Optical system and optical device

Abstract

To provide an optical system and an optical apparatus having good imaging performance.SOLUTION: An optical system OL used in an optical apparatus such as a camera 1 includes: a first lens group G1 having a diffractive optical element Lpf; a second lens group G2 that moves at the time of focusing; and a rear group GR having at least one lens group in order from an object side. The first lens group G1 has a positive lens at the most object side and satisfies following conditions: 0.40<TL / f<0.65, where TL: an overall length of the optical system OL at the time of infinite distance focusing, and f: a focal distance of a whole system of the optical system OL at the time of infinite distance focusing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical system and an optical device.

Background Art

[0002] Conventionally, an optical system miniaturized using a diffractive optical element has been proposed (see, for example, Patent Document 1). However, Patent Document 1 has a problem that further improvement in optical performance is desired.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The optical system according to the first aspect of the present invention It consists of a plurality of lens groups. During focusing, the distance between adjacent lens groups changes, and one or two lens groups move during focusing. The plurality of lens groups has, in order from the object side, a diffractive optical element and is fixed with respect to the image plane during focusing a first lens group, During focusing a second lens group that moves, and a rear group having at least one lens group consists of , the first lens group has a positive lens on the object side most, and satisfies the following condition. 0.40 < TL / f < 0.65 0.05 < -fr / f < 2.50 0.20 < -f2 / f < 0.40 However, TL: The overall length of the optical system when focused at infinity f: The overall focal length of the optical system when focused at infinity fr: Focal length of the rear group when focused at infinity f2: Focal length of the second lens group

[0005] The Second optical system according to the aspect of the present invention It consists of a plurality of lens groups. During focusing, the distance between adjacent lens groups changes, and one or two lens groups move during focusing. The plurality of lens groups has, in order from the object side, a diffractive optical element and is fixed with respect to the image plane during focusing a first lens group, During focusing a second lens group that moves, and a rear group having at least one lens groupconsists of The first lens group has a positive lens on the object side, The first lens group has two positive lenses arranged on the object side of the diffractive optical element, and satisfies the conditions of the following formula. 0.40 < TL / f < 0.65 0.05 < -fr / f < 2.50 However, TL: The overall length of the optical system when focused at infinity f: The focal length of the entire optical system when focused at infinity fr: Focal length of the rear group when focused at infinity

Brief Description of the Drawings

[0007]

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Mode for Carrying Out the Invention

[0008] Hereinafter, preferred embodiments will be described with reference to the drawings.

[0009] [First Embodiment] As shown in FIG. 1, the optical system OL according to the first embodiment includes, in order from the object side, a first lens group G1 having a diffractive optical element Lpf, a second lens group G2 that moves during focusing, and a rear group GL having at least one lens group. Further, the first lens group G1 has a positive lens (for example, a positive meniscus lens L11 shown in the first example of FIG. 1) on the most object side. By configuring in this way, the optical system OL can correct spherical aberration and axial chromatic aberration well while being small in size.

[0010] Such an optical system OL according to the present embodiment preferably satisfies the following conditional expression (1).

[0011] 0.40 < TL / f < 0.65 (1) However, TL: The overall length of the optical system OL when focused at infinity f: The focal length of the entire optical system OL when focused at infinity

[0012] The conditional expression (1) defines the ratio of the overall length of this optical system OL to the focal length of the entire optical system OL. By satisfying the conditional expression (1), the optical system OL can correct spherical aberration well while being small in size. If the upper limit value of the conditional expression (1) is exceeded, the spherical aberration is over-corrected, which is not preferable. In addition, in order to ensure the effect of the conditional expression (1), it is more desirable that the upper limit value of the conditional expression (1) be 0.57, further 0.55, 0.53. Also, if it is below the lower limit value of the conditional expression (1), the spherical aberration is under-corrected, which is not preferable. In addition, in order to ensure the effect of the conditional expression (1), it is more desirable that the lower limit value of the conditional expression (1) be 0.41.

[0013] Moreover, it is desirable that the optical system OL according to such an embodiment satisfy the following conditional expression (3).

[0014] 0.10 < TLpf / TL < 0.40 (3) However, TLpf: The distance on the optical axis from the lens surface closest to the object side of the optical system OL to the diffractive optical surface provided by the diffractive optical element Lpf when focused at infinity TL: The overall length of the optical system OL when focused at infinity

[0015] The conditional expression (3) defines the ratio of the distance on the optical axis from the lens surface closest to the object side of the optical system OL to the diffraction optical surface provided by the diffraction optical element Lpf with respect to the overall length of the optical system OL. By satisfying this conditional expression (3), while facilitating the manufacture of the diffraction optical element Lpf, it is possible to satisfactorily correct the chromatic aberration of the optical system OL. If it exceeds the upper limit value of the conditional expression (3), the chromatic aberration on the secondary axis becomes insufficiently corrected, which is not preferable. In order to ensure the effect of the conditional expression (3), it is more desirable to set the upper limit value of the conditional expression (3) to 0.35. Also, if it is below the lower limit value of the conditional expression (3), the chromatic aberration on the secondary axis becomes overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (3), it is more desirable to set the lower limit value of the conditional expression (3) to 0.18.

[0016] [Second Embodiment] As shown in FIG. 1, the optical system OL according to the second embodiment has a diffraction optical element Lpf, and in order from the object side, has a first lens group G1, a second lens group G2 that moves during focusing, and a rear group GR having at least one lens group. Also, the first lens group G1 has a positive lens (for example, the positive meniscus lens L11 shown in FIG. 1 of the first embodiment). By configuring it in this way, the optical system OL can satisfactorily correct spherical aberration and axial chromatic aberration while being small in size.

[0017] It is desirable that the optical system OL according to this embodiment satisfies the following conditional expression (2).

[0018] 0.60 < θgFp1 < 1.00 (2) However, θgFp1: The partial dispersion ratio of the medium of the positive lens having the smallest Abbe number with respect to the d-line of the medium within the first lens group G1

[0019] Conditional expression (2) defines the partial dispersion ratio of the medium of the positive lens with the smallest Abbe number for the d-line of the medium among the positive lenses included in the first lens group G1. By configuring in this way, the optical system OL can correct chromatic aberration well while being small in size. If it exceeds the upper limit value of conditional expression (2), the chromatic aberration on the secondary axis becomes overcorrected, which is not preferable. In addition, in order to ensure the effect of conditional expression (2), it is more desirable to set the upper limit value of conditional expression (2) to 0.75. Also, if it is below the lower limit value of conditional expression (2), the chromatic aberration on the secondary axis becomes undercorrected, which is not preferable. In addition, in order to ensure the effect of this conditional expression (2), it is more desirable to set the lower limit value of conditional expression (2) to 0.61.

[0020] Here, the partial dispersion ratio θgFp1 is defined by the following formula (a) when the refractive index for the g-line (λ = 435.8 nm) of the medium of the corresponding lens is ng, the refractive index for the F-line (λ = 486.1 nm) is nF, and the refractive index for the C-line (λ = 656.3 nm) is nC.

[0021] θgFp1 = (ng - nF) / (nF - nC) (a)

[0022] Moreover, it is desirable that the optical system OL according to such an embodiment satisfies the following conditional expression (3).

[0023] 0.10 < TLpf / TL < 0.40 (3) However, TLpf: The distance on the optical axis from the lens surface closest to the object side of the optical system OL to the diffractive optical surface provided by the diffractive optical element Lpf when focused at infinity TL: The overall length of the optical system OL when focused at infinity

[0024] Conditional expression (3) defines the ratio of the distance on the optical axis from the lens surface closest to the object side of this optical system OL to the diffractive optical surface provided by the diffractive optical element Lpf with respect to the overall length of the optical system OL. By satisfying this conditional expression (3), while facilitating the manufacture of the diffractive optical element Lpf, the chromatic aberration of the optical system OL can be corrected favorably. If it exceeds the upper limit value of conditional expression (3), the chromatic aberration on the secondary axis becomes insufficiently corrected, which is not preferable. In addition, in order to ensure the effect of conditional expression (3), it is more desirable that the upper limit value of conditional expression (3) be 0.35, and further 0.33. Also, if it is below the lower limit value of conditional expression (3), the chromatic aberration on the secondary axis becomes over-corrected, which is not preferable. In addition, in order to ensure the effect of conditional expression (3), it is more desirable that the lower limit value of conditional expression (3) be 0.14, and further 0.18.

[0025] Moreover, in such an optical system OL according to this embodiment, it is desirable that the first lens group G1 has the diffractive optical element Lpf. By configuring it in this way, the optical system OL can favorably correct spherical aberration and axial chromatic aberration while being small-sized.

[0026] Moreover, it is desirable that such an optical system OL according to this embodiment satisfies the following conditional expression (1).

[0027] 0.40 < TL / f < 0.65 (1) However, TL: Overall length of the optical system OL when focused at infinity f: Focal length of the entire optical system OL when focused at infinity

[0028] The conditional expression (1) defines the ratio of the overall length of the optical system OL to the overall focal length of the entire optical system OL. By satisfying the conditional expression (1), the optical system OL can correct spherical aberration well while being small in size. If the upper limit value of the conditional expression (1) is exceeded, the spherical aberration will be overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (1), it is more desirable that the upper limit value of the conditional expression (1) be 0.57, further 0.55, and 0.53. Also, if it is below the lower limit value of the conditional expression (1), the spherical aberration will be undercorrected, which is not preferable. In order to ensure the effect of the conditional expression (1), it is more desirable that the lower limit value of the conditional expression (1) be 0.41.

[0029] [Third Embodiment] As shown in FIG. 1, the optical system OL according to the third embodiment has an aperture stop S, and includes, in order from the object side, a first lens group G1 having a diffractive optical element Lpf, a second lens group G2 that moves during focusing, and a rear group GR having at least one lens group. Also, the diffractive optical element Lpf is disposed on the image plane side of the largest air gap within the first lens group G1. By configuring in this way, the optical system OL can correct spherical aberration and axial chromatic aberration well while being small in size.

[0030] Also, it is desirable that the optical system OL according to such an embodiment satisfy the following conditional expression (4).

[0031] 0.30 < d1 / dG1 < 0.60 (4) However, d1: The maximum value of the air gaps on the optical axis within the first lens group G1 dG1: The distance on the optical axis from the most object-side lens surface of the first lens group G1 to the most image-plane side lens surface of the first lens group G1

[0032] Conditional expression (4) defines the ratio of the maximum value among the air spaces on the optical axis within the first lens group G1 to the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the first lens group G1. By satisfying this conditional expression (4), it is possible to achieve both good spherical aberration correction and weight reduction of the optical system OL. If it is below the lower limit value of conditional expression (4), the optical system OL cannot be weight-reduced, which is not preferable. In order to ensure the effect of conditional expression (4), it is more desirable that the lower limit value of conditional expression (4) be 0.305. Also, if it exceeds the upper limit value of conditional expression (4), aberration correction becomes impossible, which is not preferable. In order to ensure the effect of conditional expression (4), it is more desirable that the upper limit value of conditional expression (4) be 0.58, and further 0.56.

