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

Abstract

The invention relates to an optical system, an optical element, an image pickup apparatus, and a lens apparatus. An optical system includes at least one lens, and a meta-lens having a lens surface that produces a phase change in a wavefront of light passing through the meta-lens. A phase function of the lens surface includes an inflection point, and the phase function of the lens surface represents a phase change amount of the wavefront corresponding to a position in a radial direction of the meta lens.

Description

Technical Field

[0001] One of the aspects of the embodiments relates generally to optical systems, and more particularly to optical systems suitable for digital video cameras, digital still cameras, broadcast cameras, film-based cameras, surveillance cameras, vehicle-mounted (on-board) cameras, distance measurement cameras, and the like. Background Art

[0002] An optical system for an image pickup device has recently been required to have a reduced size. Japanese Patent Laid-Open No. 2021-71727 discloses an optical system having a so-called meta-lens having a positive refractive power.

[0003] The metalens disclosed in Japanese Patent Laid-Open No. 2021-71727 corrects chromatic aberration, but its refractive power is small and cannot share the refractive power of another lens. Therefore, the effect of the metalens disclosed in Japanese Patent Application Laid-Open No. 2021-71727 in correcting various aberrations other than chromatic aberration (such as spherical aberration, coma, field curvature, astigmatism, and distortion) is limited. In addition, the metalens disclosed in Japanese Patent Laid-Open No. 2021-71727 has a phase function that decreases monotonically from the center to the periphery, but the refractive power increases monotonically from the center to the periphery, so spherical aberration, field curvature, and astigmatism are likely to occur. The phase function is a function that expresses the phase change amount of the wavefront of light passing through the metalens corresponding to the radial position of the metalens (the phase change amount of the wavefront before and after the light passes through the metalens). As described above, the optical system disclosed in Japanese Patent Laid-Open No. 2021-71727 has difficulty in satisfactorily correcting various aberrations other than chromatic aberration from the image center to the image periphery. Summary of the invention

[0004] An optical system according to one aspect of the present disclosure includes at least one lens and a metalens having a lens surface, wherein the lens surface produces a phase change in a wavefront of light passing through the metalens, wherein a phase function of the lens surface includes an inflection point, and the phase function of the lens surface represents an amount of phase change of the wavefront corresponding to a position in a radial direction of the metalens.

[0005] An optical system according to another aspect of the present disclosure includes at least one lens and a metalens having a lens surface, wherein the lens surface produces a phase change in a wavefront of light passing through the metalens. The lens surface includes a structure having a plurality of convex portions. The size of each convex portion changes in a radial direction according to a predetermined rule.

[0006] An optical system according to another aspect of the present disclosure includes at least one lens, and a metalens having a lens surface, the lens surface producing a phase change in a wavefront of light passing through the metalens, wherein a phase function of the lens surface includes a critical point in a peripheral portion in a radial direction of the metalens, the phase function of the lens surface representing an amount of phase change of the wavefront corresponding to a position in the radial direction.

[0007] An optical element according to another aspect of the present disclosure includes a lens surface that produces a phase change in a wavefront of light passing through the optical element. A phase function of the lens surface includes an inflection point, and the phase function of the lens surface represents an amount of phase change of the wavefront corresponding to a position in a radial direction of the metalens.

[0008] An image pickup device and a lens device each having one of the above optical systems also constitute another aspect of the present disclosure.

[0009] Further features of various embodiments of the present disclosure will become apparent from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a cross-sectional view of the optical system according to Example 1 in a state in which the optical system is focused at infinity.

[0011] Figure 2 is a longitudinal aberration diagram of the optical system according to Example 1 in an infinity focused state.

[0012] Figure 3 The phase function of the metalens surface according to Example 1 is illustrated.

[0013] Figure 4 A change in the filling rate near the critical point of the phase function of the metalens surface according to Example 1 is illustrated.

[0014] Figure 5 A change in the filling rate near the inflection point of the phase function of the metalens surface according to Example 1 is illustrated.

[0015] Figure 6 is a cross-sectional view of the optical system according to Example 2 in a state where the optical system is focused at infinity.

[0016] Figure 7 is a longitudinal aberration diagram of the optical system according to Example 2 in an infinity focused state.

[0017] Figure 8 The phase function of the metalens surface according to Example 2 is illustrated.

[0018] Fig. 9A change in the filling rate near the inflection point of the phase function of the metalens surface according to Example 2 is illustrated.

[0019] Fig.10 is a cross-sectional view of the optical system according to Example 3 in a state in which the optical system is focused at infinity.

[0020] Fig.11 is a longitudinal aberration diagram of the optical system according to Example 3 in the infinity focused state.

[0021] Fig.12 The phase function of the metalens surface according to Example 3 is illustrated.

[0022] Fig.13 The change in the filling rate near the inflection point of the phase function of the metalens surface according to Example 3 is illustrated.

[0023] Fig.14 is a cross-sectional view of the optical system according to Example 4 in a state in which the optical system is focused at infinity.

[0024] Fig.15 is a longitudinal aberration diagram of the optical system according to Example 4 in the infinity focused state.

[0025] Fig.16 The phase function of the metalens surface according to Example 4 is illustrated.

[0026] Fig.17 The change in the filling rate near the critical point of the phase function of the metalens surface according to Example 4 is illustrated.

[0027] Fig.18 The change in the filling rate near the inflection point of the phase function of the metalens surface according to Example 4 is illustrated.

[0028] Fig.19A and Fig.19B Schematic diagram of the subwavelength structure of the metalens.

[0029] Fig. 20A and Fig. 20B The columnar structure of the prism is explained.

[0030] Fig.21A and Fig.21B The columnar structure of the column is explained.

[0031] Fig.22A and Fig. 22B The columnar structure of the hexagonal prism is explained.

[0032] Fig.23 is a schematic diagram of a metalens surface having a phase function including an inflection point.

[0033] Fig.24is a schematic diagram of a metalens surface having a phase function including a critical point.

[0034] Fig.25 The graph shows the relationship between the value of the ratio of the length of the columnar structure to the size of the substrate and the filling rate (filling factor).

[0035] Fig.26A , Fig.26B and Fig.26C The relationship between the filling rate and the amount of phase change is shown in the figure.

[0036] Fig. 27 is a schematic diagram of an image pickup device.

[0037] Fig.28 is a schematic diagram of the lens arrangement. DETAILED DESCRIPTION

[0038] Now, with reference to the accompanying drawings, a detailed description of embodiments according to the present disclosure will be given. Corresponding elements in the various drawings will be marked with the same reference numerals, and their repeated description will be omitted.

[0039] Figure 1 , Figure 6 , Fig.10 and Fig.14 : is a cross-sectional view of the optical system L0 in the infinity focused state according to Examples 1 to 4. The optical system L0 according to each example is used for a lens device and an image pickup device such as a digital video camera, a digital still camera, a broadcast camera, a film-based camera, a surveillance camera, an in-vehicle camera (on-board camera), and a distance measuring camera, and an interchangeable lens.

[0040] In each cross-sectional view, the left side is the object side, and the right side is the image side. In the case where the optical system L0 according to each example is used in an optical device such as a projector, the left side is the screen side, and the right side is the projected image side.

