Optical element, optical system, lens device, and image pickup device

Abstract

The invention relates to an optical element, an optical system, a lens apparatus, and an image pickup apparatus. The optical element includes a substrate and a plurality of annular portions concentrically arranged on the substrate. The plurality of annular portions includes a first annular portion including a first region provided with a base layer and a second region not provided with the base layer. A plurality of first structures having different widths from each other in the radial direction are arranged in the first region. A plurality of second structures having different widths from each other in the radial direction are arranged in the second region.

Description

Technical Field

[0001] One aspect of the embodiments relates to optical elements, optical systems, lens devices, and image pickup devices. Background Technology

[0002] To reduce the size of optical systems in image pickup devices and the like, an optical element (superlens) is conventionally known, which has a finely uneven (undulating, embossed, or textured) structure formed on the surface of a substrate and utilizes diffraction to provide light converging or diverging effects. Japanese Patent Publication No. 2021-99400 discloses a superlens as a terahertz wave lens.

[0003] To improve the diffraction efficiency (the ratio of light directed to a specific diffraction angle to incident light) of optical elements with finely irregular structures, the repetition period (spacing) of the finely irregular structures can be smaller than the wavelength of the incident light. By changing the shape of the finely irregular structures at each spacing, a smooth phase distribution can be achieved.

[0004] However, as the spacing decreases, the aspect ratio of the fine irregular structure increases, making it difficult to form and maintain the shape of the fine irregular structure. Furthermore, the fine irregular structure may deform due to minor loads, temperatures, pressures, etc. Summary of the Invention

[0005] An optical element according to one aspect of this disclosure includes a substrate and a plurality of annular portions concentrically arranged on the substrate. The plurality of annular portions includes a first annular portion comprising a first region having a base layer and a second region not having a base layer. A plurality of first structures with radially different widths are arranged in the first region. A plurality of second structures with radially different widths are arranged in the second region. Optical systems, lens arrangements, and image acquisition devices all having the above-described optical element also constitute other aspects of this disclosure.

[0006] Further features of various embodiments of this disclosure will become clear from the following description of the embodiments with reference to the accompanying drawings. Attached Figure Description

[0007] Figure 1A , 1B 1C is a construction diagram of the optical element according to each example.

[0008] Figure 2 It is a construction diagram of the optical element based on the comparative example.

[0009] Figure 3 The diagram illustrates the relationship between the shape of the non-flat element of the optical element and the amount of phase modulation in each example.

[0010] Figure 4The diagram illustrates the relationship between the shape of the non-flat element and the amount of phase modulation in the optical element of the comparative example.

[0011] Figure 5A , 5B 5C explains the manufacturing method of the optical element according to each example.

[0012] Figure 6 The offset layer for each example is explained.

[0013] Figure 7 The modulation amount of the normalized phase in the radial direction is explained according to the optical element in each example.

[0014] Figure 8 The width of the non-flat element in the radial direction for each optical element according to each example and comparative example is explained.

[0015] Figure 9A and 9B The component fill rate for each example is explained.

[0016] Figure 10A , 10B 10C and 10D explain the offset of the base layer according to each example.

[0017] Figure 11A , 11B 11C and 11D explain the shape of the non-flat element according to each example.

[0018] Figure 12 It is a construction diagram of the optical element based on Example 16.

[0019] Figure 13A and 13B It is a construction diagram of the optical element based on Example 19.

[0020] Figure 14 An optical system including optical elements according to any of the examples above is explained.

[0021] Figure 15 An image pickup device having optical elements according to any of the above examples is explained. Detailed Implementation

[0022] Embodiments according to the present disclosure will now be described in detail with reference to the accompanying drawings.

[0023] Now for reference Figure 1A , 1B And 1C, will describe the optical element 100 according to each example. Figure 1A , 1B 1C is a structural diagram of optical element 100. Figure 1AThis is an enlarged cross-sectional view of the optical element 100 (on the xz plane) as seen from the y-axis direction. Figure 1B This is a magnified top view of the optical element 100 (on the xy plane) as seen from the z-axis direction (optical axis direction). Figure 1C This is a top-view view of the optical element 100 (on the xy plane) as seen from the z-axis direction (optical axis direction). In each example, the optical axis direction of the optical element 100 and the thickness direction of the substrate 1 are aligned with the z-axis direction.

[0024] According to each example, the optical element 100 includes a substrate 1 and an uneven structure (pillar) 2 formed on the substrate 1. The uneven structure 2 includes a plurality of uneven elements (a plurality of structures) 21 and a base layer 22, the plurality of uneven elements including at least one of recesses or protrusions periodically arranged in the radial direction, the base layer 22 having a substantially constant thickness in the thickness direction (z-axis direction) of the substrate 1. The term "substantially constant" means that although the thickness of the base layer 22 can be as constant as possible, the thickness does not have to be strictly constant due to manufacturing errors, etc. The thickness of the base layer 22 is, for example, within a range that satisfies the following inequality.

[0025] The following inequality (1) must be satisfied:

[0026] 1.00 ≤ A / B < 1.50 (1)

[0027] Where A and B are the maximum and minimum thicknesses of the base layer 22 in substrate 1, respectively.

[0028] Inequality (1) can be replaced by the following inequality (1a):

[0029] 1.00≤A / B<1.20(1a)

[0030] Inequality (1) can be replaced by the following inequality (1b):

[0031] 1.00≤A / B<1.15(1b)

[0032] Inequality (1) can be replaced by the following inequality (1c):

[0033] 1.00≤A / B<1.10(1c)

[0034] Inequality (1) can be replaced by the following inequality (1d):

[0035] 1.00≤A / B<1.05(1d)

[0036] Forming a periodic phase difference (annular portion or ring) in the radial direction of substrate 1 can provide a converging or diverging effect for incident light. Optical element 100 includes a plurality of annular portions, comprising a first annular portion (i-th annular portion) and a second annular portion ((i+1)-th annular portion) arranged radially to extend circumferentially relative to the center of optical element 100. Each of the plurality of annular portions has a region A1 (first region) and a region A2 (second region) arranged radially along optical element 100. In each example, at least one of the plurality of annular portions may have regions A1 and A2, but all annular portions may have regions A1 and A2.

[0037] Multiple non-flat elements (multiple structures) 21 have multiple first structures 215 deployed in region A1 and multiple second structures 216 deployed in region A2. In region A1, the multiple first structures 215 are formed on substrate 1 via a base layer 22. In region A2, the multiple second structures 216 are formed directly on substrate 1 (without a base layer 22). The multiple first structures 215 have different widths in the radial direction. Similarly, the multiple second structures 216 have different widths in the radial direction. However, the widths of the multiple first structures 215 do not have to be all different; some can be the same. The same applies to the widths of the multiple second structures 216.

