Optical system and imaging device having the same

Abstract

To provide an optical system having high optical performance while having a large aperture ratio and capable of high-speed focusing.SOLUTION: An optical system includes, in order from an object side to an image side, a front group having a positive refractive power, an image-side focusing group having a positive refractive power, and a rear group. In focusing from infinity to a close distance, the image side focusing group moves with respect to the image plane so that a distance between the front group and the image side focusing group and a distance between the image side focusing group and the rear group change, and in focusing from infinity to a close distance, the rear group is immovable with respect to the image plane, an aperture stop that determines an on-axis light beam is disposed inside the front group or adjacent to an image side of the front group, and the front group has a positive lens Gp, when the Abbe number of the material of the positive lens Gp is νdp, the partial dispersion ratio is θgFp, and the anomalous partial dispersibility is ΔθgFp, predetermined conditional expressions are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system and an imaging device having the same, and is suitable for imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and in-vehicle cameras. [Background technology]

[0002] In recent years, there has been a demand for high-quality optical systems that are compact yet effectively correct various aberrations in imaging devices such as digital still cameras and video cameras using solid-state image sensors. Patent Document 1 discloses an optical system consisting of a first lens group, a second lens group, and a third lens group arranged sequentially from the object side to the image side, wherein the second lens group moves relative to the image plane during focusing, and an aperture diaphragm is positioned on the second lens group. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-152773 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in the optical system disclosed in Patent Document 1, the mass of the second lens group that moves during focusing is large, making high-speed focusing difficult. Furthermore, there is a risk of a decrease in optical performance during focusing. [Means for solving the problem]

[0005] An optical system as one aspect of the present invention comprises a front group having positive refractive power, an image-side focusing group having positive refractive power, and a rear group, arranged in order from the object side to the image side, wherein, when focusing from infinity to the closest distance, the image-side focusing group moves relative to the image plane so that the distance between the front group and the image-side focusing group and the distance between the image-side focusing group and the rear group changes, and when focusing from infinity to the closest distance, the rear group remains stationary relative to the image plane, and the aperture diaphragm that determines the on-axial light beam is arranged inside the front group or adjacent to the image side of the front group, the front group has a positive lens Gp, and when the Abbe number of the material of the positive lens Gp is ​​νdp, the partial dispersion ratio is θgFp, and the anomalous partial dispersion is ΔθgFp, the following conditional equation is satisfied. 0.050 < ΔθgFp < 0.250 however, ΔθgFp = θgFp - (B3 × νdp 3 +B2×νdp 2 (+B1×νdp+B0) B3 = -1.665 × 10 -7 B2 = 5.213 × 10 -5 B1 = -5.656 × 10 -3 B0 = 7.278 × 10 -1 This is how it is expressed.

[0006] Furthermore, as another aspect of the present invention, the optical system comprises a front group having positive refractive power, an image-side focusing group having positive refractive power, and a rear group, arranged in order from the object side to the image side, wherein, when focusing from infinity to the closest distance, the image-side focusing group moves relative to the image plane such that the distance between the front group and the image-side focusing group and the distance between the image-side focusing group and the rear group changes, and the image-side focusing group has at least two negative lenses. [Effects of the Invention]

[0007] This system provides an optical system that offers high optical performance while maintaining a large aperture ratio, enabling high-speed focusing. [Brief explanation of the drawing]

[0008] [Figure 1] Cross-sectional view of the optical system of Example 1 at infinite focus [Figure 2] Longitudinal aberration diagrams of the optical system of Example 1 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1 [Figure 3] Cross-sectional view of the optical system of Example 2 at infinite focus [Figure 4] Longitudinal aberration diagrams of the optical system of Example 2 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1 [Figure 5] Cross-sectional view of the optical system of Example 3 at infinite focus [Figure 6] Longitudinal aberration diagrams of the optical system of Example 3 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1 [Figure 7] Cross-sectional view of the optical system of Example 4 at infinite focus [Figure 8] Longitudinal aberration diagrams of the optical system of Example 4 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1 [Figure 9] Cross-sectional view of the optical system of Example 5 at infinite focus [Figure 10] Longitudinal aberration diagrams of the optical system of Example 5 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1 [Figure 11] Cross-sectional view of the optical system of Example 6 at infinite focus [Figure 12] Longitudinal aberration diagrams of the optical system of Example 6 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1<好 [Figure 13] Cross-sectional view of the optical system of Example 7 at infinite focus [Figure 14] Longitudinal aberration diagrams of the optical system of Example 7 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1 [Figure 15] Cross-sectional view of the optical system of Example 8 at infinite focus [Figure 16] Longitudinal aberration diagrams of the optical system of Example 8 at focus for (A) infinity and (B) a distance with a transverse magnification of -0.1 [Figure 17] Schematic diagram of the imaging device [Figure 18] Schematic diagram of the lens device [Modes for carrying out the invention]

[0009] Embodiments disclosed herein will be described in detail below with reference to the drawings. Note that the drawings may be drawn to a different scale than the actual dimensions for convenience. Furthermore, the same reference numeral is used for identical components in each drawing, and redundant descriptions are omitted.

[0010] Figures 1, 3, 5, 7, 9, 11, 13, and 15 are cross-sectional views of the optical systems of Examples 1 to 8 when they are focused at infinity.

[0011] In each cross-sectional view, the left side is the object side and the right side is the image side. The optical systems of each embodiment are suitable for imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and in-vehicle cameras. Furthermore, the optical systems of each embodiment may also be used as projection lenses for projectors, in which case the left side is the screen side and the right side is the projected image side.

[0012] In each cross-sectional view, L0 represents the entire optical system, and lens group Li represents the i-th lens group (where i is a natural number) from the object side, among the lens groups that move or are fixed together with respect to the image plane during focusing. That is, the air gap between adjacent lens groups changes during focusing, while the air gap between lenses within each lens group does not change during focusing. Furthermore, each lens group may consist of one lens or multiple lenses.

[0013] In this disclosure, "the interior of the lens group" refers to the space between the lens positioned closest to the object and the lens positioned closest to the image, among the lenses constituting the lens group.

[0014] Furthermore, in optical system L0, LFR represents the image-side focusing group, which is the lens group that moves closest to the image when focusing from infinity to the closest distance. LF represents the front group, which is the group of lenses positioned closer to the object than the image-side focusing group LFR. LR represents the rear group, which is the group of lenses positioned closer to the image than the image-side focusing group LFR.

[0015] Furthermore, at least some of the lenses included in the front LF group may move along the optical axis during focusing as the front focusing group.

[0016] Furthermore, Gk represents the k-th lens (where k is a natural number) from the object side among the lenses included in the optical system L0. Additionally, the lens surface of each lens may have a metasurface.

[0017] The arrows parallel to the optical axis shown in each cross-sectional view represent the direction of movement of the lens group during focusing from infinity to near. In each embodiment, during focusing from infinity to near, the LFR (Low Frame Lens), which will be described later, moves from the image side to the object side.

[0018] In each cross-sectional view, SP is the aperture diaphragm that determines the light beam at the open F-number. IP is the image plane, and when the optical system of each embodiment is used as the photographic optical system of a digital still camera or digital video camera, the image plane of a solid-state image sensor such as a CCD sensor or CMOS sensor or a photoelectric conversion element is located there. Note that the optical system of each embodiment may also be used as the photographic optical system of a silver halide film camera, in which case a photosensitive surface corresponding to the film plane is located on the image plane IP.

[0019] Figures 2, 4, 6, 8, 10, 12, 14, and 16 show the aberration diagrams when the optical system L0 of Examples 1 to 8 is focused at (A) infinity and (B) a distance where the lateral magnification is -0.1, respectively.

[0020] In the spherical aberration diagram, Fno is the F-number, the solid line represents the amount of spherical aberration relative to the d-line (wavelength 587.6 nm), and the dashed line represents the amount of spherical aberration relative to the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S represents the amount of aberration at the sagittal image plane, and the dashed line M represents the amount of aberration at the meridional image plane. In the distortion diagram, the solid line represents the amount of distortion relative to the d-line. In the chromatic aberration diagram, the dashed line represents the amount of lateral chromatic aberration at the g-line. Also, ω is the half-angle of view (°).

[0021] Next, we will describe the characteristic configurations of the optical systems in each embodiment.

[0022] The optical system L0 of each embodiment consists of a front group LF having positive refractive power, an image-side focusing group LFR having positive refractive power, and a rear group LR, arranged in order from the object side to the image side. When focusing from infinity to the near distance, the image-side focusing group LFR moves relative to the image plane so that the distance between the front group LF and the image-side focusing group LFR, and the distance between the image-side focusing group LFR and the rear group LR, change.

[0023] The optical system L0 is configured such that the light beam, focused by the front group LF which has positive refractive power, is incident on the image-side focusing group LFR which also has positive refractive power. This reduces the lens diameter of the image-side focusing group LFR, which moves relative to the image plane during focusing, and makes the image-side focusing group LFR lighter, thus enabling high-speed focusing.

[0024] Furthermore, by positioning the rear group LR far from the aperture diaphragm SP and at a location where the on-axial beam and peripheral beam are sufficiently separated in the direction perpendicular to the optical axis, astigmatism and distortion can be effectively corrected, improving the peripheral performance of the optical system L0.

[0025] Next, we will describe the configurations that are preferable to satisfy in the optical system L0 of each embodiment.

[0026] In the optical system L0 of each embodiment, it is preferable to position the aperture diaphragm SP inside the front group LF or adjacent to the image side. This reduces the height of off-axis rays incident on the image-side focusing group LFR, and thus reduces the lens diameter of the image-side focusing group LFR. Furthermore, by making the aperture diaphragm SP immobile during focusing, it becomes unnecessary to move the mechanical components constituting the aperture diaphragm SP during focusing. This makes the image-side focusing group LFR lighter, which is preferable because it enables high-speed focusing.

[0027] In the optical system L0 of each embodiment, it is preferable that the front group LF has at least two negative lenses. In wide-angle lenses, a strong negative refractive force is required on the object side of the optical system L0 in order to ensure sufficient back focus. By sharing this strong negative refractive force with at least two negative lenses, the refractive force per negative lens can be reduced, thereby suppressing the occurrence of distortion and field curvature.

[0028] In the optical system L0 of each embodiment, it is preferable that the image-side focusing group LFR has at least two positive lenses and at least one negative lens. To reduce the amount of movement of the image-side focusing group LFR when focusing from infinity to close distance, it is necessary to increase the refractive power of the image-side focusing group LFR. By sharing this strong refractive power among at least two positive lenses, the refractive power per positive lens can be reduced, thereby reducing fluctuations in spherical aberration and field curvature during focusing. In addition, by having at least one negative lens, fluctuations in axial chromatic aberration that occur during focusing can be suppressed.

[0029] In the optical system L0 of each embodiment, it is preferable that the object-side lens surface of the lens positioned closest to the object in the image-side focusing group LFR is concave toward the object. This causes the off-axis light beam that has passed through the aperture diaphragm SP to be incident approximately concentrically on the object-side surface of the image-side focusing group LFR, reducing the refraction of light rays at that surface. This suppresses variations in astigmatism, coma aberration, and angle of view during focusing.

[0030] In the optical system L0 of each embodiment, it is preferable that the image-side lens surface of the lens positioned closest to the image in the image-side focusing group LFR is convex toward the image side. This causes the off-axis light beam emitted from the image-side focusing group LFR to be emitted approximately concentrically toward the closest surface of the image-side focusing group LFR, thereby reducing the refraction of light rays at that surface. This makes it easier to suppress variations in astigmatism, coma aberration, and angle of view during focusing.

[0031] In the optical system L0 of each embodiment, it is preferable to place the negative lens on the image side of the rear group LR, i.e., on the image side of the optical system L0. This allows for a larger angle of the off-axis rays incident on the image plane from the optical axis, thereby reducing the lens diameter of the rear group LR. Furthermore, by placing the negative lens at a position where the height of the off-axis rays on the image side is high, the positive Petzval sum of the entire optical system L0 can be reduced without worsening sagittal flare, thus effectively correcting field curvature.

[0032] In the optical system L0 of each embodiment, it is preferable that the positive lens Gp is ​​arranged as a three-element cemented lens Gcomp consisting of a positive lens, a positive lens Gp, and a negative lens, or a negative lens, a positive lens Gp, and a positive lens, in that order from the object side. This enhances the correction effect of axial chromatic aberration.

