Diffractive optical elements and methods for manufacturing diffractive optical elements

Abstract

This invention provides a diffractive optical element capable of readily achieving desired optical properties and a method for manufacturing the same. The diffractive optical element comprises: a first material layer (11) having a diffraction grating shape; and a second material layer (12) stacked on the first material layer (11). When viewed from above in the stacking direction (D) of the first material layer (11) and the second material layer (12), the diffraction grating shape forms a plurality of concentric rings (R). n ), ring zone (R) n The radius of the innermost ring (R1) is smaller than that of all the rings (R) n Any one of the intervals (P1 to P9).

Description

Technical Field

[0001] This invention relates to a diffractive optical element and a method for manufacturing a diffractive optical element. Background Technology

[0002] Patent Document 1 discloses a technique for maintaining high diffraction efficiency by preventing the collapse of the stepped surface and the shape in the vicinity when manufacturing a scanning lens with a diffraction lens structure by injection molding.

[0003] Patent document 2 discloses a method for reducing the deformation of the lens surface caused by the curing shrinkage of the resin when the resin is cured to make a diffractive optical element.

[0004] Patent document 3 discloses a technique for reducing the phase deviation of the transmission wavefront of light transmitted through a diffractive optical element.

[0005] Previous technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-041542

[0008] Patent Document 2: Japanese Patent Application Publication No. 2019-032518

[0009] Patent Document 3: Japanese Patent Application Publication No. 2015-011293 Summary of the Invention

[0010] The technical problem to be solved by the invention

[0011] When fabricating diffractive optical elements by bonding two materials, it is difficult to achieve the desired optical properties due to the shrinkage stress during material curing. In Patent Documents 2 and 3, the manufacturing process is complex. Patent Document 1 describes a technique for manufacturing diffractive lens structures via injection molding and does not involve fabricating diffractive optical elements by bonding two materials.

[0012] The purpose of this invention is to provide a diffractive optical element that can easily achieve the desired optical properties and a method for manufacturing the same.

[0013] means for solving technical problems

[0014] One aspect of the present invention provides a diffractive optical element comprising: a first material layer having a diffraction grating shape; and a second material layer stacked on the first material layer, wherein, when viewed from above in the stacking direction of the first and second material layers, the diffraction grating shape forms a plurality of concentric rings, wherein the radius of the innermost first ring among the plurality of rings is smaller than any of the intervals between the rings.

[0015] One aspect of the present invention provides a diffractive optical element comprising: a first material layer having a diffraction grating shape; and a second material layer stacked on the first material layer. When viewed from above in the stacking direction of the first and second material layers, the diffraction grating shape forms a plurality of concentric rings. In the diffractive optical element, when a reference wavelength is set to λ, the refractive index difference between the first and second material layers is set to Δn, the radius of each ring is set to r, an even-order phase difference function with the radius as a variable is set to φ(r), the initial phase of the phase difference function is set to C, and the remainder obtained by dividing the sum of φ(r) and C by 2π is set to MOD(r), and the shape of the structure forming each ring is defined using the formula MOD(r) × λ divided by 2π × Δn, C is greater than 0 and less than 2π.

[0016] In a method for manufacturing a diffractive optical element according to one aspect of the present invention, the diffractive optical element has: a first material layer having a diffraction grating shape; and a second material layer stacked on the first material layer. When viewed from above in the stacking direction of the first material layer and the second material layer, the diffraction grating shape forms a plurality of concentric rings. In the method for manufacturing the diffractive optical element, the radius of the innermost first ring among the plurality of rings is formed to be smaller than any of the intervals between the adjacent rings.

[0017] In a method for manufacturing a diffractive optical element according to one aspect of the present invention, the diffractive optical element comprises: a first material layer having a diffraction grating shape; and a second material layer stacked on the first material layer. When viewed from above in the stacking direction of the first and second material layers, the diffraction grating shape forms a plurality of concentric rings. In the method for manufacturing the diffractive optical element, when a reference wavelength is set to λ, the refractive index difference between the first and second material layers is set to Δn, the radius of each ring is set to r, an even-order phase difference function with the radius as a variable is set to φ(r), the initial phase of the phase difference function is set to C, and the remainder obtained by dividing the sum of φ(r) and C by 2π is set to MOD(r), and the shape of the structure forming each ring is defined using the formula MOD(r) × λ divided by 2π × Δn, C is set to a value greater than 0 and less than 2π to design the structure, and the diffraction grating shape is formed according to the design.

[0018] Invention Effects

[0019] According to the present invention, the desired optical properties can be easily obtained. Attached Figure Description

[0020] Figure 1This is a cross-sectional schematic diagram showing the structure of a diffractive optical element 100 as one embodiment of the diffractive optical element of the present invention.

[0021] Figure 2 Observing from direction D Figure 1 A planar schematic diagram of the diffractive optical element 100 shown.

[0022] Figure 3 It means Figure 1 A cross-sectional schematic diagram of a modified example of the diffractive optical element 100 shown.