[0038] Substrate 1 is a transparent flat plate made of synthetic quartz. Substrate 1 can be a plane mirror reflecting incident light, or it can be a curved surface with arbitrary curvature. The material of substrate 1 is not limited to synthetic quartz, but can also be inorganic glass, organic materials such as plastics, ceramics, metals, etc. Uneven structure 2 is formed on the surface of substrate 1 and provides a phase difference to the light passing through uneven structure 2, thereby producing a light converging or diverging effect. Each example achieves a light converging effect almost equivalent to that of a diffractive optical element by forming a phase distribution with a concentric and periodically repeating annular portion of phase difference where 2nπ (n = 1, 2, ..., representing the designed diffraction order or an integer of a diffraction order).

[0039] The uneven structure 2 has an uneven element 21 and a base layer 22. The uneven element 21 is composed of periodically arranged concave or convex portions. In each example, the uneven element 21 is composed of a protruding pillar element made of the dielectric material Si3N4. The shape of the uneven element 21 is not limited to a protruding pillar element, but can be a polygonal prism, a polygonal pyramid, a cone, an arbitrarily concave element, or a combination thereof. The material of the uneven element 21 can be TiO2, GaN, GaP, GaAs, Si, SiC, Al2O3, SiO2, etc.

[0040] The uneven element 21 is a protruding pillar element disposed at the center of a unit segment 11 divided into squares in the radial direction of the substrate 1. Since the width (spacing) of the segment 11 is smaller than the wavelength of the incident light, the light is effectively phase-modulated according to the effective refractive index required to occupy the unit segment (segment) fill rate (element fill rate), regardless of the shape of the uneven element 21. For example, when the incident light is in the visible light range (400 to 700 nm), the spacing (array period) P [nm] can be less than 400 nm, and the spacing P can be further reduced since unwanted diffraction light can be suppressed. The i-th annular portion (i = 1, 2, ...) has regions A1 and A2, where region A1 has an approximately flat base layer 22 disposed between the plurality of uneven elements 21 and the substrate 1, and region A2 does not have an approximately flat base layer 22 disposed between the plurality of uneven elements 21 and the substrate 1.

[0041] The base layer 22 has a substantially constant thickness in the thickness direction of the substrate 1 and is made of Si3N4, the same material as the non-flat element 21 in each example. Regions A1 and A2 in the i-th annular portion each have multiple non-flat elements 21, and each shape has a different width in the radial direction of the substrate 1. This results in a 2nπ phase distribution in the annular portion. In directions orthogonal to the optical axis, RLi and RHi are the radii of regions A1 and A2 in the i-th annular portion starting from the optical axis, respectively. Figure 1C As can be understood, regions A1 and A2 are arranged concentrically and alternately in a direction orthogonal to the optical axis (z-axis), such that RLi <RHi。

[0042] Now for reference Figure 2 The optical element 101 without the base layer 22 according to the comparative example will be described. Figure 2 This is a construction diagram based on the optical element 101 of the comparative example. To form a 2nπ phase distribution within the annular portion, the width (diameter) of the protruding pillar element 21, which serves as the non-flat element 21, is changed, and the element fill rate of the non-flat element 21 within the segment is also changed. That is, the element fill rate decreases sequentially from the protruding pillar element with a large diameter to the protruding pillar element with a small diameter, thus forming the desired phase distribution. Figure 2In the optical element 101 shown, the element fill rate is adjusted only by the diameter of the protruding element, thus significantly altering the diameter. Consequently, the minimum diameter of the protruding element tends to decrease, and the aspect ratio (the ratio of the height to the width of the uneven element 21 (height / width)) tends to increase. For relatively elongated elements with a large aspect ratio, the shape may deform, tilt, or warp under loads applied due to contact or vibration, or under changes in external factors such as temperature or pressure. Therefore, each example reduces the amount of width variation of the uneven element 21 by forming the uneven structure 2 without increasing the aspect ratio by providing a base layer 22 in the annular portion to increase the amount of phase modulation in region A2.

[0043] Figure 3 The diagram illustrates the relationship between the shape of the non-flat element 21 and the phase modulation amount of the optical element 100 according to each example, and relates to the diameter and phase modulation amount of the protruding element as the non-flat element 21. Figure 3 In the diagram, the horizontal axis represents the diameter W of the protruding element (normalized diameter normalized to the segment spacing P), and the vertical axis represents the normalized phase obtained with a 2π normalized phase modulation amount. When the normalized phase is in the range of 0 to 0.54, the normalized diameter of the protruding element in region A2 without the base layer 22 changes from 0.552 to 0.790. When the normalized phase is in the range of 0.54 to 1, the normalized diameter of the protruding element in region A1 with the base layer 22 changes from 0.253 to 0.790. Thus, a phase modulation amount with a normalized phase of 0 to 1 can be obtained, with the maximum aspect ratio AR1 of the uneven element 21 in region A1 being 7.2, and the maximum aspect ratio AR2 of the uneven element 21 in region A2 being 6.6.

[0044] Figure 4 The diagram illustrates the relationship between the shape of the non-flat element 21 of the optical element 101 according to a comparative example and the amount of phase modulation, and also relates to the diameter and phase modulation amount of the protruding element in the optical element 101 without a base layer 22. Figure 4 In the middle, the horizontal axis and the vertical axis are respectively... Figure 3 The horizontal and vertical axes are similar. Figure 4 In order to obtain the phase modulation amount from normalized phase 0 to 1, the normalized diameter will be changed from 0.177 to 0.823, and the maximum aspect ratio will be 20.7, which is larger than the case where a base layer is set. It can be understood that setting a base layer 22 can suppress the aspect ratio of the non-flat element 21.

[0045] Now for reference Figure 5A , 5B Sections 5C and 5C will describe a method for manufacturing the optical element 100 according to each example. The optical element 100 can be manufactured using photolithography. Figure 5A, 5B 5C explains the method for manufacturing optical element 100 and illustrates the steps for manufacturing optical element 100 using nanoimprint lithography. Figure 5A The illustration shows mold 31, whose shape is the inversion of the uneven shape of uneven element 21 formed by electron beam, laser, etc. For example... Figure 5B As shown, resist material 32 is applied to a film 33 deposited on a substrate 1, a mold 31 is pressed, and ultraviolet light is applied to form a reversed shape of the uneven shape of the mold 31 on the resist material 32. Subsequently, as... Figure 5C As shown, the mold 31 is stripped and developed, causing the uneven shape of the resist material 32 to transfer to the film 33, thereby forming an uneven structure 2 on the substrate 1 of the optical element 100. In each example, the method of fabricating the uneven structure 2 is not limited to nanoimprint lithography, and other methods, such as using electron beams, lasers, etc., can be used to directly form the uneven structure 2.

[0046] Figure 6 The offset layer 34 is explained based on each example. For example... Figure 6 As shown, an offset layer 34 can be set to be deployed across regions A1 and A2, instead of as... Figure 5C The uneven structure 2 is formed directly on the substrate 1 as shown. The substrate 1 may include an offset layer 34 and is treated as the substrate 1.

[0047] In each example, the base layer 22 can be made of the same material as the non-flat element 21. For example... Figure 5B As shown, it is relatively easy to prepare a material with a uniform thickness, such as membrane 33. Therefore, when forming the base layer 22 and the uneven structure 2 based on membrane 33, the base layer 22 can be made of the same material as the uneven element 21.

