Optical system and imaging device having the same

Abstract

To provide a compact and lightweight optical system having high optical performance.SOLUTION: An optical system L0 comprises at least one focus lens group that moves in focusing. A lens group arranged closest to an object side among the at least one focus lens group is a first focus lens group Lfo, one or more lens groups arranged closer to the object side than the first focus lens group are a front group LF, and one or more lens groups arranged closer to the image side than the first focus lens group and the first focus lens group are a rear group LR. A focal distance f1 of the front group, a focal distance f of the optical system, a distance Dtotal on an optical axis from a lens surface closest to the object side in the optical system to a lens surface closest to the image side in the optical system, a distance skd on the optical axis from the lens surface closest to the image side in the optical system to an image surface, and a focal distance f2 of the rear group satisfy predetermined conditional inequalities.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] An optical system used in an imaging device is required to have a high optical performance that is small and lightweight as a whole and can favorably correct various aberrations including chromatic aberration. As a small optical system, a so-called telephoto type optical system in which a lens group with a positive refractive power is arranged on the object side and a lens group with a negative refractive power is arranged on the image side is known. However, in the telephoto type optical system, as the focal length increases, the entire system becomes larger, and the use of large-diameter lenses and heavy lenses tends to increase the weight of the entire optical system.

[0003] Patent Document 1 proposes an optical system that attempts to reduce weight by devising the configuration of a lens arranged on the object side of an aperture stop.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the optical system described in Cited Document 1 cannot be said to be sufficient in terms of weight reduction.

[0006] As a method for further reducing the weight of an optical system, there are a method of reducing the number of lenses constituting the optical system and a method of configuring the optical system with lenses having a weak refractive power. However, in the former case, the refractive power of each lens becomes strong and various aberrations tend to deteriorate. In the latter case, the overall length of the lenses in the optical system becomes long and the optical system tends to become large.

[0007] This invention provides an optical system that is compact, lightweight, and possesses high optical properties. [Means for solving the problem]

[0008] One aspect of the present invention is an optical system that includes at least one group of focus lenses that move during focusing, The optical system consists of a front group and a rear group, The first focusing lens group is the one of the at least one focusing lens groups that is positioned closest to the object, and one or more lens groups that are positioned closer to the object than the first focusing lens group are... The aforementioned The front group, one or more lens groups positioned closer to the image side than the first focusing lens group, and the first focusing lens group The aforementioned When the rear group is defined as the front group, the focal length of the front group is f1, the focal length of the optical system is f, the distance along the optical axis from the lens surface closest to the object in the optical system to the lens surface closest to the image in the optical system is Dtotal, the distance along the optical axis from the lens surface closest to the image in the optical system to the image plane is skd, and the focal length of the rear group is f2, 0. 4 3 <f1 / f<0.5 5 <Dtotal / skd<15 9.5 <f 2 / |f×f1+f×f2-f1×f2|<20.0 It is characterized by satisfying the following conditional expression.

[0009] Other objects and features of the present invention are described in the following embodiments. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an optical system that is small, lightweight, and has high optical performance. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view of the optical system of Example 1 when it is in focus at infinity. [Figure 2]It is an aberration diagram when the optical system of Example 1 is focused at infinity. [Figure 3] It is a cross-sectional view when the optical system of Example 2 is focused at infinity. [Figure 4] It is an aberration diagram when the optical system of Example 2 is focused at infinity. [Figure 5] It is a cross-sectional view when the optical system of Example 3 is focused at infinity. [Figure 6] It is an aberration diagram when the optical system of Example 3 is focused at infinity. [Figure 7] It is a cross-sectional view when the optical system of Example 4 is focused at infinity. [Figure 8] It is an aberration diagram when the optical system of Example 4 is focused at infinity. [Figure 9] It is a cross-sectional view when the optical system of Example 5 is focused at infinity. [Figure 10] It is an aberration diagram when the optical system of Example 5 is focused at infinity. [Figure 11] It is a diagram for explaining the conditional expression (3) of the present invention. [Figure 12] It is a schematic diagram of the main part of an imaging device equipped with the optical systems of Examples 1 to 5.

