Imaging optical system and image pickup apparatus having same

Abstract

The invention discloses an imaging optical system and an image pickup apparatus having the same. An imaging optical system includes an imaging lens and an optical element disposed on an image side of the imaging lens. At least one surface of the optical element is a diffractive surface having controlled wavelength dispersion characteristics. A predetermined inequality is satisfied.

Description

Technical Field

[0001] An aspect of the embodiment relates to an imaging optical system and an image pickup apparatus having the imaging optical system. Background Art

[0002] Japanese PCT Domestic Publication No. 2022-542172 discloses an imaging system in which a nanostructured element is disposed on a substrate layer disposed at an arbitrary distance from an image sensor to focus the incident angle of a principal ray on the image sensor to almost zero degrees. Each of U.S. Patent Application Publications Nos. 2022 / 0082794 and 2022 / 0206186 discloses a configuration for performing dispersion control using a metasurface lens. Summary of the invention

[0003] An imaging optical system according to one aspect of the present disclosure includes an imaging lens and an optical element disposed on the image side of the imaging lens. At least one surface of the optical element is a diffractive surface with controlled wavelength dispersion characteristics. Wherein, ν0 is the Abbe number of the diffractive surface, the reference wavelength is the d-line, the main dispersion is the F-line and the C-line, ψ(λ d ),ψ(λ F ) and ψ(λ C ) are the optical path difference functions for d-line, F-line and C-line, respectively, P(λ d ), P(λ F ) and P(λ C ) are the optical path difference dispersions of the surface for d-line, F-line and C-line respectively, and the following equation is satisfied:

[0004] and

[0005] The following inequality is satisfied:

[0006] -1.5 <Tk / f1<0.2

[0007] -0.10<1 / ν0<0.02

[0008] Wherein, Tk is the exit pupil position of the imaging lens with a negative sign relative to the object side of the image plane as a reference, and f1 is the focal length of the optical element. An image pickup device having the above imaging optical system also constitutes another aspect of the present disclosure.

[0009] According to another aspect of the present disclosure, an imaging optical system includes an imaging lens and an optical element disposed on the image side of the imaging lens. At least one surface of the optical element is a metasurface having a controlled wavelength dispersion property. Wherein, ν0 is the Abbe number of the metasurface, the reference wavelength is the d-line, the main dispersion is the F-line and the C-line, ψ(λ d ),ψ(λ F) and ψ(λ C ) are the optical path difference functions for d-line, F-line and C-line, respectively, P(λ d ), P(λ F ) and P(λ C ) are the optical path difference dispersions of the surface for d-line, F-line and C-line respectively, and the following equation is satisfied:

[0010] and

[0011] The following inequality is satisfied:

[0012] -1.5 <Tk / f1<0.2

[0013] -0.10<1 / ν0<0.02

[0014] Wherein, Tk is the exit pupil position of the imaging lens by setting the object side to negative with respect to the image plane as a reference, and f1 is the focal length of the optical element including the metasurface. An image pickup device having the above imaging optical system also constitutes another aspect of the present disclosure.

[0015] Further features of the present disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional view of an imaging optical system according to Example 1.

[0017] Figure 2 is a longitudinal aberration diagram of the imaging optical system according to Example 1 in an infinity focused state.

[0018] Figure 3 is a cross-sectional view of an imaging optical system according to Example 2.

[0019] Figure 4 is a longitudinal aberration diagram of the imaging optical system according to Example 2 in an infinity focused state.

[0020] Figure 5 is a cross-sectional view of an imaging optical system according to Example 3.

[0021] Figure 6 is a longitudinal aberration diagram of the imaging optical system according to Example 3 in an infinity focused state.

[0022] Figure 7 An image pickup device having the imaging optical system according to any one of Examples 1 to 3 is illustrated. DETAILED DESCRIPTION

[0023] 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 designated with the same reference numerals, and their repeated description will be omitted.

