Optical system and imaging apparatus including the same

Abstract

The invention discloses an optical system and an imaging apparatus including the same. An optical system includes a first lens unit, a second lens unit having a negative refractive power, a third lens unit, and a fourth lens having a positive refractive power arranged in order from an object side to an image side. During focusing, an interval between adjacent ones of the lens units changes. During focusing from infinity to close, the second lens unit moves toward the image side and the fourth lens unit moves toward the object side. A certain inequality is satisfied.

Description

Technical Field

[0001] The present invention relates to an optical system and is suitable for application to imaging devices such as a digital video camera, a digital still camera, a broadcast camera, and a silver halide film camera. Background Art

[0002] In recent years, it has been desired to use a compact optical system capable of performing high-speed focusing in an imaging device.

[0003] Therefore, a method for moving a plurality of lens units during focusing has been proposed to provide a compact structure for reducing changes in aberrations during focusing while reducing the weight of the lens units that are moved during focusing.

[0004] Japanese Patent Application Publication No. 2022-140076 describes an optical system in which a second lens unit and a fourth lens move during focusing.

[0005] Japanese Patent Application Publication No. 2022-140076 describes a structure including a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a fifth lens unit having a negative refractive power, which are arranged in order from the object side to the image side. However, the second lens unit that moves during focusing has an excessively strong refractive power, thus causing an increase in so-called variation - that is, an increase in the variation of the angle of view during focusing. Summary of the invention

[0006] An optical system according to one aspect of the present invention comprises a first lens unit, a second lens unit having a negative refractive power, a third lens unit, and a fourth lens unit having a positive refractive power, which are arranged in sequence from the object side to the image side. During focusing, the intervals between adjacent lens units in the lens units change. During focusing from infinity to a close distance, the second lens unit moves toward the image side and the fourth lens unit moves toward the object side. The first lens unit comprises a negative meniscus lens and a positive lens, the negative meniscus lens having a convex surface facing the object side.

[0007] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a cross-sectional view of lenses of the optical system when the optical system according to the first embodiment is focused on infinity.

[0009] Figure 2A and Figure 2B Aberration diagrams of the optical system when the optical system according to the first embodiment is focused at infinity and at a close distance, respectively, are shown.

[0010] Figure 3 is a cross-sectional view of lenses of the optical system when the optical system according to the second embodiment is focused on infinity.

[0011] Figure 4A and Figure 4B Aberration diagrams of the optical system when the optical system according to the second embodiment is focused at infinity and at a close distance, respectively, are shown.

[0012] Figure 5 is a cross-sectional view of lenses of the optical system when the optical system according to the third embodiment is focused on infinity.

[0013] Fig. 6A and Figure 6B Aberration diagrams of the optical system when the optical system according to the third embodiment is focused at infinity and at a close distance, respectively, are shown.

[0014] Figure 7 is a cross-sectional view of lenses of the optical system when the optical system according to the fourth embodiment is focused on infinity.

[0015] Fig. 8A and Figure 8B Aberration diagrams of the optical system when the optical system according to the fourth embodiment is focused at infinity and at a close distance, respectively, are shown.

[0016] Fig. 9 is a cross-sectional view of lenses of the optical system when the optical system according to the fifth embodiment is focused on infinity.

[0017] Fig. 10A and Fig. 10B Aberration diagrams of the optical system when the optical system according to the fifth embodiment is focused at infinity and at a close distance, respectively, are shown.

[0018] Fig.11 is a cross-sectional view of lenses of the optical system when the optical system according to the sixth embodiment is focused on infinity.

[0019] Fig. 12A and Fig. 12B Aberration diagrams of the optical system when the optical system according to the sixth embodiment is focused at infinity and at a close distance, respectively, are shown.

[0020] Fig.13 is a cross-sectional view of lenses of the optical system when the optical system according to the seventh embodiment is focused on infinity.

[0021] Fig.14A and Fig. 14B Aberration diagrams of the optical system when the optical system according to the seventh embodiment is focused on infinity and a close distance, respectively, are shown.

[0022] Fig.15An arrangement including a flare cut-off stop is illustrated.

[0023] Fig.16 is a schematic diagram illustrating an imaging device. DETAILED DESCRIPTION

[0024] An optical system and an imaging device including the same according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0025] Figure 1 , Figure 3 , Figure 5 , Figure 7 , Fig. 9 , Fig.11 and Fig.13 : is a cross-sectional view of the optical system L0 when the optical system L0 according to the first to sixth embodiments is focused at infinity. The optical system L0 of each embodiment is an optical system included in an imaging device such as a digital video camera, a digital still camera, a broadcast camera, a silver halide film camera, a surveillance camera, or a vehicle-mounted camera.