[0041] Each arrow shown in each cross-sectional view indicates the movement direction of the lens during focusing from infinity to a short (or close) distance. In each example, the entire optical system L0 moves from the image side to the object side during focusing. Focusing can be performed by moving only a portion of the lens in the optical system L0 from the image side to the object side or from the object side to the image side.

[0042] In each cross-sectional view, SP represents an aperture stop (aperture). IP represents an image plane. In the case where the optical system L0 according to each example is used as an imaging optical system in a digital still camera or a digital video camera, an imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is placed on the image plane IP. In the case where the optical system L0 according to each example is used as an imaging optical system of a film-based camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP. FL represents an optical block corresponding to an optical filter, a panel, a crystal low-pass filter, an infrared cut filter, etc.

[0043] The optical system L0 according to each example includes at least one (one or more) lens and a metalens (optical element) ML. In this example, the metalens ML has a lens surface MLS, which is at least one of a lens surface on the object side and a lens surface on the image side. The lens surface MLS has a sub-wavelength structure including a plurality of sub-wavelength-sized columnar structures (convex portions), and causes a phase change in the wavefront of light passing through the lens surface MLS along the light traveling direction.

[0044] A description will now be given of the principle by which light is refracted by the sub-wavelength structure of the metalens ML. Fig.19A and Fig.19B is a schematic diagram of the subwavelength structure of the metalens ML. In the subwavelength structure, a columnar structure is provided on the substrate surface so that the size (thickness) of the subwavelength columnar structure changes according to a predetermined rule in the radial direction of the lens surface. The substrate may be flat or curved. The size of each columnar structure is approximately equal to or less than the design wavelength. Each columnar structure is invisible to light, and in approximation, the columnar structure behaves as an average effective medium in which the refractive index of the air and the refractive index of the material of the columnar structure are averaged. In this case, as the size of the columnar structure increases, the refractive index of the effective medium becomes closer to the refractive index of the material of the columnar structure. As the size of the columnar structure decreases, the ratio (filling rate) of the columnar structure to the air decreases and the refractive index becomes closer to the refractive index of the air. A similar effect can be obtained even if the space between the columnar structures is filled with an arbitrary medium instead of air, so the medium filling the space between the columnar structures is not limited to air.

[0045] Therefore, changing the size of the columnar structure in the radial direction can provide the effect of continuously changing the refractive index of the effective medium in the radial direction. That is, in approximation, the metalens ML can be regarded as a refractive index distribution type lens whose refractive index changes in the radial direction. In the case of different refractive indices, even if the thickness is the same, the optical distance changes, so the amount of phase change of the wavefront of light before and after passing through the metalens ML changes according to the refractive index of the effective medium. In the metalens ML, the size of the columnar structure changes in the radial direction, so the amount of phase change is different at each position in the radial direction. That is, for example, in the case where a plane wave (parallel light beam) with aligned phases enters the metalens ML, the phase of the wavefront of the plane wave is offset according to the amount of phase change at each position in the radial direction of the metalens ML. As a result, the metalens ML acts as a lens that converges or diverges the plane wave. This example has described an example of a plane wave for simplicity, but for the wavefront of light that is not a plane wave, the metalens ML can be used as a lens that converges or diverges light using a similar principle.

[0046] Figure 2 , Figure 7 , Fig.11 and Fig.15 Aberration diagrams of the optical systems according to Examples 1 to 4 in an infinitely focused state, respectively.

[0047] In the spherical aberration diagram, Fno represents the F number. The spherical aberration diagram illustrates the spherical aberration amount for the design wavelength (the design wavelength in each example is illustrated separately). In the astigmatism diagram, S indicates the astigmatism amount on the sagittal image plane, and M indicates the astigmatism amount on the meridional image surface. The distortion diagram illustrates the distortion amount for the design wavelength.

[0048] A description will now be given of a characteristic structure of the optical system L0 according to each example.

[0049] The phase function Φ(h) of the lens surface MLS includes at least one of a critical point and an inflection point. Phase function is a function that represents the amount of phase change of the wavefront of light passing through the metalens ML corresponding to the position h in the radial direction of the metalens ML (the amount of phase change of the wavefront of light before and after passing through the metalens or the integrated value of the phase change). As described above, the metalens surface MLS causes a phase change in the wavefront of light passing through the metalens ML due to the subwavelength structure. In the case where the amount of phase change on the optical axis is set to 0, as Fig.19A and Fig.19BAs shown in , a phase change occurs at a position h in the radial direction relative to the optical axis. In the following description, unless otherwise specified, the phase change amount represents the relative phase change amount in the case where the phase change amount on the optical axis is set to 0, and the phase is expressed in radians (radians, radians, rads). The critical point is the phase function The first derivative of is 0 and the phase function The point where the sign of the value of the first derivative of changes before and after that point. The inflection point is the phase function The second derivative of is 0 and the phase function The point at which the sign of the value of the second derivative changes before and after that point.

[0050] exist Fig.19A In the subwavelength structure of the lens surface MLS, a columnar structure is provided on the substrate surface so that the size (thickness) of the columnar structure increases as the position moves away from the center of the optical axis at the left end in the radial direction of the lens surface MLS (the center of the lens surface MLS). The change in which the size of the columnar structure increases as the position moves away from the center of the optical axis in the radial direction of the lens surface MLS is repeated periodically along the radial direction of the lens surface MLS, wherein one cycle is defined as a time period until the phase change amount reaches -2π. The wavefront whose phase change is -2π is continuously connected to the wavefront whose phase change is 0, so in order to produce a phase change less than -2π (with a large absolute value), the arrangement of one cycle can be repeated again in sequence from the columnar structure whose phase change is actually 0. Therefore, repeating the phase change from 0 to 2π can provide an arbitrary negative phase change amount. As Fig.19A As shown in , in the case where a columnar structure is provided, the phase function starts from 0 and takes a negative value, so the metalens surface MLS has a positive refractive power near the optical axis.

[0051] exist Fig.19B In the sub-wavelength structure on the lens surface MLS, a columnar structure is provided on the surface of the substrate so that the size (thickness) of the columnar structure becomes smaller as the position moves away from the center of the optical axis (the center of the lens surface MLS) at the left end in the radial direction of the lens surface MLS. The change in which the size of the columnar structure increases as the position moves away from the center of the optical axis in the radial direction of the lens surface MLS is repeated periodically along the radial direction of the lens surface MLS. At this time, Fig.19A As in the case of , any positive phase change amount can be obtained by repeating the phase change from 0 to 2π, and the metalens surface MLS has a negative refractive power near the optical axis.

[0052] As mentioned above, the phase function The positive or negative phase change is expressed as the integrated value of the phase change from the center of the optical axis. The reference to which the value of is set to 0 does not necessarily have to be the center of the optical axis, and in fact there may be an uncertainty equal to a constant. This example assumes an axisymmetric optical system, so the phase function is also expressed as axisymmetric, but in non-axisymmetric optical systems, the phase function need not also be axisymmetric.

[0053] A description will now be given of the relationship between the amount of phase change and the columnar structure. As described above, when the ratio (filling rate) of the columnar structure changes according to the size of the columnar structure, the effective refractive index of the effective medium changes and a phase change occurs. The amount of phase change in the columnar structure can be obtained by performing electromagnetic field analysis based on, for example, rigorous coupled wave analysis (RCWA), finite difference time domain method (FDTD), etc.