Modes for Carrying Out the Invention

[0012] Hereinafter, examples of the optical system of the present invention and an imaging device having the same will be described based on the accompanying drawings.

[0013] FIG. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 are cross-sectional views when the optical systems L0 of Examples 1 to 5 are focused at infinity, respectively. The optical system L0 of each example is an optical system used in an imaging device such as a digital video camera, a digital still camera, a broadcast camera, a silver halide film camera, a surveillance camera, etc.

[0014] In each cross-sectional view of the lens, the left side is the object side and the right side is the image side. The optical system L0 of each embodiment is composed of multiple lens groups. In this specification, a lens group is a collection of lenses that move or remain stationary as a single unit during focusing. A lens group may consist of one lens or multiple lenses. Furthermore, a lens group may include an aperture diaphragm.

[0015] The optical system L0 of each embodiment consists of a front group LF with positive refractive power and a rear group LR with negative refractive power, arranged in order from the object side to the image side.

[0016] In each lens cross-sectional view, SP is the aperture diaphragm, which determines (limits) the light beam at the open F-number (Fno). IP is the image plane, and when the optical system L0 of each embodiment is used as the photographic 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 CMOS sensor is placed on it. When the optical system L0 of each embodiment is used as the photographic optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP.

[0017] Furthermore, in the optical system L0 of each embodiment, the lens group Lfo is configured to move when focusing from infinity to the closest point. The focusing lens group Lfo moves as shown by the arrows in each lens cross-sectional view. Note that the optical system L0 of each embodiment may include at least one focusing lens group that moves during focusing. The focusing lens group Lfo is positioned closest to the object among the at least one focusing lens group.

[0018] Figures 2, 4, 6, 8, and 10 are aberration diagrams of the optical systems L0 of Examples 1 to 5 at infinity focus, respectively. In the spherical aberration diagram, Fno is the F number and indicates the amount of spherical aberration for the d line (wavelength 587.6 nm) and the g line (wavelength 435.8 nm). In the astigmatism diagram, dS indicates the amount of astigmatism at the sagittal image plane, and dM indicates the amount of astigmatism at the meridional image plane. The distortion diagram shows the amount of distortion for the d line. The chromatic aberration diagram shows the amount of chromatic aberration at the g line. ω is the imaging half-angle of view (°).

[0019] Next, we will describe the characteristic configurations of the optical systems in each embodiment.

[0020] The optical system L0 of each embodiment is an optical system that includes at least one focusing lens group that moves during focusing. In the optical system L0 of each embodiment, the focusing lens group that is positioned closest to the object is designated as the first focusing lens group Lfo, and one or more lens groups positioned closer to the object than the first focusing lens group Lfo are designated as the front group LF. Furthermore, one or more lens groups positioned closer to the image than the first focusing lens group Lfo, and the first focusing lens group Lfo, are designated as the rear group LR. The optical system L0 of each embodiment is a telephoto type optical system. The rear group LR may also include a lens group LIS that moves in a direction including a component perpendicular to the optical axis during image shake correction.

[0021] Furthermore, the optical system L0 of each embodiment satisfies the following conditions (1) to (3).

[0022] 0.3 <f1 / f<0.5 ···(1) 5 <Dtotal / skd<15 ···(2) 9.5 <f 2 / |f×f1+f×f2-f1×f2|<20.0 ···(3) Here, f1 is the focal length of the front group LF. f is the focal length of the optical system L0. Dtotal is the distance along the optical axis from the lens surface closest to the object in the optical system L0 to the lens surface closest to the image in the optical system L0. skd is the distance along the optical axis from the lens surface closest to the image in the optical system L0 to the image plane IP (back focus). f2 is the focal length of the rear group LR.