[0023] Figure 4 It means Figure 1 A cross-sectional schematic diagram of another variation of the diffractive optical element 100 shown.

[0024] Figure 5 This is a schematic diagram illustrating a graph of the phase difference function φ(r) and an example of the shape of the structure Sn determined based on it.

[0025] Figure 6 This is a schematic diagram illustrating the structure of the first verification example.

[0026] Figure 7 This is a graph representing the results of the first verification example.

[0027] Figure 8 This is a graph representing the results of the first verification example.

[0028] Figure 9 This is a schematic diagram illustrating the structure of the second verification example.

[0029] Figure 10 This is a graph representing the results of the second verification example.

[0030] Figure 11 This is a graph representing the results of the second verification example.

[0031] Figure 12 This is a diagram illustrating the results of an embodiment. Detailed Implementation

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a cross-sectional schematic diagram through the optical axis showing the structure of a diffractive optical element 100, which is an embodiment of the diffractive optical element of the present invention. Figure 2 Observing from direction D Figure 1 A planar schematic diagram of the diffractive optical element 100 shown.

[0033] The diffractive optical element 100 includes: a glass lens 10; a first material layer 11 with a refractive index N1, stacked on the surface of the glass lens 10 in the direction of the optical axis K, i.e., direction A; a second material layer 12 with a refractive index N2, stacked on the first material layer 11; and a glass lens 13, stacked on the second material layer 12. The first material layer 11 and the second material layer 12 are layers each containing resin. The resins used for the first material layer 11 and the second material layer 12 are selected to satisfy the diffraction condition Δnd = λ. Here, λ is the wavelength of light, Δn is the difference in refractive index between the first material layer 11 and the second material layer 12 relative to the wavelength λ, and d is the height of the diffraction grating. To obtain high diffraction efficiency over a wide wavelength band, it is preferable to use a resin with a high refractive index and low dispersion in one of the first material layer 11 and the second material layer 12, and a resin with a low refractive index and high dispersion in the other. For example, ultraviolet-curable resins can be used in the first material layer 11 and the second material layer 12. Examples of ultraviolet-curable resins include acrylate resins and epoxy resins. Acrylic resins are particularly preferred as UV-curable resins. The first material layer 11 and the second material layer 12 may each contain particles of metal or metal oxide. Examples of particles contained in the first material layer 11 and the second material layer 12 include titanium oxide, zirconium oxide, indium tin oxide, and antimony tin oxide. As an example, the refractive index N1 is lower than the refractive index N2. The stacking direction of the glass lens 10, the first material layer 11, the second material layer 12, and the glass lens 13 is consistent with the direction of extension of the optical axis K, i.e., direction A. The direction orthogonal to direction A is referred to as direction B. The direction from the glass lens 13 in direction A toward the glass lens 10 is referred to as direction D.

[0034] exist Figure 1 In this design, glass lens 10 and glass lens 13 are respectively represented as flat plates, but these shapes can be any shape, such as concave lens shape or convex lens shape, depending on the optical characteristics or applications required by the diffractive optical element 100. Glass lens 10 and glass lens 13 can each be resin lenses.

[0035] Regarding the diffractive optical element 100, it is manufactured by preparing a glass lens 10 with a first material layer 11 formed on its surface using a mold or the like, and a glass lens 13 with resin coated on its surface; joining the first material layer 11 side of the glass lens 10 and the resin side of the glass lens 13; and curing the resin on the glass lens 13 side. Regarding the first material layer 11, for example, it can be shaped into a mold by cutting or the like, and its shape can be transferred to the resin by a molding process such as ultraviolet curing, heat curing, or injection molding.

[0036] The first material layer 11 has a plurality of convex surfaces on the side opposite to the glass lens 10. Figure 1 and Figure 2In the example, there are 10 structures S n (n is 1 to 10). Structure S n From and Figure 1 The position of the dashed line L1 perpendicular to direction A is towards the structure protruding from the second material layer 12.

[0037] like Figure 2 As shown, structure S1 has a circular shape when viewed from above. Figure 1 As shown, the height of structure S1 is greatest at its outer periphery (distance from the dashed line L1 in direction A), and lowest at the center of the inner side of the outer periphery (a value greater than 0). Structure S1 is configured to have a recess D1 on the inner side of its outer periphery.

[0038] like Figure 2 As shown, structure S k (k is 2-10) When viewed from above, it appears as a ring shape. For example... Figure 1 As shown, structure S k The height is greatest at the outer perimeter and lowest (=0) at the inner perimeter. Therefore, in structure S k and the structure S adjacent to its inner peripheral edge side k-1 Between them, a concave portion D is formed. k Additionally, in Figure 1 In the example, structure S n The height of all the outer edges is the same, and the diagram shows a dashed line L2 connecting its outer edges. Recess D n This is the area that is recessed from the dashed line L2 towards the dashed line L1. Hereinafter, the area from the dashed line L2 to the recess D will be described. n The distance from the end of the glass lens 10 on one side (i.e., the dashed line L1) is recorded as the concave portion D. n The depth.