[0024] Figure 1 , Figure 3 and Figure 5 They are respectively cross-sectional views of imaging optical systems according to Examples 1 to 3. The imaging optical system according to each example is an optical system used for an image pickup apparatus such as a digital video camera, a digital still camera, a broadcast camera, a film-based camera, and a surveillance camera.

[0025] In each cross-sectional view, the left side is the object side and the right side is the image side. The imaging optical system according to each example includes an imaging lens L and an optical element disposed on the image side of the imaging lens L. At least one surface of the optical element is a diffraction surface having a controlled wavelength dispersion characteristic. In the imaging optical system according to each example, an optical element MOE including a diffraction surface having a controlled wavelength dispersion characteristic is disposed.

[0026] In each cross-sectional view, O is the optical axis, and SP is the aperture stop (aperture). IP is an image plane. In the case where the imaging optical system according to each example is used as an imaging optical system of a digital still camera or a digital video camera, an imaging surface of a solid-state image sensor (photoelectric conversion element) IM such as a CCD sensor or a CMOS sensor is arranged on the image plane IP. In the case where the imaging optical system according to each example is used as an imaging optical system of a film-based camera, a photosensitive surface equivalent to a film plane is arranged on the image plane IP.

[0027] Figure 2 , Figure 4 and Figure 6 They are longitudinal aberration diagrams of the imaging optical systems according to Examples 1 to 3 in the infinity focus state, respectively. In the spherical aberration diagram, Fno is the F number. The spherical aberration diagram illustrates the spherical aberration amount for the d-line (wavelength 587.6nm) and the g-line (wavelength 435.8nm). In the astigmatism diagram, S represents the astigmatism amount on the sagittal image plane, and M represents the astigmatism amount on the meridional image plane. The distortion diagram illustrates the distortion amount for the d-line. The chromatic aberration diagram illustrates the chromatic aberration amount for the g-line. ω is the half angle of view (°).

[0028] Now, a description will be given of the characteristic configuration of the imaging optical system according to each example.

[0029] When reducing the size of the imaging optical system, especially in the case of a wide-angle lens, reducing the total length brings the imaging exit pupil closer to the image plane, and the incident angle on the image sensor becomes larger. Conventionally, a method of arranging a microlens array at a position just in front of the image sensor to suppress the incident angle on the imaging surface of the image sensor is known. However, this method is limited in reducing the incident angle, and as the size of the imaging optical system is reduced, coloring around the periphery of the image (called false color) causes a problem.

[0030] Therefore, the optical system according to each example reduces the incident angle on the imaging surface by setting at least one surface of the optical element as a diffraction surface having a controlled wavelength dispersion characteristic.

[0031] The imaging optical system according to each example satisfies the following inequality (1):

[0032] -1.5 < Tk / f1 < 0.2 (1)

[0033] Wherein Tk is the exit pupil position of the imaging lens L by setting the object side to negative with respect to the image plane as a reference, and f1 is the focal length of the optical element (optical element MOE in the imaging optical system of each example) including a diffraction surface having controlled wavelength dispersion characteristics.

[0034] Inequality (1) defines the relationship between the exit pupil position of the imaging lens L and the refractive power of the optical element MOE. Satisfying inequality (1) can suppress the incident angle on the image sensor. In the case where the focal length of the optical element MOE becomes smaller relative to the exit pupil position and the value becomes lower than the lower limit of inequality (1), the structure of the diffraction surface becomes complicated and it becomes difficult to manufacture the optical element MOE. In addition, the exit pupil of the imaging optical system becomes positive beyond the telecentric position, and the incident angle on the imaging surface increases. In the case where the focal length of the optical element MOE becomes larger relative to the exit pupil position and the value becomes higher than the upper limit of inequality (1), the refractive power of the optical element MOE becomes insufficient and it becomes difficult to suppress the incident angle on the image sensor, or the imaging optical system becomes larger.

[0035] When the optical element MOE is endowed with refractive power, a light beam can be bent in a desired direction at a specific wavelength, but unless light beams of different wavelengths are properly controlled, lateral chromatic aberration occurs at the periphery of the image and it becomes difficult to acquire a high-definition image.