[0023] Condition (1) specifies the ratio of the focal length f1 of the front lens group LF to the focal length f of the optical system L0. By satisfying condition (1), the image point created by the light passing through the front lens group LF can be located near the first focusing lens group Lfo or lens group LIS. This reduces the diameter of the light beam in the first focusing lens group Lfo and lens group LIS, allowing the lens groups Lfo and LIS to be made smaller and lighter. Furthermore, the smaller and lighter Lfo and LIS lenses allow for the use of smaller control mechanisms. This makes it possible to make the optical system L0 smaller and lighter. If the focal length f1 becomes smaller than the lower limit of condition (1), the image point is created on the object side of the first focusing lens group Lfo, so the first focusing lens group Lfo and lens group LIS cannot be made smaller. Also, the refractive power becomes too large, and spherical aberration and axial chromatic aberration worsen in particular. When the focal length f1 increases beyond the upper limit of condition (1), the image point of the front group LF approaches the image plane IP of the optical system L0, and is positioned on the image side of the first focusing lens group Lfo and lens group LIS. Therefore, the diameters of lens groups Lfo and LIS cannot be reduced.

[0024] Condition (2) defines the ratio of the distance Dtotal on the optical axis from the lens surface closest to the object to the lens surface closest to the image in the optical system L0 to the back focus skd. When condition (1) is satisfied, the lens group LIS and the first focusing lens group Lfo must be positioned near the image point of the front lens group LF. However, if the back focus skb is long, even if condition (1) is satisfied, the image point of the front lens group LF will be on the image side of the lens group LIS and the first focusing lens group Lfo. This increases the diameter of the lens group LIS and the first focusing lens group Lfo, reducing the effect of miniaturization and weight reduction. If the back focus skd is long below the lower limit of condition (2), the image point of the front lens group LF will be on the image side of the lens group LIS and the first focusing lens group Lfo, reducing the effect of miniaturization and weight reduction. Also, if the back focus skd is short above the upper limit of condition (2), the lens group LIS and the first focusing lens group Lfo will be much closer to the image plane IP. As a result, electromagnetic waves emitted by actuators controlling the lens group LIS and the first focus lens group Lfo cause noise to be generated in the image on the image plane IP, leading to a decrease in image quality.

[0025] Conditional equation (3) defines the relationship between the focal length f1 of the front group LF, the focal length f2 of the rear group LR, and the focal length f of the optical system L0. Figure 11 is a diagram illustrating conditional equation (3). In Figure 11, Sf represents the principal point position of the front group LF, and Sr represents the principal point position of the rear group LR. Light from the subject (not shown) enters the front group LF, is refracted at the principal point position Sf of the front group LF, and is imaged at the image point LFI of the front group LF. The image formed at the image point LFI is refracted at the principal point position Sr of the rear group LR and is imaged on the image plane IP of the optical system L0. At the principal point position Sr of the rear group LR, the light beam is lifted by a negative refractive force. This causes the peripheral rays of the on-axial light beam to rise. It is known that the region where the peripheral rays of the on-axial light beam are large has a large effect on spherical aberration and axial chromatic aberration. By bringing the principal points of the front group LF and the rear group LR closer together, the peripheral beam of the axial beam increases, the rays on the image side of the front group LF become higher, and it becomes easier to correct axial chromatic aberration and spherical aberration on the image side of the front group LF. The focal length f of the optical system L0 can be expressed as follows, given the focal length f1 of the front group LF, the focal length f2 of the rear group LR, and the distance D between the principal points.

[0026] 1 / f=1 / f1+1 / f2-D×(1 / f1)×(1 / f2) By rearranging the above equation, we obtain the following equation. By rearranging this, we obtain the following equation.

[0027] 1 / D = f / (f × f1 + f × f2 - f1 × f2) To make it dimensionless, multiplying both sides of the above equation by the focal length f of the optical system L0 yields the following equation.