[0033] Also, it is desirable that the optical system OL according to such an embodiment satisfies the following conditional expression (5).

[0034] 0.30 < TLs / TL < 0.70 (5) However, TLs: The distance on the optical axis from the lens surface closest to the object side of the optical system OL to the aperture stop S when focused at infinity TL: The overall length of the optical system OL when focused at infinity

[0035] Conditional expression (5) defines the ratio of the distance on the optical axis from the lens surface closest to the object side of the optical system OL to the aperture stop S to the overall length of the optical system OL when focused at infinity. By satisfying this conditional expression (5), it is possible to correct the magnification chromatic aberration and field curvature of the optical system OL well. If it is below the lower limit value of conditional expression (5), the field curvature is over-corrected, and it becomes difficult to correct the magnification chromatic aberration, which is not preferable. In order to ensure the effect of conditional expression (5), it is more desirable that the lower limit value of conditional expression (5) be 0.35, and further 0.38. Also, if it exceeds the upper limit value of conditional expression (5), the field curvature is under-corrected, and it becomes difficult to correct the magnification chromatic aberration, which is not preferable. In order to ensure the effect of conditional expression (5), it is more desirable that the upper limit value of conditional expression (5) be 0.68, and further 0.65.

[0036] Also, it is desirable that the optical system OL according to such an embodiment satisfies the following conditional expression (1).

[0037] 0.40 < TL / f < 0.65 (1) However,[[]] TL: Total length of the optical system OL when focused at infinity f: Focal length of the entire optical system OL when focused at infinity

[0038] Conditional expression (1) defines the ratio of the total length of this optical system OL to the focal length of the entire optical system OL. By satisfying conditional expression (1), the optical system OL can correct spherical aberration well while being small in size. If the upper limit value of conditional expression (1) is exceeded, the spherical aberration will be over-corrected, which is not preferable. In addition, in order to ensure the effect of conditional expression (1), it is more desirable that the upper limit value of conditional expression (1) be 0.57, further 0.55, 0.53. Also, if the lower limit value of conditional expression (1) is below, the spherical aberration will be under-corrected, which is not preferable. In addition, in order to ensure the effect of conditional expression (1), it is more desirable that the lower limit value of conditional expression (1) be 0.41.

[0039] The following description is common to the above-described first to third embodiments.

[0040] In such an optical system OL according to this embodiment, it is desirable that the diffractive optical element Lpf be disposed on the object side of the most object-side negative lens component. By configuring in this way, the optical system OL can correct axial chromatic aberration well while being small in size.

[0041] Also, in such an optical system OL according to this embodiment, it is desirable that the first lens group G1 have two positive lenses disposed on the object side of the diffractive optical element Lpf. By configuring in this way, the spherical aberration can be corrected well while making the optical system OL small in size.

[0042] In addition, it is desirable that the optical system OL according to such an embodiment satisfies the following conditional expression (6).

[0043] 0.05 < -fr / f < 2.50 (6) However,[[]]END]] fr: Focal length of the rear group GR when focused at infinity f: Focal length of the entire optical system OL when focused at infinity

[0044] The conditional expression (6) defines the ratio of the focal length of the rear group GR to the focal length of the entire optical system OL when focused at infinity. By satisfying this conditional expression (6), the optical system OL can correct spherical aberration well while being small in size. If the upper limit value of the conditional expression (6) is exceeded, the refractive power of the second lens group G2 becomes strong, making it difficult to correct spherical aberration during close focusing, which is not preferable. In order to ensure the effect of the conditional expression (6), it is more desirable that the upper limit value of the conditional expression (6) be 1.00, and further 0.50. Also, if the lower limit value of the conditional expression (6) is exceeded, the refractive power borne by the rear group GR becomes large, making it difficult to correct axial chromatic aberration, which is not preferable. In order to ensure the effect of the conditional expression (6), it is more desirable that the lower limit value of the conditional expression (6) be 0.06, and further 0.20.

[0045] In addition, in the optical system OL according to such an embodiment, it is desirable that the first lens group G1 has a positive refractive power. By configuring it in this way, spherical aberration can be corrected well while making the optical system OL small in size.

[0046] Also, in the optical system OL according to such an embodiment, it is desirable that the diffractive optical element Lpf has two diffractive element elements made of different optical materials, these two diffractive element elements are joined to each other, and a diffractive optical surface is formed on the joint surface of the diffractive element elements. In the following description, the two diffractive element elements of the diffractive optical element Lpf that are joined to each other and on whose joint surface a diffractive optical surface is formed are referred to as phase Fresnel elements (PF elements Epf). By configuring in this way, the optical system OL can correct axial chromatic aberration well in a wide wavelength range by the diffractive optical element Lpf, and can suppress diffractive flare of unnecessary orders in the wide wavelength range generated by the diffractive optical element Lpf.

[0047] Here, it is desirable that the diffractive optical element Lpf has a lens component, and one of the two diffractive element elements (PF elements Epf) is joined to the lens surface on the object side or the lens surface on the image side of this lens component. By configuring in this way, the manufacture of the diffractive optical element Lpf becomes easy. Note that the lens component constituting the diffractive optical element Lpf is preferably in a meniscus shape. By configuring in this way, the spherical aberration generated by the diffractive optical element Lpf can be reduced.

[0048] Also, it is desirable that one of the two diffractive element elements (PF elements Epf) of the diffractive optical element Lpf is in contact with air. By configuring in this way, the weight of the diffractive optical element Lpf can be made lighter.

[0049] Also, it is desirable that the optical system OL according to such an embodiment satisfies the following conditional expression (7).

[0050] 12.0 < νdp1 < 32.0 (7) However, νdp1: The Abbe number of the positive lens having the smallest Abbe number with respect to the d-line of the medium within the first lens group G1

[0051] The conditional expression (7) defines the minimum value among the Abbe numbers of the media of the positive lenses in the first lens group G1. By satisfying this conditional expression (7), it is possible to satisfactorily correct chromatic aberration while making the optical system OL compact. If the upper limit value of the conditional expression (7) is exceeded, the primary axial chromatic aberration becomes overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (7), it is more desirable that the upper limit value of the conditional expression (7) be 30.0, and further 28.0. Also, if it is below the lower limit value of the conditional expression (7), the primary axial chromatic aberration becomes undercorrected, which is not preferable. In order to ensure the effect of the conditional expression (7), it is more desirable that the lower limit value of the conditional expression (7) be 15.0, and further 17.0.

[0052] Moreover, it is desirable that the optical system OL according to such an embodiment satisfy the following conditional expression (8).

[0053] 0.10 < d1 / TL < 0.31 (8) However, d1: the maximum value among the air spaces on the optical axis within the first lens group G1 TL: the overall length of the optical system OL at infinity focus

[0054] The conditional expression (8) defines the ratio of the maximum value among the air spaces on the optical axis within the first lens group G1 to the overall length of the optical system OL at infinity focus. By satisfying this conditional expression (8), it is possible to satisfactorily correct spherical aberration while reducing the weight of the optical system OL. If the upper limit value of the conditional expression (8) is exceeded, the spherical aberration becomes undercorrected, which is not preferable. In order to ensure the effect of the conditional expression (8), it is more desirable that the upper limit value of the conditional expression (8) be 0.30, and further 0.25. Also, if it is below the lower limit value of the conditional expression (8), the spherical aberration becomes overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (8), it is more desirable that the lower limit value of the conditional expression (8) be 0.12.

[0055] Moreover, it is desirable that the optical system OL according to such an embodiment satisfy the following conditional expression (9).

[0056] 0.20 < f1 / f < 0.50 (9) However, f1: Focal length of the first lens group G1 f: Focal length of the entire optical system OL when focused at infinity

[0057] Conditional expression (9) defines the ratio of the focal length of the first lens group G1 to the focal length of the entire optical system OL when focused at infinity. By satisfying this conditional expression (9), spherical aberration can be corrected well while making the optical system OL compact. If the upper limit value of conditional expression (9) is exceeded, spherical aberration will be overcorrected, which is not preferable. In addition, in order to ensure the effect of conditional expression (9), it is more desirable to set the upper limit value of conditional expression (9) to 0.45, and further to 0.40. Also, if it is below the lower limit value of conditional expression (9), spherical aberration will be undercorrected, which is not preferable. In addition, in order to ensure the effect of conditional expression (9), it is more desirable to set the lower limit value of conditional expression (9) to 0.23, and further to 0.25.

[0058] Moreover, it is desirable that the optical system OL according to such an embodiment satisfies the following conditional expression (10).

[0059] 0.15 < -f2 / f < 0.40 (10) However, f2: Focal length of the second lens group G2 f: Focal length of the entire optical system OL when focused at infinity

[0060] The conditional expression (10) defines the ratio of the focal length of the second lens group G2 to the focal length of the entire optical system OL at infinity focus. By satisfying this conditional expression (10), while making the optical system OL compact, it is possible to satisfactorily correct spherical aberration during close focus. If the upper limit value of the conditional expression (10) is exceeded, the refractive power borne by the rear group GR increases, and the axial chromatic aberration becomes overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (10), it is more desirable to set the upper limit value of the conditional expression (10) to 0.37, and further to 0.33. Also, if it is below the lower limit value of the conditional expression (10), the spherical aberration during close focus becomes overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (10), it is more desirable to set the lower limit value of the conditional expression (10) to 0.17, and further to 0.20.

[0061] Also, it is desirable that the optical system OL according to such an embodiment satisfies the following conditional expression (11).

[0062] 0.10 < dpf / TL < 0.31 (11) However, dpf: The air interval on the optical axis between the lens disposed on the object side adjacent to the diffractive optical element Lpf TL: The overall length of the optical system OL at infinity focus

[0063] The conditional expression (11) defines the ratio of the air interval on the optical axis between the lens disposed on the object side adjacent to the diffractive optical element Lpf to the overall length of the optical system OL at infinity focus. By satisfying this conditional expression (11), while facilitating the manufacture of the diffractive optical element Lpf, it is possible to satisfactorily correct the chromatic aberration of the optical system OL. If it exceeds the upper limit value of the conditional expression (11), the secondary axial chromatic aberration becomes undercorrected, which is not preferable. In order to ensure the effect of the conditional expression (11), it is more desirable to set the upper limit value of the conditional expression (11) to 0.30, and further to 0.25. Also, if it is below the lower limit value of the conditional expression (11), the secondary axial chromatic aberration becomes overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (11), it is more desirable to set the lower limit value of the conditional expression (11) to 0.12.

