Optical system, optical device, and method for manufacturing optical system

Abstract

The invention provides an optical system capable of obtaining good optical performance, an optical apparatus provided with the optical system, and a method for manufacturing the optical system. An optical system (OL1) used in an optical device such as a camera (1) is configured from, in order from the object side, an objective optical system (GO) and an imaging optical system (GI) for imaging an intermediate image (IM) imaged by the objective optical system (GO), and the optical system (OL1) is configured so as to satisfy the following condition: 0.40 < fo / f < 0.80 (where fo is the focal length of the objective optical system (GO), f is the focal length of the objective optical system (GO), and f is the focal length of the objective optical system (GO). F is the focal length of the entire optical system (OL).

Description

Technical Field

[0001] The present invention relates to an optical system, an optical device and a method for manufacturing the optical system. Background Art

[0002] Conventionally, an optical system for photographing a tiny subject or a narrow space has been proposed (for example, see Patent Document 1). However, further improvement in optical performance is required.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-133571 Summary of the invention

[0006] The optical system according to the first aspect of the present invention is composed of an objective optical system and an imaging optical system in order from the object side, the imaging optical system forms an intermediate image formed by the objective optical system, and the optical system satisfies the following condition: 0.40<fo / f<0.80 in, fo: focal length of the objective optical system, f: The focal length of the entire optical system.

[0007] The optical system involved in the second aspect of the present invention is composed of an objective optical system, a relay optical system and an imaging optical system in order from the object side, the relay optical system forms an image of a first intermediate image formed by the objective optical system, the imaging optical system forms an image of a second intermediate image formed by the relay optical system, and when the magnification is changed, the interval between adjacent lens groups of the imaging optical system changes, and the optical system satisfies the following condition: 1.50<|fmin| / fr2<8.00 in, fmin: The focal length of the lens group with the smallest absolute focal length among the lens groups that move when changing magnification. fr2: focal length of the imaging optical system in the wide-angle end state.

[0008] A first aspect of the present invention relates to a method for manufacturing an optical system, wherein the optical system is composed of an objective optical system and an imaging optical system in order from the object side, the imaging optical system forms an intermediate image formed by the objective optical system, wherein the imaging optical system is configured in a manner that satisfies the following condition: 0.40<fo / f<0.80 in, fo: focal length of the objective optical system, f: The focal length of the entire optical system.

[0009] A second aspect of the present invention relates to a method for manufacturing an optical system, wherein the optical system is composed of an objective optical system, a relay optical system, and an imaging optical system in order from the object side, wherein the relay optical system forms an image of a first intermediate image formed by the objective optical system, and the imaging optical system forms an image of a second intermediate image formed by the relay optical system, wherein the imaging optical system is arranged in such a manner that the intervals between adjacent lens groups change when the magnification is changed, and in such a manner that the following condition is satisfied: 1.50<|fmin| / fr2<8.00 in, fmin: The focal length of the lens group with the smallest absolute focal length among the lens groups that move when changing magnification. fr2: focal length of the imaging optical system in the wide-angle end state. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a cross-sectional view showing the lens structure of the optical system involved in Example 1-1.

[0011] Figure 2 1-1 are diagrams of various aberrations when the optical system according to Example 1 is focused at infinity.

[0012] Figure 3 It is a cross-sectional view showing the lens structure of the optical system involved in Example 1-2.

[0013] Figure 4 These are diagrams of various aberrations of the optical system according to Example 1-2 when focusing at infinity.

[0014] Figure 5 It is a cross-sectional view showing the lens structure of the optical system involved in the first to third embodiments.

[0015] Figure 6 These are various aberration diagrams of the optical system involved in Examples 1 to 3 when focusing at infinity.

[0016] Figure 7 1 and 1 are cross-sectional views showing the lens structure of the optical system according to Example 2-1, wherein (a) shows the object side of the second intermediate image, and (b) shows the image plane side of the second intermediate image.

[0017] Figure 8 1 and 10 are diagrams of various aberrations of the optical system according to Example 2-1 when focusing at infinity, wherein (a) shows the wide-angle end state and (b) shows the telephoto end state.

[0018] Fig. 92 is a cross-sectional view showing the lens structure of the optical system involved in Example 2-2, (a) shows the object side of the second intermediate image, and (b) shows the image plane side of the second intermediate image.

[0019] Fig.10 1 and 12 are diagrams of various aberrations of the optical system according to Example 2-2 when focusing at infinity, wherein (a) shows the wide-angle end state and (b) shows the telephoto end state.

[0020] Fig.11 1 and 1 are cross-sectional views showing the lens structure of the optical system according to Example 2-3, wherein (a) shows the object side of the second intermediate image, and (b) shows the image plane side of the second intermediate image.

[0021] Fig.12 1 and 10 are diagrams of various aberrations of the optical system according to Example 2-3 when focusing at infinity, wherein (a) shows the wide-angle end state and (b) shows the telephoto end state.

[0022] Fig.13 It is a cross-sectional view of a camera equipped with the optical system of the first embodiment or the second embodiment.

[0023] Fig.14 This is a flowchart for explaining the method for manufacturing the optical system according to the first embodiment.

[0024] Fig.15 This is a flowchart for explaining the method for manufacturing the optical system according to the second embodiment. DETAILED DESCRIPTION

[0025] Hereinafter, preferred embodiments will be described with reference to the drawings.

[0026] (First embodiment)

[0027] like Figure 1 As shown, the optical system OL1 according to the first embodiment is composed of an objective optical system GO and an imaging optical system GI in order from the object side, and the imaging optical system GI forms an intermediate image IM formed by the objective optical system GO. With this configuration, good optical performance can be obtained.

[0028] In addition, it is preferable that the optical system OL1 according to the first embodiment satisfies the following conditional expression (1-1).

[0029] 0.40<fo / f<0.80 (1-1) in, fo: focal length of objective optical system GO f: Focal length of the entire optical system OL1 (when focusing on an object at infinity)

[0030] Conditional formula (1-1) specifies the ratio of the focal length of the objective optical system GO to the focal length of the entire system of the optical system OL1. By satisfying the conditional formula (1-1), the lens diameter on the object side of the optical system OL1 can be reduced. If it is lower than the lower limit of the conditional formula (1-1), the focal length of the objective optical system GO becomes stronger, and the correction of off-axis aberrations such as coma and astigmatism becomes difficult, so it is not preferred. In addition, in order to make the effect of the conditional formula (1-1) reliable, it is more preferred to set the lower limit of the conditional formula (1-1) to 0.42, 0.45, 0.48, and further to 0.50. In addition, if it exceeds the upper limit of the conditional formula (1-1), the focal length of the imaging optical system GI becomes stronger, and the correction of spherical aberration and image curvature becomes difficult, so it is not preferred. In addition, in order to make the effect of the conditional formula (1-1) reliable, it is more preferred to set the upper limit of the conditional formula (1-1) to 0.78, 0.75, 0.72, and further to 0.70.

[0031] In addition, it is preferable that the optical system OL1 according to the first embodiment has one intermediate image IM. According to this configuration, the overall length of the optical system OL1 can be shortened while suppressing the lens diameter on the object side.

[0032] In the optical system OL1 according to the first embodiment, it is preferred that the imaging optical system GI has at least two focusing groups (a first movable group G1 and a second movable group G2), and the intervals between adjacent lens groups change during focusing. According to this structure, the change of the field curvature during focusing of the optical system OL1 can be reduced.

[0033] The optical system OL1 according to the first embodiment is preferably configured to focus on an infinitely distant object by moving the focus group (the first movable group G1 and the second movable group G2) along the optical axis during focusing. With this configuration, the optical system OL1 can be used as a photographic lens.

[0034] In addition, it is preferable that the optical system OL1 according to the first embodiment satisfies the following conditional expression (1-2).

[0035] 0.15<fa / fr<0.80 (1-2) in, fa: Focal length of the optical system (first fixed group GA) located on the object side relative to the focus group (first movable group G1) located closest to the object in the imaging optical system GI fr: Focal length of the imaging optical system GI (when focusing on an object at infinity)

[0036] Conditional expression (1-2) specifies the ratio of the focal length of the optical system (1st fixed group GA) located on the object side compared to the focusing group (1st movable group G1) located closest to the object side in the imaging optical system GI, relative to the focal length of the imaging optical system GI. By satisfying this conditional expression (1-2), good optical performance can be obtained. If it is lower than the lower limit value of the conditional expression (1-2), the optical focal length of the first fixed group GA becomes stronger, and it becomes difficult to correct the axial chromatic aberration, so it is not preferred. In addition, in order to make the effect of this conditional expression (1-2) reliable, it is more preferred to set the lower limit value of the conditional expression (1-2) to 0.16, 0.18, and further to 0.20. In addition, if it exceeds the upper limit value of the conditional expression (1-2), the optical focal length of the imaging optical system GI becomes stronger, and it becomes difficult to correct the spherical aberration and the field curvature, so it is not preferred. In order to ensure the effect of the conditional expression (1-2), it is more preferable to set the upper limit value of the conditional expression (1-2) to 0.78, 0.75, 0.72, and further to 0.70.

[0037] In addition, it is preferable that the optical system OL1 according to the first embodiment satisfies the following conditional expression (1-3).