[0028] f / D=f 2 / (f×f1+f×f2-f1×f2) As the distance between principal points D approaches to satisfy condition (3), the ray height on the image side of the front group LF increases, making it easier to correct axial chromatic aberration on the image side of the front group LF. This reduces the need to use highly anomalous dispersion glass in the portion of the front group LF with a large lens diameter on the object side. Generally, highly anomalous dispersion glass has a high specific gravity, resulting in a heavy lens. However, by satisfying condition (3), the need to use highly anomalous dispersion glass on the object side of the front group LF decreases, allowing for a lighter optical system L0. When the principal point position Sr of the rear group LR moves further toward the image side than the principal point position Sf of the front group LF, below the lower limit of condition (3), the amount of upward deflection of peripheral rays in the axial beam decreases. When the amount of upward deflection decreases, the peripheral rays in the axial beam passing through the portion of the front group LF that is on the image side of the principal point position Sf become lower. When this value decreases, the amount of correction for axial chromatic aberration and spherical aberration in the image-side portion of the front LF lens group becomes smaller, and the amount of chromatic aberration correction shared by the larger diameter portion of the front LF lens group on the object side becomes larger. This necessitates the use of highly anomalous dispersion glass material on the object side of the front LF lens group. Furthermore, if the principal point position Sr of the rear LR lens group and the principal point position Sf of the front LF lens group become closer than the upper limit of condition (3), it deviates from the power distribution of a telephoto lens, making aberration correction difficult.

[0029] Furthermore, it is more preferable to set the numerical range of conditional expressions (1) to (3) to the range of conditional expressions (1a) to (3a) below.

[0030] 0.32 <f1 / f<0.50 ···(1a) 5.5 <Dtotal / skd<14.0 ···(2a) 10.0 <f 2 / |f×f1+f×f2-f1×f2|<19.5 ···(3a) Furthermore, it is even more preferable that the numerical ranges of conditional expressions (1) to (3) be within the ranges of the following conditional expressions (1b) to (3b).

[0031] 0.35 <f1 / f<0.50 ···(1b) 6 <Dtotal / skd<13 ···(2b) 10.5 <f 2 / |f×f1+f×f2-f1×f2|<19.0 ···(3b) Next, we will describe the configurations that are preferable to satisfy in the optical system L0 of each embodiment.

[0032] In telephoto optical systems, the peripheral rays of the axial light beam passing through lenses positioned relatively close to the object have a higher pass height. Therefore, to effectively correct axial chromatic aberration and spherical aberration, the configuration of lenses positioned relatively close to the object is important.

[0033] In the optical system L0 of each embodiment, it is preferable that the front group LF includes a positive lens G1p positioned closest to the object. This allows for miniaturization of the optical system L0 and reduces the occurrence of various aberrations such as spherical aberration.

[0034] Furthermore, it is preferable that the aperture diaphragm SP is located on the image side or object side of the first focusing lens group Lfo. Located on the image side of the first focusing lens group Lfo makes it easier to reduce the diameter of the aperture diaphragm SP, thereby miniaturizing the lens device including the optical system L0. Located on the object side of the first focusing lens group Lfo makes it easier to secure peripheral light when the aperture diaphragm SP is in a small aperture state. More preferably, the aperture diaphragm SP is located adjacent to the first focusing lens group Lfo on either the image side or object side of the first focusing lens group Lfo.

[0035] Furthermore, in the optical system L0 of each embodiment, it is preferable that all optical surfaces having power are refractive surfaces. This makes it possible to easily obtain optical performance equivalent to or better than that when the optical surfaces having power are composed of diffractive optical elements or reflective surfaces, with a lower manufacturing difficulty.

[0036] Furthermore, in the optical system L0 of each embodiment, the rear group LR may include a lens group LIS that moves in a direction including a component perpendicular to the optical axis during image shake correction. In particular, it is preferable that the lens group LIS is located on the image side of the first focusing lens group Lfo, which is located closest to the object in the rear group LR. By making the portion that moves during image shake correction a part of the rear group LR with a relatively small lens diameter, the actuator for driving can be made smaller and the lens device can be made lighter.

[0037] Next, we will describe the conditions that the optical system L0 of each embodiment preferably satisfies. The optical system L0 of each embodiment preferably satisfies one or more of the following conditional equations (4) to (7).

