Optical system and imaging apparatus having the same

Abstract

To provide an optical system that, in a macro lens, reduces the weight and size of focus lens groups, achieves an improvement in focus stop accuracy and acceleration of focus speed, and is compact and has high performance.SOLUTION: An optical system L0 has a first lens group L1, a second lens group L2, a third lens group L3, and a fourth lens group L4, which are arranged in order from an object side. An aperture stop is arranged on an image side of the second lens group, and the first lens group and a final lens group are fixed in focusing. Focus lens groups are arranged on an object side and an image side, respectively, of the aperture stop. A most-image side focus lens group arranged on the most image side, of the focus lens groups, moves to the image side in focusing. The optical system can make a photographic magnification in the shortest photographing distance 0.5 times or more in absolute value. The final lens group includes a positive lens and a negative lens. The total thickness dF of the focus lens groups and the entire lens length L of the optical system satisfy a predetermined condition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical system suitable for digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, surveillance cameras, and the like. [Background technology]

[0002] Macro lenses are known as lenses capable of close-up photography. In recent years, there has been a demand for macro lenses that have high optical performance and little aberration variation over the entire focus range.

[0003] Patent Documents 1 and 2 disclose a macro lens that corrects aberration fluctuations during focusing by moving a large focus lens group during focusing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-57662 A [Patent Document 2] JP 2019-164277 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the macro lenses described in Patent Documents 1 and 2 have the problem that the actuator required to move the large focus lens group becomes large, and the large focus lens group also leads to a decrease in focus stopping accuracy and focus speed.

[0006] The present invention provides a compact, high-performance optical system in which the focus lens group is made lighter and smaller in weight, and high focus stop accuracy and high focus speed are achieved in a macro lens. [Means for solving the problem]

[0007] An optical system according to one aspect of the present invention has a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in that order from an object side to an image side, and a distance between adjacent lens groups changes during focusing from infinity to a close distance, an aperture stop is arranged on the image side of the second lens group, the first lens group and a final lens group arranged closest to the image side in the optical system are fixed with respect to an image plane during focusing, focus lens groups that move during focusing are arranged on the object side and image side of the aperture stop, and the most image-side focus lens group arranged closest to the image side among the focus lens groups moves to the image side during focusing, the optical system is capable of achieving an absolute shooting magnification of 0.5 times or more at a minimum shooting distance, and the final lens group includes a positive lens and a negative lens, 0.025 <dF / L<0.099 The present invention is characterized in that the following conditional expression is satisfied:

[0008] Other objects and features of the present invention will be described in the following embodiments. Effect of the Invention

[0009] According to the present invention, in a macro lens, it is possible to provide a small, high-performance optical system by making the focus lens group lightweight and compact, improving the focus stop accuracy and increasing the focus speed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view of the optical system of the first embodiment. [Diagram 2] 1A is a longitudinal aberration diagram of the optical system of Example 1 when focused at infinity, and FIG. 1B is a longitudinal aberration diagram at an imaging magnification of −1.0 times. [Diagram 3] FIG. 11 is a cross-sectional view of an optical system according to a second embodiment. [Figure 4]1A is a longitudinal aberration diagram of the optical system of Example 2 when focused on infinity, and FIG. 1B is a longitudinal aberration diagram at an imaging magnification of −1.0 times. [Diagram 5] FIG. 11 is a cross-sectional view of an optical system according to a third embodiment. [Figure 6] 11A is a longitudinal aberration diagram of the optical system of Example 3 when focused at infinity, and FIG. 11B is a longitudinal aberration diagram at an imaging magnification of −0.5 times. [Figure 7] FIG. 11 is a cross-sectional view of an optical system according to a fourth embodiment. [Figure 8] 11A is a longitudinal aberration diagram of the optical system of Example 4 when focused at infinity, and FIG. 11B is a longitudinal aberration diagram at a magnification of −0.5 times. [Figure 9] FIG. 11 is a cross-sectional view of an optical system according to a fifth embodiment. [Figure 10] 13A is a longitudinal aberration diagram of the optical system of Example 5 when focused on infinity, and FIG. 13B is a longitudinal aberration diagram at a shooting magnification of −1.0 times. [Figure 11] FIG. 13 is a cross-sectional view of the optical system of Example 6. [Figure 12] 13A is a longitudinal aberration diagram of the optical system of Example 6 when focused on infinity, and FIG. 13B is a longitudinal aberration diagram at an imaging magnification of −1.0 times. [Figure 13] FIG. 13 is a cross-sectional view of the optical system of Example 7. [Figure 14] 13A is a longitudinal aberration diagram of the optical system of Example 7 when focused on infinity, and FIG. 13B is a longitudinal aberration diagram at an imaging magnification of −1.0 times. [Figure 15] FIG. 13 is a cross-sectional view of the optical system of Example 8. [Figure 16] 13A is a longitudinal aberration diagram of the optical system of Example 8 when focused at infinity, and FIG. 13B is a longitudinal aberration diagram of the optical system of Example 8 when focused at infinity, and FIG. [Figure 17] FIG. 1 is a schematic diagram of an imaging device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an optical system and an image pickup apparatus having the same according to the present invention will be described with reference to the accompanying drawings.

[0012] The optical system in each embodiment is an optical system used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, and surveillance cameras.

[0013] Fig. 1 is a lens cross-sectional view of the optical system L0 of Example 1 when focused at infinity. Fig. 2(A) is a longitudinal aberration diagram of the optical system L0 of Example 1 when focused at infinity. Fig. 2(B) is a longitudinal aberration diagram of the optical system L0 of Example 1 at a shooting magnification of -1.0 times. The optical system L0 of Example 1 is an optical system with an F-number of about 4.

[0014] Fig. 3 is a lens cross-sectional view of the optical system L0 of Example 2 when focused at infinity. Fig. 4(A) is a longitudinal aberration diagram of the optical system L0 of Example 2 when focused at infinity. Fig. 4(B) is a longitudinal aberration diagram of the optical system L0 of Example 2 at a shooting magnification of -1.0 times. The optical system L0 of Example 2 is an optical system with an F-number of about 4.

[0015] Fig. 5 is a lens cross-sectional view of the optical system L0 of Example 3 when focused at infinity. Fig. 6(A) is a longitudinal aberration diagram of the optical system L0 of Example 3 when focused at infinity. Fig. 6(B) is a longitudinal aberration diagram of the optical system L0 of Example 3 at a shooting magnification of -0.5 times. The optical system L0 of Example 3 is an optical system with an F-number of about 4.

[0016] Fig. 7 is a lens cross-sectional view of the optical system L0 of Example 4 when focused at infinity. Fig. 8(A) is a longitudinal aberration diagram of the optical system L0 of Example 4 when focused at infinity. Fig. 8(B) is a longitudinal aberration diagram of the optical system L0 of Example 4 at a shooting magnification of -0.5 times. The optical system L0 of Example 4 is an optical system with an F-number of about 4.

