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 plurality of concentrically arranged ring zones. A first ring zone of the plurality of ring zones includes a plurality of first structures (215) having a first height, and a plurality of second structures (216) having a second height different from the first height. The plurality of first structures is different in the width in a radial direction from each other. The plurality of second structures is different in the width in the radial direction 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 focusing or diverging effect by utilizing diffraction by forming a fine uneven structure on the surface of a substrate have been known. Patent Document 1 discloses a metalens formed with a fine uneven structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2020 / 0174163 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an optical element having a highly stable fine uneven structure. [Means for solving the problem]

[0005] An optical element according to one aspect of the present invention has a plurality of concentrically arranged ring zones, a first of the plurality of ring zones includes a plurality of first structures having a first height and a plurality of second structures having a second height different from the first height, the plurality of first structures having different radial widths, and the plurality of second structures having different radial widths.

[0006] Other objects and features of the present invention are illustrated in the following examples. Effect of the Invention

[0007] 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]

[0008] [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] FIG. 23 is a diagram showing the configuration of an optical element in Example 16. [Figure 11] FIG. 21 is a diagram showing the configuration of an optical element in Example 17. [Figure 12] FIG. 23 is a diagram showing the configuration of an optical element in Example 18. [Figure 13] FIG. 2 is an explanatory diagram of an optical system including an optical element in each embodiment. [Figure 14] FIG. 2 is an explanatory diagram of an imaging device including the optical element in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0010] 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.

[0011] The optical element 100 of each embodiment has a substrate 1 and a concave-convex structure (pillar) 2 formed on the substrate 1. The concave-convex structure 2 has a plurality of concave-convex elements (a plurality of structures) 2 including at least one of concave elements or convex elements periodically arranged in the radial direction (for example, the x-axis direction and the y-axis direction) of the substrate 1 (optical element 100). By forming a periodic phase difference (zone) in the radial direction of the substrate 1, a focusing or diverging effect is given 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 A1 (first region) and a region A2 (second region) arranged along the radial direction of the optical element 100. Note that in each embodiment, it is sufficient that at least one of the plurality of zones has the region A1 and the region A2. However, it is preferable that the plurality of zones has the region A1 and the region A2. It is more preferable that all the annular zones have the regions A1 and A2.

[0012] The plurality of concave-convex elements (plural structures) 21 have a plurality of first structures 215 arranged in the region A1 and a plurality of second structures 216 arranged in the region A2. The height (first height) of each of the plurality of first structures 215 is H1, and the height (second height) of each of the plurality of second structures 216 is H2. The heights H1 and H2 are different from each other. The heights H1 of each of the plurality of first structures 215 do not all need to be the same, and some may be different from each other. This point is also true for the height H2 of the plurality of second structures 216. The plurality of first structures 215 have widths in the radial direction different from each other. Similarly, the plurality of second structures 216 have widths in the radial direction different from each other. However, the widths of each of the plurality of first structures 215 do not all need to be different, and some may be the same. This point is also true for the widths of the plurality of second structures 216.

[0013] 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.

[0014] The uneven structure 2 has uneven elements 21. The uneven elements 21 are made of periodically arranged concave or convex elements. In each embodiment, the uneven elements 21 are made of convex cylindrical elements of a dielectric material Si3N4. The shape of the uneven elements 21 is not limited to convex cylindrical elements, and may be polygonal columns, polygonal pyramids, cones, any concave elements, or combinations of these. The material of the uneven elements 21 may be TiO2, GaN, GaP, GaAs, Si, SiC, Al2O3, SiO2, etc.

[0015] 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 filling rate (element filling rate) occupied by the unit partition (segment) regardless of the shape of the concavo-convex element 21. Here, in an optical element having a concavo-convex structure, in order to increase the diffraction efficiency (the ratio of the amount of light directed to a specific diffraction angle to the amount of incident light), it is preferable to make the arrangement pitch of the concavo-convex structure sufficiently smaller than the wavelength of the incident light. For example, when the incident light is in the visible light range (400 to 700 nm), the pitch (arrangement 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 A1 having a plurality of concavo-convex elements 21 with a height H1 and a region A2 having a plurality of concavo-convex elements 21 with a height H2.

[0016] In each embodiment, the convex elements 21 in both the region A1 and the region A2 are made of Si3N4 of the same material. The region A1 and the region A2 in the i-th zone each have a plurality of convex elements 21, and by making the widths in the radial direction of the substrate 1 different from each other, a phase distribution of 2mπ is formed within the zone. Although the top view of Fig. 1(b) shows a schematic diagram in which the segments 11 are arranged in one dimension, the segments 11 may be arranged two-dimensionally to obtain condensing and diverging light. In the direction perpendicular to the optical axis, let the radii of the region A1 and the region A2 of the i-th zone from the optical axis be RLi and RHi, respectively. As can be seen from Fig. 1(c), the region A1 and the region A2 are alternately configured concentrically in the direction perpendicular to the optical axis so that RLi < RHi.

[0017] Next, as a comparative example, an optical element 101 in which the convex elements 21 have a constant height H in all regions 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 phase distribution of 2nπ in the annular zone, the width (diameter) of the convex cylindrical elements, which are the convex-shaped cylindrical elements 21, is changed to change the element packing rate of the convex-convex elements 21 in 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 elements, 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 elements, so the diameter is changed greatly. Therefore, the minimum diameter of the convex cylindrical elements tends to be small, and the aspect ratio (the ratio of the height to the width of the convex-convex elements 21 (height / width)) tends to be large. In the case of elements that are relatively elongated with a large aspect ratio, 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, the height of the concave-convex elements in the area A2 where the phase modulation amount is relatively small is set low, thereby forming the concave-convex structure 2 without increasing the aspect ratio.

[0018] FIG. 3 is a diagram showing the relationship between the shape of the concave-convex element 21 of the optical element 100 in each embodiment and the amount of phase modulation, and relates to the diameter of the convex cylindrical element, which is the concave-convex element 21, and the amount of phase modulation. In FIG. 3, the horizontal axis indicates the normalized diameter obtained by normalizing the diameter W of the convex cylindrical element by the pitch P of the segments, and the vertical axis indicates the normalized phase obtained by normalizing the amount of phase modulation by 2mπ (diffraction order m=1). When the normalized phase is in the range of 0 to 0.488, the normalized diameter of the convex cylindrical element in the region A2 is changed from 0.187 to 0.813. When the normalized phase is in the range of 0.488 to 1, the normalized diameter of the convex cylindrical element in the region A1 is changed from 0.592 to 0.813. As a result, a phase modulation amount of normalized phase 0 to 1 is obtained, and the maximum aspect ratios AR1 and AR2 of the multiple structures 215 in the region A1 and the multiple structures 216 in the region A2 are 6.2 and 9.8, respectively.

[0019] 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 in the optical element 101 and the phase modulation amount. In this case, in order to obtain a phase modulation amount of normalized phase 0 to 1, the normalized diameter needs to be changed from 0.181 to 0.819, and the aspect ratio is 20.2 at the maximum, which is larger than the aspect ratio when the height of the convex elements 21 is changed for each region. This shows that the aspect ratio of the convex elements 21 can be suppressed by changing the height of the convex elements 21 for each region.

