from the segment side that contacts region 1. In a segment including a concave-convex element 213 that contacts region 1 at one vertex and two sides of the segment, the base layer is offset by S in the x direction and the y direction from each segment side that contacts region 1. In a segment in which the underlayer 22 is offset, the amount of phase change when light passes through changes compared to when there is no offset. Therefore, it is necessary to change the width of the concave-convex elements according to the offset length S.

[0081] 10(c) shows the normalized diameter, obtained by normalizing the diameter of the convex cylindrical element, which is the uneven element 21, by the segment pitch P when the offset of the underlayer 22 is taken into consideration, and the amount of change in the normalized phase. The segment including the uneven element 211 is region 11, the segment including the uneven element 212 is region 12, and the segment including the uneven element 213 is region 13. It can be seen that in order to obtain the same normalized phase as in region 1, which does not have the offset of the underlayer 22, it is necessary to change the normalized diameter in regions 11, 12, and 13. Note that regions 11, 12, and 13 are located at the boundary between regions 1 and 2 within the same annular zone, and therefore the value of the normalized phase relative to the normalized diameter is shown only for the portion corresponding to the boundary between regions 1 and 2.

[0082] 10(d), at the boundary between region 1 and region 2 in adjacent ring zones, the width of the concave-convex elements in region 2 is configured to be relatively narrow, ensuring a sufficient distance from the underlayer 22. Therefore, it is not necessary to offset the end of underlayer 22 in region 1 from the segment boundary.

[0083] Both the offset length S and the pitch P are numerical values ​​indicating length, and are numerical values ​​equal to or greater than 0, so that they do not fall below conditional formula (18). If the upper limit of conditional formula (18) is exceeded, the desired normalized phase cannot be obtained unless the width of the concave-convex element of the segment that offsets the base layer 22 is relatively large. In this case, it is not possible to secure a sufficient distance from the end of the concave-convex element 21 to the end of the offset base layer 22, making manufacturing difficult. Also, there may be cases where the shape overhangs from the end of the base layer beyond the end of the concave-convex element, making manufacturing difficult.

[0084] In order to further ensure the effects of each embodiment, it is preferable that the lower limit of conditional expression (18) is set to 0.005, 0.01, 0.02, 0.04, 0.05, 0.06, 0.07, or 0.08 instead of 0.00, and the upper limit of conditional expression (18) is set to 0.36, 0.32, 0.28, 0.24, 0.20, 0.18, 0.16, 0.14, or 0.12 instead of 0.40.

[0085] The optical element 100 of each embodiment will be described in detail below.

[0086] 11(a) to (d) are explanatory diagrams of the shape of the concave-convex element 21. The concave-convex element 21 shown in FIG. 11(a) is a convex cylindrical element, and the concave-convex element width Wa is the diameter of the cylinder. The concave-convex element 21 shown in FIG. 11(b) is a convex rectangular prism element, and the concave-convex element width Wb is the length of the side perpendicular to the optical axis of the rectangular prism. The concave-convex element 21 shown in FIG. 11(c) is a concave cylindrical element, and the concave-convex element width Wc is the diameter of the hollow cylinder. The concave-convex element 21 shown in FIG. 11(d) is a convex cross-shaped rectangular prism element, and the concave-convex element widths WS and WL may be the lengths shown in the figure.

[0087] The optical element of Example 1 is composed of a synthetic quartz substrate having a thickness of 0.775 mm, a concave-convex structure consisting of a Si3N4 convex cylindrical element and a uniformly thick underlayer. The concave-convex elements of region 1 and region 2 are arranged in square segments each having a side length of 240 nm, and the heights are 440 nm and 880 nm, respectively, and the height of the underlayer is 440 nm. The effective diameter of the concave-convex structure is φ4.0 mm, and it has 105 rings in which the phase difference of 2π is repeated periodically at a wavelength of 500 nm, and the focal length of the concave-convex structure is 40.0 mm. The position where the normalized phase is 0.54 is set as the boundary between region 1 and region 2 in the ring, and the maximum values ​​of the aspect ratio in region 1 and region 2 are 7.24 and 6.64, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 20.7 of reference example 1 configured without the underlayer.