[0017] Fig. 9 is a lens cross-sectional view of the optical system L0 of Example 5 when focused at infinity. Fig. 10(A) is a longitudinal aberration diagram of the optical system L0 of Example 5 when focused at infinity. Fig. 10(B) is a longitudinal aberration diagram of the optical system L0 of Example 5 at a shooting magnification of -1.0 times. The optical system L0 of Example 5 is an optical system with an F-number of about 4.

[0018] Fig. 11 is a lens cross-sectional view of the optical system L0 of Example 6 when focused at infinity. Fig. 12(A) is a longitudinal aberration diagram of the optical system L0 of Example 6 when focused at infinity. Fig. 12(B) is a longitudinal aberration diagram of the optical system L0 of Example 6 at a shooting magnification of -1.0 times. The optical system L0 of Example 6 is an optical system with an F-number of about 4.

[0019] Fig. 13 is a lens cross-sectional view of the optical system L0 of Example 7 when focused at infinity. Fig. 14(A) is a longitudinal aberration diagram of the optical system L0 of Example 7 when focused at infinity. Fig. 14(B) is a longitudinal aberration diagram of the optical system L0 of Example 7 at a shooting magnification of -1.0 times. The optical system L0 of Example 7 is an optical system with an F-number of about 4.

[0020] Fig. 15 is a lens cross-sectional view of the optical system L0 of Example 8 when focused at infinity. Fig. 16(A) is a longitudinal aberration diagram of the optical system L0 of Example 8 when focused at infinity. Fig. 16(B) is a longitudinal aberration diagram of the optical system L0 of Example 8 at a shooting magnification of -1.0 times. The optical system L0 of Example 8 is an optical system with an F-number of about 4.

[0021] In each lens cross-sectional view, the left side is the object side and the right side is the image side. The optical system L0 in each embodiment is configured to have multiple lens groups. In this specification, a lens group is a group of lenses that move or stand still as a whole during focusing. That is, in the optical system L0 in each embodiment, the distance between adjacent lens groups changes during focusing from infinity to a close distance. Note that the lens group may be composed of one lens or multiple lenses. The lens group may also include an aperture stop.

[0022] If i is the order of the lens groups counted from the object side (i is a natural number), Li represents the i-th lens group. The optical system L0 in each embodiment is made up of a plurality of lens groups Li.

[0023] Also, SP is an aperture stop. IP is an image plane, and when the optical system L0 of each embodiment is used as the photographing optical system of a digital still camera or digital video camera, the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is disposed thereon. When the optical system L0 of each embodiment is used as the photographing optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is disposed on the image plane IP.

[0024] Moreover, the focusing arrows shown in each lens cross-sectional view indicate the movement direction of the lens group during focusing from infinity to a close distance.

[0025] 2, 4, 6, 8, 10, 12, 14, and 16 are aberration diagrams of the optical system L0 of Examples 1 to 8. In each aberration diagram, (A) is an aberration diagram when focused on infinity, and (B) is an aberration diagram when the imaging magnification is -1.0x or -0.5x.

[0026] In the spherical aberration diagram, Fno is the F-number, and the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm) is shown. In the astigmatism diagram, dS indicates the amount of astigmatism on the sagittal image plane, and dM indicates the amount of astigmatism on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. For the shortest and intermediate focal lengths, the distortion aberration is shown as the value at the d-line when the equal solid angle projection method is used as the standard, and for the longest focal length, the distortion aberration is shown as the value at the d-line when the central projection method is used as the standard. In the chromatic aberration diagram, the amount of chromatic aberration for the g-line is shown. ω is the half angle of view (°) of the paraxial image.

[0027] Next, the characteristic configuration of the optical system L0 in each embodiment will be described.

[0028] The optical system L0 of each embodiment has a first lens group L1, a second lens group L2, a third lens group L3, and a fourth lens group L4 arranged in order from the object side to the image side, and the interval between adjacent lens groups changes during focusing from infinity to a close distance. An aperture stop SP is arranged on the image side of the second lens group L2. The first lens group L1 and the final lens group arranged on the most image side in the optical system L0 are fixed with respect to the image surface IP during focusing from infinity to a close distance. Focus lens groups that move during focusing from infinity to a close distance are arranged on the object side and image side of the aperture stop SP. The most image-side focus lens group arranged on the most image side among the focus lens groups moves to the image side during focusing from infinity to a close distance. The optical system L0 can make the shooting magnification at the shortest shooting distance at least greater than 0.5 times in absolute value. The final lens group includes a positive lens and a negative lens.

[0029] Furthermore, the optical system L0 of each embodiment satisfies the following conditional expression (1).

[0030] 0.025 <dF / L<0.099 ···(1) Here, dF is the sum of the distances on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in each focus lens group, and L is the total lens length of the optical system L0.

[0031] Conditional formula (1) defines the total thickness dF1 of all focus lens groups in terms of the total lens length L of the optical system L0. If the lower limit of conditional formula (1) is not met, the total lens length L becomes too large. If the upper limit of conditional formula (1) is exceeded and the total thickness dF becomes large, the focus lens groups become large, resulting in a decrease in focus speed and an increase in the size of the optical system L0.

[0032] Furthermore, it is preferable that the numerical range of conditional expression (1) is within the range of the following conditional expression (1a).

[0033] 0.026 <dF / L<0.098 ···(1a) It is further preferable that the numerical range of conditional expression (1) satisfies the range of the following conditional expression (1b).

[0034] 0.027 <dF / L<0.097 ···(1b) Next, a description will be given of configurations that are preferably satisfied in the optical system L0 of each embodiment.

[0035] Each focus lens group preferably consists of four or fewer lenses, which makes each focus lens group lightweight and enables quick focusing.

[0036] It is preferable that the final lens group be made up of a positive subgroup and a negative subgroup, arranged in that order from the object side to the image side, so that the final lens group has a telephoto arrangement, which makes it possible to prevent the overall lens length of the optical system L0 from becoming large.

[0037] It is preferable that the first lens group L1 has a positive refractive power, which makes the entire optical system L0 closer to a telephoto arrangement and prevents the overall lens length of the optical system L0 from increasing.

[0038] It is preferable that one focus lens group is disposed on each of the object side and image side of the aperture diaphragm SP. In other words, it is preferable that the number of focus lens groups disposed on the object side of the aperture diaphragm SP is one, and the number of focus lenses disposed on the image side of the aperture diaphragm SP is one. This leads to simplification of the focus drive section, and makes it possible to prevent the optical system L0 from becoming large.

[0039] Of the focus lens groups arranged on the image side of the aperture stop SP, the focus lens group arranged closest to the object side preferably has negative refractive power. This makes it possible to prevent the focus lens group from becoming large. In addition, by arranging a lens group with negative refractive power near the aperture stop SP, it becomes easier to correct the curvature of field.

[0040] It is preferable that the first lens group L1 includes a subgroup L1a that moves in a direction including a component perpendicular to the optical axis during image blur correction, thereby suppressing the effects of camera shake during shooting and enabling high-resolution imaging.

[0041] Next, conditions that the optical system L0 of each embodiment should preferably satisfy will be described. The optical system L0 of each embodiment should preferably satisfy one or more of the following conditional expressions (2) to (9).