[0026] In each cross-sectional view of the lens, the left side is the object side and the right side is the image side. The optical system L0 of each embodiment can be used as a projection lens of a projector, etc. In this case, the screen is on the left and the projected image is on the right.

[0027] The optical system L0 of each embodiment includes a first lens unit L1, a second lens unit L2 having a negative refractive power, a third lens unit L3, and a fourth lens unit L4 having a positive refractive power, which are arranged in sequence from the object side to the image side. During focusing, the intervals between adjacent lens units in the lens units change. Each lens unit may be composed of a single lens or a plurality of lenses. The lens unit may include an aperture stop.

[0028] In the cross-sectional view of the lens, the downward solid arrow shows the movement locus of the lens unit during focusing from infinity to a close distance.

[0029] In each cross-sectional view of the lens, SP represents an aperture stop, and IP represents an image plane. When the optical system L0 of each embodiment is included in a digital still camera or a digital video camera, an imaging plane of a solid-state imaging device (photoelectric converter) such as a CCD sensor or a CMOS sensor is disposed on the image plane IP. When the optical system L0 of each embodiment is used as an image capturing optical system of a silver halide film camera, a photosensitive surface corresponding to a film surface is disposed on the image plane IP.

[0030] GB denotes an optical block corresponding to, for example, an optical filter, a panel, a crystal low-pass filter, or an infrared cut filter.

[0031] Figure 2A , Figure 4A , Fig. 6A , Fig. 8A , Fig. 10A , Fig. 12A and Fig.14A Aberration diagrams of the optical systems when the optical systems according to the first to seventh embodiments are focused on infinity are shown.

[0032] Figure 2B , Figure 4B , Figure 6B , Figure 8B , Fig. 10B , Fig. 12B and Fig. 14B Aberration diagrams are shown when the optical systems according to the first to seventh embodiments are focused at a close distance.

[0033] In the spherical aberration diagram, Fno is the F number, and the solid line and the dotted line respectively represent the amount of spherical aberration for the d-line (wavelength 587.6nm) and the g-line (wavelength 435.8nm). In the astigmatism diagram, the solid line shows the amount of astigmatism in the sagittal image plane, and the dotted line shows the amount of astigmatism in the meridional image plane. The distortion diagram shows the amount of distortion for the d-line. The chromatic aberration diagram shows the amount of lateral chromatic aberration for the g-line. In addition, ω is the imaging half angle of view (°).

[0034] Fig.15 An optical system L0 according to the first embodiment including a spot cut-off stop for blocking light is shown. FC1 denotes a spot cut-off stop disposed in the first lens unit L1, and FC4 denotes a spot cut-off stop disposed in the fourth lens unit L4.

[0035] Now, a characteristic structure of the optical system according to the embodiment will be described.

[0036] The optical system L0 of each embodiment includes a first lens unit L1, a second lens unit L2 having a negative refractive power, a third lens unit L3, and a fourth lens unit L4 having a positive refractive power, which are arranged in order from the object side to the image side. During focusing, the intervals between adjacent lens units in the lens units change. Since the lens units move during focusing, the aberration variation during focusing can be reduced.

[0037] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side, and the fourth lens unit L4 moves toward the object side. The second lens L2 and the fourth lens unit L4 having refractive powers of different signs move so that the interval between the second lens L2 and the fourth lens unit L4 along the optical axis is reduced. As a result, during focusing from infinity to a close distance, the change in the incident height of off-axis light on each lens unit can be reduced, so that the change in the angle of view during focusing from infinity to a close distance can be reduced.

[0038] The optical system L0 of each embodiment according to one aspect is configured to satisfy the following inequality:

[0039] -10.0 < f2 / f < -3.6 (1)

[0040] Here, f2 is the focal length of the second lens unit L2, and f is the focal length of the entire system.

[0041] Inequality (1) is set to reduce aberrations and changes in viewing angle during focusing and achieve size reduction.

[0042] When the value of inequality (1) is higher than the upper limit, the refractive power of the second lens unit L2 is too strong. As a result, the change in the viewing angle during focusing becomes too large. When the value of inequality (1) is lower than the lower limit, the refractive power of the second lens unit L2 is too weak. Therefore, the movement amount of the second lens unit L2 for focusing from infinity to the desired object distance becomes too large. As a result, the total lens length increases.

[0043] Here, the total lens length is the sum of the distance from the surface of the optical system L0 closest to the object side to the surface of the optical system L0 closest to the image side along the optical axis and the back focus. The back focus is a value obtained by air conversion of the distance between the surface of the optical system L0 closest to the image side along the optical axis and the image plane.