[0064] Further, it is desirable that the optical system OL according to such an embodiment satisfies the conditional expression (12) shown below.

[0065] 8.0 < fpf / f < 22.0 (12) However, fpf: Focal length of the diffractive optical surface of the diffractive optical element Lpf f: Focal length of the entire optical system OL when focused at infinity

[0066] The conditional expression (12) defines the ratio of the focal length of the diffractive optical surface of the diffractive optical element Lpf to the focal length of the entire optical system OL when focused at infinity. By satisfying this conditional expression (12), it is possible to satisfactorily correct chromatic aberration while making the optical system OL compact. If the upper limit value of the conditional expression (12) is exceeded, the chromatic aberration on the secondary axis becomes insufficiently corrected, which is not preferable. In order to ensure the effect of the conditional expression (12), it is more desirable that the upper limit value of the conditional expression (12) be 20.0, further 19.0, 18.0. Also, if the lower limit value of the conditional expression (12) is exceeded, the chromatic aberration on the secondary axis becomes overcorrected, which is not preferable. In order to ensure the effect of the conditional expression (12), it is more desirable that the lower limit value of the conditional expression (12) be 9.0, further 10.0, 11.0.

[0067] Also, in the optical system OL according to such an embodiment, it is desirable that the first lens group G1 has one or two positive lenses on the object side of the largest air interval among the air intervals on the optical axis within the first lens group G1. When having one positive lens, it is more desirable to have an aspherical surface. By configuring in this way, it is possible to satisfactorily correct spherical aberration while making the optical system OL compact.

[0068] Further, it is desirable that the optical system OL according to such an embodiment satisfies the conditional expression (13) shown below.

[0069] dL1L2 / TL < 0.080 (13) However, dL1L2: The distance on the optical axis from the lens surface closest to the object side of the optical system OL to the lens surface closest to the image side of the lens group located on the object side of the largest air space within the first lens group G1 TL: The overall length of the optical system OL when focused at infinity

[0070] Conditional expression (13) defines the ratio of the distance on the optical axis from the lens surface closest to the object side of the optical system OL when focused at infinity to the lens surface closest to the image side of the lens group located on the object side of the largest air space within the first lens group G1. By satisfying this conditional expression (13), the optical system OL can correct spherical aberration well while being compact. In addition, in order to ensure the effect of conditional expression (13), it is more desirable to set the upper limit value of conditional expression (13) to 0.075.

[0071] Moreover, it is desirable for the optical system OL according to such an embodiment to have an aperture stop S on the object side of the second lens group G2. By configuring it in this way, the image plane curvature at a short distance of the optical system OL can be maintained well.

[0072] Moreover, it is desirable for the optical system OL according to such an embodiment to have an aperture stop S on the image side of the second lens group G2. By configuring it in this way, the spherical aberration at a short distance of the optical system OL can be maintained well.

[0073] Moreover, it is desirable for the optical system OL according to such an embodiment to satisfy the following conditional expression (14).

[0074] θgFp1 + 0.00316×νdp1 > 0.706 (14) However, θgFp1: The partial dispersion ratio of the medium of the positive lens with the smallest Abbe number for the d-line of the medium within the first lens group G1 νdp1: The Abbe number of the positive lens with the smallest Abbe number for the d-line of the medium within the first lens group G1

[0075] Conditional expression (14) defines the relationship between the partial dispersion ratio and the Abbe number of the positive lens having the smallest Abbe number for the d-line of the medium among the positive lenses included in the first lens group G1. By satisfying this conditional expression (14), the axial chromatic aberration and the magnification chromatic aberration of the optical system OL can be corrected well. In order to ensure the effect of the conditional expression (14), it is more desirable that the lower limit value of the conditional expression (14) be 0.708, further 0.710, 0.712, 0.714, 0.716.

[0076] Also, in the optical system OL according to such an embodiment, it is desirable that the lens disposed on the object side of the largest air interval among the air intervals on the optical axis within the first lens group G1 be composed of one positive lens. By configuring in this way, the entire optical system OL can be lightened.

[0077] Also, in the optical system OL according to such an embodiment, it is desirable that the second lens group G2 have a negative refractive power. By configuring in this way, the second lens group G2, which is the focusing group, can be lightened. Also, it is easy to increase the image plane sensitivity of the optical system OL, and both good close-distance performance and shortening of the overall length can be achieved.

[0078] Also, in the optical system OL according to such an embodiment, it is desirable that the rear group GR have a lens group that moves during focusing. By configuring in this way, the variation of the axial chromatic aberration between the infinite focus and the close-distance focus of the optical system OL can be suppressed.

[0079] Also, in the optical system OL according to such an embodiment, it is desirable that the rear group GR be composed of, in order from the object side, a third lens group G3, a fourth lens group G4 that moves during focusing, and a fifth lens group G5. By configuring in this way, the variation of the axial chromatic aberration between the infinite focus and the close-distance focus of the optical system OL can be suppressed.

[0080] Also, it is desirable that the optical system OL according to such an embodiment satisfy the following conditional expression (15).

[0081] ndp1 < 1.810 (15) However, ndp1: The refractive index of the medium of the positive lens with the smallest Abbe number for the d-line of the medium within the first lens group G1

[0082] The conditional expression (15) defines the refractive index of the medium of the positive lens with the smallest Abbe number for the d-line of the medium among the positive lenses included in the first lens group G1. By satisfying this conditional expression (15), the Petzval sum of the optical system OL can be set to an appropriate value, enabling both miniaturization and weight reduction of the optical system OL and good correction of field curvature. If the upper limit value of the conditional expression (15) is exceeded, it is not preferable because good correction of field curvature and coma aberration cannot be achieved simultaneously. In addition, in order to ensure the effect of this conditional expression (15), it is more desirable to set the upper limit value of the conditional expression (15) to 1.800.

[0083] Note that the conditions and configurations described above each exhibit the effects described above, and are not limited to those that satisfy all the conditions and configurations. It is possible to obtain the above-described effects even by satisfying any one condition or configuration, or any combination of conditions or configurations.

[0084] Next, a camera, which is an optical device equipped with the optical system OL according to the present embodiment, will be described with reference to FIG. 17. This camera 1 is a so-called mirrorless interchangeable-lens camera equipped with the optical system OL according to the present embodiment as a photographing lens 2. In this camera 1, light from an object (subject) (not shown) is condensed by the photographing lens 2 and forms a subject image on the imaging surface of the imaging unit 3 via an OLPF (Optical Low Pass Filter: optical low pass filter) (not shown). Then, the subject image is photoelectrically converted by a photoelectric conversion element provided in the imaging unit 3 to generate an image of the subject. This image is displayed on an EVF (Electronic View Finder: electronic viewfinder) 4 provided in the camera 1. Thereby, the photographer can observe the subject via the EVF 4.

[0085] When a release button (not shown) is pressed by the photographer, the image photoelectrically converted by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can photograph a subject using this camera 1. In the present embodiment, an example of a mirrorless camera has been described. However, even when the optical system OL according to the present embodiment is mounted on a single-lens reflex type camera having a quick return mirror in the camera body and observing a subject through a finder optical system, the same effects as those of the above-described camera 1 can be achieved.

[0086] Note that the content described below can be appropriately adopted as long as the optical performance is not impaired.

[0087] In the present embodiment, the optical system OL having a three-group configuration or a five-group configuration has been shown. However, the above-described configuration conditions and the like are also applicable to other group configurations such as a four-group, six-group, and seven-group configurations. Also, a configuration in which a lens or a lens group is added on the most object side, or a configuration in which a lens or a lens group is added on the most image plane side may be used. Specifically, a configuration in which a lens group whose position with respect to the image plane is fixed during zooming or focusing is added on the most image plane side can be considered. Also, the lens group refers to a portion having at least one lens separated by an air interval that changes during zooming or focusing. Also, the lens component refers to a single lens or a cemented lens in which a plurality of lenses are cemented.

[0088] Also, a focusing lens group that moves a single or a plurality of lens groups or partial lens groups in the optical axis direction to focus on an object from an infinite distance object to a close distance object may be used. In this case, the focusing lens group can also be applied to autofocus and is suitable for motor driving (such as an ultrasonic motor) for autofocus. In particular, it is preferable that at least a part of the second lens group G2 is used as the focusing lens group, and the positions of the other lenses with respect to the image plane are fixed during focusing. Considering the load on the motor, the focusing lens group is preferably composed of a single lens.

[0089] Alternatively, the lens group or partial lens group may be moved so as to have a displacement component in a direction orthogonal to the optical axis, or may be rotationally moved (oscillated) in a plane direction including the optical axis to correct image blur caused by camera shake. In particular, it is preferable that at least a part of the third lens group G3 is the anti-shake lens group.

[0090] Also, the lens surface may be formed as a spherical surface or a flat surface, or may be formed as an aspherical surface. When the lens surface is a spherical surface or a flat surface, it is preferable because lens processing and assembly adjustment become easy, and deterioration of optical performance due to errors in processing and assembly adjustment can be prevented. Also, it is preferable because deterioration of the rendering performance is small even when the image plane is displaced. When the lens surface is an aspherical surface, the aspherical surface may be any of an aspherical surface by grinding, a glass mold aspherical surface formed by molding glass into an aspherical shape, and a composite aspherical surface formed by forming a resin on the surface of the glass into an aspherical shape. Further, the lens surface may be a diffractive surface, and the lens may be a gradient-index lens (GRIN lens) or a plastic lens.

[0091] The aperture stop S is preferably disposed on the object side or the image plane side of the second lens group G2, but the role may be substituted by the lens frame without providing a member as the aperture stop.

[0092] Furthermore, an antireflection film having a high transmittance in a wide wavelength range may be provided on each lens surface in order to reduce flare and ghost and achieve high-contrast optical performance.

[0093] Hereinafter, an outline of the manufacturing method of the optical system OL according to the present embodiment will be described with reference to FIG. 18. First, a first lens group G1 having a diffractive optical element, a second lens group G2 that moves during focusing, and a rear group GR having at least one lens group are each prepared (step S100). Next, a positive lens is disposed on the most object side of the first lens group G1 (step S200). Then, it is disposed so as to satisfy the conditions according to the above-described predetermined conditional expression (for example, conditional expression (1)) (step S300).

[0094] With the configuration as described above, an optical system and an optical device having good imaging performance can be provided.

Embodiment

[0095] Hereinafter, each embodiment of the present application will be described with reference to the drawings. Note that FIGS. 1, 3, 5, 7, 9, 11, 13, and 15 are cross-sectional views showing the configurations and refractive power distributions of the optical systems (OL1 to OL8) according to the first to eighth embodiments.

[0096] In each embodiment, the phase shape ψ of the diffractive optical surface of the diffractive optical element Lpf is represented by the following formula (b).