[0038] 0.10<TLo / TL<0.30 (1-3) in, TLo: The distance on the optical axis from the lens surface closest to the object side of the objective optical system GO to the intermediate image IM TL: Total optical length of optical system OL1 (when focusing on an object at infinity)

[0039] Conditional formula (1-3) specifies the ratio of the distance on the optical axis from the lens surface closest to the object side of object optical system GO to the intermediate image IM (the optical total length of object optical system GO) relative to the optical total length of optical system OL1. By satisfying this conditional formula (1-3), the reduction of the performance degradation caused by manufacturing error and the miniaturization of lens barrel can be taken into account. If lower than the lower limit of conditional formula (1-3), the focal length of object optical system GO becomes stronger, and the performance reduction caused by manufacturing error becomes larger, so it is not preferred. In addition, in order to make the effect of this conditional formula (1-3) reliable, it is more preferred that the lower limit of conditional formula (1-3) is set to 0.11, 0.12, 0.13, 0.14, further set to 0.15. In addition, if it exceeds the upper limit of conditional formula (1-3), the focal length of object optical system GO becomes weaker, and the small-diameterization of optical system OL1 becomes difficult, so it is not preferred. In order to ensure the effect of the conditional expression (1-3), it is more preferable to set the upper limit value of the conditional expression (1-3) to 0.29, 0.27, or further to 0.25.

[0040] In addition, it is preferable that the optical system OL1 according to the first embodiment satisfies the following conditional expression (1-4).

[0041] 0.30<|fb / fr|<0.80 (1-4) in, fb: Focal length of the optical system (second fixed group GB) located on the image plane side relative to the focus group (second movable group G2) located closest to the image plane in the imaging optical system GI fr: Focal length of the imaging optical system GI (when focusing on an object at infinity)

[0042] Conditional expression (1-4) specifies the ratio of the focal length of the optical system (second fixed group GB) located on the image plane side compared to the focusing group (second movable group G2) located closest to the image plane in the imaging optical system GI, relative to the focal length of the imaging optical system GI. By satisfying this conditional expression (1-4), good optical performance can be obtained. If it is lower than the lower limit value of the conditional expression (1-4), the optical focal length of the second fixed group GB becomes stronger, and it becomes difficult to correct coma aberration, so it is not preferred. In addition, in order to make the effect of this conditional expression (1-4) reliable, it is more preferable to set the lower limit value of the conditional expression (1-4) to 0.32, 0.35, 0.38, and further to 0.40. In addition, if it exceeds the upper limit value of the conditional expression (1-4), the optical focal length of the imaging optical system GI becomes stronger, and it becomes difficult to correct spherical aberration and field curvature, so it is not preferred. In order to ensure the effect of conditional expression (1-4), it is more preferable to set the upper limit value of conditional expression (1-4) to 0.78, 0.75, 0.72, and further to 0.70.

[0043] In addition, it is preferable that the optical system OL1 according to the first embodiment satisfies the following conditional expression (1-5).

[0044] 0.10<Lsum / TLr<0.60 (1-5) in, Lsum: Total thickness of the lens of the imaging optical system GI TLr: The distance on the optical axis from the intermediate image IM to the image plane I (when focusing on an object at infinity)

[0045] Conditional formula (1-5) specifies the ratio of the total thickness of the lenses of the imaging optical system GI (the value obtained by adding up the thicknesses of all the lenses constituting the imaging optical system GI) to the distance on the optical axis from the intermediate image IM to the image plane I. By satisfying the conditional formula (1-5), good optical performance can be obtained. If it is lower than the lower limit value of the conditional formula (1-5), the number of lenses of the imaging optical system GI becomes small, and it becomes difficult to fully correct the spherical aberration and the image plane curvature, so it is not preferred. In addition, in order to make the effect of the conditional formula (1-5) reliable, it is more preferred to set the lower limit value of the conditional formula (1-5) to 0.11, and further to 0.12. In addition, if the upper limit value of the conditional formula (1-5) is exceeded, the total thickness of the glass of the imaging optical system GI becomes thicker, resulting in a decrease in the amount of light. This makes it difficult to obtain a clear image, so it is not preferred. In order to ensure the effect of the conditional expression (1-5), it is more preferable to set the upper limit value of the conditional expression (1-5) to 0.58, 0.55, 0.52, and further to 0.50.

[0046] In addition, the optical system OL1 according to the first embodiment preferably includes a diaphragm (aperture stop S) in the imaging optical system GI. According to this configuration, the diameter of the optical system OL1 can be reduced, and field curvature and distortion can be corrected well.

[0047] In the optical system OL1 according to the first embodiment, it is preferable that the lens L1 disposed most on the object side of the objective optical system GO is a spherical lens. According to this configuration, it is possible to reduce performance degradation due to manufacturing errors of the optical system OL1.

[0048] In the optical system OL1 according to the first embodiment, it is preferable that the lens L1 disposed most on the object side of the objective optical system GO has negative refractive power. According to this configuration, the field curvature and astigmatism of the optical system OL1 can be corrected well.

[0049] In addition, it is preferable that the optical system OL1 according to the first embodiment satisfies the following conditional expression (1-6).

[0050] 1.70<nL1 (1-6) in, nL1: The refractive index of the medium of the lens L1 arranged on the object side of the objective optical system GO for the d-line

[0051] The conditional expression (1-6) specifies the refractive index of the medium of the lens L1 disposed on the object side of the objective optical system GO for the d-line. By satisfying the conditional expression (1-6), the field curvature and astigmatism can be well corrected. In addition, in order to make the effect of the conditional expression (1-6) reliable, it is more preferable to set the lower limit of the conditional expression (1-6) to 1.72, 1.74, 1.76, 1.78, and further to 1.80.

[0052] In addition, it is preferable that the optical system OL1 according to the first embodiment satisfies the following conditional expression (1-7).

[0053] 0.80<ωn / ωi<1.20 (1-7) in, ωn: Half field of view of optical system OL1 when focusing on close objects ωi: Half field angle of view of optical system OL1 when focusing on an object at infinity

[0054] The conditional expression (1-7) specifies the ratio of the half field angle when a close object is focused to the half field angle when an infinitely distant object of the optical system OL1 is focused. The conditional expression (1-7) is a conditional expression about breathing. By satisfying the conditional expression (1-7), the sense of disharmony during animation photography can be reduced. In addition, in order to make the effect of the conditional expression (1-7) reliable, it is more preferable to set the lower limit value of the conditional expression (1-7) to 0.82, 0.85, 0.88, and further to 0.90. In addition, in order to make the effect of the conditional expression (1-7) reliable, it is more preferable to set the upper limit value of the conditional expression (1-7) to 1.18, 1.15, 1.12, and further to 1.10.

[0055] (Second embodiment)

[0056] like Figure 7 As shown, the optical system OL2 involved in the second embodiment is composed of an objective optical system GO, a relay optical system GR and an imaging optical system GI in order from the object side, the relay optical system GR forms an image of the first intermediate image IM1 formed by the objective optical system GO, the imaging optical system GI forms an image of the second intermediate image IM2 formed by the relay optical system GR, and when the magnification is changed, the interval between each adjacent lens group of the imaging optical system GI changes. According to this structure, good optical performance can be obtained.

[0057] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-1).

[0058] 1.50<|fmin| / fr2<8.00 (2-1) in, fmin: The focal length of the lens group with the smallest absolute focal length among the lens groups that move when the imaging optical system GI is zoomed fr2: Focal length of the imaging optical system GI at the wide-angle end (when focusing on an object at infinity)

[0059] Conditional expression (2-1) specifies the ratio of the focal length of the movable group of the lens group that moves when changing the magnification (the focal length with the smallest absolute value among these lens groups) to the focal length of the imaging optical system GI in the wide-angle end state. By satisfying this conditional expression (2-1), an optical system OL2 with a small lens diameter on the object side can be realized. If it is lower than the lower limit value of conditional expression (2-1), the optical power of the movable group of the imaging optical system GI becomes stronger, and the aberration change caused by changing the magnification becomes larger, so it is not preferred. In addition, in order to make the effect of this conditional expression (2-1) reliable, it is more preferable to set the lower limit value of conditional expression (2-1) to 1.60, 1.80, and further to 2.00. In addition, if it exceeds the upper limit value of conditional expression (2-1), the optical power of the imaging optical system GI becomes stronger, and the correction of spherical aberration and field curvature becomes difficult, so it is not preferred. In order to ensure the effect of the conditional expression (2-1), it is more preferable to set the upper limit value of the conditional expression (2-1) to 7.50, 7.00, 6.50, and further to 6.00.

[0060] In the optical system OL2 according to the second embodiment, it is preferable that the imaging optical system GI is composed of a first fixed group GA, a plurality of movable groups (for example, Figure 1 In the case of the optical system, the optical system is composed of the first to third movable groups (G1 to G3) and the second fixed group GB. The first fixed group GA is fixed relative to the image plane I when the magnification is changed, the plurality of movable groups move along the optical axis when the magnification is changed, and the second fixed group GB is fixed relative to the image plane when the magnification is changed. According to this structure, good optical performance can be obtained.

[0061] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-2).

[0062] 1.00<fa / fr2<5.00 (2-2) in, fa: Focal length of the first fixed group GA fr2: Focal length of the imaging optical system GI at the wide-angle end (when focusing on an object at infinity)

[0063] Conditional expression (2-2) specifies the ratio of the focal length of the first fixed group GA to the focal length of the imaging optical system GI in the wide-angle end state. By satisfying this conditional expression (2-2), good optical performance can be obtained. If it is lower than the lower limit value of conditional expression (2-2), the optical focal length of the first fixed group GA becomes stronger, and the correction of axial chromatic aberration becomes difficult, so it is not preferred. In addition, in order to make the effect of this conditional expression (2-2) reliable, it is more preferred to set the lower limit value of conditional expression (2-2) to 1.10, 1.20, and further to 1.30. In addition, if it exceeds the upper limit value of conditional expression (2-2), the optical focal length of the imaging optical system GI becomes stronger, and the correction of spherical aberration and field curvature becomes difficult, so it is not preferred. In addition, in order to make the effect of this conditional expression (2-2) reliable, it is more preferred to set the upper limit value of conditional expression (2-2) to 4.80, 4.50, 4.20, and further to 4.00.