[0088] The optical element of Example 2 is composed of a 0.775 mm thick synthetic quartz substrate, a concave-convex structure composed of Si3N4 convex cylindrical elements and a uniformly thick underlayer. The concave-convex elements of Region 1 and Region 2 are arranged in square segments with sides of 300 nm, with heights of 500 nm and 1000 nm, respectively, and the height of the underlayer is 500 nm. The effective diameter of the concave-convex structure is φ2.5 mm, and it has 67 rings with a phase difference of 2π repeated periodically at a wavelength of 587.6 nm, and the focal length of the concave-convex structure is 20.0 mm. The position where the normalized phase is 0.59 is the boundary between Region 1 and Region 2 within the ring, and the maximum values ​​of the aspect ratio in Region 1 and Region 2 are 4.46 and 6.29, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 18.9 of Reference Example 2 configured without the underlayer.

[0089] The optical element of Example 3 is composed of a 0.775 mm thick synthetic quartz substrate, a concave-convex structure composed of Si3N4 convex cylindrical elements and a uniformly thick underlayer. The concave-convex elements of region 1 and region 2 are arranged in square segments with sides of 320 nm, with heights of 800 nm and 1600 nm, respectively, and the height of the underlayer is 800 nm. The effective diameter of the concave-convex structure is φ2.5 mm, and it has 79 rings with a phase difference of 4π repeated periodically at a wavelength of 500 nm, and the focal length of the concave-convex structure is 10.0 mm. The position where the normalized phase is 0.80 is the boundary between region 1 and region 2 within the ring, and the maximum values ​​of the aspect ratio in region 1 and region 2 are 5.88 and 9.80, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 21.3 of reference example 3 configured without a underlayer.

[0090] The optical element of Example 4 is composed of a synthetic quartz substrate with a thickness of 0.775 mm, a concave-convex structure composed of a TiO2 convex cylindrical element and a uniformly thick underlayer. The concave-convex elements of region 1 and region 2 are arranged in square segments with sides of 240 nm, with heights of 300 nm and 600 nm, respectively, and the height of the underlayer is 300 nm. The effective diameter of the concave-convex structure is φ12.0 mm, and it has 307 rings with a phase difference of 2π repeated periodically at a wavelength of 587.6 nm, and the focal length of the concave-convex structure is 100.0 mm. The position where the normalized phase is 0.65 is the boundary between region 1 and region 2 within the ring, and the maximum values ​​of the aspect ratio in region 1 and region 2 are 3.55 and 7.01, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 39.3 of reference example 4 configured without a underlayer.

[0091] The optical element of Example 5 is composed of a 2.0 mm thick synthetic quartz substrate, a concave-convex structure composed of Al2O3 convex cylindrical elements and a uniformly thick underlayer. The concave-convex elements of region 1 and region 2 are arranged in square segments with sides of 300 nm, with heights of 700 nm and 1400 nm, respectively, and the height of the underlayer is 700 nm. The effective diameter of the concave-convex structure is φ7.5 mm, and it has 348 rings with a phase difference of 2π repeated periodically at a wavelength of 486.1 nm, and the focal length of the concave-convex structure is 41.7 mm. The position where the normalized phase is 0.60 is the boundary between region 1 and region 2 within the ring, and the maximum values ​​of the aspect ratio in region 1 and region 2 are 5.68 and 8.84, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 26.4 of Reference Example 5, which is configured without a underlayer.

[0092] The optical elements of Examples 6 to 10 have the same specifications as the optical elements of Examples 1 to 5, respectively, except that the height of the concave-convex elements in Region 1 and the height of the undercoat layer are different.

[0093] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 6 are 352 nm and 528 nm, respectively. The position where the normalized phase is 0.58 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 5.02 and 5.83, respectively.

[0094] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 7 are 400 nm and 600 nm, respectively. The position where the normalized phase is 0.70 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 7.90 and 7.58, respectively.

[0095] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 8 are 640 nm and 960 nm, respectively. The position where the normalized phase is 1.40 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 5.32 and 12.47, respectively.

[0096] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 9 are 240 nm and 360 nm, respectively. The position where the normalized phase is 0.68 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 2.63 and 5.36, respectively.

[0097] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 10 are 560 nm and 840 nm, respectively. The position where the normalized phase is 0.58 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 9.86 and 7.97, respectively.

[0098] The optical elements of Examples 11 to 15 have the same specifications as the optical elements of Examples 1 to 5, except that the height of the concave-convex elements in Region 1 and the height of the undercoat layer are different.

[0099] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 11 are 528 nm and 352 nm, respectively. The position where the normalized phase is 0.55 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 6.49 and 7.94, respectively.

[0100] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 12 are 600 nm and 400 nm, respectively. The position where the normalized phase is 0.60 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 8.29 and 13.77, respectively.

[0101] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 13 are 960 nm and 640 nm, respectively. The position where the normalized phase is 1.60 is set as the boundary between region 1 and region 2 in the annular zone, and the maximum aspect ratios in region 1 and region 2 are 5.37 and 15.92, respectively.