[0039] Through structure S n The outer peripheral edge forms a diffraction grating shape for the first material layer 11. Specifically, as... Figure 2 As shown, when viewed from a top position in direction D, multiple concentric rings R are formed in the first material layer 11. n The shape of a diffraction grating (n = 1 to 10). The ring zone R n From structure S n The outer periphery is formed. Hereinafter, the annular band R... n The radius or diameter is collectively referred to as the annulus R. n path.

[0040] Furthermore, the following section defines the annular band R when the upper limit of n is set to 9. n With ring zone R n+1 The interval is recorded as interval P. n Interval Pn The concave portion D corresponding to direction B n+1 The width of the recess. That is, interval P1 corresponds to the width of the recess D2 in direction B, interval P2 corresponds to the width of the recess D3 in direction B, interval P3 corresponds to the width of the recess D4 in direction B, interval P4 corresponds to the width of the recess D5 in direction B, interval P5 corresponds to the width of the recess D6 in direction B, interval P6 corresponds to the width of the recess D7 in direction B, interval P7 corresponds to the width of the recess D8 in direction B, interval P8 corresponds to the width of the recess D9 in direction B, and interval P9 corresponds to the width of the recess D2 in direction B. 10 The width.

[0041] As diffractive optical elements, there are diffractive optical elements in which no structure exists near the optical axis. For example, cutting... Figure 1 The structure of structure S1 in the diffractive optical element 100 is described as a reference structure. This reference structure can be understood as follows: the diameter of the innermost ring R2 (in other words, the width of the recess D2 formed inside the ring R2) is greater than the diameters of the other recesses D3 to D2. 10 The width of each of the intervals P2 to P9.

[0042] In this reference structure, the width of the recess in direction B of the innermost structure S2 increases. Therefore, the shrinkage stress of the resin during the curing of the second material layer 12 acts more strongly on this recess. As a result, the area near the optical axis of the glass lens 13 becomes prone to concavity, making it difficult to obtain the desired optical properties.

[0043] On the other hand, in the diffractive optical element 100, a structure S1 is provided near the optical axis. Therefore, compared with the reference structure, the volume of the recess near the optical axis can be reduced by the structure S1. Therefore, the shrinkage of the resin during the curing of the second material layer 12 near the optical axis can be suppressed by the structure S1. As a result, the desired optical properties can be obtained by preventing the recess near the optical axis of the glass lens 13.

[0044] Through the diameter of the innermost annulus R1 (i.e., the width of the recess D1) in all recesses D n The width is not the maximum, which allows us to achieve the effect based on this structure S1. In other words, the diameter of the ring band R1 is smaller than that corresponding to other recesses D. k The aforementioned effect can be achieved by using any one of the width intervals P1 to P9. In other words, the diameter of the ring band R1 is smaller than that corresponding to the other recesses D. k The above effect can be achieved by using the maximum value among the width intervals P1 to P9.

[0045] Furthermore, even if the depth of recess D1 is different from that of other recesses D kThe same depth can achieve the above-mentioned effect. However, as in the diffractive optical element 100, it is preferable that the depth of the recess D1 is smaller than that of the other recesses D. k The depth of the recess D1 is reduced by this configuration, which also helps to mitigate shrinkage stress more effectively. Furthermore, it improves the optical properties of the diffraction optical element 100, such as its diffraction efficiency.

[0046] Furthermore, in the diffractive optical element 100, the spacing P1 is greater than the radius of the annular zone R1. With this configuration, the desired optical characteristics can be achieved when the diffractive optical element 100 is applied to lens devices such as cameras, especially to lenses positioned on the subject side.

[0047] Furthermore, in the diffractive optical element 100, the spacing P1 is at all spacings P k The maximum value is in the middle. With this configuration, the desired optical characteristics can be achieved when the diffractive optical element 100 is applied to the lens in the above-described lens device, especially to the lens disposed on the subject side.

[0048] Additionally, interval P n (However, the upper limit of n is 9) can be reduced as the value of n increases. In this way, the desired optical properties can be satisfied.

[0049] exist Figure 1 In the example, structure S n The heights of the outer edges of all structures S1 and S2 are the same. However, in order to adjust the optical path length (phase deviation) of the diffractive optical element 100, for example, the height of the outer edge of structure S1 can be made to be the same as that of other structures S1. k The heights of their outer edges are different.

[0050] For example, suppose that there is a convex error of 35 nm on the transmission wavefront in the diffractive optical element 100. In this case, if the adjustment amount of the height of the outer peripheral edge of the structure S1 is set as Δd, the required correction amount ΔW (=-35 nm) of the transmission wavefront can be expressed by the following equation (F0).

