Optical system and image capturing device

Abstract

To achieve both compactness and high optical performance using a diffraction surface with a controlled wavelength dispersion property.SOLUTION: An optical system L is provided, comprising a diffractive optical element L1 with positive refractive power having a convex refractive surface on the object side and a diffraction surface with a controlled wavelength dispersion property on the image side, and a lens L2 with negative refractive power arranged in order from the object side to the image side. The diffraction surface has an Abbe number ν0 that satisfies a condition expressed as: -0.2<1 / ν0<0.2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical system suitable for an imaging device such as a digital camera. [Background technology]

[0002] As an optical system for a small camera mounted on a smartphone, Patent Document 1 discloses a telephoto type optical system in which the entire system is composed of six lenses, and a first lens with a strong positive refractive power is arranged closest to the object. Patent Document 2 discloses an optical system composed of a first lens with a positive refractive power that is convex toward the object side and arranged closest to the object side, and a second lens having negative chromatic aberration including a metasurface lens. Patent Document 3 discloses an optical system in which a first lens with a strong positive refractive power is arranged closest to the object side, and at least one surface of a diffractive optical element is provided with an uncontrolled wavelength dispersion characteristic, and the focal length, overall length, and focal length of the diffractive optical element of the entire optical system are set to be suitable for miniaturization.

[0003] In these optical systems, the first lens with a strong positive refractive power is located closest to the object. This configuration is effective in shortening the overall length of the optical system, but since the first lens generates large chromatic aberration and monochromatic aberration, various aberrations such as chromatic aberration are corrected by arranging multiple lenses, including aspherical lenses with negative refractive power. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 10,989,901 [Patent Document 2] U.S. Patent Publication No. 2021 / 0132256 [Patent Document 3] International Patent Publication No. WO2021 / 170417 Summary of the Invention [Problem to be solved by the invention]

[0005] When arranging a strong positive refractive power in the first lens and shortening the overall length and correcting aberrations with a small number of lenses, it is effective to use a diffractive surface with a negative Abbe number mainly to correct chromatic aberration. However, since the Abbe number of a normal diffractive surface whose wavelength dispersion characteristics are not simply controlled is very high dispersion, when the diffractive surface is given a refractive power (the reciprocal of the focal length), large chromatic aberration occurs. For this reason, it is difficult to achieve both compactness of the optical system by reducing the number of lenses and high image quality at the same time.

[0006] The present invention provides an optical system that uses a diffractive surface with controlled wavelength dispersion characteristics to achieve both compactness and high optical performance. [Means for solving the problem]

[0007] An optical system according to one aspect of the present invention includes a diffractive optical element (or metalens) with positive refractive power, which has a convex refractive surface on the object side and a diffractive surface (or metasurface) with controlled wavelength dispersion characteristics on the image side, and a lens with negative refractive power, which are arranged in this order from the object side to the image side. When the Abbe number of the diffractive surface (or metasurface) is ν0, -0.2<1 / ν0<0.2 The optical system according to the present invention is characterized in that it satisfies the following conditions: Note that an image pickup apparatus having the above optical system also constitutes another aspect of the present invention. Effect of the Invention

[0008] According to the present invention, by using a diffractive surface with controlled wavelength dispersion characteristics, it is possible to achieve both a compact optical system and high optical performance. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view of the optical system of the first embodiment. [Diagram 2] 4A to 4C are aberration diagrams of the optical system of Example 1. [Diagram 3] FIG. 11 is a cross-sectional view of an optical system according to a second embodiment. [Figure 4] 6A to 6C are aberration diagrams of the optical system of Example 2. [Diagram 5] FIG. 11 is a cross-sectional view of the optical system of the third embodiment. [Figure 6] 11A to 11C are aberration diagrams of the optical system of Example 3. [Figure 7] FIG. 11 is a cross-sectional view of an optical system according to a fourth embodiment. [Figure 8] 11A to 11C are aberration diagrams of the optical system of Example 4. [Figure 9] FIG. 13 is a cross-sectional view of the optical system of the fifth embodiment. [Figure 10] 13A to 13C are aberration diagrams of the optical system of Example 5. [Figure 11] FIG. 1 is a diagram showing an imaging apparatus using an optical system according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, before describing specific embodiments 1 to 5, matters common to each embodiment will be described. FIG. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 respectively show the configuration of the optical system L of the embodiments 1 to 5. O indicates the optical axis of the optical system L. MOE indicates a diffractive optical element including a diffractive surface with controlled wavelength dispersion characteristics (hereinafter simply referred to as dispersion controlled). L1 indicates the first lens, L2 indicates the second lens, and L3 indicates the third lens group. SP indicates an aperture stop, and GB indicates a glass block including an infrared cut filter, a low-pass filter, and the like. IP indicates the image plane of the optical system L. On the image plane IP, an imaging surface (light receiving surface) of an imaging element such as a CCD sensor or a CMOS sensor, or a film surface (photosensitive surface) of a silver halide film is arranged.

[0011] 2, 4, 6, 8, and 10 respectively show longitudinal aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical systems of Numerical Examples 1 to 5 corresponding to Examples 1 to 5 when focused on an object at infinity (hereinafter referred to as an infinity focused state). The vertical axis Fno of the spherical aberration diagram indicates the F-number, and the vertical axis ω of the astigmatism, distortion, and chromatic aberration indicates the half angle of view (°). The horizontal axis indicates the amount of each aberration.

[0012] In the spherical aberration diagram, the solid line indicates the spherical aberration for the d-line (wavelength 587.6 nm), and the two-dot chain line indicates the spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S indicates the astigmatism on the sagittal image plane, and the dashed line M indicates the astigmatism on the meridional image plane. The distortion diagram shows the distortion aberration at the d-line. The chromatic aberration diagram shows the lateral chromatic aberration at the g-line.

[0013] Next, the features of the optical system of each embodiment, which is small in size and has high optical performance, and is composed of a small number of lenses, will be described.