[0102] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 14 are 360 ​​nm and 240 nm, respectively. The position where the normalized phase is 0.60 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum aspect ratios in region 1 and region 2 are 3.62 and 11.99, respectively.

[0103] The heights of the concave-convex elements and the underlayer in region 1 of the optical element in Example 15 are 840 nm and 560 nm, respectively. The position where the normalized phase is 0.60 is set as the boundary between region 1 and region 2 within the annular zone, and the maximum values ​​of the aspect ratios in region 1 and region 2 are 7.50 and 11.22, respectively.

[0104] The optical element of Example 16 has the same specifications as the optical element of Example 1, except that the height of the uneven elements in region 1 and the configuration of the underlayer are different. Region 1 of the optical element of Example 16 is shown in FIG. 12, which is an explanatory diagram of the optical element 100 of Example 16. As shown in FIG. 12, the heights H11 and H12 of the uneven elements 21 and the heights HL1 and HL2 of the underlayer 22 have different structures, and the heights of the uneven elements 21 are 352 nm and 528 nm, and the heights of the underlayer 22 are 528 nm and 352 nm. The position where the height of the underlayer 22 differs in region 1 within the ring zone is a position where the normalized phase is 0.78, and the boundary between region 1 and region 2 is a position where the normalized phase is 0.40. The maximum aspect ratios of region 1 are 3.07 and 5.29, and 6.37 in region 2.

[0105] The optical element of Example 17 has the same specifications as the optical element of Example 1, except that the shape of the concave-convex elements in Region 2 is a convex quadrangular prism element with a square cut surface in a plane perpendicular to the optical axis. In Example 17, the region where the normalized phase is 0.60 is the boundary between Regions 1 and 2 in the annular zone, and the maximum values ​​of the aspect ratios in Region 1 and Region 2 are 7.33 and 8.05, respectively. Compared with the maximum aspect ratio of 14.6 in Reference Example 6 configured without a base layer, the aspect ratio is suppressed.

[0106] The optical element of Example 18 has the same specifications as the optical element of Example 1, except that the underlayer boundary is offset by 24 nm from the segment boundary at the boundary between Region 1 and Region 2 in the same annular zone. By offsetting the underlayer boundary, the minimum distance between the end of the underlayer and the uneven elements of Region 2 becomes 49.2 nm from 25.2 nm, making it easier to manufacture.

[0107] In Example 18, the position where the normalized phase is 0.54 is set as the boundary between Region 1 and Region 2 within the annular zone, and the maximum values ​​of the aspect ratios in Region 1 and Region 2 are 7.24 and 6.64, respectively. Note that, although the offset length S is set to 24 nm in this example, the value may be changed to 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, or the like, as long as the uneven elements can be configured.

[0108] The optical element of Example 19 is composed of a synthetic quartz substrate having a thickness of 0.775 mm, and a concave-convex structure consisting of a Si3N4 concave cylindrical element and a uniformly thick underlayer. FIG. 13(a) is a cross-sectional view of the optical element 100 of Example 19 in the xz plane, and FIG. 13(b) is a cross-sectional view in the xy plane. The concave-convex elements of region 1 and region 2 are arranged in square segments with a side length of 300 nm, and the heights are 600 nm and 1200 nm, respectively, and the height of the underlayer is 600 nm. The effective diameter of the concave-convex structure is φ4.0 mm, and it has 105 rings with a phase difference of 2π repeated periodically at a wavelength of 500 nm, and the focal length of the concave-convex structure is 40.0 mm. The position where the normalized phase is 0.65 is the boundary between region 1 and region 2 in the ring, and the maximum aspect ratios in region 1 and region 2 are 11.98 and 7.06, respectively. For this reason, the aspect ratio can be suppressed compared to the maximum aspect ratio of 28.2 in Reference Example 7 in which no underlayer was provided.

[0109] Numerical Examples 1 to 19 corresponding to the optical elements of Examples 1 to 19 are shown below. The phase φ, which indicates the light collecting and diverging action by the uneven structure, is expressed by the following formula, where h is the height from the optical axis in a direction perpendicular to the optical axis (radial direction), m is the diffraction order of the diffracted light, λ0 is the reference wavelength, and Ck (k=1, 2, 3...) is the phase coefficient of each order.