[0097] ψ(h,n) =(2π / (n×λ0))×(C2h 2 +C4h 4 ) (b) However, h: Height in the direction perpendicular to the optical axis n: Order of diffracted light λ0: Design wavelength Ci: Phase coefficient (i = 2, 4)

[0098] Also, the refractive power φD of the diffractive optical surface represented by formula (b) for an arbitrary wavelength λ and an arbitrary diffraction order n is represented by the following formula (c) using the lowest-order phase coefficient C2.

[0099] φD(λ,n) = -2×C2×n×λ / λ0 (c)

[0100] In the tables of each embodiment, a # mark is attached to the right side of the surface number for the diffractive optical surface.

[0101] Also, in the eighth embodiment, for the aspherical surface, when the height in the direction perpendicular to the optical axis is y, the distance (sag amount) along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface is S(y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the conic constant is K, and the aspherical coefficient of the nth order is An, it is represented by the following formula (d).

[0102] S(y)=(y 2 / r) / {1+(1-K×y 2 / r 2 ) 1 / 2} +A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 (d)

[0103] Here, in each embodiment, the aspherical coefficient A2 of the second order is 0. In the table of the eighth embodiment, an asterisk is attached to the right side of the surface number for the aspherical surface.

[0104] Also, in each embodiment, "E-n" indicates "×10 -n ".

[0105] Also, the following embodiments show specific examples of the present invention, and the present invention is not limited thereto.

[0106] [First Embodiment] FIG. 1 is a diagram showing the configuration of an optical system OL1 according to the first embodiment. This optical system OL1 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power. The rear group GL is composed of a third lens group G3.

[0107] The first lens group G1 is composed of, in order from the object side, a positive meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a convex surface facing the object side, a diffractive optical element Lpf provided with a PF element Epf on the image-side lens surface of a positive meniscus lens L13 with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L14 and a biconcave negative lens L15, a positive meniscus lens L16 with a convex surface facing the object side, and a cemented lens formed by cementing a biconcave negative lens L17 and a biconvex positive lens L18. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side. The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L31 and a negative meniscus lens L32 with a concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L33 and a biconcave negative lens L34, a biconcave negative lens L35, a cemented lens formed by cementing a biconvex positive lens L36 and a biconcave negative lens L37, a cemented lens formed by cementing a negative meniscus lens L38 with a convex surface facing the object side and a positive meniscus lens L39 with a convex surface facing the object side, and a cemented lens formed by cementing a biconvex positive lens L310 and a negative meniscus lens L311 with a concave surface facing the object side. The aperture stop S is disposed on the object side of the second lens group G2 (between the first lens group G1 and the second lens group G2). Among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the biconvex positive lens L18.

[0108] Note that the PF element Epf included in the diffractive optical element Lpf has two diffractive element elements made of different optical materials. These two diffractive element elements are cemented to each other, and a diffractive optical surface is formed on the cemented surface of the diffractive element elements (the same applies to the following embodiments).

[0109] In this optical system OL1, focusing from an infinite distance to a close-distance object is performed by moving the second lens group G2 in the image plane direction.

[0110] Table 1 below lists the specifications of the optical system OL1. In the overall specifications of this Table 1, f represents the focal length of the entire optical system OL1, FNO represents the F-number, ω represents the semi-field angle [°], Y represents the maximum image height, TL represents the overall length, and BF represents the value of the back focus. Here, the overall length TL indicates the distance (actual distance) on the optical axis from the lens surface on the object side (the first surface) to the image plane I when focused at infinity. Also, the back focus BF indicates the distance (air-equivalent length) on the optical axis from the lens surface on the image plane side (the 36th surface) to the image plane I when focused at infinity. In the lens data, the first column m represents the order (surface number) of the lens surfaces from the object side along the direction of light propagation, the second column r represents the radius of curvature of each lens surface, the third column d represents the distance on the optical axis (spacing between surfaces) from each optical surface to the next optical surface, and the fourth column nd and the fifth column νd represent the refractive index and Abbe number for the d-line (λ = 587.6 nm). Also, a curvature radius of 0.0000 indicates a plane, and the refractive index of air 1.000000 is omitted. Note that the lens group focal length indicates the surface number of the start surface of each lens group and the focal length.

[0111] Here, in all the following specification values, the unit of the focal length f, radius of curvature r, surface spacing d, and other lengths is generally "mm", but since the optical system can obtain the same optical performance even with proportional magnification or reduction, it is not limited to this. Also, the explanations of these symbols and the explanation of the specification table are the same in the following embodiments.

[0112] (Table 1) First Embodiment [Overall Specifications] f = 585.0002 FNO = 5.7100 ω[°]= 2.10557 Y = 21.6 TL = 309.4549 BF = 95.6894 [Lens Data] m r d nd νd Object Plane ∞ 1 198.3492 8.5332 1.487490 70.32 2 1056.3396 0.2000 3 97.9481 13.9490 1.487490 70.32 4 411.8100 37.8970 5 116.0369 7.0000 1.516800 64.13 6 131.4346 0.2000 1.529500 36.27 7# 131.4346 0.3000 1.549800 50.91 8 131.4346 5.0000 9 65.7068 9.3004 1.487490 70.32 10 -2050.4055 2.3000 1.903660 31.27 11 61.4265 2.0000 12 85.9524 5.7962 1.497820 82.57 13 486.7361 20.4814 14 -118.7660 2.0000 1.950000 29.37 15 70.1339 7.4700 1.755750 24.71 16 -82.2312 4.0746 17 0.0000 d1 Aperture Stop S 18 150.0827 1.2000 1.487490 70.32 19 55.8583 d2 20 530.3423 2.8063 1.575010 41.51 21 -89.2692 1.2000 2.001000 29.12 22 -204.0519 3.0000 23 103.1226 5.4513 1.672700 32.18 24 -48.5264 1.2000 1.497820 82.57 25 56.1112 4.6753 26 -74.6931 1.2000 1.696800 55.52 27 53.4710 3.0000 28 38.0170 10.0000 1.603420 38.03 29 -30.9083 1.2000 1.497820 82.57 30 68.5697 2.4552 31 1018.2057 1.2000 1.772500 49.62 32 31.3787 5.0191 1.603420 38.03 33 1387.8678 0.2000 34 54.4867 8.3630 1.603420 38.03 35 -26.8376 1.2000 1.922860 20.88 36 -169.6934 BF Image plane ∞ [Focal length of lens group] Focal length of the starting surface of the lens group First lens group G1 1 205.9 Second lens group G2 18 -183.3 Third lens group G3 20 -147.5

[0113] In this optical system OL1, the seventh surface is a diffractive optical surface. Table 2 below shows the diffractive optical surface data, that is, the values of the design wavelength λ0, the order n, and the phase coefficients C2 and C4 for each position.

[0114] (Table 2) [Diffractive optical surface data] m λ0 n C2 C4 7 587.6 1.0 -4.96241E-05 1.65424E-09

[0115] In this optical system OL1, the axial air interval d0 between the object and the first lens group G1, the axial air interval d1 between the first lens group G1 and the aperture stop S, and the axial air interval d2 between the second lens group G2 and the third lens group G3 change during focusing. The following Table 3 shows the variable intervals at infinity focus and close-focus. Note that d0 represents the distance from the most object-side surface (the first surface) of the optical system OL1 to the object, f represents the focal length, β represents the magnification, and BF represents the back focus. These explanations are the same in the following embodiments.

[0116] (Table 3) [Variable Interval Data] Focus State Infinity Close Distance f 585.00017 - β - -0.18866 d0 ∞ 3090.5451 d1 4.00000 29.28428 d2 44.58471 4.60934 BF 95.68940 95.6894

[0117] The aberration diagrams such as the spherical aberration diagram, astigmatism diagram, distortion aberration diagram, chromatic aberration of magnification diagram, and coma aberration diagram of this optical system OL1 at infinity focus and close-focus are shown in FIG. 2. In each aberration diagram, FNO represents the F-number, NA represents the numerical aperture, and Y represents the image height. In the spherical aberration diagram, the value of the F-number or numerical aperture corresponding to the maximum aperture is shown. In the astigmatism diagram and distortion aberration diagram, the maximum value of the image height is shown respectively. In the coma aberration diagram, the value of each image height is shown. d represents the d-line (λ = 587.6 nm), and g represents the g-line (λ = 435.8 nm). In the astigmatism diagram, the solid line represents the sagittal image plane, and the dashed line represents the meridional image plane. Also, in the aberration diagrams of each of the following embodiments, the same reference numerals as in this embodiment are used. From these aberration diagrams, it can be seen that this optical system OL1 has good correction of various aberrations.

[0118] [Second Embodiment] FIG. 3 is a diagram showing the configuration of the optical system OL2 according to the second embodiment. This optical system OL2 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power. The rear group GL is composed of a third lens group G3.

[0119] The first lens group G1 is composed of, in order from the object side, a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object side, a diffractive optical element Lpf provided with a PF element Epf on the lens surface on the image side of a positive meniscus lens L13 with its convex surface facing the object side, a cemented lens formed by cementing a positive meniscus lens L14 with its convex surface facing the object side and a negative meniscus lens L15 with its convex surface facing the object side, a positive meniscus lens L16 with its convex surface facing the object side, and a cemented lens formed by cementing a negative meniscus lens L17 with its convex surface facing the object side and a positive meniscus lens L18 with its convex surface facing the object side. The second lens group G2 is composed of a negative meniscus lens L21 with its convex surface facing the object side. The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a positive meniscus lens L31 with its concave surface facing the object side and a negative meniscus lens L32 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L33 and a biconcave negative lens L34, a biconcave negative lens L35, a cemented lens formed by cementing a biconvex positive lens L36 and a biconcave negative lens L37, a cemented lens formed by cementing a biconcave negative lens L38 and a biconvex positive lens L39, and a cemented lens formed by cementing a biconvex positive lens L310 and a negative meniscus lens L311 with its concave surface facing the object side. The aperture stop S is disposed on the object side of the second lens group G2 (between the first lens group G1 and the second lens group G2). Among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the positive meniscus lens L18.

[0120] In this optical system OL2, focusing from infinity to a close object is performed by moving the second lens group G2 in the image plane direction.

[0121] The values of the specifications of the optical system OL2 are listed in Table 4 below.