[0020] 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 may be used, such as directly forming the concave-convex structure 2 using an electron beam, a laser, or the like.

[0021] 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 A1 and the region A2 as in Fig. 6. The substrate 1 may include the offset layer 34.

[0022] Here, the height of each of the concave-convex elements 21 in the region A1 (the height of each of the first structures 215) is H1, and the height of each of the concave-convex elements 21 in the region A2 (the height of each of the second structures 216) is H2. The maximum width of the concave-convex elements 21 in the region A1 (the maximum width of the first structures 215, in FIG. 1(a) the width of the leftmost convex element in the region A1) is Wmax1. The maximum width of the concave-convex elements 21 in the region A2 (the maximum width of the second structures 216, in FIG. 1(a) the width of the leftmost convex element in the region A2) is Wmax2. The minimum width of the concave-convex elements 21 in the region A1 (the minimum width of the first structures 215, in FIG. 1(a) the width of the rightmost convex element in the region A1) is Wmin1. Furthermore, the minimum width of the concave-convex elements 21 in the region A2 (the minimum width of the second structures 216, the width of the rightmost convex element in the region A2 in FIG. 1(a)) is taken as Wmin2. In this case, in each embodiment, it is preferable to satisfy at least one of the following conditional expressions (1) to (3).

[0023] 0.05≦H2 / H1≦0.95 …(1) 1.00 <Wmax1 / Wmin1<20.00 …(2) 1.00 <Wmax2 / Wmin2<20.00 …(3) Conditional formula (1) relates to the shape of the concave-convex elements 21. By configuring the height H2 of the concave-convex elements 21 in the region A2, where the amount of phase modulation is relatively small, to be lower than the height H1 of the concave-convex elements 21 in the region A1, it is possible to realize a shape in which the aspect ratio of the concave-convex elements 21 is reduced while obtaining a desired amount of phase modulation.

[0024] If the lower limit of conditional formula (1) is exceeded, the height H2 of the concave-convex elements 21 in region A2 becomes relatively low, making it difficult to increase the amount of phase modulation when the width of the concave-convex elements 21 in region A2 is changed. In this case, in order to obtain a desired amount of phase modulation, it is necessary to change the width of the concave-convex elements 21 in region A2 relatively largely, making it difficult to obtain the effect of reducing the aspect ratio in region A2. In each embodiment, it is more preferable that the lower limit of conditional formula (1) is set to 0.10, 0.15, 0.20, 0.24, 0.28, 0.32, 0.34, or 0.36 instead of 0.05.

[0025] On the other hand, when the upper limit value of conditional formula (1) is exceeded, the height H2 of the concave-convex elements 21 in region A2 becomes relatively high, and in order to obtain a desired phase modulation amount, it is necessary to relatively reduce the width of the concave-convex elements 21 in region A2, making it difficult to obtain the effect of reducing the aspect ratio in region A2. In each embodiment, it is more preferable that the upper limit value of conditional formula (1) is set to 0.90, 0.85, 0.80, 0.76, 0.72, 0.70, 0.68, 0.66, 0.64, 0.62, or 0.60 instead of 0.95.

[0026] When the concave-convex element 21 has a cylindrical shape, the diameter of the circle can be used as the width of the concave-convex element as shown in Fig. 1(b). The width of the concave-convex element 21 may be converted to the length of a side in the case of a rectangular prism element, or to the diameter of a cylindrical element that provides an equivalent amount of phase modulation in the case of a complex shape, and used as the width of the concave-convex element.

[0027] Conditional formula (2) and conditional formula (3) relate to the shape of the concave-convex elements 21. By varying the width of the concave-convex elements 21 within a predetermined range in the regions A1 and A2, a desired amount of phase modulation can be obtained.

[0028] In the conditional expressions (2) and (3), the maximum width is normalized by the minimum width of the concave-convex element 21, so that the minimum width will not fall below the lower limit, but the desired phase modulation amount can be easily obtained by setting the minimum width to a certain degree. In each embodiment, the lower limit of the conditional expressions (2) and (3) is more preferably set to 1.04, 1.08, 1.12, 0.14, 1.18, 1.22, 1.24, or 1.26, instead of 1. If the upper limit of the conditional expressions (2) and (3) is exceeded, the width of the concave-convex element 21 becomes relatively small, so that the aspect ratio becomes large. In each embodiment, the upper limit of the conditional expressions (2) and (3) is more preferably set to 18, 16, 14, 12, 10, 8, 7, 6, or 5, instead of 20.

[0029] When the height of the unevenness elements 21 has a slight undulation in the radial direction of the substrate, it is preferable that the average value of the height of the unevenness elements within the annular zone satisfies conditional formula (1). Moreover, in areas where the effects of the present invention are not expected, such as unintended local unevenness due to manufacturing errors or structures outside the effective light beam area, it is not necessarily necessary to satisfy conditional formulas (1) to (3).

[0030] In each embodiment, when each of the structures is a concave element, the structure refers to a structure including a side surface and a bottom surface that form the space of the concave portion. In this case, the height of the structure is the height of the concave portion, and the width of the structure is the width of the concave portion.

[0031] Here, the repeating period of the concave / convex elements (arrangement period: pitch of the concave or convex elements which are unit elements of the multiple structures) is defined as P. The difference between the maximum and minimum widths of the concave / convex elements 21 in region A1 (the difference between the maximum and minimum widths of the multiple first structures 215) is defined as ΔW1, and the difference between the maximum and minimum widths of the concave / convex elements 21 in region A2 (the difference between the maximum and minimum widths of the multiple second structures 216) is defined as ΔW2. In this case, in each embodiment, it is preferable to satisfy the following conditional expressions (4) and (5).

[0032] 0.05≦ΔW1 / P≦0.80 …(4) 0.15≦ΔW2 / P≦0.95 …(5) Conditional expressions (4) and (5) relate to the radial shape of the concave-convex elements 21. By satisfying conditional expressions (4) and (5), the amount of change in the width of the concave-convex elements 21 can be suppressed, and a shape with a reduced aspect ratio of the concave-convex elements 21 can be realized. If the lower limit of conditional expressions (4) and (5) is not met, the amount of phase modulation obtained by a slight change in the width of the concave-convex elements 21 changes significantly, making it difficult to stably manufacture an optical element having the desired performance. If the upper limit of conditional expressions (4) and (5) is exceeded, the width of the concave-convex elements 21 becomes small, the aspect ratio becomes large, and the interval between adjacent concave-convex elements becomes narrow, making manufacture difficult.

[0033] In order to further ensure the effects of each embodiment, the lower limit of conditional expression (4) is more preferably set to 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, or 0.15, instead of 0.05. The upper limit of conditional expression (4) is more preferably set to 0.76, 0.72, 0.68, 0.64, 0.62, or 0.60, instead of 0.15. The lower limit of conditional expression (5) is more preferably set to 0.16, 0.17, 0.18, 0.20, 0.22, 0.24, or 0.26, instead of 0.15. The upper limit of conditional expression (5) is more preferably set to 0.90, 0.86, 0.82, 0.78, 0.74, 0.72, or 0.70.