[0042] 0.0<|f1 / fL|<1.0 (2) 0.1<|(1-βf 2 )×βr 2 |<5.1 ···(3) 0.8 <L / f<2.4 ···(4) 0.2 <f1 / f<1.3 ···(5) 0.1<|f2 / f|<2.5 (6) 0.2<|f3 / f|<0.8 (7) 0.1<|f4 / f|<0.9 (8) |β|≧0.5 (9) Here, f1 is the focal length of the first lens group L1. fL is the focal length of the final lens group. βf is the lateral magnification of the most image-side focus lens group. βr is the combined lateral magnification of all lens groups arranged on the image side of the most image-side focus lens group. f is the focal length of optical system L0. f2 is the focal length of the second lens group. f3 is the focal length of the third lens group. f4 is the focal length of the fourth lens group. β is the shooting magnification at the minimum shooting distance of optical system L0.

[0043] Conditional formula (2) defines the focal length f1 of the first lens group L1 in terms of the focal length fL of the final lens group. If the focal length f1 of the first lens group L1 becomes small below the lower limit of conditional formula (2), the refractive power of the first lens group becomes too strong, and light rays converged or diverged by the first lens group generate large spherical aberration and coma aberration. This makes it difficult to correct aberrations with the subsequent lens groups, which is undesirable. If the focal length f1 of the first lens group becomes large above the upper limit of conditional formula (2), it is advantageous for aberration correction, but the lens group has no refractive power, so the total lens length increases, which is undesirable from the perspective of size and weight reduction.

[0044] Condition (3) specifies the focus sensitivity of the most image-side focus lens group. If the lower limit of condition (3) is not satisfied, the movement amount of the most image-side focus lens group increases, and the total lens length of the optical system L0 increases, which is not preferable. If the upper limit of condition (3) is exceeded, the focus stop accuracy of the most image-side focus lens group during focusing decreases, which makes it difficult to achieve proper focusing, which is not preferable.

[0045] Conditional expression (4) defines the total lens length L of the optical system L0 in terms of the focal length f of the optical system L0. If the focal length f is greater than the lower limit of conditional expression (4), the total lens length L of the optical system L0 becomes large, which is undesirable. If the focal length f is greater than the upper limit of conditional expression (4), the focal length f becomes small, which is undesirable because it becomes difficult to correct various aberrations.

[0046] Conditional expression (5) defines the focal length f1 of the first lens group L1 in terms of the focal length f of the optical system L0. If the focal length f1 is reduced below the lower limit of conditional expression (5), it is undesirable because it becomes difficult to correct various aberrations. If the focal length f1 is increased above the upper limit of conditional expression (5), it is undesirable because the total lens length of the optical system L0 becomes large.

[0047] Conditional expression (6) defines the focal length f2 of the second lens group L2 in terms of the focal length f of the optical system L0. Conditional expression (6) serves to reduce the occurrence of spherical aberration, and if the value of |f2 / f| falls within the range of conditional expression (6), it is easy to correct spherical aberration.

[0048] Conditional expression (7) defines the focal length f3 of the third lens group L3 in terms of the focal length f of the optical system L0. Conditional expression (7) serves to reduce the occurrence of spherical aberration, and if the value of |f3 / f| falls within the range of conditional expression (7), it is easy to correct spherical aberration.

[0049] Conditional expression (8) defines the focal length f4 of the fourth lens group L4 in terms of the focal length f of the optical system L0. Conditional expression (8) serves to reduce the occurrence of field curvature, and if the value of |f4 / f| falls within the range of conditional expression (8), it is easy to correct the field curvature.

[0050] Condition (9) defines the condition for the shooting magnification β at the shortest shooting distance of the optical system L0. If the lower limit of condition (9) is exceeded, it becomes difficult to shoot at a high magnification, which is not preferable.

[0051] It is more preferable that the numerical ranges of the conditional expressions (2) to (9) be within the ranges of the following conditional expressions (2a) to (9a).

[0052] 0.0<|f1 / fL|<0.95 (2a) 0.2<|(1-βf 2 )×βr 2 |<5.0 ···(3a) 1.0 <L / f<2.3 ···(4a) 0.3 <f1 / f<1.2 ···(5a) 0.2<|f2 / f|<2.4 (6a) 0.3<|f3 / f|<0.7 (7a) 0.2<|f4 / f|<0.8 (8a) |β|≧0.7 (9a) It is more preferable that the numerical ranges of the conditional expressions (2) to (9) be within the ranges of the following conditional expressions (2b) to (9b).

[0053] 0.0<|f1 / fL|<0.9 (2b) 0.3<|(1-βf 2 )×βr 2 |<4.9 ···(3b) 1.05 <L / f<2.22 ···(4b) 0.4 <f1 / f<1.1 ···(5b) 0.3<|f2 / f|<2.3 (6b) 0.33<|f3 / f|<0.65 (7b) 0.3<|f4 / f|<0.7 (8b) |β|≧1.0 (9b) Next, the optical system L0 of each embodiment will be described in detail.

[0054] The optical system L0 of the first embodiment is composed of, arranged from the object side to the image side, a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having negative refractive power, and a fifth lens group L5 having positive refractive power.

[0055] In the optical system L0 of the first embodiment, the first lens group L1, the third lens group L3, and the fifth lens group L5 are fixed with respect to the image surface IP during focusing from infinity to a close distance. During focusing from infinity to a close distance, the second lens group L2 and the fourth lens group L4 move toward the image side. The third lens group L3 includes an aperture stop SP, and the aperture stop SP is disposed closest to the object side of the third lens group L3.

[0056] The optical system L0 of the second embodiment is composed of, arranged from the object side to the image side, a first lens group L1 having positive refractive power, a second lens group L2 having positive refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having negative refractive power, and a fifth lens group L5 having positive refractive power.

[0057] In the optical system L0 of the second embodiment, the first lens group L1, the third lens group L3, and the fifth lens group L5 are fixed with respect to the image surface IP during focusing from infinity to a close distance. During focusing from infinity to a close distance, the second lens group L2 moves toward the object side, and the fourth lens group L4 moves toward the image side. The third lens group L3 includes an aperture stop SP, and the aperture stop SP is disposed closest to the object side of the third lens group L3.

[0058] The optical system L0 of the third embodiment is composed of, arranged from the object side to the image side, a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having negative refractive power, and a fifth lens group L5 having positive refractive power.

[0059] During focusing from infinity to a close distance, the first lens group L1, the third lens group L3, and the fifth lens group L5 are fixed with respect to the image plane IP. During focusing from infinity to a close distance, the second lens group L2 and the fourth lens group L4 move toward the image side. The third lens group L3 includes an aperture diaphragm SP, which is located closest to the object of the third lens group L3.

[0060] The optical system L0 of the fourth embodiment is composed of, arranged from the object side to the image side, a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having negative refractive power, a fifth lens group L5 having positive refractive power, and a sixth lens group L6 having positive refractive power.