[0033] Also, in the optical system L0 of each embodiment, by joining the lens surfaces on the object side and the image side of the positive lens Gp to other lenses respectively, when the positive lens Gp is made of a resin material, the degree of moisture absorption of the positive lens Gp can be reduced. Thereby, since the deformation of the positive lens Gp and the lenses joined thereto can be reduced, changes such as spherical aberration can be suppressed even in a high-humidity environment.

[0034] Next, the preferable conditions satisfied by the optical system L0 of each embodiment will be described.

[0035] The optical system L0 of each embodiment preferably satisfies one or more of the following conditional expressions (1) to (18). In each conditional expression, various numerical values are represented as follows.

[0036] Let the Abbe number of the material of the positive lens Gp included in the front group LF be νdp, the partial dispersion ratio be θgFp, and the anomalous partial dispersibility be ΔθgFp. However, various numerical values are represented as follows. ΔθgFp = θgFp-(B3×νdp 3 +B2×νdp 2 +B1×νdp + B0) B3 = -1.665×10 -7 B2 = 5.213×10 -5 B1 = -5.656×10 -3 B0 = 7.278×10 -1

[0037] Let the back focus in terms of air of the optical system L0 when focused at infinity be sk.

[0038] Let the focal length of the entire optical system L0 be f.

[0039] Let the focal length of the front group LF be fLF, the focal length of the image-side focusing group LFR be fLFR, and the focal length of the rear group LR be fLR.

[0040] Let RLFR1 be the radius of curvature of the lens surface closest to the object in the image-side focusing group LFR, and RLFR2 be the radius of curvature of the lens surface closest to the image.

[0041] Let Ndn be the refractive index of the negative lens Gn material of the optical system L0 with respect to the d line.

[0042] The anomalous partial dispersion ΔθgFn of the negative lens Gn material in the optical system L0 is expressed using the Abbe number νdn and the partial dispersion ratios for the g-line and F-line as θgFn. ΔθgFn=θgFn-(-0.0025116×νdn+0.67449) Let's assume that.

[0043] When focused at infinity, the lateral magnification of the image-side focusing group LFR is denoted as βLFR, and the lateral magnification of the rear group LR is denoted as βLR.

[0044] Let ΣDair be the sum of the air gaps along the optical axis from the object-side surface to the image-side surface of the optical system L0.

[0045] Let L be the total optical length of the optical system L0. The total optical length is the distance from the first lens surface to the final lens surface plus the back focus in air equivalent.

[0046] Let νd1n be the Abbe number of the material of the negative lens G1n in the front group LF.

[0047] Let νd2p be the Abbe number of the material of the positive lens G2p in the image-side focusing group LFR.

[0048] The amount of movement of the LFR of the image-side focusing group when focusing from infinity to an object distance where the lateral magnification of the entire system becomes -0.1 times is defined as MLFR.

[0049] When the optical system L0 is focused at infinity, the distance along the optical axis from the aperture diaphragm SP to the image plane is defined as DSP.

[0050] Let fGcomp be the focal length of the cemented lens Gcomp, which includes the positive lens Gp, in the front group LF.

[0051] 0.050 < ΔθgFp < 0.250 ···(1) 0.10 <sk / f<1.80 ···(2) 0.30 <fLF / fLFR<3.00 ···(3) -1.50 <f / fLR<1.50 ···(4) -1.50<(RLFR2-RLFR1) / (RLFR2+RLFR1)<1.50...(5) -0.015<ΔθgFn<0.015 (6) -0.200 <Ndn-(-1.454×10 -2 ×νdn+2.287)<0.05···(7) 0.50<(1-βLFR 2 )×βLR 2 <2.50 ···(8) 0.00 <sk / |fLR|<0.80 ···(9) 0.20<ΣDair / (L-sk)<0.70 ···(10) 1.50 <L / f<15.00 ···(11) 60.00 < νd2p < 100.00 ···(12) -0.200 <MLFR / DSP<-0.005 ···(13) 60.00 < νd1n < 100.00 ···(14) 0.50 <fLFR / f<3.00 ···(15) 0.30<(DSP+sk) / L<0.80 (16) 0.50 <fLF / f<5.00 ···(17) 0.00 <f / fGcomp<2.00 ···(18)

[0052] Next, we will explain the technical meaning of the aforementioned conditional expressions (1) through (18).

[0053] Condition (1) defines the anomalous partial dispersion ΔθgFp of the positive lens Gp placed in the front group LF.

[0054] Large-aperture lenses often suffer from axial chromatic aberration in the short-wavelength range, such as the g-line. In particular, applying first-order achromatic correction to the C-line and F-line tends to result in excessive axial chromatic aberration in the g-line. Therefore, by using a material with a large ΔθgFp for the positive lens, the excessive axial chromatic aberration in the short-wavelength range, such as the g-line, can be selectively focused, thereby effectively correcting axial chromatic aberration.

[0055] If ΔθgFp falls below the lower limit of condition (1), it becomes difficult to correct axial chromatic aberration, which is undesirable.

[0056] If ΔθgFp becomes large enough to exceed the upper limit of condition (1), the correction of axial chromatic aberration becomes excessive, which is undesirable.

[0057] Condition (2) relates to the air-reduced back focus sk of the optical system L0. By satisfying condition (2), the rear group LR can be positioned at a location with a large off-axis ray height, thereby selectively correcting distortion and astigmatism while minimizing the impact on correcting spherical aberration and sagittal flare. This improves the peripheral performance of the optical system L0.

[0058] If the back focus sk becomes small below the lower limit of condition (2), it is undesirable because the optical system L0 and the components of the camera or other device to which the optical system L0 is attached will interfere, making it difficult to place lenses in the rear group LR.

[0059] If the back focus sk exceeds the upper limit of condition (2), it becomes difficult to correct distortion, field curvature, and astigmatism, which is undesirable.

[0060] Conditional equation (3) specifies the ratio of the refractive power of the front group LF to the image-side focusing group LFR.

[0061] If the fLFR becomes large below the lower limit of condition (3), the positive refractive power of the image-side focusing group LFR becomes too small. This increases the amount of movement of the lens group during focusing, which is undesirable because it increases the overall length of the optical system. Also, if the fLF becomes small, it becomes difficult to correct spherical aberration and axial chromatic aberration, which is undesirable.

[0062] If fLFR becomes too small, exceeding the upper limit of condition (3), the refractive power of the image-side focusing group LFR becomes too large, which is undesirable because it leads to excessive changes in performance such as spherical aberration, field curvature, and angle of view fluctuations during focusing. Also, if fLF becomes too large, the overall length of the optical system increases, which is undesirable.

[0063] Conditional equation (4) specifies the ratio of the focal length fLR of the rear group LR to the focal length f of the entire optical system L0. Near the lower limit of conditional equation (4), fLR takes a negative value. If the absolute value of fLR becomes small below the lower limit of conditional equation (4), the negative refractive power of the rear group LR becomes too large. In this case, the angle of incidence of the off-axis light beam incident on the image plane becomes too large, which is undesirable because it makes color unevenness more likely to occur when imaging with a solid-state image sensor such as a CMOS sensor.

[0064] Near the upper limit of condition (4), fLR takes a positive value. When the absolute value of fLR becomes small beyond the upper limit of condition (4), the positive refractive power of the rear group LR becomes too large. In this case, the positive Petzval sum for the entire optical system L0 becomes too large, making it difficult to correct for field curvature, which is undesirable.

[0065] Conditional equation (5) defines the shape of the LFR on the image side and relates to the conditions for suppressing aberrations and changes in the angle of view that occur during focusing.

[0066] When the value falls below the lower limit of condition (5), the absolute value of the radius of curvature of the concave surface closest to the object in the image-side focusing group LFR increases. In this case, the concentricity of the surface closest to the object in the image-side focusing group LFR decreases with respect to the off-axis light beam incident on the image-side focusing group LFR. Also, because the absolute value of the radius of curvature of the convex surface closest to the image in the image-side focusing group LFR decreases, the off-axis light beam is significantly refracted by the surface closest to the image in the image-side focusing group LFR. As a result, the fluctuation in the angle of view that occurs during focusing tends to increase, which is undesirable.

[0067] When the upper limit of condition (5) is exceeded, the absolute value of the radius of curvature of the object-side concave surface of the image-side focusing group LFR becomes smaller. At this time, the concentricity of the object-side surface of the image-side focusing group LFR with respect to the off-axis light beam incident on the image-side focusing group LFR becomes smaller. As a result, the fluctuation of the angle of view that occurs during focusing tends to become larger. Also, the absolute value of the radius of curvature of the image-side convex surface of the image-side focusing group LFR becomes larger. This is undesirable because it tends to increase aberration fluctuations such as coma aberration and astigmatism during focusing.

[0068] Conditional equation (6) defines the anomalous partial dispersion of the negative lens Gn possessed by at least one of the front group LF or the image-side focusing group LFR.

[0069] If the value falls below the lower limit of condition (6), the correction of axial chromatic aberration on the g line becomes excessive, which is undesirable.

[0070] If the upper limit of condition (6) is exceeded, the correction of axial chromatic aberration on the g line will be insufficient, which is undesirable.

[0071] Condition (7) specifies the dispersion of the negative lens Gn material in at least one of the front group LF or the image-side focusing group LFR.

[0072] If the value falls below the lower limit of condition (7), the Abbe number of the negative lens Gn becomes too large. This results in excessive correction of axial chromatic aberration, which is undesirable.

[0073] If the upper limit of condition (7) is exceeded, the Abbe number of the negative lens Gn becomes too small. This is undesirable because it results in insufficient correction of axial chromatic aberration. Also undesirable because the refractive power of the negative lens Gn becomes too large, making it difficult to correct spherical aberration.

[0074] Large-aperture lenses often suffer from axial chromatic aberration in the short-wavelength range, such as the g-line. In particular, when first-order achromatic aberration is applied to the C-line and F-line, the axial chromatic aberration of the g-line tends to become excessive. Therefore, by using a material that satisfies conditions (6) and (7) for the negative lens Gn, the degree of divergence of the g-line due to the negative lens can be relatively reduced, thereby suppressing excessive axial chromatic aberration in the short-wavelength range, such as the g-line.

[0075] By placing at least one negative lens Gn that satisfies both conditions (6) and (7) in at least one of the front group LF or the image-side focusing group LFR, the above-described effect of axial chromatic aberration correction can be obtained.

[0076] Furthermore, having at least one of the front group LF or the image-side focusing group LFR have two negative lenses Gn can enhance the effect of the axial chromatic aberration correction described above. Having three or more negative lenses Gn can further enhance the effect of the axial chromatic aberration correction described above.

[0077] Furthermore, it is more preferable to place at least one negative lens Gn in both the front group LF and the image-side focusing group LFR. By placing a negative lens Gn in the front group LF, axial chromatic aberration can be effectively corrected throughout the entire optical system L0. By placing a negative lens Gn in the image-side focusing group LFR, axial chromatic aberration correction within the image-side focusing group LFR is facilitated, and fluctuations in axial chromatic aberration during focusing can be suppressed.

[0078] Conditional equation (8) defines the positional sensitivity of the image-side focusing group LFR, that is, the ratio of the amount of movement of the image plane to the amount of movement of the image-side focusing group LFR during focusing.

[0079] If the value falls below the lower limit of condition (8), the positional sensitivity of the image-side focusing group LFR becomes too small. This is undesirable because it increases the focusing distance. Furthermore, it is undesirable because it becomes difficult to shorten the overall length of the optical system L0 in order to ensure sufficient focusing distance.

[0080] If the upper limit of condition (8) is exceeded, the refractive power of the LFR on the image side becomes too large, which is undesirable because it leads to excessive changes in performance such as spherical aberration, field curvature, and angle of view during focusing.

[0081] Conditional equation (9) defines the ratio of the focal length fLR of the rear group to the air-equivalent back focus sk.

[0082] When sk becomes small, falling below the lower limit of condition (9), the image plane of the optical system L0 is positioned closer to the object than the image-side lens plane among the lenses included in the rear group LR, or at the same position as the image-side lens plane. This makes imaging difficult and undesirable.

[0083] If sk becomes too large, exceeding the upper limit of condition (9), the absolute value of the refractive power of the rear group LR becomes too large. If the negative refractive power of the rear group LR becomes too large, the incident angle of the off-axis light beam incident on the image plane becomes too large, which is undesirable because it makes it easier for color unevenness to occur when imaging with an image sensor such as a CMOS sensor. If the positive refractive power of the rear group LR becomes too large, the positive Petzval sum of the entire optical system L0 becomes too large, which is undesirable because it makes it difficult to correct the curvature of the image field.

[0084] Conditional equation (10) defines the ratio of the total air gap ΣDair on the optical axis from the object-side surface to the image-side surface of the optical system L0 to the total optical length L of the optical system L0.