[0036] The imaging optical system according to each example satisfies the following inequality (2):

[0037] -0.10 < 1 / ν0 < 0.02 (2)

[0038] where ν0 is the Abbe number of the diffractive surface with controlled wavelength dispersion. d = 0.58756 μm) and the main dispersion is F line (λ F =0.48613μm) and C line (λ C =0.65627 μm), the Abbe number ν0 is defined by the following equation:

[0039]

[0040] Where ψ(λ d ),ψ(λ F ) and ψ(λ C ) is the optical path difference function for the wavelengths of the d-line, F-line, and C-line, and P(λ d ), P(λ F ) and P(λ C ) is the optical path difference dispersion of the surface for the wavelengths of the d-line, F-line and C-line.

[0041] Satisfying inequality (2) can provide an image without chromatic aberration even when the incident angle on the image sensor is suppressed using inequality (1). In the case where negative dispersion increases and the value becomes lower than the lower limit of inequality (2), lateral chromatic aberration on the short wavelength side appears on the overexposed side and image quality deteriorates. In the case where positive dispersion increases and the value becomes higher than the upper limit of inequality (2), lateral chromatic aberration on the short wavelength side appears on the underexposed side and image quality deteriorates.

[0042] The imaging lens L generally has a positive refractive power, so that lateral chromatic aberration on the short wavelength side may occur on the underexposed side. Therefore, making the Abbe number of the optical element MOE negative can eliminate the lateral chromatic aberration that occurs in the imaging lens L, and it becomes easier to satisfactorily correct the aberration in the imaging optical system.

[0043] This configuration can realize an imaging optical system that can relax the incident angle on the imaging surface of the image sensor while satisfactorily correcting chromatic aberration.

[0044] Inequalities (1) and (2) can be replaced by inequalities (1a) and (2a):

[0045] -1.40 <Tk / f1<0.15(1a)

[0046] -0.080<1 / ν0<0.015(2a)

[0047] Inequalities (1) and (2) can be replaced by inequalities (1b) and (2b):

[0048] -1.2 <Tk / f1<0.1(1b)

[0049] -0.06<1 / ν0<0.01(2b)

[0050] Now, a description will be given of inequalities that can be satisfied by the imaging optical system according to each example. The imaging optical system according to each example can satisfy one or more of the following inequalities (3) to (6):

[0051] 0.05 < Psum < 0.40 (3)

[0052] -0.050 < ΣΦi / νdi < -0.001 (4)

[0053] 0.8 < fmoe / f1 < 3.0 (5)

[0054] -1.0 < STO / f1 < 2.5 (6)

[0055] Wherein Psum is the Petzval sum of the imaging lens L, Φi is the refractive power of the i-th lens (where i is a natural number) counted from the object side among the lenses constituting the imaging lens L, νdi is the Abbe number of the i-th lens (where i is a natural number) counted from the object side among the lenses constituting the imaging lens L, fmoe is the focal length of the diffraction surface with controlled wavelength dispersion characteristics, and STO is the distance on the optical axis from the image plane (imaging surface) to the aperture stop SP.

[0056] Inequality (3) defines the amount of field curvature of the imaging lens L. Satisfying inequality (3) can eliminate the field curvature that occurs in the optical element MOE and satisfactorily correct the aberration of the imaging optical system. In the case where the Petzval sum of the imaging lens L decreases and the value becomes lower than the lower limit of inequality (3), the field curvature of the imaging optical system occurs on the overexposed side. In the case where the Petzval sum of the imaging lens L increases and the value becomes higher than the upper limit of inequality (3), the field curvature of the imaging optical system occurs on the underexposed side.