[0064] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-3).

[0065] 0.80<|fb| / fr2<4.00 (2-3) in, fb: Focal length of the second fixed group GB fr2: Focal length of the imaging optical system GI at the wide-angle end (when focusing on an object at infinity)

[0066] Conditional expression (2-3) specifies the ratio of the focal length of the second fixed group GB to the focal length of the imaging optical system GI in the wide-angle end state. By satisfying the conditional expression (2-3), good optical performance can be obtained. If it is lower than the lower limit value of the conditional expression (2-3), the optical focal length of the second fixed group GB becomes stronger, and the correction of astigmatism becomes difficult, so it is not preferred. In addition, in order to make the effect of the conditional expression (2-3) reliable, it is more preferred to set the lower limit value of the conditional expression (2-3) to 0.90, 1.00, 1.10, and further to 1.15. In addition, if it exceeds the upper limit value of the conditional expression (2-3), the optical focal length of the imaging optical system GI becomes stronger, and the correction of spherical aberration and field curvature becomes difficult, so it is not preferred. In addition, in order to make the effect of the conditional expression (2-3) reliable, it is more preferred to set the upper limit value of the conditional expression (2-3) to 3.80, 3.50, 3.20, and further to 3.00.

[0067] In the optical system OL2 according to the second embodiment, it is preferable that the second fixed group GB has negative refractive power. According to this configuration, it is possible to correct the field curvature and astigmatism of the optical system OL2 well.

[0068] In the optical system OL2 according to the second embodiment, it is preferable that the imaging optical system GI has a diaphragm (aperture stop S). According to this configuration, the diameter of the optical system OL2 can be reduced, and field curvature and distortion can be corrected well.

[0069] In addition, it is preferable that the optical system OL2 according to the second embodiment, when focusing, a part of the lens groups of the imaging optical system GI (for example, Figure 1 In the case of the optical system OL2, the first to third movable groups (G1 to G3) are moved along the optical axis as the focusing group. According to this configuration, the change of the field curvature during focusing of the optical system OL2 can be reduced.

[0070] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-4).

[0071] 0.05<TLo / TL<0.30 (2-4) in, TLo: The distance on the optical axis from the lens surface closest to the object side of the objective optical system GO to the first intermediate image IM1 in the wide-angle end state TL: The total optical length of the optical system OL2 at the wide-angle end

[0072] Conditional formula (2-4) specifies the ratio of the distance on the optical axis from the lens surface closest to the object side of the objective optical system GO to the first intermediate image IM1 under the wide-angle end state (the optical total length of the objective optical system GO) to the optical total length of the optical system OL2. By satisfying this conditional formula (2-4), good optical performance can be obtained. If it is lower than the lower limit of the conditional formula (2-4), the focal length of the objective optical system GO becomes stronger, and the performance degradation caused by the manufacturing error becomes larger, so it is not preferred. In addition, in order to make the effect of this conditional formula (2-4) reliable, it is more preferred to set the lower limit of the conditional formula (2-4) to 0.06, 0.08, and further to 0.10. In addition, if it exceeds the upper limit of the conditional formula (2-4), the focal length of the objective optical system GO becomes weaker, and the small diameter of the optical system OL2 becomes difficult, so it is not preferred. Or, the focal length of the relay optical system GR and the imaging optical system GI becomes stronger, and the correction of spherical aberration and field curvature becomes difficult, so it is not preferred. In order to ensure the effect of the conditional expression (2-4), it is more preferable to set the upper limit value of the conditional expression (2-4) to 0.28, 0.25, 0.22, and further to 0.20.

[0073] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-5).

[0074] 0.20<TLr1 / TL<0.50 (2-5) in, TLr1: The distance on the optical axis from the first intermediate image IM1 to the second intermediate image IM2 in the wide-angle end state TL: The total optical length of the optical system OL2 at the wide-angle end

[0075] Conditional formula (2-5) specifies the ratio of the distance on the optical axis from the first intermediate image IM1 to the second intermediate image IM2 in the wide-angle end state to the total optical length of the optical system OL2. By satisfying this conditional formula (2-5), good optical performance can be obtained. If it is lower than the lower limit of the conditional formula (2-5), the focal length of the relay optical system GR becomes stronger, and the correction of spherical aberration and image curvature becomes difficult, so it is not preferred. In addition, in order to make the effect of the conditional formula (2-5) reliable, it is more preferred to set the lower limit of the conditional formula (2-5) to 0.21, 0.23, and further to 0.25. In addition, if it exceeds the upper limit of the conditional formula (2-5), the focal length of the relay optical system GR becomes weaker, and the reduction of the diameter of the optical system OL2 becomes difficult, so it is not preferred. Alternatively, the focal length of the objective optical system GO and the imaging optical system GI becomes stronger, and the correction of spherical aberration and image curvature becomes difficult, so it is not preferred. In order to ensure the effect of the conditional expression (2-5), it is more preferable to set the upper limit value of the conditional expression (2-5) to 0.48, 0.45, 0.42, and further to 0.40.

[0076] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-6).

[0077] 0.30<TLr2 / TL<0.80 (2-6) in, TLr2: The distance on the optical axis from the second intermediate image IM2 to the image plane I in the wide-angle end state TL: The total optical length of the optical system OL2 at the wide-angle end

[0078] Conditional formula (2-6) specifies the ratio of the distance on the optical axis from the second intermediate image IM2 to the image plane I in the wide-angle end state to the total optical length of the optical system OL2. By satisfying this conditional formula (2-6), good optical performance can be obtained. If it is lower than the lower limit of the conditional formula (2-6), the focal length of the imaging optical system GI becomes stronger, and it becomes difficult to correct spherical aberration and image curvature, so it is not preferred. In addition, in order to make the effect of this conditional formula (2-6) reliable, it is more preferred to set the lower limit of the conditional formula (2-6) to 0.32, 0.35, 0.38, and further to 0.40. In addition, if it exceeds the upper limit of the conditional formula (2-6), the focal length of the imaging optical system GI becomes weaker, and the optical system OL2 is enlarged, so it is not preferred. Alternatively, the focal length of the objective optical system GO and the relay optical system GR becomes stronger, and the performance degradation caused by the manufacturing error becomes larger, so it is not preferred. In order to ensure the effect of the conditional expression (2-6), it is more preferable to set the upper limit value of the conditional expression (2-6) to 0.78, 0.75, 0.72, and further to 0.70.

[0079] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-7).

[0080] 0.20<Lsum / TLr2<0.60 (2-7) in, Lsum: Total thickness of the lens of the imaging optical system GI TLr2: The distance on the optical axis from the second intermediate image IM2 to the image plane I in the wide-angle end state

[0081] Conditional formula (2-7) specifies the ratio of the total thickness of the lenses of the imaging optical system GI (the value obtained by adding up the thicknesses of all the lenses constituting the imaging optical system GI) to the distance on the optical axis from the second intermediate image IM2 to the image plane I in the wide-angle end state. By satisfying this conditional formula (2-7), good optical performance can be obtained. If it is lower than the lower limit value of the conditional formula (2-7), the number of lenses of the imaging optical system GI becomes small, and it becomes difficult to fully correct spherical aberration and field curvature, so it is not preferred. In addition, in order to make the effect of this conditional formula (2-7) reliable, it is more preferred to set the lower limit value of the conditional formula (2-7) to 0.22, 0.25, 0.28, and further to 0.30. In addition, if the upper limit value of the conditional formula (2-7) is exceeded, the total thickness of the glass of the imaging optical system GI becomes thicker, resulting in a decrease in the amount of light. It becomes difficult to obtain a clear image, so it is not preferred. In order to ensure the effect of the conditional expression (2-7), it is more preferable to set the upper limit value of the conditional expression (2-7) to 0.58, 0.55, 0.52, and further to 0.50.

[0082] In the optical system OL2 according to the second embodiment, it is preferable that the lens L1 disposed most on the object side of the objective optical system GO is a spherical lens. According to this configuration, it is possible to reduce performance degradation due to manufacturing errors of the optical system OL2.

[0083] In the optical system OL2 according to the second embodiment, it is preferable that the lens L1 disposed most on the object side of the objective optical system GO has negative refractive power. According to this configuration, the field curvature and astigmatism of the optical system OL2 can be corrected well.

[0084] In addition, it is preferable that the optical system OL2 according to the second embodiment satisfies the following conditional expression (2-8).

[0085] 1.70<nL1 (2-8) in, nL1: The refractive index of the medium of the lens L1 arranged on the object side of the objective optical system GO for the d-line

[0086] The conditional expression (2-8) specifies the refractive index of the medium of the lens L1 disposed on the object side of the objective optical system GO for the d-line. By satisfying the conditional expression (2-8), the field curvature and astigmatism can be well corrected. In order to make the effect of the conditional expression (2-8) reliable, it is more preferable to set the lower limit of the conditional expression (2-8) to 1.72, 1.74, 1.76, 1.78, and further to 1.80.

[0087] In addition, the conditions and structures described above each exert the above-mentioned effects, and are not limited to satisfying all the conditions and structures. The above-mentioned effects can be obtained even if any one condition or structure is satisfied, or a combination of any one condition or structure is satisfied.