[0085] If ΣDair becomes small below the lower limit of condition (10), it becomes difficult to secure sufficient space for the lens group to move during focusing. Furthermore, in order to give the negative lens of the first lens group sufficient positive curvature, an air gap on the optical axis between adjacent lenses is necessary, but this becomes difficult, and as a result, it becomes difficult to widen the optical system L0 and correct distortion aberration, which is undesirable.

[0086] If ΣDair becomes larger than the upper limit of condition (10), the ratio of the air gap to the total optical length becomes too large, making it difficult to provide each positive lens with sufficient refractive power, and thus difficult to correct spherical aberration and axial chromatic aberration, which is undesirable. Alternatively, if one attempts to provide each positive lens with sufficient refractive power, the total length becomes larger, which is also undesirable.

[0087] Conditional equation (11) defines the ratio of the total optical length L of the optical system L0 to the focal length f of the entire optical system L0.

[0088] If L becomes small below the lower limit of condition (11), the refractive power of each lens group becomes too large, making it difficult to correct aberrations such as distortion, astigmatism, and spherical aberration, which is undesirable.

[0089] If L becomes larger than the upper limit of condition (11), the overall length of the lens device L0 increases, which is undesirable.

[0090] Conditional equation (12) is an equation that specifies the Abbe number νd2p of the material of at least one positive lens G2p in the image-side focusing group LFR, and specifies the conditions for good correction of axial chromatic aberration.

[0091] If νd2p becomes small below the lower limit of condition equation (12), it becomes difficult to correct axial chromatic aberration, which is undesirable.

[0092] If νd2p becomes large enough to exceed the upper limit of condition (12), the correction of chromatic aberration becomes excessive, which is undesirable.

[0093] Furthermore, it is preferable to arrange two or more positive lenses G2p that satisfy condition (12) in the image-side focusing group LFR, as this can enhance the effects described above.

[0094] Conditional equation (13) defines the ratio of the amount of movement MLFR when focusing from infinity to an object distance where the lateral magnification of the entire system is -0.1x, to the distance DSP on the optical axis from the aperture diaphragm SP to the image-side plane. Note that the sign of the amount of movement MLFR is considered positive when moving from the object side to the image side.

[0095] If the value falls below the lower limit of condition (13), the refractive power of the image-side focusing group LFR becomes too large, which is undesirable because it increases the fluctuations in spherical aberration and field curvature during focusing.

[0096] If the MLFR exceeds the upper limit of condition (13), the amount of movement of the image-side focusing group LFR increases, and the overall length increases in order to secure space for that movement, which is undesirable.

[0097] Conditional equation (14) defines the Abbe number νd1n of the material of the negative lens G1n in the front group LF, and specifies the conditions for good correction of chromatic aberration.

[0098] If νd1n becomes small below the lower limit of condition equation (14), it becomes difficult to correct chromatic aberration, which is undesirable.

[0099] If νd1n becomes larger than the upper limit of condition equation (14), it is undesirable because it can lead to excessive correction of chromatic aberration, excessive wear of the negative lens Gn1 making processing difficult, and increased susceptibility to cracking.

[0100] Furthermore, it is even more preferable to place two or more negative lenses G1n that satisfy condition (14) in the front LF group, as this can enhance the effects described above.

[0101] Condition (15) relates to the refractive power of the LFR of the image-side focusing group. By satisfying condition (15), the focal length fLFR of the LFR of the image-side focusing group becomes smaller, allowing the object distance that can be focused by focusing to be brought closer to the image plane. In addition, the overall length of the optical system can be shortened while suppressing changes in optical performance during focusing.

[0102] If the focal length fLFR of the positive image-side focusing group LFR falls below the lower limit of condition (15), the refractive power of the image-side focusing group LFR becomes too large. This is undesirable because it results in large changes in performance such as spherical aberration, field curvature, and angle of view fluctuations that occur during focusing.

[0103] If the focal length fLFR of the positive image-side focusing group LFR exceeds the upper limit of condition (15), the positional sensitivity of the image-side focusing group LFR, i.e., the ratio of the movement of the image plane to the movement of the focusing group, becomes too small. As a result, the object distance that can be focused by focusing moves further away from the image plane, which is undesirable. Furthermore, the overall length of the optical system L0 increases in order to ensure sufficient air distance for focusing, which is also undesirable.

[0104] Furthermore, by using a negative lens Gn that satisfies conditions (6) and (7) as the negative lens constituting the three-element cemented lens, axial chromatic aberration can be effectively corrected.

[0105] Furthermore, it is preferable that the three-element cemented lens be positioned adjacent to the object-side or image-side of the aperture diaphragm SP located in the front group LF. This positions the three-element cemented lens at a location with a large axial ray height, thereby enhancing the effect of axial chromatic aberration correction.

[0106] Furthermore, it is preferable to position the three-element cemented lens and aperture diaphragm SP in the front group LF, which remains stationary during focusing. As mentioned above, it is preferable to position the three-element cemented lens before and after the aperture diaphragm SP, but the axial light beam diameter is large before and after the aperture diaphragm SP, resulting in larger lens diameters and greater weight. Therefore, it is preferable to configure the three-element cemented lens, including the aperture diaphragm SP and the positive lens Gp, to remain stationary during focusing.

[0107] Conditional equation (16) is an equation that specifies the position DSP of the aperture diaphragm SP, and defines the conditions for constructing a compact optical system L0.

[0108] If the DSP becomes small below the lower limit of condition (16), the lens diameter of the lens positioned on the object side of the aperture diaphragm SP increases, which is undesirable because it increases the overall mass and diameter of the optical system L0. Also, the angle of the off-axis light beam incident on the image plane becomes too large, which is undesirable because it makes color unevenness more likely to occur when imaging with a solid-state image sensor such as a CMOS sensor.

[0109] If the DSP becomes larger than the upper limit of condition (16), the lens diameter of the lens positioned on the image side of the aperture diaphragm SP becomes larger, which is undesirable because it increases the overall mass and diameter of the optical system L0.

[0110] Conditional equation (17) specifies the focal length fLF of the front group LF.

[0111] If the fLF becomes small below the lower limit of condition equation (17), the positive refractive power of the front group LF becomes too large, making it difficult to correct spherical aberration and distortion, which is undesirable.

[0112] When fLF exceeds the upper limit of condition (17), the lens diameter of the image-side focusing group LFR increases. This results in an increased mass of the image-side focusing group LFR, making high-speed focusing difficult, which is undesirable.

[0113] Conditional equation (18) defines the focal length fGcomp of the cemented lens Gcomp.

[0114] If fGcomp takes a negative value below the lower limit of condition equation (18), it is undesirable because it becomes difficult to correct axial chromatic aberration.

[0115] If fGcomp becomes smaller than the upper limit of condition (18), the refractive power of the cemented lens with positive Gcomp becomes too large, resulting in excessive correction of axial chromatic aberration, which is undesirable.

[0116] Furthermore, it is more preferable to use the numerical ranges of the following conditional expressions (1a) to (18) as the numerical ranges of the conditional expressions (1a) to (18a). 0.060 < ΔθgFp < 0.220 ···(1a) 0.20 <sk / f<1.60···(2a) 0.50 <fLF / fLFR<2.70···(3a) -1.20 <f / fLR<1.20···(4a) -1.20<(RLFR2-RLFR1) / (RLFR2+RLFR1)<1.20...(5a) -0.010<ΔθgFn<0.010 (6a) -0.180 <Ndn-(-1.454×10 -2 ×νdn+2.287)<0.030···(7a) 0.60<(1-βLFR 2 )×βLR 2 <2.20···(8a) 0.00 <sk / |fLR|<0.70···(9a) 0.25<ΣDair / (L-sk)<0.64 (10a) 2.00 <L / f<13.50···(11a) 62.00 < νd2p < 99.00 ... (12a) -0.160 <MLFR / DSP<-0.008···(13a) 62.00 < νd1n < 99.00 ... (14a) 0.70 <fLFR / f<2.80···(15a) 0.35<(DSP+sk) / L<0.74 (16a) 0.70 <fLF / f<4.50···(17a) 0.01 <f / fGcomp<1.80···(18a)

[0117] Furthermore, it is more preferable to use the numerical ranges of the following conditional expressions (1) to (18) as the numerical ranges of the conditional expressions (1b) to (18b). 0.070 < ΔθgFp < 0.190 ···(1b) 0.30 <sk / f<1.40···(2b) 0.70 <fLF / fLFR<2.30···(3b) -0.90 <f / fLR<0.50···(4b) -0.80<(RLFR2-RLFR1) / (RLFR2+RLFR1)<0.80...(5b) -0.008<ΔθgFn<0.007 (6b) -0.15 <Ndn-(-1.454×10 -2 ×νdn+2.287)<0.02···(7b) 0.55<(1-βLFR 2 )×βLR 2 <1.90···(8b) 0.00 <sk / |fLR|<0.60···(9b) 0.30<ΣDair / (L-sk)<0.59 (10b) 2.20 <L / f<12.00···(11b) 64.00 < νd2p < 98.00 ···(12b) -0.120 <MLFR / DSP<-0.012···(13b) 64.00 < νd1n < 98.00 ... (14b) 0.90 <fLFR / f<2.60···(15b) 0.40<(DSP+sk) / L<0.68 (16b) 1.00 <fLF / f<4.00···(17b) 0.02 <f / fGcomp<1.60···(18b)

[0118] Furthermore, it is more preferable to use the numerical ranges of the following conditional expressions (1) to (18) as the numerical ranges of the conditional expressions (1c) to (18c). 0.080 < ΔθgFp < 0.160 ···(1c) 0.38 <sk / f<1.20···(2c) 0.90 <fLF / fLFR<1.80···(3c) -0.70 <f / fLR<0.20···(4c) -0.50<(RLFR2-RLFR1) / (RLFR2+RLFR1)<0.50...(5c) -0.006<ΔθgFn<0.004 (6c) -0.13 <Ndn-(-0.0145425×νdn+2.28725)<0.01···(7c) 0.65<(1-βLFR 2 )×βLR 2 <1.60···(8c) 0.00 <sk / |fLR|<0.40···(9c) 0.33<ΣDair / (L-sk)<0.57 (10c) 2.60 <L / f<11.00···(11c) 66.00 < νd2p < 97.00 ···(12c) -0.080 <MLFR / DSP<-0.016···(13c) 66.00 < νd1n < 97.00 ···(14c) 1.00 <fLFR / f<2.40···(15c) 0.45<(DSP+sk) / L<0.65 (16c) 1.30 <fLF / f<3.50···(17c) 0.04 <f / fGcomp<1.40···(18c)

[0119] Furthermore, by setting the lower limit of condition (1) to 0.10, 0.12, 0, and 13, the effect of the lower limit of condition (1) can be further enhanced.

[0120] Furthermore, by setting the upper limit of condition (1) to 0.155, 0.15, and 0.145, the effect of the upper limit of condition (1) can be further enhanced.

[0121] Furthermore, by setting the lower limit of conditional expression (12) to 68.00, 70.00, 73.00, 75.00, and 80.00, the effect of the lower limit of conditional expression (12) can be further enhanced.

[0122] Furthermore, by setting the upper limit of conditional expression (18) to 1.20, 1.00, 0.80, 0.60, and 0.40, the effect of the upper limit of conditional expression (18) can be further enhanced.

[0123] Next, we will describe the detailed configuration of the optical system L0 in Examples 1 to 8. Note that for each example's optical system L0, we will omit the explanation of configurations similar to those of Example 1's optical system L0, and will mainly describe the differences from Example 1.

[0124] [Example 1] The optical system L0 of Example 1 consists of a first lens group L1 having positive refractive power, a second lens group L2 having positive refractive power, and a third lens group L3 having negative refractive power.

[0125] In the optical system L0 of Example 1, the front group LF, which has positive refractive power, corresponds to the first lens group L1, the image-side focusing group LFR, which also has positive refractive power, corresponds to the second lens group L2, and the rear group LR corresponds to the third lens group L3.

[0126] By making the rear group LR have a negative refractive power, it becomes easier to correct the positive Petzval sum, and image field curvature can be corrected effectively.

[0127] In the optical system L0 of Example 1, the front group LF consists of G1 to G12 lenses, the image-side focusing group LFR consists of G13 to G16 lenses, and the rear group consists of G17 and G18 lenses. The front group LF has seven negative lenses.

[0128] In the optical system L0 of Example 1, the aperture diaphragm SP is located inside the front group LF. Furthermore, by making the G1 and G3 lenses aspherical lenses, distortion and astigmatism can be effectively corrected.