[0110]

number

[0111] The refractive indices at the d-line (587.6 nm), g-line (435.8 nm), F-line (486.1 nm), C-line (656.3 nm), and wavelength of 500 nm are nd, ng, nC, nF, and n500. The widths of the concave-convex elements in regions 1 and 2 are W1 [nm] and W2 [nm], respectively, and the width of the concave-convex elements in the comparative example is Wref [nm].

[0112] [Numerical Example 1] Normalized phase W1 W2 Wref1 0.00 132.45 43.48 0.05 138.45 66.44 0.10 144.15 82.23 0.15 149.64 94.19 0.20 154.97 104.04 0.25 160.19 112.59 0.30 165.32 120.22 0.35 170.38 127.12 0.40 175.42 133.44 0.45 180.48 139.34 0.50 185.58 144.96 0.54 60.79 189.62 149.33 0.60 95.31 155.75 0.65 113.95 161.01 0.70 128.17 166.16 0.75 140.18 171.21 0.80 150.87 176.18 0.85 160.69 181.18 0.90 170.11 186.30 0.95 179.73 191.56 1.00 189.57 196.52 [Numerical Example 2] Normalized phase W1 W2 Wref2 0.00 158.94 52.99 0.05 166.78 82.77 0.10 174.14 102.57 0.15 181.20 117.34 0.20 188.06 129.51 0.25 194.79 140.16 0.30 201.41 149.70 0.35 207.90 158.33 0.40 214.31 166.23 0.45 220.76 173.58 0.50 227.39 180.60 0.55 234.24 187.44 0.59 112.09 239.58 192.84 0.65 141.54 200.86 0.70 160.51 207.43 0.75 177.02 213.88 0.80 191.37 220.27 0.85 203.86 226.74 0.90 215.65 233.51 0.95 228.05 240.57 1.00 239.89 247.29 [Numerical Example 3] Normalized phase W1 W2 Wref3 0.00 163.26 74.98 0.10 169.62 97.75 0.20 175.83 112.71 0.30 181.96 123.86 0.40 188.08 133.16 0.50 194.24 141.46 0.60 200.53 149.09 0.70 206.97 156.17 0.80 136.05 213.53 162.79 0.90 144.54 169.10 1.00 151.29 175.24 1.10 157.24 181.34 1.20 162.72 187.48 1.30 167.77 193.72 1.40 172.49 200.05 1.50 177.01 206.51 1.60 181.51 213.17 1.70 186.07 220.20 1.80 190.64 227.84 1.90 195.15 236.23 2.00 200.02 245.16 [Numerical Example 4] Normalized phase W1 W2 Wref4 0.00 85.65 15.25 0.05 101.98 67.65 0.10 114.61 90.20 0.15 125.27 103.58 0.20 134.52 115.27 0.25 142.73 126.60 0.30 150.29 136.86 0.35 157.51 145.42 0.40 164.56 152.39 0.45 171.42 158.51 0.50 178.06 164.70 0.54 183.29 170.12 0.60 191.36 179.06 0.65 84.56 198.34 186.69 0.70 116.42 193.72 0.75 136.38 199.78 0.80 152.32 205.26 0.85 165.61 211.46 0.90 177.15 219.59 0.95 189.20 228.51 1.00 201.50 230.08 [Numerical Example 5] Normalized phase W1 W2 Wref5 0.00 158.36 52.97 0.05 166.48 79.60 0.10 174.23 97.81 0.15 181.73 111.83 0.20 189.07 123.73 0.25 196.30 134.40 0.30 203.39 144.17 0.35 210.36 153.20 0.40 217.21 161.61 0.45 224.01 169.54 0.50 230.87 177.15 0.54 236.44 183.10 0.60 123.32 244.65 191.89 0.65 144.19 199.09 0.70 161.62 206.16 0.75 177.43 213.07 0.80 191.96 219.85 0.85 205.46 226.63 0.90 218.72 233.54 0.95 232.57 240.59 1.00 245.90 247.22 [Numerical Example 6] Normalized phase W1 W2 0.00 151.05 0.05 156.31 0.10 161.49 0.15 166.64 0.20 171.76 0.25 176.84 0.30 181.89 0.35 186.90 0.40 191.94 0.45 197.05 0.50 202.25 0.55 207.44 0.58 70.16 210.38 0.65 109.34 0.70 126.54 0.75 142.11 0.80 156.88 0.85 170.53 0.90 183.79 0.95 198.06 1.00 211.04 [Numerical Example 7] Normalized phase W1 W2 0.00 132.01 0.05 142.35 0.10 151.62 0.15 160.04 0.20 167.81 0.25 175.12 0.30 182.14 0.35 188.98 0.40 195.70 0.45 202.29 0.50 208.77 0.54 213.90 0.60 221.64 0.65 228.31 0.70 50.66 235.17 0.75 118.64 0.80 152.47 0.85 178.35 0.90 200.04 0.95 219.95 1.00 239.89 [Numerical Example 8] Normalized phase W1 W2 0.00 128.27 0.10 137.09 0.20 145.00 0.30 152.28 0.40 159.10 0.50 165.59 0.60 171.88 0.70 178.05 0.80 184.17 0.90 190.31 1.00 196.51 1.10 202.84 1.20 209.41 1.30 216.32 1.40 120.28 223.63 1.50 143.63 1.60 159.94 1.70 174.47 1.80 188.44 1.90 203.75 2.00 223.92 [Numerical Example 9] Normalized phase W1 W2 0.00 111.87 0.05 123.26 0.10 133.24 0.15 141.71 0.20 149.02 0.25 155.85 0.30 