[0088] Next, based on Fig.13 A camera as an optical device having an optical system OL (OL1 or OL2) according to the first or second embodiment is described. The camera 1 is a so-called mirrorless camera with interchangeable lenses having an optical system OL according to the first or second embodiment as a photographic lens 2. In the camera 1, light from an object (subject) not shown is focused by the photographic lens 2, and a subject image is formed on a photographing surface of a photographing unit 3 via an OLPF (Optical low pass filter) not shown. Then, the subject image is photoelectrically converted by a photoelectric conversion element (photographing element) provided on the photographing unit 3 to generate an image of the subject. The image is displayed on an EVF (Electronic view finder) 4 provided on the camera 1. As a result, the photographer can observe the subject via the EVF 4.

[0089] Furthermore, when the photographer presses a release button (not shown), an image obtained by photoelectric conversion by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can shoot a subject using the camera 1. In addition, in the present embodiment, an example of a mirrorless camera is described, but even when the optical system OL of the present embodiment is mounted on a single-lens reflex camera having a quick return mirror on the camera body and observing the subject through a viewfinder optical system, the same effect as that of the above-mentioned camera 1 can be achieved.

[0090] In addition, the contents described below can be appropriately adopted within a range not impairing the optical performance.

[0091] In the first embodiment, an optical system OL consisting of an objective optical system GO and an imaging optical system GI of a 4-group structure is shown, but the above structural conditions and the like can also be applied to other group structures such as 5 groups and 6 groups. In addition, it can also be a structure in which a lens or a lens group is added to the side closest to the object, or a structure in which a lens or a lens group is added to the side closest to the image plane. Specifically, consider a structure in which a lens group whose position relative to the image plane is fixed when focusing is added to the side closest to the image plane of the imaging optical system GI. In addition, the so-called lens group, as long as no special boundary is specified, means a part having at least one lens separated by an air gap that changes when focusing. In addition, a lens component refers to a single lens or a joined lens in which a plurality of lenses are joined.

[0092] In addition, in the second embodiment, an optical system OL consisting of an objective optical system GO, a relay optical system GR and an imaging optical system GI of a 5-group structure is shown, but the above structural conditions and the like can also be applied to other group structures such as 6 groups and 7 groups. In addition, it can also be a structure in which a lens or a lens group is added to the side closest to the object, or a structure in which a lens or a lens group is added to the side closest to the image plane. Specifically, consider a structure in which a lens group is added to the side closest to the image plane of the imaging optical system GI that fixes the position relative to the image plane when changing the magnification or focusing. In addition, the so-called lens group, as long as no special boundary is specified, means a part having at least one lens separated by an air gap that changes when changing the magnification or focusing. In addition, a lens component refers to a single lens or a joint lens in which a plurality of lenses are joined.

[0093] In addition, a single or multiple lens groups or part of the lens groups may be moved along the optical axis to serve as a focusing group for focusing from an infinitely distant object to a close object. In this case, the focusing group may also be applied to autofocus, and is also suitable for motor drive (ultrasonic motor, etc.) for autofocus. In particular, in the first embodiment, it is preferred that the first movable group G1 and the second movable group G2 of the coupling optical system GI serve as the focusing group, and the positions of the other lenses are fixed relative to the image plane during focusing. In addition, in the second embodiment, it is preferred that the first movable group G1, the second movable group G2 and the third movable group G3 of the coupling optical system GI serve as the focusing group, and the positions of the other lenses are fixed relative to the image plane during focusing.

[0094] In addition, the lens group or part of the lens group can be moved in a manner having a displacement component in a direction orthogonal to the optical axis or rotationally moved (swung) in a plane direction including the optical axis to serve as an anti-shake group for correcting image shake caused by hand shake.

[0095] In addition, the lens surface can be formed by a spherical surface or a plane, and can also be formed by an aspherical surface. In the case where the lens surface is a spherical surface or a plane, lens processing and assembly adjustment become easy, and the degradation of optical performance caused by errors in processing and assembly adjustment can be prevented, so it is preferred. In addition, even in the case of deviation of the image plane, the degradation of the depiction performance is also small, so it is preferred. In the case where the lens surface is an aspherical surface, the aspherical surface can be an aspherical surface based on grinding, a glass molded aspherical surface in which a glass is formed into an aspherical shape with a mold, and a composite aspherical surface in which a resin is formed into an aspherical shape on the surface of the glass. In addition, the lens surface can be a diffraction surface, and the lens can also be used as a refractive index distribution lens (GRIN lens) or a plastic lens.

[0096] It is preferable to arrange the aperture stop S in the imaging optical system GI, but it is also possible not to provide a member serving as the aperture stop, but to use a lens frame instead of the aperture stop.

[0097] Furthermore, in order to reduce glare and ghosting and realize high optical performance with high contrast, an antireflection film having high transmittance in a wide wavelength range may be applied to each lens surface.

[0098] Below, refer to Fig.14 The outline of the manufacturing method of the optical system OL1 involved in the first embodiment is described. First, the objective optical system GO and the imaging optical system GI that images the intermediate image IM imaged by the objective optical system GO are prepared in sequence from the object side (step S100). Then, these lens groups are arranged in a manner that satisfies a prescribed condition (for example, the above-mentioned conditional formula (1-1)) (step S200).

[0099] In addition, refer to Fig.15The outline of the manufacturing method of the optical system OL2 involved in the second embodiment is described. First, the objective optical system GO, the relay optical system GR that images the first intermediate image IM1 imaged by the objective optical system GO, and the imaging optical system GI that images the second intermediate image IM2 imaged by the relay optical system GR are prepared in sequence from the object side (step S300). Next, the imaging optical system GI is configured in a manner such that the intervals between the adjacent lens groups change when the magnification is changed (step S400). Then, these lens groups are configured in a manner that satisfies a specified condition (for example, the above-mentioned conditional formula (2-1)) (step S500).

[0100] As described above, according to the first embodiment, it is possible to provide an optical system, an optical device, and a method for manufacturing the optical system that are capable of close-up photography, have a small lens diameter on the object side, and have excellent optical performance.

[0101] Furthermore, according to the second embodiment, it is possible to provide an optical system, an optical device, and a method for manufacturing the optical system, which have a small lens diameter on the object side, are capable of close-up photography, and have excellent optical performance.

[0102] [Example]

[0103] (First embodiment)

[0104] Hereinafter, Examples 1-1 to 1-3 according to the first embodiment will be described based on the drawings. Figure 1 , Figure 3 as well as Figure 5 The cross-sectional views are sectional views showing the structure and focal power distribution of the optical system OL1 (OL11 to OL13) involved in each embodiment. In addition, in the cross-sectional views of the optical systems OL11 to OL13, arrows are used to show the movement direction of each lens group G1 and G2 along the optical axis when focusing from an infinitely distant object (∞) to a close-distance object (close distance).

[0105] In the first embodiment and the second embodiment described later, in each of the first and second embodiments, the height in the direction perpendicular to the optical axis is set to y, the distance along the optical axis from the tangent plane of the vertex to each aspheric surface at the height y (the amount of concavity) is set to S (y), the radius of curvature of the reference spherical surface (paraxial radius of curvature) is set to r, the conic constant is set to K, and the n-order aspheric coefficient is set to An, the aspheric surface is represented by the following formula (a). In addition, in the following embodiments, "en" represents "×10-n".

[0106] S(y)=(y2 / r) / {1+(1-K×y2 / r2)1 / 2} +A4×y4+A6×y6+A8×y8+A10×y10 (a)

[0107] In the first embodiment and the second embodiment, in Example 1-2 and Example 2-2, the secondary aspheric coefficient A2 is 0. In the tables of Example 1-2 and Example 2-2, an aspheric surface is denoted by an * on the right side of the surface number.

[0108] [Example 1-1]

[0109] Figure 1 1-1 is a diagram showing the structure of an optical system OL11 involved in the first embodiment. The optical system OL11 is composed of an objective optical system GO having positive optical power and an imaging optical system GI having positive optical power in order from the object side, and the imaging optical system GI forms an intermediate image IM formed by the objective optical system GO. In addition, the imaging optical system GI is composed of a first fixed group GA having positive optical power, a first movable group G1 having negative optical power, a second movable group G2 having negative optical power, and a second fixed group GB having positive optical power in order from the object side.

[0110] The objective optical system GO is composed, from the object side, in sequence: a meniscus-shaped negative lens L11 (L1) with the convex surface toward the object side, a biconvex positive lens L12, a joined positive lens formed by joining a biconcave negative lens L13 and a biconvex positive lens L14, a joined negative lens formed by joining a biconcave negative lens L15 and a biconvex positive lens L16, a biconvex positive lens L17, a biconcave negative lens L18, and a biconvex positive lens L19.

[0111] In addition, the first fixed group GA of the imaging optical system GI is composed of, from the object side, a positive lens L21 of a meniscus shape with a convex surface facing the object side, a negative lens L22 of a biconcave shape, a positive lens L23 of a meniscus shape with a concave surface facing the object side, a positive lens L24 of a biconvex shape, and a cemented positive lens formed by cementing a negative lens L25 of a meniscus shape with a convex surface facing the object side and a positive lens L26 of a biconvex shape. In addition, the first movable group G1 is composed of, from the object side, a cemented negative lens formed by cementing a negative lens L31 of a biconcave shape and a positive lens L32 of a meniscus shape with a convex surface facing the object side. In addition, the second movable group G2 is composed of, from the object side, a negative lens L41 of a biconcave shape, and a positive lens L42 of a meniscus shape with a concave surface facing the object side. In addition, the second fixed group GB is composed of, from the object side, a cemented positive lens formed by cementing a negative lens L51 of a meniscus shape with a convex surface facing the object side and a positive lens L52 of a biconvex shape.