[0129] In the optical system L0 of Example 1, the lens closest to the image in the image-side focusing group LFR is an aspherical lens. This allows for good correction of spherical aberration, field curvature, and astigmatism. Furthermore, by placing the aspherical lens closest to the image in the image-side focusing group LFR where the light beam is focused, the rate of performance degradation due to errors from the desired surface shape caused by manufacturing tolerances can be reduced.

[0130] In the optical system L0 of Example 1, lenses G6 and G7, lenses G10 to G12, lenses G13 and G14, and lenses G17 and G18 are each joined together to form a single cemented lens.

[0131] In the optical system L0 of Example 1, G11 is a positive lens Gp having positive anomalous partial dispersion, and is bonded between the positive lens G10 and the negative lens G12 to form a three-element cemented lens Gcomp. This allows for good correction of axial chromatic aberration in the short wavelength range, such as the g-line.

[0132] Furthermore, during focusing, the image-side focusing group LFR moves in the optical axis direction from the image side to the object side relative to the image plane, while the front group LF and rear group LR remain stationary relative to the image plane.

[0133] [Example 2] In the optical system L0 of Example 2, the front group LF consists of G1 to G10 lenses, the image-side focusing group LFR consists of G11 to G14 lenses, and the rear group consists of G15 and G16 lenses.

[0134] In the optical system L0 of Example 2, lenses G4 and G5, lenses G8 to G10, lenses G11 and G12, and lenses G15 and G16 are each joined together to form a single cemented lens. The front group LF has six negative lenses.

[0135] In the optical system L0 of Example 2, G9 is a positive lens Gp having positive anomalous partial dispersion, and is bonded between the positive lens G8 and the negative lens G10 to form a three-element cemented lens Gcomp. This allows for good correction of axial chromatic aberration in the short wavelength range, such as the g-line.

[0136] [Example 3] The optical system L0 of Example 3 consists of a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having positive refractive power, and a fifth lens group L5 having negative refractive power.

[0137] The front lens group LF, which has positive refractive power, consists of the first lens group L1, the second lens group L2, and the third lens group L3. The image-side focusing group LFR, which also has positive refractive power, corresponds to the fourth lens group L4, and the rear lens group LR corresponds to the fifth lens group L5.

[0138] In the optical system L0 of Example 3, the front group LF consists of G1 to G8 lenses, the image-side focusing group LFR consists of G9 to G12 lenses, and the rear group consists of G13 to G15 lenses. The front group LF has five negative lenses. The aperture diaphragm SP is located inside the front group LF.

[0139] In the optical system L0 of Example 3, lenses G3 and G4, lenses G7 to G9, lenses G10 and G11, and lenses G14 and G15 are each joined together to form a single cemented lens.

[0140] In the optical system L0 of Example 3, G8 is a positive lens Gp having positive anomalous partial dispersion, and is bonded between the positive lens G7 and the negative lens G9 to form a three-element cemented lens Gcomp. This allows for good correction of axial chromatic aberration in the short wavelength range, such as the g-line.

[0141] In the optical system L0 of Example 3, the second lens group L2 moves from the object side to the image side when focusing from infinity to the closest distance, and the fourth lens group L4 moves from the image side to the object side. During focusing, the movement of the second lens group L2 in addition to the fourth lens group L4, which is the image-side focusing group LFR, can suppress fluctuations in field curvature and breathing.

[0142] Alternatively, instead of the second lens group L2, any lens within the front group LF may be moved from the object side to the image side, or from the image side to the object side. For example, moving the G5 lens from the image side to the object side can suppress field curvature fluctuations during focusing.

[0143] Furthermore, when focusing from infinity to close range, the first lens group L1, the third lens group L3, and the fifth lens group L5 remain stationary relative to the image plane.

[0144] [Example 4] In the optical system L0 of Example 4, the front group LF consists of G1 to G11 lenses, the image-side focusing group LFR consists of G12 to G15 lenses, and the rear group consists of G16 and G17 lenses. The front group LF has seven negative lenses.

[0145] In the optical system L0 of Example 4, lenses G5 and G6, lenses G9 to G11, lenses G12 and G13, and lenses G16 and G17 are each joined to each other to form a single cemented lens.

[0146] In the optical system L0 of Example 4, G10 is a positive lens Gp having positive anomalous partial dispersion, and is bonded between the positive lens G9 and the negative lens G11 to form a three-element cemented lens Gcomp. This allows for good correction of axial chromatic aberration in the short wavelength range, such as the g-line.

[0147] [Example 5] In the optical system L0 of Example 5, the front group LF consists of G1 to G12 lenses, the image-side focusing group LFR consists of G13 to G16 lenses, and the rear group consists of G17 and G18 lenses. The front group LF has seven negative lenses. Furthermore, by making the G1 and G3 lenses aspherical lenses, distortion and astigmatism can be corrected effectively.

[0148] In the optical system L0 of Example 5, lenses G6 and G7, lenses G10 to G12, lenses G13 and G14, and lenses G17 and G18 are joined together to form a single cemented lens.

[0149] [Example 6] The optical system L0 of Example 6 consists of a first lens group L1 having positive refractive power, a second lens group L2 having positive refractive power, and a third lens group L3 having positive refractive power.

[0150] The front group LF, which has positive refractive power, corresponds to the first lens group L1; the image-side focusing group LFR, which also has positive refractive power, corresponds to the second lens group L2; and the rear group LR corresponds to the third lens group L3.

[0151] The optical system L0 of Example 6 consists of a front group LF with positive refractive power, an image-side focusing group LFR with positive refractive power, and a rear group LR with positive refractive power. By making the rear group LR have positive refractive power, the incident angle of the off-axis light beam incident on the image plane can be reduced, making it easier to suppress color unevenness when imaging with a solid-state image sensor such as a CMOS sensor.

[0152] In the optical system L0 of Example 6, the front group LF consists of G1 to G10 lenses, the image-side focusing group LFR consists of G11 to G14 lenses, and the rear group consists of G15 and G16 lenses. The front group LF has six negative lenses. Furthermore, by making the G1 and G3 lenses aspherical lenses, distortion and astigmatism can be corrected effectively.

[0153] In the optical system L0 of Example 6, lenses G4 and G5, lenses G8 to G10, lenses G11 and G12, and lenses G15 and G16 are joined together to form a single cemented lens.

[0154] In the optical system L0 of Example 6, G9 is a positive lens Gp having positive anomalous partial dispersion, and is bonded between the positive lens G8 and the negative lens G10 to form a three-element cemented lens Gcomp. This allows for good correction of axial chromatic aberration in the short wavelength range, such as the g-line.

[0155] [Example 7] In the optical system L0 of Example 7, the front group LF consists of G1 to G8 lenses, the image-side focusing group LFR consists of G9 to G12 lenses, and the rear group consists of G13 and G14 lenses. Furthermore, by making the G14 lens closest to the image a spherical lens, distortion and astigmatism can be corrected effectively.

[0156] Furthermore, by constructing the G12 lens from plastic resin, the image-side focusing group LFR can be made lighter, enabling faster focusing.

[0157] In the optical system L0 of Example 7, lenses G5 to G7, lenses G9 and G10, and lenses G13 and G14 are joined together to form a single cemented lens.

[0158] In the optical system L0 of Example 7, the G8 lens included in the front group LF moves to include a component perpendicular to the optical axis. This allows for image blur correction and suppresses fluctuations in coma aberration and uneven focus during image blur correction.

[0159] In the optical system L0 of each embodiment, it is preferable to place the negative lens on the image side of the rear group LR, i.e., on the image side of the optical system L0. This allows for a larger angle of the off-axis rays incident on the image plane from the optical axis, thereby reducing the lens diameter of the rear group LR. Furthermore, by placing the negative lens at a position where the height of the off-axis rays on the image side is high, the positive Petzval sum of the entire optical system L0 can be reduced without worsening sagittal flare, and image field curvature can be corrected effectively.

[0160] [Example 8] In the optical system L0 of Example 8, the front group LF consists of G1 to G8 lenses, the image-side focusing group LFR consists of G9 to G11 lenses, and the rear group consists of G12 and G13 lenses. The front group LF has four negative lenses.

[0161] In the optical system L0 of Example 8, G7 is a positive lens Gp having positive anomalous partial dispersion, and is bonded between the positive lens G6 and the negative lens G8 to form a three-element cemented lens Gcomp. This allows for good correction of axial chromatic aberration in the short wavelength range, such as the g-line.

[0162] Furthermore, in the optical system L0 of Example 8, the aperture diaphragm SP is positioned adjacent to the image side of the front group LF. This allows for a smaller aperture diameter for the aperture diaphragm SP.

[0163] Next, we will describe the preferred configurations that the optical system L0 of each embodiment should satisfy.

[0164] In the optical system L0 of each embodiment, it is preferable that at least one of the air lenses, from the first to the third air lens in order from the object side, be biconvex. This allows a lens with a strong negative refractive power to be placed at a position away from the aperture diaphragm SP, thereby suppressing sagittal flare caused by the strong negative refractive power while reducing the positive Petzval sum, and thus effectively correcting field curvature.

[0165] In the optical system L0 of each embodiment, it is preferable that the front group LF has, in order from the object side, a negative lens G1, a negative lens G2, a negative lens G3, and a positive lens G4. By making lens G4 a positive lens, barrel distortion and chromatic aberration generated by lenses G1 to G3 can be effectively corrected.

[0166] In the optical system L0 of Examples 1, 2, 4, 5, and 6, it is preferable that the front group LF has two negative meniscus lenses arranged consecutively on the object side, with the object-side lens surface being convex toward the object. This allows for good correction of distortion, field curvature, and astigmatism.

[0167] In Examples 1, 2, 4, 5, and 6, it is preferable that the front group LF has three negative lenses arranged continuously in the optical axis direction on the object side. In wide-angle lenses, a strong negative refractive force is required on the object side of the optical system L0 in order to ensure sufficient back focus. By sharing this negative refractive force among three negative lenses, the refractive force per negative lens can be reduced, thereby suppressing barrel distortion and field curvature. In this disclosure, three continuously arranged negative lenses mean that no positive lenses are arranged between the three negative lenses.

[0168] In the optical system L0 of Examples 1, 2, 4, 5, and 6, it is preferable that at least one of the three negative lenses arranged continuously on the object side of the front group LF be an aspherical lens. This allows for good correction of distortion and astigmatism. Furthermore, in Examples 1 and 5, the above effect is enhanced by making both the G1 lens and the G3 lens as aspherical lenses. In addition, by shaping the aspherical lens such that the absolute value of curvature at the periphery is smaller than the absolute value of curvature along the optical axis, distortion can be well corrected.

[0169] In the optical system L0 of Examples 1 and 5, the G4 lens is preferably a meniscus lens with positive refractive power. This allows for correction of barrel distortion and chromatic aberration. The G4 lens may be a positive meniscus lens with the object-side lens surface convex toward the object, or a positive meniscus lens with the image-side lens surface convex toward the image.

[0170] In the optical system L0 of each embodiment, the front group LF preferably has at least one cemented lens consisting of a positive lens and a negative lens. This allows for good correction of axial chromatic aberration and lateral chromatic aberration. Furthermore, as in Examples 2, 3, 4, 6, and 7, by making the negative lens in the cemented lens a negative lens Gn that satisfies conditions (6) and (7), axial chromatic aberration of the g line can be corrected even more effectively.

[0171] In the optical system L0 of each embodiment, image blur correction can be performed by moving at least some of the lenses constituting the front group LF so as to include a component in a direction perpendicular to the optical axis. For example, in embodiments 7 and 8, the G8 lens moves to include a component perpendicular to the optical axis during image blur correction, but this is not limited to this. Furthermore, by ensuring that the lenses moved during image blur correction include at least a positive lens and a negative lens, fluctuations in chromatic aberration during image blur correction can be suppressed. Alternatively, a configuration in which three or more lenses move during image blur correction is also possible.

[0172] In the optical system L0 of each embodiment, the image-side focusing group LFR has a negative lens and a positive lens arranged sequentially in the optical axis direction. This allows for better correction of axial chromatic aberration at infinity focus and fluctuations in axial chromatic aberration during focusing. The above effect can be obtained regardless of the order in which the negative and positive lenses are arranged.

[0173] Furthermore, in the optical system L0 of each embodiment, it is preferable that the object-side lens surface of the lens positioned closest to the object among the lenses constituting the image-side focusing group LFR be concave toward the object. Also, it is preferable that the image-side lens surface of the second lens positioned from the object side be convex toward the image. As a result, the lens surface becomes substantially concentric with respect to the off-axis light beam incident on the image-side focusing group LFR, thereby suppressing aberrations and changes in the angle of view during focusing.