[0044] At least one of the upper limit and the lower limit of the numerical range of inequality (1) can be changed to inequality (1a):

[0045] -9.5 <f2 / f<-3.7(1a)

[0046] At least one of the upper limit and the lower limit of the numerical range of inequality (1) can also be changed to inequality (1b):

[0047] -9.0 <f2 / f<-3.8(1b)

[0048] The optical system L0 of each embodiment according to another aspect is configured such that the first lens unit L1 includes a negative meniscus lens having a convex surface facing the object side and a positive lens.

[0049] When the first lens unit L1 includes a negative meniscus lens having a convex surface facing the object side and a positive lens, changes in lateral chromatic aberration and distortion of the first lens unit L1 during focusing from infinity to a close distance can be reduced.

[0050] Now, the structure of the optical system L0 according to each embodiment will be described.

[0051] During image blur correction, the entirety or a portion of the lens element included in the third lens unit L3 may be moved in a direction including a component perpendicular to the optical axis. In order to obtain a desired amount of peripheral light during image blur correction, the diameter of the lens moved during image blur correction is increased. Therefore, by moving the lens element of the third lens unit L3 having a relatively small diameter, an increase in the diameter of the optical system L0 can be suppressed.

[0052] Here, the lens element refers to a single lens or a plurality of lenses.

[0053] The optical system L0 of each embodiment may satisfy one or more of the following inequalities:

[0054] -3.5 < M2 / M4 < -0.5 (2)

[0055] -7.00 < f2 / f4 < -2.50 (3)

[0056] 0.05 < |f1 / f2| < 0.50 (4)

[0057] 2.0 < |fR / f| < 500.0 (5)

[0058] 0.30 < BF / f < 1.50 (6)

[0059] 0.45 < Da / TL < 0.70 (7)

[0060] 0.15 < D4 / Da < 0.35 (8)

[0061] 0.70 < (1-β4 2 )×βR 2 < 3.00 (9)

[0062] 70.0 < ν4p < 96.0 (10)

[0063] Here, M2 and M4 are the movement amounts of the second lens unit L2 and the fourth lens unit L4, respectively, during focusing from infinity to an object distance at which the lateral magnification of the entire system is -0.1. The sign of the movement amount is positive for movement toward the image side.

[0064] In addition, f4 is the focal length of the fourth lens unit L4, and f1 is the focal length of the first lens unit L1.

[0065] In addition, fR is the focal length of the lens unit closest to the image side in the optical system L0, and BF is the back focus when the optical system L0 is focused on infinity.

[0066] The optical system L0 includes an aperture stop SP. In this case, Da is the distance from the aperture stop SP to the image plane along the optical axis when the optical system L0 is focused at infinity. TL is the total lens length of the optical system L0. D4 is the distance from the aperture stop SP to the surface of the fourth lens unit L4 closest to the object side along the optical axis.

[0067] In addition, β4 is the lateral magnification of the fourth lens unit L4 when the optical system L0 is focused on infinity, and βR is the combined lateral magnification of all lens units disposed on the image side of the fourth lens unit L4 when the optical system L0 is focused on infinity.

[0068] In addition, ν4p is the Abbe number of at least one positive lens included in the fourth lens unit L4.

[0069] Now, the technical meanings of inequalities (2) to (10) will be described.

[0070] When the movement amount of the fourth lens unit L4 is too large so that the value of inequality (2) is higher than the upper limit, the change in the incident height of the off-axis light on each lens unit during focusing from infinity to a close distance increases. As a result, the change in the viewing angle during focusing from infinity to a close distance increases. In addition, when the value of inequality (2) is lower than the lower limit, the movement amount of the second lens unit L2 is too large, and the change in the incident height of the off-axis light on each lens unit during focusing from infinity to a close distance increases. As a result, the change in the viewing angle during focusing from infinity to a close distance increases.

[0071] When the value of inequality (3) is higher than the upper limit, the refractive power of the second lens unit L2 is too strong. As a result, the change in the viewing angle during focusing becomes too large. When the value of inequality (3) is lower than the lower limit, the refractive power of the fourth lens unit L4 is too strong. As a result, the change in the viewing angle and field curvature during focusing becomes too large.

[0072] When the value of inequality (4) is higher than the upper limit, the refractive power of the first lens unit L1 is too weak. As a result, the diameter of the first lens unit L1 and the total lens length increase. When the value of inequality (4) is lower than the lower limit, the refractive power of the first lens unit L1 is too strong. As a result, spherical aberration, lateral chromatic aberration, etc. cannot be easily corrected.