[0112] In the optical system OL11, an intermediate image IM is formed between the objective optical system GO and the imaging optical system GI. In addition, an aperture stop S is arranged between the first fixed group GA and the first movable group G1 of the imaging optical system GI. In addition, a filter group FL is arranged between the imaging optical system GI and the image plane I.

[0113] In addition, when the optical system OL11 focuses from an object at infinity to an object at close range, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1 and the second movable group G2 serving as focusing groups move along the optical axis direction (the first movable group G1 moves toward the image plane side, and the second movable group G2 moves toward the image plane side after temporarily moving toward the object side).

[0114] The values ​​of the parameters of the optical system OL11 are disclosed in the following Table 1. In this Table 1, f shown in the overall parameters is the focal length of the entire system, Fno is the F value, ω is the half field angle [°], Y is the maximum image height, TL is the total optical length, and Bf is the back focal length, and represents the value when the infinite object is focused. Here, the back focal length Bf represents the distance in air conversion length on the optical axis from the lens surface closest to the image side (the 39th surface) to the image surface I. In addition, the total optical length TL represents the length obtained by adding the back focal length in air conversion length to the distance on the optical axis from the lens surface closest to the object side (the 1st surface) to the lens surface closest to the image side (the 39th surface). In addition, the first column m in the lens data indicates the order of the lens surfaces from the object side along the direction of light travel (surface number), the second column r indicates the radius of curvature of each lens surface, the third column d indicates the distance on the optical axis from each optical surface to the next optical surface (surface spacing), the fourth column nd and the fifth column νd indicate the refractive index and Abbe number for the d line (λ=587.6nm). In addition, the radius of curvature ∞ indicates a plane, and the refractive index of air 1.00000 is omitted. In addition, the focal length of the lens group shows the surface number and focal length of the starting surface of each lens group.

[0115] Here, the focal length f, radius of curvature r, surface spacing d, and other lengths disclosed in all parameter values ​​below are generally expressed in "mm", but the optical system can obtain the same optical performance even if the ratio is enlarged or reduced, so it is not limited to this. In addition, the description of these symbols and the description of the parameter table are the same in the subsequent embodiments.

[0116] (Table 1) Example 1-1

[0117] [Overall parameters]

[0118] [Lens data]

[0119] [Focal length of lens group]

[0120] In addition, in the optical system OL11, the axial air gap D29 between the first fixed group GA and the first movable group G1, the axial air gap D32 between the first movable group G1 and the second movable group G2, and the axial air gap D36 between the second movable group G2 and the second fixed group GB change when focusing. In the following Table 2, the variable gaps when focusing on an object at infinity and when focusing on an object at a close distance are shown. In addition, D0 represents the distance from the lens surface (first surface) on the object side of the optical system OL11 to the object, f represents the focal length, and β represents the photographic magnification. This description is also the same in the subsequent embodiments.

[0121] (Table 2)

[0122] [Variable interval data]

[0123] exist Figure 2 The spherical aberration diagram, astigmatism diagram, distortion diagram, and coma diagram of the optical system OL11 when focusing on an infinitely distant object are shown in the figure. In each aberration diagram, FNo represents the F value, and A represents the half field angle. In addition, the value of the F value corresponding to the maximum aperture is shown in the spherical aberration diagram, the maximum value of the half field angle is shown in the astigmatism diagram and the distortion diagram, and the value of each half field angle is shown in the coma diagram. d represents the d line (λ=587.6nm), and g represents the g line (λ=435.8nm). In the astigmatism diagram, the solid line represents the sagittal image plane, and the dotted line represents the meridional image plane. In the coma diagram, the solid line represents the meridional image plane. In addition, in the aberration diagrams of each embodiment shown later, the same symbols as those of the present embodiment are also used. Through these aberration diagrams, it can be seen that the optical system OL11 corrects each aberration well and has excellent imaging performance.

[0124] [1st-2nd embodiment]

[0125] Figure 31-2 is a diagram showing the structure of the optical system OL12 involved in the first and second embodiments. The optical system OL12 is composed of an objective optical system GO having positive optical power and an imaging optical system GI having positive optical power in order from the object side, and the imaging optical system GI forms an intermediate image IM formed by the objective optical system GO. In addition, the imaging optical system GI is composed of a first fixed group GA having positive optical power, a first movable group G1 having negative optical power, a second movable group G2 having positive optical power, and a second fixed group GB having negative optical power in order from the object side.

[0126] The objective optical system GO is composed, from the object side, in sequence: a meniscus-shaped negative lens L11 (L1) with the convex surface toward the object side, a meniscus-shaped negative lens L12 with the convex surface toward the object side, a joined positive lens formed by joining a biconcave negative lens L13 and a biconvex positive lens L14, a joined positive lens formed by joining a biconcave negative lens L15 and a biconvex positive lens L16, a biconvex positive lens L17, a joined negative lens formed by joining a biconcave negative lens L18 and a biconvex positive lens L19, and a biconvex positive lens L110.

[0127] In addition, the first fixed group GA of the imaging optical system GI is composed of a biconvex positive lens L21, a biconcave negative lens L22, a biconvex positive lens L23, a biconvex positive lens L24, and a cemented positive lens formed by cementing a meniscus-shaped negative lens L25 with a convex surface facing the object side and a biconvex positive lens L26 in order from the object side. In addition, the first movable group G1 is composed of a cemented negative lens formed by cementing a biconcave negative lens L31 and a biconvex positive lens L32 in order from the object side. In addition, the second movable group G2 is composed of a meniscus-shaped positive lens L41 whose lens surface on the image side is aspherical and whose concave surface faces the object side. In addition, the second fixed group GB is composed of a biconvex positive lens L51 and a biconcave negative lens L52 in order from the object side.

[0128] In the optical system OL12, an intermediate image IM is formed between the objective optical system GO and the imaging optical system GI. In addition, an aperture stop S is arranged between the first fixed group GA and the first movable group G1 of the imaging optical system GI. In addition, a filter group FL is arranged between the imaging optical system GI and the image plane I.

[0129] In addition, when the optical system OL12 focuses from an object at infinity to an object at close range, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1 and the second movable group G2 serving as the focusing group move along the optical axis direction (the first movable group G1 moves toward the image plane side, and the second movable group G2 moves toward the object side).

[0130] The values ​​of the parameters of optical system OL12 are disclosed in Table 3 below.

[0131] (Table 3) Example 1-2

[0132] [Overall parameters]

[0133] [Lens data]

[0134] [Focal length of lens group]

[0135] In the optical system OL12, the 35th surface is formed into an aspherical shape. The following Table 4 shows the data of the aspherical surface, that is, the values ​​of the cone constant K and the aspherical constants A4 to A10.

[0136] (Table 4)

[0137] [Aspherical surface data]

[0138] In addition, in the optical system OL12, the axial air gap D30 between the first fixed group GA and the first movable group G1, the axial air gap D33 between the first movable group G1 and the second movable group G2, and the axial air gap D35 between the second movable group G2 and the second fixed group GB change when focusing. The following Table 5 shows the variable gaps when focusing on an infinitely distant object and when focusing on a close-up object.

[0139] (Table 5)

[0140] [Variable interval data]

[0141] exist Figure 4 2 shows the spherical aberration diagram, astigmatism diagram, distortion diagram, and coma diagram of the optical system OL12 when an infinitely distant object is focused. From these aberration diagrams, it can be seen that the optical system OL12 corrects various aberrations well and has excellent imaging performance.

[0142] [1st to 3rd embodiment]

[0143] Figure 51 is a diagram showing the structure of the optical system OL13 involved in the first to third embodiments. The optical system OL13 is composed of an objective optical system GO having positive optical power and an imaging optical system GI having positive optical power in order from the object side, and the imaging optical system GI forms an intermediate image IM formed by the objective optical system GO. In addition, the imaging optical system GI is composed of a first fixed group GA having positive optical power, a first movable group G1 having negative optical power, a second movable group G2 having positive optical power, and a second fixed group GB having negative optical power in order from the object side.

[0144] The objective optical system GO is composed, from the object side, in sequence: a meniscus-shaped negative lens L11 (L1) with the convex surface toward the object side, a meniscus-shaped negative lens L12 with the convex surface toward the object side, a joined positive lens formed by joining a meniscus-shaped negative lens L13 with the convex surface toward the object side and a biconvex positive lens L14, a joined positive lens formed by joining a biconcave negative lens L15 and a biconvex positive lens L16, a biconvex positive lens L17, a joined negative lens formed by joining a biconcave negative lens L18 and a biconvex positive lens L19, a meniscus-shaped negative lens L110 with the convex surface toward the object side, and a biconvex positive lens L111.

[0145] In addition, the first fixed group GA of the imaging optical system GI is composed of, from the object side, a cemented positive lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22, a meniscus positive lens L23 with a concave surface facing the object side, and a cemented positive lens formed by cementing a meniscus negative lens L24 with a convex surface facing the object side and a biconvex positive lens L25. In addition, the first movable group G1 is composed of, from the object side, a cemented negative lens formed by cementing a biconcave negative lens L31 and a biconvex positive lens L32. In addition, the second movable group G2 is composed of, from the object side, a biconvex positive lens L41, a meniscus negative lens L42 with a convex surface facing the object side, and a biconvex positive lens L43. In addition, the second fixed group GB is composed of, from the object side, a biconvex positive lens L51 and a meniscus negative lens L52 with a concave surface facing the object side.

[0146] Here, the medium of the negative lens L11 (L1) of the objective optical system GO is an optical glass manufactured by a method for making new glass called a suspension melting method. According to the suspension melting method, even an unstable composition that has been difficult to vitrify so far can be vitrified. Thus, it is possible to manufacture a glass with a high refractive index, a dispersion that is small and a high transmittance even at a short wavelength. If such a high refractive index glass is used for a negative lens of a meniscus shape, the generation of astigmatism can be reduced.