[0014] The optical system of each embodiment has, arranged in order from the object side to the image side, a diffractive optical element with positive refractive power having a convex refracting surface on the object side and a dispersion-controlled diffractive surface on the image side, and a lens with negative refractive power. Note that a lens or other optical element may be arranged on the object side of the diffractive optical element. When the Abbe number of the diffractive surface is ν0, the following formula (1) is satisfied.

[0015] -0.2<1 / ν0<0.2 (1) Here, the Abbe number ν0 of the dispersion-controlled diffractive surface is defined by the following formula. d =0.58756μm), main dispersion is F line (λ F =0.48613μm) and C line (λ C = 0.65627 μm, and the optical path difference function at each wavelength is ψ(λ d ), ψ(λ F ), ψ(λ C ) and the optical path difference dispersion of the surface at each wavelength is P(λ d ), P(λ F ), P(λ C ) In this case,

[0016]

number

[0017] As described above, the optical system of each embodiment includes a diffractive optical element with positive refractive power having a convex refractive surface on the object side and a dispersion-controlled diffractive surface on the image side. The convergence effect of light rays due to the positive refractive power makes it easy to miniaturize the optical system. In addition, the inclusion of a dispersion-controlled diffractive surface makes it easy to effectively correct chromatic aberration and obtain high optical performance with a small number of lenses.

[0018] The optical system of each embodiment also includes a second lens having a negative refractive power, which makes it easy to obtain high optical performance by correcting various aberrations, mainly monochromatic aberrations, generated by a diffractive optical element having a positive refractive power.

[0019] The condition of formula (1) is a condition for effectively correcting chromatic aberration with a dispersion-controlled diffractive surface and obtaining high optical performance with a small number of lenses. If the negative Abbe number becomes too high dispersion so that 1 / ν0 is below the lower limit of formula (1), the chromatic aberration generated by the dispersion-controlled diffractive surface becomes too large, making it difficult to increase the refractive power of the diffractive surface and reduce the size of the optical system, which is not preferable. It also becomes difficult to correct chromatic aberration and obtain high optical performance, which is not preferable. If the positive Abbe number becomes too high dispersion so that 1 / ν0 is above the upper limit of formula (1), the chromatic aberration generated by the dispersion-controlled diffractive surface becomes too large, making it difficult to increase the refractive power of the diffractive surface and reduce the size of the optical system, which is not preferable. It also becomes difficult to correct chromatic aberration and obtain high optical performance, which is not preferable.

[0020] It is more preferable to set the numerical range of formula (1) as follows:

[0021] -0.10<1 / ν0<0.02 (1a) It is more preferable that the numerical range of formula (1) is as follows:

[0022] -0.100<1 / ν0<0.011 (1b) It is preferable that the optical system of each embodiment satisfies at least one of the conditions of the following expressions (2) to (8).

[0023] When the focal length of a diffractive optical element with positive refractive power is f1 and the focal length of the entire optical system is f, it is preferable to set the focal length f1 of the diffractive optical element so as to satisfy the condition of the following formula (2).

[0024] 0.3 <f1 / f<0.8 (2) The condition of formula (2) is a condition for facilitating the achievement of an optical system that is compact and has high optical performance. If f1 / f is below the lower limit of formula (2), the focal length of the diffractive optical element becomes too short, making it difficult to achieve high optical performance, which is undesirable. If f1 / f is above the upper limit of formula (2), the focal length of the diffractive optical element becomes too long, making it difficult to miniaturize the optical system, which is undesirable.

[0025] It is more preferable to set the numerical range of the formula (2) as follows:

[0026] 0.4 <f1 / f<0.7 (2a) It is more preferable that the numerical range of the formula (2) is as follows:

[0027] 0.45 <f1 / f<0.65 (2b) When the focal length of the dispersion-controlled diffractive surface is fmoe and the focal length of the entire optical system is f, it is preferable to set the focal length fmoe of the diffractive surface so as to satisfy the condition of the following equation (3).

[0028] 2.5 <fmoe / f<10.0 (3) The focal length fmoe of a dispersion-controlled diffractive surface is calculated by the following formula, where U2 is the quadratic coefficient of the optical path difference function of the surface at the design wavelength.

[0029]

number

[0030] The condition of formula (3) is also a condition for facilitating the achievement of an optical system that is compact and has high optical performance. If fmoe / f falls below the lower limit of formula (3), the focal length of the dispersion-controlled diffractive surface becomes too short, causing large aberrations such as spherical aberration, which makes it difficult to achieve high optical performance, which is undesirable. If fmoe / f exceeds the upper limit of formula (3), the focal length of the dispersion-controlled diffractive surface becomes too long, making it difficult to miniaturize the optical system, which is undesirable.

[0031] It is more preferable to set the numerical range of the formula (3) as follows:

[0032] 3.0 <fmoe / f<9.7 (3a) It is more preferable that the numerical range of the formula (3) is as follows:

[0033] 4.0 <fmoe / f<9.4 (3b) When the distance on the optical axis from the lens surface closest to the object to the image plane (hereinafter referred to as the total lens length) is TL, it is preferable to set the total lens length so as to satisfy the condition of the following formula (4).

[0034] 0.6 <TL / f<0.9 (4) The condition of formula (4) is also a condition for facilitating the achievement of an optical system that is compact and has high optical performance. If TL / f is below the lower limit of formula (4), the total lens length becomes too short, causing large aberrations such as spherical aberration, which makes it difficult to achieve high optical performance, which is undesirable. If TL / f is above the upper limit of formula (4), the total lens length becomes too long, making it difficult to miniaturize the optical system, which is undesirable.

[0035] It is more preferable to set the numerical range of the formula (4) as follows:

[0036] 0.70 <TL / f<0.88 (4a) It is more preferable that the numerical range of the formula (4) is as follows:

[0037] 0.75 <TL / f<0.86 (4b) In the optical system of each embodiment, it is preferable to arrange, in order from the object side to the image side, a first optical element (hereinafter referred to as the first diffractive optical element) as a diffractive optical element with positive refractive power described above, and a second optical element (hereinafter referred to as the second lens) as a lens with negative refractive power described above. As described above, the first diffractive optical element is a diffractive optical element with positive refractive power having a convex refracting surface on the object side and a dispersion-controlled diffractive surface on the image side. With this arrangement, the first diffractive optical element can effectively converge light rays while appropriately correcting various aberrations such as chromatic aberration. Furthermore, the second lens with negative refractive power makes it easy to obtain high optical performance by correcting various aberrations, mainly monochromatic aberrations, generated by the diffractive optical element with positive refractive power.