[0061] During focusing from infinity to a close distance, the first lens group L1, the third lens group L3, and the sixth lens group L6 are fixed with respect to the image plane IP. During focusing from infinity to a close distance, the second lens group L2, the fourth lens group L4, and the fifth lens group L5 move toward the image side. The third lens group L3 includes an aperture diaphragm SP, which is located closest to the object of the third lens group L3.

[0062] The optical system L0 of the fifth embodiment is composed of, arranged from the object side to the image side, a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having negative refractive power, and a fifth lens group L5 having negative refractive power.

[0063] During focusing from infinity to a close distance, the first lens group L1, the third lens group L3, and the fifth lens group L5 are fixed with respect to the image plane IP. During focusing from infinity to a close distance, the second lens group L2 and the fourth lens group L4 move toward the image side. The third lens group L3 includes an aperture diaphragm SP, which is located closest to the object of the third lens group L3.

[0064] The optical system L0 of the sixth embodiment is composed of, arranged from the object side to the image side, a first lens unit L1 having positive refractive power, a second lens unit L2 having negative refractive power, an aperture stop SP, a third lens unit L3 having negative refractive power, and a fourth lens unit L4 having positive refractive power.

[0065] During focusing from infinity to a close distance, the first lens unit L1, the aperture stop SP, and the fourth lens unit L4 are fixed with respect to the image plane IP. During focusing from infinity to a close distance, the second lens unit L2 and the third lens unit L3 move toward the image side.

[0066] The optical system L0 of the seventh embodiment is composed of, arranged from the object side to the image side, a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having negative refractive power, and a fifth lens group L5 having negative refractive power.

[0067] During focusing from infinity to a close distance, the first lens group L1, the third lens group L3, and the fifth lens group L5 are fixed with respect to the image plane IP. During focusing from infinity to a close distance, the second lens group L2 and the fourth lens group L4 move toward the image side. The third lens group L3 includes an aperture diaphragm SP, which is located closest to the object of the third lens group L3.

[0068] The optical system L0 of the eighth embodiment comprises, arranged from the object side to the image side, a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, a fourth lens group L4 having negative refractive power, and a fifth lens group L5 having positive refractive power.

[0069] During focusing from infinity to a close distance, the first lens group L1, the third lens group L3, and the fifth lens group L5 are fixed with respect to the image plane IP. During focusing from infinity to a close distance, the second lens group L2 and the fourth lens group L4 move toward the image side. The third lens group L3 includes an aperture diaphragm SP, which is located closest to the object of the third lens group L3.

[0070] As described above, according to each embodiment, in a macro lens, it is possible to reduce the weight and size of the focus lens group, improve the focus stop accuracy, and increase the focus speed, thereby providing a small, high-performance optical system.

[0071] Numerical examples 1 to 8 corresponding to the first to eighth embodiments, respectively, are shown below.

[0072] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial distance (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. In addition, nd represents the refractive index of each optical member at the d-line, and νd represents the Abbe number of the optical member. The Abbe number νd of a certain material is expressed as νd=(Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer line. The effective diameter means the diameter of the area (effective area) of the lens surface through which the effective light beam that contributes to imaging passes.

[0073] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when the optical system of each example is focused on an object at infinity. "Back focus BF" is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image surface expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the first lens surface (the lens surface closest to the object) of optical system L0 to the final lens surface plus the back focus. The term "lens group" is not limited to cases where the group is composed of multiple lenses, but also includes cases where the group is composed of a single lens.

[0074] If the optical surface is aspheric, a * symbol is added to the right of the surface number. The aspheric shape is expressed as follows, where X is the displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, and A12 are the aspheric coefficients of each order: x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 In addition, "e±XX" in each aspheric coefficient is "×10± XX " It means.