[0147] Specifically, the levitation melting method can use a laser levitation furnace to irradiate a sample with a laser such as carbon dioxide to melt the sample, and then cool and solidify the melt through a fluid of a floating gas ejected from a nozzle. The floating gas can be any gas that can float the sample. In addition to inert gases represented by air, nitrogen, oxygen, argon, etc., dry air, etc. can also be appropriately selected for use according to the application. The levitation melting method is also called a containerless solidification method. It is a method of obtaining glass by heating and melting the material without using a container such as a Pt alloy (Pt or platinum alloy, such as Pt-Au, Pt-Au-Rh, etc.) and then cooling and solidifying it (for example, refer to Japanese Patent Publication No. 2014-196236). In addition, such optical glass is not limited to the levitation melting method, and can also be made in a zero-gravity state.

[0148] In the optical system OL13, an intermediate image IM is formed between the objective optical system GO and the imaging optical system GI. In addition, an aperture stop S is arranged between the first fixed group GA and the first movable group G1 of the imaging optical system GI. In addition, a filter group FL is arranged between the imaging optical system GI and the image plane I.

[0149] In addition, when the optical system OL13 focuses from an object at infinity to an object at close range, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1 and the second movable group G2 serving as the focusing group move along the optical axis direction (the first movable group G1 moves toward the image plane side, and the second movable group G2 moves toward the object side).

[0150] The values ​​of the parameters of the optical system OL13 are disclosed in Table 6 below.

[0151] (Table 6) Embodiments 1-3

[0152] [Overall parameters]

[0153] [Lens data]

[0154] [Focal length of lens group]

[0155] In addition, in the optical system OL13, the axial air gap D29 between the first fixed group GA and the first movable group G1, the axial air gap D32 between the first movable group G1 and the second movable group G2, and the axial air gap D38 between the second movable group G2 and the second fixed group GB change when focusing. The following Table 7 shows the variable gaps when focusing on an infinitely distant object and when focusing on a close-up object.

[0156] (Table 7)

[0157] [Variable interval data]

[0158] exist Figure 6 2 shows the spherical aberration diagram, astigmatism diagram, distortion diagram, and coma diagram of the optical system OL13 when an infinitely distant object is focused. From these aberration diagrams, it can be seen that the optical system OL13 corrects various aberrations well and has excellent imaging performance.

[0159] (Second embodiment)

[0160] Hereinafter, Examples 2-1 to 2-3 according to the second embodiment will be described based on the drawings. Figure 7 , Fig. 9 as well as Fig.11 It is a cross-sectional view showing the structure and focal power distribution of the optical system OL2 (OL21 to OL23) involved in each embodiment. In addition, in the cross-sectional views of these optical systems OL21 to OL23, arrows are used to indicate the movement direction of each lens group G1 to G3 along the optical axis when changing the magnification from the wide-angle end state (W) to the telephoto end state (T) and the movement direction of each lens group G1 to G3 along the optical axis when focusing from an infinitely distant object (∞) to a close-distance object.

[0161] [Example 2-1]

[0162] Figure 7 : is a diagram showing the structure of the optical system OL21 involved in the second-first embodiment. The optical system OL21 is composed of an objective optical system GO having positive optical power, a relay optical system GR having positive optical power, and an imaging optical system GI having positive optical power in order from the object side. The relay optical system GR forms an image of the first intermediate image IM1 formed by the objective optical system GO, and the imaging optical system GI forms an image of the second intermediate image formed by the relay optical system GR. In addition, the imaging optical system GI is composed of a first fixed group GA having positive optical power, a first movable group G1 having positive optical power, a second movable group G2 having negative optical power, a third movable group G3 having positive optical power, and a second fixed group GB having negative optical power in order from the object side.

[0163] The objective optical system GO is composed, from the object side, of a meniscus-shaped negative lens L11 (L1) with its convex surface toward the object side, a meniscus-shaped positive lens L12 with its concave surface toward the object side, a joined positive lens formed by joining a biconcave negative lens L13 and a biconvex positive lens L14, a biconvex positive lens L15, and a meniscus-shaped negative lens L16 with its concave surface toward the object side.

[0164] The relay optical system GR is composed, in sequence from the object side, of a meniscus-shaped positive lens L21 with its concave surface toward the object side, a meniscus-shaped negative lens L22 with its convex surface toward the object side, a joined positive lens formed by joining a meniscus-shaped positive lens L23 with its convex surface toward the object side and a biconvex positive lens L24, a joined positive lens formed by joining a meniscus-shaped positive lens L25 with its convex surface toward the object side and a meniscus-shaped negative lens L26 with its convex surface toward the object side, a joined positive lens formed by joining a biconvex positive lens L27 and a biconcave negative lens L28, a joined positive lens formed by joining a biconcave negative lens L29 and a biconvex positive lens L210, and a joined positive lens formed by joining a biconvex positive lens L211 and a meniscus-shaped negative lens L212 with its concave surface toward the object side.

[0165] The first fixed group GA of the imaging optical system GI is composed of, in order from the object side, a cemented positive lens formed by cementing a meniscus-shaped negative lens L31 with a convex surface toward the object side and a biconvex positive lens L32, a cemented positive lens formed by cementing a biconvex positive lens L33 and a meniscus-shaped negative lens L34 with a concave surface toward the object side, and a cemented negative lens formed by cementing a biconcave negative lens L35 and a biconvex positive lens L36. In addition, the first movable group G1 is composed of, in order from the object side, a cemented positive lens formed by cementing a biconcave negative lens L41 and a biconvex positive lens L42. In addition, the second movable group G2 is composed of, in order from the object side, a cemented negative lens formed by cementing a biconvex positive lens L51 and a biconcave negative lens L52. In addition, the third movable group G3 is composed of a biconvex positive lens L61. The second fixed group GB is composed of a cemented negative lens in which a biconvex positive lens L71 and a biconcave negative lens L72 are cemented in order from the object side.

[0166] In the optical system OL21, a first intermediate image IM1 is formed between the objective optical system GO and the relay optical system GR, and a second intermediate image IM2 is formed between the relay optical system GR and the imaging optical system GI. In addition, an aperture stop S is disposed between the negative lens L34 and the negative lens L35 in the first fixed group GA of the imaging optical system GI. In addition, a filter group FL is disposed between the imaging optical system GI and the image plane I.

[0167] In addition, when the optical system OL21 changes magnification from the wide-angle end state to the telephoto end state, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1, the second movable group G2 and the third movable group G3 move along the optical axis direction (the first movable group G1 and the second movable group G2 move toward the object side, and the third movable group G3 moves toward the image plane side).

[0168] In addition, when the optical system OL21 focuses from an object at infinity to an object at close range, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1, the second movable group G2 and the third movable group G3 serving as the focusing group move along the optical axis direction (the first movable group G1, the second movable group G2 and the third movable group G3 move toward the object side).

[0169] The values ​​of the parameters of the optical system OL21 are disclosed in the following Table 8. In this Table 8, the overall parameters show f as the focal length of the entire system, Fno as the F value, ω as the half angle of view [°], Y as the maximum image height, TL as the total optical length, and Bf as the back focus, and show the values ​​when the infinitely distant object is focused in the wide-angle end state and the telephoto end state. The explanations of these symbols and the explanations of the parameter table are the same in the subsequent embodiments.

[0170] (Table 8) Example 2-1

[0171] [Overall parameters]

[0172] [Lens data]

[0173] [Focal length of lens group]

[0174] In addition, in the optical system OL21, the axial air gap D42 between the first fixed group GA and the first movable group G1, the axial air gap D45 between the first movable group G1 and the second movable group G2, the axial air gap D48 between the second movable group G2 and the third movable group G3, and the axial air gap D50 between the third movable group G3 and the second fixed group GB change when changing the magnification and focusing. In the following Table 9, the variable gaps when focusing on an infinitely distant object and focusing on a close-up object in the wide-angle end state and the telephoto end state are shown. In addition, D0 represents the distance from the lens surface (first surface) on the object side of the optical system OL21 to the object, f represents the focal length, and β represents the photographic magnification. This description is also the same in the subsequent embodiments.

[0175] (Table 9)

[0176] [Variable interval data]

[0177] exist Figure 8 The spherical aberration diagram, astigmatism diagram, distortion diagram, and coma diagram of the optical system OL21 when focusing on an infinitely distant object in the wide-angle end state and the telephoto end state are shown in FIG. Through these aberration diagrams, it can be seen that the optical system OL21 corrects various aberrations well in the entire zoom range from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0178] [Example 2-2]

[0179] Fig. 9 : is a diagram showing the structure of the optical system OL22 involved in the second embodiment. The optical system OL22 is composed of an objective optical system GO having a positive optical focal length, a relay optical system GR having a negative optical focal length, and an imaging optical system GI having a positive optical focal length. The relay optical system GR forms an image of the first intermediate image IM1 formed by the objective optical system GO, and the imaging optical system GI forms an image of the second intermediate image formed by the relay optical system GR. In addition, the imaging optical system GI is composed of a first fixed group GA having a positive optical focal length, a first movable group G1 having a positive optical focal length, a second movable group G2 having a positive optical focal length, a third movable group G3 having a negative optical focal length, and a second fixed group GB having a negative optical focal length, in order from the object side.