[0122] (Table 4) Second Embodiment [Overall Specifications] f = 585.00008 FNO = 5.7100 ω[°]= 2.08967 Y = 21.6 TL = 311.4549 BF = 74.44520 [Lens Data] m r d nd νd Object Plane ∞ 1 256.7991 8.0000 1.487490 70.32 2 -10718.8210 0.2000 3 126.8427 9.0000 1.487490 70.32 4 304.0593 46.3492 5 104.9091 7.0000 1.516800 64.13 6 165.7799 0.2000 1.529500 36.27 7# 165.7799 0.3000 1.549800 50.91 8 165.7799 5.0000 9 77.8329 7.7320 1.487490 70.32 10 186.6794 2.3000 1.903660 31.27 11 60.4528 2.0000 12 55.5648 8.9778 1.518600 69.89 13 180.2474 36.1145 14 503.2004 2.0000 1.902650 35.77 15 34.5282 5.8266 1.663820 27.35 16 14816.1980 4.0000 17 0.0000 d1 Aperture Stop S 18 200.8922 1.2000 1.497820 82.57 19 50.2042 d2 20 -236.9030 3.1882 1.575010 41.51 21 -41.3579 1.2000 2.001000 29.12 22 -71.0261 3.0000 23 94.0731 4.5855 1.717360 29.57 24 -59.5874 1.2000 1.593190 67.90 25 55.9640 4.0002 26 -102.2571 1.2000 1.772500 49.62 27 69.6362 4.8061 28 33.5531 9.8502 1.595510 39.21 29 -29.3690 1.2000 1.497820 82.57 30 56.6631 3.3836 31 -251.0099 1.2000 1.883000 40.69 32 29.4179 5.6817 1.620040 36.40 33 -962.9336 0.2000 34 67.6496 10.2804 1.737999 32.33 35 -21.7365 1.2000 1.922860 20.88 36 -108.3418 BF Image plane ∞ [Focal length of lens group] Focal length of the starting surface of the lens group First lens group G1 1 217.2 Second lens group G2 18 -134.8 Third lens group G3 20 -233.5

[0123] In this optical system OL2, the seventh surface is a diffractive optical surface. Table 5 below shows the diffractive optical surface data, that is, the values of the design wavelength λ0, the order n, and the phase coefficients C2 and C4 for each position.

[0124] (Table 5) [Diffractive optical surface data] m λ0 n C2 C4 7 587.6 1.0 -4.55065E-05 6.56102E-11

[0125] Also, in this optical system OL2, the axial air interval d0 between the object and the first lens group G1, the axial air interval d1 between the first lens group G1 and the aperture stop S, and the axial air interval d2 between the second lens group G2 and the third lens group G3 change during focusing. The following Table 6 shows the variable intervals at infinity focus and close-focus.

[0126] (Table 6) [Variable interval data] Focus state Infinity Close distance f 585.00008 - β - -0.18912 d0 ∞ 3088.5451 d1 4.00000 29.76301 d2 30.63380 4.87079 BF 74.44520 74.44520

[0127] The various aberration diagrams of the spherical aberration diagram, astigmatism diagram, distortion diagram, chromatic aberration of magnification diagram, and coma diagram of this optical system OL2 at infinity focus and close-focus are shown in FIG. 4. From these respective aberration diagrams, it can be seen that this optical system OL2 has good correction of various aberrations.

[0128] [Third Embodiment] FIG. 5 is a diagram showing the configuration of an optical system OL3 according to the third embodiment. This optical system OL3 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power. Further, the rear group GL is composed of a third lens group G3.

[0129] The first lens group G1 is composed of, in order from the object side, a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object side, a diffraction optical element Lpf provided with a PF element Epf on the image-side lens surface of a positive meniscus lens L13 with its convex surface facing the object side, a cemented lens formed by cementing a negative meniscus lens L14 with its convex surface facing the object side and a biconvex positive lens L15, a cemented lens formed by cementing a biconvex positive lens L16 and a biconcave negative lens L17, and a cemented lens formed by cementing a biconcave negative lens L18 and a biconvex positive lens L19. The second lens group G2 is composed of a negative meniscus lens L21 with its convex surface facing the object side. The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a negative meniscus lens L31 with its convex surface facing the object side and a biconvex positive lens L32, a biconcave negative lens L33, a cemented lens formed by cementing a biconcave negative lens L34 and a biconvex positive lens L35, a cemented lens formed by cementing a biconvex positive lens L36 and a biconcave negative lens L37, a cemented lens formed by cementing a biconvex positive lens L38, a biconcave negative lens L39, and a positive meniscus lens L310 with its convex surface facing the object side, and a cemented lens formed by cementing a biconvex positive lens L311 and a negative meniscus lens L312 with its concave surface facing the object side. The aperture stop S is disposed on the image side of the second lens group G2 (between the second lens group G2 and the third lens group G3). Among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the biconvex positive lens L19.

[0130] In this optical system OL3, focusing from an infinite distance to a near-distance object is performed by moving the second lens group G2 in the image plane direction.

[0131] The following Table 7 shows the values of the specifications of the optical system OL3.

[0132] (Table 7) Third Embodiment [Overall Specifications] f = 999.99972 FNO = 8.1600 ω[°]= 1.22886 Y = 21.6 TL = 419.0888 BF = 84.30629 [Lens Data] m r d nd νd Object plane ∞ 1 268.7128 10.8775 1.487490 70.32 2 -2672.1391 0.2000 3 116.5428 14.0606 1.487490 70.32 4 322.3537 58.1581 5 130.0360 7.0000 1.516800 64.13 6 142.9490 0.2000 1.529500 36.27 7# 142.9490 0.3000 1.549800 50.91 8 142.9490 13.9998 9 221.0597 2.8967 1.850260 32.35 10 66.9470 10.0000 1.487490 70.32 11 -10794.8470 2.5000 12 73.9911 10.6970 1.487490 70.32 13 -286.5976 1.6241 1.834000 37.18 14 97.1167 26.7475 15 -20459.2230 2.5058 1.902650 35.77 16 63.1106 5.5966 1.808090 22.74 17 -966.5886 d1 18 446.8149 1.2000 1.487490 70.32 19 94.2997 d2 20 0.0000 30.0896 Aperture stop S 21 1180.5271 1.2000 1.883000 40.69 22 39.2566 3.1265 1.720467 34.71 23 -163.6972 3.4467 24 -219.7919 1.2000 1.593190 67.90 25 38.7994 4.2256 26 -97.9560 1.2000 1.593190 67.90 27 33.0021 4.4839 1.717360 29.57 28 -1429.3587 3.2000 29 31.1058 7.4309 1.567320 42.58 30 -89.4330 1.5069 1.883000 40.69 31 817.9183 10.2551 32 81.6733 5.6315 1.737999 32.33 33 -34.7206 2.0000 1.883000 40.69 34 23.5273 3.6692 1.654115 39.68 35 45.4280 5.0000 36 48.4921 9.6222 1.737999 32.33 37 -25.9571 2.0000 1.945944 17.98 38 -135.4658 BF Image plane ∞ [Focal length of lens group] Focal length of the starting surface of the lens group First lens group G1 1 320.7 Second lens group G2 18 -245.5 Third lens group G3 20 -160.6

[0133] In this optical system OL3, the seventh surface is a diffractive optical surface. Table 8 below shows the diffractive optical surface data, that is, the values of the design wavelength λ0, the order n, and the phase coefficients C2 and C4 for each position.

[0134] (Table 8) [Diffractive optical surface data] m λ0 n C2 C4 7 587.6 1.0 -4.38195E-05 -5.85224E-10

[0135] Also, in this optical system OL3, the axial air interval d0 between the object and the first lens group G1, the axial air interval d1 between the first lens group G1 and the second lens group G2, and the axial air interval d2 between the second lens group G2 and the aperture stop S change during focusing. The following Table 9 shows the variable intervals at infinity focus and close focus.

[0136] (Table 9) [Variable interval data] Focus state Infinity Close distance f 999.99972 - β - -0.1330 d0 ∞ 7580.9112 d1 8.57559 32.49421 d2 58.35509 34.43646 BF 84.30629 84.30629

[0137] The aberration diagrams such as the spherical aberration diagram, astigmatism diagram, distortion aberration diagram, chromatic aberration of magnification diagram, and coma aberration diagram of this optical system OL3 at infinity focus and close focus are shown in FIG. 6. From these aberration diagrams, it can be seen that this optical system OL3 has good correction of various aberrations.

[0138] [Fourth Embodiment] FIG. 7 is a diagram showing the configuration of an optical system OL4 according to the fourth embodiment. This optical system OL4 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power. The rear group GL is composed of a third lens group G3.

[0139] The first lens group G1 is composed of, in order from the object side, a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object side, a diffractive optical element Lpf provided with a PF element Epf on the image-side lens surface of a positive meniscus lens L13 with its convex surface facing the object side, a cemented lens formed by cementing a positive meniscus lens L14 with its convex surface facing the object side and a negative meniscus lens L15 with its convex surface facing the object side, a positive meniscus lens L16 with its convex surface facing the object side, and a cemented lens formed by cementing a biconcave negative lens L17 and a biconvex positive lens L18. The second lens group G2 is composed of a negative meniscus lens L21 with its convex surface facing the object side. The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L31 and a biconvex positive lens L32, a biconcave negative lens L33, a cemented lens formed by cementing a biconcave negative lens L34 and a biconvex positive lens L35, a cemented lens formed by cementing a biconvex positive lens L36 and a biconcave negative lens L37, a cemented lens formed by cementing a biconcave negative lens L38 and a biconvex positive lens L39, a cemented lens formed by cementing a biconvex positive lens L310 and a biconcave negative lens L311, and a cemented lens formed by cementing a biconvex positive lens L312 and a biconcave negative lens L313. The aperture stop S is disposed on the image side of the second lens group G2 (between the second lens group G2 and the third lens group G3). Among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the biconvex positive lens L18.

[0140] In this optical system OL4, focusing from an infinite distance to a close object is performed by moving the second lens group G2 in the image plane direction.

[0141] The values of the specifications of the optical system OL4 are listed in Table 10 below.

[0142] (Table 10) Fourth Embodiment [Overall Specifications] f = 999.96318 FNO = 8.1600 ω[°]= 1.22353 Y = 21.6 TL = 419.4549 BF = 94.37907 [Lens Data] m r d nd νd Object plane ∞ 1 519.3503 8.3069 1.487490 70.32 2 -1148.6620 0.2000 3 127.9584 13.3914 1.487490 70.32 4 344.4064 79.0796 5 114.2251 7.0000 1.516800 64.13 6 154.1141 0.1000 1.529500 36.27 7# 154.1141 0.2500 1.549800 50.91 8 154.1141 10.6237 9 91.6865 10.0000 1.487490 70.32 10 2798.7715 2.3000 1.903660 31.27 11 65.1594 2.0000 12 67.6949 9.0709 1.487490 70.32 13 780.3038 23.6453 14 -196.7990 1.2000 1.732110 46.18 15 109.6535 5.7885 1.663820 27.35 16 -175.2636 d1 17 504.3668 1.2000 1.487490 70.32 18 92.7728 d2 19 0.0000 13.8858 Aperture stop S 20 -130.6366 1.2000 2.001000 29.12 21 47.2332 3.1612 1.730371 32.23 22 -71.5789 3.4144 23 -236.3231 1.2000 1.772500 49.62 24 49.6984 2.9728 25 -115.6087 1.2000 1.593190 67.90 26 41.3816 3.4871 1.795040 28.69 27 -612.0200 3.2000 28 30.5076 6.1577 1.612660 44.46 29 -37.3580 1.2000 1.593190 67.90 30 218.9654 3.0689 31 -326.2570 1.8000 1.953750 32.33 32 24.8675 5.2938 1.612930 36.94 33 -90.5368 14.8971 34 85.0536 5.7888 1.730371 32.23 35 -32.6053 1.8000 1.772500 49.62 36 34.9782 1.0342 37 36.9993 7.5539 1.850000 27.03 38 -35.3416 1.8000 1.945944 17.98 39 154.0811 BF Image plane ∞ [Focal length of lens group] [Focal length of the starting surface of the lens group] First lens group G1 1 256.6 Second lens group G2 17 -233.4 Third lens group G3 19 -91.6

[0143] In this optical system OL4, the seventh surface is a diffractive optical surface. Table 11 below shows the diffractive optical surface data, that is, the values of the design wavelength λ0, the order n, and the phase coefficients C2 and C4 for each position.

