Optical system and imaging device having the same

Abstract

To provide a compact, light-weight optical system for a wide-angle lens, which offers high optical performance.SOLUTION: An optical system comprises a front group having positive refractive power and a rear group having positive refractive power arranged in order from the object side to the image side, and is configured such that the distance between the front group and the rear group changes for focusing. Curvature radii of object-side and image-side surfaces of a lens with positive refractive power located on the most image side are set appropriately.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical system and an imaging device having the same. [Background technology]

[0002] As a photographic optical system with a wide photographic angle, a so-called retrofocus type photographic optical system is known in which an optical system having negative refractive power is arranged on the object side and an optical system having positive refractive power is arranged on the image side. This type of optical system is used, for example, in a single-focus wide-angle lens.

[0003] Furthermore, in digital cameras and video cameras, solid-state image pickup elements such as CCD and CMOS sensors are becoming increasingly high-resolution, and photographing lenses are being required to have high optical performance, including chromatic aberration, while also becoming smaller in size. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-009644 A [Patent Document 2] JP 2014-055992 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for wide-angle lens systems used in imaging devices that are small in overall size yet have high optical performance. In general, in wide-angle lenses, the overall lens length is reduced by placing a lens with negative refractive power closest to the image side. However, the exit pupil becomes shorter and the angle at which off-axis light rays enter the image sensor becomes larger, which causes shading and other problems due to the influence of the oblique incidence light characteristics of the image sensor. In addition, because off-axis light rays become higher in wide-angle lenses, the fluctuations in field curvature and distortion aberration during focusing become greater. To solve these problems, it is necessary to optimize the lens shape that constitutes the rear group and the focus group.

[0006] Patent Document 1 discloses a lens that, from the object side, is made up of a front group having positive refractive power and a rear group composed of one lens having positive refractive power, and the front group moves in the optical axis direction during focusing. The lens closest to the image side has a smaller radius of curvature on the object side than on the image side, and has a stronger positive refractive power than the entire system, which is undesirable because it causes deterioration of the field curvature caused mainly by off-axis rays.

[0007] Patent Document 2 discloses a lens that is composed of a front group having positive refractive power and a rear group consisting of one lens having negative refractive power, arranged in order from the object side, and that the front group moves in the optical axis direction during focusing. In a wide-angle lens, by placing a lens having negative refractive power closest to the image side, it is possible to reduce the overall lens length. However, this is not preferable because the angle at which off-axis light rays enter the image sensor becomes large due to the short exit pupil, and shading, etc. occurs due to the influence of the oblique incidence light characteristics of the image sensor.

[0008] The present invention provides an optical system that is small and lightweight and has high optical performance with reduced aberration fluctuation due to focusing, and an imaging apparatus having the same, in a wide-angle lens. [Means for solving the problem]

[0009] In order to achieve the above object, the optical system of the present invention comprises, arranged in order from the object side to the image side, a front group having positive refractive power: reargroup, the lens arranged closest to the object side in the front group has negative refractive power, and for focusing, the front group moves in the optical axis direction, while the rear group is stationary, In The lens positioned closest to the image The final lens has a positive refractive power. Let GLR1 be the radius of curvature of the object-side surface of the lens, GLR2 be the radius of curvature of the image-side surface, f2 be the focal length of the rear group, and f be the focal length of the entire system. 0.1<(GLR1+GLR2) / (GLR1-GLR2)<10.0 3.4 <f2 / f<6.2 The present invention is characterized in that the following conditional expression is satisfied: Effect of the Invention

[0010] According to the present invention, it is possible to provide an optical system that is small and lightweight and has high optical performance with reduced aberration fluctuation due to focusing, in a wide-angle lens, and an imaging device having the same. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a lens sectional view of the first embodiment when the object distance is at infinity. [Diagram 2] 4A to 4C are aberration diagrams of the first embodiment when the object distance is at infinity. [Diagram 3] FIG. 11 is a lens sectional view of Example 2 when the object distance is at infinity. [Figure 4] 11A to 11C are aberration diagrams of Example 2 when the object distance is at infinity. [Diagram 5] FIG. 11 is a lens sectional view of Example 3 when the object distance is at infinity. [Figure 6] 13A to 13C are aberration diagrams for Example 3 when the object distance is at infinity. [Figure 7] FIG. 11 is a lens sectional view of Example 4 when the object distance is at infinity. [Figure 8] 13A to 13C are aberration diagrams for Example 4 when the object distance is at infinity. [Figure 9] FIG. 13 is a lens sectional view of Example 5 when the object distance is at infinity. [Figure 10] 13A to 13C are aberration diagrams for Example 5 when the object distance is at infinity. [Figure 11]1 is a schematic diagram of a main part of an imaging device according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1, 3, 5, 7 and 9 are sectional views of the optical systems according to the first to fifth embodiments of the present invention when the object distance is at infinity. 2, 4, 6, 8 and 10 are aberration diagrams of the optical systems according to the first to fifth embodiments of the present invention when the object distance is at infinity.