[0051] ΔW=(N2-N1)×Δd……(F0)

[0052] When the refractive index N1 of the first material layer 11 is less than the refractive index N2 of the second material layer 12, the adjustment amount Δd becomes negative. That is, as... Figure 3 As illustrated, by making the height of the outer periphery of structure S1 higher than that of other structures S... k The reduction in the height of the outer periphery, corresponding to the absolute value of the adjustment amount Δd, can eliminate errors in the transmission wavefront. On the other hand, when the refractive index N1 of the first material layer 11 is greater than the refractive index N2 of the second material layer 12, the adjustment amount Δd becomes positive. That is, as... Figure 4 As illustrated, by making the height of the outer periphery of structure S1 higher than that of other structures S... k The increase in the height of the outer perimeter edge corresponds to the absolute value of the adjustment amount Δd, which can eliminate the error of the transmitted wave surface.

[0053] exist Figure 1 In the example, among the intervals P1 to P9, interval P1 is the largest. Therefore, in order to make the diameter of the ring belt R1 (i.e., the width of the recess D1) in all recesses D... n The width of the ring R1 must not be the maximum, and the radius of the ring R1 must satisfy the condition that it is less than the interval P1.

[0054] The structure S of the first material layer 11 n Shape D(S) n In this process, the reference wavelength determined by the purpose of the diffractive optical element 100 is set as λ, and the refractive index difference (=N1-N2) between the first material layer 11 and the second material layer 12 is set as Δn. The annular R... n The radius (hereinafter referred to as "r") n Let φ(r) be the even-order phase difference function of the variable. n ), set the initial phase of the phase difference function to C, and set φ(r n The remainder obtained by dividing the sum of r and C by 2π is set as MOD(r). n In the case of MOD(r), it is possible to obtain the MOD(r) n The following equation (F1) defines D(S) as λ divided by 2π×Δn. n The design of structure S n Based on the shape of the glass lens 10, the first material layer 11 can be formed on the glass lens 10 by means of a mold or the like.

[0055] D(S n )={MOD(r n )×λ} / {2π×Δn}……(F1)

[0056] As an example, the phase difference function φ(r) can be expressed by equation (F2). n C2, C4, C6, C8, and C in equation (F2) 10 These are pre-defined coefficients. As illustrated in equation (F2), they are expected to be used in the design of structure S. n The phase difference function of the shape does not have an extremum within the effective optical diameter range of the diffractive optical element 100. Thus, chromatic aberration correction is possible. Furthermore, in special applications of the diffractive optical element 100, such as low-profile lenses for small camera modules in mobile phones or automotive devices, or ultra-wide-angle lenses for projectors, it is desirable for the phase difference function to have an extremum.

[0057] φ(r n )=C2r n 2 +C4r n 4 +C6r n 6 +C8r n 8 +C 10 r n 10 ...(F2)

[0058] Figure 5 It is used to explain the phase difference function φ(r) n The diagram and the structure S determined based on the diagram. n A schematic diagram of an example of its shape. Figure 5 The horizontal axis represents the distance. Figure 1 The distance of the optical axis K on the direction B of the diffractive optical element 100. Figure 5 The vertical axis represents the phase difference function φ(r) n The value of ). Figure 5 The thick solid line in the diagram schematically represents structure S. n The shape. Furthermore, since the graph of the phase difference function is symmetrical, therefore in Figure 5 Only half of the image is shown.

[0059] exist Figure 5 In the example, the phase difference function φ(r) n The distance where the value is a multiple of 2π is set as the annular zone R. n The radius. And, in Figure 5 In the example, the initial phase C (the value when the radius is 0) is 1.8π, which is greater than 0. The initial phase C is a value corresponding to the depth of the recess D1. By making this value greater than 0, the depth of the recess D1 can be made smaller than that of other recesses D. k The depth.

[0060] The following is for reference. Figures 6 to 12 The results of verification for the diffractive optical element 100 are explained below. The materials, amounts, proportions, processing contents, and processing steps shown below can be appropriately modified without departing from the spirit of the invention. The scope of the invention should not be interpreted limitingly by the specific examples shown below.

[0061] Figure 6 This is a schematic diagram showing the structure of the diffractive optical element in the first verification example. (Example) Figure 6As shown, in the first verification example, the diameter of the diffractive optical element is set to 54.50 mm (the effective optical diameter is 44 mm), and the distance between the surface of the glass lens 10 opposite to the side of the glass lens 13 and the surface of the glass lens 10 in the glass lens 13 is set to 2.5 mm. Furthermore, in the first verification example, C2 in formula (F2) is set to -0.45934, C4 to 0.000276, and C6, C8, and C... 10 Phase difference function φ(r) set to 0 respectively n ), setting λ to 633 nm, Δd to 0.06, and varying the initial phase C between 0 and 2π to construct structure S n Shape design. Figure 7 This represents the change in the radius of the ring band R1 and the interval P1 relative to the initial phase C in the first verification example. Figure 8 This represents the structure S when the initial phase C is set to 1.8π in the first verification example. n The interval P between them j The graph shows (j = 0, 1, 2, 3, ...). Additionally, the value corresponding to interval P0 is set as the radius of the annular band R1.