[0034] In each embodiment, it is preferable to satisfy the following condition (6).

[0035] 0.05≦ΔW1 / ΔW2≦1.50 …(6) Conditional formula (6) relates to the relationship between the shapes of the concave-convex elements 21 in the region A1 and the region A2. By satisfying conditional formula (6), it is possible to realize a shape with a reduced aspect ratio of the concave-convex elements, particularly in the region A2. If the lower limit of conditional formula (6) is not met, the amount of phase modulation obtained by a slight change in the width of the concave-convex elements 21 in the region A1 changes significantly, making it difficult to manufacture an optical element with the desired performance in a stable manner. On the other hand, if the upper limit of conditional formula (6) is exceeded, the amount of change in the width of the concave-convex elements 21 in the region A1 becomes relatively large, and the aspect ratio becomes large. 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 0.10, 0.14, 0.18, 0.22, 0.24, or 0.25, instead of 0.05. It is more preferable that the upper limit of condition (6) be set to 1.45, 1.40, 1.35, 1.30, 1.25 or 1.20 instead of 1.50.

[0036] 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 larger in region A1 than in region A2. 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, which is an unevenness structure of a constant height, is shown by a dotted line.

[0037] In each embodiment, the height of the concave-convex elements in region A1 is made higher than in region A2 to increase the amount of phase modulation, and the concave-convex element width is changed in each region. In this way, in each embodiment, the aspect ratio of the concave-convex elements in region A1 and region A2 is suppressed by making the change in the concave-convex element width smaller than in the comparative example. When the phase modulation by the concave-convex structure in region A1 is smaller than that in region A2, the change in the concave-convex element width in region A1 and region A2 must be made relatively large to obtain the desired phase distribution, and the aspect ratio suppression effect cannot be obtained.

[0038] Next, the element packing ratio will be described with reference to Fig. 9(a) and (b). Fig. 9(a) and (b) are explanatory diagrams of the element packing ratio, with Fig. 9(a) showing the element packing ratio in area A1 where uneven elements 21 with height H1 are arranged, and Fig. 9(b) showing the element packing ratio in area A2 where uneven elements 21 with height H2 are arranged.

[0039] The element packing rate is the ratio of the volume occupied by the concave-convex elements per segment. The element packing rate of the regions A1 and A2 is the volume ratio of the convex elements 21 to the volume Va of the bottom surface P×P and height H1, as shown in Figures 9(a) and (b). When the minimum value of the element packing rate of the concave-convex elements of the region A1 is V1min and the maximum value of the element packing rate of the concave-convex elements of the region A2 for the repeating period P and the height H1 of the concave-convex elements of the region A1 is V2max, it is preferable to satisfy the following conditional formula (7).

[0040] 0.70≦V2max / V1min≦1.50 …(7) Conditional formula (7) relates to the shape of the concave-convex elements in the region A1 and the region A2. By satisfying conditional formula (7), it is possible to realize a shape with a reduced aspect ratio of the concave-convex elements. If the lower limit of conditional formula (7) is exceeded, the minimum width of the concave-convex structure in the region A1 becomes small, and the aspect ratio increases. On the other hand, if the upper limit of conditional formula (7) is exceeded, the maximum width of the concave-convex structure in the region A2 becomes large, and the interval between the concave-convex elements becomes narrow, making manufacturing difficult. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (7) is set to 0.74, 0.76, 0.78, 0.79, 0.80, 0.81, or 0.82, instead of 0.70. It is more preferable that the upper limit of conditional formula (7) is set to 1.45, 1.40, 1.35, 1.30, 1.25, or 1.20, instead of 1.50.

[0041] When the maximum values ​​of the aspect ratios of the concave-convex elements in the regions A1 and A2 are AR1 and AR2, respectively, it is preferable that the following conditional expression (8) be satisfied.

[0042] 1.50≦AR1≦20.00 …(8) 1.50≦AR2≦20.00 …(9) 0.50≦AR2 / AR1≦4.00 …(10) Conditional formula (8) and conditional formula (9) relate to the shape of the concave-convex elements of region A1 and region A2. If the lower limit of conditional formula (8) and conditional formula (9) is not met, the phase modulation becomes relatively large with a slight change in the width of the concave-convex elements, and the influence of manufacturing variations during the formation of the concave-convex structure becomes large, making manufacturing difficult. On the other hand, if the upper limit of conditional formula (8) and conditional formula (9) is exceeded, the aspect ratio becomes large and the structure is easily destroyed by external factors. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (9) and conditional formula (10) is 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. It is more preferable that the upper limit values ​​of conditional expressions (8) and (9) 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.

[0043] Conditional formula (10) relates to the shape of the concave-convex element. If the lower limit of conditional formula (10) is exceeded, the change in the concave-convex element width in region A1 increases, and the aspect ratio suppression effect in region A1 cannot be obtained. If the upper limit of conditional formula (10) is exceeded, the change in the concave-convex element width in region A2 increases, and the aspect ratio suppression effect in region A2 cannot be obtained. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (10) is set to 0.60, 0.80, 1.00, 1.20, 1.40, 1.60, 1.80, 1.90, or 2.00 instead of 0.50. It is more preferable that the upper limit of conditional formula (10) is set to 3.80, 3.60, 3.40, 3.20, 3.00, 2.80, 2.60, 2.50, or 2.40 instead of 4.00.

[0044] In each embodiment, it is preferable that the maximum widths Wmax1 and Wmax2 of the concave and convex elements in the regions A1 and A2 satisfy the following conditional expression (11).

[0045] 0.60≦Wmax2 / Wmax1≦1.20 …(11) Conditional formula (11) relates to the shape of the concave-convex elements. If the lower limit of conditional formula (11) is exceeded, the width of the concave-convex elements in region A2 becomes relatively small, and the aspect ratio must be increased to obtain a desired phase difference. On the other hand, if the upper limit of conditional formula (11) is exceeded, the width of the concave-convex elements in region A1 becomes relatively small, and the aspect ratio must be increased to obtain a desired phase difference. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (11) be 0.60, 0.65, 0.70, 0.75, 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, or 0.95, instead of 0.50. It is more preferable that the upper limit of condition (11) be set to 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, or 1.05, instead of 1.20.

[0046] In the optical element of each embodiment, the phase distribution depends on the reference wavelength (design wavelength) λ0. In this case, when the difference in height between the concave and convex elements of the region A1 and the region A2 is ΔH and the diffraction order is m, it is preferable to satisfy the following conditional expression (12).

[0047] 0.25≦ΔH / (m×λ0)≦3.00 …(12) Conditional formula (12) relates to the shape of the concave-convex element. The phase distribution determines the annular zone based on the phase relative to the reference wavelength λ0. If the lower limit of conditional formula (12) is exceeded, the difference in the amount of phase modulation obtained in region A1 and region A2 becomes small, so the desired phase difference cannot be obtained unless the change in the width of the concave-convex element in each region is increased, and the aspect ratio suppression effect cannot be obtained. On the other hand, if the upper limit of conditional formula (12) is exceeded, the aspect ratio becomes large and the structure is easily destroyed by external factors. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (12) is set to 0.30, 0.35, 0.40, 0.45, 0.50, 0.60, 0.65, 0.70, or 0.75 instead of 0.25. It is more preferable that the upper limit of condition (12) be set to 2.50, 2.00, 1.80, 1.60, 1.40, 1.30 or 1.20 instead of 3.00.