[0013] The optical system of each embodiment is used in imaging devices such as digital still cameras, video cameras, security cameras, car-mounted cameras, etc. In the lens cross-sectional views, the left side is the object side (front) and the right side is the image side (rear).

[0014] SP is the aperture. IP is the image plane, where the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed when used as the shooting optical system of a digital still camera or video camera. Also, when used as the shooting optical system of a silver halide film camera, the photosensitive surface of the film is placed.

[0015] In the aberration diagram, Fno is the F-number and ω is the half angle of view (degrees). In the spherical aberration diagram, d is the d-line (wavelength 587.56 nm) and g is the g-line (wavelength 435.835 nm).

[0016] In the astigmatism diagram, ΔS is the sagittal image plane at the d-line, and ΔM is the meridional image plane at the d-line. Distortion is shown for the d-line. The chromatic aberration diagram shows lateral chromatic aberration for the g-line. The present invention has a front group having positive refractive power and a rear group having at least one lens having positive refractive power, which are arranged in that order from the object side to the image side, and the distance between the front group and the rear group changes during focusing. When the radius of curvature of the object side surface of the lens having positive refractive power closest to the image side is GLR1 and the radius of curvature of the image side surface is GLR2, 0.1<(GLR1+GLR2) / (GLR1-GLR2)<10.0 ···(1) The present invention is characterized in that the following condition is satisfied:

[0017] In a wide-angle lens, by appropriately setting the shape of the lens disposed closest to the image side, the exit pupil can be lengthened, and the angle at which off-axis light rays enter the image sensor is reduced. This makes it less susceptible to the effects of oblique incidence light characteristics of the image sensor, making it possible to reduce shading and the like. It also makes it possible to appropriately correct distortion aberrations and lateral chromatic aberrations that are mainly caused by off-axis light rays. In addition, by moving the front group in the optical axis direction during focusing, it is possible to suppress the fluctuation of various aberrations during focusing and to make the focus group lighter than when the entire system is integrated as a focus group.

[0018] Conditional formula (1) specifies the shape (shape factor) of the lens arranged closest to the image side. By optimizing the shape, it is possible to reduce shading and other aberrations by ensuring the exit pupil and to suppress fluctuations in various aberrations during focusing. If the upper limit of conditional formula (1) is exceeded, the positive refractive power of the lens arranged closest to the image side becomes strong, the exit pupil becomes long, and shading and other aberrations can be reduced. However, since the refractive power of the rear group becomes strong, it is advantageous to reduce the overall lens length, but this leads to deterioration of field curvature aberrations that are mainly generated by off-axis rays. If the lower limit of conditional formula (1) is exceeded, the positive refractive power of the lens arranged closest to the image side becomes weak and the exit pupil becomes short, which is undesirable.

[0019] It is preferable to set the numerical range of conditional expression (1) as follows: 0.2<(GLR1+GLR2) / (GLR1-GLR2)<7.0 ···(1a) It is more preferable to set the numerical range of condition (1a) as follows: 0.3<(GLR1+GLR2) / (GLR1-GLR2)<5.0 (1b) As described above, by satisfying conditional expression (1), it is possible to provide an optical system that is small, lightweight, and has high optical performance in a wide-angle lens, and an image pickup apparatus having the same.

