Optical element, optical system, and image pickup device

Abstract

The document provides optical elements, optical systems, and image acquisition devices. One or more optical elements may include a substrate and a wave structure formed on the substrate, the wave structure including a first antireflective film having one or more layers formed opposite to the substrate and a plurality of wave regions, each wave region including a plurality of structures. A predetermined inequality is satisfied.

Description

Technical Field

[0001] Various aspects of this disclosure relate to one or more embodiments of optical elements, such as superlenses. Background Technology

[0002] As an optical element in an optical system used for imaging, a superlens is known to have a finely textured (uneven or uneven) structure formed on the surface of a substrate and to have light-converging or diverging functions by utilizing diffraction. PCT International Publication No. WO 2022 / 150816 discloses a superlens in which reflection of the optical element is reduced by placing an anti-reflection film above or below the finely textured structure. Summary of the Invention

[0003] One or more embodiments of an optical element according to one or more aspects of this disclosure may include a substrate and a wave structure formed on the substrate, the wave structure including a first antireflective film having one or more layers formed opposite to the substrate and a plurality of wave regions, each wave region including a plurality of structures. The following inequalities may be satisfied:

[0004]

[0005] Where n p It is the refractive index of the first material forming multiple structures for light with a wavelength of 550 nm, κ p It is the extinction coefficient of the first material, and n 1L The refractive index of the second material forming any one of the following layers for light with a wavelength of 550 nm is also mentioned: any one of the layers forming the first antireflective film or any of the multiple layers. An optical system and image acquisition device having the above-described optical elements also constitute another aspect of this disclosure.

[0006] The features of this disclosure will become clear from the following description of embodiments with reference to the accompanying drawings. The following description of embodiments will be given by way of example. Attached Figure Description

[0007] Figure 1A , Figure 1B , Figure 1C and Figure 1D This is a schematic diagram illustrating an optical element based on a representative example.

[0008] Figure 2A and Figure 2B The diagram illustrates an optical element based on a comparative example.

[0009] Figure 3A , Figure 3B and Figure 3C The illustration shows a method for manufacturing an optical element according to this example.

[0010] Figure 4 The diagram illustrates the relationship between the shape of the optical element and the amount of phase modulation according to Example 1.

[0011] Figure 5 The reflectivity characteristics of the optical element according to Example 1 are illustrated.

[0012] Figure 6 The reflectivity characteristics of the optical element according to Example 2 are illustrated.

[0013] Figure 7 The reflectivity characteristics of the optical element according to Example 3 are illustrated.

[0014] Figure 8 The reflectivity characteristics of the optical elements according to Examples 4, 5 and 6 and Comparative Example 2 are illustrated.

[0015] Figure 9 The reflectivity characteristics of the optical element according to Example 7 are illustrated.

[0016] Figure 10 The reflectivity characteristics of the optical element according to Example 8 are illustrated.

[0017] Figure 11 The reflectivity characteristics of the optical element according to Example 9 are illustrated.

[0018] Figure 12 The reflectivity characteristics of the optical elements according to Example 10 and Comparative Example 4 are illustrated.

[0019] Figure 13A , Figure 13B , Figure 13C , Figure 13D and Figure 13E This is a schematic diagram illustrating an optical element based on other examples and comparative examples.

[0020] Figure 14 The reflectivity characteristics of the optical element according to Example 11 are illustrated.

[0021] Figure 15 The reflectivity characteristics of the optical element according to Example 12 are illustrated.

[0022] Figure 16 The reflectivity characteristics of the optical element according to Example 13 are illustrated.

[0023] Figure 17A , Figure 17B , Figure 17C and Figure 17D This is a schematic diagram illustrating an optical element based on other examples and comparative examples.

[0024] Figure 18A , Figure 18B , Figure 18C , Figure 18D , Figure 18E and Figure 18F The diagram illustrates the manufacturing process. Figure 17A , Figure 17B , Figure 17C and Figure 17D The method of the optical element shown.

[0025] Figure 19 The reflectivity characteristics of the optical element according to Example 14 are illustrated.

[0026] Figure 20 The reflectivity characteristics of the optical element according to Example 15 are illustrated.

[0027] Figure 21 The reflectivity characteristics of an optical element according to Example 16 are illustrated.

[0028] Figure 22 The reflectivity characteristics of the optical elements according to Examples 17 and 18 and Comparative Example 7 are illustrated.

[0029] Figure 23 An optical system using optical elements according to Examples 1 to 18 is illustrated.

[0030] Figure 24 The illustration shows an image pickup device using the optical system described above.

[0031] Figure 25 The reflectivity characteristics of the optical element according to Comparative Example 1 are illustrated.

[0032] Figure 26 The reflectivity characteristics of the optical element according to Comparative Example 3 are illustrated.

[0033] Figure 27 The reflectivity characteristics of the optical element according to Comparative Example 5 are illustrated.

[0034] Figure 28 The reflectivity characteristics of the optical element according to Comparative Example 6 are illustrated. Detailed Implementation

[0035] Examples according to this disclosure will now be described with reference to the accompanying drawings.

[0036] Figure 1A , Figure 1B , Figure 1C and Figure 1D The illustration shows an optical element of a representative example of this disclosure. Figure 1A , Figure 1B and Figure 1C The cross-sections of optical elements 101, 102, and 103 in the radial direction are illustrated respectively. Figure 1DThe diagram illustrates optical element 101 as viewed from above. Optical elements 102 and 103, viewed from above, are similar to optical element 101 as viewed from above.