[0038] When the air gap on the optical axis between the first diffractive optical element having positive refractive power and the second lens having negative refractive power is defined as D12, it is preferable to set the air gap D12 so as to satisfy the condition of the following formula (5).

[0039] 0.08 <D12 / TL<0.40 (5) The condition of formula (5) is also a condition for facilitating the achievement of a compact optical system with high optical performance. If the air gap D12 is too short so that D12 / TL is below the lower limit of formula (5), it becomes difficult to sufficiently converge the on-axis marginal ray by the first diffractive optical element and make it enter the second lens. As a result, it becomes difficult to obtain high optical performance by correcting various aberrations such as spherical aberration and coma aberration by giving the second lens a strong negative refractive power, which is undesirable. If the air gap D12 is too long so that D12 / TL exceeds the upper limit of formula (5), it becomes difficult to miniaturize the optical system, which is undesirable.

[0040] It is more preferable to set the numerical range of the formula (5) as follows:

[0041] 0.10 <D12 / TL<0.30 (5a) It is more preferable that the numerical range of the formula (5) is as follows:

[0042] 0.11 <D12 / TL<0.25 (5b) When the air distance on the optical axis between the second lens having negative refractive power and a third optical element (hereinafter referred to as the third lens) serving as a lens adjacent to the second lens on the image side is denoted as D23, it is preferable to set the air distance D23 so as to satisfy the condition of the following equation (6).

[0043] 0.15 <D23 / TL<0.50 (6) The condition of formula (6) is also a condition for facilitating the achievement of an optical system that is compact and has high optical performance. If the air gap D23 becomes too short so that D23 / TL falls below the lower limit of formula (6), it becomes difficult to sufficiently separate the off-axis light beams incident on the third lens. As a result, it becomes difficult to effectively use the aspheric surface of the third lens to correct aberrations, and it becomes difficult to achieve high optical performance, which is undesirable. If the air gap D23 becomes too long so that D23 / TL exceeds the upper limit of formula (6), it becomes difficult to miniaturize the optical system, which is undesirable.

[0044] It is more preferable to set the numerical range of the formula (6) as follows:

[0045] 0.18 <D23 / TL<0.40 (6a) It is more preferable that the numerical range of the formula (6) is as follows:

[0046] 0.20 <D23 / TL<0.35 (6b) When the distance on the optical axis from the lens surface closest to the object side of the optical system to the lens surface of the second lens closest to the object side is L02, it is preferable to set the distance L02 so as to satisfy the condition of the following formula (7).

[0047] 0.20 <L02 / TL<0.45 (7) The condition of formula (7) is a condition for facilitating the attainment of an optical system having high optical performance. If the distance L2 is too short so that L02 / TL is below the lower limit of formula (7), the second lens becomes too close to the first lens. As a result, it becomes difficult to make the entire optical system have a concentric shape with the second lens at the center, and it becomes difficult to correct various aberrations such as curvature of field and distortion, which is not preferable. If the distance L2 is too long so that L02 / TL exceeds the upper limit of formula (7), the second lens becomes too close to the lens on the image side. As a result, it becomes difficult to make the entire optical system have a concentric shape with the second lens at the center, and it becomes difficult to correct various aberrations such as curvature of field and distortion, which is not preferable.

[0048] It is more preferable to set the numerical range of the formula (7) as follows:

[0049] 0.24 <L02 / TL<0.40 (7a) It is more preferable that the numerical range of the formula (7) is as follows:

[0050] 0.26 <L02 / TL<0.36 (7b) When the focal length of a third lens having negative refractive power adjacent to the second lens having negative refractive power on the image side is fG3, it is preferable to set the focal length fG3 of the third lens so as to satisfy the condition of the following equation (8).

[0051] -1.5 <fG3 / f<-0.4 (8) The condition of formula (8) is also a condition for facilitating the achievement of a compact optical system with high optical performance. If the focal length fG3 is too long so that fG3 / f is below the lower limit of formula (8), the effect of changing the light direction of the third lens becomes too weak, making it difficult for the third lens to effectively correct various aberrations such as curvature of field and distortion, which is not preferable. If the focal length fG3 is too short so that fG3 / f is above the upper limit of formula (8), the divergence effect of the third lens becomes too strong, making it difficult to shorten the overall length of the optical system, which is not preferable.

[0052] It is more preferable to set the numerical range of the formula (8) as follows:

[0053] -1.0 <fG3 / f<-0.5 (8a) It is more preferable that the numerical range of the formula (8) is as follows:

[0054] -0.70 <fG3 / f<-0.55 (8b) The optical system of the embodiment is preferably composed of, arranged in order from the object side to the image side, a first diffractive optical element with positive refractive power, a second lens with negative refractive power, a third lens which is a double-sided aspherical lens, and a fourth optical element (fourth lens) which is a double-sided aspherical lens.

[0055] By arranging a positive first diffractive optical element and a negative second lens in that order from the object side, it is possible to effectively converge light rays with the first diffractive optical element while appropriately correcting various aberrations such as chromatic aberration. In addition, by arranging the negative second lens next to the positive first diffractive optical element, it becomes easy to obtain high optical performance by correcting various aberrations, mainly monochromatic aberration, generated by the first diffractive optical element. Furthermore, by arranging a double-sided aspherical third lens and a double-sided aspherical fourth lens, it becomes easy to obtain high optical performance with a small number of lenses, that is, four.

[0056] Hereinafter, a specific description will be given of the optical system L of Examples 1 to 5. After Example 5, Numerical Examples 1 to 5 corresponding to Examples 1 to 5, respectively, are shown.

[0057] In each numerical example, surface number i indicates the order of the surface when counted from the object side. r indicates the paraxial radius of curvature (mm) of the i-th optical surface (i-th surface), and d indicates the axial distance (lens thickness or air distance) (mm) along the optical axis between the i-th surface and the (i+1)-th surface. In addition, nd and νd respectively indicate the refractive index at the d-line of the material of the i-th optical member and the Abbe number based on the d-line.