[0073] When the value of inequality (5) is higher than the upper limit, the refractive power of the lens unit closest to the image side in the optical system L0 is too weak. As a result, the aberration of each of the lens units included in the optical system L0 cannot be easily corrected. When the value of inequality (5) is lower than the lower limit, the refractive power of the lens unit closest to the image side is too strong. As a result, the field curvature, lateral chromatic aberration, etc. of the lens unit closest to the image side cannot be easily corrected.

[0074] When the back focus increases so that the value of inequality (6) is higher than the upper limit, the total lens length is too long. When the back focus decreases so that the value of inequality (6) is lower than the lower limit, ghost light generated by reflection between the mounted imaging device and the image side surface of the lens closest to the image side easily forms an image on the imaging device.

[0075] When the aperture stop SP is disposed in the optical system L0 so as to be close to the object side so that the value of inequality (7) is higher than the upper limit, the diameter of the lens unit disposed closest to the image side increases. When the aperture stop SP is disposed in the optical system L0 so as to be close to the image side so that the value of inequality (7) is lower than the lower limit, the diameter of the first lens unit L1 increases.

[0076] When the distance from the aperture stop SP along the optical axis to the surface of the fourth lens unit L4 closest to the object side increases so that the value of inequality (8) is higher than the upper limit, the fourth lens unit L4 is disposed at a position where the off-axis light has a large height from the optical axis. As a result, the change in the angle of view during focusing increases.

[0077] When the distance from the aperture stop SP along the optical axis to the surface of the fourth lens unit L4 closest to the object side is reduced so that the value of inequality (8) is lower than the lower limit, the fourth lens unit L4 is disposed at a position where the on-axis light is at a large height from the optical axis. As a result, the change in spherical aberration during focusing increases.

[0078] Inequality (9) relates to the sensitivity to the position of the fourth lens unit L4, that is, the image plane displacement in response to the unit displacement of the fourth lens unit L4 in the optical axis direction. When the sensitivity to the position of the fourth lens unit L4 increases so that the value of inequality (9) is higher than the upper limit, the refractive power of the fourth lens unit L4 is too strong. As a result, the change in aberration during focusing becomes too large.

[0079] When the sensitivity to the position of the fourth lens unit L4 decreases so that the value of inequality (9) falls below the lower limit, the movement amount of the second lens unit L2 for focusing from infinity to a desired object distance becomes too large. As a result, the total lens length increases.

[0080] When the value of the inequality (10) is higher than the upper limit, the refractive index of at least one positive lens included in the fourth lens unit L4 is too low, and, for example, field curvature cannot be easily corrected.

[0081] When the value of the inequality (10) is lower than the lower limit, the Abbe number of at least one positive lens included in the fourth lens unit L4 is too small, and, for example, lateral chromatic aberration cannot be easily corrected.

[0082] At least one of the upper limit and the lower limit of the numerical range of inequalities (2) to (10) may be changed as follows:

[0083] -3.3 <M2 / M4<-0.6(2a)

[0084] -6.90 <f2 / f4<-2.55(3a)

[0085] 0.10<|f1 / f2|<0.47(4a)

[0086] 2.1<|fR / f|<450.0(5a)

[0087] 0.35 <BF / f<1.30(6a)

[0088] 0.50 <Da / TL<0.67(7a)

[0089] 0.17 <D4 / Da<0.33(8a)

[0090] 0.75<(1-β4 2 )×βR 2 <2.80(9a)

[0091] 72.0<ν4p<95.5(10a)

[0092] At least one of the upper limit and the lower limit of the numerical range of inequalities (2) to (10) may also be changed as follows:

[0093] -3.1 <M2 / M4<-0.7(2b)

[0094] -6.80 <f2 / f4<-2.60(3b)

[0095] 0.15<|f1 / f2|<0.45(4b)

[0096] 2.2<|fR / f|<400.0(5b)

[0097] 0.40 <BF / f<1.20(6b)

[0098] 0.55 <Da / TL<0.65(7b)

[0099] 0.20 <D4 / Da<0.31(8b)

[0100] 0.78<(1-β4 2 )×βR 2 <2.50(9b)

[0101] 75.0<ν4p<95.0(10b)

[0102] Now, the detailed structure of the optical system L0 of each embodiment will be described. Regarding the second embodiment and the following embodiments, the differences from the first embodiment will be mainly described.

[0103] First embodiment

[0104] The optical system L0 of the first embodiment includes lens units having positive refractive power, negative refractive power, positive refractive power, positive refractive power, and negative refractive power, which are arranged in sequence from the object side to the image side. During focusing, the intervals between adjacent lens units in the lens units change. The lens units having positive refractive power and the lens units having negative refractive power are appropriately arranged so that changes in aberrations during focusing can be reduced.