[0057] Inequality (4) defines the lateral chromatic aberration of the imaging lens L. Satisfying inequality (4) can eliminate the lateral chromatic aberration occurring in the optical element MOE and satisfactorily correct the aberration of the imaging optical system. In the case where the value becomes lower than the lower limit of inequality (4), the lateral chromatic aberration of the imaging optical system occurs on the overexposed side. In the case where the value becomes higher than the upper limit of inequality (4), the lateral chromatic aberration of the imaging optical system occurs on the underexposed side.

[0058] Inequality (5) specifies the refractive power of the diffraction surface of the optical element MOE having controlled wavelength dispersion characteristics. In the case where the refractive power of the diffraction surface becomes too weak and the value becomes lower than the lower limit of inequality (5), the refractive power of the optical element MOE becomes weak, and the incident angle on the imaging plane becomes larger or the size of the imaging optical system increases. In order to try to maintain the refractive power of the optical element MOE, the refractive power of the surface opposite to the diffraction surface becomes stronger. In the case where the refractive power of the diffraction surface becomes too strong and the value becomes higher than the upper limit of inequality (5), the structure of the diffraction surface becomes complicated and it becomes difficult to manufacture the optical element MOE.

[0059] Inequality (6) defines the relationship between the distance on the optical axis from the image plane to the aperture stop SP and the refractive power of the optical element MOE. When the distance from the image plane to the aperture stop SP increases, the exit pupil position is also separated from the image plane, and an effect similar to that of inequality (1) is obtained. When the distance on the optical axis from the image plane to the aperture stop SP becomes smaller relative to the focal length of the optical element MOE and the value becomes lower than the lower limit of inequality (6), the refractive power of the optical element MOE becomes stronger, the structure of the diffraction surface becomes complicated, and it becomes difficult to manufacture the optical element MOE. When the distance on the optical axis from the image plane to the aperture stop SP becomes larger relative to the focal length of the optical element MOE and the value becomes higher than the upper limit of inequality (6), the refractive power of the optical element MOE becomes insufficient, and it becomes difficult to suppress the incident angle on the image sensor, or the size of the imaging optical system increases.

[0060] Inequalities (3) to (6) can be replaced by inequalities (3a) to (6a):

[0061] 0.10 <Psum<0.35(3a)

[0062] -0.030<ΣΦi / νdi<-0.003(4a)

[0063] 0.9 <fmoe / f1<2.5(5a)

[0064] -0.5 <STO / f1<2.0(6a)

[0065] Inequalities (3) to (6) can be replaced by inequalities (3b) to (6b):

[0066] 0.15 <Psum<0.30(3b)

[0067] -0.015<ΣΦi / νdi<-0.005(4b)

[0068] 0.95 <fmoe / f1<2.00(5b)

[0069] -0.2 <STO / f1<1.5(6b)

[0070] Now, a detailed description will be given of the imaging optical system according to each example.

[0071] The imaging optical system according to Example 1 is an optical system with a focal length of 2.30 mm, an F number of 2.50, and a half viewing angle of 56.31 degrees. The imaging lens L is composed of six lenses (the first lens to the sixth lens) having negative refractive power, positive refractive power, positive refractive power, negative refractive power, positive refractive power, and negative refractive power, which are arranged in sequence from the object side to the image side. All six lenses have aspherical surfaces on both sides. The aperture stop SP is disposed between the first lens and the second lens. The optical element MOE is arranged between the imaging lens L and the image sensor IM. The surface on the object side of the optical element MOE is a diffraction surface with a controlled wavelength dispersion characteristic, and the dispersion of the diffraction surface is set to zero dispersion. Arranging the diffraction element on a flat plate can reduce the difficulty of manufacturing.

[0072] The imaging optical system according to Example 2 is an optical system having a focal length of 2.22 mm, an F number of 2.50, and a half viewing angle of 57.20 degrees. The configuration of the imaging lens L is similar to the configuration according to Example 1. The optical element MOE is arranged between the imaging lens L and the image sensor IM. The surface on the object side of the optical element MOE has a convex shape facing the object side, and shares the refractive power of the optical element MOE. The surface on the image side of the optical element MOE is a diffraction surface having a controlled wavelength dispersion characteristic, and the diffraction surface has a negative dispersion with an Abbe number of -23.31.