[0174] In the optical system L0 of each embodiment, the image-side focusing group LFR has a cemented lens formed by joining at least one negative lens Gn and at least one positive lens G2p. This allows for good correction of axial chromatic aberration at infinity focus and fluctuations in axial chromatic aberration during focusing.

[0175] Furthermore, it is preferable that the cemented lens be positioned furthest towards the object in the LFR (Long Frame Lens) group on the image side. This ensures that the cemented lens is positioned at a high height from the optical axis for the axial marginal rays, thereby further improving the correction of axial chromatic aberration.

[0176] Furthermore, it is preferable that the lens surface closest to the object in the cemented lens has a concave shape directed toward the object, and the lens surface closest to the image has a convex shape directed toward the image. This results in a substantially concentric shape with respect to the off-axis light beam incident on the image-side focusing group LFR, thereby suppressing aberrations and changes in the angle of view during focusing. In addition, the cemented lens may be made by bonding a biconcave lens and a biconvex lens in that order from the object side.

[0177] In the optical system L0 of each embodiment, it is preferable that the image-side focusing group LFR consists of five or fewer lenses. This reduces the weight of the lenses in the image-side focusing group LFR, enabling high-speed focusing. It also reduces the refractive power per lens, suppressing fluctuations in spherical aberration, field curvature, and chromatic aberration during focusing. To further enhance the aforementioned effects, it is even more preferable to configure the image-side focusing group LFR with four or fewer lenses. Furthermore, it is even more preferable to configure the image-side focusing group LFR with three or fewer lenses.

[0178] In the optical system L0 of each embodiment, it is preferable that the object-side lens surface of the lens positioned closest to the object in the image-side focusing group LFR is concave toward the object. This allows the off-axis light beam that has passed through the aperture diaphragm to be incident on the closest surface to the object in a substantially concentric manner, making it easier to suppress variations in astigmatism, coma aberration, and angle of view during focusing.

[0179] In the optical system L0 of each embodiment, the image-side focusing group LFR preferably includes an aspherical lens in which at least one surface is aspherical. This allows for good correction of spherical aberration, astigmatism, and coma aberration. Furthermore, it is more preferable to make one of the surfaces of the positive lenses included in the image-side focusing group LFR aspherical, as this reduces surface shape errors during molding. Moreover, it is more preferable to make the lens closest to the image or the second lens from the image side of the image-side focusing group LFR aspherical, as this allows for good correction of off-axis aberrations such as astigmatism and coma aberration.

[0180] In the optical system L0 of Examples 1 to 6, it is preferable that the rear group LR has a cemented lens consisting of a positive lens and a negative lens. This allows for good correction of chromatic aberration and astigmatism.

[0181] In the optical system L0 of each embodiment, the aspherical lens material may be an organic material such as plastic, or a glass material. Alternatively, an aspherical lens made of an organic material may be formed on a spherical glass by molding, joining, or bonding an organic material such as plastic with a thickness of about 0.01 mm to 1.00 mm onto the spherical glass.

[0182] In the optical system L0 of each embodiment of Example 7, the aspherical lens G12 arranged in the image-side focusing group LFR is made of plastic material. Thus, it is preferable to make at least one of the lenses arranged in the image-side focusing group LFR out of plastic material because it is possible to reduce the weight of the image-side focusing group LFR.

[0183] In the optical system L0 of each embodiment, it is preferable that the combined focal length fGcomp of the three cemented lens Gcomp arranged in the front group LF is a positive value. This allows for good correction of axial chromatic aberration and reduces the diameter of the lens arranged on the object side of the image-side focusing group LFR.

[0184] In the optical system L0 of each embodiment, the positive lens Gp is ​​preferably made of an organic resin material. This makes it possible to reduce the weight of the entire optical system L0. In addition, it is possible to obtain the anomalous partial dispersion required for the positive lens Gp as defined in condition (1).

[0185] Materials that satisfy condition (1) include, for example, resins and mixtures of resins and inorganic oxide fine particles. Examples of inorganic oxides include TiO2 (nd=2.304, νd=13.8), Nb2O5 (nd=2.367, νd=14.0), and ITO (nd=1.8571, νd=5.69). Other examples include CrO3 (nd=2.2178, νd=13.4) and BaTiO3 (nd=2.4362, νd=11.3). The refractive index for the d line in each material is denoted as nd.

[0186] By dispersing the aforementioned inorganic oxide fine particles in a solid material in an appropriate volume ratio, a material satisfying condition (1) can be obtained. Considering material scattering, the particle size of the fine particles is preferably between 2 nm and 50 nm. Dispersants may be added to suppress aggregation.

[0187] In the optical system L0 of each embodiment, it is preferable to set the refractive index of the positive lens with the greatest refractive power among the positive lenses constituting the three-bonded lens Gcomp to be 1.65 or greater and 2.1 or less.

[0188] When the positive lens Gp, which constitutes a three-element cemented lens Gcomp, is made of resin material, the positive lens Gp may deform due to external environmental changes such as temperature changes and moisture absorption, and the positive lens bonded to it on the object side or image side may also deform. If the refractive index of the positive lens bonded to the positive lens Gp is ​​less than 1.65, the mechanical hardness of the positive lens, i.e., the Young's modulus and Knoop hardness of the material of the positive lens, decreases. This makes the deformation of the positive lens more likely, and aberration fluctuations such as spherical aberration increase, which is undesirable. Furthermore, a refractive index of 1.70 or higher, and even more preferably 1.75 or higher, is preferable.

[0189] Furthermore, it is preferable to set the refractive index of the positive lens bonded to the positive lens Gp to 2.1 or less, as this allows for good correction of axial chromatic aberration.

[0190] In the optical system L0 of each embodiment, it is preferable that the Abbe number of the positive lens with the greatest refractive power among the three-span lens Gcomp has a value of 25 or more and 60 or less relative to the d line.

[0191] If the Abbe number of the positive lens joined to the positive lens Gp with respect to the d line exceeds 60, the mechanical stiffness of the positive lens decreases, making it easier for the positive lens to deform along with the deformation of the positive lens Gp, and thus increasing aberration fluctuations such as spherical aberration, which is undesirable. Furthermore, it is more preferable to set the Abbe number to 56 or less, and even more preferably to 53 or less.

[0192] Furthermore, if the Abbe number of the positive lens joined to the positive lens Gp with respect to the d line is less than 25, it becomes difficult to correct axial chromatic aberration, which is undesirable.

[0193] The numerical values ​​corresponding to Examples 1 to 8 are shown below.

[0194] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the distance along the optical axis between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the light incident side. Also, nd represents the refractive index of the material of each optical component with respect to the d line, and νd represents the Abbe number of the material of each optical component. The Abbe number νd and partial dispersion ratio θgF of a certain material are expressed as follows, when the refractive indices of the Fraunhofer lines d line (587.6 nm), F line (486.1 nm), C line (656.3 nm), and g line (wavelength 435.8 nm) are Nd, NF, NC, and Ng, respectively. νd = (Nd-1) / (NF-NC) θgF = (Ng - NF) / (NF - NC)

[0195] In each numerical example, d, focal length (mm), F-number, and half-angle of view (°) are all values ​​when the optical system of each example is focused on an object at infinity. Back focus BF is the air-equivalent distance from the final lens surface to the image plane. The total optical length is the distance from the first lens surface to the final lens surface plus the air-equivalent back focus. However, optical components such as optical filters, faceplates, quartz low-pass filters, and infrared cut filters are not included.

[0196] Furthermore, for each lens, if the lens surface is aspherical, the symbol * is added to the right of the surface number. The aspherical shape is defined as follows, where X is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis perpendicular to the optical axis, R is the paraaxial radius of curvature, k is the cone constant, and A4, A6, A8, A10, A12, A14, and A16 are the aspherical coefficients of their respective orders. x=( h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 +A14×h 14 +A16×h 16 This is expressed as follows. Note that "e±XX" in each aspherical coefficient is "×10± XX It means "...".

[0197] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd 1* 30.434 2.50 1.58313 59.4 2* 12.960 14.47 3 -8220.485 1.60 1.49700 81.7 4 48.726 5.09 5 -52.293 2.00 1.80400 46.5 6* 61.254 0.20 7 30.423 3.13 1.66565 35.6 8 60.805 4.01 9 -38.272 1.20 1.43387 95.1 10 89.263 0.20 11 33.379 9.18 1.75500 52.3 12 -25.609 1.05 1.84666 23.8 13 -50.774 0.20 14 121.888 4.07 1.83481 42.7 15 -55.780 3.62 16 -26.631 1.10 1.77047 29.7 17 -79.426 2.00 18 (aperture) ∞ 2.43 19 52.498 5.84 2.00100 29.1 20 -45.067 1.00 1.57060 20.1 21 -32.493 1.10 1.66565 35.6 22 71.141 (variable) 23 -120.281 7.55 1.43875 94.7 24 -14.562 1.00 1.77047 29.7 25 -57.242 0.20 26 39.251 8.64 1.49700 81.7 27 -31.928 0.60 28* 137.086 4.68 1.85400 40.4 29* -65.817 (variable) 30 -1214.157 7.51 1.59282 68.6 31 -22.877 1.05 1.91650 31.6 32 331.855 14.00 Image plane ∞ Aspherical data Front page K = 0.00000e+00 A 4=-9.44889e-06 A 6=-2.78211e-09 A 8= 1.38292e-11 A10=-1.87056e-14 A12= 7.67401e-18 2nd side K =-6.82090e-01 A 4=-2.16920e-06 A 6=-9.17628e-09 A 8=-2.33882e-10 A10= 8.26939e-13 A12=-1.85607e-15 Side 6 K = 0.00000e+00 A 4= 2.29625e-05 A 6= 1.76297e-08 A 8= 4.18666e-10 A10=-2.45395e-12 A12= 6.29348e-15 Page 28 K = 0.00000e+00 A 4=-2.17900e-05 A 6=-7.22596e-09 A 8=-1.48661e-10 A10= 1.85432e-12 A12=-3.03305e-15 Page 29 K = 0.00000e+00 A 4=-1.07831e-05 A 6=-3.03321e-09 A 8=-5.03844e-11 A10= 1.22127e-12 A12=-1.50312e-15 Focal length 14.42 F-number 1.46 Half-angle 52.34 Image height 18.68 Optical total length 118.50 BF 14.00 When focused at infinity, when focused on an object at a horizontal magnification of -0.1x. From the object surface to the first surface: Infinity 240.532 d22 5.08 4.08 d29 2.20 3.21 Lens group data Group starting plane focal length L1 1 36.30 L2 23 28.35 L3 30 -57.28 Single lens data Lens starting plane, focal length θgF 1 1 -40.86 2 3 -97.46 3 5 -34.81 4 7 87.86 5 9 -61.56 6 11 20.57 7 12 -62.22 8 14 46.32 9 16 -52.47 0.5951 10 19 24.97 11 20 198.38 0.7782 12 21 -33.37 0.5824 13 23 36.96 14 24 -25.61 0.5951 15 26 36.91 16 28 52.63 17 30 39.24 18 31 -23.32