[0058] The Abbe number νd based on the d-line is expressed as νd=(Nd-1) / (NF-NC) where Nd, NF, and NC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines. The effective diameter indicates the radius (mm) of the area through which light rays that contribute to image formation pass on the i-th surface.

[0059] BF stands for back focus (mm). Back focus is the distance on the optical axis from the final surface of the zoom lens (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. The total lens length is the distance on the optical axis from the foreground surface of the zoom lens (the lens surface closest to the object) to the final surface plus the back focus, and corresponds to TL in equations (4) to (7).

[0060] An "*" next to a surface number means that the surface has an aspheric shape. An aspheric shape is expressed by the following formula, where x is the displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, k is the conic constant, and A4 to A10 are aspheric coefficients. Note that the conic constant and the aspheric coefficients "e±M" are expressed as x10 ±M means...

[0061] 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 Moreover, the optical path difference function of the surface at the design wavelength is expressed by the following formula, where U2 to U10 are the optical path difference function coefficients of the surface.

[0062] ψ0=U2 h 2 +U4·h 4 +U6·h 6 +U8·h 8 +U10·h 10 The (diffraction) affixed to the surface number means that the surface is optically designed according to the optical path difference function of the surface.

[0063] The values ​​of Numerical Examples 1 to 5 relating to the above-mentioned formulas (1) to (8) are shown in Table 1. EXAMPLES

[0064] 1 is an optical system having a focal length of 6.79 mm, an F-number of 2.7, and a half angle of view of 21.83°. The optical system L is composed of a first diffractive optical element L1 with positive refractive power, an aperture stop SP, a second lens L2 with negative refractive power, and a third lens group L3, arranged in this order from the object side to the image side.

[0065] The first diffractive optical element L1 is a diffractive optical element having a convex refractive surface on the object side and a dispersion-controlled diffractive surface on the image side. The second lens L2 is a double-sided aspheric lens with a biconcave paraxial lens surface. The third lens group L3 is composed of a third lens having negative refractive power and a biconcave paraxial radius of curvature on both sides, and a fourth lens having positive refractive power and a meniscus shape with a convex paraxial radius of curvature on the image side, arranged in order from the object side to the image side. EXAMPLES

[0066] 3 is an optical system having a focal length of 5.53 mm, an F-number of 2.5, and a half angle of view of 26.2°. The optical system L is composed of a first diffractive optical element L1 with positive refractive power, an aperture stop SP, a second lens L2 with negative refractive power, and a third lens group L3.

[0067] The first diffractive optical element L1 is a diffractive optical element having a convex refractive surface on the object side and a dispersion-controlled diffractive surface on the image side. The second lens L2 is a double-sided aspheric lens with a biconcave paraxial radius of curvature. The third lens group L3 is composed of a third lens having negative refractive power and a biconcave paraxial radius of curvature on both sides, and a fourth lens having negative refractive power and a meniscus shape with a convex paraxial radius of curvature on the image side, arranged in order from the object side to the image side. EXAMPLES

[0068] 5 is an optical system having a focal length of 8.70 mm, an F-number of 2.9, and a half angle of view of 17.36°. The optical system L is composed of, arranged in order from the object side to the image side, a first diffractive optical element L1 having a positive refractive power, an aperture stop SP, a second lens L2 having a negative refractive power, and a third lens group L3.

[0069] The first diffractive optical element L1 is a diffractive optical element having a convex refractive surface on the object side and a dispersion-controlled diffractive surface on the image side. The second lens L2 is a double-sided aspheric lens with a biconcave paraxial radius of curvature. The third lens group L3 is composed of a third lens having negative refractive power and a biconcave paraxial radius of curvature on both sides, and a fourth lens having positive refractive power and a meniscus shape with a convex paraxial radius of curvature on the image side, arranged in order from the object side to the image side. EXAMPLES

[0070] 7 is an optical system having a focal length of 8.58 mm, an F-number of 2.9, and a half angle of view of 17.59°. The optical system L is composed of a first diffractive optical element L1 with positive refractive power, an aperture stop SP, a second lens L2 with negative refractive power, and a third lens group L3, arranged in this order from the object side to the image side.

[0071] As in the first embodiment, the first diffractive optical element L1 is a diffractive optical element having a convex refracting surface on the object side and a dispersion-controlled diffractive surface on the image side. The second lens L2 is a double-sided aspheric lens with a biconcave paraxial radius of curvature. The third lens group L3 is composed of a third lens having negative refractive power and a biconcave paraxial radius of curvature on both sides, and a fourth lens having positive refractive power and a meniscus shape with a convex paraxial radius of curvature on the image side, arranged in order from the object side to the image side. EXAMPLES

[0072] 9 is an optical system having a focal length of 6.79 mm, an F-number of 2.7, and a half angle of view of 21.83°. The optical system L is composed of a first diffractive optical element L1 with positive refractive power, an aperture stop SP, a second lens L2 with negative refractive power, and a third lens group L3, arranged in this order from the object side to the image side.

[0073] As in the first embodiment, the first diffractive optical element L1 is a diffractive optical element having a convex refracting surface on the object side and a dispersion-controlled diffractive surface on the image side. The second lens L2 is a double-sided aspheric lens with a biconcave paraxial radius of curvature. The third lens group L3 is composed of a third lens having negative refractive power and a biconcave paraxial radius of curvature on both sides, and a fourth lens having positive refractive power and a meniscus shape with a convex paraxial radius of curvature on the image side, arranged in order from the object side to the image side.