[0020] In each embodiment, it is more preferable to satisfy one or more of the following conditions: Let sk be the distance from the image-side lens surface of the lens closest to the image side to the image surface (back focus in air), and LD be the distance on the optical axis from the object-side surface of the lens closest to the object side to the image-side surface of the lens closest to the image side. Let f11 be the focal length of the lens system located on the object side of the aperture in the front group, and f12 be the focal length of the lens system located on the image side of the aperture in the front group. Let LB be the distance on the optical axis between the front group and the rear group. Let f be the focal length of the entire system, f1 be the focal length of the front group, and f2 be the focal length of the rear group. Let ESinf be the focus sensitivity of the front group when focusing at infinity. When the lateral magnifications of the front and rear groups are β1 and β2, respectively, when focusing at infinity, focus sensitivity ESinf is ESinf = (1 - β1 2 )×β2 2 It is expressed as follows. When focusing at infinity, the distance on the optical axis from the object side surface of the lens closest to the object to the aperture is PD. The distance between the lens closest to the object and the second lens closest to the object is L12, and the distance between the second lens closest to the object and the third lens closest to the object is L23. The radius of curvature of the image side surface of the second lens closest to the object is G2R2, and the radius of curvature of the object side surface of the third lens closest to the object is G3R1. In the front group, the focal length of the lens closest to the object that has negative refractive power is fGn1. In the lens system arranged on the object side of the aperture in the front group, the average Abbe number of the lenses with negative refractive power is νdn, and the average Abbe number of the lenses with positive refractive power is νdp. 0.1 <sk / LD<0.5 ··(2) -5.0 <f11 / f12<5.0 ··(3) 0.05 <LB / LD<0.60 ··(4) 1.0 <f2 / f<7.0 ··(5) 0.2 <ESinf<2.0 ··(6) PD / LD<0.45 ··(7) -3.0 <f11 / f<12.0 ··(8) 0.1 <L12 / L23<5.0 ··(9) -8.0<(G2R2+G3R1) / (G2R2-G3R1)<-0.1··(10) 0.1 <fGn1 / f11<7.0 ··(11) 0.3<νdn / νdp<4.5 (12) The Abbe number νd is given by the following equation, where Nd, NF, and NC are the refractive indices at the d, F, and C lines of the Fraunhofer lines: νd=(Nd-1) / (NF-NC) is defined as:

[0021] Conditional formula (2) specifies the ratio of the back focal length sk to the distance on the optical axis from the object side surface of the lens closest to the object to the image side surface of the lens closest to the image, LD. If the upper limit of conditional formula (2) is exceeded, the back focal length sk increases and the lens cannot be positioned close to the image sensor, making it difficult to improve the curvature of field and chromatic aberration of magnification, resulting in poor image quality, which is undesirable. If the lower limit of conditional formula (2) is exceeded, the back focal length sk decreases and the lens can be positioned closer to the image sensor, which is advantageous for improving the curvature of field and chromatic aberration of magnification, but makes it difficult to position the shutter member, etc.

[0022] Conditional formula (3) specifies the ratio of the focal length f11 of the lens system (first sub-lens group) arranged closer to the object than the aperture in the front group to the focal length f12 of the lens system (second sub-lens group) arranged closer to the object than the aperture in the front group. If the upper limit of conditional formula (3) is exceeded, the refractive power of the lens system arranged closer to the object than the aperture in the front group becomes stronger, which is advantageous for making the lens system more compact, but is undesirable because distortion aberration and lateral chromatic aberration caused by off-axis light rays become worse. If the lower limit of conditional formula (3) is exceeded, the refractive power of the lens system arranged closer to the object than the aperture in the front group becomes weaker, which is advantageous for suppressing various aberrations, but is undesirable because the lens diameter becomes larger.

[0023] Conditional formula (4) prescribes the ratio of the axial distance LB between the front and rear groups to the axial distance LD from the object side surface of the lens closest to the object to the image side surface of the lens closest to the image. Exceeding the upper limit of conditional formula (4) is advantageous since the diameter of the lens closest to the image side of the front group becomes smaller, but is undesirable since the overall lens length becomes longer. Exceeding the lower limit of conditional formula (4) is advantageous since the overall lens length becomes smaller, but is undesirable since it becomes difficult to arrange the mechanical components required to change the distance between the front and rear groups.