[0073] The imaging optical system according to Example 3 is an optical system having a focal length of 2.33 mm, an F number of 2.50, and a half viewing angle of 52.14 degrees. The configuration of the imaging lens L is similar to that of Example 1. The optical element MOE is disposed between the imaging lens L and the image sensor IM. In Example 3, aberrations are corrected only in the imaging lens L, and imaging is feasible without using the optical element MOE when the image sensor has good angular characteristics. In other words, deploying the optical element MOE according to Example 3 in a conventional imaging lens can only change the incident angle characteristics of the image sensor. The surface on the object side of the optical element MOE is a diffraction surface having a controlled wavelength dispersion characteristic, and the configuration and dispersion of the diffraction surface are similar to those of Example 1.

[0074] In each example, the aberration may be corrected by image processing, or another method may be used. The structure that implements the optical path difference function of the diffractive optical element may be a so-called single-layer metasurface in which the metasurface includes a single layer, or may be a so-called stacked metasurface in which the metasurface includes multiple layers. The optical element according to the present disclosure may have a metasurface on the surface of a low-pass filter, an IR cutoff filter, etc. deployed near an image sensor. This makes it possible to reduce the number of components and realize a compact imaging optical system. In addition to the optical element of the present disclosure, an optical block not shown may be used as a low-pass filter or an IR cutoff filter.

[0075] A description will be given of numerical examples corresponding to Example 1 to Example 3.

[0076] 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 m-th 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 based on the d-line. The Abbe number νd of a specific material is represented as follows:

[0077] νd=(Nd-1) / (NF-NC)

[0078] Where Nd, NF and NC are the refractive indices for the d-line (587.6nm), F-line (486.1nm) and C-line (656.3nm) in the Fraunhofer line:

[0079] In each numerical example, d, focal length (mm), F number and half angle of view (degrees) are all values ​​when the imaging optical system according to each example is in a focused state on an object at infinity. The "back focal length" is the distance on the optical axis from the last lens surface (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 frontmost lens surface (lens surface closest to the object) of the imaging optical system to the last surface plus the back focal length.

[0080] In the case where the optical surface is aspherical, an asterisk * is added to the right side of the surface number. The aspherical shape is represented as follows:

[0081] 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 12Where 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 curvature radius, 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 ”.

[0082] The optical path difference function of the surface at the design wavelength is expressed as follows:

[0083] ψ0=U2·h 2 +U4·h 4 +U6·h 6 +U8·h 8 +U10·h 10

[0084] Where U2, U4, U6, U8, and U10 are the coefficients of the optical path difference function of the surface. "Diffraction" refers to a surface that uses the optical path difference function of the surface for optical design.

[0085] Numerical Example 1

[0086] Unit: mm

[0087] Surface data

[0088]

[0089]

[0090] Aspheric surface data

[0091] Surface 1

[0092] K=9.90007e+01 A4=2.48086e-01 A6=-2.42915e-01A8=2.91689e-01 A10=-2.24650e-01 A12=9.59098e-02 A14=-1.21432e-02A16=-2.95944e-03

[0093] Surface 2

[0094] K=4.89422e+00A4=3.65560e-01A6=-8.43191e-02A8=-1.86680e+00A1 0=1.12029e+01A12=-2.75888e+01A14=3.37170e+01A16=-1.63504e+01

[0095] Surface 4

[0096] K=0.00000e+00A4=-1.08610e-02A6=1.79646e-01A8=-6.50335e-01A10=7.01469e-01

[0097] Surface 5

[0098] K=0.00000e+00A4=-8.90619e-03A6=-4.86125e-02A8=8.44771e-02A10=-1.88038e-02A12=-4.18980e-02

[0099] Surface 6

[0100] K=0.00000e+00A4=-4.08132e-03A6=-4.54474e-02A8=9.77174e-04A10=8.27491e-02A12=-4.01016e-02