[0038] 0.0<(Dtotal+skd) / f<1.0 ···(4) 0.40 <D1 / Dtotal<0.75 ···(5) 1.45 <NG1p<1.55 ···(6) 55.0 < νG1p < 75.0 ···(7) Here, D1 is the distance along the optical axis from the lens surface closest to the object in the front LF group to the lens surface closest to the image in the front LF group (the total length of the front LF lens). NG1p is the refractive index of the material of the positive lens G1p located closest to the object in the front LF group. νG1p is the Abbe number of the material of the positive lens G1p located closest to the object in the front LF group.

[0039] Conditional equation (4) specifies the ratio of the focal length f of the optical system L0 to the total lens length (Dtotal + skd). If the total lens length exceeds the upper limit of conditional equation (4), the optical system L0 becomes larger, which is undesirable. If the total lens length falls below the lower limit of conditional equation (4), the refractive power of each lens constituting the optical system L0 is increased, making it difficult to correct various aberrations, including chromatic aberration, which is also undesirable.

[0040] Conditional equation (5) specifies the ratio of the total lens length D1 of the front LF group to the distance Dtotal. If the total lens length D1 of the front LF group exceeds the upper limit of conditional equation (5), the rear LR group becomes smaller, the number of usable lenses decreases, and it becomes difficult to correct various aberrations such as chromatic aberration and field distortion, which is undesirable. If the total lens length D1 of the front LF group becomes shorter than the lower limit of conditional equation (5), the position of the image point by the front LF group shifts towards the object, making it impossible to reduce the diameter of the first focusing lens group Lfo and lens group LIS, and the optical system L0 becomes larger, which is undesirable.

[0041] Conditional equation (6) specifies the refractive index NG1p of the positive lens G1p, which is positioned closest to the object in the front group LF. By using a material with an appropriate refractive index, the weight of the optical system L0 is reduced. In general optical materials, the specific gravity tends to increase as the refractive index increases. Therefore, if the refractive index of the material of the positive lens G1p exceeds the upper limit of conditional equation (6), the specific gravity of the positive lens G1p, which has a large diameter, will increase, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the refractive index of the material of the positive lens G1p falls below the lower limit of conditional equation (6), the positive refractive power of the positive lens G1p will be weak, making it difficult to miniaturize the optical system L0, which is also undesirable.

[0042] Conditional equation (7) specifies the Abbe number νG1p of the material of the positive lens G1p located closest to the object in the front LF group. By appropriately setting the Abbe number, both high optical performance and weight reduction can be achieved. In general optical materials, the specific gravity tends to increase as the Abbe number of the material increases. Therefore, if the Abbe number νG1p exceeds the upper limit of conditional equation (7), the specific gravity of the positive lens G1p located closest to the object in the front LF group becomes large, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the Abbe number νG1p of the material of the positive lens G1p located closest to the object in the front LF group becomes small, below the lower limit of conditional equation (7), it becomes difficult to correct chromatic aberrations such as lateral chromatic aberration, which is also undesirable.

[0043] Furthermore, it is more preferable that the numerical ranges of conditional expressions (4) to (7) be within the ranges of conditional expressions (4a) to (7a) below.

[0044] 0.50<(Dtotal+skd) / f<0.99 (4a) 0.42 <D1 / Dtotal<0.73 ···(5a) 1.452 <NG1p<1.548 ···(6a) 55.5 < νG1p < 74.0 ···(7a) Furthermore, it is even more preferable that the numerical ranges of conditional expressions (4) to (7) be within the ranges of the following conditional expressions (4b) to (7b).

[0045] 0.90<(Dtotal+skd) / f<0.98 ···(4b) 0.45 <D1 / Dtotal<0.71 ···(5b) 1.455 <NG1p<1.545 ···(6b) 56.0 < νG1p < 73.0 ···(7b) Next, the optical system L0 of each embodiment will be described in detail.