[0054] A description will now be given of the definition of the filling rate F. Fig. 20A Schematically illustrates the Fig.19A and Fig.19B The continuous structure shown in FIG. 1 is a virtually cut-out unit cell (a collection of a single columnar structure and the corresponding substrate). Fig. 20B yes Fig. 20A Elevation and plan views of the unit cell shown in .

[0055] Fig. 20A and Fig. 20B The columnar structure shown in is a quadrangular prism (quadrangular prism) with a square bottom. Now assume that S0 is the area of ​​the substrate of the unit cell, S1 is the bottom area of ​​the columnar structure (the area occupied by the columnar structure on the substrate), and H is the height of the columnar structure. At this time, the filling rate F is (S1×H) / (S0×H). The area S0 and the bottom area S1 are w0×w0 and w1×w1, respectively. That is, in general, the filling rate is defined as the ratio of the volume of the columnar structure to the volume of the space of height H on the substrate of the unit cell. According to this definition, the filling rate can be calculated even if it is not necessarily a column. For example, for a Fig.21A and Fig.21B The cylindrical structure with a circular bottom surface as shown in Fig.22A and Fig. 22B The filling rate can also be calculated for the columnar structure whose base is a regular hexagon as shown in . Fig.21A and Fig.21B In the columnar structure shown in , the filling rate F is (S1×H) / (S0×H). The area S0 and the bottom area S1 are w0×w0 and (π×w1×w1) / 4, respectively. Fig.22A and Fig. 22B In the columnar structure shown in , the filling rate F is (S1×H) / (S0×H). The area S0 and the bottom area S1 are {3×(√3)×w0×w0} / 8 and {3×(√3)×w1×w1} / 8, respectively.

[0056] The columnar structures shown in Figures 20 to 22 are cylindrical columns having two similar and parallel plane figures on the top and bottom surfaces, but in practice, the two plane figures may not be completely similar, or the top and bottom surfaces may not be completely parallel. Even in such a case, the effective refractive index of the effective medium can be controlled from the viewpoint of the above-mentioned filling rate.

[0057] The substrate of the unit cell of FIGS. 20 to 22 actually exists as a single substrate when viewed from the entire metalens ML, and a columnar structure is provided on the substrate.

[0058] In FIGS. 20 to 22 , the center of the substrate and the center of the columnar structure in the unit cell substantially coincide with each other, but this example is not limited to this implementation.

[0059] The shape of the columnar structure is not limited to one of the shapes shown in Figures 20 to 22. For example, the shape of the columnar structure may be a prism with a polygonal bottom, a prism with a trapezoidal bottom, a prism with a convex bottom, a prism with a substantially regular polygonal bottom, a prism with an L-shaped bottom, etc.

[0060] Now we will give the phase function of the metalens surface MLS A description of the effect of at least one of a critical point and an inflection point is included.

[0061] In the phase function In the case of having a critical point, there is an effect of significantly changing the refractive power at the center and the refractive power at the periphery of the lens surface MLS or changing their signs. For example, as in Examples 1 and 4, in the case of using an aspherical lens on the front side of the optical system L0 or near the aperture stop SP, the refractive power of the aspherical lens increases and the size decreases, and spherical aberration and coma can be corrected. However, in this case, field curvature and astigmatism tend to fluctuate from the center to the periphery of the image (image surface). At this time, placing its phase function A metalens having a critical point can satisfactorily correct the relief aberration by utilizing the difference in refractive power between the center and the periphery.

[0062] In the phase function In the case of having an inflection point, there is an effect of making the refractive power of the periphery of the lens surface MLS smaller than the refractive power of the center. For example, as in Examples 2 and 3, by increasing the refractive power near the center of the lens surface MLS, the size of the lens can be reduced, the refractive power of the periphery is relatively reduced, and the light beams in the periphery are gently refracted relative to the light beams near the center. Thus, spherical aberration and coma can be effectively corrected.

[0063] Because the refractive power of the lens surface MLS can change significantly at the position where the on-axis beam and the off-axis beam separate in the radial direction, its phase function The metalens ML having a critical point and an inflection point disposed on the object side of the aperture stop SP can effectively correct the distortion.

[0064] As mentioned above, due to the phase function of the MLS on the metalens surface At least one of a critical point and an inflection point is included, so various aberrations of the optical system L0 can be satisfactorily corrected. An attempt to obtain the above effect using only an aspherical lens increases the thickness of the optical system L0 by the amount of the aspherical lens, but the use of the metalens ML minimizes the increase in thickness, so the reduced size of the optical system L0 can be maintained.

[0065] A description will now be given of a structure that may be satisfied in the optical system L0 according to each example.

[0066] The size of the columnar structure can be changed according to a predetermined rule in the radial direction of the lens surface MLS. Thus, an arbitrary phase change amount can be obtained at a position h in the radial direction. This example uses the filling rate as the size of the columnar structure, but is not limited to this implementation. As the size of the columnar structure, for example, the volume of the columnar structure, the diameter of the columnar structure, and the area occupied by the columnar structure on the lens surface MLS (the bottom area of ​​the columnar structure) can be used.

[0067] The sub-wavelength structure may include a structure in which a columnar structure is provided so that the size of the columnar structure increases or decreases as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS. Such a structure may be provided periodically along the radial direction of the lens surface MLS on at least a portion of the lens surface MLS. Thus, by repeating a phase change from 0 to 2π or from 0 to -2π in the radial direction of the element lens surface MLS, the phase function It can be changed continuously, and the metalens ML as a whole can be used as a lens.

[0068] In the case where a plurality of structures are provided along the radial direction of the lens surface MLS in at least a portion of the metalens surface MLS, the first structure and the second structure included in the plurality of structures may have different distances (intervals, periods) in the radial direction of the lens surface MLS. In at least a portion of the metalens surface MLS, the distance in the radial direction of the plurality of structures may decrease as the position moves away from the center, and then increase as the position moves away from the center. Now referring to Fig.23 , a description will be given of the effect of this change in such a structure.

[0069] Fig.23 is a phase function with an inflection point Schematic diagram of the metalens surface MLS. Fig.23 In the embodiment, the lens surface MLS includes a plurality of structures, wherein the filling rate of the columnar structure decreases as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS. The columnar structure is omitted in the middle, but Fig.19A and Fig.19B Similarly provided. D(i) is the distance in the radial direction of the lens surface MLS of the i-th structure (where i is a natural number) counted from the center of the lens surface among the plurality of structures. Fig.24 In the example, the distance D(i) is longer than the distance D(i+1), and the distance D(i+1) is shorter than the distance D(i+2). That is, in the i-th and (i+1)-th structures, the phase change from 0 to -2π in the (i+1)-th period occurs at a narrower distance than the phase change from 0 to -2π in the i-th period. At this time, the phase function The slope (absolute value) of is steep along the radial direction of the lens surface MLS. In the (i+1)th and (i+2)th structures, the phase change from 0 to -2π in the (i+2)th period occurs over a wider distance than the phase change from 0 to -2π in the (i+1)th period. At this time, the phase function The slope (absolute value) of is gentle along the radial direction of the lens surface MLS. Fig.23 In the phase function The slope (absolute value) of becomes gradually steeper along the radial direction of the lens surface MLS, and then gradually becomes gentler from the middle. That is, this means that the phase function has an inflection point, and due to the phase function Including the inflection point, an aberration correction effect can be obtained.