[0074] In addition, in imaging using the optical system L of each embodiment, aberration correction may be performed by image processing. Furthermore, the optical path difference function of the diffractive optical element may be realized by a metalens having a so-called single-layer metasurface, in which the metasurface is made of one layer, or a so-called stacked metasurface, in which the metasurface is made of multiple layers. [Numerical example 1] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1* 1.684 0.81 1.43875 94.9 2.51 2(return) ∞ 0.83 2.37 3 (twist) ∞ 0.10 1.74 4* -9.488 0.30 1.59946 25.8 1.63 5* 7.691 1.82 1.39 6* -2.930 0.40 1.53504 55.7 2.56 7* 12.835 0.12 3.25 8* -1.910 0.74 1.64025 19.3 3.75 9* -1.431 0.03 4.11 10 ∞ 0.21 1.51633 64.1 5.50 11 ∞ 0.40 5.50 Image plane∞ Aspheric surface Page 1 K =-8.37714e-01 A 4= 9.67558e-03 A 6=-6.23630e-04 A 8= 2.13482e-03 A10=-8.44847e-04 Side 2 (folded side) Design wavelength 0.58756 [μm] U 2=-9.76396e-03 U 4= 1.46160e-03 U 6= 1.78901e-03 U 8=-1.02999e-03 U 10 = 1.12524e-04 Surface optical path difference dispersion P(λ) = 12.24651 λ 10 - 119.47404 λ 9 + 698.9340 λ 8 - 2720.50548 · λ 7 + 7400.16189 λ 6 - 14357.25933 · λ 5 + 19873.45822 · λ 4 - 19240.96797 · λ 3 + 19240.96797 λ 2-4807.97026 · λ + 847.47010 P(λ d ) = 1.000000e+00 P(λ C ) = 9.061342e-01 P(λ F ) = 1.194911e+00 Page 4 K =-7.30312e+02 A 4= 1.11548e-01 A 6= 2.68473e-01 A 8=-1.02096e+00 A10= 2.20808e+00 A12=-2.77979e+00 A14= 1.80491e+00 A16=-4.29895e-01 Page 5 K = 9.50000e+01 A 4= 2.50245e-01 A 6=-9.99304e-02 A 8= 1.82022e-01 A10=-2.06303e-01 Page 6 K = 3.71573e+00 A 4=-3.10316e-01 A 6=-1.39954e-01 A 8= 1.08852e+00 A10=-1.59622e+00 A12= 1.13582e+00 A14=-4.07725e-01 A16= 6.09779e-02 Page 7 K = 5.66804e+01 A 4=-3.59989e-01 A 6= 2.81360e-01 A 8=-1.32968e-01 A10= 3.00410e-02 A12=-3.03550e-03 A14= 1.94204e-04 Page 8 K =-7.61381e+00 A 4= 2.25923e-02 A 6=-1.53447e-02 A 8= 1.29023e-03 A10= 1.54000e-03 A12=-3.07319e-04 Page 9 K =-3.68987e+00 A 4=-2.79819e-03 A 6=-1.52162e-03 A 8=-3.47584e-03 A10=2.02821e-03 A12=-2.65856e-04 Various data Focal length 6.79 F-number 2.70 Half angle of view(°) 21.83 Image height 2.72 Lens length 5.69 BF 0.57 Entrance pupil position 2.21 Exit pupil position -5.42 Front principal point position 1.08 Back principal point position -6.39 Single lens data Lens starting surface focal length 1 1 3.61 2 4 -7.04 3 6 -4.42 4 8 5.55 [Numerical example 2] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1* 1.386 0.77 1.43875 94.9 2.21 2(diffraction) ∞ 0.57 2.06 3 (Aperture) ∞ 0.11 1.60 4* -10.233 0.30 1.60586 24.5 1.48 5* 11.746 1.17 1.25 6* -2.121 0.40 1.53504 55.7 2.08 7* 12.818 0.09 2.88 8* -2.090 0.61 1.63085 20.4 3.65 9* -2.454 0.03 4.06 10 ∞ 0.21 1.51633 64.1 5.50 11 ∞ 0.40 5.50 Image plane∞ Aspheric surface Page 1 K =-9.18376e-01 A 4= 1.89471e-02 A 6= 1.09143e-03 A 8= 1.87832e-03 A10=-2.95422e-03 Side 2 (folded side) Design wavelength 0.58756 [μm] U 2=-1.00142e-02 U 4= 7.40658e-03 U 6=-1.02452e-02 U 8= 7.55762e-03 U10=-2.62698e-03 Surface optical path difference dispersion P(λ) = 13.87546 λ 10 - 153.95668 λ 9 + 1009.95630 λ 8 - 4356.52716 λ 7 + 13006.44877 λ 6 - 27470.79737 · λ 5 + 41106.88437 λ 4 - 42762.08537 · λ 3 + 29486.82651 λ 2 - 12144.39247·λ + 2266.41068 P(λ d ) = 1.000000e+00 P(λ C ) = 9.155559e-01 P(λ F ) = 1.184181e+00 Page 4 K =-2.71665e+02 A 4= 2.02763e-01 A 6=-7.20641e-02 A 8= 8.04897e-01 A10=-3.05427e+00 A12= 5.29501e+00 A14=-4.14210e+00 A16= 1.19528e+00 5th page K = 4.89253e-01 A 4= 2.25750e-01 A 6= 6.27068e-01 A 8=-1.60141e+00 A10 = 1.82728e+00 Side 6 K = 2.66010e+00 A 4=-3.37434e-01 A 6=-2.07792e-01 A 8= 1.03514e+00 A10=-1.74754e+00 A12= 1.26306e+00 A14=-1.36633e-01 A16=-8.95322e-02 Side 7 K = 2.89242e+01 A 4=-3.42912e-01 A 6= 1.98866e-01 A 8=-9.07270e-02 A10= 7.20873e-03 A12= 8.78904e-03 A14=-1.68521e-03 Side 8 K =-5.53855e+00 A 4= 5.40644e-03 A 6= 7.17144e-03 A 8=-6.11534e-04 A10=3.80971e-04 A12=-1.54203e-04 9th page K =-1.10259e+01 A 4=-7.33408e-02 A 6= 2.34943e-02 A 8=-1.14536e-03 A10= 1.23043e-04 A12=-8.25915e-05 Various data Focal length 5.53 F-number 2.50 Half angle of view (°) 26.20 Image height 2.72 Lens length 4.59 BF 0.57 Entrance pupil position 1.73 Exit pupil position -2.19 Front principal point position -4.53 Back principal point position -5.13 Single lens data Lens starting surface focal length 1 1 3.00 2 4 -8.98 3 6 -3.37 4 8 -64.19 [Numerical example 3] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1* 2.226 0.83 1.43875 94.9 3.00 2(Diffraction) ∞ 1.43 2.87 3 (Aperture) ∞ 0.10 1.86 4* -9.383 0.30 1.58172 30.3 1.77 5* 7.917 2.01 1.56 6* -8.482 0.40 1.53504 55.7 2.53 7* 5.062 0.15 3.12 8* -3.299 1.00 1.63648 19.7 3.52 9* -2.221 0.51 4.19 10 ∞ 0.21 1.51633 64.1 5.50 11 ∞ 0.40 5.50 Image plane ∞ Aspheric Data Front page K = 3.28784e-01 A 4=-1.12717e-02 A 6=-1.16474e-03 A 8=-5.88116e-04 A10=-7.58421e-05 Surface 2 (diffractive surface) Design wavelength 0.58756 [μm] U2 = -1.24211e-02 U4 = -9.93242e-04 U6 = 1.10002e-03 U8 = -5.79917e-04 U10 = 1.48671e-04 Optical path difference dispersion of the surface P(λ) = 11.97801·λ 10 - 113.77083·λ 9 + 647.33574·λ 8 - 2448.35587·λ 7 + 