[0048] In each embodiment, when the ratio of the minimum phase in the area A1 to the maximum phase difference in the annular zone is NP, it is preferable to satisfy the following conditional expressions (13) and (14).

[0049] 0.15≦NP≦0.85 …(13) 0.50≦NP / H2×H1≦1.50 …(14) Conditional formula (13) relates to the amount of phase modulation at the boundary between the region A1 and the region A2. If the lower limit of conditional formula (13) is exceeded, the amount of change in the width of the uneven element in the region A1 increases, and the aspect ratio suppression effect in the region A1 cannot be obtained. On the other hand, if the upper limit of conditional formula (13) is exceeded, the amount of change in the width of the uneven element in the region A2 increases, and the aspect ratio suppression effect in the region A2 cannot be obtained. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of conditional formula (13) is set to 0.18, 0.20, 0.22, 0.24, 0.28, 0.32, 0.34, 0.36, 0.38, or 0.40, instead of 0.15. It is more preferable that the upper limit of conditional formula (13) is set to 0.80, 0.75, 0.70, 0.65, or 0.60, instead of 0.85.

[0050] Conditional formula (14) relates to the amount of phase modulation at the boundary between the region A1 and the region A2 and the shape of the concave-convex element. By setting the ratio NP of the minimum phase of the region A1 to the maximum phase difference in the annular zone according to the height of the concave-convex element of the region A1 and the region A2, the aspect ratio suppression effect of the concave-convex element can be further obtained. If the lower limit of the conditional formula (14) is exceeded, the amount of change in the width of the concave-convex element in the region A1 increases, and the aspect ratio suppression effect in the region A1 cannot be obtained. On the other hand, if the upper limit of the conditional formula (14) is exceeded, the amount of change in the width of the concave-convex element in the region A2 increases, and the aspect ratio suppression effect in the region A2 cannot be obtained. In order to further ensure the effects of each embodiment, it is more preferable that the lower limit of the conditional formula (14) is set to 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, or 0.90 instead of 0.50. It is more preferable that the upper limit of condition (14) be set to 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1.15 or 1.10, instead of 1.50.

[0051] It is preferable that the uneven elements of the regions A1 and A2 have a monotonically increasing or decreasing phase modulation along the radial direction of the substrate within the annular zone. If the phase modulation increases or decreases discretely, the uneven element width needs to be changed relatively greatly, and the aspect ratio suppression effect cannot be obtained. When a plane wave is incident on the optical element of each embodiment in the substrate thickness direction, and the optical element has a focusing effect, the phase delay in the phase modulation in the annular zone decreases monotonically in the radial direction from the inside to the outer periphery of the substrate. Also, when the optical element has a diverging effect, the phase delay in the phase modulation in the annular zone increases monotonically in the radial direction from the inside to the outer periphery of the substrate.

[0052] 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 (15).

[0053] 0.00≦H2 / t≦0.10 …(15) Conditional formula (15) relates to the shape of the optical element. The height H2 of the uneven elements in the region A2 and the thickness t of the substrate are both numerical values ​​indicating length, and are numerical values ​​greater than 0, so they do not fall below the lower limit of conditional formula (15). If the upper limit of conditional formula (15) is exceeded, the thickness of the substrate becomes relatively thin, and deformation due to its own weight cannot be suppressed when held by a holding member, or deformation of the substrate occurs when manufacturing using lithography technology. In order to further ensure the effects of each embodiment, it is preferable that the lower limit of conditional formula (15) is set to 0.000001, 0.000005, 0.00001, or 0.0001, instead of 0.00. It is preferable that the upper limit of conditional formula (15) is set to 0.08, 0.06, 0.04, 0.02, 0.01, 0.008, 0.006, or 0.004, instead of 0.10.

[0054] The optical elements of each embodiment will be described in detail below.

[0055] The optical element of Example 1 is composed of a synthetic quartz substrate having a thickness of 0.775 mm and a concave-convex structure composed of convex cylindrical elements of Si3N4. The concave-convex elements of the regions A1 and A2 are arranged in square segments each having a side length of 240 nm, and the heights H1 and H2 are 880 nm and 440 nm, respectively. The effective diameter of the concave-convex structure is φ4.0 mm, and it has 105 ring zones in which the phase difference of 2π (diffraction order 1) at a wavelength of 500 nm is repeated periodically, and the focal length of the concave-convex structure is 40.0 mm. The position where the normalized phase is 0.488 is set as the boundary between the regions A1 and A2 in the ring zone, and the maximum values ​​of the aspect ratio in the regions A1 and A2 are 6.20 and 9.80, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 20.2 of the reference example 1 in which the height of the concave-convex elements is configured to be equal in all regions.

[0056] The optical element of Example 2 is composed of a synthetic quartz substrate having a thickness of 0.775 mm and a concave-convex structure composed of convex cylindrical elements of Si3N4. The concave-convex elements of the regions A1 and A2 are arranged in square segments each having a side length of 300 nm, and the heights H1 and H2 are 1000 nm and 500 nm, respectively. The effective diameter of the concave-convex structure is φ2.5 mm, and it has 67 ring zones in which the phase difference of 2π (diffraction order 1) is repeated periodically at a wavelength of 587.56 nm, and the focal length of the concave-convex structure is 20.0 mm. The position where the normalized phase is 0.510 is the boundary between the regions A1 and A2 in the ring zone, and the maximum values ​​of the aspect ratio in the regions A1 and A2 are 5.55 and 9.18, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 18.9 of the reference example 2 in which the height of the concave-convex elements is configured to be equal in all regions.

[0057] The optical element of Example 3 is composed of a synthetic quartz substrate having a thickness of 0.775 mm and a concave-convex structure composed of convex cylindrical elements of Si3N4. The concave-convex elements of the regions A1 and A2 are arranged in square segments each having a side length of 320 nm, and the heights H1 and H2 are 1600 nm and 800 nm, respectively. The effective diameter of the concave-convex structure is φ2.5 mm, and it has 72 ring zones in which the phase difference of 4π (diffraction order 2) is repeated periodically at a wavelength of 546.07 nm, and the focal length of the concave-convex structure is 10.0 mm. The position where the normalized phase is 0.498 is the boundary between the regions A1 and A2 in the ring zone, and the maximum values ​​of the aspect ratio in the regions A1 and A2 are 8.57 and 15.06, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 31.3 of the reference example 3 in which the height of the concave-convex elements is equal in all regions.