[0048] In each example, the following inequality (2) can be satisfied:

[0049] 0.20≤H1 / H2≤0.90 (2)

[0050] Where H1 is the height (first height) of each of the plurality of first structures 215 in region A1, and H2 is the height (second height) of each of the plurality of second structures 216 in region A2. By satisfying inequality (2), the manufacturing process becomes simpler, and the formation of the non-flat element 21 becomes easier.

[0051] Inequality (2) relates to the shape of the uneven element 21. Since the base layer 22 is deployed in region A1, the phase modulation amount can be increased even if the height H1 of the uneven element 21 in region A1 is lower than the height H1 of the uneven element 21 in region A2. Therefore, a shape with a reduced aspect ratio of the uneven element 21 can be achieved, especially in region A1.

[0052] When the value becomes lower than the lower limit of inequality (2), the height H1 of the uneven element 21 in region A1 becomes relatively low, and the phase modulation amount cannot be increased by changing the width of the uneven element 21 in region A1. At this time, in order to obtain the desired phase modulation amount, the width of the uneven element 21 in region A1 will have to be changed relatively significantly, making it impossible to obtain the effect of reducing the aspect ratio in region A1. In each example, the lower limit of inequality (2) is 0.25, 0.30, 0.32, 0.34, 0.35, 0.36, 0.38, or 0.40.

[0053] On the other hand, when the value becomes higher than the upper limit of inequality (2), the height H2 of the uneven element 21 in region A2 becomes relatively low, and the phase modulation amount cannot be increased when the width of the uneven element 21 in region A2 is changed. At this time, in order to obtain the desired phase modulation amount, the width of the uneven element 21 in region A2 will need to be changed relatively significantly, making it impossible to obtain the effect of reducing the aspect ratio in region A2. The upper limit of inequality (2) can be changed 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.

[0054] In each example, the height H1 of the multiple first structures 215 does not necessarily have to be the same, and can be different from each other. The same applies to the height H2 of the multiple second structures 216.

[0055] In each example, the following inequality (3) can be satisfied:

[0056] 0.80≤(H1+HL) / H2≤1.20 (3)

[0057] Where HL is the height of base layer 22 in region A1. Height HL is, for example, the average height of base layer 22 in region A1. Even if height HL is the minimum height or the maximum height, the following inequality (3) can still be satisfied.

[0058] Inequality (3) relates to the heights of the uneven element 21 and the substrate 22. By satisfying inequality (3), the tip positions of the uneven element 21 in region A1 and region A2 relative to the substrate 1 become approximately equal. Therefore, when forming the uneven structure 2 from a film with uniform thickness, a highly stable uneven structure can be achieved through a simple process. When the value becomes lower than the lower limit of inequality (3), the height H2 of the uneven element 21 in region A2 becomes relatively high, and the effect of reducing the aspect ratio in region A2 cannot be obtained. Furthermore, the difference in the tip positions of the uneven element 21 between regions A1 and A2 increases. Therefore, when forming the uneven structure 2 from a film with uniform thickness, a step of providing a height difference will be included. On the other hand, when the value becomes higher than the upper limit of inequality (3), the height H1 of the uneven element 21 in region A1 becomes relatively high, and the effect of reducing the aspect ratio in region A1 cannot be obtained.

[0059] To further ensure the effectiveness of each example, the lower limit of inequality (3) can be changed 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. The upper limit of inequality (3) can be changed 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.

[0060] When the heights of the uneven element 21 and the base layer 22 have slight undulations in the radial direction of the substrate 1, the average heights of the uneven element 21 and the base layer 22 in the annular portion can satisfy inequality (3). However, in areas where the effect of each example is not desired, such as in unexpected local unevenness caused by manufacturing errors or structures outside the effective portion of the ray, inequality (3) may not be satisfied.

[0061] Regarding light propagating in the thickness direction of substrate 1, the amount of phase modulation (phase delay) caused by the uneven structure 2 may be greater in region A1 than in region A2. Figure 7 The modulation amount of the normalized phase in the radial direction of substrate 1 is explained. Figure 7 In the diagram, the vertical axis represents the normalized phase, and the horizontal axis represents the position in the radial direction. Figure 8 The width of uneven components (e.g., the diameter of a protruding component, etc.) is explained. In Figure 8 In the diagram, the vertical axis represents the width of the uneven element, and the horizontal axis represents its position in the radial direction. Figure 8In the diagram, the structure of the optical element 100 according to each example is shown in solid lines, and the structure of the optical element 101 without the base layer 22 according to the comparative example is shown in dashed lines.

[0062] In each example, the base layer 22 is placed in region A1, and the phase modulation amount is greater than that in region A2. Each example modulates the width of the uneven element in each region so that the change in the width of the uneven element is less than that in the comparative example, thereby suppressing the aspect ratio of the uneven element 21 in regions A1 and A2. When the phase modulation caused by the uneven structure 2 in region A1 is less than that in region A2, the desired phase distribution or aspect ratio suppression effect cannot be obtained unless the change in the width of the uneven element in regions A1 and A2 is configured to be relatively large.

[0063] Now for reference Figure 9A and 9B The component fill rate will be described. Figure 9A and 9B The component fill rate was explained. Figure 9A The illustration shows the component fill rate in region A1 with base layer 22, and Figure 9B The diagram illustrates the component fill rate in region A2, which does not have a base layer 22.

[0064] The component fill rate is the proportion of the volume occupied by the non-flat structure 2 in each segment. For example... Figure 9A and 9B As shown, the element fill rate within the range from the surface position of substrate 1 in region A1 or A2 to the height HL above the surface position of substrate 1 is the ratio of the base layer 22 or uneven element 21 to the volume Vs defined by the bottom surface PxP multiplied by the height HL. Figure 9A and 9B As shown, the element fill rate, ranging from the position of height HL in region A1 or A2 to the tip position of uneven element 21, is the ratio of the base layer 22 or uneven element 21 to the volume Va defined by bottom surface PxP multiplied by height H1.

[0065] It can satisfy at least one of the following inequalities (4) to (6):

[0066] 0.50≤V1s≤1.00 (4)

[0067] 0.80≤V2a / V2s≤1.20 (5)

[0068] 0.20≤V1a / V1s≤0.80 (6)

[0069] Wherein V1s is the maximum value of the component fill rate of the plurality of first structures in region A1 from the surface position (surface) of substrate 1 to the height HL position, V2s is the maximum value of the component fill rate of the plurality of second structures in region A2 from the surface position of substrate 1 to the height HL position, V1a is the maximum value of the component fill rate of the plurality of first structures in region A1 from the height HL position to the tip position (tip) of the uneven structure 2 (structure), and V2a is the minimum value of the component fill rate of the plurality of first structures and the plurality of second structures in regions A1 and A2 respectively from the height HL position to the tip position of the uneven structure 2.