162.77 0.35 169.95 0.40 177.14 0.45 183.91 0.50 190.13 0.55 196.33 0.60 203.43 0.68 91.15 215.18 0.70 105.66 0.75 130.19 0.80 151.59 0.85 169.55 0.90 183.43 0.95 199.62 1.00 215.64 [Numerical Example 10] Normalized phase W1 W2 0.00 175.65 0.05 183.00 0.10 190.27 0.15 197.51 0.20 204.71 0.25 211.79 0.30 218.67 0.35 225.38 0.40 232.02 0.45 238.82 0.50 245.92 0.55 253.07 0.58 56.82 256.90 0.65 122.39 0.70 147.19 0.75 168.58 0.80 188.48 0.85 206.14 0.90 222.66 0.95 240.81 1.00 257.76 [Numerical Example 11] Normalized phase W1 W2 0.00 110.85 0.05 118.59 0.10 125.58 0.15 132.01 0.20 138.04 0.25 143.77 0.30 149.29 0.35 154.63 0.40 159.84 0.45 164.95 0.50 170.02 0.55 81.32 175.10 0.60 99.50 0.65 113.30 0.70 125.22 0.75 136.04 0.80 145.86 0.85 154.81 0.90 163.32 0.95 171.88 1.00 179.95 [Numerical Example 12] Normalized phase W1 W2 0.00 72.61 0.05 95.29 0.10 111.80 0.15 124.95 0.20 136.14 0.25 146.01 0.30 154.90 0.35 163.04 0.40 170.63 0.45 177.84 0.50 184.81 0.55 191.59 0.60 72.34 198.23 0.65 113.91 0.70 141.68 0.75 163.42 0.80 181.55 0.85 196.60 0.90 209.56 0.95 222.18 1.00 233.93 [Numerical Example 13] Normalized phase W1 W2 0.00 100.48 0.10 114.55 0.20 125.47 0.30 134.65 0.40 142.79 0.50 150.23 0.60 157.17 0.70 163.74 0.80 170.07 0.90 176.27 1.00 182.40 1.10 188.53 1.20 194.71 1.30 200.99 1.40 207.48 1.50 214.28 1.60 178.74 221.48 1.70 189.71 1.80 200.78 1.90 212.36 2.00 223.94 [Numerical Example 14] Normalized phase W1 W2 0.00 50.05 0.05 79.97 0.10 97.72 0.15 111.10 0.20 122.41 0.25 132.13 0.30 140.54 0.35 148.11 0.40 155.34 0.45 162.51 0.50 169.56 0.55 176.29 0.60 99.54 182.71 0.65 118.07 0.70 133.58 0.75 148.31 0.80 161.23 0.85 171.92 0.90 182.13 0.95 194.01 1.00 203.77 [Numerical Example 15] Normalized phase W1 W2 0.00 124.75 0.05 135.29 0.10 144.90 0.15 153.80 0.20 162.17 0.25 170.15 0.30 177.83 0.35 185.27 0.40 192.52 0.45 199.62 0.50 206.61 0.55 213.56 0.60 112.01 220.45 0.65 131.35 0.70 147.84 0.75 162.63 0.80 176.09 0.85 188.39 0.90 199.91 0.95 211.15 1.00 221.97 [Numerical Example 16] Normalized phase W11 W12 W2 0.00 138.25 0.05 143.97 0.10 149.47 0.15 154.81 0.20 160.02 0.25 165.13 0.30 170.20 0.35 175.28 0.40 99.88 180.31 0.45 113.75 0.50 125.76 0.54 134.37 0.60 146.02 0.65 155.08 0.70 163.81 0.78 114.69 176.91 0.80 121.81 0.85 137.96 0.90 152.35 0.95 166.17 1.00 179.95 [Numerical Example 17] Normalized phase W1 W2 Wref6 0.00 109.35 60.15 0.05 115.29 73.38 0.10 120.88 83.52 0.15 126.19 91.89 0.20 131.28 99.23 0.25 136.22 105.89 0.30 141.04 112.06 0.35 145.76 117.84 0.40 150.40 123.30 0.45 154.97 128.50 0.50 159.50 133.51 0.54 163.11 137.42 0.60 60.07 168.56 143.16 0.65 90.24 147.85 0.70 110.30 152.46 0.75 125.32 157.02 0.80 137.73 161.53 0.85 148.59 166.04 0.90 158.51 170.61 0.95 168.10 175.24 1.00 177.59 179.85 [Numerical Example 18] Normalized phase W1 W11 W12 W13 W2 0.00 132.52 0.05 138.51 0.10 144.21 0.15 149.70 0.20 155.03 0.25 160.25 0.30 165.37 0.35 170.43 0.40 175.47 0.45 180.53 0.50 185.63 0.54 60.79 67.49 108.63 136.41 189.67 0.60 95.31 99.31 127.32 150.44 0.65 113.95 0.70 128.17 0.75 140.18 0.80 150.87 0.85 160.69 0.90 170.11 0.95 179.73 1.00 189.57 [Numerical Example 19] Normalized phase W1 W2 Wref7 0.00 257.49 257.49 0.10 246.63 246.63 0.20 240.96 240.96 0.30 238.67 238.67 0.40 237.14 237.14 0.50 234.23 234.23 0.60 228.80 228.80 0.70 220.82 220.82 0.80 211.13 211.13 0.90 200.96 200.96 1.00 191.50 191.50 1.10 184.92 184.92 1.20 176.60 176.60 1.30 226.77 170.00 170.00 1.40 220.77 161.81 1.50 210.77 149.89 1.60 190.59 132.42 1.70 161.38 108.89 1.80 130.43 81.29 1.90 100.95 55.45 2.00 50.09 42.53 Various numerical values ​​in each example are summarized in the following Tables 1 to 3(a) to (c).