6465.34198·λ 6 - 12165.39383·λ 5 + 16315.44261·λ 4 - 15288.88750·λ 3 + 9538.09656·λ 2 - 3567.44539·λ + 606.61668 P(λ d ) = 1.000000e+00 P(λ C ) = 9.046900e-01 P(λ F ) = 1.196528e+00 The fourth surface K = -7.12739e+02 A4 = 1.93928e-02 A6 = 3.10222e-01 A8 = -9.88060e-01 A10 = 2.03483e+00 A12 = -2.53536e+00 A14 = 1.71781e+00 A16 = -4.81247e-01 The fifth surface K = 7.49263e+01 A4 = 1.33691e-01 A6 = -4.90895e-02 A8 = 7.52699e-02 A10 = -6.37695e-02 The sixth surface K = 4.03729e+01 A4 = -2.72142e-01 A6 = -1.27746e-01 A8 = 8.56983e-01 A10=-1.36860e+00 A12= 1.08218e+00 A14=-4.25757e-01 A16= 6.72854e-02 Side 7 K = 8.34119e+00 A 4=-3.52878e-01 A 6= 2.40338e-01 A 8=-1.18592e-01 A10= 2.59296e-02 A12= 1.55307e-03 A14=-1.08217e-03 Side 8 K = 2.04857e+00 A 4= 3.67846e-02 A 6= 4.39495e-03 A 8=-1.50198e-03 A10= 2.19341e-04 A12= 1.74466e-05 9th page K =-8.24113e-02 A 4= 3.88049e-02 A 6= 2.10572e-03 A 8=-1.59372e-03 A10=3.89306e-04 A12=-3.30176e-05 Various data Focal length 8.70 F-number 2.90 Half angle of view (°) 17.36 Image height 2.72 Lens length 7.27 BF 1.05 Entrance pupil position 3.46 Exit pupil position -5.58 Front principal point position -0.50 Back principal point position -8.30 Single lens data Lens starting surface focal length 1 1 4.56 2 4 -7.33 3 6 -5.86 4 8 7.85 [Numerical example 4] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1* 2.246 0.81 1.43875 94.9 2.96 2(Diffraction) -295.185 1.41 2.83 3 (Aperture) ∞ 0.10 1.87 4* -17.662 0.30 1.56422 36.5 1.77 5* 6.188 1.99 1.56 6* -6.412 0.40 1.53504 55.7 2.52 7* 5.517 0.33 3.11 8* -4.293 1.00 1.61957 22.1 3.65 9* -2.411 0.28 4.28 10 ∞ 0.21 1.51633 64.1 5.50 11 ∞ 0.40 5.50 Image plane ∞ Aspheric Data Front page K = 2.78962e-01 A 4=-9.97081e-03 A 6=-1.16477e-03 A 8=-6.47121e-04 A10=-2.00577e-07 Surface 2 (diffractive surface) K = 2.28097e+04 Design wavelength 0.58756 [μm] U 2=-1.21838e-02 U 4= 1.63050e-04 U 6= 2.16299e-04 U 8=-1.70898e-04 U10 = 7.75164e-05 Surface optical path difference dispersion P(λ) = -434.73044 λ 10 + 8122.08910·λ 9 - 67394.74965 λ 8 + 329209.06586·λ 7- 1049750.44998 · λ 6 + 2284260.64803 · λ 5 - 3435917.19850·λ 4 + 3528102.09277 · λ 3 - 2367044.44179 · λ 2 +937029.43952·λ - 166209.30017 P(λ d ) = 1.000000e+00 P(λ C ) = 9.218523e-01 P(λ F ) = 1.177345e+00 Page 4 K =-3.94370e+03 A 4= 3.63831e-02 A 6= 3.04246e-01 A 8=-1.00699e+00 A10= 2.05779e+00 A12=-2.51896e+00 A14= 1.67922e+00 A16=-4.64464e-01 Page 5 K = 4.21306e+01 A 4= 1.19464e-01 A 6=-1.17085e-02 A 8= 4.56339e-03 A10=-1.28123e-02 Page 6 K = 2.25807e+01 A 4=-2.40989e-01 A 6=-1.20292e-01 A 8= 8.48864e-01 A10=-1.36495e+00 A12= 1.07826e+00 A14=-4.25456e-01 A16= 6.78933e-02 Page 7 K = 1.01704e+01 A 4=-3.33795e-01 A 6= 2.36754e-01 A 8=-1.18145e-01 A10= 2.50599e-02 A12= 1.71424e-03 A14=-1.05420e-03 Page 8 K = 3.74014e+00 A 4=-3.44508e-03 A 6= 1.14067e-02 A 8=-2.17872e-03 A10=4.85615e-04 A12=-5.30278e-05 9th page K = 3.93746e-02 A 4= 2.66395e-02 A 6=-1.24811e-03 A 8= 1.05063e-04 A10= 1.52986e-04 A12=-2.06204e-05 Various data Focal length 8.58 F-number 2.90 Half angle of view(°) 17.59 Image height 2.72 Lens length 7.15 BF 0.81 Entrance pupil position 3.34 Exit pupil position -5.71 Front principal point position -0.13 Back principal point position -8.18 Single lens data Lens starting surface focal length 1 1 4.61 2 4 -8.09 3 6 -5.48 4 8 7.37 [Numerical example 5] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1* 1.679 0.81 1.43875 94.9 2.51 2(Diffraction) -1201.658 0.80 2.37 3 (Aperture) ∞ 0.10 1.76 4* -9.679 0.30 1.60444 24.8 1.65 5* 7.743 1.84 1.40 6* -2.952 0.40 1.53504 55.7 2.57 7* 11.054 0.11 3.28 8* -1.909 0.75 1.64475 19.1 3.74 9* -1.431 0.03 4.10 10 ∞ 0.21 1.51633 64.1 5.50 11 ∞ 0.40 5.50 Image plane∞ Aspheric surface Page 1 K =-8.31081e-01 A 4= 9.86364e-03 A 6=-4.96299e-04 A 8= 2.14642e-03 A10=-8.10108e-04 Side 2 (folded side) K = 8.39004e+05 Design wavelength 0.58756 [μm] U 2=-9.57924e-03 U 4= 1.96827e-03 U 6= 1.84008e-03 U 8=-1.04244e-03 U10 = 1.26614e-04 Surface optical path difference dispersion P(λ) = 0.58756 / λ P(λ d ) = 1.000000e+00 P(λ C ) = 8.953022e-01 P(λ F ) = 1.208648e+00 Page 4 K =-7.78980e+02 A 4= 1.13646e-01 A 6= 2.67771e-01 A 8=-1.02350e+00 A10= 2.21155e+00 A12=-2.77374e+00 A14= 1.79686e+00 A16=-4.32428e-01 5th page K = 9.50000e+01 A 4= 2.51941e-01 A 6=-1.04642e-01 A 8= 1.91332e-01 A10=-2.07083e-01 Side 6 K = 3.75305e+00 A 4=-3.17027e-01 A 6=-1.36568e-01 A 8= 1.09289e+00 A10=-1.59737e+00 A12= 1.13434e+00 A14=-4.07143e-01 A16= 6.08155e-02 Side 7 K = 4.07551e+01 A 4=-3.64478e-01 A 6= 2.85375e-01 A 8=-1.33950e-01 A10= 3.01960e-02 A12=-2.92272e-03 A14= 1.40925e-04 Side 8 K =-8.37675e+00 A 4= 2.02048e-02 A 6=-1.49159e-02 A 8= 1.26993e-03 A10= 1.53299e-03 A12=-3.05658e-04 9th page K =-3.76863e+00 A 4=-2.11771e-03 A 6=-2.28008e-03 A 8=-3.46988e-03 A10=2.07880e-03 A12=-2.72202e-04 Various data Focal length 6.79 F-number 2.70 Half angle of view(°) 21.83 Image height 2.72 Lens length 5.69 BF 0.57 Entrance pupil position 2.16 Exit pupil position -5.42 Front principal point position 1.02 Back principal point position -6.39 Single lens data Lens starting surface focal length 1 1 3.60 2 4 -7.07 3 6 -4.31 4 8 5.50