[0062] Figure 9 This is a schematic diagram showing the structure of the diffractive optical element in the second verification example. (Example) Figure 9 As shown, in the second verification example, the diameter of the diffractive optical element is set to 77.50 mm (the effective optical diameter is 56 mm), and the distance between the surface of the glass lens 10 opposite to the side of the glass lens 13 and the surface of the glass lens 10 in the glass lens 13 is set to 2.2 mm. Furthermore, in the second verification example, C2 in formula (F2) is set to -0.19824 and C4 is set to 2.37 × 10⁻⁶. -5 C6 is set to 2.31 × 10 -9 C8 is set to -1.7336×10 -11 C 10 Set to 1.09×10 -14 Phase difference function φ(r) n The structure S was constructed by setting λ to 633 nm, Δd to 0.06, and varying the initial phase C between 0 and 2π. n Shape design.

[0063] Figure 10 This represents the change in the radius of the ring band R1 and the interval P1 relative to the initial phase C in the second verification example. Figure 11 This refers to structure S when the initial phase C is set to 1.8π in the second verification example. n The interval P between them jThe graph shows (j = 0, 1, 2, 3, ...). Additionally, the value corresponding to interval P0 is set as the radius of the annular band R1.

[0064] To satisfy the aforementioned condition that the radius of the ring R1 is smaller than the interval P1, as follows: Figure 7 and Figure 10 As shown, the initial phase C is set to a value greater than the radius of the ring band R1 and the same as the initial phase C of the interval P1 (and...). Figure 7 ( Figure 10 The value of the initial phase C corresponding to the intersection of the two graphs in the diagram is sufficient. Figure 7 In the example, by setting the initial phase C to be greater than 1.326π and less than 2π, for example, Figure 8 As shown, the above conditions can be met. In Figure 10 In the example, by setting the initial phase C to be greater than 1.327π and less than 2π, for example, Figure 11 As shown, the above conditions can be met.

[0065] In the first verification example, the diffractive optical element 100 was manufactured by setting the materials of glass lens 10 and glass lens 13 to BSC7 (manufactured by HOYA Corporation) and the initial phase C to 1.8π, and the result is recorded as Example 1. The shape error of the design value at the optical axis position of the diffractive optical element 100 of Example 1 is concave by 20 nm, and the error of the design value at the transmission wavefront at the optical axis position is less than 10 nm.

[0066] In the first verification example, the result of manufacturing a diffractive optical element 100 with the materials of glass lens 10 and glass lens 13 set to BSC7 and the initial phase C set to 0π is recorded as Reference Example 1a. The shape error of the design value in the optical axis position of the diffractive optical element 100 from Reference Example 1a is concave 60 nm, and the design error in the transmission wavefront from the optical axis position is convex 30 nm.

[0067] In the second verification example, the diffractive optical element 100 was manufactured with the material of glass lens 10 set to S-LAH55V (manufactured by OHARA INC.), the material of glass lens 13 set to S-FPL51 (manufactured by OHARA INC.), and the initial phase C set to 1.8π. The result is described as Example 2. The shape error of the design value at the optical axis position of the diffractive optical element 100 of Example 2 is concave by 40 nm, and the error of the design value at the transmission wavefront at the optical axis position is convex by 35 nm.

[0068] In the second verification example, the result of manufacturing the diffractive optical element 100 with the material of glass lens 10 set to S-LAH55V, the material of glass lens 13 set to S-FPL51, and the initial phase C set to 0π is recorded as Reference Example 2a. The shape error of the design value in the optical axis position of the diffractive optical element 100 from Reference Example 2a is concave 100nm, and the error of the design value in the transmission wavefront from the optical axis position is convex 80nm.

[0069] In the second verification example, the diffractive optical element 100 was manufactured by setting the material of glass lens 10 to S-LAH55V, the material of glass lens 13 to S-FPL51, setting the initial phase C to 1.8π, and making the height of structure S1 less than the design value of 58.4 nm. The result is described as Example 3. The shape error of the diffractive optical element 100 at the optical axis position relative to the design value is less than 10 nm, and the error of the design value at the transmission wavefront relative to the optical axis position is less than 10 nm.

[0070] The results summarizing the above embodiments are shown below. Figure 12 Additionally, in Figure 12 In the embodiments and reference examples, acrylate monomers dispersed with ITO nanoparticles are used as the second material layer 12 on the side of the glass lens 13, and acrylate monomers dispersed with ZrO2 nanoparticles are used as the first material layer 11 on the side of the glass lens 10. Based on this result, it is known that by making the initial phase C greater than 0, the shape error and the transmission wavefront error can be reduced. Furthermore, it is known that by adjusting the height of the structure S1, the shape error and the transmission wavefront error can be further reduced.