[0024] Conditional formula (5) specifies the ratio of the focal length f2 of the rear group to the focal length f of the entire system. By optimizing the focal length of the rear group, it is possible to achieve both a reduction in the overall lens length and suppression of fluctuations in various aberrations during focusing. If the upper limit of conditional formula (5) is exceeded, the positive refractive power of the rear group becomes weak, which is advantageous for suppressing various aberrations, but leads to an increase in the overall lens length. If the lower limit of conditional formula (5) is exceeded, the positive refractive power of the rear group becomes strong, which leads to a reduction in the overall lens length, but is undesirable because it worsens field curvature and spherical aberration.

[0025] Conditional expression (6) specifies the focus sensitivity ESinf of the front group when focusing at infinity. Exceeding the upper limit of conditional expression (6) is undesirable because it increases the change in the angle of view relative to the amount of movement of the focus lens group during focusing. It is also undesirable because it becomes difficult to suppress the fluctuations in spherical aberration and curvature of field during focusing. Exceeding the lower limit of conditional expression (6) makes it easier to suppress the changes in spherical aberration and curvature of field during focusing, but it increases the amount of movement of the focus lens group during focusing, resulting in an increase in the overall lens length.

[0026] Conditional expression (7) specifies the position of the aperture in the entire system. By optimizing the position of the aperture, it is possible to reduce the diameter of the lens on the object side. Exceeding the upper limit of conditional expression (7) is not preferable because it becomes difficult to reduce the diameter of the lens on the object side.

[0027] Conditional expression (8) specifies the ratio of the focal length f1 of the front group to the focal length f of the entire system. Mainly, by optimizing the refractive power of the front group, it is possible to achieve both a compact lens system and good optical performance. If the upper limit of conditional expression (8) is exceeded, the refractive power of the front group becomes strong, which is advantageous for reducing the overall lens length, but this leads to deterioration of field curvature aberration. If the lower limit of conditional expression (8) is exceeded, the refractive power of the front group becomes weak, which is advantageous for suppressing the occurrence of various aberrations, but this is undesirable because it makes it difficult to reduce the overall lens length.

[0028] Conditional formula (9) specifies the ratio of the distance L12 between the lens closest to the object and the second lens closest to the object, and the distance L23 between the second lens closest to the object and the third lens closest to the object. If the upper limit of conditional formula (9) is exceeded, the distance L12 between the lens closest to the object and the second lens closest to the object becomes long, and the off-axis marginal rays passing through the lens closest to the object become high, which is undesirable because the lens diameter becomes large. If the lower limit of conditional formula (9) is exceeded, the distance L23 between the second lens closest to the object and the third lens closest to the object becomes long, and the on-axis marginal rays passing through the third lens closest to the object become high, which is advantageous for correcting spherical aberration, but is undesirable because the lens diameter becomes large.

[0029] Conditional formula (10) specifies the shape (shape factor) of the air lens between the image side surface of the second lens from the object side and the object side surface of the third lens from the object side. By optimizing the shape, it is possible to achieve good optical performance, mainly within the front group. If the upper limit of conditional formula (10) is exceeded, the refractive power of the air lens becomes weak, which is advantageous for suppressing the occurrence of various aberrations, but is undesirable. If the lower limit of conditional formula (10) is exceeded, the refractive power of the air lens becomes strong, which is advantageous for reducing the overall lens length, but off-axis rays are largely diverged, causing chromatic aberration to worsen.

[0030] Conditional expression (11) specifies the ratio of the focal length fGn1 of the lens closest to the object and having negative refractive power in the front group to the focal length f of the entire system. By optimizing the focal length of the lens closest to the object and having negative refractive power in the front group, it is possible to achieve both a small lens diameter and good optical performance. If the upper limit of conditional expression (11) is exceeded, the refractive power of the lens closest to the object and having negative refractive power in the front group becomes weak, which is advantageous for suppressing the occurrence of various aberrations, but it is undesirable because the lens diameter becomes large. If the lower limit of conditional expression (11) is exceeded, the refractive power of the lens closest to the object and having negative refractive power in the front group becomes strong, which is advantageous for reducing the lens diameter, but it is undesirable because chromatic aberrations become worse.