[0113] [Table 1]

[0114] [Table 2]

[0115] [Table 3(a)]

[0116] [Table 3(b)]

[0117] [Table 3(c)]

[0118] Table 4 shows numerical values ​​representing the concave-convex structures of the comparative examples (Reference Examples 1 to 7) corresponding to the optical elements of the respective examples.

[0119] [Table 4]

[0120] [Optical system] Next, an optical system including the optical elements of each embodiment will be described with reference to FIG. 14. FIG. 14 is an explanatory diagram of an optical system including the optical elements of each embodiment. In FIG. 14, 100 is the optical element of each embodiment, 102 is a lens element, OA is the optical axis, IP is the image surface, and 3 is the optical system including the optical element of each embodiment. The lens element is composed of a refractive lens, a diffractive optical element, a mirror, etc., and may be one or more. The optical element 100 and the lens element 102 are arranged along the optical axis OA, and the incident light is imaged on the imaging surface IP. A converging or diverging effect is obtained by arranging a concave-convex element on the image side surface of the optical element 100. [Imaging device] Next, with reference to FIG. 15, a digital still camera (imaging device) using an optical system including the optical element of each embodiment as an imaging optical system will be described. FIG. 15 is an explanatory diagram of an imaging device 6 equipped with an optical system including the optical element of each embodiment. In FIG. 15, 4 is a camera body, and 3 is an optical system including the optical element of each embodiment. 5 is an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body 4 and receives an optical image formed by the optical system 3 and photoelectrically converts it. The camera body 4 may be a so-called single-lens reflex camera having a quick return mirror, or a so-called mirrorless camera not having a quick return mirror. In this way, by applying the optical system including the optical element of each embodiment to an imaging device such as a digital still camera, an imaging device with a small lens can be obtained.

[0121] According to each embodiment, it is possible to provide an optical element, an optical system, a lens device, and an imaging device having a highly stable fine uneven structure.