[0058] The optical element of Example 4 is composed of a synthetic quartz substrate having a thickness of 0.775 mm, a concave-convex structure consisting of a TiO2 convex cylindrical element and a uniformly thick underlayer (offset layer). The concave-convex elements of the regions A1 and A2 are arranged in square segments each having a side length of 240 nm, and the heights H1 and H2 are 600 nm and 300 nm, respectively. The effective diameter of the concave-convex structure is φ6.0 mm, and it has 90 ring zones in which the phase difference of 2π (diffraction order 1) at a wavelength of 500 nm is repeated periodically, and the focal length of the concave-convex structure is 100.0 mm. The position where the normalized phase is 0.475 is the boundary between the regions A1 and A2 in the ring zone, and the maximum values ​​of the aspect ratio in the regions A1 and A2 are 4.25 and 5.83, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 11.9 of Reference Example 4 in which the heights of the concave-convex elements are configured to be equal in all regions.

[0059] The optical element of the fifth embodiment is composed of a 2.0 mm thick synthetic quartz substrate, a concave-convex structure consisting of a convex cylindrical element of Al2O3 and a uniform thickness underlayer (offset layer). The concave-convex elements of the regions A1 and A2 are arranged in square segments with sides of 300 nm, and the heights H1 and H2 are 1400 nm and 700 nm, respectively. The effective diameter of the concave-convex structure is φ6.0 mm, and it has 223 ring zones with a phase difference of 2π (diffraction order 1) 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 0.490 is the boundary between the regions A1 and A2 in the ring zone, and the maximum aspect ratios in the regions A1 and A2 are 8.08 and 12.74, respectively. For this reason, the aspect ratio can be suppressed compared to the maximum aspect ratio of 26.5 in Reference Example 5 in which the heights of the concave and convex elements are configured to be equal in all regions.

[0060] 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 heights of the concave and convex elements in the region A2 are different.

[0061] The height of the concave and convex elements in region A2 of the optical element in Example 6 is 352 nm. The position where the normalized phase is 0.390 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 6.77 and 7.78, respectively.

[0062] The height of the concave and convex elements in region A2 of the optical element in Example 7 is 400 nm. The position where the normalized phase is 0.250 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 7.30 and 7.29, respectively.

[0063] The height of the concave and convex elements in region A2 of the optical element in Example 8 is 640 nm. The position where the normalized phase is 0.375 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 9.56 and 11.84, respectively.

[0064] The height of the concave and convex elements in region A2 of the optical element in Example 9 is 240 nm. The position where the normalized phase is 0.68 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 4.67 and 4.64, respectively.

[0065] The height of the concave and convex elements in region A2 of the optical element in Example 10 is 560 nm. The position where the normalized phase is 0.389 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 8.94 and 10.10, respectively.

[0066] 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 H2 of the concave-convex elements in the region A2 is different.

[0067] The height H2 of the concave and convex elements in region A2 of the optical element in Example 11 is 528 nm. The position where the normalized phase is 0.590 is the boundary between region A1 and region A2 in the annular zone, and the maximum aspect ratios in region A1 and region A2 are 5.73 and 11.83, respectively.

[0068] The height H2 of the concave and convex elements in region A2 of the optical element in Example 12 is 600 nm. The position where the normalized phase is 0.60 is the boundary between region A1 and region A2 in the annular zone, and the maximum aspect ratios in region A1 and region A2 are 5.22 and 11.08, respectively.

[0069] The height H2 of the concave and convex elements in region A2 of the optical element in Example 13 is 960 nm. The position where the normalized phase is 0.587 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 8.00 and 18.27, respectively.

[0070] The height H2 of the concave and convex elements in region A2 of the optical element in Example 14 is 360 nm. The position where the normalized phase is 0.56 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 4.00 and 7.04, respectively.

[0071] The height H2 of the concave and convex elements in region A2 of the optical element in Example 15 is 840 nm. The position where the normalized phase is 0.591 is set as the boundary between region A1 and region A2 in the annular zone, and the maximum values ​​of the aspect ratios in region A1 and region A2 are 7.42 and 15.41, respectively.

[0072] The optical element of Example 16 has the same specifications as the optical element of Example 1, except that the height H1 of the concave-convex elements in region A1 is different.

[0073] Fig. 10 is a diagram showing the configuration of an optical element according to Example 16. As shown in Fig. 10, the region A2 of the optical element according to Example 16 has a region A21 with a height of the concave-convex elements of H1 and a region A22 with a height of H2, and the height of the concave-convex elements in region A1 is 880 nm, and the height of the concave-convex elements in region A2 is 528 nm and 352 nm, respectively. The position where the heights of the concave-convex elements in region A2 within the annular zone are different is a position where the normalized phase is 0.28, and the boundary between regions A1 and 2 is a position where the normalized phase is 0.59. The maximum aspect ratio of region A1 is 5.74, and in region A2 it is 3.74 and 7.07.

[0074] The optical element of Example 17 is composed of a synthetic quartz substrate and a concave-convex structure made of convex square columnar elements made of Si3N4.

[0075] FIG. 11 is a diagram (top view) of the configuration of the optical element of Example 17. The rectangular prism elements of region A1 and region A2 are arranged in square segments with sides of 240 nm, and the heights H1 and H2 are 800 nm and 400 nm, respectively. The effective diameter and the number of zones of the concave-convex structure are the same as those of the optical element of Example 1. The width of the concave-convex element in the rectangular prism element can be the length of the side of the rectangular prism in the radial direction of the optical element as shown in FIG. 11. The position where the normalized phase is 0.478 is set as the boundary between region A1 and region A2 in the zone, and the maximum values ​​of the aspect ratio in region A1 and region A2 are 6.09 and 7.26, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 15.3 of Reference Example 6 in which the heights of the concave-convex elements are configured to be equal in all regions.

[0076] The optical element of Example 18 is composed of a synthetic quartz substrate and a concave-convex structure composed of Si3N4 concave cylindrical elements. Figures 12(a) and 12(b) are diagrams of the optical element of Example 18, with Figure 12(a) showing a cross-sectional view and Figure 12(b) showing a top view. The rectangular prism elements in region A1 and region A2 are arranged in square segments with sides of 240 nm, and their heights are 800 nm and 560 nm, respectively. The effective diameter and the number of annular zones of the concave-convex structure are the same as those of the optical element of Example 1. The minimum width of the concave-convex elements in the concave-shaped elements can be the value obtained by subtracting the maximum width of the concave elements from the repetition period P. That is, the minimum widths of the concave-convex elements in region A1 and region A2 of Example 18 are 60.9 nm and 42.8 nm, respectively. The position where the normalized phase is 0.478 is set as the boundary between area A1 and area A2 in the annular zone, and the maximum aspect ratios in area A1 and area A2 are 13.13 and 13.09, respectively. Therefore, the aspect ratio is suppressed compared to the maximum aspect ratio of 37.9 in reference example 7, in which the heights of the concave and convex elements are configured to be equal in all areas.

[0077] Numerical examples 1 to 18 corresponding to the optical elements of the embodiments are shown below.

[0078] The phase φ, which indicates the focusing and diverging action of the uneven structure, is expressed by the following equation, where h is the height from the optical axis in the 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.