[0105] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side, and the fourth lens unit L4 moves toward the object side, so that the change in the incident height of off-axis light on each lens unit is reduced. Therefore, the change in the angle of view during focusing from infinity to a close distance is reduced.

[0106] The second lens unit L2 includes a negative meniscus lens having a convex surface facing the object side. Therefore, weight reduction is achieved, and changes in spherical aberration during focusing are reduced.

[0107] Second embodiment

[0108] The fourth lens unit L4 according to the second embodiment includes a negative meniscus lens having a convex surface facing the image side. Therefore, changes in field curvature during focusing can be easily reduced.

[0109] Third embodiment

[0110] The optical system L0 of the third embodiment includes a negative meniscus lens disposed closest to the image side and having a convex surface facing the image side. Therefore, field curvature can be easily corrected.

[0111] Fourth embodiment

[0112] The optical system L0 of the fourth embodiment includes lens units having negative refractive power, negative refractive power, positive refractive power, positive refractive power, and negative refractive power arranged in order from the object side to the image side. During focusing, intervals between adjacent ones of the lens units change.

[0113] The first lens unit L1 according to the fourth embodiment includes a positive meniscus lens having a convex surface facing the object side. Therefore, spherical aberration can be easily corrected.

[0114] Fifth embodiment

[0115] The optical system L0 of the fifth embodiment includes lens units having positive refractive power, negative refractive power, positive refractive power, positive refractive power, negative refractive power and negative refractive power arranged in order from the object side to the image side. During focusing, intervals between adjacent ones of the lens units change.

[0116] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side, the fourth lens unit L4 moves toward the object side, and the fifth lens unit L5 moves along a trajectory convex toward the object side. Since the three lens units move during focusing from infinity to a close distance, changes in aberrations can be easily reduced.

[0117] Since the fifth lens unit L5 and the sixth lens unit L6 have negative refractive power, the total lens length can be easily reduced by positioning the principal point of the optical system L0 on the object side.

[0118] Sixth embodiment

[0119] The optical system L0 of the sixth embodiment includes lens units having positive refractive power, negative refractive power, positive refractive power, positive refractive power, negative refractive power, and positive refractive power arranged in order from the object side to the image side. During focusing, intervals between adjacent ones of the lens units change.

[0120] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side, the fourth lens unit L4 moves toward the object side, and the fifth lens unit L5 moves along a trajectory convex toward the object side. Since the three lens units move during focusing from infinity to a close distance, changes in aberrations can be easily reduced.

[0121] Since the fifth lens unit L5 and the sixth lens unit L6 have refractive powers of different signs, lateral chromatic aberration and field curvature of the fifth lens unit L5 and the sixth lens unit L6 easily cancel each other.

[0122] Seventh embodiment

[0123] The optical system L0 of the seventh embodiment includes lens units having positive refractive power, negative refractive power, positive refractive power, positive refractive power, and positive refractive power arranged in order from the object side to the image side. During focusing, intervals between adjacent ones of the lens units change.

[0124] Since the fifth lens unit L5 has positive refractive power, the incident angle of light with respect to the normal direction of the image plane can be reduced, so that color misregistration (color shading) occurring when the imaging device is deployed can be easily reduced.

[0125] In the optical system L0 of each embodiment, the positive lens and the negative lens forming the cemented lens can be bonded together using an adhesive having a thickness of 0.005 mm or more and 0.050 mm or less along the optical axis. When the thickness is less than 0.005 mm, the lenses are easily separated. When the thickness is greater than 0.030 mm, the distance from the surface of the cemented lens closest to the object side to the surface of the cemented lens closest to the image side along the optical axis increases, so the total lens length increases. The thickness can be 0.008 mm or more and 0.020 mm or less.

[0126] An anti-reflection film for preventing reflection may be applied to at least one of the lenses included in the optical system L0 of each embodiment. The anti-reflection film may include a plurality of layers.

[0127] When Nd is the refractive index of the layer closest to the air interface for the d-line, an anti-reflection film PC having an Nd of 1.32 or less can be used. When Nd is 1.32 or less, the difference in refractive index between the layer and the air can be reduced. Therefore, the reflectivity of light can be further reduced, and ghosting can be reduced accordingly.

[0128] Examples of the structure of the anti-reflection film PC include a multilayer film formed by a wetting method described in Japanese Patent Application Publication No. 2012-230211 and Japanese Patent Application Publication No. 2014-95877. However, the anti-reflection film PC is not limited to these examples. When Nd is 1.30 or less, ghosting can be further reduced.