[0075] [Table 1]

[0076] [Imaging device] 11 shows a digital still camera as an imaging device using the optical system of each of the above-mentioned embodiments as an imaging optical system. Reference numeral 20 denotes a camera body, and 21 denotes an imaging optical system constituted by any of the optical systems of embodiments 1 to 3. Reference numeral 22 denotes an imaging element such as a CCD sensor or a CMOS sensor that is built into the camera body 20 and captures an optical image (subject image) formed by the imaging optical system 21. Reference numeral 23 denotes a recording unit that records image data generated by processing an imaging signal from the imaging element 22, and 24 denotes a rear display that displays the image data.

[0077] By using the optical system of each embodiment, a small-sized camera having high optical performance can be obtained. The camera may be a single-lens reflex camera having a quick-turn mirror, or a mirrorless camera having no quick-turn mirror.

[0078] The above embodiment includes the following configurations.

[0079] (Configuration 1) Arranged in order from the object side to the image side, a diffractive optical element having a positive refractive power and a convex refractive surface on the object side and a diffractive surface on the image side whose wavelength dispersion characteristics are controlled; and a lens having a negative refractive power, The Abbe number of the diffractive surface is ν0, the reference wavelength is d-line, the primary dispersion is F-line and C-line, and the optical path difference function at each wavelength is ψ(λd ), ψ(λ F ), ψ(λ C ), and the optical path difference dispersion of the surface at each wavelength is P(λ d ), P(λ F ), P(λ C ) as

[0080]

number

[0081] When -0.2<1 / ν0<0.2 An optical system characterized by satisfying the following conditions. (Configuration 2) When the focal length of the diffractive optical element is f1 and the focal length of the optical system is f, 0.3 <f1 / f<0.8 2. The optical system according to claim 1, wherein the following condition is satisfied: (Configuration 3) The focal length of the diffractive surface is fmoe, the focal length of the optical system is f, and the quadratic coefficient of the optical path difference function of the surface at the design wavelength is U2.