[0122] The disclosure of each embodiment includes the following configuration. (Configuration 1) A substrate; A base layer formed on the substrate; a plurality of structures including at least one of concave elements or convex elements; the underlayer is disposed in a first region of the first ring zone and is not disposed in a second region of the first ring zone; the plurality of structures includes a plurality of first structures disposed on the underlayer in the first region and a plurality of second structures disposed on the substrate in the second region; The widths of the first structures are different from one another, An optical element, wherein the plurality of second structures have widths different from one another. (Configuration 2) 2. The optical element according to claim 1, wherein the underlayer is made of the same material as the plurality of structures. (Configuration 3) When the height of each of the plurality of first structures is H1 and the height of each of the plurality of second structures is H2, 0.20≦H1 / H2≦0.90 3. The optical element according to configuration 1 or 2, which satisfies the following conditional expression: (Configuration 4) When the height of each of the plurality of first structures is H1, the height of each of the plurality of second structures is H2, and the height of the base layer is HL, 0.80≦(H1+HL) / H2≦1.20 4. The optical element according to any one of configurations 1 to 3, which satisfies the following conditional expression: (Configuration 5) An optical element described in any one of configurations 1 to 4, characterized in that for light traveling in the thickness direction of the substrate, the phase delay amount caused by the multiple structures is larger in the first region than in the second region. (Configuration 6) When the height of the underlayer is HL, the maximum element packing rate in the first region from the surface position of the substrate to a position of height HL is V1s, the maximum element packing rate in the second region from the surface position of the substrate to a position of height HL is V2s, and the maximum element packing rate in each of the first region and the second region from the position of height HL to the tip position of the structure is V2a, 0.50≦V1s≦1.00 0.80≦V2a / V2s≦1.20 6. The optical element according to any one of configurations 1 to 5, which satisfies the following conditional expression: (Configuration 7) When the height of the underlayer is HL, and the maximum element packing rate from the position of the height HL in the first region to the tip position of the structure is V1a, 0.20≦V1a / V1s≦0.80 7. The optical element according to any one of configurations 1 to 6, which satisfies the following conditional expression: (Configuration 8) When the maximum width and the minimum width of the plurality of first structures are Wmax1 and Wmin1, respectively, and the maximum width and the minimum width of the plurality of second structures are Wmax2 and Wmin2, respectively, 1.05≦Wmax1 / Wmin1≦6.00 1.05≦Wmax2 / Wmin2≦6.00 8. The optical element according to any one of configurations 1 to 7, which satisfies the following conditional expression: (Configuration 9) An optical element described in any one of configurations 1 to 8, characterized in that in the first annular zone, the multiple first structures and the multiple second structures are configured so that the phase of light passing through them monotonically increases or decreases in the radial direction. (Configuration 10) When the maximum value of the aspect ratios of the plurality of first structures is A1 and the maximum value of the aspect ratios of the plurality of second structures is A2, 0.35≦A1 / A2≦2.00 10. The optical element according to any one of configurations 1 to 9, which satisfies the following conditional expression: (Configuration 11) When the height of each of the plurality of second structures is H2 and the reference wavelength is λ0, 0.50≦H2 / λ0≦4.00 11. The optical element according to any one of configurations 1 to 10, which satisfies the following conditional expression: (Configuration 12) When the maximum width of the plurality of first structures is Wmax1 and the maximum width of the plurality of second structures is Wmax2, 0.70≦Wmax1 / Wmax2≦1.40 12. The optical element according to any one of configurations 1 to 11, which satisfies the following conditional expression: (Configuration 13) When the arrangement period of the concave elements or the convex elements of the plurality of structures is P and the height of each of the plurality of second structures is H2, 0.10≦P / H2≦0.60 13. The optical element according to any one of structures 1 to 12, which satisfies the following conditional expression: (Configuration 14) When the normalized phase at the boundary between the first region and the second region in the first ring zone is E and the designed diffraction order is n, 0.15≦E / n≦0.95 14. The optical element according to any one of configurations 1 to 13, which satisfies the following conditional expression: (Configuration 15) When the height of each of the plurality of second structures is H2 and the thickness of the substrate in the optical axis direction is t, 0.0≦H2 / t≦0.1 15. The optical element according to any one of structures 1 to 14, which satisfies the following conditional expression: (Configuration 16) The arrangement period of the concave elements or the convex elements of the plurality of structures is P, and the length in a direction perpendicular to the thickness direction of the substrate from a segment boundary of the arrangement period P to an end of the underlayer at the boundary between the first region and the second region in the first ring zone is S. 0.00≦S / P≦0.40 16. The optical element according to any one of structures 1 to 15, which satisfies the following conditional expression: (Configuration 17) 17. An optical system comprising a plurality of optical elements including the optical element according to any one of claims 1 to 16. (Configuration 18) 18. A lens device comprising the optical system according to aspect 17 and a holding member for holding the optical system. (Configuration 19) 18. An imaging apparatus comprising the optical system according to aspect 17, and an imaging element for receiving an image formed by the optical system.