[0180] The objective optical system GO is composed, from the object side, in sequence: a meniscus-shaped negative lens L11 (L1) with the convex surface facing the object side, a meniscus-shaped positive lens L12 with the concave surface facing the object side, a cemented positive lens formed by cementing a biconcave negative lens L13 and a biconvex positive lens L14, a meniscus-shaped positive lens L15 with the concave surface facing the object side, a meniscus-shaped positive lens L16 with the concave surface facing the object side, a biconvex positive lens L17, a biconcave negative lens L18, and a biconvex positive lens L19.

[0181] The relay optical system GR is composed, in sequence from the object side, of a cemented positive lens formed by cementing a biconvex positive lens L21 and a meniscus-shaped negative lens L22 with its concave surface facing the object side, a cemented positive lens formed by cementing a biconvex positive lens L23 and a meniscus-shaped negative lens L24 with its concave surface facing the object side, a meniscus-shaped positive lens L25 with its convex surface facing the object side, a meniscus-shaped negative lens L26 with its convex surface facing the object side, a cemented positive lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28, and a cemented positive lens formed by cementing a biconvex positive lens L29 and a meniscus-shaped negative lens L210 with its concave surface facing the object side.

[0182] The first fixed group GA of the imaging optical system GI is composed of, from the object side, a cemented positive lens formed by cementing a biconvex positive lens L31 and a meniscus-shaped negative lens L32 with a concave surface facing the object side, a cemented positive lens formed by cementing a biconvex positive lens L33 and a biconcave negative lens L34, and a cemented positive lens formed by cementing a biconcave negative lens L35 and a biconvex positive lens L36. In addition, the first movable group G1 is composed of, from the object side, a cemented positive lens formed by cementing a meniscus-shaped negative lens L41 with a convex surface facing the object side and a biconvex positive lens L42. In addition, the second movable group G2 is composed of, from the object side, a cemented positive lens formed by cementing a biconvex positive lens L51 and a meniscus-shaped negative lens L52 with a concave surface facing the object side. In addition, the third movable group G3 is composed of, from the object side, a meniscus-shaped positive lens L61 with a concave surface facing the object side, and a biconcave negative lens L62. The second fixed group GB is composed of, in order from the object side, a biconvex positive lens L71 and a biconcave negative lens L72 whose lens surface on the image side is aspherical.

[0183] In the optical system OL22, a first intermediate image IM1 is formed between the objective optical system GO and the relay optical system GR, and a second intermediate image IM2 is formed between the relay optical system GR and the imaging optical system GI. In addition, an aperture stop S is disposed between the negative lens L34 and the negative lens L35 in the first fixed group GA of the imaging optical system GI. In addition, a filter group FL is disposed between the imaging optical system GI and the image plane I.

[0184] In addition, when the optical system OL22 changes magnification from the wide-angle end state to the telephoto end state, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1, the second movable group G2 and the third movable group G3 move along the optical axis direction (the first movable group G1 moves toward the object side, and the second movable group G2 and the third movable group G3 move toward the image plane side).

[0185] In addition, when the optical system OL22 focuses from an object at infinity to an object at close range, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1, the second movable group G2 and the third movable group G3 serving as the focusing group move along the optical axis direction (the first movable group G1, the second movable group G2 and the third movable group G3 move toward the object side).

[0186] The values ​​of the parameters of the optical system OL22 are disclosed in Table 10 below.

[0187] (Table 10) Example 2-2

[0188] [Overall parameters]

[0189] [Lens data]

[0190] [Focal length of lens group]

[0191] In the optical system OL22, the 59th surface is formed into an aspherical shape. The following Table 11 shows the data of the aspherical surface, that is, the values ​​of the cone constant K and the aspherical constants A4 to A10.

[0192] (Table 11)

[0193] [Aspherical surface data]

[0194] In addition, in the optical system OL22, the axial air gap D45 between the first fixed group GA and the first movable group G1, the axial air gap D48 between the first movable group G1 and the second movable group G2, the axial air gap D51 between the second movable group G2 and the third movable group G3, and the axial air gap D55 between the third movable group G3 and the second fixed group GB change when zooming and focusing. The following Table 12 shows the variable gaps when focusing on an infinitely distant object and focusing on a close-up object in the wide-angle end state and the telephoto end state.

[0195] (Table 12)

[0196] [Variable interval data]

[0197] exist Fig.10 The spherical aberration diagram, astigmatism diagram, distortion diagram, and coma diagram of the optical system OL22 when focusing on an infinitely distant object in the wide-angle end state and the telephoto end state are shown in FIG. Through these aberration diagrams, it can be seen that the optical system OL22 corrects various aberrations well in the entire zoom range from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0198] [Example 2-3]

[0199] Fig.11 : is a diagram showing the structure of the optical system OL23 involved in the second and third embodiments. The optical system OL23 is composed of an objective optical system GO having positive optical power, a relay optical system GR having positive optical power, and an imaging optical system GI having positive optical power. The relay optical system GR forms an image of the first intermediate image IM1 formed by the objective optical system GO, and the imaging optical system GI forms an image of the second intermediate image formed by the relay optical system GR. In addition, the imaging optical system GI is composed of a first fixed group GA having positive optical power, a first movable group G1 having positive optical power, a second movable group G2 having positive optical power, a third movable group G3 having positive optical power, and a second fixed group GB having negative optical power in order from the object side.

[0200] The objective optical system GO is composed, from the object side, in sequence: a meniscus-shaped negative lens L11 (L1) with the convex surface facing the object side, a meniscus-shaped negative lens L12 with the convex surface facing the object side, a meniscus-shaped positive lens L13 with the concave surface facing the object side, a joined positive lens formed by joining a meniscus-shaped negative lens L14 with the concave surface facing the object side and a meniscus-shaped positive lens L15 with the concave surface facing the object side, a joined positive lens formed by joining a biconvex positive lens L16 and a meniscus-shaped negative lens L17 with the concave surface facing the object side, a biconvex positive lens L18, a meniscus-shaped negative lens L19 with the concave surface facing the object side, and a meniscus-shaped positive lens L110 with the convex surface facing the object side.

[0201] The relay optical system GR is composed, in sequence from the object side, of a joined positive lens formed by joining a meniscus-shaped positive lens L21 with its concave surface facing the object side and a meniscus-shaped negative lens L22 with its concave surface facing the object side, a joined positive lens formed by joining a meniscus-shaped negative lens L23 with its convex surface facing the object side and a meniscus-shaped positive lens L24 with its convex surface facing the object side, a meniscus-shaped negative lens L25 with its convex surface facing the object side, a joined positive lens formed by joining a biconcave negative lens L26 and a biconvex positive lens L27, and a joined positive lens formed by joining a biconvex positive lens L28 and a meniscus-shaped negative lens L29 with its concave surface facing the object side.

[0202] The first fixed group GA of the imaging optical system GI is composed of, in order from the object side, a cemented positive lens formed by cementing a negative lens L31 with a convex surface toward the object side and a positive lens L32 with a convex surface toward the object side, a cemented positive lens formed by cementing a negative lens L33 with a convex surface toward the object side and a positive lens L34 with a convex surface toward the object side, and a cemented positive lens formed by cementing a biconcave negative lens L35 and a biconvex positive lens L36. In addition, the first movable group G1 is composed of, in order from the object side, a cemented positive lens formed by cementing a positive lens L41 with a biconvex shape and a negative lens L42 with a concave surface toward the object side. In addition, the second movable group G2 is composed of, in order from the object side, a cemented positive lens formed by cementing a positive lens L51 with a biconvex shape and a negative lens L52 with a biconcave shape. In addition, the third movable group G3 is composed of a cemented positive lens formed by cementing a biconcave negative lens L61 and a biconvex positive lens L62 in order from the object side. In addition, the second fixed group GB is composed of a biconcave negative lens L71, a biconvex positive lens L72, a meniscus-shaped negative lens L73 with the convex surface facing the object side, a biconvex positive lens L74, and a meniscus-shaped negative lens L75 with the concave surface facing the object side in order from the object side.

[0203] Here, the medium of the negative lens L11 (L1) of the objective optical system GO is an optical glass manufactured by a method for making new glass called a suspension melting method. According to the suspension melting method, even an unstable composition that has been difficult to vitrify so far can be vitrified. Thus, it is possible to manufacture a glass with a high refractive index, a dispersion that is small and a high transmittance even at a short wavelength. If such a high refractive index glass is used for a negative lens of a meniscus shape, the generation of astigmatism can be reduced.

[0204] Specifically, the levitation melting method can use a laser levitation furnace to irradiate a sample with a laser such as carbon dioxide to melt the sample, and then cool and solidify the melt through a fluid of a floating gas ejected from a nozzle. The floating gas can be any gas that can float the sample. In addition to inert gases represented by air, nitrogen, oxygen, argon, etc., dry air, etc. can also be appropriately selected for use according to the application. The levitation melting method is also called a containerless solidification method. It is a method of obtaining glass by heating and melting the material without using a container such as a Pt alloy (Pt or platinum alloy, such as Pt-Au, Pt-Au-Rh, etc.) and then cooling and solidifying it (for example, refer to Japanese Patent Publication No. 2014-196236). In addition, such optical glass is not limited to the levitation melting method, and can also be made in a zero-gravity state.

[0205] In the optical system OL23, a first intermediate image IM1 is formed between the objective optical system GO and the relay optical system GR, and a second intermediate image IM2 is formed between the relay optical system GR and the imaging optical system GI. In addition, an aperture stop S is arranged between the positive lens L34 and the negative lens L35 in the first fixed group GA of the imaging optical system GI. In addition, a filter group FL is arranged between the imaging optical system GI and the image plane I.