[0075] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 ∞ 1.50 37.21 2 185.879 3.29 1.95375 32.3 36.32 3 -182.103 0.13 35.88 4 58.616 5.18 1.49700 81.5 33.11 5 -191.217 0.25 31.53 6 -139.020 1.20 1.85478 24.8 31.51 7 64.476 1.84 29.58 8 60.127 1.20 1.80328 30.0 28.59 9 40.819 4.45 1.49700 81.5 27.62 10 -169.716 0.97 26.91 11 37.977 2.47 1.49700 81.5 24.00 12 117.183 (variable) 23.14 13 -224.411 0.80 1.77959 49.2 20.96 14 21.839 2.19 1.92286 20.9 20.12 15 36.163 (variable) 19.78 16 (Aperture) ∞ 0.63 18.72 17 158.702 2.48 1.95375 32.3 18.67 18 -47.239 0.12 18.56 19 -36.943 1.37 1.55787 64.9 18.65 20 -29.099 1.10 1.84666 23.8 18.47 21 -41.530 (variable) 18.42 22* -101.372 0.05 1.53110 55.9 17.54 23 -103.203 0.90 1.53887 64.2 17.53 24 41.709 (variable) 17.02 25 57.353 4.33 1.48749 70.2 21.50 26 -35.413 11.10 21.83 27 -27.840 1.00 1.69387 29.6 21.78 28 1604.966 34.03 22.88 Image plane ∞ Aspheric Data Page 22 K = 0.00000e+00 A 4=-8.05214e-07 A 6= 2.03352e-08 A 8=-2.81786e-10 A10 = 1.26453e-12 Various data Focal length 111.29 F-number: 4.12 Half angle of view (°) 11.00 Image height 21.64 Lens total length 125.00 BF 34.03 Magnification: Infinity -1.0 d12 2.82 19.92 d15 20.41 3.36 d21 1.23 17.23 d24 17.92 1.89 Entrance pupil position 67.03 104.82 Exit pupil position -25.35 -21.72 Front principal point position -30.27 -47.81 Back principal point position -77.26 -56.69 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 52.51 22.50 7.15 -9.51 2 13 -44.70 2.99 1.68 0.09 3 16 46.87 5.70 2.54 -1.00 4 22 -54.72 0.95 0.44 -0.18 5 25 296.90 16.43 -90.32 -80.24 Single lens data Lens starting surface focal length 1 1 96.87 2 4 90.90 3 6 -51.39 4 8 -162.75 5 9 66.67 6 11 111.89 7 13 -25.49 8 14 55.66 9 17 38.39 10 19 231.21 11 20 -119.67 12 22 -10862.67 13 23 -55.00 14 25 45.61 15 27 -39.43 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1∞1.50 27.70 2 38.294 3.54 2.00100 29.1 25.98 3 343.053 2.60 25.10 4 499.265 1.00 1.58913 61.1 22.03 5 31.000 3.60 20.19 6 -10384.825 1.00 1.85478 24.8 18.78 7 32.326 2.39 18.43 8 51.874 1.00 1.67300 38.1 19.09 9 31.293 3.49 1.49700 81.5 19.18 10 -69.451 0.97 19.35 11 37.877 2.38 1.49700 81.5 19.54 12 -741.291 (variable) 19.40 13 -170.842 0.75 1.56932 39.1 19.00 14 35.293 2.65 1.74983 45.3 18.78 15 -239.271 (variable) 18.61 16 (Aperture) ∞ 3.28 16.71 17 -16.832 1.40 1.95375 32.3 16.35 18 -17.300 0.15 16.86 19 218.205 4.09 1.69680 55.5 16.09 20 -16.372 0.70 1.88300 40.8 15.67 21 -36.649 (variable) 15.53 22 -52.745 1.55 1.72172 43.0 14.53 23 -20.223 0.90 1.53775 74.7 14.39 24 21.238 (variable) 13.33 25 173.567 7.05 1.57703 63.8 33.38 26 -33.331 9.01 33.91 27 -31.255 1.40 1.72916 54.7 32.62 28 -75.010 21.58 34.30 Image plane ∞ Various data Focal length 90.00 F-number: 4.12 Half angle of view (°) 13.52 Image height 21.64 Lens total length 120.00 BF 21.58 Magnification: Infinity -1.0 d12 9.07 2.17 d15 0.87 7.79 d21 1.44 23.18 d24 30.72 8.97 Entrance pupil position 40.56 41.07 41.15 39.90 40.55 Exit pupil position -63.04 -63.72 -40.86 -59.28 -53.34 Front principal point position 34.85 33.79 1.93 23.63 15.50 Back principal point position -68.41 -70.45 -60.97 -72.67 -71.17 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 93.73 23.47 11.00 -10.53 2 13 203.23 3.40 1.76 -0.23 3 16 58.10 9.61 8.59 1.96 4 22 -33.14 2.45 0.97 -0.49 5 25 105.72 17.46 -9.19 -21.13 Single lens data Lens starting surface focal length 1 1 42.81 2 4 -56.15 3 6 -37.70 4 8 -119.53 5 9 43.91 6 11 72.58 7 13 -51.31 8 14 41.19 9 17 1415.98 10 19 22.01 11 20 -34.06 12 22 44.55 13 23 -19.12 14 25 49.07 15 27 -74.49 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1∞1.50 29.20 2 137.714 2.88 1.95375 32.3 28.34 3 -156.964 0.15 27.88 4 39.757 4.70 1.49700 81.5 25.54 5 -185.324 0.17 24.54 6 -133.370 1.20 1.85478 24.8 24.52 7 54.137 1.25 23.56 8 36.053 1.20 1.54455 62.5 23.19 9 24.683 2.12 1.49700 81.5 22.46 10 37.720 0.97 22.08 11 38.076 2.45 1.49700 81.5 21.88 12 174.487 (variable) 21.48 13 743.088 1.20 1.69178 41.2 20.57 14 19.940 1.96 1.92286 20.9 19.55 15 28.454 (variable) 19.15 16 (Aperture) ∞ 4.37 18.48 17 -605.953 1.40 1.95375 32.3 18.19 18 -109.007 0.15 18.21 19 -1455.101 0.50 1.54833 43.7 18.18 20 55.907 1.77 1.72915 54.7 18.14 21 -77.622 (variable) 18.11 22* -117.521 0.21 1.53110 55.9 17.17 23 -77.304 1.50 1.48785 70.2 17.16 24 44.651 2.37 16.50 25 -346.126 2.10 1.88300 40.8 16.24 26 -47.567 1.19 16.13 27 -41.412 1.00 1.50547 66.6 15.62 28 171.592 (variable) 16.05 29 308.375 3.69 1.48749 70.2 24.10 30 -39.533 2.40 24.55 31 -49.252 1.00 1.84666 23.8 24.89 32 -136.037 43.07 25.51 Image plane ∞ Aspheric Data Page 22 K = 0.00000e+00 A 4=-4.22246e-07 A 6= 3.64925e-09 A 8=-4.07067e-11 A10 = 2.40919e-13 Various data Focal length 110.00 F-number: 4.12 Half angle of view (°) 11.13 Image height 21.64 Lens length 119.99 BF 43.07 Magnification: Infinity -0.5 d12 2.25 10.07 d15 11.47 3.66 d21 1.32 16.53 d28 16.45 1.24 Entrance pupil position 46.44 46.75 52.14 49.73 Exit pupil position -37.53 -37.38 -31.21 -35.11 Front principal point position 