[0037] Optical elements 101, 102, and 103 include a substrate 50 and wave (uneven unevenness) structures 41, 42, and 43 respectively formed on the substrate 50 (on a first surface of the substrate 50). Each wave structure includes annular bands i, i+1, ... arranged as a plurality of wave regions. Each annular band is oriented along the first surface... Figure 1A , Figure 1B , Figure 1C and Figure 1D The substrate 50 includes multiple structures in the radial direction. Multiple convex elements (convex portions) 10, as multiple structures in each annular band, are deployed at a predetermined pitch; in other words, they are periodically deployed in the radial direction of the substrate 50. Multiple concave elements (concave portions) are formed between the multiple convex elements 10. In the radial direction of the substrate 50, the widths of the multiple convex elements 10 and the multiple concave elements are different from each other in each annular band (gradually decreasing or increasing). In this way, by periodically forming multiple annular bands i, i+1, ... in the radial direction of the substrate 50, each annular band serves as a phase difference applying structure, and each of the optical elements 101 to 103 serves as a superlens with incident light converging or diverging functions.

[0038] In the wave structures 41 to 43, a first anti-reflective film 11 is provided opposite to the substrate 50. More specifically, it is provided in the direction along the first surface at a portion above each convex element 10 within the width of each convex element 10 (between the convex element 10 and the air).

[0039] In addition to the first antireflective film 11, the wave structure 42 of optical element 102 also includes a second antireflective film 12 disposed to cover the substrate 50 (first surface). In addition to the first antireflective film 11 and the second antireflective film 12, the wave structure 43 of optical element 103 also includes a third antireflective film 13 disposed below each convex element 10 between the second antireflective film 12 and the convex element 10 (i.e., within the width of the convex element 10 in the direction along the first surface). Each of the first to third antireflective films 11 to 13 is a single-layer film or a multilayer film comprising one or more layers (low refractive index layer or high refractive index layer). In the following description, the first to third antireflective films 11 to 13 will be simply referred to as antireflective films 11 to 13.

[0040] In optical elements 101 to 103, substrate 50 is a light-transmitting flat plate. However, substrate 50 can be a plane mirror that reflects incident light, or it can be a curved plate. The material of substrate 50 can be synthetic quartz, inorganic glass, organic materials (such as plastics), ceramics, metals, etc.

[0041] Wave structures 41 to 43 provide a converging or diverging effect by applying a phase difference to light passing through them. More specifically, each of the multiple annular bands i, i+1, ... (including multiple structures (convex and concave elements) with different widths) provides 2m of light for the designed wavelength. The phase distribution (diffraction order m=1, 2,…) exhibits a light-converging effect equivalent to that of a diffractive optical element (DOE).

[0042] Each convex element 10 in the wave structures 41 to 43 has a cylindrical shape. The shape of each convex element 10 is not limited to a cylindrical shape, but can be a prismatic shape.

[0043] The convex element 10 is positioned at the center of a square-shaped unit partition (segment) 60, which is divided in the radial and circumferential directions of the substrate 50. The width (pitch) P of each segment 60 (i.e., the pitch of each convex element 10) is smaller than the wavelength of the incident light. Thus, regardless of the shape of the convex element 10, the incident light undergoes phase modulation according to the effective refractive index determined by the element fill factor occupied by the convex element 10 in the segment 60. For example, when the incident light is in the visible range (400 to 680 nm), the pitch P can be equal to or less than 400 nm, and the pitch P can be further reduced to suppress unwanted diffraction. More specifically, the following inequality can be satisfied:

[0044]

[0045] In each annular band, a plurality of protruding elements 10 are formed to sandwich a concave element in the middle. In each annular band, by varying the width of the protruding elements 10 in the radial direction of the substrate 50, a 2m band is formed. The phase distribution.

[0046] In optical elements 101 to 103, the convex element 10 has a constant height H0 [nm] in all regions. In optical element 101, the wave structure 41 including the antireflective film 11 has a constant height H1 [nm] in all regions. In optical element 102, the wave structure 42 including antireflective films 11 and 12 has a constant height H2 [nm] in all regions. In optical element 103, the wave structure 43 including antireflective films 11 to 13 has a constant height H3 [nm] in all regions.

[0047] In optical elements 101 to 103, where the height of the wave structure is constant in all regions, the width W [nm] (diameter of the cylinder) of the convex element 10, which is a component of each wave structure, is varied to form 2m in each annulus. The phase distribution is thus altered. Consequently, the element fill factor of the convex elements 10 (and antireflective films 11 to 13) in each segment 60 changes. In other words, the element fill factor in segment 60 decreases as the width of the convex element 10 decreases, and the desired phase distribution is formed accordingly. In segments 60 where the minimum width of the convex element 10 decreases, the aspect ratio (the ratio of the height to the width of the convex element 10) increases. The convex element 10, having a large aspect ratio and being relatively elongated, may deform, tilt, or peel off when subjected to loads due to contact, vibration, etc., or when external factors such as temperature or pressure change. Therefore, the minimum value of the width W [nm] of each convex element 10 can be equal to or greater than 25 nm.

[0048] exist Figure 1D The diagram shows a segment 60 deployed in one dimension in the radial direction of the substrate 50. However, in reality, the segment 60 is deployed in two dimensions in both the radial and circumferential directions of the substrate 50, and has the function of converging or diverging incident light in the two-dimensional direction.

[0049] Reference Figure 2A and 2B The reflection of incident light in optical element 100 according to a comparative example is described. Figure 2A The diagram illustrates a cross-section of the optical element 100 in the radial direction. The optical element 100 does not have antireflective coatings 11 to 13. That is, the optical element 100 includes a substrate 50 and a wave structure 40, and the wave structure 40 includes only convex elements 10 with a height H0 [nm]. In the optical element 100, the element fill factor of the convex elements 10 in segment 60 also varies to form 2m in each annular band. The phase distribution. When the width (pitch) P of each segment 60 is less than the wavelength of the incident light, regardless of the shape of the convex element 10, the light will recognize the convex element 10 as a film element 14 with an effective refractive index determined by the element fill factor of the segment 60, such as... Figure 2B As shown in the diagram. That is, where Figure 2A The undulating structure 40, where the width (diameter) of the convex element 10 shown varies from a larger value to a smaller value, is equivalent to... Figure 2B The membrane 48 shown is composed of multiple membrane elements 14 with refractive indices varying from larger to smaller values ​​(gray level decreases in the figure).