[0079]

number

[0080] 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 the regions A1 and A2 are W1 [nm] and W2 [nm], respectively, and the width of the concave-convex elements in the comparative example is Wref [nm]. [Numerical Example 1] Normalized phase W1 W2 Wref 0.00 44.89 43.48 0.05 82.64 66.44 0.10 104.37 82.23 0.15 120.82 94.19 0.20 134.31 104.04 0.25 146.06 112.59 0.30 157.03 120.22 0.35 167.49 127.12 0.40 177.46 133.44 0.45 187.60 139.34 0.50 143.42 144.96 0.55 148.92 150.41 0.60 154.29 155.75 0.65 159.56 161.01 0.70 164.74 166.16 0.75 169.80 171.21 0.80 174.79 176.18 0.85 179.78 181.18 0.90 184.89 186.30 0.95 190.12 191.56 1.00 195.11 196.52 [Numerical Example 2] Normalized phase W1 W2 Wref 0.00 54.47 52.75 0.05 102.86 82.62 0.10 129.99 102.46 0.15 150.50 117.25 0.20 167.33 129.44 0.25 182.02 140.09 0.30 195.87 149.64 0.35 209.22 158.28 0.40 222.10 166.18 0.45 235.47 173.54 0.50 248.19 180.55 0.55 185.74 187.39 0.60 192.51 194.14 0.65 199.20 200.82 0.70 205.78 207.39 0.75 212.24 213.84 0.80 218.63 220.22 0.85 225.09 226.70 0.90 231.81 233.46 0.95 238.81 240.52 1.00 245.53 247.25 [Numerical Example 3] Normalized phase W1 W2 Wref 0.00 53.13 51.19 0.05 107.92 87.82 0.10 137.29 109.52 0.15 158.02 124.50 0.20 174.48 136.56 0.25 188.78 147.21 0.30 202.51 156.88 0.35 216.34 165.67 0.40 230.67 173.71 0.45 247.16 181.22 0.50 187.06 188.47 0.55 194.30 195.70 0.60 201.62 203.04 0.65 209.05 210.50 0.70 216.53 218.01 0.75 224.02 225.53 0.80 231.60 233.14 0.85 239.52 241.13 0.90 248.13 249.85 0.95 257.54 259.40 1.00 266.87 268.81 [Numerical Example 4] Normalized phase W1 W2 Wref 0.00 51.43 50.31 0.05 89.10 74.88 0.10 109.50 88.30 0.15 123.74 97.79 0.20 135.37 106.21 0.25 145.67 114.22 0.30 155.31 121.71 0.35 164.68 128.46 0.40 174.06 134.45 0.45 183.71 139.84 0.50 143.71 144.91 0.55 148.72 149.87 0.60 153.67 154.80 0.65 158.50 159.61 0.70 163.07 164.14 0.75 167.27 168.30 0.80 171.20 172.18 0.85 175.18 176.16 0.90 179.64 180.66 0.95 184.59 185.69 1.00 188.57 189.69 [Numerical Example 5] Normalized phase W1 W2 Wref 0.00 54.95 52.81 0.05 98.35 79.50 0.10 124.57 97.73 0.15 145.10 111.77 0.20 162.45 123.67 0.25 177.90 134.35 0.30 192.49 144.13 0.35 206.58 153.16 0.40 220.21 161.57 0.45 233.98 169.50 0.50 174.74 177.11 0.55 182.23 184.54 0.60 189.58 191.85 0.65 196.81 199.06 0.70 203.91 206.13 0.75 210.86 213.04 0.80 217.67 219.82 0.85 224.46 226.60 0.90 231.36 233.51 0.95 238.38 240.55 1.00 245.05 247.19 [Numerical Example 6] Normalized phase W1 W2 Wref 0.00 45.24 43.48 0.05 88.68 66.44 0.10 112.41 82.23 0.15 130.69 94.19 0.20 145.81 104.04 0.25 159.65 112.59 0.30 172.50 120.22 0.35 184.90 127.12 0.40 131.30 133.44 0.45 137.34 139.34 0.50 143.05 144.96 0.55 148.55 150.41 0.60 153.93 155.75 0.65 159.21 161.01 0.70 164.39 166.16 0.75 169.46 171.21 0.80 174.45 176.18 0.85 179.45 181.18 0.90 184.55 186.30 0.95 189.77 191.56 1.00 194.76 196.52 [Numerical Example 7] Normalized phase W1 W2 Wref 0.00 54.90 52.75 0.05 110.82 82.62 0.10 140.39 102.46 0.15 163.10 117.25 0.20 181.90 129.44 0.25 136.97 199.30 140.09 0.30 146.81 149.64 0.35 155.69 158.28 0.40 163.79 166.18 0.45 171.30 173.54 0.50 178.42 180.55 0.55 185.32 187.39 0.60 192.10 194.14 0.65 198.79 200.82 0.70 205.37 207.39 0.75 211.84 213.84 0.80 218.23 220.22 0.85 224.69 226.70 0.90 231.40 233.46 0.95 238.38 240.52 1.00 245.10 247.25 [Numerical Example 8] Normalized phase W1 W2 Wref 0.00 54.04 51.19 0.05 110.82 87.82 0.10 149.35 109.52 0.15 168.79 124.50 0.20 185.56 136.56 0.25 202.57 147.21 0.30 223.41 156.88 0.35 251.43 165.67 0.40 171.41 173.71 0.45 179.06 181.22 0.50 186.38 188.47 0.55 193.63 195.70 0.60 200.95 203.04 0.65 208.36 210.50 0.70 215.83 218.01 0.75 223.31 225.53 0.80 230.87 233.14 0.85 238.76 241.13 0.90 247.31 249.85 0.95 256.65 259.40 1.00 265.96 268.81 [Numerical Example 9] Normalized phase W1 W2 Wref 0.00 51.76 50.31 0.05 95.26 74.88 0.10 117.82 88.30 0.15 134.20 97.79 0.20 147.73 106.21 0.25 160.17 114.22 0.30 171.97 121.71 0.35 184.15 128.46 0.40 132.61 134.45 0.45 138.17 139.84 0.50 143.35 144.91 0.55 148.37 149.87 0.60 153.33 154.80 0.65 158.17 159.61 0.70 162.75 164.14 0.75 166.97 168.30 0.80 170.91 172.18 0.85 174.89 