[0070] Although the columnar structure Fig.23 The columnar structure is provided so that the filling rate decreases as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS, but the columnar structure may be provided so that the filling rate increases.

[0071] In Example 1, Figure 3 and Figure 5 As shown in , the phase function of the metalens ML The filling rate corresponding to the actual columnar structure periodically repeats the change from a small value to a large value, and the distance in the radial direction per cycle narrows before and after the inflection point (from 0.0086 mm to 0.0084 mm) and then widens (0.0084 mm to 0.0086 mm). That is, the columnar structure is provided so that the phase function There are inflection points before and after this point. The phase function in Example 1 The inflection point is 1.0058 mm away from the optical axis in the radial direction.

[0072] In Example 2, Figure 8 and Fig. 9 As shown in , the phase function of the metalens ML The filling rate corresponding to the actual columnar structure periodically repeats the change from a large value to a small value, and the distance in the radial direction per cycle narrows before and after the inflection point (from 0.0250 mm to 0.0245 mm) and then widens (0.0245 mm to 0.0250 mm). That is, the columnar structure is provided so that the phase function There are inflection points before and after this point. The phase function in Example 2 The inflection point is 0.7135 mm away from the optical axis in the radial direction.

[0073] In Example 3, if Fig.12 and Fig.13 As shown in , the phase function of the metalens ML The filling rate corresponding to the actual columnar structure periodically repeats the change from a large value to a small value, and the distance in the radial direction per cycle narrows before and after the inflection point (from 0.0126 mm to 0.0124 mm) and then widens (0.0124 mm to 0.0126 mm). That is, the columnar structure is provided so that the phase function There are inflection points before and after this point. The phase function in Example 3 The inflection point is 0.7490 mm away from the optical axis in the radial direction.

[0074] In Example 4, Fig.16 and Fig.18 As shown in , the phase function of the metalens ML The filling rate corresponding to the actual columnar structure periodically repeats the change from a small value to a large value, and the distance in the radial direction per cycle narrows before and after the inflection point (from 0.0070 mm to 0.0069 mm) and then widens (0.0069 mm to 0.0070 mm). That is, the columnar structure is provided so that the phase function There are inflection points before and after this point. The phase function in Example 4 The inflection point is 0.9342 mm away from the optical axis in the radial direction.

[0075] In the case where a plurality of structures are provided in at least a portion of the meta-lens surface MLS along the radial direction of the lens surface MLS, the columnar structures in the first structure and the second structure included in the plurality of structures may have different sizes. For example, in the first structure, the columnar structure is provided so that the size of the columnar structure increases as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS. In the second structure, the columnar structure is provided so that the size of the columnar structure decreases as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS. At least a portion of the meta-lens surface MLS has a structure in which the first structure is periodically repeated in the radial direction of the lens surface MLS and a structure in which the second structure is periodically repeated. That is, the structure in which the first structure is periodically repeated and the structure in which the second structure is periodically repeated are switched at a predetermined position in the radial direction of the meta-lens surface MLS. Now referring to Fig.24 , a description will be given of the effects of the above structure.

[0076] Fig.24 is a phase function with a critical point Schematic diagram of the metalens surface MLS. Fig.24 , structures causing a phase change from 0 to 2π (or -2π) are repeatedly provided, and the i-th (where i is a natural number), (i+1)-th, (i+2)-th, and (i+3)-th structures are illustrated. The (i+1)-th structure ends before a phase change with a width of 2π occurs, and switches to the (i+2)-th structure. Up to the (i+1)-th structure, the columnar structure is provided so that its size decreases as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS. On the other hand, starting from the (i+2)-th structure, the columnar structure is provided so that its size increases as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS. Due to this structure, the phase function of the lens surface MLS The phase of decreases until the middle of the (i+1)th cycle (before switching to the (i+2)th cycle), and then increases after switching to the (i+2)th cycle. Fig.24 In the phase function The phase of decreases along the radial direction of the lens surface MLS and then increases from the middle. That is, this means that the phase function has a critical point, and due to the phase function Including critical points can obtain aberration correction effects.

[0077] exist Fig.24In the embodiment, the columnar structure changes so that its filling rate becomes smaller and then becomes larger as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS, but the example is not limited to this implementation. The columnar structure may change so that its filling rate becomes larger and then becomes smaller as the position moves away from the center of the lens surface MLS in the radial direction of the lens surface MLS. In this case, the phase function There is a critical point where it changes from increasing to decreasing.

[0078] In Example 1, Figure 3 and Figure 4 As shown in , the phase function of the metalens ML has a critical point. The filling rate corresponding to the actual columnar structure periodically repeats the change from a small value to a large value, and periodically repeats the change from a large value to a small value in the middle. That is, the columnar structure is provided so that the phase function There are critical points before and after this point. The phase function in Example 1 The critical point is 2.0417 mm away from the optical axis in the radial direction.

[0079] In Example 4, Fig.16 and Fig.17 As shown in , the phase function of the metalens ML has a critical point. The filling rate corresponding to the actual columnar structure periodically repeats the change from a small value to a large value, and periodically repeats the change from a large value to a small value in the middle. That is, the columnar structure is provided so that the phase function There are critical points before and after this point. The phase function in Example 4 The critical point is 1.8459 mm away from the optical axis in the radial direction.

[0080] The characteristic structure of the metalens ML and its aberration correction effect have been described above, but if the optical system L0 is composed of the metalens ML, the aberration correction effect is limited. Therefore, the aberration can be corrected by combining the metalens ML with an aspheric lens. The use of the metalens ML in combination with the aspheric lens can provide a synergistic effect on aberration correction. Therefore, the optical system L0 according to each example includes at least one aspheric lens. At least one of the lens surface on the object side of the aspheric lens and the lens surface on the image side of the aspheric lens is an aspheric surface, and the aspheric surface has at least one of an inflection point and a critical point.

[0081] In Examples 1 and 4, an aspherical lens having a large refractive power placed near the aperture stop SP is used to correct spherical aberration and coma, but as a result, field curvature tends to fluctuate. Therefore, the phase function A metalens ML with a critical point or inflection point deployed near the image plane can selectively correct field curvature.

[0082] In Examples 2 and 3, spherical aberration and coma are offset by an aspherical lens having a negative refractive power and a metalens ML having a positive refractive power. A sufficient aberration correction effect can be obtained by using a plurality of metalens ML, but in that case, a decrease in efficiency due to unnecessary diffracted light originating from a subwavelength structure and an influence on image quality due to glare cannot be ignored. Therefore, the metalens ML may be used in combination with an aspherical lens.

[0083] The columnar structure may be in the shape of a cylindrical column having two substantially similar and substantially parallel plane figures on the top and bottom surfaces. If the columnar structure is shaped like, for example, a cone or a pyramid, it becomes difficult to manufacture using a semiconductor manufacturing process such as photolithography.