[0046] In the optical system L0 of each embodiment, the first focusing lens group Lfo moves during focusing. In the optical system L0 of each embodiment, the front group LF with positive refractive power remains stationary during focusing. The rear group LR with negative refractive power consists of the first focusing lens group Lfo, which moves during focusing, and a group of lenses that remain stationary during focusing, arranged sequentially from the object side to the image side. The lens group that remains stationary during focusing in the rear group LR consists of a partial lens group LRa that remains stationary during focusing, a lens group LIS for image shake correction, and a partial lens group LRb that remains stationary during focusing, arranged sequentially from the object side to the image side. The first focusing lens group Lfo moves towards the image side when focusing from infinity to the closest focus.

[0047] In the above embodiments, only the first focus lens group Lfo moved during focusing. However, as a modification, the first focus lens group Lfo may be positioned as the focus lens group closest to the object, and multiple focus lens groups may be arranged (floating focus).

[0048] The numerical values ​​corresponding to Examples 1 to 5 are shown below.

[0049] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance along the optical axis) between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the light incidence side. Furthermore, nd represents the refractive index of each optical element with respect to the d-line, and νd represents the Abbe number of the optical element. Note that the Abbe number νd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC, respectively. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0050] In each numerical example, d, focal length (mm), F-number, and half-angle of view (°) are all values ​​when the optical system L0 of each example is focused on an object at infinity. "Back focus skd" is the distance along the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed in terms of air equivalent length. "Total lens length" is the length obtained by adding the back focus to the distance along the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final surface. "Lens group" includes not only cases where it is composed of multiple lenses, but also cases where it is composed of a single lens.