[0070] Inequality (4) relates to the element fill rate of the base layer 22 in region A1. If the value becomes below the lower limit of inequality (4), the desired amount of phase modulation or the effect of suppressing aspect ratio cannot be obtained unless the uneven element widths of regions A1 and A2 change relatively significantly. According to the definition of element fill rate, V1s becomes the maximum value when V1s becomes equal to Vs, and therefore it will never exceed the upper limit of inequality (4). The lower limit of inequality (4) can be 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.

[0071] Inequality (5) relates to the element fill rate in region A2. When the value becomes lower than the lower limit of condition (5), V2s becomes relatively large, and the desired amount of phase modulation or the effect of suppressing aspect ratio cannot be obtained unless the width of the uneven element in region A2 is significantly changed. On the other hand, when the value becomes higher than the upper limit of inequality (5), V2a becomes relatively large, and the desired amount of phase modulation or the effect of suppressing aspect ratio cannot be obtained unless the width of the uneven element 21 in region A1 is significantly changed. To further ensure the effect of each example, the lower limit of inequality (5) can be changed to 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, or 0.96. The upper limit of inequality (5) can be changed to 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, or 1.02.

[0072] Inequality (6) relates to the element fill rate in region A1. When the value becomes below the lower limit of inequality (6), V1s becomes relatively large, and the desired amount of phase modulation or the effect of suppressing aspect ratio cannot be obtained unless the width of the non-flat element 21 in region A2 is significantly changed. On the other hand, when the value becomes above the upper limit of inequality (6), V1a becomes relatively large, and the desired amount of phase modulation or the effect of suppressing aspect ratio cannot be obtained unless the width of the non-flat element 21 in region A1 is significantly changed. To further ensure the effect of each example, the lower limit of inequality (6) can be changed to 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.30. The upper limit of inequality (6) can be changed to 0.78, 0.76, 0.74, 0.72, 0.70, 0.68, 0.66, or 0.65.

[0073] In each example, the following inequalities (7) and (8) can be satisfied:

[0074] 1.05≤Wmax1 / Wmin1≤6.00 (7)

[0075] 1.05≤Wmax2 / Wmin2≤6.00 (8)

[0076] Where Wmax1 is the maximum width of the uneven element 21 in region A1 (the maximum diameter of the cylinder among the multiple first structures), Wmin1 is the minimum width of the uneven element 21 in region A1 (the minimum diameter of the cylinder among the multiple first structures), Wmax2 is the maximum width of the uneven element 21 in region A2 (the maximum diameter of the cylinder among the multiple second structures), and Wmin2 is the minimum width of the uneven element 21 in region A2 (the minimum diameter of the cylinder among the multiple second structures).

[0077] Inequalities (7) and (8) relate to the shape of the uneven element 21 in regions A1 and A2, respectively. When the value becomes lower than the lower limit of each of inequalities (7) and (8), the phase modulation becomes relatively large due to the slight change in the width of the uneven element, the influence of the manufacturing change increases when forming the uneven structure 2, and manufacturing becomes difficult. On the other hand, when the value becomes higher than the upper limit of each of inequalities (7) and (8), the amount of change in the width of the uneven element increases, and the effect of suppressing aspect ratio cannot be obtained.

[0078] To further ensure the effectiveness of each example, the lower bound of inequality (7) can be changed to 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, or 1.45. The upper bound of inequality (7) can be changed to 5.50, 5.00, 4.50, 4.00, or 3.50.

[0079] To further ensure the effectiveness of each example, the lower limit of inequality (8) can be changed 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. The upper limit of inequality (8) can be changed to 5.50, 5.00, 4.50, 4.00, 3.50, 3.00, 2.50, 2.00, 1.80, 1.70, or 1.60.

[0080] In each example, the phase modulation of the non-flat element 21 in regions A1 and A2 can monotonically increase or decrease along the radial direction of the substrate 1 within the annular portion. That is, in each of the plurality of annular portions, a plurality of first structures 215 and a plurality of second structures 216 are configured such that the phase of light passing through the non-flat structure 2 monotonically increases or decreases in the radial direction. When the phase modulation increases or decreases discretely, the width of the non-flat element will change relatively significantly, and the effect of suppressing aspect ratio cannot be obtained. In the case where the optical element 100 according to each example has a light-converging effect when the plane wave enters in the thickness direction of the substrate 1, the phase modulation within the annular portion shows that the phase delay monotonically decreases from the inside to the outer periphery of the substrate 1 in the radial direction. Furthermore, in the case where the optical element 100 according to each example has a light-diverging effect, the phase modulation within the annular portion shows that the phase delay monotonically increases from the inside to the outer periphery of the substrate.

[0081] In each example, the following inequality (9) can be satisfied:

[0082] 0.35≤AR1 / AR2≤2.00 (9)

[0083] AR1 is the maximum aspect ratio of the non-flat element 21 in region A1, and AR2 is the maximum aspect ratio of the non-flat element 21 in region A2.

[0084] Inequality (9) relates to the shape of the uneven element 21. When the value becomes lower than the lower limit of inequality (9), the change in the width of the uneven element in region A2 increases, and the effect of suppressing the aspect ratio in region A2 cannot be obtained. On the other hand, when the value becomes higher than the upper limit of inequality (9), the change in the width of the uneven element in region A1 increases, and the effect of suppressing the aspect ratio in region A1 cannot be obtained.

[0085] To further ensure the effectiveness of each example, the lower bound of inequality (9) can be changed to 0.36, 0.38, 0.40, 0.42, 0.43, or 0.44. The upper bound of inequality (9) can be changed to 1.90, 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.25, or 1.20.

[0086] In each example, the following inequalities (10) and (11) can be satisfied:

[0087] 1.50≤A1≤20.00 (10)

[0088] 1.50≤A2≤20.00 (11)

[0089] Inequalities (10) and (11) relate to the shape of the uneven element 21 in regions A1 and A2. When the value becomes lower than the lower limit of each of inequalities (10) and (11), the phase modulation becomes relatively large even with a slight change in the width of the uneven element, increasing the impact of the manufacturing variation when forming the uneven structure 2 and making manufacturing difficult. On the other hand, when the value becomes higher than the upper limit of each of inequalities (10) and (11), the aspect ratio increases, and the structure may collapse due to external factors.

[0090] To further ensure the effectiveness of each example, the lower bounds of inequalities (10) and (11) can be changed to 2.00, 3.00, 3.40, 3.80, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00, or 5.20. The upper bounds of inequalities (10) and (11) can be changed to 18.00, 16.00, 15.00, 14.00, 13.0, 12.0, 11.0, 10.0, 9.0, or 8.0.

[0091] In the optical element 100 according to each example, the phase distribution depends on the reference wavelength λ0. The following inequality (12) can be satisfied:

[0092] 0.50≤H2 / λ0≤4.00 (12)

[0093] Inequality (12) relates to the shape of the uneven structure 2. Regarding the phase distribution, the annular portion is determined based on the phase relative to the reference wavelength λ0. When the value becomes lower than the lower limit of inequality (12), the change in the width of the uneven element increases, and the effect of suppressing the aspect ratio in region A2 cannot be obtained. On the other hand, when the value becomes higher than the upper limit of inequality (12), the aspect ratio increases, and the structure may collapse due to external factors.