[0084] A description will now be given of inequalities that the optical system L0 according to each example may satisfy. The optical system L0 according to each example may satisfy one or more of the following inequalities (1) to (12):

[0085] 0.050 <r / D<0.425 (1)

[0086] 0.1<|fM| / f<10.0 (2)

[0087] 0.1 <fP / f<10.0 (3)

[0088] -10.0 <fN / f<-0.1 (4)

[0089] 1.0 <H / λ<3.0 (5)

[0090] 0.3 <rmax / λ<0.9 (6)

[0091] 0.05 <rmin / λ<0.5 (7)

[0092] Here, r represents the phase function from the center of the lens surface MLS in the radial direction of the metalens surface MLS to the metalens surface MLS. The distance from the position on the lens surface MLS corresponding to at least one of the critical points and inflection points of the metalens surface MLS. D is the effective diameter of the metalens surface MLS (a distance twice as large as the distance from the optical axis to the light ray farthest from the optical axis in the radial direction among the light rays passing through the metalens surface MLS). f represents the focal length of the optical system L0. fM represents the focal length of the metalens ML. fP represents the focal length of at least one lens (positive lens) with positive refractive power included in the optical system L0. fN represents the focal length of at least one lens (negative lens) with negative refractive power included in the optical system L0. H represents the maximum height of the columnar structure (the length in the direction parallel to the optical axis direction). λ represents the design wavelength, which is, for example, the wavelength that maximizes the transmittance (i.e., the ratio of the intensity of the output light to the intensity of the incident light) of the light (substantially parallel light) incident on the metalens ML along the optical axis. rmax and rmin respectively represent the maximum diameter and the minimum diameter of the diameter of the columnar structure provided on the metalens surface MLS. In the case where the base of the columnar structure is substantially circular or substantially regular polygonal, the diameter of the columnar structure is the diameter of the circle circumscribing the shape of the base, and in the case where the base of the columnar structure is any other shape, it is the maximum length of the length of the line segment obtained by connecting any two points on the base.

[0093] Inequality (1) defines the phase function from the center of the lens surface MLS to the metalens surface MLS in the radial direction of the metalens surface MLS: The value of the ratio of the distance from the critical point or inflection point to the effective diameter of the metalens surface MLS. As described above, the metalens ML has the effect of significantly changing the refractive power between the vicinity of the optical axis and the periphery of the optical axis on the metalens surface MLS, and the effect of changing the sign of the refractive power. Therefore, the metalens ML deployed near the image plane away from the aperture stop SP can satisfactorily correct the field curvature and astigmatism from the center of the image (image plane) to the periphery of the image using the difference in refractive power between the center and the periphery. In addition, the metalens ML deployed near the aperture stop SP can satisfactorily correct spherical aberration and coma. In addition, the metalens ML deployed on the object side of the aperture stop SP can satisfactorily correct distortion. In the phase function from the center of the lens surface MLS to the metalens surface MLS In the case where the distance from the critical point or inflection point of the lens surface MLS becomes smaller and the value of r / D becomes lower than the lower limit of inequality (1), the change in refraction within the metalens surface MLS becomes too steep and the aberration correction effect becomes excessive. When the distance from the critical point or inflection point of the metalens surface MLS becomes larger and the value of r / D becomes higher than the upper limit of inequality (1), the position corresponding to the critical point or inflection point of the metalens surface MLS becomes too close to the periphery. In this case, the aberration correction effect using the difference in refractive power between the center and the periphery becomes limited.

[0094] Inequality (2) defines the value of the ratio of the focal length of the metalens ML to the focal length of the optical system L0. Generally, in order to correct or suppress aberrations, the refractive power of the optical system L0 can be shared by multiple lenses. Therefore, in order to correct aberrations using the metalens ML, the metalens ML can share a certain amount of the refractive power of the optical system L0. Thereby, the refractive power of lenses other than the metalens ML can be reduced, and the aberration correction effect can be appropriately obtained while suppressing aberrations. In the case where the absolute value of the focal length of the metalens ML becomes smaller and the value of |fM| / f becomes lower than the lower limit of the inequality (2), the refractive power of the metalens ML becomes too large and the aberration correction becomes excessive. In the case where the absolute value of the focal length of the metalens ML becomes larger and the value of |fM| / f becomes greater than the upper limit of the inequality (2), the effect of sharing the refractive power becomes smaller and the refractive power of other lenses becomes relatively larger. At this time, the aberrations generated become larger and the aberration correction effect of the metalens ML becomes smaller.

[0095] Inequality (3) defines the value of the ratio of the focal length of at least one lens with positive refractive power included in the optical system L0 to the focal length of the optical system L0. The combination of the lens with positive refractive power and the metalens ML can satisfactorily correct aberrations by sharing refractive power, suppressing aberrations, and canceling aberrations. In the case where the focal length of the lens with positive refractive power becomes shorter and the value of fP / f becomes lower than the lower limit of inequality (3), the refractive power of the lens with positive refractive power becomes too large, and spherical aberration and field curvature occur significantly in the undercorrected direction. In the case where the focal length of the lens with positive refractive power becomes longer and the value of fP / f becomes higher than the upper limit of inequality (3), the refractive power sharing effect and the aberration correction effect of the lens with positive refractive power are reduced.

[0096] Inequality (4) defines the value of the ratio of the focal length of at least one lens with negative refractive power included in the optical system L0 to the focal length of the optical system L0. The combination of the lens with negative refractive power and the metalens ML can satisfactorily correct aberrations by sharing refractive power, suppressing aberrations, and canceling aberrations. In the case where the focal length of the lens with negative refractive power becomes shorter and the value of fN / f becomes less than the lower limit of inequality (4), the refractive power of the lens with negative refractive power becomes too large, and spherical aberration and field curvature occur significantly in the over-correction direction. In the case where the focal length of the lens with negative refractive power becomes longer and the value of fN / f becomes higher than the upper limit of inequality (4), the refractive power sharing effect and the aberration correction effect of the lens with negative refractive power are reduced.

[0097] Inequality (5) defines the value of the ratio of the maximum height of the columnar structure to the design wavelength. Satisfying inequality (5) can provide an optical path length corresponding to the design wavelength or longer on the metalens surface MLS, and enables the metalens ML to achieve continuous desired phase changes by repetition of a periodic structure that produces a phase change from 0 to 2π as described above. In the case where the maximum height of the columnar structure decreases and the value of H / λ becomes lower than the lower limit of inequality (5), a phase change from 0 to 2π (width: 2π) cannot be produced, and the phase becomes discontinuous at the boundary of the periodic repetition, and the wavefront of the design wavelength is not continuously connected. In the case where the maximum height of the columnar structure becomes higher and the value of H / λ becomes higher than the upper limit of inequality (5), the maximum height of the columnar structure becomes too high and manufacturing becomes difficult.

[0098] Inequality (6) defines the value of the ratio of the maximum diameter among the diameters of the columnar structures provided on the metalens surface MLS to the design wavelength. Satisfying inequality (6) enables the metalens ML to behave as an average effective medium to light. In the case where the maximum diameter decreases and the value of rmax / λ becomes lower than the lower limit of inequality (6), the filling rate necessary to produce a phase change from 0 to 2π (width: 2π) cannot be obtained, and the wavefront of the design wavelength is not continuously connected. In the case where the maximum diameter increases and the value of rmax / λ becomes higher than the upper limit of inequality (6), the columnar structure becomes too large for light having the design wavelength, and unexpected diffraction light, glare, or reflected light may occur.