[0101] Surface 7

[0102] K=0.00000e+00A4=-7.51533e-02A6=-3.28907e-02A8=-3.45258e-02A10=4.12748e-02

[0103] Surface 8

[0104] K=0.00000e+00A4=5.21400e-02A6=7.67770e-02A8=-7.40533e-02A10=5.55810e-02A12=-1.60881e-02

[0105] Surface 9

[0106] K=0.00000e+00A4=-6.05322e-02A6=1.04622e-01A8=-3.05453e-02A10=-1.53191e-04A12=6.91537e-04

[0107] Surface 10

[0108] K=0.00000e+00A4=4.01857e-02A6=-1.81149e-02A8=1.72265e-03A10=-1.66674e-04

[0109] Surface 11

[0110] K=0.00000e+00A4=2.01306e-01A6=-5.98149e-02A8=8.38921e-03A10=-4.89678e-04

[0111] Surface 12

[0112] K=-8.04920e-01A4=-1.61372e-01A6=3.19208e-02A8=-4.59935e-03A10=2.10178e-04

[0113] Surface 13

[0114] K=-2.72052e+00A4=-7.06132e-02A6=1.96761e-02A8=-3.53477e-03A10=3.92793e-04A12=-2.73824e-05A14=8.58965e-07

[0115] 14th surface (diffraction surface)

[0116] U2=-5.63346e-02U4=-1.68445e-03U6=7.13021e-05

[0117] Surface optical path difference dispersion

[0118] P(λ)=0.58756 / λ

[0119] Various data

[0120]

[0121] Numerical Example 2

[0122] Unit: mm

[0123] Surface data

[0124]

[0125]

[0126] Aspheric surface data

[0127] Surface 1

[0128] K=-3.86919e+01 A4=2.41588e-01 A6=-2.41928e-01A8=2.89633e-01 A10=-2.23921e-01 A12=9.59516e-02 A14=-1.20885e-02A16=-2.78335e-03

[0129] Surface 2

[0130] K=5.21399e+00A4=3.42258e-01A6=-6.13440e-02A8=-2.00079e+00A1 0=1.13128e+01A12=-2.74538e+01A14=3.35094e+01A16=-1.61949e+01

[0131] Surface 4

[0132] K=0.00000e+00A4=9.18393e-03A6=7.97704e-02A8=-5.19262e-01A10=6.29534e-01

[0133] Surface 5

[0134] K=0.00000e+00A4=-1.94958e-02A6=-1.77983e-02A8=9.07516e-02A10=-4.91208e-02A12=-2.60306e-02

[0135] Surface 6

[0136] K=0.00000e+00A4=-1.38771e-02A6=-3.44599e-02A8=6.51807e-03A10=6.68454e-02A12=-3.25873e-02

[0137] Surface 7

[0138] K=0.00000e+00A4=-7.64664e-02A6=-4.08103e-02A8=-2.21156e-02A10=3.46808e-02

[0139] Surface 8

[0140] K=0.00000e+00A4=4.41172e-02A6=6.68996e-02A8=-6.35215e-02A10=4.88373e-02A12=-1.42106e-02

[0141] Surface 9

[0142] K=0.00000e+00A4=-5.89835e-02A6=1.02374e-01A8=-3.03807e-02A10=2.55099e-04A12=6.73171e-04

[0143] Surface 10

[0144] K=0.00000e+00A4=4.39231e-02A6=-2.01611e-02A8=2.61684e-03A10=-2.35583e-04

[0145] Surface 11

[0146] K=0.00000e+00A4=2.03568e-01A6=-5.99845e-02A8=8.58443e-03A10=-5.16256e-04

[0147] Surface 12

[0148] K=-7.88543e-01A4=-1.65961e-01A6=3.13932e-02A8=-4.46084e-03A10=2.04899e-04

[0149] Surface 13

[0150] K=-2.54988e+00A4=-6.93865e-02A6=1.89535e-02A8=-3.52069e-03A10=3.91221e-04A12=-2.48839e-05A14=6.71496e-07