[0050] When light is incident on the film 48, reflection occurs at the interface 70 between the air and the film 48 and at the interface 80 between the substrate 50 and the film 48. At this time, because the refractive index of the film 48 changes in the radial direction of the substrate 50, the reflectivity characteristics change depending on the in-plane position. That is, an anti-reflective film needs to be formed to reduce the reflection occurring at interfaces 70 and 80, and its reflectivity changes for each segment 60. In this example, optical elements 101 to 103 include one or more anti-reflective films to reduce the reflection occurring at the aforementioned interfaces.

[0051] exist Figure 2A In order to reduce reflection at the interface 70 between each convex element 10 and the air, an anti-reflective film 11 is formed above each convex element 10, such as... Figure 1A As shown in the image. p It is the refractive index of the first material forming the convex element 10 of the structure for light with a wavelength of 550 nm, and κ p It is the extinction coefficient of the first material. Furthermore, n 1L This is the refractive index of the second material for light with a wavelength of 550 nm, which forms any one or more layers constituting the antireflective film 11, for example, the layer with the lowest refractive index or the layer furthest from the substrate 50 (closest to the air side). In this case, the following inequality can be satisfied:

[0052]

[0053] Anti-reflective coating 11 can reduce, for example Figure 2A The reflection occurs at the interface 70 between each convex element 10 and the air shown. In this case, at n p and n 1L Without satisfying inequalities (1) and (3), it is difficult to obtain sufficient anti-reflective properties. In κ p When the value is greater than 0.001, light absorption increases, making it difficult to use the optical element across a wide wavelength range from the visible to the near-infrared.

[0054] The lower limit of inequality (1) can be 1.5 or 2.0, and the upper limit of inequality (1) can be 3.5.

[0055] The lower limit of inequality (3) can be 0.8. Or 0.9 Furthermore, the upper limit of inequality (3) can be 1.1. .

[0056] In such Figure 1AIn the optical element 101 shown, reflection also occurs at the interface 80 between each convex element 10 and the substrate 50. To reduce this reflection, an anti-reflection film 12 is formed at the interface 80 between each convex element 10 and the substrate 50 to cover the substrate 50, such as... Figure 1B As shown in the figure, the following inequalities can be satisfied:

[0057]

[0058] Where n 2L It is the refractive index of the third material for light with a wavelength of 550 nm, which forms any one or more layers of the antireflective film 12, for example, the layer closest to the convex element (structure).

[0059] The lower limit of inequality (4) can be 1.4, and the upper limit of inequality (4) can be 1.6.

[0060] As described above, reflection at interface 80 occurs due to the difference in refractive index between each film element 14 and the substrate 50. When the area surrounding the convex element 10 is air, the effective refractive index of the film element 14 is determined by the filling factor of the convex element 10 and the air. Specifically, when the width W of the convex element 10 is small, the refractive index is closer to the refractive index of air. In this case, the following inequality can be satisfied:

[0061]

[0062] Where d 2L It is the thickness (physical thickness) of the third material layer.

[0063] When the antireflective film 12 is constructed by repeatedly stacking a third material and a fourth material, the following inequality can be satisfied:

[0064]

[0065] Where n 2H It is the refractive index of the fourth material for light with a wavelength of 550nm.

[0066] The upper limit of inequality (6) can be 2.8 or 2.6.

[0067] Figure 1B The antireflective films 11 and 12 shown can reduce reflection at the interface 70 between each convex element 10 and the air, and at the interface 80 between each convex element 10 and the substrate 50. To further reduce reflection, an antireflective film 13 can be formed at the interface between each convex element 10 and the antireflective film 12, such as... Figure 1C As shown in the image.

[0068] The antireflective film 13 has the same width as the convex element 10 and is formed only at the locations where the convex element 10 is formed. The following inequality can be satisfied:

[0069]

[0070] Where n 3L It is the refractive index of the fifth material for light with a wavelength of 550 nm, which forms any one or more layers of the antireflective film 13, for example, the layer closest to the convex element.

[0071] The lower limit of inequality (7) can be 1.4, and the upper limit of inequality (7) can be 1.6.

[0072] When the antireflective film 13 is constructed by repeatedly stacking the fifth and sixth materials, the following inequality can be satisfied:

[0073]

[0074] Where n 3H It is the refractive index of the sixth material for light with a wavelength of 550nm.

[0075] The upper limit of inequality (8) can be 2.8 or 2.6.

[0076] The following inequalities can be satisfied:

[0077]

[0078] Where n s It is the refractive index of the material forming the substrate 50 for light with a wavelength of 550 nm.

[0079] The upper limit of inequality (9) can be 2.3 or 2.1.

[0080] The first material forming the convex element 10 can be a dielectric material, including silicon nitride (Si3N4), titanium oxide (TiO2), gallium nitride (GaN), gallium arsenide (GaAs), silicon carbide (SiC), aluminum oxide (Al2O3), silicon oxide (SiO2), etc.

[0081] The second material, which is one of the materials forming the antireflective film 11, can be an organic resin made of silicon oxide, magnesium fluoride (MgF2), aluminum oxide, fluorine (F), silicon (Si), etc.

[0082] The third material, which is one of the materials used to form the antireflective film 12, can be silicon oxide, magnesium fluoride, magnesium oxide (MgO), etc. The fourth material, which is another material used to form the antireflective film 12, can be silicon nitride, titanium oxide, gallium nitride, gallium arsenide, or silicon carbide, and can be the same as the first material of the convex element 10.

[0083] The fifth material, as one of the materials forming the antireflective film 13, can be silicon oxide, magnesium fluoride, or magnesium oxide. The sixth material, as another material forming the antireflective film 13, can be silicon nitride, titanium oxide, gallium nitride, gallium arsenide, or silicon carbide, and can be the same as the first material of the convex element 10. The second, third, and fifth materials can be the same material.

[0084] Optical elements 101 to 103 can be manufactured using photolithography. As an example, Figure 3A , Figure 3B and Figure 3C The illustration shows the process of fabricating optical element 103 by nanoimprint lithography.