[0071] In the above explanation, the ring band R n The shape is described as circular, but the circular shape in this specification not only refers to a perfect circle, but also includes the concept of tolerance. Ring R n The ring R when the shape is not a perfect circle n The radius refers to the annular band R when viewed from above. n Any point on the ring and the ring R furthest from that point n Half the straight-line distance between points on the ring R. n The ring R when the shape is not a perfect circle n The diameter refers to the annular band R when viewed from above. n Any point on the ring and the ring R furthest from that point n The straight-line distance between points on the graph.

[0072] Similarly, multiple concentric rings R n Not only referring to each circumferential zone R n Its shape is a perfect circle, and it also includes the concept of tolerance. Strictly speaking, the various rings R arranged in concentric circles...n The centers are not in the same location, and tolerances may be included.

[0073] Circular band R n The shape can be, for example, an ellipse. Ring R n When the shape is elliptical, the radius refers to the annulus R when viewed from above. n The straight-line distance between any point on the ellipse and the point where the extension of the line connecting that point to the center of the ellipse intersects the ellipse is half the distance between the ellipse and the point where the line intersects the ellipse. (R) n When the shape is elliptical, the diameter refers to the annulus R when viewed from above. n The straight-line distance between any point on the ellipse and the point where the extension of the line connecting that point to the center of the ellipse intersects the ellipse.

[0074] The diffractive optical element 100 can be cut as needed for use in the product. For example, a portion further outward than the annular band R5 can be cut as the final product.

[0075] As explained above, the following items are disclosed in this specification. Additionally, components corresponding to those in the above embodiments are shown in parentheses, but the scope is not limited thereto. (1)

[0077] A diffractive optical element (diffractive optical element 100) comprises: a first material layer (first material layer 11) having a diffraction grating shape; and a second material layer (second material layer 12) stacked on the first material layer, wherein, when viewed from above in the stacking direction (direction D) of the first and second material layers, the diffraction grating shape forms a plurality of concentric rings (rings R). n In the diffractive optical element (diffractive optical element 100),

[0078] The radius of the innermost first annulus (annulus R1) among the above annulus bands is smaller than that of any of the intervals between the annulus bands. (2)

[0080] According to the diffractive optical element described in (1), wherein,

[0081] The diameter of the first annulus is smaller than any of the intervals between the annulus bands. (3)

[0083] According to the diffractive optical element described in (1), wherein,

[0084] The radius of the first annulus is smaller than the maximum value of the interval between the annulus and the other annulus. (4)

[0086] According to any one of (1) to (3), the diffractive optical element, wherein,

[0087] The first interval (interval P1) between the second ring (ring R2) adjacent to the first ring and the first ring is greater than the radius of the first ring. (5)

[0089] According to the diffractive optical element described in (4), wherein,

[0090] The first interval mentioned above is the largest among the intervals of each annulus. (6)

[0092] According to any one of (1) to (5), the diffractive optical element, wherein,

[0093] The depth of the inner recess (recess D1) of the first ring in the structure (structure S1) forming the first ring is less than the depth of the recesses between the structures forming each ring. (7)

[0095] According to any one of (1) to (6), the diffractive optical element, wherein,

[0096] When the reference wavelength is set to λ

[0097] Let the refractive index difference between the first material layer and the second material layer be Δn.

[0098] Let the radius of each annulus be r(r n ),

[0099] Let the even-order phase difference function, with the aforementioned radius as the variable, be denoted as φ(r)(φ(r)). n )),

[0100] Let the initial phase of the above phase difference function be C.

[0101] Let the remainder obtained by dividing the sum of φ(r) and C by 2π be MOD(r)(MOD(r)). n )),

[0102] When the shape of the structure forming each annulus is defined by dividing MOD(r)×λ by 2π×Δn,

[0103] C is greater than 0 and less than 2π. (8)

[0105] According to any one of (1) to (7), the diffractive optical element, wherein,

[0106] The height of the structure forming the first annular zone is different from the height of the structures forming the other annular zones besides the first annular zone. (9)

[0108] According to the diffractive optical element described in (8), wherein,

[0109] The refractive index of the first material layer is less than that of the second material layer.

[0110] The height of the structure forming the first annular zone is less than the height of the structures forming the other annular zones besides the first annular zone. (10)

[0112] According to the diffractive optical element described in (8), wherein,

[0113] The refractive index of the first material layer is greater than that of the second material layer.

[0114] The height of the structure forming the first annular zone is greater than the height of the structures forming the other annular zones besides the first annular zone. (11)

[0116] According to any one of (1) to (10), the diffractive optical element, wherein,

[0117] The spacing between the rings narrows from the center outwards. (12)

[0119] A diffractive optical element comprises: a first material layer having a diffraction grating shape; and a second material layer stacked on the first material layer, wherein, when viewed from above in the stacking direction of the first and second material layers, the diffraction grating shape forms a plurality of concentric rings, wherein in the diffractive optical element,

[0120] When the reference wavelength is set to λ

[0121] Let the refractive index difference between the first material layer and the second material layer be Δn.