[0151] 15th surface (diffraction surface)

[0152] U2=-1.13692e-01U4=1.50559e-03U6=1.19260e-04

[0153] Surface optical path difference dispersion

[0154] P(λ)=13.87546·λ 10 -153.95668 · λ 9 +1009.95630 λ 8 -4356.52716

[0155] ·λ 7 +13006.44877 λ 6 -27470.79737 · λ 5 +41106.88437 · λ4 -42762.08537 · λ 3 +29486.82651 λ 2 -12144.39247·λ+2266.41068

[0156] Various data

[0157]

[0158] Numerical Example 3

[0159] Unit: mm

[0160] Surface data

[0161]

[0162] Aspheric surface data

[0163] Surface 1

[0164] K=-3.72021e+01 A4=2.52858e-01 A6=-2.57610e-01 A8=3.23789e-01 A10=-2.85442e-01 A12=1.57126e-01 A14=-4.41254e-02A16=3.72864e-03

[0165] Surface 2

[0166] K=2.88135e+00 A4=3.98563e-01 A6=-4.23396e-01A8=6.89592e-01A10=1.58942e+00A12=-8.42291e+00A14=1.49105e+01A16=-9.39537e+00

[0167] Surface 4

[0168] K=0.00000e+00A4=-1.88163e-02A6=5.88929e-02A8=-3.59062e-01A10=3.48112e-01

[0169] Surface 5

[0170] K=0.00000e+00A4=-1.23712e-01A6=1.00415e-01A8=-1.35266e-01A10=1.52765e-01A12=-1.11587e-01

[0171] Surface 6

[0172] K=0.00000e+00A4=-1.04125e-01A6=7.39184e-02A8=-4.58902e-02A10=2.90998e-02A12=-7.76881e-03

[0173] Surface 7

[0174] K=0.00000e+00A4=6.98768e-02A6=-2.51434e-01A8=1.44386e-01A10=-2.27035e-02

[0175] Surface 8

[0176] K=0.00000e+00A4=3.43960e-01A6=-2.88160e-01A8=1.64638e-01A10=-4.44706e-02A12=5.28482e-03

[0177] Surface 9

[0178] K=0.00000e+00A4=1.19248e-01A6=-2.42456e-02A8=-2.70298e-03A10=2.28000e-03A12=-3.77003e-04

[0179] Surface 10

[0180] K=0.00000e+00A4=5.33684e-02A6=-3.98652e-02A8=9.60901e-03A10=-1.54167e-03

[0181] Surface 11

[0182] K=0.00000e+00A4=1.80297e-01A6=-5.20218e-02A8=7.19376e-03A10=-4.36277e-04

[0183] Surface 12

[0184] K=-9.38278e-01A4=-1.84025e-01A6=3.24158e-02A8=-4.27734e-03A10=3.23634e-04

[0185] Surface 13

[0186] K=-2.76835e+00A4=-9.81714e-02A6=3.21162e-02A8=-7.34394e-03A10=1.04738e-03A12=-8.68086e-05A14=3.14568e-06

[0187] 14th surface (diffraction surface)

[0188] U2=9.57493e-03U4=-6.02019e-03U6=1.10748e-04U8=-3.78986e-06

[0189] Surface optical path difference dispersion

[0190] P(λ)=0.58756 / λ

[0191] Various data

[0192]

[0193]

[0194] Table 1 summarizes the various values ​​in each numerical example.

[0195]

[0196] Image pickup device

[0197] Now refer to Figure 7 , a description will be given of an example of a digital still camera (image pickup device) having any one of the imaging optical systems according to Example 1 to Example 3. Figure 7 An image pickup apparatus having any of the imaging optical systems according to Examples 1 to 3 is illustrated.