[0085] Figure 3A The illustration shows a mold 91 formed by an electron beam, laser, etc., and having a shape opposite to the wave shape of the wave structure 43. For example... Figure 3B As shown, a resist material 92 is applied onto a film 93 deposited on a substrate 50, a mold 91 is pressed onto the resist material 92, and irradiation with ultraviolet light or the like is performed to form a shape in the resist material 92 that is opposite to the uneven shape of the mold 91.

[0086] Next, etching is performed using resist material 92 as a mask to form the wave structure 43 of the optical element 103. The etching proceeds to the antireflective film 11, the convex element 10, and the antireflective film 13, and terminates when it reaches the antireflective film 12. Therefore, it can be said that anisotropic etching is appropriate for the generation of the wave structure 42.

[0087] After etching is completed, the resist material 92 is removed to form the wave structure 43 of the optical element 103, such as... Figure 3C As shown in the image.

[0088] The method for manufacturing wave structure 43 is not limited to the above-mentioned nanoimprint lithography, and other methods can be used, such as directly forming wave structure with electron beam, laser, etc.

[0089] Specific examples 1 through 20 are described below. The configurations in these examples are merely illustrative, and other configurations may be used.

[0090] Examples 1 to 3

[0091] The optical element according to Example 1 includes, for example, Figure 1A The anti-reflective film 11 in the optical element 101 shown. The optical element according to Example 2 includes, for example... Figure 1B The anti-reflective films 11 and 12 in the optical element 102 shown. The optical element according to Example 3 includes, for example... Figure 1CThe anti-reflective coatings 11, 12, and 13 in the optical element 103 shown. The optical elements according to Examples 1 to 3 are DOEs used in the visible range (wavelength 420 to 680 nm).

[0092] In Examples 1 to 3, the substrate 50 is formed of quartz with a refractive index of 1.46 (for light with a wavelength of 550 nm), and each convex element 10 is formed of silicon nitride with a refractive index of 2.09 (for light with a wavelength of 550 nm) in a cylindrical shape. The convex elements 10 are deployed in corresponding square segments 60, each segment 60 having a pitch P of 240 nm, and the height H0 of the convex element 10 is 700 nm. Each wave structure has... It has an effective diameter of 4.0 mm and is constructed by periodically deploying 105 rings, each ring providing 2 [units of energy] for light with a wavelength of 500 nm. The phase difference (diffraction order = 1). The focal length generated by each wave structure is 40.0 mm.

[0093] Table 1 summarizes the materials and refractive indices of the antireflective films 11 to 13, the convex element 10, and the substrate 50 in the optical elements according to Examples 1 to 3, as well as the film thickness (height) of the antireflective films 11 to 13 and the convex element 10. The refractive indices of the materials are values ​​for light with a wavelength of 550 nm.

[0094] exist Figure 4 In the diagram, the horizontal axis represents the normalized diameter obtained by normalizing the diameter W (which is the width of the convex element 10 in the optical element of Example 1) with the segment pitch P, and the vertical axis represents the normalized diameter obtained by normalizing the incident light phase modulation amount with 2 The normalized phase is obtained by normalization (diffraction order m=1). In the optical element according to Example 1, the phase modulation amount includes the modulation amount at the antireflective coating 11 formed on each convex element 10. Figure 4 In this process, the normalized diameter varies from 0.13 to 0.87 to make the normalized phase difference vary from 0 to 1.

[0095] Figure 5 The illustration shows the reflectivity characteristics of the convex element 10 in the optical element according to Example 1 when the normalized diameter is 0.13, 0.30, 0.40, 0.50, 0.60, 0.70, and 0.87. The reflectivity characteristics in the visible range are all 3.5% or less. Figure 6 and Figure 7 The reflectivity characteristics of the optical elements according to Examples 2 and 3 are illustrated as the normalized diameter varies similarly from 0.13 to 0.87. The reflectivity characteristics of the optical elements according to Examples 2 and 3 in the visible range are 3.0% or less. Based on these results, it can be understood that the reflectivity characteristics (anti-reflection performance) of the optical elements according to Examples 1 to 3 are excellent.

[0096] Following the order of Examples 1, 2, and 3, the anti-reflective performance is improved. Based on this result, it can be confirmed that by increasing the number of anti-reflective films in the order of anti-reflective films 11, 12, and 13, the anti-reflective performance is improved.

[0097] Table 1

[0098]

[0099] Examples 4 to 6

[0100] The optical element according to Example 4 includes an anti-reflective coating 11 as in optical element 101. The optical element according to Example 5 includes anti-reflective coatings 11 and 12 as in optical element 102. The optical element according to Example 6 includes anti-reflective coatings 11, 12, and 13 as in optical element 103. The optical elements according to Examples 4 to 6 are DOEs used in the infrared range (wavelength 800 nm).

[0101] In Examples 4 to 6, the substrate 50 is formed of quartz with a refractive index of 1.46 (for light with a wavelength of 550 nm), and each convex element 10 is formed of silicon nitride with a refractive index of 2.09 (for light with a wavelength of 550 nm) in a cylindrical shape. The convex elements 10 are deployed in corresponding square segments 60, each segment having a pitch P of 360 nm, and the height H0 of the convex element 10 is 1200 nm. Each wave structure has... It has an effective diameter of 4.0 mm and is constructed by periodically deploying 105 rings, each ring providing 2 [units of energy] for light with a wavelength of 800 nm. The phase difference (diffraction order = 1). The focal length produced by each wave structure is 40.0 mm. In Examples 4 to 6, the normalized diameter of the convex element 10 varies from 0.20 to 0.80 to vary the normalized phase difference from 0 to 1.

[0102] Table 2 summarizes the materials and refractive indices of the antireflective films 11 to 13, the convex element 10, and the substrate 50 in the optical elements according to Examples 4 to 6, as well as the film thickness (height) of the antireflective films 11 to 13 and the convex element 10. The refractive indices of the materials are values ​​for light with a wavelength of 550 nm.