176.16 0.90 179.33 180.66 0.95 184.26 185.69 1.00 188.24 189.69 [Numerical Example 10] Normalized phase W1 W2 Wref 0.00 55.45 52.81 0.05 105.82 79.50 0.10 134.78 97.73 0.15 157.72 111.77 0.20 177.46 123.67 0.25 195.98 134.35 0.30 213.68 144.13 0.35 230.97 153.16 0.40 158.35 161.57 0.45 166.45 169.50 0.50 174.19 177.11 0.55 181.69 184.54 0.60 189.05 191.85 0.65 196.29 199.06 0.70 203.40 206.13 0.75 210.35 213.04 0.80 217.17 219.82 0.85 223.96 226.60 0.90 230.86 233.51 0.95 237.87 240.55 1.00 244.55 247.19 [Numerical Example 11] Normalized phase W1 W2 Wref 0.00 44.64 43.48 0.05 78.59 66.44 0.10 97.93 82.23 0.15 112.67 94.19 0.20 125.08 104.04 0.25 135.77 112.59 0.30 145.38 120.22 0.35 154.52 127.12 0.40 163.37 133.44 0.45 171.79 139.34 0.50 180.00 144.96 0.55 188.62 150.41 0.60 154.56 155.75 0.65 159.83 161.01 0.70 165.00 166.16 0.75 170.06 171.21 0.80 175.04 176.18 0.85 180.04 181.18 0.90 185.15 186.30 0.95 190.38 191.56 1.00 195.36 196.52 [Numerical Example 12] Normalized phase W1 W2 Wref 0.00 54.13 52.75 0.05 97.99 82.62 0.10 122.34 102.46 0.15 140.66 117.25 0.20 156.06 129.44 0.25 169.31 140.09 0.30 181.28 149.64 0.35 192.76 158.28 0.40 203.97 166.18 0.45 214.76 173.54 0.50 225.37 180.55 0.55 236.64 187.39 0.60 192.83 194.14 0.65 199.52 200.82 0.70 206.10 207.39 0.75 212.56 213.84 0.80 218.94 220.22 0.85 225.41 226.70 0.90 232.14 233.46 0.95 239.15 240.52 1.00 245.87 247.25 [Numerical Example 13] Normalized phase W1 W2 Wref 0.00 52.55 51.19 0.05 103.72 87.82 0.10 129.39 109.52 0.15 147.85 124.50 0.20 163.32 136.56 0.25 176.76 147.21 0.30 189.18 156.88 0.35 201.56 165.67 0.40 214.26 173.71 0.45 227.22 181.22 0.50 240.83 188.47 0.55 256.07 195.70 0.60 202.04 203.04 0.65 209.48 210.50 0.70 216.97 218.01 0.75 224.47 225.53 0.80 232.06 233.14 0.85 240.00 241.13 0.90 248.64 249.85 0.95 258.09 259.40 1.00 267.45 268.81 [Numerical Example 14] Normalized phase W1 W2 Wref 0.00 51.11 50.31 0.05 84.12 74.88 0.10 102.86 88.30 0.15 116.25 97.79 0.20 127.12 106.21 0.25 136.53 114.22 0.30 145.12 121.71 0.35 153.35 128.46 0.40 161.44 134.45 0.45 169.51 139.84 0.50 177.91 144.91 0.55 187.01 149.87 0.60 153.99 154.80 0.65 158.82 159.61 0.70 163.37 164.14 0.75 167.57 168.30 0.80 171.48 172.18 0.85 175.46 176.16 0.90 179.93 180.66 0.95 184.90 185.69 1.00 188.89 189.69 [Numerical Example 15] Normalized phase W1 W2 Wref 0.00 54.52 52.81 0.05 92.49 79.50 0.10 115.89 97.73 0.15 134.45 111.77 0.20 150.51 123.67 0.25 164.72 134.35 0.30 177.73 144.13 0.35 190.13 153.16 0.40 202.13 161.57 0.45 213.63 169.50 0.50 224.83 177.11 0.55 236.28 184.54 0.60 190.04 191.85 0.65 197.27 199.06 0.70 204.37 206.13 0.75 211.30 213.04 0.80 218.11 219.82 0.85 224.90 226.60 0.90 231.80 233.51 0.95 238.82 240.55 1.00 245.48 247.19 [Numerical Example 16] Normalized phase W1 W21 W22 Wref 0.00 49.77 43.48 0.05 90.56 66.44 0.10 113.78 82.23 0.15 131.79 94.19 0.20 146.76 104.04 0.25 160.55 112.59 0.30 144.91 120.22 0.35 154.07 127.12 0.40 162.93 133.44 0.45 171.37 139.34 0.50 179.58 144.96 0.55 188.18 150.41 0.60 154.29 155.75 0.65 159.56 161.01 0.70 164.74 166.16 0.75 169.80 171.21 0.80 174.79 176.18 0.85 179.78 181.18 0.90 184.89 186.30 0.95 190.12 191.56 1.00 195.11 196.52 [Numerical Example 17] Normalized phase W1 W2 Wref 0.00 55.06 52.45 0.05 82.23 68.80 0.10 100.14 80.91 0.15 114.41 90.64 0.20 126.69 98.96 0.25 137.79 106.39 0.30 148.30 113.16 0.35 158.53 119.43 0.40 168.64 125.30 0.45 179.01 130.86 0.50 133.64 136.22 0.55 138.92 141.43 0.60 144.08 146.56 0.65 149.18 151.63 0.70 154.22 156.66 0.75 159.23 161.67 0.80 164.23 166.68 0.85 169.27 171.74 0.90 174.41 176.93 0.95 179.67 182.25 1.00 184.94 187.55 [Numerical Example 18] Normalized phase W1 W2 Wref 0.00 197.21 218.87 0.05 189.84 215.53 0.10 181.74 211.28 0.15 172.76 206.91 0.20 162.88 202.52 0.25 151.85 197.95 0.30 139.35 193.04 0.35 124.72 187.69 0.40 106.23 181.85 0.45 80.47 175.54 0.50 172.55 168.72 0.55 165.47 161.34 0.60 157.78 153.30 0.65 149.40 144.50 0.70 140.21 134.81 0.75 130.08 124.07 0.80 118.83 112.03 0.85 106.03 98.04 0.90 90.74 80.67 0.95 70.93 56.93 1.00 42.72 21.13 Various numerical values ​​in each example are summarized in the following Tables 1 to 3(a) to (c).