[0099] Inequality (7) defines the value of the ratio of the minimum diameter among the diameters of the columnar structures provided on the metalens surface MLS to the design wavelength. Satisfying inequality (7) enables the metalens ML to behave as an average effective medium to light. In the case where the minimum diameter decreases and the value of rmin / λ becomes lower than the lower limit of inequality (7), the columnar structure becomes too thin and manufacturing becomes difficult. In the case where the minimum diameter increases and the value of rmin / λ becomes higher than the upper limit of inequality (7), the filling rate necessary to produce a phase change from 0 to 2π (width: 2π) cannot be obtained, and the wavefront of the design wavelength is not continuously connected.

[0100] Inequalities (1) to (7) can be replaced by the following inequalities (1a) to (7a):

[0101] 0.085 <r / D<0.415 (1a)

[0102] 0.3<|fM| / f<9.0 (2a)

[0103] 0.15 <fP / f<9.70 (3a)

[0104] -9.5 <fN / f<-0.4 (4a)

[0105] 1.1 <H / λ<2.5 (5a)

[0106] 0.35 <rmax / λ<0.87 (6a)

[0107] 0.07 <rmin / λ<0.45 (7a)

[0108] Inequalities (1) to (7) can be replaced by the following inequalities (1b) to (7b):

[0109] 0.095 <r / D<0.405 (1b)

[0110] 0.6<|fM| / f<8.0 (2b)

[0111] 0.30 <fP / f<9.50 (3b)

[0112] -9.0 <fN / f<-0.7 (4b)

[0113] 1.15 <H / λ<2.20 (5b)

[0114] 0.40 <rmax / λ<0.85 (6b)

[0115] 0.09 <rmin / λ<0.40 (7b)

[0116] Inequalities (1) to (7) can be replaced by the following inequalities (1c) to (7c):

[0117] 0.110<2×r / D<0.395 (1c)

[0118] 0.8<|fM| / f<7.0 (2c)

[0119] 0.40 <fP / f<9.20 (3c)

[0120] -8.0 <fN / f<-1.0 (4c)

[0121] 1.2 <H / λ<2.0 (5c)

[0122] 0.45 <rmax / λ<0.83 (6c)

[0123] 0.14 <rmin / λ<0.35 (7c)

[0124] A detailed description will be given of the optical system L0 according to each example.

[0125] In Example 1, the optical system L0 includes, from the object side to the image side, first lens G1 to sixth lens G6 having positive, negative, positive, positive, negative, and negative refractive powers. In Example 1, the design wavelength is 940 nm. The metalens ML in Example 1 is the sixth lens G6, and the metalens surface MLS is a lens surface on the image side of the sixth lens G6. The metalens ML has negative refractive power near the optical axis. For the design wavelength, the refractive index of the columnar structure of the metalens surface MLS is 2.0164. Fig.21A and Fig.21B The cylindrical columnar structure (cylinder) shown in Fig.25 (disconnected) and Fig.26B (Broken line) is provided on the metalens surface MLS so as to produce while the diameter w1 of the circle changes Figure 3 The phase changes shown in . In Example 1, the length w0 of the substrate is 0.75 μm, the height H of the columnar structure is 1.45 μm, and the diameter w1 varies in the range of 0.200 μm to 0.685 μm.

[0126] In Example 2, the optical system L0 includes, from the object side to the image side, first lens G1 to sixth lens G6 having negative, positive, negative, positive, positive, and negative refractive powers. In Example 2, the design wavelength is 587.56 nm. The metalens ML in Example 2 is the fourth lens G4, and the metalens surface MLS is the lens surface on the object side of the fourth lens G4. The metalens ML has positive refractive power near the optical axis. For the design wavelength, the refractive index of the columnar structure of the metalens surface MLS is 2.0458. Fig. 20A and Fig. 20B The rectangular columnar structure (quadrangular prism or quadrangular prism) shown in Fig.25 (solid line) and Fig.26A (solid line) is provided on the metalens surface MLS so as to produce a Figure 8 In Example 2, the length w0 of the substrate is 0.40 μm, the height H of the columnar structure is 0.84 μm, and the side length w1 is varied in the range of 0.100 μm to 0.335 μm.

[0127] In Example 3, the optical system L0 includes first lens G1 to fourth lens G4 having positive, positive, negative, and negative refractive powers in order from the object side to the image side. In Example 3, the design wavelength is 940 nm. The metalens ML in Example 3 is the second lens G2, and the metalens surface MLS is the lens surface on the image side of the second lens G2. The metalens ML has positive refractive power near the optical axis. The refractive index of the columnar structure of the metalens surface MLS is 2.0164 for the design wavelength. Fig.22A and Fig. 22B The hexagonal columnar structure (hexagonal prism) shown in Fig.25 (solid line) and Fig.26C (Broken line) is provided on the metalens surface MLS so as to produce a Fig.12 In Example 3, the length w0 of the substrate is 0.75 μm, the height H of the columnar structure is 1.45 μm, and the side length w1 is varied in the range of 0.180 μm to 0.607 μm.

[0128] In Example 4, the optical system L0 includes, from the object side to the image side, first lens G1 to sixth lens G6 having positive, negative, positive, positive, negative, and negative refractive powers. In Example 4, the design wavelength is 587.56 nm. The metalens ML of Example 4 is the sixth lens G6, and the metalens surface MLS is a lens surface on the image side of the sixth lens G6. The metalens ML has negative refractive power near the optical axis. For the design wavelength, the refractive index of the columnar structure of the metalens surface MLS is 2.0458. Fig.21A and Fig.21B The cylindrical columnar structure (cylinder) shown in Fig.25 (disconnected) and Fig.26B (solid line) is provided on the metalens surface MLS so as to produce while changing the diameter w1 of the circle Fig.16 The phase changes shown in . In Example 4, the length w0 of the substrate is 0.40 μm, the height H of the columnar structure is 0.84 μm, and the diameter w1 varies from 0.180 μm to 0.367 μm.

[0129] Numerical Examples 1 to 4 corresponding to Examples 1 to 4 will be described below.

[0130] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axis distance (distance on the optical axis) between the mth surface and the (m+1)th surface, where m is the surface number counted from the light incident side. nd represents the refractive index of each optical member for the d line, and νd represents the Abbe number of the optical member. n940 is the refractive index of each optical member for a wavelength of 940 nm. The Abbe number of a certain material is expressed as follows:

[0131] vd=(Nd-1) / (NF-NC)

[0132] Here, Nd, NF and NC are the refractive indices of the d line (587.6 nm), the F line (486.1 nm) and the C line (656.3 nm) among the Fraunhofer lines.

[0133] In each numerical example, d, focal length (mm), F number, and half angle of view (°) are all values ​​when the optical system L0 is in a state of focusing on an object at infinity. The back focal length BF is the distance on the optical axis from the last lens surface (lens surface closest to the image plane) of the optical system L0 to the (paraxial) image plane expressed in air equivalent length. The total lens length is the length obtained by adding the back focal length to the distance on the optical axis from the frontmost lens surface (lens surface closest to the object) to the last lens surface (which does not include the optical block FL).

[0134] An asterisk "*" appended to the right of the surface number means that the optical surface is aspherical. The aspherical shape is expressed as follows:

[0135] X=(h 2 / R) / [1+{1-(1+K)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12

[0136] Where X is the displacement from the surface vertex in the direction of the optical axis, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, K is the cone constant, and A4, A6, A8, A10, and A12 are the aspheric coefficients of each order. The “e±XX” in each aspheric coefficient means “×10 ±XX ”.