[0103] Figure 8The illustration shows the reflectivity characteristics of the convex element 10 in the optical elements according to Examples 4 to 6 as the normalized diameter varies from 0.20 to 0.80 for light with a wavelength of 800 nm. Within the range of normalized diameter from 0.20 to 0.80, the reflectivity characteristic of the optical element according to Example 4 is 3.0% or less, and the reflectivity characteristic of the optical elements according to Examples 5 and 6 is 1.0% or less. Based on these results, it can be understood that the reflectivity characteristics (anti-reflection performance) of the optical elements according to Examples 4 to 6 are excellent.

[0104] Table 2

[0105]

[0106] Examples 7 to 9

[0107] The optical element according to Example 7 includes an anti-reflective coating 11 as in optical element 101. The optical element according to Example 8 includes anti-reflective coatings 11 and 12 as in optical element 102. The optical element according to Example 9 includes anti-reflective coatings 11, 12, and 13 as in optical element 103. The optical elements according to Examples 7 to 9 are DOEs used in the visible range (wavelength 420 to 680 nm).

[0108] In Examples 7 to 9, the substrate 50 is formed of S-LAH79 (manufactured by OHARA) with a refractive index of 2.00 (for light with a wavelength of 550 nm), and each convex element 10 is formed in a cylindrical shape of titanium oxide with a refractive index of 2.47 (for light with a wavelength of 550 nm). The convex elements 10 are deployed in corresponding square segments 60, each segment having a pitch P of 240 nm, and the height H0 of the convex element 10 is 550 nm. Each wave structure has... It has an effective diameter of 4.0 mm and is constructed by periodically deploying 105 rings, each ring providing 2 [units of energy] for light with a wavelength of 500 nm. The phase difference (diffraction order = 1). The focal length produced by each wave structure is 40.0 mm. In Examples 7 to 9, the normalized diameter of the convex element 10 varies from 0.20 to 0.80 to vary the normalized phase difference from 0 to 1.

[0109] Table 3 summarizes the materials and refractive indices of the antireflective films 11 to 13, the convex element 10, and the substrate 50 in the optical elements according to Examples 7 to 9, as well as the film thickness (height) of the antireflective films 11 to 13 and the convex element 10. The refractive indices of the materials are values ​​for light with a wavelength of 550 nm.

[0110] Figure 9 , Figure 10 and Figure 11The illustration shows the reflectivity characteristics in the visible range when the normalized diameter of the convex element 10 according to Examples 7, 8, and 9 varies to 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, and 0.80, respectively. Within the range of normalized diameters from 0.20 to 0.80, the reflectivity characteristic of the optical element according to Example 7 is 11.0% or less, the reflectivity characteristic of the optical element according to Example 8 is 6.0% or less, and the reflectivity characteristic of the optical element according to Example 9 is 2.0% or less. Based on this result, it can be understood that the reflectivity characteristics (anti-reflection performance) of the optical elements according to Examples 4 to 6 are excellent.

[0111] Table 3

[0112]

[0113] Example 10

[0114] The optical element according to Example 10 includes an anti-reflective coating 11 as in optical element 101. The optical element according to Example 10 is a DOE used in the infrared range (wavelength 800 nm).

[0115] In Example 10, the substrate 50 is formed of quartz with a refractive index of 1.46 (for light with a wavelength of 550 nm), and each convex element 10 is formed of gallium arsenide (GaAs) with a refractive index of 3.45 (for light with a wavelength of 550 nm) in a cylindrical shape. The convex elements 10 are deployed in corresponding square segments 60, each segment having a pitch P of 360 nm, and the height H0 of the convex element is 600 nm. The wave structure has... It has an effective diameter of 4.0 mm and is constructed by periodically deploying 105 rings, each ring providing 2 [units of energy] for light with a wavelength of 800 nm. The phase difference (diffraction order = 1). The focal length generated by the wave structure is 40.0 mm. In Example 10, the normalized diameter of the convex element 10 is varied from 0.20 to 0.80 to vary the normalized phase difference from 0 to 1.

[0116] Table 4 summarizes the materials and refractive indices of the antireflective film 11, the convex element 10, and the substrate 50 in the optical element according to Example 10, as well as the film thickness (height) of the antireflective film 11 and the convex element 10. The refractive indices of the materials are values ​​for light with a wavelength of 550 nm.

[0117] Figure 12The figure illustrates the reflectivity characteristics of the convex element in the optical element according to Example 10 for light with a wavelength of 800 nm as the diameter varies from 0.20 to 0.80. Within the normalized diameter range of 0.2 to 0.8, the reflectivity characteristic of the optical element according to Example 10 is 5.0% or less. Based on this result, it can be understood that the reflectivity characteristics (anti-reflection performance) of the optical element according to Example 10 are excellent.

[0118] Table 4

[0119]

[0120] Examples 11 to 13

[0121] Figure 13A , Figure 13B and Figure 13C The cross-sections of the i-th ring in optical elements 104, 105, and 106 are illustrated respectively. Figure 13D The diagram illustrates optical element 104 as viewed from above. Optical elements 105 and 106, when viewed from above, are similar to optical element 104.

[0122] Optical elements 104, 105, and 106 include a substrate 50 and wave structures 44, 45, and 46 respectively formed on the substrate 50. Each of the wave structures 44 to 46 includes a convex element 15, a concave element 16 as structures, and an anti-reflective film 11 disposed above each convex element 15. Figure 13D As shown, the wave structure 44 is constructed by deploying a plurality of rectangular tubular concave elements 16, thereby forming convex elements 15 therebetween. This is the same for optical elements 105 and 106.

[0123] In addition to the anti-reflective film 11, the optical element 105 also includes an anti-reflective film 12 disposed between each convex element 15 and the substrate 50 to cover the substrate 50.

[0124] In addition to the anti-reflective films 11 and 12, the optical element 106 also includes an anti-reflective film 13 (located below the convex element 15) disposed between each convex element 15 and the anti-reflective film 12.