[0144] (Table 11) [Diffractive optical surface data] m λ0 n C2 C4 7 587.6 1.0 -4.47066E-05 -2.42983E-10

[0145] Also, in this optical system OL4, the axial air interval d0 between the object and the first lens group G1, the axial air interval d1 between the first lens group G1 and the second lens group G2, and the axial air interval d2 between the second lens group G2 and the aperture stop S change during focusing. The following Table 12 shows the variable intervals at infinity focus and close-focus.

[0146] (Table 12) [Variable Interval Data] Focus State Infinity Close Distance f 999.99979 - β - -0.13123 d0 ∞ 7580.5451 d1 8.69620 24.48434 d2 58.10735 42.31921 BF 94.37907 94.37907

[0147] Figs. 8 show the aberration diagrams of spherical aberration, astigmatism, distortion, chromatic aberration of magnification, and coma aberration of this optical system OL4 at infinity focus and close-focus. From these aberration diagrams, it can be seen that this optical system OL4 has good correction of various aberrations.

[0148] [Fifth Embodiment] Fig. 9 is a diagram showing the configuration of an optical system OL5 according to the fifth embodiment. This optical system OL5 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power. The rear group GL is composed of a third lens group G3.

[0149] The first lens group G1 is composed of, in order from the object side, a positive meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a convex surface facing the object side, a diffractive optical element Lpf provided with a PF element Epf on the lens surface on the image side of a positive meniscus lens L13 with a convex surface facing the object side, a cemented lens formed by cementing a negative meniscus lens L14 with a convex surface facing the object side and a biconvex positive lens L15, a cemented lens formed by cementing a biconvex positive lens L16 and a biconcave negative lens L17, and a cemented lens formed by cementing a biconcave negative lens L18 and a biconvex positive lens L19. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side. The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L31 and a biconvex positive lens L32, a biconcave negative lens L33, a cemented lens formed by cementing a biconcave negative lens L34 and a biconvex positive lens L35, a cemented lens formed by cementing a biconvex positive lens L36 and a negative meniscus lens L37 with a concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L38 and a biconcave negative lens L39, a biconvex positive lens L310, and a cemented lens formed by cementing a positive meniscus lens L311 with a concave surface facing the object side and a negative meniscus lens L312 with a concave surface facing the object side. The aperture stop S is disposed on the image side of the second lens group G2 (between the second lens group G2 and the third lens group G3). Among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the biconvex positive lens L19.

[0150] In this optical system OL5, focusing from an infinite distance to a close object is performed by moving the second lens group G2 in the image plane direction.

[0151] The following Table 13 lists the values of the specifications of the optical system OL5.

[0152] (Table 13) Fifth Embodiment [Overall Specifications] f = 779.93334 FNO = 6.4201 ω[°]= 1.56305 Y = 21.6 TL = 393.4548 BF = 63.44872 [Lens Data] m r d nd νd Object plane ∞ 1 228.0072 10.6000 1.487490 70.32 2 3048.3506 0.2000 3 118.0101 15.0000 1.437001 95.10 4 443.8711 66.0687 5 130.0360 7.0000 1.516800 64.13 6 142.9490 0.2000 1.529500 36.27 7# 142.9490 0.3000 1.549800 50.91 8 142.9490 9.1685 9 306.0027 2.2000 1.834000 37.18 10 63.6978 11.7000 1.518600 69.89 11 -951.1005 3.0000 12 95.7831 9.4000 1.518600 69.89 13 -169.4233 2.2000 1.834000 37.18 14 157.8539 28.9675 15 -307.2847 2.1000 1.804000 46.60 16 104.5358 4.5000 1.805180 25.45 17 -292.1429 d1 18 2622.8877 1.2000 1.497820 82.57 19 78.5937 d2 20 0.0000 6.1329 Aperture stop S 21 -3223.9611 3.0000 1.883000 40.69 22 38.4921 4.1000 1.720467 34.71 23 -105.4185 3.4242 24 -258.2146 1.2000 1.593190 67.90 25 42.3067 4.2000 26 -81.0825 1.2000 1.593190 67.90 27 38.5510 4.4000 1.717360 29.57 28 -735.4086 3.2000 29 39.2389 7.9000 1.552981 55.07 30 -57.5685 3.0000 1.805180 25.45 31 -272.9721 19.7309 32 63.7192 8.0000 1.737999 32.33 33 -36.6300 2.5000 1.883000 40.69 34 34.0088 2.0000 35 37.8029 7.3000 1.654115 39.68 36 -183.6449 10.0000 37 -114.0641 6.1000 1.737999 32.33 38 -30.0300 2.6000 1.922860 20.88 39 -148.7894 BF Image plane ∞ [Focal length of lens group] Focal length of the starting surface of the lens group First lens group G1 1 265.9 Second lens group G2 18 -162.8 Third lens group G3 20 -195.1

[0153] In this optical system OL5, the seventh surface is a diffractive optical surface. Table 14 below shows the diffractive optical surface data, namely the values of the design wavelength λ0, the order n, and the phase coefficients C2 and C4 for each position.

[0154] (Table 14) [Diffractive optical surface data] m λ0 n C2 C4 7 587.6 1.0 -3.93586E-05 -5.57153E-10

[0155] In addition, in this optical system OL5, the axial air interval d0 between the object and the first lens group G1, the axial air interval d1 between the first lens group G1 and the second lens group G2, and the axial air interval d2 between the second lens group G2 and the aperture stop S change during focusing. The following Table 15 shows the variable intervals at infinity focus and close focus.

[0156] (Table 15) [Variable interval data] Focus state Infinity Close distance f 779.93334 - β - -0.16874 d0 ∞ 4606.5452 d1 6.00000 29.93769 d2 50.19530 26.25760 BF 63.44872 63.44872

[0157] The aberration diagrams such as the spherical aberration diagram, astigmatism diagram, distortion aberration diagram, longitudinal chromatic aberration diagram, and coma aberration diagram of this optical system OL5 at infinity focus and close focus are shown in FIG. 10. From these aberration diagrams, it can be seen that the various aberrations of this optical system OL5 are well corrected.

[0158] [Sixth Embodiment] FIG. 11 is a diagram showing the configuration of an optical system OL6 according to the sixth embodiment. This optical system OL6 is composed of a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power, in order from the object side. The rear group GL is composed of a third lens group G3.

[0159] The first lens group G1 is composed of, in order from the object side, a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object side, a diffractive optical element Lpf provided with a PF element Epf on the lens surface on the image side of a positive meniscus lens L13 with its convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L14 and a biconcave negative lens L15, a positive meniscus lens L16 with its convex surface facing the object side, and a cemented lens formed by cementing a biconcave negative lens L17 and a biconvex positive lens L18. The second lens group G2 is composed of a negative meniscus lens L21 with its convex surface facing the object side. The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L31 and a biconvex positive lens L32, a biconcave negative lens L33, a cemented lens formed by cementing a biconcave negative lens L34 and a positive meniscus lens L35 with its convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L36 and a biconcave negative lens L37, a cemented lens formed by cementing a biconcave negative lens L38 and a biconvex positive lens L39, a cemented lens formed by cementing a biconvex positive lens L310 and a biconcave negative lens L311, and a cemented lens formed by cementing a biconvex positive lens L312 and a biconcave negative lens L313. The aperture stop S is disposed on the image side of the second lens group G2 (between the second lens group G2 and the third lens group G3). Among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the biconvex positive lens L18.

[0160] In this optical system OL6, focusing from an infinite distance to a close object is performed by moving the second lens group G2 in the direction of the image plane.

[0161] The values of the specifications of the optical system OL6 are listed in Table 16 below. In the lens data shown in Table 16, the 14th surface is a virtual surface and is not shown in FIG. 11.

[0162] (Table 16) Sixth Embodiment [Overall Specifications] f = 779.99933 FNO = 6.41999 ω[°]= 1.56363 Y = 21.6 TL = 393.4547 BF = 74.56937 [Lens Data] m r d nd νd Object plane ∞ 1 488.6452 7.9000 1.487490 70.32 2 -1584.8559 0.2000 3 136.4730 13.4000 1.487490 70.32 4 465.0973 89.1101 5 114.2433 7.0000 1.516800 64.13 6 154.1141 0.1000 1.529500 36.27 7# 154.1141 0.2500 1.549800 50.91 8 154.1141 5.0000 9 94.8010 8.9096 1.487490 70.32 10 -2064.0654 2.3000 1.903660 31.27 11 65.7160 2.5000 12 66.1740 9.5854 1.497820 82.57 13 2165.2785 0.0000 14 0.0000 17.5002 15 -277.4112 2.0000 1.667550 41.87 16 70.4454 7.5446 1.663820 27.35 17 -263.5468 d1 18 523.4497 1.2000 1.487490 70.32 19 94.5055 d2 20 0.0000 6.7123 Aperture stop S 21 -393.7363 1.2000 2.001000 29.12 22 43.8736 2.9870 1.730371 32.23 23 -94.2293 3.3713 24 -288.4503 1.2000 1.772500 49.62 25 45.6878 3.0157 26 -164.6808 1.2000 1.627496 59.24 27 35.6904 3.4759 1.795040 28.69 28 248.6215 3.4478 29 33.0750 7.7564 1.612660 44.46 30 -36.1356 1.8000 1.593190 67.90 31 720.1003 3.0000 32 -89.4524 1.8000 1.953750 32.33 33 33.3333 6.2498 1.612930 36.94 34 -55.1763 4.5000 35 59.9212 6.8358 1.730371 32.23 36 -36.3245 1.8000 1.772500 49.62 37 33.3333 3.0000 38 39.9579 10.7333 1.850000 27.03 39 -35.6438 1.8000 1.945944 17.98 40 166.9500 BF Image plane ∞ [Focal length of lens group] Focal length of the starting surface of the lens group First lens group G1 1 237.1 Second lens group G2 18 -236.8 Third lens group G3 20 -105.9

[0163] In this optical system OL6, the seventh surface is a diffractive optical surface. Table 17 below shows the diffractive optical surface data, namely the design wavelength λ0, the order n, and the values of the phase coefficients C2 and C4 for each position.