[0031] Conditional expression (12) specifies the ratio of the average Abbe number νdn of the lenses having negative refractive power in the front group to the average Abbe number νdp of the lenses having positive refractive power. By optimizing the Abbe number of the lenses in the front group, it is possible to achieve both a reduction in the lens diameter and suppression of lateral chromatic aberration occurring in the front group. If the upper limit of conditional expression (12) is exceeded, the correction effect of lateral chromatic aberration increases, but this leads to deterioration of axial chromatic aberration and makes it difficult to optimize the refractive power of the lenses having negative refractive power, resulting in an increase in the lens diameter. If the lower limit of conditional expression (12) is exceeded, the refractive power of the lens having negative refractive power can be optimized and the lens diameter can be reduced, but it becomes difficult to appropriately correct lateral chromatic aberration, which is not preferable. It is preferable to set the numerical ranges of the conditions (2) to (12) as follows: 0.15 <sk / LD<0.40 ··(2a) -3.0 <f11 / f12<4.5 ··(3a) 0.08 <LB / LD<0.30 ··(4a) 2.2 <f2 / f<6.2 ··(5a) 0.4 <ESinf<1.0 ··(6a) PD / LD<0.4 (7a) -2.6 <f11 / f<10.0 ··(8a) 0.3 <L12 / L23<4.0 ··(9a) -4.0<(G2R2+G3R1) / (G2R2-G3R1)<-0.3·(10a) 0.3 <fGn1 / f1<4.0 ··(11a) 0.8<νdn / νdp<3.2 (12a) It is more preferable to set the numerical ranges of the conditions (2a) to (12a) as follows: 0.2 <sk / LD<0.36 ··(2b) -1.5 <f11 / f12<4.0 ··(3b) 0.10 <LB / LD<0.20 ··(4b) 3.4 <f2 / f<5.5 ··(5b) 0.5 <ESinf<0.82 ··(6b) PD / LD<0.35 (7b) -2.2 <f11 / f<9.0 ··(8b) 0.9 <L12 / L23<3.0 ··(9b) -2.7<(G2R2+G3R1) / (G2R2-G3R1)<-1.1·(10b) 0.5 <fGn1 / f1<2.1 ··(11b) 1.1<νdn / νdp<2.6 (12b)

[0032] When the focus group moves from infinity focusing to the closest focusing, it is desirable for the rear group to be fixed. Furthermore, it is desirable to have only one focus group. This makes it possible to reduce the number of parts, such as motors, required to move the focus group, thereby making the lens lighter.

[0033] It is desirable that the lens system located on the object side of the aperture stop in the front group contain only one lens element with positive refractive power, which makes it possible to both correct lateral chromatic aberration that occurs in the front group and reduce the overall lens length.

[0034] It is desirable that at least one lens element with positive refractive power in the lens system located on the object side of the front group relative to the aperture stop has a convex surface facing the image side, which makes it possible to both correct spherical aberration and reduce the overall length of the lens.

[0035] The front group desirably has at least one cemented lens made of a lens having positive refractive power and a lens having negative refractive power, and preferably has two cemented lenses made of a lens having positive refractive power and a lens having negative refractive power, which makes it possible to correct axial chromatic aberration and chromatic aberration of magnification.

[0036] It is desirable for the front group to have at least one aspherical lens, which makes it possible to appropriately correct fluctuations in field curvature caused by focusing, which are mainly caused by off-axis rays.

[0037] It is preferable that the rear group be made up of one lens element having positive refractive power, which makes it possible to secure an exit pupil while also reducing the weight of the lens.

[0038] When image blur correction is performed by moving the image blur correction group in a direction perpendicular to the optical axis, some of the lenses in the entire system may have a movement mechanism (anti-vibration mechanism). EXAMPLES

[0039] Numerical examples 1 to 5 will be referred to as the present embodiment hereinafter. In each numerical example, ri is the radius of curvature of the ith surface, starting from the object side, di is the lens thickness and air space between the ith surface and the (i+1)th surface, starting from the object side, and ndi and νdi are the refractive index and Abbe number of the optical medium between the ith surface and the (i+1)th surface, starting from the object side, respectively.

[0040] The aspheric shape is defined as follows: X-axis is in the direction of the optical axis, H-axis is perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, A10, A12, and A14 are the aspheric coefficients.

number

[0041] The * to the right of the surface number means that the surface has an aspheric shape. -x " BF stands for back focus. Next, an embodiment of a digital still camera using the optical system of the present invention as a photographing optical system will be described with reference to FIG. 11, reference numeral 10 denotes a camera body, and 11 denotes a photographing optical system constituted by any one of the zoom lenses described in Examples 1 to 5. Reference numeral 12 denotes a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body and receives a subject image formed by the photographing optical system 11.