[0125] In all regions, the heights of the wave structures 44, 45, and 46 are constant. This is to form a 2m [structure / structure] in each annulus. The phase distribution is changed by altering the width W of the concave element 16 in each wave structure to change the element fill factor of the convex element 15 (and anti-reflective films 11 to 13) in segment 60.

[0126] Optical elements 104 to 106 can be manufactured using a manufacturing method similar to that used for optical elements 101 to 103.

[0127] The optical element according to Example 11 includes an anti-reflective coating 11 as in optical element 104. The optical element according to Example 12 includes anti-reflective coatings 11 and 12 as in optical element 105. The optical element according to Example 13 includes anti-reflective coatings 11, 12, and 13 as in optical element 106. The optical elements according to Examples 11 to 13 are DOEs used in the visible range (wavelength 420 to 680 nm).

[0128] In Examples 11 to 13, the substrate 50 is formed of S-BAH28 (manufactured by OHARA) with a refractive index of 1.72 (for light with a wavelength of 550 nm), and each convex element 15 is formed in a cylindrical shape of silicon nitride with a refractive index of 2.09 (for light with a wavelength of 550 nm). The convex elements 15 are deployed in corresponding square segments 60, the segment pitch P of which is 240 nm, and the height H0 of the convex element 15 is 700 nm. Each wave structure has... It has an effective diameter of 4.0 mm and is constructed by periodically deploying 105 rings, each ring providing 2 [units of energy] for light with a wavelength of 500 nm. The phase difference (diffraction order = 1). The focal length produced by each wave structure is 40.0 mm. In Examples 11 to 13, the normalized diameter of the convex element 15 varies from 0.20 to 0.80 to vary the normalized phase difference from 0 to 1.

[0129] Table 5 summarizes the materials and refractive indices of the antireflective films 11 to 13, the convex element 15, and the substrate 50 in the optical elements according to Examples 11 to 13, as well as the film thickness (height) of the antireflective films 11 to 13 and the convex element 15. The refractive indices of the materials are values ​​for light with a wavelength of 550 nm.

[0130] Figure 14 , Figure 15 and Figure 16 The illustration shows the reflectivity characteristics in the visible range when the normalized diameter of the convex element 15 in the optical elements according to Examples 11, 12, and 13 varies to 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, and 0.80, respectively. Within the range of normalized diameters from 0.2 to 0.8, the reflectivity characteristic of the optical element according to Example 11 is 7.0% or less, the reflectivity characteristic of the optical element according to Example 12 is 3.0% or less, and the reflectivity characteristic of the optical element according to Example 13 is 2.0% or less. Based on this result, it can be understood that the reflectivity characteristics (anti-reflection performance) of the optical elements according to Examples 11 to 13 are excellent.

[0131] Table 5

[0132]

[0133] Examples 14 to 16

[0134] Figure 17A , Figure 17B and Figure 17C The cross-sections of the i-th ring in optical elements 201, 202 and 203 are shown respectively.

[0135] exist Figure 1A , Figure 1B and Figure 1C In the optical elements 101 to 103 shown, the space around (above and between) the plurality of convex elements 10 is filled with air. However, in optical elements 201 to 203, the space between the plurality of convex elements 10 is filled with material 90, serving as a medium other than air. Accordingly, in optical elements 201 to 203, an anti-reflective film 11 of uniform thickness is provided not only on the convex elements 10 but also on the material 90. Anti-reflective films 12 and 13 are similar to those in optical elements 102 and 103.

[0136] Similar to optical elements 101 to 103, optical elements 201 to 203 can be manufactured using photolithography. Figure 18A , Figure 18B , Figure 18C , Figure 18D , Figure 18E and Figure 18F The illustration shows a method for manufacturing optical element 203 as an example.

[0137] Figure 18A The illustration shows a mold 91 formed by an electron beam, laser, etc., and having a shape opposite to the uneven shape of the wave structure 43. For example... Figure 18B As shown, a resist material 92 is applied onto a film 93 deposited on a substrate 50, a mold 91 is pressed onto the resist material 92, and irradiation with ultraviolet light or the like is performed to form a shape in the resist material 92 that is opposite to the uneven shape of the mold 91.

[0138] After that, as Figure 18D As shown, material 90 is formed around the convex element 10 by atomic layer deposition (ALD). Then, as... Figure 18E As shown, material 90 on the protruding element 10 is removed by etching. Furthermore, as... Figure 18F As shown, an anti-reflective film 11 is deposited over the convex element 10 and the material 90 by vapor deposition.

[0139] The method for forming the antireflective film 11 is not limited to vapor deposition, but can be a dry deposition method (such as sputtering) or a wet deposition method (such as sol-gel method).

[0140] The optical element according to Example 14 includes an anti-reflective coating 11 as in optical element 201. The optical element according to Example 15 includes anti-reflective coatings 11 and 12 as in optical element 202. The optical element according to Example 16 includes anti-reflective coatings 11, 12, and 13 as in optical element 203. The optical elements according to Examples 14 to 16 are DOEs used in the visible range (wavelength 420 to 680 nm).

[0141] In Examples 14 to 16, the substrate 50 is formed of quartz with a refractive index of 1.46 (for light with a wavelength of 550 nm), and each convex element 10 is formed of silicon nitride with a refractive index of 2.09 (for light with a wavelength of 550 nm) in a cylindrical shape. The material 90 is silicon oxide (SiO2) with a refractive index of 1.46 (for light with a wavelength of 550 nm). The convex elements 10 are deployed in corresponding square segments 60, the segment pitch P of which is 240 nm, and the height H0 of the convex element is 1250 nm. Each wave structure has... It has an effective diameter of 4.0 mm and is constructed by periodically arranging 105 rings, each ring providing 2 [units of energy] for light with a wavelength of 500 nm. The phase difference (diffraction order = 1). The focal length produced by each wave structure is 40.0 mm. In Examples 14 to 16, the normalized diameter of the convex element 10 is varied from 0.20 to 0.80 to vary the normalized phase difference from 0 to 1.