[0198] [Numerical Example 2] Unit: mm Surface data Surface number r d nd νd 1 52.423 1.40 1.60311 60.6 2 19.691 5.03 3 29.399 2.00 1.58313 59.4 4* 17.890 16.43 5 -23.409 1.20 1.43875 94.7 6 -99.819 0.50 7 167.077 8.86 1.75500 52.3 s8 -20.287 1.05 1.85"478 24.8 9 -46.575 0.25 10 70.946 5.42 1.90043 37.4 11 -70.946 0.96 12 184.489 1.10 1.54072 47.2 13 50.592 4.99 14 (Aperture) ∞ 2.1"8 15 124.113 3.80 2.00069 25.5 A 16 -86.925 0.70 1.57060 20.1 17 -58.110 1.10 1.66565 35.6<00008"98>18 92.703 (Variable) 19 -31.832 5.02 1.49700 81.7 (注:原文中“ ”下的“s8 -20.287 1.05 1.85"478 24.8”疑似有误,已按原样翻译;“ ”下的“18 92.703 (可変)”疑似有误,已按原样翻译;“ ”下的“14(絞り) ∞ 2.18”疑似有误,已按原样翻译)20 -16.428 1.00 1.77047 29.7 21 -103.188 0.20 22 40.261 8.11 1.49700 81.7 23 -34.315 2.75 24* 87.489 5.76 1.80400 46.5 25* -54.320 (Variable) 26 326.711 6.95 1.59282 68.6 27 -29.793 1.05 1.66565 35.6 28 59.878 18.44 Image plane ∞ Aspherical data Fourth surface K =-4.88704e+00 A 4= 9.85206e-05 A 6=-4.60796e-07 A 8= 2.61477e-09 A10=-1.06987e-11 A12= 2.62680e-14 A14=-2.76184e-17 Twenty-fourth surface K = 0.00000e+00 A 4=-8.28107e-06 A 6= 7.81678e-09 A 8=-5.60781e-11 A10= 2.06771e-13 A12=-4.03084e-16 Twenty-fifth surface K = 0.00000e+00 A 4= 6.09726e-06 A 6= 5.11495e-09 A 8=-1.22444e-11 A10= 1.38078e-13 A12=-2.89951e-16 Focal length 20.60 F number 1.46 Half angle of view 42.54 Image height 18.90 Overall optical length 117.50 BF 18.44 When focused at infinity, when focused at an object distance with a lateral magnification of -0.1x Object surface to first surface Infinity 300.024 d18 9.05 7.44 d25 2.20 3.81 Lens group data Group starting plane focal length L1 1 45.15 L2 19 32.25 L3 26 -85.88 Single lens data Lens starting plane, focal length θgF 1 1 -53.14 2 3 -83.73 3 5 -70.04 4 7 24.46 5 8 -42.84 0.6122 6 10 40.12 7 12 -129.29 8 15 51.55 9 16 304.54 0.7782 10 17 -53.51 0.5824 11 19 61.63 12 20 -25.49 0.5951 13 22 38.67 14 24 42.45 15 26 46.39 16 27 -29.75

[0199] [Numerical Example 3] Unit: mm Surface data Face number rd nd νd 1 53.831 1.05 1.72916 54.7 2 22.346 14.69 3 -29.419 1.00 1.48749 70.2 4 188.029 3.89 5 -203.116 8.40 1.83481 42.7 6 -20.865 1.05 1.85478 24.8 7 -47.144 0.20 8 49.538 4.97 2.00069 25.5 9 -184.719 (Variable) 10 115.985 1.10 1.61340 44.3 11 45.795 (Variable) 12 (Aperture) ∞ 1.48 13 74.195 6.89 1.75500 52.3 14 -31.627 0.50 1.57060 20.1 15 -29.087 1.00 1.66565 35.6 16 87.405 (Variable)<00009-eight0>17 -34.716 5.17 1.49700 81.7 1⑧ -16.180 1.00 1.85478 24.8 19 -210.624 0.20 20 56.336 8.47 1.49700 81.7 21 -27.668 0.94 22* 90.528 6.73 1.80400 46.5 23* -46.782 (Variable) 24 119.008 6.50 1.92286 20.9 25 -⑤0.757 1.05 1.66565 35.6 26 38.876 5.37 27 -85.461 1.00 1.51742 52.4 [[ID=④④]]28 -595.711 15.00 Image plane ∞ Aspherical data The 22nd surface K = 0.00000e+00 A 4=-8.63588e-06 A 6= 2.870①5e-09 A 8=-1.46350e-11 A10= 5.23①93e-14 A12=-1.23076e-16 (注:原文中部分数字⑧、⑤0、①5、①93为猜测可能是错误的数字,按照原样保留并翻译,你可根据实际情况核对修正。)Page 23 K = 0.00000e+00 A 4= 3.58608e-06 A 6= 3.19398e-09 A 8=-1.61487e-11 A10= 1.02393e-13 A12=-1.58745e-16 Focal length 24.72 F-number 1.46 Field of view 37.40 Image height 18.90 Lens length: 117.50 BF 15.00 When focused at infinity, when focused on an object at a horizontal magnification of -0.1x. From the object's surface to the first surface: Infinity 226.884 d 9 0.50 2.71 d11 8.51 6.31 d16 8.64 6.89 d23 2.20 3.95 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 41.33 35.24 34.50 28.24 L2 10 -124.11 1.10 1.13 0.45 L3 12 183.91 9.87 -3.63 -9.67 L4 17 34.38 22.51 16.76 6.16 L5 24 -106.17 13.92 10.87 0.43 Single lens data Lens starting plane, focal length θgF 1 1 -53.14 2 3 -52.11 3 5 27.28 4 6 -44.61 0.6122 5 8 39.45 6 10 -124.11 0.5633 7 13 30.22 8 14 592.30 0.7782 9 15 -32.67 0.5824 10 17 55.81 11 18 -20.55 0.6122 12 20 38.63 13 22 39.22 14 24 41.89 15 25 -34.26 16 27 -192.96

[0200] [Numerical Example 4] Unit: mm Surface data Face number rd nd νd 1* 61.501 2.00 1.58313 59.4 2* 20.184 9.47 3 1901.390 1.80 1.49700 81.7 4 42.169 2.76 5 159.837 2.00 1.76802 49.2 6* 92.467 10.72 7 -28.269 1.20 1.43387 95.1 8 80.363 0.50 9 44.572 9.93 1.72916 54.7 10 -25.481 1.05 1.84666 23.8 11 -53.627 0.25 12 82.209 5.46 1.81600 46.6 13 -50.551 1.71 14 -37.489 1.10 1.62205 41.1 15 -87.960 2.83 16 (aperture) ∞ 2.32 17 147.999 4.55 2.00069 25.5 18 -49.961 1.00 1.57060 20.1 19 -35.594 1.10 1.66565 35.6 20 67.510 (Variable) 21 -39.085 5.89 1.43875 94.7 22 -15.511 1.00 1.77047 29.7 23 -82.267 0.20 24 39.313 7.60 1.49700 81.7 25 -35.308 2.28 26* 99.752 5.96 1.80400 46.5 27* -45.519 (variable) 28 575.113 7.49 1.59282 68.6 29 -25.634 1.05 1.66565 35.6 30 61.536 17.78 Image plane ∞ Aspherical data Front page K = 0.00000e+00 A 4= 1.29176e-06 A 6=-2.09110e-09 A 8= 4.38333e-12 2nd side K =-3.24571e-01 A 4=-5.71201e-06 A 6=-1.03383e-08 A 8=-7.16243e-11 Side 6 K =-7.00000e+00 A 4= 1.58032e-05 A 6= 1.44025e-08 A 8= 2.02465e-10 A10=-6.06022e-13 A12= 1.67729e-15 Page 26 K = 0.00000e+00 A 4=-1.06246e-05 A 6=-7.22658e-09 A 8= 2.73322e-11 A10= 9.27530e-14 A12=-1.23176e-16 Page 27 K = 0.00000e+00 A 4= 5.05881e-06 A 6=-6.17326e-09 A 8= 4.07297e-11 A10= 1.05263e-13 A12=-6.79698e-17 Focal length 18.45 F-number 1.46 Field of view 45.46 Image height 18.75 Lens length: 121.17 BF 17.78 d20 7.96 d27 2.20 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 47.25 61.75 44.85 39.61 L2 21 30.00 22.93 15.17 1.79 L3 28 -79.53 8.54 5.66 0.30 Single lens data Lens starting plane, focal length θgF 1 1 -52.46 2 3 -86.80 3 5 -289.37 4 7 -48.04 5 9 23.65 6 10 -58.34 7 12 39.08 8 14 -105.92 0.5690 9 17 37.76 10 18 211.58 0.7782 11 19 -34.86 0.5824 12 21 54.46 13 22 -24.97 0.5951 14 24 38.74 15 26 39.60 16 28 41.59 17 29 -27.06

[0201] [Numerical Example 5] Unit: mm Surface data Face number rd nd νd 1* 31.090 2.50 1.58313 59.4 2* 13.099 14.59 3 -530.553 1.70 1.49700 81.7 4 47.214 5.63 5 -49.986 2.00 1.80400 46.5 6* 87.783 0.20 7 31.641 3.06 1.66565 35.6 8 68.370 3.74 9 -36.085 1.20 1.43387 95.1 10 60.775 0.20 11 32.009 8.73 1.75500 52.3 12 -25.657 1.05 1.84666 23.8 13 -54.614 0.20 14 167.133 3.92 1.83481 42.7 15 -53.249 4.34 16 -24.473 1.10 1.77047 29.7 17 -65.694 2.00 18 (aperture) ∞ 1.68 19 50.345 6.13 2.00100 29.1 20 -44.102 1.00 1.57060 20.1 21 -32.378 1.10 1.66565 35.6 22 87.176 (Variable) 23 -140.226 7.75 1.43875 94.7 24 -14.948 1.00 1.77047 29.7 25 -65.160 0.20 26 40.856 8.72 1.49700 81.7 27 -31.383 0.20 28* 128.494 4.66 1.85400 40.4 29* -70.134 (variable) 30 -319.132 7.26 1.59282 68.6 31 -23.023 1.05 1.91650 31.6 32 -1191.612 15.50 Image plane ∞ Aspherical data Front page K = 0.00000e+00 A 4=-1.01110e-05 A 6= 8.17661e-10 A 8= 8.93040e-12 A10=-1.54052e-14 A12= 7.63241e-18 2nd side K =-6.44184e-01 A 4=-6.39936e-06 A 6=-1.43284e-08 A 8=-2.16244e-10 A10= 7.31957e-13 A12=-1.78412e-15 Side 6 K = 0.00000e+00 A 4= 2.13738e-05 A 6= 2.10113e-08 A 8= 3.60161e-10 A10=-2.14645e-12 A12= 6.19796e-15 Page 28 K = 0.00000e+00 A 4=-2.11705e-05 A 6=-5.23668e-09 A 8=-1.83281e-10 A10= 1.81505e-12 A12=-2.71601e-15 Page 29 K = 0.00000e+00 A 4=-1.02347e-05 A 6=-7.27343e-09 A 8=-3.83789e-11 A10= 1.01331e-12 A12=-1.00325e-15 Focal length 14.42 F-number 1.46 Half-angle 52.34 Image height 18.68 Optical total length 119.50 BF 15.50 When focused at infinity, when focused on an object at a horizontal magnification of -0.1x. From the object's surface to the first surface: Infinity 241.623 d22 4.90 3.89 d29 2.20 3.21 Lens group data Group starting plane focal length L1 1 36.74 L2 23 29.10 L3 30 -65.56 Single lens data Lens starting plane, focal length θgF 1 1 -40.91 2 3 -87.15 3 5 -39.36 4 7 85.64 5 9 -51.99 6 11 20.18 7 12 -58.12 8 14 48.77 9 16 -51.22 0.5951 10 19 24 27 11 20 207.03 0.7782 12 21 -35.34 0.5824 13 23 37.43 14 24 -25.40 0.5951 15 26 37.20 16 28 53.71 17 30 41.48 18 31 -25.63

[0202] [Numerical Example 6] Unit: mm Surface data Face number rd nd νd 1 43.024 1.40 1.61800 63.4 2 20.105 5.66 3 32.408 2.00 1.58313 59.4 4* 17.039 15.89 5 -23.276 1.20 1.43875 94.7 6 -65.876 0.50 7 1040.783 9.43 1.75500 52.3 8 -20.743 1.05 1.85478 24.8 9 -51.168 0.25 10 88.793 5.21 1.88100 40.1 11 -61.610 0.25 12 53.033 1.10 1.48749 70.2 13 33.098 6.53 14 (aperture) ∞ 1.38 15 56.211 4.07 2.00069 25.5 16 -282.390 0.70 1.57060 20.1 17 -106.816 1.10 1.61340 44.3 18 35.085 (variable) 19 -55.827 6.01 1.49700 81.7 20 -17.101 1.00 1.77047 29.7 21 -285.670 0.20 22 49.100 7.70 1.49700 81.7 23 -32.916 4.78 24* 167.193 5.11 1.80400 46.5 25* -71.686 (variable) 26 64.441 8.97 1.59282 68.6 27 -37.571 1.05 1.66565 35.6 28 96.827 20.51 Image plane ∞ Aspherical data Side 4 K =-4.93669e+00 A 4= 1.15091e-04 A 6=-5.84829e-07 A 8= 3.36673e-09 A10=-1.32319e-11 A12= 2.98902e-14 A14=-2.80832e-17 Page 24 K = 0.00000e+00 A 4=-3.47747e-06 A 6=-1.65912e-09 A 8= 4.12770e-11 A10=-9.38830e-14 A12=-2.12904e-17 Page 25 K = 0.00000e+00 A 4= 3.21233e-06 A 6= 1.28708e-09 A 8= 3.52617e-11 A10=-2.24322e-14 A12=-1.03425e-16 Focal length 20.60 F-number 1.50 Half-angle 42.57 Image height 18.93 Optical total length 125.00 BF 20.51 When focused at infinity, when focused on an object at a horizontal magnification of -0.1x. From the object's surface to the first surface, infinity: 309.542 d18 9.74 7.07 d25 2.20 4.88 Lens group data Group starting plane focal length L1 1 63.61 L2 19 45.28 L3 26 1142.84 Single lens data Lens starting plane, focal length θgF 1 1 -62.53 2 3 -64.71 3 5 -82.75 4 7 27.04 5 8 -41.47 0.6122 6 10 41.97 7 12 -183.95 8 15 47.13 9 16 300.65 0.7782 10 17 -42.93 0.5633 11 19 47.17 12 20 -23.65 0.5951 13 22 40.93 14 24 63.00 15 26 41.39 16 27 -40.54