[0042] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd vd 1 41.307 1.20 1.60311 60.6 2 9.978 4.26 3 30.342 1.00 1.48749 70.2 4 12.124 3.17 5 28.492 2.01 1.83481 42.7 6 -662.034 5.01 7(Aperture) ∞ 1.80 8 47.613 5.77 1.81600 46.6 9 -8.980 0.91 1.90366 31.3 10 -16.902 5.69 11 -18.534 0.92 1.69895 30.1 12 29.517 4.40 1.59282 68.6 13 -35.692 1.10 14* -54.759 2.10 1.53110 55.9 15* -34.782 6.57 16 -161.374 4.59 1.60311 60.6 17 -34.257 12.94 Image plane ∞ Aspheric Data Side 14 K = 0.00000e+000 A 4= 4.57136e-005 A 6=-1.97209e-006 A 8= 3.74538e-008 A10=-4.12263e-010 A12= 1.59769e-012 Page 15 K = 0.00000e+000 A 4= 1.03365e-004 A 6=-1.10800e-006 A 8= 1.95771e-008 A10=-1.88559e-010 A12= 6.52817e-013 Various data Focal length 18.20 F-number 2.90 Half angle of view 45.00 Image height 18.20 Lens length 63.45 BF 12.94 Lens Group Data Group starting plane focal length 1 1 21.96 2 16 71.14

[0043] [Numerical Example 2] Unit: mm Surface Data Surface number rd nd vd 1 25.173 1.20 1.59522 67.7 2 9.960 4.83 3 22.509 1.00 1.49700 81.5 4 7.529 1.81 5 57.731 1.65 1.91650 31.6 6 -98.374 3.25 7(Aperture) ∞ 1.80 8 64.342 6.53 1.88300 40.8 9 -7.326 0.91 2.00069 25.5 10 -12.387 3.52 11 -19.745 0.92 1.69895 30.1 12 23.747 5.10 1.49700 81.5 13 -27.013 1.44 14* -29.866 2.10 1.53110 55.9 15* -17.802 6.34 16 -62.773 4.14 1.64000 60.1 17 -26.587 10.97 Image plane ∞ Aspheric Data Side 14 K = 0.00000e+000 A 4=-2.73841e-005 A 6=-3.88135e-007 A 8= 2.67267e-008 A10=-4.37155e-010 A12= 2.30061e-012 A14=-5.75662e-015 Page 15 K = 0.00000e+000 A 4= 7.95764e-005 A 6=-3.58079e-007 A 8= 2.89945e-008 A10=-3.41257e-010 A12= 1.23584e-012 A14=-2.30241e-016 Focal length 14.28 F-number: 2.91 Half angle of view: 51.88 Image height 18.20 Lens length 57.50 BF 10.97 Lens Group Data Group starting plane focal length 1 1 16.48 2 16 68.99

[0044] [Numerical Example 3] Unit: mm Surface Data Surface number rd nd vd 1 27.125 1.10 1.60311 60.6 2 9.735 3.67 3 30.493 1.00 1.48749 70.2 4 10.586 3.21 5 40.191 1.71 1.83400 37.2 6 -392.360 5.43 7(Aperture) ∞ 1.80 8 38.857 6.25 1.83481 42.7 9 -8.128 0.90 1.90366 31.3 10 -16.045 4.69 11 -16.526 0.92 1.68893 31.1 12 19.781 5.80 1.59282 68.6 13 -26.412 0.91 14* -50.009 2.10 1.53110 55.9 15* -32.615 6.74 16 -109.118 4.42 1.62299 58.2 17 -31.658 12.54 Image plane ∞ Aspheric Data Side 14 K = 0.00000e+000 A 4= 5.22756e-005 A 6=-1.92650e-006 A 8= 3.51677e-008 A10=-3.71946e-010 A12= 1.36387e-012 Page 15 K = 0.00000e+000 A 4= 1.10438e-004 A 6=-1.14287e-006 A 8= 2.01498e-008 A10=-1.88642e-010 A12= 6.28660e-013 Focal length 16.48 F-number 2.90 Half angle of view: 47.84 Image height 18.20 Lens length 63.19 BF 12.54 Lens Group Data Group starting plane focal length 1 1 19.70 2 16 70.05