[0123] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0124] 1 Board 21 Uneven element (structure) 22 Base layer 215 1st structure 216 Second structure 100 Optical Elements

Claims

1. A substrate; A base layer formed on the substrate; a plurality of structures including at least one of concave elements or convex elements; the underlayer is disposed in a first region of the first ring zone and is not disposed in a second region of the first ring zone; the plurality of structures includes a plurality of first structures disposed on the underlayer in the first region and a plurality of second structures disposed on the substrate in the second region; The widths of the first structures are different from one another, An optical element, wherein the widths of the second structures are different from one another.

2. The optical element according to claim 1 , wherein the underlayer is made of the same material as the plurality of structures.

3. When the height of each of the plurality of first structures is H1 and the height of each of the plurality of second structures is H2, 0.20≦H1 / H2≦0.90 2. The optical element according to claim 1, which satisfies the following condition:

4. When the height of each of the plurality of first structures is H1, the height of each of the plurality of second structures is H2, and the height of the underlayer is HL, 0.80≦(H1+HL) / H2≦1.20 2. The optical element according to claim 1, which satisfies the following condition:

5. The optical element according to claim 1 , wherein the amount of phase delay caused by the plurality of structures is greater in the first region than in the second region for light traveling in a thickness direction of the substrate.

6. When the height of the underlayer is HL, the maximum element packing rate from the surface position of the substrate to a position of height HL in the first region is V1s, the maximum element packing rate from the surface position of the substrate to a position of height HL in the second region is V2s, and the maximum element packing rate from the position of height HL to a tip position of the structure in each of the first region and the second region is V2a, 0.50≦V1s≦1.00 0.80≦V2a / V2s≦1.20 2. The optical element according to claim 1, which satisfies the following condition:

7. When the height of the underlayer is HL, and the maximum element packing rate from the position of the height HL in the first region to the tip position of the structure is V1a, 0.20≦V1a / V1s≦0.80 2. The optical element according to claim 1, which satisfies the following condition:

8. When the maximum width and the minimum width of the plurality of first structures are Wmax1 and Wmin1, respectively, and the maximum width and the minimum width of the plurality of second structures are Wmax2 and Wmin2, respectively, 1.05≦Wmax1 / Wmin1≦6.00 1.05≦Wmax2 / Wmin2≦6.00 2. The optical element according to claim 1, which satisfies the following condition:

9. The optical element according to claim 1, characterized in that in the first annular zone, the plurality of first structures and the plurality of second structures are configured so that the phase of light passing therethrough monotonically increases or decreases in a radial direction.

10. When the maximum value of the aspect ratios of the plurality of first structures is A1 and the maximum value of the aspect ratios of the plurality of second structures is A2, 0.35≦A1 / A2≦2.00 2. The optical element according to claim 1, which satisfies the following condition:

11. When the height of each of the plurality of second structures is H2 and the reference wavelength is λ0, 0.50≦H2 / λ0≦4.00 2. The optical element according to claim 1, which satisfies the following condition:

12. When the maximum width of the plurality of first structures is Wmax1 and the maximum width of the plurality of second structures is Wmax2, 0.70≦Wmax1 / Wmax2≦1.40 2. The optical element according to claim 1, which satisfies the following condition:

13. When the arrangement period of the concave elements or the convex elements of the plurality of structures is P and the height of each of the plurality of second structures is H2, 0.10≦P / H2≦0.60 2. The optical element according to claim 1, which satisfies the following condition:

14. When a normalized phase at the boundary between the first region and the second region in the first annular zone is E and a designed diffraction order is n, 0.15≦E / n≦0.95 2. The optical element according to claim 1, which satisfies the following condition:

15. When the height of each of the plurality of second structures is H2 and the thickness of the substrate in the optical axis direction is t, 0.0≦H2 / t≦0.1 2. The optical element according to claim 1, which satisfies the following condition:

16. The arrangement period of the concave elements or the convex elements of the plurality of structures is P, and the length in a direction perpendicular to the thickness direction of the substrate from a segment boundary of the arrangement period P to an end of the underlayer at the boundary between the first region and the second region in the first ring zone is S. 0.00≦S / P≦0.40 2. The optical element according to claim 1, which satisfies the following condition:

17. An optical system comprising a plurality of optical elements including the optical element according to claim 1 .

18. 20. A lens device comprising: the optical system according to claim 17; and a holding member for holding the optical system.

19. 20. An imaging apparatus comprising: the optical system according to claim 17; and an imaging element that receives an image formed by the optical system.

Images