[0129] When lens A is the lens closest to the object side and lens B is the lens second closest to the object side among the negative lenses included in the optical system L0 and having a concave surface facing the image side, the anti-reflection film PC may be applied to the image side surface of lens A or lens B. The image side surfaces of lens A and lens B tend to have a large aperture angle, and light reflected in an area having a large aperture angle tends to have a large reflection angle relative to the normal direction of the lens surface. Therefore, the reflectivity is easily increased.

[0130] In addition, light reflected by a negative lens having a concave surface facing the image side is easily condensed on the image plane, so ghosting can be easily noticed. Therefore, by applying an antireflection film PC to the image side surface of lens A or lens B, ghosting can be reduced.

[0131] In each embodiment, a spot cut-off stop may be provided to block light. Fig.15 The optical system L0 according to the first embodiment including the spot cut-off stop is shown. Fig.15 A structure including a spot cut-off aperture is described.

[0132] The first lens unit L1 may include at least one spot cut-off stop FC1. Fig.15 In the embodiment of the present invention, the lower line of the off-axis marginal light incident on the first lens unit L1 from the lower position on the object side can be appropriately blocked, so that the coma aberration can be reduced.

[0133] The fourth lens unit L4 may include at least one spot cut-off stop FC4. Fig.15 In the embodiment of the present invention, the upper line of the off-axis marginal light incident on the first lens unit L1 from the lower position on the object side can be appropriately blocked, so that the coma aberration can be reduced.

[0134] The above-described arrangement of the spot cutoff stop is not limited to the first embodiment, and can be similarly applied to the second to seventh embodiments to reduce coma aberration.

[0135] Now, first to seventh numerical examples corresponding to the first to seventh embodiments will be described.

[0136] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, d (mm) is the interval along the axis (the distance along the optical axis) between the mth surface and the (m+1)th surface, wherein m is the number of each surface counted from the light incident side. In addition, nd is the refractive index of each optical member for the d line, and νd is the Abbe number of each optical member. When Nd, NF, and NC are the refractive indices of a certain material of the d line (wavelength 587.6nm), the F line (wavelength 486.1nm), and the C line (wavelength 656.3nm) of the Fraunhofer line, respectively, the Abbe number νd of the material can be expressed as follows:

[0137] νd=(Nd-1) / (NF-NC)

[0138] BF stands for back focal length.

[0139] When the corresponding optical surface is an aspherical surface, the symbol "*" is attached to the right side of the surface number. When X is the displacement relative to the surface vertex in the optical axis direction, 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 aspherical coefficients of various orders, the aspherical surface can be expressed by the following equation:

[0140] 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

[0141] +A12×h12

[0142] For each of the aspherical coefficients, “e±XX” means “×10±XX”.

[0143] The lens structure length of each lens unit is the distance from the surface closest to the object side to the surface closest to the image side along the optical axis.

[0144] In various data, intervals between adjacent lens units along the optical axis are shown in the lens units when the lateral magnification of the entire system is 0.0 (INF), -0.1, close distance, etc. INF represents infinity.

[0145] First numerical example

[0146] Measurement unit: mm

[0147] Surface data

[0148]

[0149]

[0150] Aspheric surface data

[0151] Surface 2

[0152] K=0.00000e+00A4=-1.54852e-06A6=-1.39851e-08A8=4.03181e-11A10=-1.18272e-13

[0153] Surface 21

[0154] K=0.00000e+00A4=-1.44287e-05A6=-1.34545e-08A8=2.95087e-11A10=-3.61239e-13A12=6.97332e-16

[0155] Surface 22

[0156] K=0.00000e+00A4=5.35853e-06A 6=-2.56320e-08A8=1.20016e-10A10=-4.84989e-13A12=8.09237e-16

[0157] Various data

[0158]

[0159]

[0160]

[0161] Lens unit data

[0162] Second numerical example Measurement unit mm Surface data

[0163]

[0164] Aspheric surface data

[0165] Surface 2

[0166] K=0.00000e+00A 4=6.14218e-07A 6=5.28540e-09A 8=-2.21840e-11A10=6.93534e-14

[0167] Surface 21

[0168] K=0.00000e+00A4=-8.89677e-06A6=-5.76603e-09A8=2.46003e-11A10=-1.08980e-13A12=1.29068e-16

[0169] Surface 22

[0170] K=0.00000e+00A4=2.85669e-06A 6=-6.12974e-09A8=2.49444e-11A10=-5.50422e-14A12=4.81648e-17

[0171] Various data

[0172]

[0173]

[0174] Lens unit data

[0175]

[0176] Third numerical example

[0177] Measurement unit: mm

[0178] Surface data

[0179]