[0142] Table 6 summarizes the materials and refractive indices of material 90, antireflective films 11 to 13, convex element 10, and substrate 50 in the optical elements according to Examples 14 to 16, as well as the film thicknesses (heights) of antireflective films 11 to 13 and convex element 10. The refractive indices of the materials are values ​​for light with a wavelength of 550 nm.

[0143] Figure 19 , Figure 20 and Figure 21 The illustration shows the reflectivity characteristics in the visible range when the normalized diameter of the convex element 10 in the optical elements according to Examples 14, 15, and 16 varies to 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, and 0.80, respectively. Within the range of normalized diameters from 0.20 to 0.80, the reflectivity characteristic of the optical element according to Example 14 is 4% or less, and the reflectivity characteristic of the optical elements according to Examples 15 and 16 is 2.0% or less. Based on this result, it can be understood that the reflectivity characteristics (anti-reflection performance) of the optical elements according to Examples 14 to 16 are excellent.

[0144] Table 6

[0145]

[0146] Examples 17 and 18

[0147] The optical element according to Example 17 includes an anti-reflective coating 11 as in optical element 201. The optical element according to Example 18 includes anti-reflective coatings 11 and 12 as in optical element 202. The optical elements according to Examples 17 and 18 are DOEs used in the infrared range (wavelength 800 nm).

[0148] In Examples 17 and 18, the substrate 50 is formed of quartz with a refractive index of 1.46 (for light with a wavelength of 550 nm), and each convex element 10 is formed of gallium arsenide with a refractive index of 3.45 (for light with a wavelength of 550 nm) in a cylindrical shape. The convex elements 10 are deployed in corresponding square segments 60, the segment pitch P of which is 360 nm, and the height H0 of the convex element is 1070 nm. Each wave structure has... It has an effective diameter of 4.0 mm and is constructed by periodically deploying 105 rings, each ring providing 2 [units of energy] for light with a wavelength of 800 nm. The phase difference (diffraction order = 1). The focal length produced by each wave structure is 40.0 mm. In Examples 17 and 18, the normalized diameter of the convex element 10 is varied from 0.20 to 0.80 to vary the normalized phase difference from 0 to 1.

[0149] Table 7 summarizes the materials and refractive indices of material 90, antireflective films 11 to 13, convex element 10, and substrate 50 in the optical elements according to Examples 17 and 18, as well as the film thicknesses (heights) of antireflective films 11 to 13 and convex element 10. The refractive indices of the materials are values ​​for light with a wavelength of 550 nm.

[0150] Figure 22 The illustration shows the reflectivity characteristics of light with a wavelength of 800 nm when the diameter of the convex element 10 in the optical elements according to Examples 17 and 18 varies from 0.20 to 0.80. Within the normalized diameter range of 0.20 to 0.80, the reflectivity characteristic of the optical element according to Example 17 is 6.0% or less, and the reflectivity characteristic of the optical element according to Example 18 is 2.0% or less. Based on these results, it can be understood that the reflectivity characteristics (anti-reflection performance) of the optical elements according to Examples 17 and 18 are excellent.

[0151] Table 7

[0152]

[0153] Optical system

[0154] Figure 23 An optical system 401 using any of the optical elements according to Examples 1 to 18 is illustrated. Figure 23In the figures, reference numeral 301 denotes the optical element in each example, reference numeral 302 denotes the lens element, and OA denotes the optical axis of the optical system. Furthermore, IP denotes the image plane.

[0155] Lens element 302 comprises a refractive lens, a DOE, a reflector, etc., and one or more such elements are deployed. Optical element 301 and lens element 302 are deployed along the optical axis OA, and the incident light is imaged onto the image plane IP. In the image acquisition device, the image plane of the image sensor (such as a CCD sensor or a CMOS sensor) or the surface of the silver halide film is deployed at the image plane IP.

[0156] This optical system 400 is not limited to image acquisition devices, but is also applicable to a variety of optical devices, such as binoculars, projectors and telescopes.

[0157] Image pickup device

[0158] Figure 24 The diagram includes Figure 23 The optical system 401 contains the image pickup device (digital camera) 501. Figure 24 In the accompanying drawings, reference numeral 4 denotes the camera body, and reference numeral 3 denotes the imaging optical system comprising the optical system 401. Reference numeral 5 denotes an image sensor disposed in the camera body 4 and configured to receive and photoelectrically convert the optical image formed by the imaging optical system 3 (i.e., capture the image of an object formed by the optical system). The camera body 4 may be an SLR camera including a fast-rotating mirror, or it may be a mirrorless camera without a fast-rotating mirror.

[0159] Therefore, by applying an optical system including optical elements according to each example to an image-capturing device such as a digital camera, an image-capturing device that can properly capture images can be obtained.

[0160] Comparative Examples 1 to 7

[0161] The optical element according to Comparative Example 1 is a comparative example relative to the optical elements according to Examples 1 to 3, and does not include an anti-reflective coating. Figure 2A The optical element 100 shown is similar.

[0162] Except for the absence of the anti-reflective coating 11, the optical element according to Comparative Example 1 is constructed identically to the optical elements according to Examples 1 to 3. The substrate 50 is formed of quartz with a refractive index of 1.46 (for light with a wavelength of 550 nm), and each convex element 10 is formed of silicon nitride with a refractive index of 2.09 (for light with a wavelength of 550 nm) in a cylindrical shape. The pitch P of the segment 60 is 240 nm, and the height H0 of the convex element is 700 nm. The wave structure has... The effective diameter is 4.0 mm and includes 105 rings, similar to the optical elements according to Examples 1 to 3. The normalized diameter of the convex element 10 is 0.13 to 0.87, as in Examples 1 to 3. The optical elements according to Examples 1 to 3 have a construction in which antireflective films 11 to 13 are provided on the optical element according to Comparative Example 1.

[0163] The optical element according to Comparative Example 2 is a comparative example relative to the optical elements according to Examples 4 to 6, and the optical element according to Comparative Example 3 is a comparative example relative to Examples 7 to 9. The optical element according to Comparative Example 4 is a comparative example relative to the optical element according to Example 10. Figure 2A The optical element 100 shown is similar, and Comparative Examples 2 to 4 do not include anti-reflective coatings.