[0094] To further ensure the effectiveness of each example, the lower bound of inequality (12) can be changed to 0.60, 0.70, 0.80, 0.90, 0.95, or 1.00. The upper bound of inequality (12) can be changed to 3.80, 3.60, 3.40, 3.20, 3.00, 2.80, 2.60, 2.40, 2.20, or 2.00.

[0095] The following inequality (13) can be satisfied based on the optical element 100 in each example:

[0096] 0.15≤Wmin1 / Wmin2≤4.00 (13)

[0097] Inequality (13) relates to the shape of the uneven element 21. When the value becomes lower than the lower limit of inequality (13), the width of the uneven element in region A1 becomes relatively small, and it becomes difficult to achieve the effect of suppressing the aspect ratio in region A1. On the other hand, when the value becomes higher than the upper limit of inequality (13), the width of the uneven element in region A2 becomes relatively small, and it becomes difficult to achieve the effect of suppressing the aspect ratio in region A2.

[0098] To further ensure the effectiveness of each example, the lower bound of inequality (13) can be changed to 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, or 0.29. The upper bound of inequality (13) can be changed to 3.75, 3.50, 3.25, 3.00, 2.75, 2.50, or 2.25.

[0099] The following inequality (14) can be satisfied:

[0100] 0.70≤Wmax1 / Wmax2≤1.40 (14)

[0101] Inequality (14) relates to the shape of the uneven element 21. When the value becomes lower than the lower limit of inequality (14), the maximum width of the uneven element 21 in region A1 becomes relatively small. Therefore, in order to change the predetermined normalized phase in region A1, the minimum width of the uneven element 21 will decrease, and it becomes difficult to achieve the effect of suppressing aspect ratio. On the other hand, when the value becomes higher than the upper limit of inequality (14), the maximum width of the uneven element 21 in region A2 becomes relatively small. Therefore, in order to change the predetermined normalized phase in region A2, the minimum width of the uneven element 21 will decrease, and it becomes difficult to achieve the effect of suppressing aspect ratio in region A2.

[0102] To further ensure the effect for each example, the lower bound of inequality (14) can be changed to 0.74, 0.78, 0.82, 0.84, 0.85, 0.86, or 0.87. The upper bound of inequality (14) can be changed to 1.36, 1.32, 1.30, 1.28, 1.26, 1.24, 1.22, or 1.20.

[0103] The following inequality (15) can be satisfied:

[0104] 0.10≤P / H2≤0.60 (15)

[0105] Inequality (15) relates to the shape and segment shape of the uneven element 21. When the value becomes lower than the lower limit of inequality (15), the segment of the uneven element 21 becomes relatively small, and the slight change in the width of the uneven element increases the phase modulation. As a result, the influence of manufacturing variations increases when forming the uneven structure 2, and manufacturing becomes difficult. On the other hand, when the value becomes higher than the upper limit of inequality (15), the height of the uneven element 21 in region A2 becomes higher, and it becomes difficult to sufficiently achieve the effect of suppressing aspect ratio.

[0106] To further ensure the effectiveness of each example, the lower bound of inequality (15) can be changed to 0.12, 0.14, 0.15, 0.16, 0.17, or 0.18. The upper bound of inequality (15) can be changed to 0.58, 0.56, 0.54, 0.52, 0.50, 0.48, 0.46, 0.44, or 0.42.

[0107] The following inequality (16) can be satisfied:

[0108] 0.15≤E / n≤0.95 (16)

[0109] Where E is the normalized phase at the boundary between regions A1 and A2 in the same annular section, and n is the designed diffraction order.

[0110] Inequality (16) relates to the normalized phase of the diffraction effect. When the value becomes lower than the lower limit of inequality (16), the change in the normalized phase in region A1 increases, the change in the width of the uneven element 21 in region A1 increases, and it becomes difficult to achieve the effect of suppressing the aspect ratio. On the other hand, when the value becomes higher than the upper limit of inequality (16), the change in the normalized phase in region A2 increases, the change in the width of the uneven element 21 in region A2 increases, and it becomes difficult to achieve the effect of suppressing the aspect ratio.

[0111] To further ensure the effectiveness of each example, the lower bound of inequality (16) can be changed to 0.16, 0.20, 0.24, 0.28, 0.30, 0.32, 0.34, 0.36, or 0.38. The upper bound of inequality (16) can be changed 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.

[0112] In each example, the following inequality (17) can be satisfied:

[0113] 0.00≤H2 / t≤0.10 (17)

[0114] Where t is the thickness of substrate 1 in the optical axis direction.

[0115] Inequality (17) relates to the shape of the optical element 100. The height H2 of the uneven element 21 in region A2 and the thickness t of the substrate 1 are both length-indicating values ​​and are greater than zero. Therefore, the value will never fall below the lower limit of inequality (17). If the value becomes higher than the upper limit of inequality (17), the substrate becomes relatively thin, and deformation due to its own weight cannot be suppressed when the substrate is held by the holder, or the substrate may deform during manufacturing using photolithography.

[0116] To further ensure the effectiveness of each example, the lower limit of inequality (17) can be changed to 0.000001, 0.000005, 0.00001, or 0.0001. The upper limit of inequality (17) can be changed to 0.08, 0.06, 0.04, 0.02, 0.01, 0.008, 0.006, or 0.004.

[0117] The following inequality (18) can be satisfied:

[0118] 0.00≤S / P≤0.40 (18)

[0119] Where S is the boundary between regions A1 and A2 in the same annular portion, and is the length from the boundary between the segments arranged at a spacing P to the end of the base layer 22 in a direction orthogonal to the thickness direction of the substrate 1 (i.e., in a direction orthogonal to the optical axis).

[0120] Inequality (18) relates to the shape of base layer 22. Now refer to Figures 10A to 10D The offset of base layer 22 will be described. Figures 10A to 10D The offset of base layer 22 is explained.

[0121] like Figure 10AAs shown, the boundary between regions A1 and A2 in the same annular portion is ensured by offsetting the end of the substrate 22 from the segment boundary by a length S in a direction orthogonal to the optical axis, thus ensuring sufficient distance between the uneven element 21 in region A2 and the substrate 22. Therefore, when forming the uneven element 21 using photolithography, the distance (spacing) between the uneven elements 21 or the distance between the uneven element 21 and the substrate 22 can be ensured to be relatively wide, and the process can be simplified.

[0122] Figure 10B This is an xy-plane diagram at the boundary between regions A1 and A2 in the first annular portion of Example 18, which will be described below. Each segment is a square with a side length P, and the center coordinates (x, y) of the segment are ((j-0.5)×P, (k-0.5)×P), where each of i and k is an integer. In a segment including an uneven element 211 that contacts region A1 at one vertex of the segment, the base layer can be offset by S from the segment vertex that contacts region A1 in each of the x and y directions. In a segment including an uneven element 212 that contacts region A1 on one side of the segment, the base layer can be offset by S from the segment edge that contacts region A1 in either the x or y direction. In a segment including an uneven element 213 that contacts region A1 at one vertex and on both sides of the segment, the base layer can be offset by S from each segment edge that contacts region A1 in each of the x and y directions. In a segment where the base layer 22 is offset, the amount of phase change of light as it passes through the segment differs from that in the case where the segment is not offset, and the width of the uneven element will change according to the offset length S.