[0137] MLS indicates that the surface is a metalens surface. Where B2, B4, B6, B8, B10 and B12 are coefficients of each order, and the phase function of the metalens surface is is expressed as a power series polynomial:

[0138]

[0139] Where Φ is the optical path difference function of the metalens surface, λ is the design wavelength, and C2, C4, C6, C8, C10, and C12 are coefficients of each order. The optical path difference function Φ is expressed as a power series polynomial:

[0140]

[0141]

[0142] At this time, where fM is the focal length of the metalens surface, the following equation is established:

[0143] 1 / fM=-2×C2=-2×λ×B2 / (2Π)

[0144] The “e±XX” in each coefficient means “×10± XX ”.

[0145] Numerical Example 1

[0146] Unit: mm

[0147] Surface data

[0148]

[0149] Aspheric surface data

[0150] Surface 1

[0151] K=0.00000e+00 A4=8.31829e-02 A 6=-6.80816e-03 A8=4.96011e-05

[0152] Surface 2

[0153] K=-7.83575e+00 A4=1.39114e-01 A6=-2.53752e-02A8=1.68533e-02

[0154] Surface 3

[0155] K=-4.53662e+00A4=1.33684e-01 A6=-4.83426e-02 A8=1.34721e-02

[0156] Surface 4

[0157] K=-3.57529e+00 A4=1.07508e-01 A6=-2.00095e-02A 8=-4.70803e-02

[0158] Surface 6

[0159] K=1.00000e+-01 A4=9.41213e-03 A6=6.12387e-02 A8=-1.55783e-01 A10=-2.77809e-03

[0160] Surface 7

[0161] K=-1.86654e+01 A4=1.49386e-01 A6=1.09103e-01 A8=-8.78459e-02 A10=8.49814e-03

[0162] Surface 8

[0163] K=0.00000e+00 A4=7.25912e-02 A6=5.61224e-02 A8=-2.60104e-02

[0164] Surface 9

[0165] K=0.00000e+00 A4=-3.42408e-02A 6=1.36192e-02 A8=-2.08664e-02

[0166] Surface 10

[0167] K=0.00000e+00 A4=-1.22987e-01 A6=2.69464e-02 A8=4.87787e-03 A10=-3.34934e-03

[0168] Surface 11

[0169] K=0.00000e+00 A4=-1.24895e-01 A6=3.36893e-02 A8=-5.67529e-03

[0170] 13th Surface (MLS)

[0171] C2=8.55017e-02 C4=-1.73660e-02 C6=1.38018e-03 C8=4.37175e-05

[0172]

[0173] Single lens data

[0174]

[0175] Numerical Example 2

[0176] Unit: mm

[0177] Surface data

[0178]

[0179]

[0180] Aspheric surface data

[0181] Surface 1

[0182] K=0.00000e+00 A4=-1.91087e-02 A6=1.37174e-03 A8=3.95640e-04

[0183] Surface 2

[0184] K=-3.18548e+00 A4=-2.03665e-02 A6=9.72944e-03 A8=1.63619e-02

[0185] Surface 3

[0186] K=-4.74707e+00 A4=4.76470e-02 A6=-6.23112e-02 A8=6.19068e-03 A10=-1.74582e-02

[0187] Surface 4

[0188] K=1.00000e+01 A4=-9.55121e-02 A 6=7.92232e-02 A8=-4.93316e-02 A10=2.73523e-02

[0189] Surface 6

[0190] K=9.96250e+00 A4=-1.14053e-01 A6=1.84047e-01 A8=-3.60989e-02 A10=6.22275e-03

[0191] Surface 7

[0192] K=1.99999e+01 A4=-7.25652e-02 A6=1.37502e-01 A8=-5.40950e-02 A10=2.59535e-02

[0193] 8th surface (MLS)

[0194] C2=-2.50984e-02 C4=8.41972e-03 C6=5.93566e-04 C8=-7.84988e-04C10=-1.55749e-04

[0195] Surface 10

[0196] K=0.00000 e +00 A4=-9.20501e-02 A6=1.21058e-02 A8=-2.32952e-03

[0197] Surface 11

[0198] K=0.00000e+00 A4=-8.08606e-02 A6=9.29348e-03 A8=-1.34130e-03

[0199] Surface 12

[0200] K=-1.00000e+01A4=-6.35885e-02 A6=-1.18290e-02 A8=2.86576e-03

[0201] Surface 13

[0202] K=-4.66528e+00 A4=-3.78185e-02 A6=2.45314e-03 A8=-9.86812e-05

[0203]

[0204] Single lens data

[0205] Numerical example 3 Unit: mm Surface data

[0206]

[0207] Aspheric surface data

[0208] Surface 1

[0209] K=0.00000e+00 A4=-8.51198e-03 A6=-1.87386e-03 A8=-8.21259e-03

[0210] Surface 2

[0211] K=0.00000e+00 A4=-8.82492e-03 A6=-1.39205e-02 A8=-1.00226e-02

[0212] 5th surface (MLS)

[0213] C2=-6.42581e-02 C4=5.80317e-03 C6=8.18128e-03 C8=-3.64839e-03C10=5.41249e-03

[0214] Surface 6

[0215] K=0.00000e+00 A4=-1.32164e-02 A6=3.81982e-03

[0216] Surface 7

[0217] K=0.00000e+00 A4=-1.66429e-02 A6=1.04823e-02 A8=-1.22743e-03 Surface 8

[0218] K=0.00000e+00 A4=-7.50759e-02 A6=4.47157e-03 A8=7.75616e-04 A10=-7.39618e-05

[0219] Surface 9

[0220] K=0.00000e+00 A4=-6.50080e-02 A6=6.71184e-03 A8=-4.14732e-04

[0221]

[0222] Single lens data

[0223]

[0224] Numerical Example 4

[0225] Unit: mm

[0226] Surface data

[0227]

[0228]

[0229] Aspheric surface data

[0230] Surface 1

[0231] K=0.00000e+00 A4=7.76296e-02 A6=-5.96239e-03

[0232] Surface 2

[0233] K=0.00000e+00 A4=1.58973e-01 A6=-2.43158e-02 A8=1.36084e-02

[0234] Surface 3

[0235] K=-3.59362e+00 A4=8.65247e-02 A6=-2.20609e-02 A8=7.58096e-03

[0236] Surface 4

[0237] K=-3.07327e+00 A4=8.03389e-02 A6=-1.81655e-02 A8=-2.75557e-02

[0238] Surface 6

[0239] K=0.0000e+00 A4=2.52416e-02 A6=-1.56320e-03 A8=-7.66220e-02

[0240] Surface 7

[0241] K=0.00000e+00 A4=1.48521e-01

[0242] Surface 8

[0243] K=0.00000e+00 A4=8.55980e-02 A6=-4.07608e-03 A8=4.28876e-03

[0244] Surface 9

[0245] K=0.00000e+00 A4=-1.84767e-02 A6=3.70582e-03 A8=-5.13414e-03

[0246] Surface 10

[0247] K=0.00000e+00 A4=-1.10959e-01 A6=2.08304e-02 A8=7.15666e-03A10=-3.97014e-03

[0248] Surface 11

[0249] K=0.00000e+00 A4=-1.21890e-01 A6=3.34359e-02 A8=-6.00247e-03

[0250] 13th Surface (MLS)

[0251] C2=7.06468e-02 C4=-1.63034e-02 C6=1.36101e-03 C8=-4.39037e-05

[0252]

[0253] Single lens data

[0254]

[0255] Table 1 below summarizes the various values ​​of the inequality in each example.