[0164] The optical element according to Comparative Example 5 is a comparative example relative to the optical elements according to Examples 11 to 13, and does not include an anti-reflective coating. Figure 13E The optical element 107 shown is similar. The optical element according to Comparative Example 6 is a comparative example relative to the optical elements according to Examples 14 to 16, and the optical element according to Comparative Example 7 is a comparative example relative to the optical elements according to Examples 17 and 18. Comparative Examples 6 and 7 do not include an anti-reflective film in the wave structure 40, and are similar to... Figure 17D The optical element 200 shown is similar.

[0165] Table 8 summarizes the materials and refractive indices of the substrate 50 and the convex element 10 in Comparative Examples 1 to 7, the height of the convex element 10, and the material 90 and its refractive index.

[0166] Figure 25 The figure illustrates the reflectivity characteristics of the optical element according to Comparative Example 1. Figure 26 The figure illustrates the reflectivity characteristics of the optical element according to Comparative Example 3. Figure 27 The reflectivity characteristics of the optical element according to Comparative Example 5 are illustrated, and Figure 28 The figure illustrates the reflectivity characteristics of the optical element according to Comparative Example 6. The reflectivity characteristics of the optical element according to Comparative Example 2 are shown in... Figure 8 As shown in the figure, the reflectivity characteristics of the optical element according to Comparative Example 4 are... Figure 12 As shown in the figure, and based on the reflectivity characteristics of the optical element in Comparative Example 5, Figure 22 As shown in the image.

[0167] From the reflectivity characteristics of the examples and comparative examples, it can be understood that the optical elements according to Examples 1 to 18 have higher anti-reflection performance than the optical elements according to Comparative Examples 1 to 7 without an anti-reflection film.

[0168] Table 8

[0169]

[0170] While this disclosure has been described with reference to embodiments, it should be understood that this disclosure is 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.

[0171] Each example can provide an optical element with excellent anti-reflective properties.

Claims

1. An optical element, comprising: substrate; as well as The wave structure formed on the substrate includes: A first antireflective film having one or more layers formed opposite to the substrate; as well as Multiple fluctuation zones, and each fluctuation zone includes multiple structures. The following inequalities are satisfied: Where n p The refractive index of the first material forming the plurality of structures for light with a wavelength of 550 nm is κ. p It is the extinction coefficient of the first material, and n 1L It is the refractive index of the second material forming any one of the following layers for light with a wavelength of 550 nm, where any one layer is any one or more layers forming the first antireflective film.

2. The optical element according to claim 1, characterized in that, A wave structure is formed on the first surface of the substrate. Each of the plurality of structures comprises a plurality of structures having different widths along the direction of the first surface.

3. The optical element according to claim 1, characterized in that, In the one or more layers forming the first antireflective film, the layer with the lowest refractive index or the layer furthest from the substrate is formed of a second material.

4. The optical element according to claim 1, characterized in that, A wave structure is formed on the first surface of the substrate. The space surrounding the plurality of structures is filled with air, and The first antireflective film is formed on the plurality of structures within the width of each of the plurality of structures along the direction of the first surface.

5. The optical element according to claim 1, characterized in that, The spaces between the multiple structures are filled with a medium different from air. The first antireflective film is formed on the plurality of structures and the medium.

6. The optical element of claim 1, further comprising a second antireflective film formed between the substrate and the plurality of structures to cover the substrate. Its features are, The following inequalities must be satisfied: Where n 2L The refractive index of the third material forming any of the following layers for light with a wavelength of 550 nm is given by d. This "any" layer is any one or more layers forming the second antireflective coating. 2L It is the thickness of the third material layer, d 2L The unit is nm.

7. The optical element according to claim 6, characterized in that, In the layer or multiple layers forming the second antireflective film, the layer closest to the plurality of structures is formed of a third material.

8. The optical element according to claim 6, characterized in that, The second anti-reflective coating comprises a layer formed of a third material and a layer formed of a fourth material. The following inequalities are satisfied: Where n 2H It is the refractive index of the fourth material for light with a wavelength of 550nm.

9. The optical element according to claim 6, characterized in that, A wave structure is formed on the first surface of the substrate. The optical element further includes a third antireflective film formed between the second antireflective film and the plurality of structures within the width of each of the plurality of structures along the direction of the first surface, and The following inequalities are satisfied: Where n 3L It is the refractive index of the fifth material forming any of the following layers for light with a wavelength of 550 nm, where any of the layers is one or more layers forming the third antireflective coating.

10. The optical element according to claim 9, characterized in that, In the layer or multiple layers forming the third antireflective film, the layer closest to the plurality of structures is formed of a fifth material.

11. The optical element according to claim 9, characterized in that, The third anti-reflective coating comprises a layer formed of a fifth material and a layer formed of a sixth material. The following inequalities are satisfied: Where n 3H It is the refractive index of the sixth material for light with a wavelength of 550nm.

12. The optical element according to claim 1, characterized in that, The following inequalities must be satisfied: Where n s It is the refractive index of the material forming the substrate for light with a wavelength of 550 nm.

13. The optical element according to claim 1, characterized in that, A wave structure is formed on the first surface of the substrate. The following inequalities are satisfied: Where P is the pitch of the plurality of structures along the direction of the first surface.

14. The optical element according to claim 1, characterized in that, The first material includes at least one of silicon nitride, titanium oxide, gallium nitride, gallium arsenide, silicon carbide, aluminum oxide, and silicon oxide.

15. The optical element according to claim 1, characterized in that, The incident light in each fluctuation region is provided with a different phase modulation amount.

16. The optical element according to any one of claims 1 to 15, characterized in that, An optical element is a superlens that uses a wave structure to converge or diverge incident light.

17. An optical system comprising: The optical element according to any one of claims 1 to 16.

18. An image acquisition device, comprising: An optical system comprising an optical element according to any one of claims 1 to 16; as well as An image sensor is configured to capture images of objects using an optical system.

Images