[0122] Let the radius of each ring be r.

[0123] Let the even-order phase difference function, with the aforementioned radius as the variable, be φ(r).

[0124] Let the initial phase of the above phase difference function be C.

[0125] Let MOD(r) be the remainder obtained by dividing the sum of φ(r) and C by 2π.

[0126] When the shape of the structure forming each annulus is defined by dividing MOD(r)×λ by 2π×Δn,

[0127] C is greater than 0 and less than 2π. (13)

[0129] According to the diffractive optical element described in (12), wherein,

[0130] C is greater than the value of C, which is the same as the radius of the innermost first annulus among the aforementioned annulus and the interval between the first annulus and the second annulus adjacent to the first annulus. (14)

[0132] According to the diffractive optical element described in (12) or (13), wherein,

[0133] The aforementioned phase difference function does not have extreme values ​​within the effective optical diameter range. (15)

[0135] A method for manufacturing a diffractive optical element, the diffractive optical element comprising: a first material layer having a diffraction grating shape; and a second material layer stacked on the first material layer, wherein, when viewed from above in the stacking direction of the first and second material layers, the diffraction grating shape forms a plurality of concentric rings, in the method for manufacturing the diffractive optical element...

[0136] The radius of the innermost first annulus among the above plurality of annulus is formed to be smaller than any of the intervals between the adjacent annulus. (16)

[0138] A method for manufacturing a diffractive optical element, the diffractive optical element comprising: a first material layer having a diffraction grating shape; and a second material layer stacked on the first material layer, wherein, when viewed from above in the stacking direction of the first and second material layers, the diffraction grating shape forms a plurality of concentric rings, in the method for manufacturing the diffractive optical element...

[0139] When the reference wavelength is set to λ

[0140] Let the refractive index difference between the first material layer and the second material layer be Δn.

[0141] Let the radius of each ring be r.

[0142] Let the even-order phase difference function, with the aforementioned radius as the variable, be φ(r).

[0143] Let the initial phase of the above phase difference function be C.

[0144] Let MOD(r) be the remainder obtained by dividing the sum of φ(r) and C by 2π.

[0145] When the shape of the structure forming each annulus is defined by dividing MOD(r)×λ by 2π×Δn,

[0146] The above structure is designed with C set to a value greater than 0 and less than 2π.

[0147] The diffraction grating shape is formed according to the above design. (17)

[0149] According to the manufacturing method of the diffractive optical element described in (16), wherein,

[0150] The value of C is such that the radius of the first annulus, which is greater than the smallest diameter among the aforementioned annulus, is the same as the interval between the first annulus and the second annulus adjacent to the first annulus.

[0151] Various embodiments have been described above with reference to the accompanying drawings, but the present invention is not limited to these examples. Obviously, those skilled in the art will be able to conceive of various modifications or alterations within the scope of the claims, and these modifications or alterations should naturally be understood to fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0152] Furthermore, the contents of Japanese Patent Application No. 2020-063803, filed on March 31, 2020, are incorporated herein by reference.

[0153] Symbol Explanation

[0154] L1, L2 - dashed line L, S1~S 10 -Structures, R1~R 10 - Annular band, D1~D 10 - Recessed portion, P1~P9 - Spacing, 10, 13 - Glass lenses, 11 - First material layer, 12 - Second material layer, 100 - Diffractive optical element, K - Optical axis.

Claims

1. A diffractive optical element having: a first material layer having a diffractive grating shape; and a second material layer laminated on the first material layer, the diffractive grating shape forming a plurality of annular zones in a concentric circular shape in a state viewed from a direction of lamination of the first material layer and the second material layer, in the diffractive optical element, a first annular zone that is innermost among the plurality of annular zones has a radius smaller than a maximum value among intervals of the annular zones, recesses between structures that form the first annular zone and structures that form the annular zones other than the first annular zone are filled with the second material layer, the structure that forms the first annular zone has a configuration having a recess inside an outer periphery, a depth of the recess of the structure that forms the first annular zone is smaller than a depth of recesses between the structures that form the annular zones other than the first annular zone.

2. The diffractive optical element according to claim 1, wherein a diameter of the first annular zone is smaller than the maximum value among the intervals of the annular zones.

3. The diffractive optical element according to claim 1, wherein the radius of the first annular zone is smaller than the maximum value among the intervals of the annular zones.

4. The diffractive optical element according to any one of claims 1 to 3, wherein a first interval between a second annular zone adjacent to the first annular zone and the first annular zone is larger than the radius of the first annular zone.

5. The diffractive optical element according to claim 4, wherein the first interval is the largest among the intervals of the annular zones.