[0051] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd 1 122.716 12.91 1.48749 70.2 2 1348.168 90.00 3 78.259 12.67 1.48749 70.2 4 -126.485 0.10 5 -129.028 1.92 1.80100 35.0 6 55.042 0.10 7 53.233 10.23 1.48749 70.2 8 ∞ 8.00 9 51.407 8.73 1.89286 20.4 10 1720.777 0.00 11 1490.111 1.92 1.75520 27.5 12 29.405 10.50 1.49700 81.5 13 409.644 9.40 14 (aperture) ∞ 1.08 15 -1703.479 1.22 1.58913 61.1 16 40.110 17.58 17 242.752 1.92 1.84666 23.8 18 229.052 5.00 1.51633 64.1 19 -73.816 1.50 20 673.870 3.00 1.80518 25.4 21 -64.980 1.00 1.60311 60.6 22 34.400 4.83 23 -52.531 1.00 1.49700 81.5 24 80.978 1.50 25 71.256 2.95 1.51633 64.1 26 -122.327 20.64 27 51.542 10.00 1.59551 39.2 28 -57.002 1.09 29 -58.134 2.00 1.84666 23.8 30 -429.173 (variable) Image plane ∞ Various data Zoom ratio 1.00 Focal length 294.99 F-number 2.90 Half-angle (°): 4.19 Image height 21.64 Lens length: 280.25 skd 37.47 Lens group data Group starting plane focal length 1 1 128.26 2 15 -183.20 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd 1 113.214 13.69 1.48749 70.2 2 1149.016 88.55 3 95.729 11.92 1.48749 70.2 4 -94.033 0.10 5 -96.293 1.92 1.80100 35.0 6 52.268 0.10 7 46.700 11.17 1.48749 70.2 8 ∞ 8.00 9 44.938 10.45 1.96300 24.1 10 -506.685 0.42 11 -294.415 1.92 1.85026 32.3 12 26.177 11.00 1.49700 81.5 13 1384.885 9.40 14 (aperture) ∞ 0.99 15 15695.526 1.22 1.60311 60.6 16 40.244 15.68 17 108.569 1.92 1.96300 24.1 18 75.480 3.70 1.51633 64.1 19 -81.581 1.50 20 -649.033 3.00 1.84666 23.8 21 -60.180 1.00 1.60311 60.6 22 35.567 3.06 23 -55.308 1.00 1.49700 81.5 24 78.530 4.93 25 63.078 4.71 1.51742 52.4 26 -118.498 15.91 27 52.637 10.00 1.59551 39.2 28 -59.158 2.11 29 -56.128 2.00 1.96300 24.1 30 -237.718 Image plane ∞ Various data Zoom ratio 1.00 Focal length 292.99 F-number 2.90 Half-angle (°): 4.22 Image height 21.64 Lens length: 278.34 skd 36.99 Lens group data Group starting plane focal length 1 1 136.07 2 15 -213.44 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd 1 111.047 13.22 1.48749 70.2 2 939.402 88.70 3 92.491 12.07 1.48749 70.2 4 -94.708 0.10 5 -96.914 1.92 1.80100 35.0 6 51.262 0.10 7 46.260 11.21 1.48749 70.2 8 ∞ 8.00 9 44.315 10.54 1.96300 24.1 10 -494.248 0.39 11 -295.934 1.92 1.85026 32.3 12 25.812 11.00 1.49700 81.5 13 1223.691 9.40 14 (aperture) ∞ 0.99 15 9571.562 1.22 1.60311 60.6 16 38.708 15.25 17 111.023 1.92 1.96300 24.1 18 78.609 3.47 1.51633 64.1 19 -77.051 1.50 20 -764.742 3.00 1.84666 23.8 21 -64.373 1.00 1.60311 60.6 22 34.846 3.19 23 -52.117 1.00 1.49700 81.5 24 84.371 6.09 25 60.370 5.26 1.51742 52.4 26 -115.117 15.90 27 56.356 10.00 1.59551 39.2 28 -60.220 1.03 29 -58.485 2.00 1.96300 24.1 30 -214.845 Image plane ∞ Various data Zoom ratio 1.00 Focal length 293.00 F-number 2.90 Half-angle (°): 4.22 Image height 21.64 Lens length: 278.35 skd 36.99 Lens group data Group starting plane focal length 1 1 134.13 2 15 -301.35 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd 1 110.964 13.26 1.48749 70.2 2 890.444 89.18 3 91.352 12.14 1.48749 70.2 4 -94.607 0.10 5 -96.882 1.92 1.80100 35.0 6 50.928 0.10 7 45.930 11.29 1.48749 70.2 8 ∞ 8.00 9 44.251 10.60 1.96300 24.1 10 -447.035 0.40 11 -276.650 1.92 1.85026 32.3 12 25.710 11.00 1.49700 81.5 13 1365.203 9.40 14 (aperture) ∞ 0.98 15 5629.925 1.22 1.60311 60.6 16 38.236 15.11 17 105.553 1.92 1.96300 24.1 18 73.989 3.48 1.51633 64.1 19 -78.549 1.50 20 -543.782 3.00 1.84666 23.8 21 -61.440 1.00 1.60311 60.6 22 35.134 3.18 23 -52.054 1.00 1.49700 81.5 24 83.908 5.87 25 58.623 5.39 1.51742 52.4 26 -109.305 17.07 27 54.746 10.00 1.59551 39.2 28 -64.126 1.31 29 -60.702 2.00 1.96300 24.1 30 -255.434 Image plane ∞ Various data Zoom ratio 1.00 Focal length 293.00 F-number 2.90 Half-angle (°): 4.22 Image height 21.64 Lens length: 278.35 skd 35.00 Lens group data Group starting plane focal length 1 1 133.69 2 15 -278.18 [Numerical Example 5] Unit: mm Surface data Face number rd nd νd 1 206.547 14.75 1.48749 70.2 2 -2206.441 115.68 3 157.775 12.00 1.48749 70.2 4 -278.814 0.13 5 -268.771 2.55 1.80100 35.0 6 142.657 0.10 7 94.917 11.94 1.48749 70.2 8 ∞ 10.67 9 80.716 8.00 1.92286 20.9 10 249.307 0.67 11 334.047 2.55 1.68893 31.1 12 41.765 14.80 1.43875 94.7 13 415.980 12.53 14 (aperture) ∞ 1.36 15 -856.937 1.63 1.62041 60.3 16 73.775 56.00 17 205.479 2.00 1.91082 35.3 18 37.677 6.38 1.72000 46.0 19 -124.441 2.00 20 276.456 3.61 1.65844 50.9 21 -54.338 1.33 1.49700 81.5 22 35.712 7.80 23 -50.929 1.00 1.49700 81.5 24 132.355 2.00 25 53.978 7.00 1.51633 64.1 26 -84.737 30.74 27 -33.395 1.50 1.59551 39.2 28 -39.767 0.10 29 52.177 2.67 1.80518 25.4 30 79.069 (Variable) Image plane ∞ Various data Zoom ratio 1.00 Focal length 390.00 F-number 2.90 Half-angle (°): 3.18 Image height 21.64 Lens length: 370.50 skd 37.00 Lens group data Group starting plane focal length 1 1 175.50 2 15 -390.00 The various values ​​in each numerical example are summarized in Table 1 below.