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3(a)]

[0084] [Table 3(b)]

[0085] [Table 3(c)]

[0086] 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.

[0087] [Table 4]

[0088] [Optical system] Next, an optical system including the optical elements of each embodiment will be described with reference to FIG. 13. FIG. 13 is an explanatory diagram of an optical system including the optical elements of each embodiment. In FIG. 13, 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. 14, 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. 14 is an explanatory diagram of an imaging device 6 equipped with an optical system including the optical element of each embodiment. In FIG. 14, 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.

[0089] 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.

[0090] The disclosure of each embodiment includes the following configuration. (Configuration 1) A plurality of rings arranged concentrically, a first zone of the plurality of zones includes a plurality of first structures having a first height and a plurality of second structures having a second height different from the first height; The plurality of first structures have different radial widths, An optical element, wherein the plurality of second structures have mutually different widths in the radial direction. (Configuration 2) When the first height is H1 and the second height is H2, 0.05≦H2 / H1≦0.95 2. The optical element according to configuration 1, which satisfies the following condition: (Configuration 3) When the maximum width of the plurality of first structures is Wmax1, the maximum width of the plurality of second structures is Wmax2, the minimum width of the plurality of first structures is Wmin1, and the minimum width of the plurality of second structures is Wmin2, 1.04 <Wmax1 / Wmin1<20.00 1.04 <Wmax2 / Wmin2<20.00 3. The optical element according to configuration 1 or 2, which satisfies the following conditional expression: (Configuration 4) 4. The optical element according to any one of configurations 1 to 3, wherein the plurality of first structures and the plurality of second structures are arranged at the same period in the radial direction. (Configuration 5) When the period is P, the difference between the maximum width and the minimum width of the plurality of first structures is ΔW1, and the difference between the maximum width and the minimum width of the plurality of second structures is ΔW2, 0.05≦ΔW1 / P≦0.80 0.15≦ΔW2 / P≦0.95 5. The optical element according to configuration 4, which satisfies the following condition: (Configuration 6) When the difference between the maximum width and the minimum width of the plurality of first structures is ΔW1 and the difference between the maximum width and the minimum width of the plurality of second structures is ΔW2, 0.05≦ΔW1 / ΔW2≦1.50 6. The optical element according to any one of configurations 1 to 5, which satisfies the following conditional expression: (Configuration 7) When the minimum value of the packing rate of the plurality of first structures is V1min and the maximum value of the packing rate of the plurality of second structures is V2max, 0.70≦V2max / V1min≦1.50 6. The optical element according to configuration 4 or 5, which satisfies the following conditional expression: (Configuration 8) When the maximum value of the aspect ratios of the plurality of first structures is AR1 and the maximum value of the aspect ratios of the plurality of second structures is AR2, 1.50≦AR1≦20.00 1.50≦AR2≦20.00 8. The optical element according to any one of configurations 1 to 7, which satisfies the following conditional expression: (Configuration 9) When the maximum value of the aspect ratios of the plurality of first structures is AR1 and the maximum value of the aspect ratios of the plurality of second structures is AR2, 0.50≦AR2 / AR1≦4.00 9. The optical element according to any one of configurations 1 to 8, which satisfies the following conditional expression: (Configuration 10) When the maximum width of the plurality of first structures is Wmax1 and the maximum width of the plurality of second structures is Wmax2, 0.60≦Wmax2 / Wmax1≦1.20 10. The optical element according to any one of configurations 1 to 9, which satisfies the following conditional expression: (Configuration 11) When the difference between the first height and the second height is ΔH, the design diffraction order is m, and the design wavelength is λ, 0.25≦ΔH / (m×λ0)≦3.00 11. The optical element according to any one of configurations 1 to 10, which satisfies the following conditional expression: (Configuration 12) When a ratio value of a minimum phase in a first region in which the plurality of first structures are arranged to a maximum phase difference in the first annular zone is represented as NP, 0.15≦NP≦0.85 12. The optical element according to any one of configurations 1 to 11, which satisfies the following conditional expression: (Configuration 13) When a ratio value of a minimum phase in a first region in which the plurality of first structures are arranged to a maximum phase difference in the first annular zone is NP, the first height is H1, and the second height is H2, 0.50≦NP / H2×H1≦1.50 13. The optical element according to any one of structures 1 to 12, which satisfies the following conditional expression: (Configuration 14) 14. The optical element according to any one of configurations 1 to 13, wherein an amount of phase modulation by each of the plurality of first structures and the plurality of second structures varies monotonically in a radial direction. (Configuration 15) 15. The optical element according to any one of configurations 1 to 14, wherein an amount of phase modulation by the plurality of first structures is greater than an amount of phase modulation by the plurality of second structures. (Configuration 16) Further comprising a substrate on which the plurality of annular zones are disposed, When the thickness of the substrate is t, 0.0≦H2 / t≦0.1 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.

[0091] 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]

[0092] 215 1st structure 216 Second structure 100 Optical Elements

Claims

1. A plurality of rings arranged concentrically, a first zone of the plurality of zones includes a plurality of first structures having a first height and a plurality of second structures having a second height different from the first height; The first structures have radial widths different from one another, An optical element, characterized in that the widths of the second structures in the radial direction are different from one another.

2. When the first height is H1 and the second height is H2, 0.05≦H2 / H1≦0.95 2. The optical element according to claim 1, which satisfies the following condition:

3. When the maximum width of the plurality of first structures is Wmax1, the maximum width of the plurality of second structures is Wmax2, the minimum width of the plurality of first structures is Wmin1, and the minimum width of the plurality of second structures is Wmin2, 1.04<Wmax1 / Wmin1<20.00 1.04<Wmax2 / Wmin2<20.00 2. The optical element according to claim 1, which satisfies the following condition:

4. The optical element according to claim 1 , wherein the plurality of first structures and the plurality of second structures are arranged at the same period in the radial direction.

5. When the period is P, the difference between the maximum width and the minimum width of the plurality of first structures is ΔW1, and the difference between the maximum width and the minimum width of the plurality of second structures is ΔW2, 0.05≦ΔW1 / P≦0.80 0.15≦ΔW2 / P≦0.95 5. The optical element according to claim 4, which satisfies the following condition:

6. When the difference between the maximum width and the minimum width of the plurality of first structures is ΔW1 and the difference between the maximum width and the minimum width of the plurality of second structures is ΔW2, 0.05≦ΔW1 / ΔW2≦1.50 2. The optical element according to claim 1, which satisfies the following condition:

7. When the minimum value of the packing rate of the first structures is V1min and the maximum value of the packing rate of the second structures is V2max, 0.70≦V2max / V1min≦1.50 5. The optical element according to claim 4, which satisfies the following condition:

8. When the maximum value of the aspect ratios of the plurality of first structures is AR1 and the maximum value of the aspect ratios of the plurality of second structures is AR2, 1.50≦AR1≦20.00 1.50≦AR2≦20.00 2. The optical element according to claim 1, which satisfies the following condition:

9. When the maximum value of the aspect ratios of the plurality of first structures is AR1 and the maximum value of the aspect ratios of the plurality of second structures is AR2, 0.50≦AR2 / AR1≦4.00 2. The optical element according to claim 1, which satisfies the following condition:

10. When the maximum width of the plurality of first structures is Wmax1 and the maximum width of the plurality of second structures is Wmax2, 0.60≦Wmax2 / Wmax1≦1.20 2. The optical element according to claim 1, which satisfies the following condition:

11. When the difference between the first height and the second height is ΔH, the design diffraction order is m, and the design wavelength is λ, 0.25≦ΔH / (m×λ0)≦3.00 2. The optical element according to claim 1, which satisfies the following condition:

12. When a ratio value of a minimum phase in a first region in which the plurality of first structures are arranged to a maximum phase difference in the first annular zone is denoted by NP, 0.15≦NP≦0.85 2. The optical element according to claim 1, which satisfies the following condition:

13. When a ratio value of a minimum phase in a first region in which the plurality of first structures are arranged to a maximum phase difference in the first annular zone is NP, the first height is H1, and the second height is H2, 0.50≦NP / H2×H1≦1.50 2. The optical element according to claim 1, which satisfies the following condition:

14. 2 . The optical element according to claim 1 , wherein an amount of phase modulation by each of the plurality of first structures and the plurality of second structures varies monotonically in a radial direction.

15. 2 . The optical element according to claim 1 , wherein an amount of phase modulation by the plurality of first structures is greater than an amount of phase modulation by the plurality of second structures.

16. Further comprising a substrate on which the plurality of annular zones are disposed, When the thickness of the substrate is t, 0.0≦H2 / t≦0.1 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