6. The diffractive optical element according to any one of claims 1 to 3, 5, wherein a reference wavelength is set as λ, a refractive index difference between the first material layer and the second material layer is set as Δn, a radius of the annular zones is set as r, a phase difference function of an even order with the radius as a variable is set as φ(r), a start phase of the phase difference function is set as C, a remainder obtained by dividing an addition value of φ(r) and C by 2π is set as MOD(r), in a case where a shape of the structure that forms the annular zones is defined by a formula of MOD(r) x λ divided by 2π x Δn, C is larger than 0 and smaller than 2π.

7. The diffractive optical element according to any one of claims 1 to 3, 5, wherein a height of the structure that forms the first annular zone is different from a height of the structure that forms the annular zones other than the first annular zone.

8. The diffractive optical element according to claim 7, wherein a refractive index of the first material layer is smaller than a refractive index of the second material layer, the height of the structure that forms the first annular zone is smaller than the height of the structure that forms the annular zones other than the first annular zone.

9. The diffractive optical element according to claim 7, wherein the refractive index of the first material layer is larger than the refractive index of the second material layer, the height of the structure that forms the first annular zone is larger than the height of the structure that forms the annular zones other than the first annular zone.

10. The diffractive optical element according to any one of claims 1 to 3, 5, 8, 9, wherein the intervals of the annular zones are narrower as going from the center to the outside.

11. A diffractive optical element having: a first material layer having a diffractive grating shape; and a second material layer laminated on the first material layer, the diffractive grating shape forming a plurality of annular zones in a concentric circular shape in a state of viewing from a direction of lamination of the first material layer and the second material layer, a structure forming a first annular zone that is innermost among the plurality of annular zones and structures forming each annular zone are filled with recesses between each other by the second material layer, the structure forming the first annular zone is configured to have a recess inside an outer periphery, a depth of the recess of the structure forming the first annular zone is smaller than a depth of the recess between each of the structures forming each annular zone, in the diffractive optical element, a reference wavelength is set to λ, a refractive index difference between the first material layer and the second material layer is set to Δn, a radius of each annular zone is set to r, a phase difference function of an even order with the radius as a variable is set to φ(r), a start phase of the phase difference function is set to C, a remainder obtained by dividing an addition value of φ(r) and C by 2π is set to MOD(r), a shape of the structure forming each annular zone is defined using a formula of MOD(r) x λ divided by 2π x Δn, and C is greater than 0 and smaller than 2π.

12. The diffractive optical element according to claim 11, wherein C is greater than a value of C in which a radius of a first annular zone that is innermost among the plurality of annular zones is the same as a spacing between the first annular zone and a second annular zone adjacent to the first annular zone.

13. The diffractive optical element according to claim 11 or 12, wherein the phase difference function does not have an extreme value in a range of an optical effective diameter.

14. A manufacturing method of a diffractive optical element having: a first material layer having a diffractive grating shape; and a second material layer laminated on the first material layer, the diffractive grating shape forming a plurality of annular zones in a concentric circular shape in a state of viewing from a direction of lamination of the first material layer and the second material layer, in the manufacturing method of the diffractive optical element, a radius of a first annular zone that is innermost among the plurality of annular zones is formed to be smaller than a maximum value among spacings of adjacent annular zones, a structure forming the first annular zone and structures forming each annular zone are filled with recesses between each other by the second material layer, the structure forming the first annular zone is configured to have a recess inside an outer periphery, and a depth of the recess of the structure forming the first annular zone is smaller than a depth of the recess between each of the structures forming each annular zone.

15. A manufacturing method of a diffractive optical element having: a first material layer having a diffractive grating shape; and a second material layer laminated on the first material layer, the diffractive grating shape forming a plurality of annular zones in a concentric circular shape in a state of viewing from a direction of lamination of the first material layer and the second material layer, in the manufacturing method of the diffractive optical element, a radius of a first annular zone that is innermost among the plurality of annular zones is formed to be smaller than a maximum value among spacings of adjacent annular zones, a structure forming the first annular zone and structures forming each annular zone are filled with recesses between each other by the second material layer, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the structure forming the first annular zone has a concave portion inside the outer periphery, a depth of the concave portion of the structure forming the first annular zone is smaller than a depth of the concave portion between the structures forming the respective annular zones, the manufacturing method of the diffractive optical element, a reference wavelength is set to λ, a difference in refractive index between the first material layer and the second material layer is set to Δn, a radius of each annular zone is set to r, a phase difference function of even order with the radius as a variable is set to φ(r), a starting phase of the phase difference function is set to C, a remainder obtained by dividing an addition value of φ(r) and C by 2π is set to MOD(r), in a case where a shape of the structure forming each annular zone is defined by an expression of MOD(r) x λ divided by 2π x Δn, C is designed to be a value larger than 0 and smaller than 2π, the diffractive grating shape is formed according to the design.

16. The manufacturing method of the diffractive optical element according to claim 15, wherein C is made larger than a value of C which is the same as a radius of a first annular zone of a smallest diameter among the plurality of annular zones and a spacing between the first annular zone and a second annular zone adjacent to the first annular zone.

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