[0198] exist Figure 7 , reference numeral 20 denotes a camera body, and reference numeral 21 denotes an imaging optical system according to any one of Examples 1 to 3. Reference numeral 22 denotes a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body 20 and receives and photoelectrically converts an object image (optical image) formed by the imaging optical system 21. Reference numeral 23 denotes a memory that records information corresponding to the object image photoelectrically converted by the solid-state image sensor 22. Reference numeral 24 denotes a viewfinder that includes a liquid crystal display panel and the like and is configured to observe the object image formed on the solid-state image sensor 22. The camera body 20 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.

[0199] Therefore, applying the imaging optical system according to each example to an image pickup apparatus such as a digital still camera can provide an image pickup apparatus that can relax the incident angle on the image sensor while satisfactorily correcting chromatic aberration.

[0200] While the present disclosure has been described with reference to the embodiments, it is to be understood that the present disclosure is 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 imaging optical system, comprising: Imaging lens; as well as an optical element disposed on the image side of the imaging lens, wherein at least one surface of the optical element is a diffractive surface having controlled wavelength dispersion characteristics, and where ν0 is the Abbe number of the diffractive surface, the reference wavelength is the d-line, the main dispersions are the F-line and the C-line, and ψ(λ d ),ψ(λ F ) and ψ(λ C ) are the optical path difference functions for d-line, F-line and C-line, respectively, P(λ d ), P(λ F ) and P(λ C ) are the optical path difference dispersions of the surface for d-line, F-line and C-line respectively, and the following equation is satisfied: and The following inequality is satisfied: -1.5 <Tk / f1<0.2 -0.10<1 / ν0<0.02 Wherein, Tk is the exit pupil position of the imaging lens with a negative sign relative to the object side of the image plane as a reference, and f1 is the focal length of the optical element.

2. The imaging optical system according to claim 1, wherein: The following inequality is satisfied: 0.05 <Psum<0.40 Wherein, Psum is the Petzval sum of the imaging lens.

3. The imaging optical system according to claim 1, wherein: The following inequality is satisfied: -0.050<ΣΦi / νdi<-0.001 Here, Φi and νdi are respectively the refractive power and the Abbe number of the i-th lens counted from the object side among the lenses included in the imaging lens, where i is a natural number.

4. The imaging optical system according to claim 1, wherein: The following inequality is satisfied: 0.8 <fmoe / f1<3.0 where fmoe is the focal length of the diffractive surface.

5. The imaging optical system according to claim 1, wherein: The following inequality is satisfied: -1.0 <STO / f1<2.5 Here, STO is the distance on the optical axis from the image plane to the aperture stop included in the imaging lens.

6. The imaging optical system according to any one of claims 1 to 5, wherein: The imaging lens is composed of, from the object side to the image side, a first lens with negative refractive power, a second lens with positive refractive power, a third lens with positive refractive power, a fourth lens with negative refractive power, a fifth lens with positive refractive power, and a sixth lens with negative refractive power. 7 . The imaging optical system according to claim 6 , further comprising an aperture stop disposed between the first lens and the second lens.

8. An imaging optical system, comprising: Imaging lens; as well as an optical element disposed on the image side of the imaging lens, wherein at least one surface of the optical element is a metasurface having controlled wavelength dispersion properties, Where ν0 is the Abbe number of the metasurface, the reference wavelength is the d-line, the main dispersion is the F-line and the C-line, ψ(λ d ),ψ(λ F ) and ψ(λ C ) are the optical path difference functions for d-line, F-line and C-line, respectively, P(λ d ), P(λ F ) and P(λ C ) are the optical path difference dispersions of the surface for d-line, F-line and C-line respectively, and the following equation is satisfied: and The following inequality is satisfied: -1.5 <Tk / f1<0.2 -0.10<1 / ν0<0.02 Wherein, Tk is the exit pupil position of the imaging lens with a negative sign relative to the object side of the image plane as a reference, and f1 is the focal length of the optical element.

9. An image pickup device, comprising: The imaging optical system according to any one of claims 1 to 8; as well as An image sensor is configured to image an object through the imaging optical system.

Images