[0256] Table 1

[0257]

[0258] Image pickup device

[0259] Reference now Fig. 27 , a description will be given of a digital still camera (image pickup device) using the optical system L0 according to any one of Examples 1 to 4 as an imaging optical system. Fig. 27 , reference numeral 10 denotes a camera body, and reference numeral 11 denotes an imaging optical system including the optical system L0 according to any one of Examples 1 to 4. Reference numeral 12 denotes an image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor, which is built into the camera body 10, receives an optical image formed by the imaging optical system 11, and performs photoelectric conversion on it. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror. The quality of an output image can be improved by electrically correcting various aberrations such as distortion and chromatic aberration in an image acquired by the image sensor 12.

[0260] Applying the optical system L0 according to each example to an image pickup apparatus such as a digital still camera can provide an image pickup apparatus having a small lens.

[0261] Lens device

[0262] Fig.28 : is a schematic external view of a lens apparatus 20 using the optical system L0 according to any one of Examples 1 to 4 as an imaging optical system. The lens apparatus 20 is a so-called interchangeable lens that is attachable to and detachable from a camera body not shown. Reference numeral 21 denotes an imaging optical system including the optical system L0 according to any one of Examples 1 to 4. The imaging optical system 21 is held by a holder not shown. The lens apparatus 20 includes a focus operation unit 22 and an operation unit 23 configured to change an imaging mode.

[0263] When the user operates the focus operation unit 22 , the arrangement of the imaging optical system 21 may be changed mechanically or electrically, and the focal position may be changed.

[0264] The arrangement of the lens units in the imaging optical system 21 may be changed for purposes other than focusing by the user operating the operation unit 23. For example, the aberration of the imaging optical system 21 may be changed by mechanically or electrically changing the arrangement of the lens units in the imaging optical system 21 according to the operation of the operation unit 23. At this time, the focal position may not be substantially changed.

[0265] Each example can provide an optical system that is compact and can satisfactorily correct various aberrations from the center of the image to the periphery of the image.

[0266] Although the disclosure has described example embodiments, it is to be understood that some embodiments are not limited to the disclosed embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An optical system, include: at least one lens; as well as a metalens having a lens surface that produces a phase change in the wavefront of light passing through the metalens, It is characterized in that the phase function of the lens surface includes an inflection point, and the phase function of the lens surface represents the phase change amount of the wavefront corresponding to the position in the radial direction of the metalens.

2. The optical system according to claim 1, Features The following inequalities are satisfied: 0.050<r / D<0.425 Wherein r is the distance from the center of the lens surface in the radial direction of the metalens to the position in the radial direction of the metalens corresponding to the inflection point included in the phase function, and D is the effective diameter of the lens surface.

3. The optical system according to claim 1, Features The lens surface includes a structure having a plurality of convex portions, The size of each protrusion changes in the radial direction according to a predetermined rule.

4. The optical system according to claim 3, Features The size of the convex portion of the optical system is determined by at least one of a filling rate of the convex portion, a volume of the convex portion, a diameter of the convex portion, and an area of ​​the convex portion on the lens surface.

5. The optical system according to claim 3, Features In the structure, the convex portions are provided such that the size of each convex portion increases or decreases as the position moves away from the center of the lens surface in the radial direction.

6. The optical system according to claim 5, Features The structures are provided periodically along the radial direction.

7. The optical system according to claim 3, Features The lens surface includes a plurality of structures, in each of which a convex portion is provided such that a size of each convex portion increases or decreases as a position moves away from a center of the lens surface in the radial direction, and wherein the plurality of structures comprises a first structure and a second structure, and The distance of the first structure in the radial direction is different from the distance of the second structure in the radial direction.

8. The optical system according to claim 7, Features In at least a portion of the lens surface, a distance of the plurality of structures in the radial direction becomes shorter as a position moves away from the center, and then becomes longer as the position moves away from the center.

9. The optical system according to claim 3, Features The lens surface includes a plurality of structures, in each of which a convex portion is provided such that a size of each convex portion increases or decreases as a position moves away from a center of the lens surface in the radial direction, wherein the plurality of structures comprises a first structure and a second structure, and The change in size of the first structure in the radial direction is different from the change in size of the second structure in the radial direction.

10. The optical system according to claim 9, Features On at least a portion of the lens surface, the first structure is periodically repeated in the radial direction, and the second structure is periodically repeated in the radial direction.

11. The optical system according to claim 3, Features Each of the protrusions has a columnar shape having two substantially similar and substantially parallel planar figures on a top surface and a bottom surface.

12. The optical system according to claim 1, Features The following inequalities are satisfied: 0.1<|fM| / f<10.0 Where f is the focal length of the optical system and fM is the focal length of the metalens.

13. The optical system according to claim 1, Features The at least one lens includes at least one positive lens, and the following inequality is satisfied: 0.1 <fP / f<10.0 Wherein f is the focal length of the optical system, and fP is the focal length of the positive lens.

14. The optical system according to claim 1, Features The at least one lens includes at least one negative lens, and the following inequality is satisfied: -10.0<fN / f<-0.1 Wherein f is the focal length of the optical system, and fN is the focal length of the negative lens.

15. The optical system according to claim 3, Features The following inequalities are satisfied: 1.0<H / λ<3.0 Wherein H is the maximum height among the heights of the convex portions in the direction along the optical axis, and λ is the design wavelength.

16. The optical system according to claim 3, Features the following The inequality is satisfied: 0.3 <rmax / λ<0.9 0.05 <rmin / λ<0.50 wherein rmax and rmin are the maximum diameter and the minimum diameter of the plurality of convex portions, respectively, and λ is the design wavelength.

17. The optical system according to claim 1, Features The at least one lens comprises at least one aspherical lens, The aspherical lens has an aspherical surface including an inflection point.

18. An optical system, include: at least one lens; as well as a metalens having a lens surface that produces a phase change in the wavefront of light passing through the metalens, It is characterized in that the lens surface includes a structure having a plurality of convex portions, The size of each convex portion changes in the radial direction according to a predetermined rule.

19. An optical system, include: at least one lens; as well as a metalens having a lens surface that produces a phase change in the wavefront of light passing through the metalens, It is characterized in that the phase function of the lens surface includes a critical point in the peripheral portion in the radial direction of the metalens, and the phase function of the lens surface represents the phase change amount of the wavefront corresponding to the position in the radial direction.

20. An optical element, include: a lens surface that produces a phase change in the wavefront of light passing through the optical element, It is characterized in that the phase function of the lens surface includes an inflection point, and the phase function of the lens surface represents the phase change amount of the wavefront corresponding to the position in the radial direction of the metalens.

21. An image pickup device, include: An optical system according to any one of claims 1 to 19; as well as An image sensor is configured to receive an image formed by the optical system.

22. A lens device, include: An optical system according to any one of claims 1 to 19; as well as A holder is configured to hold the optical system.

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