[0203] [Numerical Example 7] Unit: mm Surface data Face number rd nd νd 1 64.036 1.25 1.59270 35.3 2 19.134 5.47 3 29.144 6.99 2.05090 26.9 4 -164.343 0.20 5 -214.914 1.10 1.67270 32.1 6 20.824 6.60 7 -23.834 0.90 1.58144 40.8 8 120.560 0.44 9 40.779 7.75 1.75500 52.3 10 -22.714 0.50 1.60401 20.8 11 -20.733 0.90 1.85478 24.8 12 -31.966 4.45 13 (aperture) ∞ 4.13 14 75.325 2.30 1.81600 46.6 15 30549.322 (variable) 16 -17.256 3.03 1.49700 81.7 17 -14.230 0.75 1.77047 29.7 18 -22.527 0.20 19 67.123 6.11 1.49700 81.7 20 -28.721 4.28 21* -64.055 4.45 1.53500 56.0 22* -24.736 (variable) 23 513.689 1.00 1.51742 52.4 24 60.438 7.24 25* -28.526 2.25 1.53500 56.0 26* -69.691 14.00 Image plane ∞ Aspherical data Page 21 K = 0.00000e+00 A 4=-9.95374e-06 A 6= 7.57077e-08 A 8=-1.20581e-10 A10= 2.35597e-13 Page 22 K = 0.00000e+00 A 4= 1.95965e-05 A 6= 4.39915e-08 A 8= 1.12423e-10 A10=-5.83395e-13 A12= 1.49458e-15 Page 25 K = 0.00000e+00 A 4=-6.90991e-06 A 6=-3.19089e-08 A 8=-1.15341e-10 Page 26 K = 0.00000e+00 A 4=-2.04198e-05 A 6=-1.90671e-08 A 8=-2.89877e-11 Focal length 34.00 F-number 1.85 Field of view 30.41 Image height 19.96 Lens length 98.50 BF 14.00 When focused at infinity, when focused on an object at a horizontal magnification of -0.1x. From the object's surface to the first surface, infinity: 313.087 d15 10.02 7.80 d22 2.20 4.41 Lens group data Group starting plane focal length L1 1 56.50 L2 16 35.52 L3 23 -52.86 Single lens data Lens starting plane, focal length θgF 1 1 -46.52 2 3 24.00 3 5 -28.17 4 7 -34.15 5 9 20.39 6 10 359.44 0.7230 7 11 -71.67 0.6122 8 14 92.53 9 16 122.53 10 17 -52.20 0.5951 11 19 41.35 12 21 72.47 13 23 -132.48 14 25 -92.02

[0204] [Numerical Example 8] Unit: mm Surface data Face number rd nd νd 1 53.821 1.25 1.59270 35.3 2 19.792 6.70 3 32.079 6.96 2.05090 26.9 4 -197.061 0.20 5 -219.698 1.10 1.69895 30.1 6 22.445 7.32 7 -22.851 0.90 1.53172 48.8 8 128.035 0.20 9 42.517 8.54 1.81600 46.6 10 -20.253 0.60 1.60401 20.8 11 -18.556 0.90 1.85451 25.2 12 -34.216 9.36 13 63.514 2.28 1.81600 46.6 14 406.615 1.50 15 (aperture) ∞ (variable) 16 -15.762 0.90 1.85451 25.2 17 -24.463 0.20 18 90.261 6.30 1.49700 81.7 19 -23.179 3.61 20* -159.864 4.42 1.76802 49.2 21* -36.419 (variable) 22 -433.667 1.00 1.56732 42.8 23 85.888 6.84 24* -26.724 2.25 1.53500 56.0 25* -63.795 13.00 Image plane ∞ Aspherical data Page 20 K = 0.00000e+00 A 4= 8.94338e-06 A 6= 4.88458e-08 A 8= 5.93594e-11 A10=-7.78918e-13 Page 21 K = 0.00000e+00 A 4= 2.50680e-05 A 6= 3.79676e-08 A 8= 2.03086e-10 A10=-1.01428e-12 A12=-1.35233e-16 Page 24 K = 0.00000e+00 A 4=-5.82583e-06 A 6=-2.82269e-08 A 8=-1.68916e-10 Page 25 K = 0.00000e+00 A 4=-1.70437e-05 A 6=-3.50373e-08 A 8=-3.50671e-11 Focal length 34.00 F-number 1.85 Field of view 30.41 Image height 21.64 Lens length 98.50 BF 13.00 When focused at infinity, when focused on an object at a horizontal magnification of -0.1x. From the object surface to the first surface: Infinity 310.391 d15 9.97 7.59 d21 2.20 4.58 Lens group data Group starting plane focal length L1 1 49.70 L2 16 36.67 L3 22 -50.42 Single lens data Lens starting plane, focal length θgF 1 1 -53.55 2 3 26.67 3 5 -29.08 4 7 -36.39 5 9 17.91 6 10 323.61 0.7230 7 11 -48.74 0.6103 8 13 91.97 9 16 -54.46 0.6103 10 18 37.81 11 20 60.47 12 22 -126.28 13 24 -87.82

[0205] The various values ​​in each numerical example are summarized in Tables 1 and 2 below.

[0206] [Table 1]

[0207] The lenses and their corresponding numerical values ​​that satisfy the conditions (1), (6), (7), (12), and (14) in each numerical example are summarized in Table 2 below.

[0208] [Table 2]

[0209] [Imaging device] Next, an embodiment of an imaging device equipped with the optical system L0 of this embodiment will be described.

[0210] Figure 17 is a schematic diagram of an imaging device 10 equipped with the optical system L0 of this embodiment. The imaging device 10 comprises a camera body 13, an optical system 11 similar to any of the embodiments 1 to 8 described above, and a light-receiving element 12 that converts the image formed by the optical system 11 into photoelectricity.

[0211] The imaging device 10 of this embodiment can obtain high-quality images formed by an optical system 11 that is wide-angle and has improved distortion correction and peripheral illumination ratio.

[0212] Furthermore, an image sensor such as a CCD or CMOS sensor can be used as the light-receiving element 12. In this case, the output image can be made higher quality by correcting various aberrations such as distortion and chromatic aberration of the image acquired by the light-receiving element 12, for example, using an electrical method.

[0213] Furthermore, the optical system L0 in each of the above embodiments can be applied not only to the digital still camera shown in Figure 17, but also to various optical instruments such as silver halide film cameras, video cameras, and telescopes. The camera itself may be either a fixed-lens type or a lens-interchangeable type.

[0214] [Lens device] Next, an embodiment of a lens device equipped with the optical system L0 of this embodiment will be described.

[0215] Figure 18 is a schematic diagram of the external appearance of a lens device 20 equipped with the optical system L0 of this embodiment. The lens device 20 in Figure 18 is a so-called interchangeable lens that is detachably attached to a camera body (not shown).

[0216] The lens device 20 includes a photographic optical system 21, which is the same as in any of the embodiments 1 to 8 described above. The lens device 20 also has a focus operating means 22 and an operating means 23 for changing the shooting mode.

[0217] The user operates the focus control means 22, which mechanically or electrically changes the arrangement of the imaging optical system 21 and alters the focal position. Alternatively, the user may operate the control means 23 to change the arrangement of the lens group of the imaging optical system 21 for purposes other than focusing. For example, the arrangement of the lens group of the imaging optical system 21 may be changed mechanically or electrically in conjunction with the operation of the control means 23, thereby altering the aberrations of the imaging optical system 21. In this case, it is preferable that the focal position does not substantially change.

[0218] Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of its gist.

[0219] Furthermore, the disclosures herein include the following configurations.

[0220] (Composition 1) An optical system comprising a front group having positive refractive power, an image-side focusing group having positive refractive power, and a rear group, arranged in order from the object side to the image side, When focusing from infinity to close distance, the image-side focusing group moves relative to the image plane so that the distance between the front group and the image-side focusing group, and the distance between the image-side focusing group and the rear group, changes. When focusing from infinity to close range, the rear group remains stationary with respect to the image plane. The aperture diaphragm that determines the on-axial light beam is located inside the front group or adjacent to the image side of the front group. The aforementioned front group has a positive lens Gp, The aperture diaphragm and the positive lens Gp remain stationary with respect to the image plane during focusing. An optical system characterized in that, when the Abbe number of the material of the positive lens Gp is ​​νdp, the partial dispersion ratio is θgFp, and the anomalous partial dispersion is ΔθgFp, the following conditional equation is satisfied. 0.050 < ΔθgFp < 0.250 however, ΔθgFp=θgFp-(B3×νdp3+B2×νdp2+B1×νdp+B0) B3 = -1.665 × 10⁻⁷ B2 = 5.213 × 10⁻⁵ B1 = -5.656 × 10⁻³ B0 = 7.278 × 10⁻¹ This is how it is expressed.

[0221] (Configuration 2) An optical system comprising a front group having positive refractive power, an image-side focusing group having positive refractive power, and a rear group, arranged in order from the object side to the image side, When focusing from infinity to close distance, the image-side focusing group moves relative to the image plane so that the distance between the front group and the image-side focusing group, and the distance between the image-side focusing group and the rear group, changes. During focusing, the rear group remains stationary with respect to the image plane. The optical system is characterized in that the image-side focusing group has at least two negative lenses.

[0222] (Composition 3) The optical system according to configuration 1 or 2, characterized in that, when the air-equivalent back focus of the optical system is focused at infinity, sk is the focal length of the entire optical system, and f is the focal length of the entire system, the following conditional equation is satisfied. 0.10 <sk / f<1.80

[0223] (Composition 4) The optical system according to any one of configurations 1 to 3, characterized in that, when the focal length of the front group is fLF and the focal length of the image-side focusing group is fLFR, the following conditional expression is satisfied. 0.30 <fLF / fLFR<3.00

[0224] (Composition 5) The optical system according to any one of configurations 1 to 4, characterized in that, when the focal length of the entire optical system is f and the focal length of the rear group is fLR, the following condition is satisfied. -1.50 <f / fLR<1.50

[0225] (Composition 6) The optical system according to any one of configurations 1 to 5, characterized in that the image-side focusing group comprises at least two positive lenses and at least one negative lens.

[0226] (Composition 7) The object-side lens surface of the lens positioned closest to the object in the aforementioned image-side focusing group is concave. The image-side lens surface, which is positioned closest to the image in the aforementioned image-side focusing group, has a convex shape. The optical system according to any one of configurations 1 to 6, characterized in that, when the radius of curvature of the object-side lens surface is RLFR1 and the radius of curvature of the image-side lens surface is RLFR2, the following conditional expression is satisfied. -1.50<(RLFR2-RLFR1) / (RLFR2+RLFR1)<1.50

[0227] (Composition 8) At least one of the front group or the image-side focusing group has a negative lens Gn, The optical system according to any one of configurations 1 to 7, characterized in that, when the refractive index of the negative lens Gn material with respect to the d line is Ndn, the Abbe number is νdn, the partial dispersion ratio with respect to the g line and the F line is θgFn, and the anomalous partial dispersion is ΔθgFn, the following conditional equation is satisfied. -0.20 <Ndn-(-0.0145425×νdn+2.28725)<0.05 -0.015 < ΔθgFn < 0.015 However, ΔθgFn = θgFn - (-0.0025116 × νdn + 0.67449) This is how it is expressed.

[0228] (Composition 9) The optical system according to any one of configurations 1 to 8, characterized in that the front group has at least one negative lens Gn.

[0229] (Composition 10) The optical system according to any one of configurations 1 to 9, characterized in that the image-side focusing group has at least one negative lens Gn.