[0123] Figure 10C The illustration shows the normalized diameter obtained by normalizing the diameter of the protruding pillar element 21, which is the uneven element 21, using the segment spacing P, and the amount of change in the normalized phase considering the offset of the base layer 22. The segment including the uneven element 211 will be referred to as region A11, the segment including the uneven element 212 will be referred to as region A12, and the segment including the uneven element 213 will be referred to as region A13. It can be understood that in order to obtain the same normalized phase as region A1, which does not have the offset of the base layer 22, the normalized diameter will be changed in regions A11, A12, and A13. Since regions A11, A12, and A13 are located at the boundary between regions A1 and A2 in the same annular portion, the value of the normalized phase of the normalized diameter at the position corresponding to the boundary between regions A1 and A2 is illustrated.

[0124] like Figure 10D As shown, at the boundary between regions A1 and A2 in adjacent annular portions, the width of the non-flat element in region A2 is configured to be relatively narrow, ensuring a sufficient distance from the base layer 22. Therefore, the end of the base layer 22 in region A1 does not need to offset from the segment boundary.

[0125] The offset length S and the spacing P are both numerical values ​​indicating length, and since they are values ​​greater than or equal to 0, the values ​​will never fall below the lower limit of inequality (18). If the values ​​become higher than the upper limit of inequality (18), the desired normalized phase cannot be obtained unless the width of the uneven element of the segment offsetting the base layer 22 is made relatively large. At this point, a sufficient distance from the end of the uneven element 21 to the offset end of the base layer 22 cannot be ensured, and manufacturing becomes difficult. Furthermore, manufacturing becomes difficult due to the overhanging shape extending beyond the end of the uneven element from the end of the base layer.

[0126] To further ensure the effectiveness of each example, the lower limit of inequality (18) can be changed to 0.005, 0.01, 0.02, 0.04, 0.05, 0.06, 0.07, or 0.08. The upper limit of inequality (18) can be changed to 0.36, 0.32, 0.28, 0.24, 0.20, 0.18, 0.16, 0.14, or 0.12.

[0127] The optical element 100 according to each embodiment will now be described in detail.

[0128] Figure 11A , 11B 11C and 11D explain the shape of the non-flat element 21. Figure 11A The uneven element 21 shown is a convex cylindrical element, and the width Wa of the uneven element is the diameter of the cylinder. Figure 11B The uneven element 21 shown is a convex rectangular (quadrilateral) prism element, and the width Wb of the uneven element is the length of the side of the rectangular prism in the direction orthogonal to the optical axis. Figure 11C The uneven element 21 shown is a concave cylindrical element, and the width Wc of the uneven element is the diameter of the hollow cylinder. Figure 11D The uneven element 21 shown has a convex cross-shaped prism element, and the widths WS and WL of the uneven element can be the lengths shown in the figure.

[0129] The optical element according to Example 1 has a non-flat structure, comprising a substrate made of synthetic quartz with a thickness of 0.775 mm, protruding elements made of Si3N4, and a base layer with a uniform film thickness. For each square segment with a side length of 240 nm, non-flat elements are arranged in regions A1 and A2, having heights of 440 nm and 880 nm respectively, and the base layer has a height of 440 nm. This non-flat structure has… The effective diameter, 105 annular sections with a 2π phase difference repeating periodically at a wavelength of 500 nm, and a focal length of 40.0 mm are used. The position with a normalized phase of 0.54 is set as the boundary between regions A1 and A2 in the annular section, and the maximum aspect ratios in regions A1 and A2 are 7.24 and 6.64, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 20.7 in Reference Example 1 without a base layer.

[0130] The optical element according to Example 2 has a non-flat structure, comprising a substrate made of synthetic quartz with a thickness of 0.775 mm, protruding elements made of Si3N4, and a base layer with a uniform film thickness. For each square segment with a side length of 300 nm, non-flat elements are arranged in regions A1 and A2, having heights of 500 nm and 1000 nm respectively, and the base layer has a height of 500 nm. This non-flat structure has… The effective diameter, 67 annular sections with a 2π phase difference periodically repeating at a wavelength of 587.6 nm, and a focal length of 20.0 mm are used. The boundary between regions A1 and A2 in the annular section is set at a normalized phase of 0.59, and the maximum aspect ratios in regions A1 and A2 are 4.46 and 6.29, respectively. Therefore, the aspect ratio is suppressed compared to the maximum aspect ratio of 18.9 in Reference Example 2 without a base layer.

[0131] The optical element according to Example 3 has a non-flat structure, comprising a substrate made of synthetic quartz with a thickness of 0.775 mm, protruding elements made of Si3N4, and a base layer with a uniform film thickness. For each square segment with a side length of 320 nm, non-flat elements are arranged in regions A1 and A2, having heights of 800 nm and 1600 nm respectively, and the base layer has a height of 800 nm. This non-flat structure has… The effective diameter, 79 annular sections with a 4π phase difference that repeat periodically at a wavelength of 500 nm, and a focal length of 10.0 mm are used. The position with a normalized phase of 0.80 is set as the boundary between regions A1 and A2 in the annular section, and the maximum aspect ratios in regions A1 and A2 are 5.88 and 9.80, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 21.3 in Reference Example 3 without a base layer.

[0132] The optical element according to Example 4 has an uneven structure, comprising a substrate made of synthetic quartz with a thickness of 0.775 mm, protruding TiO2 elements, and a base layer with a uniform film thickness. For each square segment with a side length of 240 nm, uneven elements are arranged in regions A1 and A2, having heights of 300 nm and 600 nm respectively, and the base layer has a height of 300 nm. This uneven structure has… The effective diameter, 307 annular sections with a 2π phase difference that repeat periodically at a wavelength of 587.6 nm, and a focal length of 100.0 mm are used. The position with a normalized phase of 0.65 is set as the boundary between regions A1 and A2 in the annular section, and the maximum aspect ratios in regions A1 and A2 are 3.55 and 7.01, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 39.3 in Reference Example 4 without a base layer.

[0133] The optical element according to Example 5 has an uneven structure, comprising a substrate made of synthetic quartz with a thickness of 2.0 mm, Al2O3 protruding elements, and a base layer with a uniform film thickness. For each square segment with a side length of 300 nm, uneven elements are arranged in regions A1 and A2, having heights of 700 nm and 1400 nm respectively, and the base layer has a height of 700 nm. This uneven structure has… The effective diameter, 348 annular sections with a 2π phase difference periodically repeating at a wavelength of 486.1 nm, and a focal length of 41.7 mm are all considered. The boundary between regions A1 and A2 in the annular section is set at a normalized phase of 0.60, and the maximum aspect ratios in regions A1 and A2 are 5.68 and 8.84, respectively. Therefore, the aspect ratio is suppressed compared to the maximum aspect ratio of 26.4 in Reference Example 5 without a substrate.