6.31 5.10 -21.21 -8.15 Back principal point position -66.93 -67.47 -68.07 -70.46 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 58.71 18.59 1.06 -11.99 2 13 -51.32 3.16 2.45 0.69 3 16 51.78 8.20 5.95 -0.64 4 22 -71.65 8.37 1.74 -4.61 5 29 301.70 7.10 -5.62 -10.80 Single lens data Lens starting surface focal length 1 1 77.28 2 4 66.32 3 6 -44.92 4 8 -149.29 5 9 136.34 6 11 97.42 7 13 -29.64 8 14 65.01 9 17 139.17 10 19 -98.17 11 20 44.82 12 22 424.56 13 23 -57.78 14 25 62.25 15 27 -65.90 16 29 72.13 17 31 -91.67 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1∞1.50 30.10 2 128.915 3.02 1.95375 32.3 29.21 3 -161.611 0.15 28.73 4 40.041 4.88 1.49700 81.5 26.22 5 -171.138 0.15 24.46 6 -129.965 1.20 1.85478 24.8 24.46 7 52.971 1.15 23.47 8 33.976 1.20 1.52995 63.3 23.09 9 22.209 2.38 1.49700 81.5 22.27 10 34.922 0.97 21.86 11 37.389 2.53 1.49700 81.5 21.68 12 210.122 (variable) 21.26 13 2698.680 1.20 1.69849 42.7 20.32 14 19.441 1.98 1.92286 20.9 19.29 15 27.846 (variable) 18.89 16 (Aperture) ∞ 4.88 18.28 17 -330.153 1.37 1.95375 32.3 17.99 18 -100.710 0.15 17.99 19 2911.242 0.50 1.54812 43.8 17.97 20 51.866 1.83 1.72917 54.7 17.94 21 -74.366 (variable) 17.92 22* -112.030 0.05 1.53110 55.9 17.00 23 -114.811 1.50 1.49230 69.6 16.99 24 42.149 (variable) 16.37 25 -262.895 2.00 1.83707 43.7 16.13 26 -47.464 1.12 16.04 27 -37.120 1.00 1.50424 68.1 15.74 28 -224.938 (variable) 16.30 29 531.967 3.55 1.48749 70.2 24.38 30 -45.239 3.71 24.86 31 -54.376 1.00 1.84666 23.8 25.48 32 -158.660 40.0 26.08 Image plane ∞ Aspheric Data Page 22 K = 0.00000e+00 A 4= 1.34215e-06 A 6= 4.95860e-09 A 8=-7.44395e-11 A10 = 5.04803e-13 Various data Focal length 110.22 F-number: 4.12 Half angle of view (°) 11.11 Image height 21.64 Lens total length 120.00 BF 40.00 Magnification: Infinity -0.5 d12 2.25 10.06 d15 11.83 4.03 d21 1.31 16.68 d24 2.43 3.87 d28 17.22 0.39 Entrance pupil position 48.66 49.04 55.58 52.54 Exit pupil position -38.10 -37.99 -33.06 -36.21 Front principal point position 3.33 2.22 -21.58 -9.87 Back principal point position -70.22 -70.70 -70.79 -73.15 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 56.98 19.13 1.15 -12.22 2 13 -47.77 3.18 2.35 0.59 3 16 50.09 8.72 6.51 -0.60 4 22 -61.97 1.55 0.75 -0.28 5 25 301.75 4.12 -1.24 -4.08 6 29 523.87 8.25 -17.08 -22.91 Single lens data Lens starting surface focal length 1 1 75.57 2 4 65.80 3 6 -43.89 4 8 -125.44 5 9 115.58 6 11 91.07 7 13 -28.04 8 14 62.69 9 17 151.50 10 19 -96.35 11 20 42.16 12 22 -8762.17 13 23 -62.43 14 25 68.90 15 27 -88.32 16 29 85.70 17 31 -98.14 [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 ∞ 1.50 37.31 2 163.453 4.21 1.95375 32.3 36.36 3 -105.073 0.61 35.85 4 38.687 3.58 1.49700 81.5 30.22 5 85.523 2.77 28.52 6 -73.018 1.20 1.85478 24.8 28.25 7 54.590 1.98 26.47 8 56.800 1.20 1.89986 32.7 25.82 9 39.963 3.62 1.49700 81.5 25.11 10 -275.683 0.97 24.66 11 45.194 3.77 1.49700 81.5 23.08 12 -73.681 (variable) 22.29 13 -100.917 1.40 1.53864 66.3 20.94 14 24.305 0.31 1.53110 55.9 19.87 15* 26.331 (variable) 19.85 16 (Aperture) ∞ 2.46 20.02 17 85.791 2.56 1.95375 32.3 20.04 18 -82.798 1.63 19.89 19 -149.009 0.50 1.68444 35.1 19.00 20 94.572 1.62 1.84666 23.8 18.73 21 -103.440 (variable) 18.57 22* -96.988 0.35 1.53110 55.9 15.29 23 -49.415 1.40 1.48741 70.3 15.28 24 31.005 (variable) 14.34 25 50.006 6.09 1.48749 70.2 22.14 26 -21.690 0.15 22.41 27 -22.642 1.00 1.84667 23.8 22.29 28 -357.990 36.15 23.48 Image plane ∞ Aspheric Data Page 15 K = 0.00000e+00 A 4=-4.15065e-06 A 6= 3.96039e-10 A 8=-8.09148e-11 A10 = 3.51171e-13 Page 22 K = 0.00000e+00 A 4= 1.20126e-06 A 6= 4.49914e-08 A 8=-7.71502e-10 A10= 4.64740e-12 Various data Focal length 110.67 F-number: 4.12 Half angle of view (°) 11.06 Image height 21.64 Lens total length 125.00 BF 36.15 Magnification: Infinity -1.0 d12 1.61 18.70 d15 20.89 3.89 d21 5.58 19.15 d24 15.88 2.27 Entrance pupil position 67.40 68.03 113.75 76.21 87.92 Exit pupil position -27.41 -27.39 -21.86 -26.46 -25.21 Front principal point position -14.62 -15.26 -35.08 -20.72 -25.40 Back principal point position -74.52 -74.51 -57.47 -72.23 -68.36 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 50.76 25.40 10.22 -10.76 2 13 -38.55 1.71 0.88 -0.23 3 16 36.62 8.77 3.95 -2.70 4 22 -49.02 1.75 0.89 -0.27 5 25 -467.70 7.23 25.56 19.68 Single lens data Lens starting surface focal length 1 1 67.58 2 4 138.62 3 6 -36.39 4 8 -155.05 5 9 70.50 6 11 56.96 7 13 -36.22 8 14 564.74 9 17 44.51 10 19 -84.46 11 20 58.57 12 22 189.20 13 23 -38.87 14 25 31.92 15 27 -28.59 [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1∞1.50 32.98 2 797.447 1.63 1.95375 32.3 32.39 3 -628.379 0.13 32.13 4 122.066 3.78 1.49700 81.5 31.52 5 -139.354 0.24 30.78 6 -108.510 1.20 1.85478 24.8 30.79 7 -269.097 0.99 30.35 8 70.829 1.20 1.62817 39.1 28.77 9 34.532 4.96 1.49700 81.5 27.49 10 -177.926 0.97 26.75 11 57.960 2.51 1.49700 81.5 25.94 12 1178.009 (variable) 25.57 13 -714.730 1.20 1.80810 46.5 23.52 14 63.755 0.94 1.92286 20.9 22.81 15 73.009 (variable) 22.57 16 (Aperture) ∞ (Variable) 17.34 17 -69.477 1.00 1.69597 50.9 16.79 18 54.133 2.88 16.63 19 98.106 1.63 1.89970 30.6 16.85 20 -37.055 1.00 1.61562 65.2 16.84 21 57.300 (variable) 16.51 22 106.086 5.76 1.49692 81.6 33.16 23 -50.706 0.20 33.62 24 68.722 4.20 1.48749 70.2 34.08 25 -94.099 12.91 34.03 26 -44.117 1.00 1.84667 23.8 29.89 27 250.000 33.73 30.49 Image plane ∞ Various data Focal length 115.85 F-number: 4.12 Half angle of view (°) 10.58 Image height 21.64 Lens total length 140.00 BF 33.73 Magnification: Infinity -1.0 d12 2.12 17.95 d15 18.64 2.84 d16 1.59 32.34 d21 32.10 1.34 Entrance pupil position 57.32 57.73 73.14 62.24 67.58 Exit pupil position -50.36 -50.31 -36.26 -48.47 -45.73 Front principal point position 13.56 11.45 -52.10 -11.44 -27.35 Back principal point position -82.12 -83.29 -73.90 -90.82 -89.83 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 48.34 19.11 8.03 -5.90 2 13 -83.51 2.14 1.12 -0.04 Aperture 16 ∞ 0.00 0.00 -0.00 3 17 -60.66 6.51 -0.29 -5.23 4 22 77.70 24.06 -24.40 -32.99 Single lens data Lens starting surface focal length 1 1 368.69 2 4 131.56 3 6 -213.46 4 8 -108.66 5 9 58.64 6 11 122.56 7 13 -72.38 8 14 519.69 9 17 -43.57 10 19 30.07 11 20 -36.41 12 22 69.89 13 24 82.17 14 26 -44.22 [Numerical Example 7] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 ∞ 1.50 39.03 2 258.701 3.55 1.95375 32.3 38.16 3 -136.563 0.11 37.74 4 47.785 4.70 1.49700 81.5 33.75 5 398.844 1.13 32.11 6 -160.130 1.20 1.85478 24.8 32.10 7 54.937 1.89 30.00 8 53.346 1.20 1.76052 27.2 29.14 9 37.404 5.02 1.49700 81.5 28.15 10 -137.507 0.97 27.42 11 38.276 2.93 1.49700 81.5 24.33 12 288.818 (variable) 23.40 13 -215.253 0.80 1.74322 53.0 20.96 14 21.029 1.85 1.92286 20.9 19.03 15 31.168 (variable) 18.43 16 (Aperture) ∞ 0.60 17.51 17 132.072 2.55 1.95375 32.3 17.46 18 -40.188 0.20 17.34 19 -34.627 1.04 1.48749 70.2 17.32 20 -32.067 1.10 1.84666 23.8 17.09 21 -45.708 (variable) 16.97 22* -98.884 0.05 1.53110 55.9 16.15 23 -229.821 0.90 1.53550 64.6 16.09 24 41.557 (variable) 15.64 25 52.989 4.15 1.48749 70.2 20.27 26 -34.230 8.84 20.61 27 -27.147 1.00 1.87973 27.6 20.73 28 -364.618 30.53 21.85 Image plane ∞ Aspheric Data Page 22 K = 0.00000e+00 A 4=-8.06792e-07 A 6= 3.16734e-08 A 8=-3.66331e-10 A10 = 1.23432e-12 Various data Focal length 105.18 F-number: 4.12 Half angle of view (°) 11.62 Image height 21.64 Lens total length 118.00 BF 30.53 Magnification: Infinity -1.0 d12 2.46 19.56 d15 20.29 3.33 d21 1.23 15.58 d24 16.18 1.77 Entrance pupil position 69.30 70.16 115.26 79.73 91.00 Exit pupil position -21.80 -21.77 -18.96 -21.39 -20.74 Front principal point position -36.93 -36.97 -44.72 -37.80 -39.69 Back principal point position -74.65 -74.20 -51.66 -68.80 -62.93 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 49.34 24.20 8.91 -9.63 2 13 -40.97 2.65 1.56 0.14 3 16 41.79 5.48 2.15 -1.29 4 22 -54.59 0.95 0.44 -0.18 5 25 -34354.01 13.99 10194.75 7852.49 Single lens data Lens starting surface focal length 1 1 94.13 2 4 108.75 3 6 -47.73 4 8 -170.11 5 9 59.73 6 11 88.44 7 13 -25.74 8 14 64.41 9 17 32.54 10 19 785.54 11 20 -131.79 12 22 -326.84 13 23 -65.64 14 25 43.34 15 27 -33.39 [Numerical Example 8] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 ∞ 1.50 33.46 2 61.774 1.20 1.85478 24.8 30.73 3 24.871 8.22 28.30 4 65.249 2.09 1.50159 72.5 27.72 5 -959.980 4.61 27.61 6 73.831 1.20 1.89295 20.4 25.60 7 42.463 4.59 1.49700 81.5 24.92 8 -67.565 0.97 24.47 9 46.549 3.96 1.49700 81.5 22.27 10 -45.571 (variable) 21.49 11 -43.685 0.80 1.73012 54.6 18.62 12 16.537 2.29 1.92286 20.9 16.76 13 31.284 (variable) 16.19 14 (Aperture) ∞ 0.09 17.29 15 47.659 2.85 1.95375 32.3 17.43 16 -61.905 0.60 17.28 17 164.946 3.72 1.54550 65.7 16.58 18 -19.797 1.10 1.74431 27.4 15.93 19 -108.737 (variable) 15.43 20* 67.363 0.29 1.53110 55.9 13.30 21 377.182 0.90 1.81350 44.0 13.28 22 21.019 (variable) 12.71 23 38.634 4.38 1.48749 70.2 18.49 24 -23.053 11.19 18.89 25 -28.319 0.50 1.84668 23.8 19.55 26 91.838 24.18 20.57 Image plane ∞ Aspheric Data Page 20 K = 0.00000e+00 A 4=-1.88646e-05 A 6= 1.83998e-07 A 8=-2.54179e-09 A10 = 1.36793e-11 Various data Focal length 52.00 F-number: 4.12 Half angle of view(°) 22.59 Image height 21.64 Lens total length 115.00 BF 24.18 Magnification: Infinity -1.0 d10 1.77 18.87 d13 20.19 3.13 d19 3.97 9.26 d22 7.82 2.51 Entrance pupil position 34.46 34.80 53.89 38.82 43.72 Exit pupil position -17.37 -17.33 -15.94 -16.88 -16.43 Front principal point position 21.39 20.75 -10.47 13.35 4.93 Back principal point position -27.82 -28.37 -36.58 -33.27 -36.18 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 35.50 28.34 24.34 7.12 2 11 -28.68 3.09 1.24 -0.39 3 14 28.38 8.37 0.65 -4.56 4 20 -33.50 1.19 0.89 0.19 5 23 102.20 16.07 -47.69 -41.92 Single lens data Lens starting surface focal length 1 1 -49.45 2 4 121.89 3 6 -113.98 4 7 53.20 5 9 47.00 6 11 -16.34 7 12 35.38 8 15 28.60 9 17 32.64 10 18 -32.69 11 20 154.37 12 21 -27.39 13 23 30.32 14 25 -25.52 Various values ​​in each numerical example are summarized in Table 1 below.