[0052] [Table 1]

[0053] [Imaging device] Next, an embodiment of a digital still camera (imaging device) 10 using the optical system L0 of the present invention as an imaging optical system will be described with reference to Figure 12. In Figure 12, 13 is the camera body, and 11 is the imaging optical system composed of any of the optical systems L0 described in Embodiments 1 to 5. 12 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, which is built into the camera body 13 and receives the optical image formed by the imaging optical system 11 and converts it into photoelectric light. The camera body 13 may be a so-called single-lens reflex camera with a quick-turn mirror, or a so-called mirrorless camera without a quick-turn mirror.

[0054] By applying the optical system of the present invention to an imaging device such as a digital still camera, an imaging device with a lightweight lens can be obtained.

[0055] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various combinations, modifications, and changes are possible within the scope of its essence. [Explanation of Symbols]

[0056] LF front group LR rear group LFO First Focusing Lens Group

Claims

1. An optical system including at least one group of focusing lenses that moves during focusing, The optical system consists of a front group and a rear group, The group of at least one focus lens group positioned closest to the object is referred to as the first focus lens group, one or more lens groups positioned closer to the object than the first focus lens group are referred to as the front group, and one or more lens groups positioned closer to the image than the first focus lens group, along with the first focus lens group, are referred to as the rear group. When the focal length of the front group is f1, the focal length of the optical system is f, the distance along the optical axis from the lens surface closest to the object in the optical system to the lens surface closest to the image in the optical system is Dtotal, the distance along the optical axis from the lens surface closest to the image in the optical system to the image plane is skd, and the focal length of the rear group is f2, 0.43<f1 / f<0.5 5<Dtotal / skd<15 9.5<f ２ / |f×f1+f×f2-f1×f2|<20.0 An optical system characterized by satisfying the following conditional equation.

2. 0.0<(Dtotal+skd) / f<1.0 The optical system according to claim 1, characterized in that it satisfies the following condition.

3. When D1 is the distance along the optical axis from the lens surface closest to the object in the front group to the lens surface closest to the image in the front group, 0.40<D1 / Dtotal<0.75 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. The optical system according to any one of claims 1 to 3, characterized in that the front group includes a positive lens positioned closest to the object.

5. When the refractive index of the material of the positive lens is NG1p, 1.45<NG1p<1.55 The optical system according to claim 4, characterized in that it satisfies the following condition.

6. When the Abbe number of the material of the positive lens is νG1p, 55.0<νG1p<75.0 The optical system according to claim 4 or 5, characterized in that it satisfies the following conditional expression.

7. The optical system according to any one of claims 1 to 6, characterized in that the rear group includes a lens group that moves in a direction including a component perpendicular to the optical axis when correcting image shake.

8. The optical system according to any one of claims 1 to 7, characterized in that an aperture diaphragm is arranged adjacent to the object side or image side of the first focusing lens group.

9. The optical system according to any one of claims 1 to 8, characterized in that all optical surfaces having power are refractive surfaces.

10. An imaging device characterized by having an optical system according to any one of claims 1 to 9 and an image sensor that receives an image formed by the optical system.

Images