[0134] The optical elements according to Examples 6 to 10 have similar specifications to those according to Examples 1 to 5, except that the height of the uneven element in region A1 is different from the height of the substrate.

[0135] According to Example 6, the heights of the uneven element and the substrate in region A1 of the optical element are 352 nm and 528 nm, respectively. The position with a normalized phase of 0.58 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 5.02 and 5.83, respectively.

[0136] According to Example 7, the heights of the uneven element and the substrate in region A1 of the optical element are 400 nm and 600 nm, respectively. The position with a normalized phase of 0.70 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 7.90 and 7.58, respectively.

[0137] According to Example 8, the heights of the uneven element and the substrate in region A1 of the optical element are 640 nm and 960 nm, respectively. The position with a normalized phase of 1.40 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 5.32 and 12.47, respectively.

[0138] According to Example 9, the heights of the uneven element and the substrate in region A1 of the optical element are 240 nm and 360 nm, respectively. The position with a normalized phase of 0.68 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 2.63 and 5.36, respectively.

[0139] According to Example 10, the heights of the uneven element and the substrate in region A1 of the optical element are 560 nm and 840 nm, respectively. The position with a normalized phase of 0.58 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 9.86 and 7.97, respectively.

[0140] The optical elements according to Examples 11 to 15 have similar specifications to those according to Examples 1 to 5, except that the height of the uneven element and the height of the base layer in region A1 are different.

[0141] According to Example 11, the heights of the uneven element and the substrate in region A1 of the optical element are 528 nm and 352 nm, respectively. The position with a normalized phase of 0.55 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 6.49 and 7.94, respectively.

[0142] According to Example 12, the heights of the uneven element and the substrate in region A1 of the optical element are 600 nm and 400 nm, respectively. The position with a normalized phase of 0.60 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 8.29 and 13.77, respectively.

[0143] According to Example 13, the heights of the uneven element and the substrate in region A1 of the optical element are 960 nm and 640 nm, respectively. The position with a normalized phase of 1.60 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 5.37 and 15.92, respectively.

[0144] According to Example 14, the heights of the uneven element and the substrate in region A1 of the optical element are 360 ​​nm and 240 nm, respectively. The position with a normalized phase of 0.60 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 3.62 and 11.99, respectively.

[0145] According to Example 15, the heights of the uneven element and the substrate in region A1 of the optical element are 840 nm and 560 nm, respectively. The position with a normalized phase of 0.60 is set as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 7.50 and 11.22, respectively.

[0146] The optical element according to Example 16 has similar specifications to the optical element according to Example 1, except that the height of the uneven element in region A1 and the structure of the substrate are different. Figure 12 The optical element 100 according to Example 16 is explained. (As...) Figure 12 As shown, the heights H11 and H12 of the uneven element 21 and the heights HL1 and HL2 of the base layer 22 have different structures, and the heights of the uneven element 21 are 352 nm and 528 nm, and the heights of the base layer 22 are 528 nm and 352 nm. The positions of the base layer 22 with different heights in region A1 of the annular portion are positions with a normalized phase of 0.78, and the boundary between regions A1 and A2 is a position with a normalized phase of 0.40. The maximum aspect ratios in region A1 are 3.07 and 5.29, and the maximum aspect ratio in region A2 is 6.37.

[0147] The optical element according to Example 17 has similar specifications to the optical element according to Example 1, except that the non-flat element in region A2 is a convex rectangular (quadrilateral) prism element with a square-cut surface in a plane orthogonal to the optical axis. Example 17 sets the region with a normalized phase of 0.60 as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 7.33 and 8.05, respectively. Compared to the maximum aspect ratio of 14.6 in Reference Example 6 without a base layer, the aspect ratio is suppressed.

[0148] The optical element according to Example 18 has similar specifications to the optical element according to Example 1, except that the base layer boundary is offset from the segment boundary by 24 nm at the boundary between regions A1 and A2 in the same annular portion. By offsetting the base layer boundary, the minimum distance between the base layer end and the non-flat element in region A2 is changed from 25.2 nm to 49.2 nm, and manufacturing becomes easier.

[0149] Example 18 sets the position with a normalized phase of 0.54 as the boundary between regions A1 and A2 in the annular portion, and the maximum aspect ratios in regions A1 and A2 are 7.24 and 6.64, respectively. This example sets the offset length S to 24 nm, but the value can be changed to 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, etc., as long as non-flat elements can be configured.

[0150] The optical element according to Example 19 has a non-flat structure, which includes a substrate made of synthetic quartz with a thickness of 0.775 mm, a concave cylindrical element made of Si3N4, and a base layer having a uniform film thickness. Figure 13A It is a cross-sectional view of the optical element 100 in the xz plane according to Example 19, and Figure 13B This is a cross-sectional view of the optical element 100 in the xy plane according to Example 19. For each square segment with a side length of 300 nm, non-flat elements in regions A1 and A2 are arranged, and they have heights of 600 nm and 1200 nm respectively, and the height of the substrate is 600 nm. The non-flat structure has The effective diameter, 105 annular sections with a 2π phase difference that repeat periodically at a wavelength of 500 nm, and a focal length of 40.0 mm are used. The position with a normalized phase of 0.65 is set as the boundary between regions A1 and A2 in the annular section, and the maximum aspect ratios in regions A1 and A2 are 11.98 and 7.06, respectively. Therefore, the aspect ratio can be suppressed compared to the maximum aspect ratio of 28.2 in Reference Example 7 without a base layer.

[0151] The following illustrations show the numerical values ​​corresponding to the optical elements according to Examples 1 to 19. The phase indicates the light converging and diverging effects of the non-flat structure. The expression is as follows:

[0152]

[0153] Where h is the height of the optical axis in the direction orthogonal 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...) are the phase coefficients of each order.

[0154] nd, ng, nC, nF, and n500 are the refractive indices for the d-line (587.6 nm), g-line (435.8 nm), F-line (486.1 nm), and C-line (656.3 nm), respectively, and for a wavelength of 500 nm. W1[nm] and W2[nm] are the widths of the uneven elements in regions A1 and A2, respectively, and Wref[nm] is the width of the uneven element in the comparative example.

[0155] Numerical Example 1

[0156]

[0157]

[0158] Numerical Example 2

[0159]

[0160] Numerical Example 3

[0161]

[0162] Numerical Example 4

[0163]

[0164]

[0165] Numerical Example 5

[0166]

[0167]

[0168] Numerical Example 6

[0169]

[0170]

[0171] Numerical Example 7

[0172]

[0173]

[0174] Numerical Example 8

[0175]

[0176] Numerical Example 9

[0177]

[0178] Numerical Example 10

[0179]

[0180]

[0181] Numerical Example 11

[0182]

[0183]

[0184] Numerical Example 12

[0185]

[0186]

[0187] Numerical Example 13

[0188]

[0189]

[0190] Numerical Example 14

[0191]

[0192] Numerical Example 15

[0193]

[0194] Numerical Example 16

[0195]

[0196]

[0197] Numerical Example 17

[0198]

[0199]

[0200] Numerical Example 18

[0201]

[0202]

[0203] Numerical Example 19

[0204]

[0205]

[0206] Tables 1 through 3C summarize the various values ​​for each example.