[0230] (Composition 11) The optical system according to any one of configurations 1 to 10, characterized in that when the image-side focusing group is focused at infinity, the lateral magnification is βLFR and the lateral magnification of the rear group is βLR, the following conditional equation is satisfied. 0.50 < (1-βLFR2) × βLR2 < 2.50

[0231] (Composition 12) The optical system according to any one of configurations 1 to 11, characterized in that the aperture diaphragm is immovable in the optical axis direction with respect to the image plane during focusing.

[0232] (Composition 13) The optical system according to any one of configurations 1 to 12, characterized in that, when the air-equivalent back focus of the optical system is focused at infinity, sk is denoted by the focal length of the rear group, fLR is denoted by the following conditional equation. 0.00 <sk / |fLR|<0.80

[0233] (Composition 14) The optical system according to any one of configurations 1 to 13, characterized in that, when ΣDair is the sum of the air gaps on the optical axis from the object-side lens surface of the lens positioned closest to the object in the front group to the image-side lens surface of the lens positioned closest to the image in the rear group, L is the total optical length of the optical system, and sk is the air-reduced back focus of the optical system when focused to infinity, the following conditional equation is satisfied. 0.20 < ΣDair / (L-sk) < 0.70

[0234] (Composition 15) The optical system according to any one of configurations 1 to 14, characterized in that, when the total optical length of the optical system is L and the focal length of the entire optical system is f, the following conditional equation is satisfied. 1.50 <L / f<15.00

[0235] (Composition 16) The aforementioned image-side focusing group has a positive lens G2p, The optical system according to any one of configurations 1 to 15, characterized in that the following condition is satisfied when the Abbe number of the material of the positive lens G2p is νd2p. 60.00 < νd2p < 100.00

[0236] (Composition 17) An optical system according to any one of configurations 1 to 16, characterized in that the following condition is satisfied when the amount of movement of the image-side focusing group when focusing from infinity to an object distance at which the lateral magnification of the entire system becomes -0.1 times is MLFR, the sign of the amount of movement of the image-side focusing group when moving toward the image side when focusing from infinity to an object distance at which the lateral magnification of the entire system becomes -0.1 times is positive, and the distance on the optical axis from the aperture diaphragm of the optical system to the image plane when focused at infinity is DSP. -0.200 <MLFR / DSP<-0.005

[0237] (Composition 18) The aforementioned front group has a negative lens G1n, The optical system according to any one of configurations 1 to 17, characterized in that the following condition is satisfied when the Abbe number of the negative lens G1n is νd1n. 60.00 < νd1n < 100.00

[0238] (Composition 19) The optical system according to any one of configurations 1 to 18, characterized in that, when the focal length of the image-side focusing group is fLFR and the focal length of the entire optical system is f, the following conditional equation is satisfied. 0.50 <fLFR / f<3.00

[0239] (Composition 20) The optical system according to any one of configurations 1 to 19, characterized in that, when the optical system is focused at infinity, the distance on the optical axis from the aperture diaphragm to the image plane is DSP, the air-equivalent back focus is sk, and the total optical length of the optical system is L, the following conditional equation is satisfied. 0.30 < (DSP + sk) / L < 0.80

[0240] (Composition 21) The optical system according to any one of configurations 1 to 20, characterized in that, when the focal length of the front group is fLF and the focal length of the entire optical system is f, the following conditional equation is satisfied. 0.50 <fLF / f<5.00

[0241] (Composition 22) The optical system according to any one of configurations 1 to 21, characterized in that a negative lens is positioned on the image side of the rear group.

[0242] (Composition 23) The aforementioned front group has a positive lens, a cemented lens Gcomp consisting of the positive lens Gp and a negative lens, The optical system according to any one of configurations 1 to 22, characterized in that, when the focal length of the entire optical system is f and the focal length of the cemented lens Gcomp is fGcomp, the following conditional expression is satisfied. 0.00 <f / fGcomp<2.00

[0243] (Composition 24) The aforementioned group includes an object-side focusing group, An optical system according to any one of configurations 1 to 23, characterized in that the object-side focusing group moves relative to the image plane when focusing from infinity to a close distance.

[0244] (Composition 25) The optical system according to any one of configurations 1 to 24, characterized in that the aforementioned rear group has a positive refractive power.

[0245] (Composition 26) The optical system according to any one of configurations 1 to 25, characterized in that the aforementioned rear group has a negative refractive power.

[0246] (Composition 27) The aforementioned front group comprises, arranged in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. The optical system according to any one of configurations 1 to 26, characterized in that, when focusing from infinity to close distance, the second lens group moves relative to the image plane such that the distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group change.

[0247] (Composition 28) An imaging device comprising an optical system described in any one of configurations 1 to 27, and an image sensor that receives an image formed by the optical system. [Explanation of symbols]

[0248] L0 optical system LF front group LFR image side focusing group LR rear group SP aperture diaphragm GP positive lens

Claims

1. An optical system comprising a front group having positive refractive power, an image-side focusing group having positive refractive power, and a rear group, arranged in order from the object side to the image side, When focusing from infinity to close distance, the image-side focusing group moves relative to the image plane so that the distance between the front group and the image-side focusing group, and the distance between the image-side focusing group and the rear group, changes. When focusing from infinity to close range, the rear group remains stationary with respect to the image plane. The aperture diaphragm that determines the on-axial light beam is located inside the front group or adjacent to the image side of the front group. The front group has a positive lens Gp, An optical system characterized in that, when the Abbe number of the material of the positive lens Gp is ​​νdp, the partial dispersion ratio is θgFp, and the anomalous partial dispersion is ΔθgFp, the following conditional equation is satisfied. 0.10<ΔθgFp<0.160 however, ΔθgFp=θgFp-(B3×νdp ３ +B2×νdp ２ +B1×νdp+B0) B3=-1.665×10 －７ B2=5.21310 －５ B1=-5.656×� －３ B0 = 7.278 × 10 －１ This is how it is expressed.

2. The optical system according to claim 1, characterized in that, when the air-equivalent back focus of the optical system is focused at infinity, sk is the air-equivalent back focus, and f is the focal length of the entire optical system, the following conditional equation is satisfied. 0.10<sk / f<1.80

3. The optical system according to claim 1, characterized in that, when the focal length of the front group is fLF and the focal length of the image-side focusing group is fLFR, the following conditional equation is satisfied. 0.30<fLF / fLFR<3.00

4. The optical system according to claim 1, characterized in that, when the focal length of the entire optical system is f and the focal length of the rear group is fLR, the following condition is satisfied. -1.50<f / fLR<1.50

5. The optical system according to claim 1, characterized in that the image-side focusing group has at least two positive lenses and at least one negative lens.

6. The object-side lens surface of the lens positioned closest to the object in the aforementioned image-side focusing group is concave towards the object. The image-side lens surface located closest to the image in the aforementioned image-side focusing group has a convex shape toward the image side. The optical system according to claim 1, characterized in that, when the radius of curvature of the object-side lens surface is RLFR1 and the radius of curvature of the image-side lens surface is RLFR2, the following conditional equation is satisfied. -1.50<(RLFR2-RLFR1) / (RLFR2+RLFR1)<1.50

7. At least one of the front group or the image-side focusing group has a negative lens Gn, The optical system according to claim 1, characterized in that when the refractive index of the negative lens Gn material with respect to the d line is Ndn, the Abbe number is νdn, the partial dispersion ratio with respect to the g line and the F line is θgFn, and the anomalous partial dispersion is ΔθgFn, the following conditional equation is satisfied. -0.2000<N~~~~~(-1.454×10) －２ ×ν+2.287)<0050 -0.015<ΔθgFn<0.015 However, ΔθgFn = θgFn - (-2.511 × 10) －３ ×νdn + 0.674) This is how it is expressed.

8. The optical system according to claim 7, characterized in that the front group has at least one negative lens Gn.

9. The optical system according to claim 7, characterized in that the image-side focusing group has at least one negative lens Gn.

10. The optical system according to claim 1, characterized in that when the image-side focusing group is focused at infinity, the lateral magnification is βLFR and the lateral magnification of the rear group is βLR, and the following condition is satisfied. 0.50<(1-βLFR ２ )×βLR ２ <2.50

11. The optical system according to claim 1, characterized in that at least one of the aperture diaphragm and the positive lens Gp is ​​immovable with respect to the image plane during focusing.

12. The optical system according to claim 1, characterized in that, when the air-equivalent back focus of the optical system is focused at infinity, sk is the air-equivalent back focus, and the focal length of the rear group is fLR, the following conditional equation is satisfied. 0.00<sk / |fLR|<0.80

13. The optical system according to claim 1, characterized in that, when ΣDair is the sum of the air gaps on the optical axis from the object-side lens surface of the lens positioned closest to the object in the front group to the image-side lens surface of the lens positioned closest to the image in the rear group, L is the total optical length of the optical system, and sk is the air-reduced back focus of the optical system when focused to infinity, the following conditional equation is satisfied. 0.20<ΣDair / (L-sk)<0.70

14. The optical system according to claim 1, characterized in that, when the total optical length of the optical system is L and the focal length of the entire system of the optical system is f, the following condition is satisfied. 1.50<L / f<15.00

15. The image-side focusing group has a positive lens G2p, The optical system according to claim 1, characterized in that the following condition is satisfied when the Abbe number of the material of the positive lens G2p is νd2p. 60.00<νd2p<100.00

16. The optical system according to claim 1, characterized in that the following condition is satisfied when MLFR is the amount of movement of the image-side focusing group when focusing from infinity to an object distance at which the lateral magnification of the entire system becomes -0.1 times, the sign of the amount of movement of the image-side focusing group when it moves toward the image side when focusing from infinity to an object distance at which the lateral magnification of the entire system becomes -0.1 times is positive, and DSP is the distance on the optical axis from the aperture diaphragm of the optical system to the image plane when focused at infinity. -0.200<MLFR / DSP<-0.005

17. The aforementioned front group has a negative lens G1n, The optical system according to claim 1, characterized in that the following condition is satisfied when the Abbe number of the negative lens G1n is νd1n. 60.00<νd1n<100.00

18. The optical system according to claim 1, characterized in that, when the focal length of the image-side focusing group is fLFR and the focal length of the entire optical system is f, the following condition is satisfied. 0.50<fLFR / f<3.00

19. The optical system according to claim 1, characterized in that when the optical system is focused at infinity, the distance on the optical axis from the aperture diaphragm to the image plane is DSP, the air-equivalent back focus is sk, and the total optical length of the optical system is L, the following conditional equation is satisfied. 0.30<(DSP+sk) / L<0.80

20. The optical system according to claim 1, characterized in that, when the focal length of the front group is fLF and the focal length of the entire optical system is f, the following condition is satisfied. 0.50<fLF / f<5.00

21. The aforementioned front group has a positive lens, a positive lens Gp, and a cemented lens Gcomp consisting of a negative lens. The optical system according to claim 1, characterized in that, when the focal length of the entire optical system is f and the focal length of the cemented lens Gcomp is fGcomp, the following conditional equation is satisfied. 0.00<f / fGcomp<2.00

22. The aforementioned group includes an object-side focusing group, The optical system according to claim 1, characterized in that the object-side focusing group moves relative to the image plane when focusing from infinity to a close distance.

23. The optical system according to claim 1, characterized in that the aforementioned rear group has a positive refractive power.

24. The optical system according to claim 1, characterized in that the rear group has a negative refractive power.

25. The aforementioned front group comprises, arranged in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. The optical system according to claim 1, characterized in that, when focusing from infinity to close distance, the second lens group moves with respect to the image plane such that the distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group change.

26. An optical system comprising a front group having positive refractive power, an image-side focusing group having positive refractive power, and a rear group, arranged in order from the object side to the image side, When focusing from infinity to close distance, the image-side focusing group moves relative to the image plane so that the distance between the front group and the image-side focusing group, and the distance between the image-side focusing group and the rear group, changes. When focusing from infinity to close range, the rear group remains stationary with respect to the image plane. The aperture diaphragm that determines the on-axial light beam is located inside the front group or adjacent to the image side of the front group. The front group has a positive lens Gp, The aforementioned rear group has a negative lens positioned closest to the image, An optical system characterized in that, when the Abbe number of the material of the positive lens Gp is ​​νdp, the partial dispersion ratio is θgFp, and the anomalous partial dispersion is ΔθgFp, the following conditional equation is satisfied. 0.050<ΔθgFp<0.250 however, ΔθgFp=θgFp-(B3×νdp ３ +B2×νdp ２ +B1×νdp+B0) B3=-1.665×10 －７ B2=5.21310 －５ B1=-5.656×� －３ B0 = 7.278 × 10 －１ This is how it is expressed.

27. An imaging device comprising an optical system according to any one of claims 1 to 26 and an image sensor that receives an image formed by the optical system.

Images