[0076] [Table 1]

[0077] [Imaging device] Next, an embodiment of a digital still camera (imaging device) 10 using the optical system L0 of each embodiment as an imaging optical system will be described with reference to FIG. 17. In FIG. 17, 13 is a camera body, and 11 is an imaging optical system configured with any of the optical systems L0 described in the first to eighth embodiments. 12 is a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body and receives an optical image formed by the imaging optical system 11 and photoelectrically converts it. The camera body 13 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror. An optical device having the imaging optical system 11 may be attached to the camera body 13, or the camera body 13 and the optical device having the imaging optical system 11 may be an integrated type that cannot be detached.

[0078] In this way, by applying the optical system L0 of each embodiment to an imaging device such as a digital still camera, it is possible to obtain an imaging device with a small lens.

[0079] The disclosure of each of the above embodiments includes the following configurations.

[0080] (Configuration 1) An optical system having a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in this order from an object side to an image side, in which the distance between adjacent lens groups changes during focusing from infinity to a close distance, an aperture stop is disposed on the image side of the second lens group; the first lens group and a final lens group disposed closest to the image side in the optical system are fixed with respect to an image plane during the focusing; a focus lens group that moves during the focusing is disposed on the object side and the image side of the aperture stop; the most image-side focus lens group, which is disposed most image-side among the focus lens groups, moves toward the image side during the focusing; The optical system is capable of achieving an absolute magnification of 0.5 or more at the shortest shooting distance, the final lens group includes a positive lens and a negative lens, Let dF be the sum of the distances on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in each of the focus lens groups, and L be the total lens length of the optical system. 0.025 <dF / L<0.099 An optical system characterized in that the following condition is satisfied: (Configuration 2) Let f1 be the focal length of the first lens group and fL be the focal length of the final lens group. 0.0<|f1 / fL|<1.0 2. The optical system according to claim 1, wherein the following condition is satisfied: (Configuration 3) Let βf be the lateral magnification of the most image-side focus lens unit, and βr be the combined lateral magnification of all the lens units arranged on the image side of the most image-side focus lens unit. 0.1<|(1-βf 2 )×βr 2 |<5.1 3. The optical system according to configuration 1 or 2, wherein the following condition is satisfied: (Configuration 4) Let f be the focal length of the optical system. 0.8 <L / f<2.4 4. The optical system according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) When the focal length of the first lens group is f1 and the focal length of the optical system is f, 0.2 <f1 / f<1.3 5. The optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) Let f2 be the focal length of the second lens group and f be the focal length of the optical system. 0.1<|f2 / f|<2.5 6. The optical system according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) Let f3 be the focal length of the third lens group and f be the focal length of the optical system. 0.2<|f3 / f|<0.8 7. The optical system according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) Let f4 be the focal length of the fourth lens group and f be the focal length of the optical system. 0.1<|f4 / f|<0.9 8. The optical system according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) When the imaging magnification at the shortest imaging distance of the optical system is β, |β|≧0.5 9. The optical system according to any one of configurations 1 to 8, wherein the following condition is satisfied: (Configuration 10) The optical system according to any one of configurations 1 to 9, wherein each of the focus lens groups is composed of four or less lenses. (Configuration 11) 11. The optical system according to any one of configurations 1 to 10, wherein the final lens group comprises, in order from the object side to the image side, a positive subgroup and a negative subgroup. (Configuration 12) 12. The optical system according to any one of configurations 1 to 11, wherein the first lens group has positive refractive power. (Configuration 13) 13. The optical system described in any one of configurations 1 to 12, characterized in that the number of focus lens groups among the focus lens groups arranged on the object side of the aperture stop is 1, and the number of focus lens groups among the focus lens groups arranged on the image side of the aperture stop is 1. (Configuration 14) 14. The optical system according to any one of configurations 1 to 13, wherein among the focus lens groups, a focus lens group arranged closest to the object side of the focus lens groups arranged on the image side of the aperture stop has negative refractive power. (Configuration 15) 15. The optical system according to any one of configurations 1 to 14, wherein the first lens group includes a subgroup that moves in a direction including a component perpendicular to the optical axis during image blur correction. (Configuration 16) the optical system includes, in order from an object side to an image side, the first lens group, the second lens group, the aperture stop, the third lens group, and the fourth lens group, 16. The optical system according to any one of configurations 1 to 15, wherein the aperture stop is fixed with respect to the image plane during the focusing. (Configuration 17) 16. The optical system according to any one of configurations 1 to 15, characterized in that the optical system comprises the first lens group, the second lens group, the third lens group, the fourth lens group, and a fifth lens group, arranged in this order from the object side to the image side. (Configuration 18) The optical system according to any one of configurations 1 to 15, characterized in that the optical system comprises, in order from the object side to the image side, the first lens group, the second lens group, the third lens group, the fourth lens group, the fifth lens group, and a sixth lens group. (Configuration 19) 19. An imaging apparatus comprising the optical system according to any one of configurations 1 to 18, and an imaging element that images an object via the optical system. (Configuration 20) 19. An optical device comprising the optical system according to any one of configurations 1 to 18, and capable of being attached to and detached from an imaging device.

[0081] Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0082] Optical system L0 First lens group L1 Second lens group L2 Third lens group L3 Fourth lens group L4

Claims

1. An optical system having a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in order from the object side to the image side, and in which the distance between adjacent lens groups changes during focusing from infinity to a short distance, an aperture stop is arranged on the image side of the second lens group, the first lens group and the final lens group arranged on the most image side in the optical system are fixed with respect to the image plane during focusing, a focus lens group that moves during focusing is arranged on the object side and the image side of the aperture stop, the most image-side focus lens group arranged on the most image side among the focus lens groups moves to the image side during focusing, the optical system can achieve a shooting magnification at the shortest shooting distance of 0.5 times or more in absolute value, the final lens group includes a positive lens and a negative lens, when the sum of the distances on the optical axis from the most object-side lens surface to the most image-side lens surface in each of the focus lens groups is dF, the overall length of the lenses of the optical system is L, the focal length of the fourth lens group is f4, and the focal length of the optical system is f, 0.025 < dF / L < 0.099 0.1 < |f4 / f| < 0.9 An optical system characterized by satisfying the conditional expressions.

2. When the focal length of the first lens group is f1 and the focal length of the final lens group is fL, 0.0 < |f1 / fL| < 1.0 The optical system according to claim 1, characterized by satisfying the conditional expressions.

3. When the lateral magnification of the most image-side focus lens group is βf and the combined lateral magnification of all the lens groups arranged on the image side of the most image-side focus lens group is βr, 0.1 < |(1 - βf ２ ) × βr ２ | < 5.1 The optical system according to claim 1, characterized by satisfying the conditional expressions.

4. 0.8 < L / f < 2.4 The optical system according to claim 1, characterized by satisfying the conditional expressions.

5. When the focal length of the first lens group is f1, 0.2 < f1 / f < 1.3 The optical system according to claim 1, characterized by satisfying the conditional expressions.

6. When the focal length of the second lens group is f2, 0.1 < |f2 / f| < 2.5 The optical system according to claim 1, characterized by satisfying the conditional expressions.

7. When the focal length of the third lens group is f3, 0.2 < |f3 / f| < 0.8 The optical system according to claim 1, characterized by satisfying the conditional expressions.

8. When the imaging magnification at the shortest shooting distance of the optical system is β, ｜β｜≧０．５ The optical system according to claim 1, characterized in that it satisfies the following conditional expression.

9. The focusing lens group of the optical system according to claim 1, wherein each focusing lens group is composed of 4 or fewer lenses.

10. The final lens group of the optical system according to claim 1, which is composed of a positive subgroup and a negative subgroup arranged in order from the object side to the image side.

11. The first lens group of the optical system according to claim 1, which has a positive refractive power.

12. The number of focusing lens groups arranged on the object side of the aperture stop among the focusing lens groups is 1, and the number of focusing lens groups arranged on the image side of the aperture stop among the focusing lens groups is 1. The optical system according to claim 1, characterized in that it is 1.

13. Among the focusing lens groups arranged on the image side of the aperture stop in the focusing lens group, the focusing lens group arranged closest to the object side has a negative refractive power. The optical system according to claim 1, characterized in that it has a negative refractive power.

14. The first lens group of the optical system according to claim 1, which includes a subgroup that moves in a direction including a component perpendicular to the optical axis during image blur correction.

15. The optical system is composed of the first lens group, the second lens group, the aperture stop, the third lens group, and the fourth lens group arranged in order from the object side to the image side. The optical system according to claim 1, characterized in that the aperture stop is fixed with respect to the image plane during focusing.

16. The optical system according to claim 1, which is composed of the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group arranged in order from the object side to the image side.

17. The optical system according to claim 1, which is composed of the first lens group, the second lens group, the third lens group, the fourth lens group, the fifth lens group, and the sixth lens group arranged in order from the object side to the image side.

18. An imaging device, comprising the optical system according to any one of claims 1 to 17, and an imaging element that images an object through the optical system.

19. An optical device, comprising the optical system according to any one of claims 1 to 17, and being detachable from the imaging device.

Images