[0207] Table 1

[0208] <![CDATA[Si3N4]]> <![CDATA[TiO2]]> <![CDATA[Al2O3]]> Synthetic Quartz ng 2.08394 2.48181 1.63759 1.46240 nF 2.06710 2.42034 1.63053 1.45876 nd 2.04580 2.35281 1.62153 1.45345 nC 2.03665 2.32645 1.61759 1.45084 n500 2.06337 2.40780 1.62896 1.45790

[0209] Table 2

[0210]

[0211] Table 3A

[0212]

[0213]

[0214]

[0215] Table 3B

[0216]

[0217]

[0218]

[0219] Table 3C

[0220]

[0221]

[0222]

[0223] Table 4 illustrates the numerical values ​​of the uneven structures according to the comparative examples (refer to Examples 1 to 7) corresponding to the optical elements of each example.

[0224] Table 4

[0225]

[0226] Optical system

[0227] Now for reference Figure 14 An optical system comprising an optical element according to any of the examples above will be described. Figure 14 An optical system comprising optical elements according to any of the examples above has been explained. Figure 14 In the figures, reference numeral 100 denotes an optical element according to any of the above examples, reference numeral 102 denotes a lens element, OA denotes the optical axis, IP denotes the image plane, and reference numeral 3 denotes an optical system including an optical element according to any of the above examples. Lens elements include lenses, diffractive optical elements, mirrors, etc., and the number of lens elements is not limited. Optical element 100 and lens element 102 are arranged along the optical axis OA to image incident light onto the image plane IP. Uneven elements deployed on the image-side surface of optical element 100 can provide light converging or diverging effects.

[0228] Image pickup device

[0229] Now for reference Figure 15 The following will now describe a digital still camera (image acquisition device) that uses an optical system comprising optical elements according to any of the examples above as an imaging optical system. Figure 15 An image pickup device 6 having an optical system including optical elements according to any of the examples above is explained. Figure 15In the figures, reference numeral 4 denotes the camera body, and reference numeral 3 denotes an optical system including optical elements according to any of the examples described above. Reference numeral 5 denotes an image sensor (photoelectric conversion element), such as a CCD sensor or a CMOS sensor, built into the camera body 4, that receives the optical image formed by the optical system 3 and performs photoelectric conversion on it. The camera body 4 can be a so-called single-lens reflex camera with a fast-return mirror, or a so-called mirrorless camera without a fast-return mirror. Applying an optical system including optical elements according to each example in this way to an image acquisition device such as a digital still camera can provide an image acquisition device with a small lens.

[0230] Therefore, according to one aspect of the example, the optical element includes a plurality of annular portions concentrically arranged on a substrate. The plurality of annular portions includes a first annular portion comprising a first region having a substrate and a second region not having a substrate. A plurality of first structures with radially different widths are arranged in the first region. A plurality of second structures with radially different widths are arranged in the second region. Thus, each example can provide an optical element, an optical system, a lens assembly, and an image pickup device, each having a highly stable, finely uneven structure.

[0231] While this disclosure describes exemplary embodiments, it should be understood that some embodiments are not limited to the disclosed embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. An optical element, comprising: substrate; as well as A plurality of annular portions are concentrically arranged on a substrate, The invention is characterized in that the plurality of annular parts include a first annular part, the first annular part includes a first area provided with a base layer and a second area not provided with a base layer, wherein a plurality of first structures having different widths in a radial direction are arranged in the first region, and A plurality of second structures having different widths in the radial direction are arranged in the second region.

2. The optical element according to claim 1, characterized in that The base layer is made of the same material as that of the plurality of first structures.

3. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.20≤H1 / H2≤0.90 Wherein H1 is the height of each of the plurality of first structures, and H2 is the height of each of the plurality of second structures.

4. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.80≤(H1+HL) / H2≤1.20 Wherein H1 is the height of each of the plurality of first structures, H2 is the height of each of the plurality of second structures, and HL is the height of the base layer.

5. The optical element according to claim 1, characterized in that The phase delay amount caused by the plurality of first structures to light perpendicularly incident on the surface of the substrate is greater than the phase delay amount caused by the plurality of second structures to the light.

6. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.50≤V1s≤1.00 0.80≤V2a / V2s≤1.20 Wherein HL is the height of the base layer, V1s is the maximum value of the filling rate of the multiple first structures in the range from the surface of the substrate to the height HL, V2s is the maximum value of the filling rate of the multiple second structures in the range from the surface of the substrate to the height HL, and V2a is the maximum value of the filling rate of the multiple first structures and the multiple second structures in the range from the position at the height HL to the corresponding tips among the tips of the multiple first structures and the multiple second structures.

7. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.20≤V1a / V1s≤0.80 Wherein HL is the height of the base layer, V1s is the maximum filling rate of the plurality of first structures in the range from the surface of the substrate to the height HL, and V1a is the maximum filling rate of the plurality of first structures in the range from the position at the height HL to the tips of the plurality of first structures.

8. The optical element according to claim 1, characterized in that The following inequality is satisfied: 1.05≤Wmax1 / Wmin1≤6.00 1.05≤Wmax2 / Wmin2≤6.00 Wherein Wmax1 and Wmin1 are the maximum width and the minimum width of the plurality of first structures, respectively, and Wmax2 and Wmin2 are the maximum width and the minimum width of the plurality of second structures, respectively.

9. The optical element according to claim 1, characterized in that The phase modulation amount caused by each of the plurality of first structures and the plurality of second structures varies monotonically in the radial direction.

10. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.35≤AR1 / AR2≤2.00 Wherein AR1 is the maximum value of the aspect ratios of the plurality of first structures, and AR2 is the maximum value of the aspect ratios of the plurality of second structures.

11. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.50≤H2 / λ0≤4.00 Wherein H2 is the height of each of the plurality of second structures, and λ0 is the reference wavelength.

12. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.70≤Wmax1 / Wmax2≤1.40 Wherein Wmax1 is the maximum width of the plurality of first structures, and Wmax2 is the maximum width of the plurality of second structures.

13. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.10≤P / H2≤0.60 Wherein P is an arrangement period of the plurality of second structures in the radial direction, and H2 is a height of each of the plurality of second structures.

14. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.15≤E / n≤0.95 where E is the normalized phase at the boundary between the first region and the second region, and n is the designed diffraction order.

15. The optical element according to claim 1, characterized in that The following inequality is satisfied: 0.00≤H2 / t≤0.10 Wherein H2 is the height of each of the plurality of second structures, and t is the thickness of the substrate.

16. An optical system comprising a plurality of optical elements, the plurality of optical elements including the optical element according to any one of claims 1 to 15.

17. A lens device comprising: The optical system according to claim 16; as well as A holder is configured to hold the optical system.

18. An image pickup device, comprising: The optical system according to claim 16; as well as The image sensor is configured to receive an image formed by the optical system.

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