[0082]

number

[0083] When 2.5 <fmoe / f<10.0 3. The optical system according to configuration 1 or 2, which satisfies the following condition: (Configuration 4) Let TL be the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane, and f be the focal length of the optical system. 0.6 <TL / f<0.9 4. The optical system according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) 5. The optical system described in any one of configurations 1 to 4, characterized in that a first optical element as the diffractive optical element and a second optical element as the lens are arranged in this order from the most object side to the most image side in the optical system. (Configuration 6) When an air gap on the optical axis between the first optical element and the second optical element is D12, and a distance on the optical axis from the lens surface closest to the object side of the optical system to an image plane is TL, 0.08 <D12 / TL<0.40 6. The optical system according to configuration 5, wherein the following condition is satisfied: (Configuration 7) a third optical element as a lens adjacent to the second optical element on an image side, When the air gap on the optical axis between the second optical element and the third optical element is D23, and the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane is TL, 0.15 <D23 / TL<0.50 7. The optical system according to configuration 5 or 6, which satisfies the following condition: (Configuration 8) Let L02 be the distance on the optical axis from the lens surface closest to the object of the optical system to the lens surface of the second optical element closest to the object, and TL be the distance on the optical axis from the lens surface closest to the object of the optical system to an image plane. 0.20 <L02 / TL<0.45 8. The optical system according to any one of configurations 5 to 7, wherein the following condition is satisfied: (Configuration 9) a third optical element serving as a lens having negative refractive power adjacent to the second optical element on an image side, When the focal length of the third optical element is fG3 and the focal length of the optical system is f, -1.5 <fG3 / f<-0.4 9. The optical system according to any one of configurations 5 to 8, wherein the following condition is satisfied: (Configuration 10) are arranged in the optical system in order from the most object side to the most image side. a first optical element as the diffractive optical element; and A second optical element as the lens; a third optical element as a double aspheric lens; and 10. The optical system according to any one of configurations 1 to 9, characterized in that it is configured with a fourth optical element which is a double-sided aspherical lens. (Configuration 11) the third optical element has a negative refractive power, 11. The optical system according to configuration 10, wherein the fourth optical element has a positive or negative refractive power. (Configuration 12) Arranged in order from the object side to the image side, a metalens with positive refractive power having a convex refractive surface on the object side and a metasurface with controlled wavelength dispersion characteristics on the image side; and a lens having a negative refractive power, The Abbe number of the metasurface is ν0, the reference wavelength is the d-line, the primary dispersion is the F-line and the C-line, and the optical path difference function at each wavelength is ψ(λ d ), ψ(λ F ), ψ(λ C ), and the optical path difference dispersion of the surface at each wavelength is P(λ d ), P(λ F ), P(λ C ) as

[0084]

number

[0085] When -0.2<1 / ν0<0.2 An optical system characterized by satisfying the following conditions. (Configuration 13) An optical system according to any one of configurations 1 to 12; and an image sensor for capturing an image of a subject through the optical system.

[0086] The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0087] L optical system MOE Diffractive Optical Element L1 First diffractive optical element L2 Second lens L3: Third lens group SP aperture stop IP image plane

Claims

1. Arranged in order from the object side to the image side, a diffractive optical element having a positive refractive power and a convex refractive surface on the object side and a diffractive surface on the image side whose wavelength dispersion characteristics are controlled; and a lens having a negative refractive power, The Abbe number of the diffractive surface is ν ０ The reference wavelength is the d-line, the primary dispersion is the F-line and the C-line, and the optical path difference function at each wavelength is ψ(λ ｄ ), ψ(λ Ｆ ), ψ(λ Ｃ ), and the optical path difference dispersion of the surface at each wavelength is P(λ ｄ ), P(λ Ｆ ), P(λ Ｃ ) as [0010] When -0.2<1 / n ０ <0.2 An optical system characterized by satisfying the following conditions.

2. When the focal length of the diffractive optical element is f1 and the focal length of the optical system is f, 0.3<f1 / f<0.8 2. The optical system according to claim 1, which satisfies the following condition:

3. The focal length of the diffractive surface is fmoe, the focal length of the optical system is f, and the quadratic coefficient of the optical path difference function of the surface at the design wavelength is U ２ As, [0025] When 2.5<fmoe / f<10.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

4. Let TL be the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane, and f be the focal length of the optical system. 0.6<TL / f<0.9 2. The optical system according to claim 1, which satisfies the following condition:

5. 2. The optical system according to claim 1, further comprising, in order from the object side to the image side in the optical system, a first optical element as the diffractive optical element and a second optical element as the lens.

6. When an air gap on the optical axis between the first optical element and the second optical element is D12, and a distance on the optical axis from a lens surface closest to the object side of the optical system to an image plane is TL, 0.08<D12 / TL<0.40 6. The optical system according to claim 5, which satisfies the following condition:

7. a third optical element as a lens adjacent to the second optical element on an image side, When an air gap on the optical axis between the second optical element and the third optical element is D23, and a distance on the optical axis from a lens surface closest to the object side of the optical system to an image plane is TL, 0.15<D23 / TL<0.50 6. The optical system according to claim 5, which satisfies the following condition:

8. Let L02 be the distance on the optical axis from the lens surface closest to the object side of the optical system to the lens surface closest to the object side of the second optical element, and let TL be the distance on the optical axis from the lens surface closest to the object side of the optical system to an image plane. 0.20<L02 / TL<0.45 6. The optical system according to claim 5, which satisfies the following condition:

9. a third optical element as a lens having negative refractive power adjacent to the second optical element on an image side, When the focal length of the third lens is fG3 and the focal length of the optical system is f, -1.5<fG3 / f<-0.4 6. The optical system according to claim 5, which satisfies the following condition:

10. are arranged in the optical system in order from the most object side to the most image side. a first optical element as the diffractive optical element; A second optical element as the lens; a third optical element as a double aspheric lens; and 2. The optical system according to claim 1, further comprising a fourth optical element which is a double-sided aspherical lens.

11. the third optical element has a negative refractive power, The optical system according to claim 10 , wherein the fourth optical element has a positive or negative refractive power.

12. Arranged in order from the object side to the image side, a metalens with positive refractive power having a convex refractive surface on the object side and a metasurface with controlled wavelength dispersion characteristics on the image side; and a lens having a negative refractive power, The Abbe number of the metasurface is v ０ The reference wavelength is the d-line, the primary dispersion is the F-line and the C-line, and the optical path difference function at each wavelength is ψ(λ ｄ ), ψ(λ Ｆ ), ψ(λ Ｃ ), and the optical path difference dispersion of the surface at each wavelength is P(λ ｄ ), P(λ Ｆ ), P(λ Ｃ ) as [0030] When -0.2<1 / n ０ <0.2 An optical system characterized by satisfying the following conditions.

13. An optical system according to any one of claims 1 to 12; and an image sensor for capturing an image of a subject through the optical system.

Images