[0180]

[0181] Aspheric surface data

[0182] Surface 21

[0183] K=0.00000e+00A4=-7.68130e-06A6=-9.12882e-10A8=2.65012e-11A10=-7.89662e-14A12=1.31928e-16

[0184] Surface 22

[0185] K=0.00000e+00A4=4.42473e-06A 6=-2.12367e-09A8=3.53558e-11A10=-6.57718e-14A12=1.35297e-16

[0186] Various data

[0187]

[0188]

[0189] Lens unit data

[0190]

[0191] Fourth Numerical Example

[0192] Measurement unit: mm

[0193] Surface data

[0194]

[0195]

[0196] Aspherical surface data 2nd surface

[0197] K=0.00000e+00A4=-7.52192e-07A6=-6.39173e-09A8=1.90775e-11A10=-4.34826e-14

[0198] Surface 21

[0199] K=0.00000e+00A4=-1.59674e-05A6=1.32646e-09A8=-1.63157e-10A10=1.83632e-12A12=-4.38378e-15

[0200] Surface 22

[0201] K=0.00000e+00A4=4.55728e-06A 6=-5.06476e-09A8=5.47838e-12A10=1.16038e-12A12=-3.04625e-15

[0202] Various data

[0203]

[0204]

[0205] Lens unit data

[0206]

[0207] Fifth numerical example

[0208] Measurement unit: mm

[0209] Surface data

[0210]

[0211]

[0212]

[0213] Aspheric surface data

[0214] Surface 2

[0215] K=0.00000e+00A 4=5.82869e-08A 6=3.28093e-10A 8=-7.30293e-12A10=1.73470e-14

[0216] Surface 21

[0217] K=0.00000e+00A4=2.29294e-06A 6=-2.98460e-09A8=1.20199e-10A10=-4.29392e-13A12=2.82932e-16

[0218] Surface 22

[0219] K=0.00000e+00A4=1.40841e-05A 6=-8.55175e-09A8=1.99012e-10A10=-6.29223e-13A12=4.48042e-16

[0220] Various data

[0221]

[0222]

[0223] Lens unit data

[0224]

[0225]

[0226] Sixth numerical example Measurement unit mm Surface data

[0227]

[0228] Aspheric surface data

[0229] Surface 2

[0230] K=0.00000e+00A4=-2.77516e-07A6=-1.54577e-09A8=6.44179e-13A10=7.64354e-16

[0231] Surface 21

[0232] K=0.00000e+00A4=1.80120e-06A 6=-4.51707e-09A8=9.41454e-11A10=-3.12742e-13A12=1.29042e-16

[0233] Surface 22

[0234] K=0.00000e+00A4=1.25407e-05A 6=-9.09304e-09A8=1.59275e-10A10=-4.78303e-13A12=2.76852e-16

[0235] Various data

[0236]

[0237]

[0238]

[0239] Lens unit data

[0240] 7. Numerical example Measurement unit: mm Surface data

[0241]

[0242] Aspheric surface data

[0243] Surface 2

[0244] K=0.00000e+00A4=3.61761e-07A 6=-6.66364e-10A8=3.81905e-12A10=-2.19217e-15

[0245] Surface 21

[0246] K=0.00000e+00A4=2.67559e-06A 6=-2.93730e-09A8=6.58324e-11A10=-1.79203e-13A12=-8.74999e-18

[0247] Surface 22

[0248] K=0.00000e+00A4=1.30939e-05A 6=-7.05155e-09A8=1.25332e-10A10=-3.09303e-13A12=8.07445e-17

[0249] Various data

[0250]

[0251]

[0252]

[0253] Lens unit data

[0254]

[0255] Table 1 shows various values ​​of each numerical example.

[0256] Table 1

[0257]

[0258]

[0259] Imaging device

[0260] Will refer to Fig.16 An embodiment of a digital still camera (imaging device) including an optical system according to the present invention as an imaging optical system is described. Fig.16, the imaging optical system 11 is composed of the optical system according to any one of the first to seventh embodiments. An imaging device (photoelectric converter) 12 such as a CCD sensor or a CMOS sensor is disposed in the camera body 10. The imaging device 12 receives an optical image formed by the imaging optical system 11 and performs photoelectric conversion on the optical image. The camera body 10 may be a single-lens reflex camera including a quick-turn mirror or a mirrorless camera not including a quick-turn mirror.

[0261] Therefore, when the optical system L0 according to the present invention is applied to an imaging device such as a digital still camera, a high-resolution image with a wide viewing angle can be obtained.