[0164] (Table 17) [Diffractive optical surface data] m λ0 n C2 C4 7 587.6 1.0 -4.02091E-05 -2.29061E-10

[0165] Also, in this optical system OL6, the axial air interval d0 between the object and the first lens group G1, the axial air interval d1 between the first lens group G1 and the second lens group G2, and the axial air interval d2 between the second lens group G2 and the aperture stop S change during focusing. The following Table 18 shows the variable intervals at infinity focus and close focus.

[0166] (Table 18) [Variable interval data] Focus state Infinity Close distance f 779.99933 - β - -0.16674 d0 ∞ 4606.5453 d1 6.00000 29.75122 d2 62.50000 38.74878 BF 74.56937 74.56937

[0167] The aberration diagrams such as the spherical aberration diagram, astigmatism diagram, distortion diagram, longitudinal chromatic aberration diagram, and coma diagram of this optical system OL6 at infinity focus and close focus are shown in FIG. 12. From these aberration diagrams, it can be seen that this optical system OL6 has good aberration correction.

[0168] [Example 7] FIG. 13 is a diagram showing the configuration of an optical system OL7 according to the seventh embodiment. This optical system OL7 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power. The rear group GL is composed of, in order from the object side, a third lens group G3 having a negative refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power.

[0169] The first lens group G1 is composed of, in order from the object side, a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object side, a diffractive optical element Lpf provided with a PF element Epf on the image-side lens surface of a positive meniscus lens L13 with its convex surface facing the object side, a cemented lens formed by cementing a negative meniscus lens L14 with its convex surface facing the object side and a positive meniscus lens L15 with its convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L16 and a biconcave negative lens L17, and a cemented lens formed by cementing a biconcave negative lens L18 and a biconvex positive lens L19. The second lens group G2 is composed of a negative meniscus lens L21 with its convex surface facing the object side. The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L31 and a biconvex positive lens L32. The fourth lens group G4 is composed of a biconvex positive lens L41. The fifth lens group G5 is composed of a biconcave negative lens L51, a cemented lens formed by cementing a biconcave negative lens L52 and a positive meniscus lens L53 with its convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L54 and a negative meniscus lens L55 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L56 and a biconcave negative lens L57, a biconvex positive lens L58, and a cemented lens formed by cementing a positive meniscus lens L59 with its concave surface facing the object side and a negative meniscus lens L510 with its concave surface facing the object side. The aperture stop S is disposed on the image side of the second lens group G2 (between the second lens group G2 and the third lens group G3). Among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the biconvex positive lens L19.

[0170] In this optical system OL7, focusing from an infinite distance to a near-distance object is performed by moving the second lens group G2 in the image plane direction and moving the fourth lens group G4 in the object direction.

[0171] The following Table 19 lists the values of the specifications of the optical system OL7. Note that the rear group GR in the lens group focal length is the value at infinite focus.

[0172] (Table 19) Seventh Embodiment [Overall Specifications] f = 779.91908 FNO = 6.4199 ω[°]= 1.58017 Y = 21.6 TL = 393.3977 BF = 51.39765 [Lens Data] m r d nd νd Object plane ∞ 1 424.3476 8.3660 1.487490 70.32 2 -1652.1838 0.2000 3 105.5654 15.9140 1.437001 95.10 4 319.2044 75.8188 5 114.0000 7.0000 1.516800 64.13 6 154.0000 0.2000 1.529500 36.27 7# 154.0000 0.3000 1.549800 50.91 8 154.0000 11.0246 9 261.9525 2.2658 1.903660 31.27 10 122.0744 6.0040 1.518600 69.89 11 1366.9052 3.0060 12 76.1365 10.1384 1.518600 69.89 13 -158.3236 2.5000 1.902650 35.77 14 87.1741 32.6651 15 -122.0270 2.0000 1.816000 46.59 16 361.4186 3.4772 1.808090 22.74 17 -127.0101 d1 18 215.9032 1.2000 1.497820 82.57 19 79.3475 d2 20 0.0000 5.6136 Aperture Stop S 21 -112.9018 1.2000 1.883000 40.69 22 63.7923 3.0550 1.603420 38.03 23 -69.3917 d3 24 79.5932 2.3590 1.552981 55.07 25 -450.0840 d4 26 -1062.0041 1.2000 1.772500 49.62 27 38.6281 4.3403 28 -94.0940 1.2000 1.627496 59.24 29 37.5442 4.1672 1.808090 22.74 30 473.5817 3.3752 31 40.0000 6.1265 1.552981 55.07 32 -68.3848 1.5000 1.808090 22.74 33 -1055.9517 11.9061 34 67.5522 7.2276 1.737999 32.33 35 -44.5483 2.0000 1.883000 40.69 36 40.0000 2.1173 37 45.3449 7.0622 1.737999 32.33 38 -89.9302 15.0000 39 -54.7362 5.0820 1.788800 28.43 40 -26.7010 2.0000 1.945944 17.98 41 -103.9165 BF Image plane ∞ [Focal length of lens group] Focal length of the starting surface of the lens group First lens group G1 1 330.6 Second lens group G2 18 -252.7 Rear group GR 20 -190.4 Third lens group G3 20 -304.5 Fourth lens group G4 24 122.5 Fifth lens group G5 26 -94.6

[0173] In this optical system OL7, the seventh surface is a diffractive optical surface. Table 20 below shows the diffractive optical surface data, i.e., the values of the design wavelength λ0, the order n, and the phase coefficients C2 and C4 for each position.

[0174] (Table 20) [Diffractive optical surface data] m λ0 n C2 C4 7 587.6 1.0 -3.90875E-05 -6.61767E-10

[0175] Also, in this optical system OL7, the axial air gap d0 between the object and the first lens group G1, the axial air gap d1 between the first lens group G1 and the second lens group G2, the axial air gap d2 between the second lens group G2 and the aperture stop S, the axial air gap d3 between the third lens group G3 and the fourth lens group G4, and the axial air gap d4 between the fourth lens group G4 and the fifth lens group G5 change during focusing. Table 21 below shows the variable intervals at infinity focus and close focus.

[0176] (Table 21) [Variable interval data] Focus state Infinity Close distance f 585.00017 - β - -0.16536 d0 ∞ 4606.6023 d1 7.44308 50.07294 d2 50.75570 8.12583 d3 8.45431 2.99768 d4 6.73510 12.19172 BF 51.39765 51.39765

[0177] Figs. 14 show various aberration diagrams of the optical system OL7, namely spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, chromatic aberration of magnification diagrams, and coma aberration diagrams, when focusing at infinity and at close range. From these respective aberration diagrams, it can be seen that the optical system OL7 has its various aberrations well corrected.

[0178] [Eighth Embodiment] Fig. 15 is a diagram showing the configuration of an optical system OL8 according to the eighth embodiment. This optical system OL8 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear group GL having a negative refractive power. Further, the rear group GL is composed of a third lens group G3.

[0179] The first lens group G1 is composed of, in order from the object side, an aspherical positive lens L11 having a biconvex shape with an aspherical shape formed on the lens surface on the object side and the lens surface on the image side, a diffractive optical element Lpf provided with a PF element Epf on the lens surface on the image side of a positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L13 and a biconcave negative lens L14, and a cemented lens formed by cementing a negative meniscus lens L15 with a convex surface facing the object side and a biconvex positive lens L16. Further, the second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side. Further, the third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L31 and a biconcave negative lens L32, a biconcave negative lens L33, a cemented lens formed by cementing a biconvex positive lens L34 and a biconcave negative lens L35, a cemented lens formed by cementing a negative meniscus lens L36 with a convex surface facing the object side and a biconvex positive lens L37, a cemented lens formed by cementing a biconcave negative lens L38 and a positive meniscus lens L39 with a convex surface facing the object side, and a positive meniscus lens L310 with a convex surface facing the object side. Further, the aperture stop S is disposed on the object side of the second lens group G2 (between the first lens group G1 and the second lens group G2). Further, among the positive lenses included in the first lens group G1, the positive lens having the smallest Abbe number with respect to the d-line of the medium is the biconvex positive lens L16.

[0180] In this optical system OL8, focusing from infinity to a close - distance object is achieved by moving the second lens group G2 in the image plane direction.

[0181] The following Table 22 lists the values of the specifications of the optical system OL8. Note that in the lens data shown in Table 22, the 16th surface is a virtual surface and is not shown in FIG. 15.

[0182] (Table 22) Eighth Embodiment [Overall Specifications] f = 390.019 FNO = 4.600 ω[°]= 3.14 Y = 21.6 TL = 247.546 BF = 45.26893 [Lens Data] m r d nd νd Object plane ∞ 1* 112.6999 11.4142 1.487490 70.32 2* -804.3009 76.3821 3 68.8075 4.7100 1.516800 64.13 4 158.5341 0.1000 1.528300 36.18 5# 158.5341 0.2500 1.548900 51.30 6 158.5341 15.1436 7 66.3631 4.6902 1.487490 70.32 8 -320.7208 1.2000 1.846660 23.80 9 58.0531 18.7361 10 85.2798 1.1000 1.900430 37.37 11 40.5271 4.0337 1.663820 27.35 12 -284.0294 3.0000 13 0.0000 d1 Aperture Stop S 14 121.7747 1.0000 1.581440 40.98 15 30.8413 d2 16 0.0000 0.4000 17 56.7050 4.0000 1.603420 38.03 18 -34.3098 1.0000 1.593490 67.00 19 41.4738 1.8000 20 -31189.2380 1.0000 1.900430 37.37 21 56.5306 1.5000 22 27.8447 6.8000 1.581440 40.98 23 -22.6989 1.0000 1.593190 67.90 24 33.3615 2.9413 25 50.2032 1.0000 1.945944 17.98 26 20.4619 7.4000 1.770470 29.74 27 -41.9379 1.5000 28 -41.1217 1.0000 1.900430 37.37 29 24.9456 4.2000 1.770470 29.74 30 106.7270 0.2000 31 42.9809 3.4000 1.770470 29.74 32 355.9859 BF Image plane ∞ [Focal length of lens group] Focal length of the starting surface of the lens group First lens group G1 1 147.0 Second lens group G2 14 -71.3 Third lens group G3 17 -224.8

[0183] In this optical system OL8, the fifth surface is a diffractive optical surface. Table 23 below shows the diffractive optical surface data, that is, the values of the design wavelength λ0, the order n, and the phase coefficients C2 and C4 for each position.