[0206] In addition, when the optical system OL23 changes magnification from the wide-angle end state to the telephoto end state, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1, the second movable group G2 and the third movable group G3 move along the optical axis direction (the first movable group G1, the second movable group G2 and the third movable group G3 move toward the object side).

[0207] In addition, when the optical system OL23 focuses from an infinitely distant object to a close object, the first fixed group GA and the second fixed group GB of the imaging optical system GI are fixed relative to the image plane I, and the first movable group G1, the second movable group G2, and the third movable group G3 as the focusing group move in the optical axis direction. Specifically, in the wide-angle end state, the first movable group G1, the second movable group G2, and the third movable group G3 move toward the object side. In addition, in the telephoto end state, the first movable group G1 moves toward the object side and then moves toward the image plane side, and the second movable group G2 and the third movable group G3 move toward the object side.

[0208] The values ​​of the parameters of the optical system OL23 are disclosed in Table 13 below.

[0209] (Table 13) Example 2-3

[0210] [Overall parameters]

[0211] [Lens data]

[0212] [Focal length of lens group]

[0213] In the optical system OL23, the axial air gap D44 between the first fixed group GA and the first movable group G1, the axial air gap D47 between the first movable group G1 and the second movable group G2, the axial air gap D50 between the second movable group G2 and the third movable group G3, and the axial air gap D53 between the third movable group G3 and the second fixed group GB change when zooming and focusing. The following Table 14 shows the variable gaps when focusing on an infinitely distant object and a close-distance object in the wide-angle end state and the telephoto end state.

[0214] (Table 14)

[0215] [Variable interval data]

[0216] exist Fig.12 The spherical aberration diagram, astigmatism diagram, distortion diagram, and coma diagram of the optical system OL23 when focusing on an infinitely distant object in the wide-angle end state and the telephoto end state are shown in FIG. Through these aberration diagrams, it can be seen that the optical system OL23 corrects various aberrations well in the entire zoom range from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0217] [Conditional value]

[0218] Table 15 below shows the corresponding values ​​of conditional expressions (1-1) to (1-7) in Examples 1-1 to 1-3 of the first embodiment.

[0219] (Table 15)

[0220] Table 16 below shows the corresponding values ​​of conditional expressions (2-1) to (2-8) in Example 2-1 to Example 2-3 of the second embodiment.

[0221] (Table 16)

[0222] Description of symbols 1 Camera (optical equipment) OL1 (OL11~OL13) Optical system OL2(OL21~OL23) Optical System GO objective optical system GI imaging optical system GR relay optical system GA 1st fixed group G1 1st movable group (focus group) G2 2nd movable group (focusing group) G3 3rd movable group (focusing group) GB 2nd fixed group S Aperture diaphragm

Claims

1. An optical system, wherein: The optical system is composed of an objective optical system and an imaging optical system in order from the object side. The imaging optical system forms an intermediate image formed by the objective optical system. The optical system satisfies the following conditions: 0.40<fo / f<0.80 in, fo: focal length of the objective optical system, f: The focal length of the entire optical system.

2. The optical system according to claim 1, wherein: The intermediate image is one.

3. The optical system according to claim 1 or 2, wherein: The imaging optical system has at least two focusing groups. When focusing is performed, the intervals between adjacent lens groups change.

4. The optical system according to claim 3, wherein: When focusing, the focusing group is moved along the optical axis so that the object at infinity can be focused.

5. The optical system according to claim 3 or 4, wherein: The optical system satisfies the following conditions: 0.15<fa / fr<0.80 in, fa: the focal length of the optical system located on the object side relative to the focusing group located closest to the object in the imaging optical system, fr: focal length of the imaging optical system.

6. The optical system according to any one of claims 1 to 5, wherein: The optical system satisfies the following conditions: 0.10<TLo / TL<0.30 in, TLo: The distance on the optical axis from the lens surface closest to the object side of the objective optical system to the intermediate image, TL: total optical length of the optical system.

7. The optical system according to any one of claims 1 to 6, wherein: The optical system satisfies the following conditions: 0.30<|fb / fr|<0.80 in, fb: the focal length of the optical system located on the image plane side relative to the focusing group located closest to the image plane in the imaging optical system, fr: focal length of the imaging optical system.

8. The optical system according to any one of claims 1 to 7, wherein: The optical system satisfies the following conditions: 0.10<Lsum / TLr<0.60 in, Lsum: total lens thickness of the imaging optical system, TLr: The distance on the optical axis from the intermediate image to the image plane.

9. The optical system according to any one of claims 1 to 8, wherein: An aperture is provided in the imaging optical system.

10. The optical system according to any one of claims 1 to 9, wherein: The lens disposed closest to the object side of the objective optical system is a spherical lens.

11. The optical system according to any one of claims 1 to 10, wherein: A lens disposed closest to the object side of the objective optical system has negative refractive power.

12. The optical system according to any one of claims 1 to 11, wherein: The optical system satisfies the following conditions: 1.70<nL1 in, nL1: The refractive index of the medium of the lens arranged on the most object side of the objective optical system for d-line.

13. The optical system according to any one of claims 1 to 12, wherein: The optical system satisfies the following conditions: 0.80<ωn / ωi<1.20 in, ωn: half field of view of the optical system when focusing on close objects, ωi: half field angle of view of the optical system when an object at infinity is in focus.

14. An optical system, wherein: The optical system is composed of an objective optical system, a relay optical system and an imaging optical system in order from the object side. The relay optical system forms a first intermediate image formed by the objective optical system. The imaging optical system forms an image of a second intermediate image formed by the relay optical system. When changing the magnification, the intervals between adjacent lens groups of the imaging optical system change. The optical system satisfies the following conditions: 1.50<|fmin| / fr2<8.00 in, fmin: The focal length of the lens group with the smallest absolute focal length among the lens groups that move when changing magnification. fr2: focal length of the imaging optical system in the wide-angle end state.

15. The optical system according to claim 14, wherein: The imaging optical system is composed of a first fixed group, a plurality of movable groups and a second fixed group in order from the object side. The first fixed group is fixed relative to the image plane when zooming. The plurality of movable groups move along the optical axis when zooming. The second fixed group is fixed relative to the image plane when zooming. The optical system satisfies the following conditions: 1.00<fa / fr2<5.00 in, fa: focal length of the first fixed group, fr2: focal length of the imaging optical system in the wide-angle end state.

16. The optical system according to claim 15, wherein: The optical system satisfies the following conditions: 0.80<|fb| / fr2<4.00 in, fb: focal length of the second fixed group, fr2: focal length of the imaging optical system in the wide-angle end state.

17. An optical system according to claim 15 or 16, wherein: The second fixed group has negative optical power.

18. The optical system according to any one of claims 14 to 17, wherein: The imaging optical system has an aperture.

19. The optical system according to any one of claims 14 to 18, wherein: When focusing is performed, a part of the lens group of the imaging optical system moves along the optical axis as a focusing group.

20. The optical system of claim 19, wherein: When focusing, the focusing group is moved along the optical axis to focus on an object at infinity.

21. The optical system according to any one of claims 14 to 20, wherein: The optical system satisfies the following conditions: 0.05<TLo / TL<0.30 in, TLo: the distance on the optical axis from the lens surface closest to the object side of the objective optical system to the first intermediate image in the wide-angle end state, TL: The total optical length of the optical system in the wide-angle end state.

22. The optical system according to any one of claims 14 to 21, wherein: The optical system satisfies the following conditions: 0.20<TLr1 / TL<0.50 in, TLr1: the distance on the optical axis from the first intermediate image to the second intermediate image in the wide-angle end state, TL: The total optical length of the optical system in the wide-angle end state.

23. The optical system according to any one of claims 14 to 22, wherein: The optical system satisfies the following conditions: 0.30<TLr2 / TL<0.80 in, TLr2: the distance on the optical axis from the second intermediate image to the image plane in the wide-angle end state, TL: The total optical length of the optical system in the wide-angle end state.

24. The optical system according to any one of claims 14 to 23, wherein: The optical system satisfies the following conditions: 0.20<Lsum / TLr2<0.60 in, Lsum: total lens thickness of the imaging optical system, TLr2: The distance on the optical axis from the second intermediate image to the image plane in the wide-angle end state.

25. The optical system according to any one of claims 14 to 24, wherein: The lens disposed closest to the object side of the objective optical system is a spherical lens.

26. The optical system according to any one of claims 14 to 25, wherein: A lens disposed closest to the object side of the objective optical system has negative refractive power.

27. The optical system according to any one of claims 14 to 26, wherein: The optical system satisfies the following conditions: 1.70<nL1 in, nL1: The refractive index of the medium of the lens arranged on the most object side of the imaging optical system for the d-line.

28. An optical device comprising the optical system according to any one of claims 1 to 27.

29. A method for manufacturing an optical system, wherein the optical system is composed of an objective optical system and an imaging optical system in order from the object side, the imaging optical system forms an intermediate image formed by the objective optical system, wherein: Configure in a way that satisfies the following conditions: 0.40<fo / f<0.80 in, fo: focal length of the objective optical system, f: The focal length of the entire optical system.

30. A method for manufacturing an optical system, wherein the optical system is composed of an objective optical system, a relay optical system, and an imaging optical system in order from the object side, the relay optical system forms an image of a first intermediate image formed by the objective optical system, and the imaging optical system forms an image of a second intermediate image formed by the relay optical system, wherein: The imaging optical system is configured so that the intervals between adjacent lens groups change when the magnification is changed. Configure in a way that satisfies the following conditions: 1.50<|fmin| / fr2<8.00 in, fmin: The focal length of the lens group with the smallest absolute focal length among the lens groups that move when changing magnification. fr2: focal length of the imaging optical system in the wide-angle end state.

Images