[0262] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary 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, comprising: A first lens unit, a second lens unit having a negative refractive power, a third lens unit, and a fourth lens unit having a positive refractive power are arranged in order from the object side to the image side, wherein during focusing, the intervals between adjacent ones of the lens units change, wherein, during focusing from infinity to a close distance, the second lens unit moves toward the image side and the fourth lens unit moves toward the object side, and The first lens unit includes a negative meniscus lens and a positive lens, and the negative meniscus lens has a convex surface facing the object side.

2. The optical system according to claim 1, wherein: The following inequality is satisfied: -3.5 <M2 / M4<-0.5, Here, M2 and M4 are respectively the movement amount of the second lens unit and the movement amount of the fourth lens unit during focusing from infinity to an object distance at which the lateral magnification of the entire system is -0.1, and the sign of the movement amount toward the image side is positive.

3. The optical system according to claim 1, wherein: The following inequality is satisfied: -7.00 <f2 / f4<-2.50, Wherein f2 is the focal length of the second lens unit, and f4 is the focal length of the fourth lens unit.

4. The optical system according to claim 1, wherein: The following inequality is satisfied: 0.05<|f1 / f2|<0.50, Wherein f1 is the focal length of the first lens unit, and f2 is the focal length of the second lens unit.

5. The optical system according to claim 1, wherein: The following inequality is satisfied: 2.0<|fR / f|<500.0, Wherein fR is the focal length of the lens unit closest to the image side among the lens units in the optical system, and f is the focal length of the entire system.

6. The optical system according to claim 1, wherein: The following inequality is satisfied: 0.30 <BF / f<1.50, Where BF is the back focal length when the optical system is focused at infinity, and f is the focal length of the entire system.

7. The optical system according to claim 1, further comprising: Aperture diaphragm, Among them, the following inequality is satisfied: 0.45 <Da / TL<0.70, Where Da is the distance from the aperture stop to the image plane along the optical axis when the optical system is focused at infinity, and TL is the total lens length of the optical system.

8. The optical system according to claim 7, wherein: The aperture stop is closer to the image side than a surface of the second lens unit closest to the image side.

9. The optical system according to claim 7, wherein: The following inequality is satisfied: 0.15 <D4 / Da<0.35, Wherein D4 is the distance from the aperture stop to the surface of the fourth lens unit closest to the object side along the optical axis.

10. The optical system according to claim 1, wherein: The following inequality is satisfied: 0.70<(1-β4 2 )×βR 2 <3.00， wherein β4 is the lateral power of the fourth lens unit when the optical system is focused at infinity, and βR is the combined lateral power of all lens units disposed closer to the image side than the fourth lens unit when the optical system is focused at infinity.

11. The optical system according to claim 1, wherein: The following inequality is satisfied: 70.0<ν4p<96.0, Wherein ν4p is the Abbe number of at least one positive lens included in the fourth lens unit.

12. The optical system according to claim 1, wherein: During image blur correction, the whole or a part of the lens element included in the third lens unit moves in a direction including a component perpendicular to the optical axis.

13. The optical system according to claim 1, wherein: The optical system includes the first lens unit having positive refractive power, the second lens unit, the third lens unit having positive refractive power, the fourth lens unit, and a fifth lens unit having negative refractive power, which are arranged in order from the object side to the image side.

14. The optical system according to claim 1, wherein: The optical system includes the first lens unit having negative refractive power, the second lens unit, the third lens unit having positive refractive power, the fourth lens unit, and a fifth lens unit having negative refractive power, which are arranged in order from the object side to the image side.

15. The optical system of claim 1, wherein: The optical system includes the first lens unit having positive refractive power, the second lens unit, the third lens unit having positive refractive power, the fourth lens unit, the fifth lens unit having negative refractive power, and the sixth lens unit having negative refractive power, which are arranged in sequence from the object side to the image side.

16. The optical system of claim 1, wherein: The optical system includes the first lens unit having positive refractive power, the second lens unit, the third lens unit having positive refractive power, the fourth lens unit, the fifth lens unit having negative refractive power, and the sixth lens unit having positive refractive power, which are arranged in sequence from the object side to the image side.

17. The optical system of claim 1, wherein: The optical system includes the first lens unit having positive refractive power, the second lens unit, the third lens unit having positive refractive power, the fourth lens unit, and a fifth lens unit having positive refractive power, which are arranged in order from the object side to the image side.

18. The optical system of claim 1, wherein: The following inequality is satisfied: -10.0 <f2 / f<-3.6, Where f2 is the focal length of the second lens unit and f is the focal length of the entire system.

19. An imaging device comprising: An optical system according to any one of claims 1 to 18; as well as An imaging device receives an image formed by the optical system.

Images