[0184] (Table 23) [Diffractive optical surface data] m λ0 n C2 C4 5 587.6 1.0 -1.14484E-04 3.49966E-09

[0185] In this optical system OL8, each lens surface of the first surface and the second surface is formed in an aspherical shape. Table 24 below shows the surface number m and the aspherical data, that is, the values of the conic constant K and the aspherical coefficients A4 to A10 for each position.

[0186] (Table 24) [Aspherical data] m K A4 A6 A8 A10 1 1.000 -2.56030E-08 -7.13730E-13 0.00000E+00 0.00000E+00 2 1.000 3.78499E-08 -7.98960E-14 0.00000E+00 0.00000E+00

[0187] Also, in this optical system OL8, the axial air interval d0 between the object and the first lens group G1, the axial air interval d1 between the first lens group G1 and the second lens group G2, and the axial air interval d2 between the second lens group G2 and the aperture stop S change during focusing. Table 25 below shows the variable intervals at infinity focus and close-focus.

[0188] (Table 25) [Variable interval data] Focus state Infinity Close distance f 390.01858 - β - -0.16368 d0 ∞ 2250.1757 d1 3.00000 16.36518 d2 18.37538 5.00920 BF 45.26893 45.26893

[0189] The aberration diagrams such as the spherical aberration diagram, the astigmatism diagram, the distortion aberration diagram, the chromatic aberration of magnification diagram, and the coma aberration diagram of this optical system OL8 at infinity focus and close focus are shown in FIG. 16. From these aberration diagrams, it can be seen that this optical system OL8 has good correction of various aberrations.

[0190] [Conditional formula corresponding value] The corresponding values of the conditional formulas (1) to (15) in the first to eighth embodiments are shown in Table 26 below.

[0191] (Table 26) (1) TL / f (2) θgFp1 (3) TLpf / TL (4) d1 / dG1 (5) TLs / TL (6) -fr / f (7) νdp1 (8) d1 / TL (9) f1 / f (10) -f2 / f (11) dpf / TL (12) fpf / f (13) dL1L2 / TL (14) θgfp1 + 0.00316 × νdp1 (15) ndp1 First Embodiment Second Embodiment Third Embodiment Fourth Embodiment fpf 10075.749 10987.441 11410.445 11184.031 θgFp1 0.6291 0.6319 0.6288 0.6319 TLpf 67.779 70.749 90.496 108.078 TLs 126.502 145.000 235.494 240.968 d1 37.897 46.349 58.158 79.080 dG1 122.427 141.000 167.364 172.956 dpf 37.897 46.349 58.158 79.080 dL1L2 22.682 17.200 25.138 21.898 (1) 0.529 0.532 0.419 0.419 (2) 0.6291 0.6319 0.6288 0.6319 (3) 0.219 0.227 0.216 0.258 (4) 0.310 0.329 0.347 0.457 (5) 0.409 0.466 0.562 0.574 (6) 0.252 0.399 0.161 0.092 (7) 24.71 27.35 22.74 27.35 (8) 0.122 0.149 0.139 0.189 (9) 0.352 0.371 0.321 0.257 (10) 0.313 0.230 0.245 0.233 (11) 0.122 0.149 0.139 0.189 (12) 17.223 18.782 11.410 11.184 (13) 0.073 0.055 0.060 0.052 (14) 0.707 0.718 0.701 0.718 (15) 1.756 1.664 1.808 1.664 Example 5 Example 6 Example 7 Example 8 fpf 12703.704 12434.996 12791.813 4367.423 θgFp1 0.6157 0.6319 0.6288 0.6319 TLpf 99.069 117.710 107.499 92.606 TLs 230.000 243.000 240.279 140.760 d1 66.069 89.110 75.819 76.382 dG1 172.605 173.300 180.880 137.760 dpf 66.069 89.110 75.819 76.382 dL1L2 25.800 21.500 24.480 11.412 (1) 0.504 0.504 0.504 0.635 (2) 0.6157 0.6319 0.6288 0.6319 (3) 0.252 0.299 0.273 0.374 (4) 0.383 0.514 0.419 0.554 (5) 0.585 0.618 0.611 0.569 (6) 0.250 0.136 0.244 0.576 (7) 25.45 27.35 22.74 27.35 (8) 0.168 0.226 0.193 0.309 (9) 0.341 0.304 0.424 0.377 (10) 0.209 0.304 0.324 0.183 (11) 0.168 0.226 0.193 0.309 (12) 16.288 15.942 16.401 11.198 (13) 0.066 0.055 0.062 0.046 (14) 0.696 0.718 0.701 0.718 (15) 1.805 1.664 1.808 1.664

Explanation of Symbols

[0192] 1 Camera (Optical Device) OS (OS1~OS8) Optical System G1 First Lens Group G2 Second Lens Group GR Rear Group G3 Third Lens Group G4 Fourth Lens Group G5 Fifth Lens Group Lpf Diffractive Optical Element S Aperture Stop

Claims

1. It consists of a plurality of lens groups, When focusing, the distance between adjacent lens groups changes, When focusing, one or two lens groups move, The plurality of lens groups are, in order from the object side, A first lens group having a diffractive optical element and being fixed with respect to the image plane when focusing, A second lens group that moves when focusing, And a rear group having at least one lens group, The first lens group has a positive lens on the most object side, An optical system that satisfies the conditions of the following formula. 0.40 < TL / f < 0.65 0.05 < -fr / f < 2.50 0.20 < -f2 / f < 0.40 However, TL: The overall length of the optical system when focused at infinity f: The focal length of the entire optical system when focused at infinity fr: The focal length of the rear group when focused at infinity f2: The focal length of the second lens group

2. It consists of a plurality of lens groups, When focusing, the distance between adjacent lens groups changes, When focusing, one or two lens groups move, The plurality of lens groups are, in order from the object side, A first lens group having a diffractive optical element and being fixed with respect to the image plane when focusing, A second lens group that moves when focusing, And a rear group having at least one lens group, The first lens group has a positive lens on the most object side, The first lens group has two positive lenses arranged on the object side of the diffractive optical element, An optical system that satisfies the conditions of the following formula. 0.40 < TL / f < 0.65 0.05 < -fr / f < 2.50 However, TL: The overall length of the optical system when focused at infinity f: The focal length of the entire optical system when focused at infinity fr: The focal length of the rear group when focused at infinity

3. The first lens group has two positive lenses arranged on the object side of the diffractive optical element The optical system according to claim 1.

4. The optical system according to claim 2, satisfying the conditions of the following formula 0.15 < -f2 / f < 0.40 However, f2: The focal length of the second lens group f: The focal length of the entire optical system when focused at infinity

5. The optical system according to any one of claims 1 to 4, satisfying the conditions of the following formula 0.10 < TLpf / TL < 0.40 However, TLpf: The distance on the optical axis from the lens surface closest to the object of the optical system to the diffractive optical surface provided by the diffractive optical element when focused at infinity TL: The overall length of the optical system when focused at infinity

6. The diffractive optical element is arranged on the object side of the negative lens component closest to the object The optical system according to any one of claims 1 to 5.

7. The first lens group has a positive refractive power The optical system according to any one of claims 1 to 6.

8. The diffractive optical element has two diffractive element elements made of different optical materials, and the two diffractive element elements are joined to each other, and a diffractive optical surface is formed on the joint surface of the diffractive element elements The optical system according to any one of claims 1 to 7.

9. The diffractive optical element has a lens component, and one of the two diffractive element elements is joined to a lens surface on the object side or the image side of the lens component. The optical system according to claim 8.

10. In the diffractive optical element, one of the two diffractive element elements is in contact with air. The optical system according to claim 8.

11. The optical system according to any one of claims 1 to 10, satisfying the condition of the following formula. 12.0 < νdp1 < 32.0 However, νdp1: The Abbe number of the positive lens having the smallest Abbe number with respect to the d-line of the medium within the first lens group

12. The optical system according to any one of claims 1 to 11, satisfying the condition of the following formula. 0.10 < d1 / TL < 0.31 However, d1: The maximum value of the air intervals on the optical axis within the first lens group TL: The overall length of the optical system at infinity focus

13. The optical system according to any one of claims 1 to 12, satisfying the condition of the following formula. 0.20 < f1 / f < 0.50 However, f1: The focal length of the first lens group f: The overall focal length of the optical system at infinity focus

14. The optical system according to any one of claims 1 to 13, satisfying the condition of the following formula. 0.10 < dpf / TL < 0.31 However, dpf: The air interval on the optical axis between the lens disposed on the object side adjacent to the diffractive optical element TL: The overall length of the optical system at infinity focus

15. The optical system according to any one of Claims 1 to 14, satisfying the conditions of the following formula. 8.0 < fpf / f < 22.0 However, fpf: The focal length of the diffractive optical surface of the diffractive optical element f: The overall focal length of the entire optical system when focused at infinity

16. The first lens group has two positive lenses on the object side of the largest air interval among the air intervals on the optical axis within the first lens group. The optical system according to any one of Claims 1 to 15.

17. The optical system according to any one of Claims 1 to 15, satisfying the conditions of the following formula. dL1L2 / TL < 0.080 However, dL1L2: The distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the lens group on the object side of the largest air interval within the first lens group. TL: The overall length of the optical system when focused at infinity

18. An aperture stop is provided on the object side of the second lens group. The optical system according to any one of Claims 1 to 17.

19. An aperture stop is provided on the image side of the second lens group. The optical system according to any one of Claims 1 to 17.

20. The optical system according to any one of Claims 1 to 19, satisfying the conditions of the following formula. θgFp1 + 0.00316 × νdp1 > 0.706 However, θgFp1: The partial dispersion ratio of the medium of the positive lens having the smallest Abbe number with respect to the d-line of the medium within the first lens group. νdp1: The Abbe number of the positive lens having the smallest Abbe number with respect to the d-line of the medium within the first lens group.

21. The lens disposed on the object side of the largest air interval among the air intervals on the optical axis within the first lens group consists of one positive lens. The optical system according to any one of Claims 1 to 20.

22. The second lens group has a negative refractive power. The optical system according to any one of Claims 1 to 21.

23. The rear group has a lens group that moves during focusing. The optical system according to any one of Claims 1 to 22.

24. The rear group, in order from the object side, a third lens group, a fourth lens group that moves during focusing, and a fifth lens group. The optical system according to any one of Claims 1 to 23.

25. The optical system according to any one of Claims 1 to 24 that satisfies the conditions of the following formula. ndp1 < 1.810 However, ndp1: The refractive index of the medium for the d-line of the positive lens having the smallest Abbe number for the d-line of the medium within the first lens group.

26. An optical device having the optical system according to any one of Claims 1 to 25.

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