[0045] [Numerical Example 4] Unit: mm Surface Data Surface number rd nd vd 1 23.402 1.20 1.65160 58.5 2 9.036 4.12 3 42.789 0.90 1.49700 81.5 4 13.075 1.50 5 53.278 1.58 1.91082 35.3 6 -3366.466 6.15 7(Aperture) ∞ 1.66 8 30.996 6.92 1.83481 42.7 9 -8.459 0.87 1.90366 31.3 10 -16.835 4.39 11 -17.793 0.93 1.68893 31.1 12 17.113 7.09 1.61800 63.4 13 -24.767 0.50 14* -88.687 2.10 1.53110 55.9 15* -49.891 6.99 16 -37.109 3.65 1.60311 60.6 17 -22.451 13.47 Image plane ∞ Aspheric Data Side 14 K = 0.00000e+000 A 4= 3.20994e-005 A 6=-1.17847e-006 A 8= 5.68853e-009 A10=-3.19562e-011 A12= 1.12210e-014 Page 15 K = 0.00000e+000 A 4= 1.04857e-004 A 6=-6.86726e-007 A 8= 1.82918e-009 Focal length 16.48 F-number: 2.91 Half angle of view: 48.31 Image height 18.50 Lens length 64.04 BF 13.47 Lens Group Data Group starting plane focal length 1 1 18.71 2 16 86.17

[0046] [Numerical Example 5] Unit: mm Surface Data Surface number rd nd vd 1 370.091 1.20 1.65160 58.5 2 10.962 11.82 3 23.532 2.35 1.81600 46.6 4 -261.263 1.97 5(Aperture) ∞ 1.80 6 55.000 6.46 1.81600 46.6 7 -9.617 0.91 1.90366 31.3 8 -22.024 4.64 9 -15.178 0.92 1.69895 30.1 10 37.405 3.54 1.59282 68.6 11 -45.470 2.59 12* -18.407 2.10 1.53110 55.9 13* -15.903 6.80 14 111.462 5.73 1.51633 64.1 15 -53.364 11.16 Image plane ∞ Aspheric Data Side 12 K = 0.00000e+000 A 4=-4.23116e-005 A 6=-3.29069e-007 A 8= 3.49757e-008 A10=-2.97301e-010 A12= 7.14062e-013 A14=-9.39720e-016 Page 13 K = 0.00000e+000 A 4= 5.00081e-005 A 6=-5.09273e-007 A 8= 3.35843e-008 A10=-2.22271e-010 A12= 2.03270e-013 A14= 1.10164e-015 Focal length 20.10 F-number 2.90 Half angle of view: 42.16 Image height 18.20 Lens length 63.99 BF 11.16 Lens Group Data Group starting plane focal length 1 1 24.37 2 14 70.73

[0047] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Table 1]

Claims

1. It consists of a front group and a rear group, both of which have positive refractive power, arranged in order from the object side to the image side. the lens disposed closest to the object side in the front group has negative refractive power, For focusing, the front group moves in the optical axis direction and the rear group is stationary; The final lens in the rear group that is disposed furthest to the image side has positive refractive power, the radius of curvature of the object side surface of the final lens is GLR1, the radius of curvature of the image side surface is GLR2, the focal length of the rear group is f2, and the focal length of the entire system is f, 0.1<(GLR1+GLR2) / (GLR1-GLR2)<10.0 3.4<f2 / f<6.2 An optical system characterized in that the following condition is satisfied:

2. When the distance from the image side lens surface of the final lens to the image surface (back focus in air) is sk, and the distance on the optical axis from the object side surface of the lens closest to the object to the image side surface of the final lens when focusing at infinity is LD, 0.1<sk / LD<0.5 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. a diaphragm is provided within the front group, When the focal length of the first sub-lens group arranged on the object side of the aperture stop in the front group is f11, and the focal length of the second sub-lens group arranged on the image side of the aperture stop in the front group is f12, -5.0<f11 / f12<5.0 3. The optical system according to claim 1, wherein the following condition is satisfied:

4. When the distance on the optical axis between the front group and the rear group when focusing on infinity is LB, and the distance on the optical axis from the object side surface of the lens closest to the object to the image side surface of the last lens when focusing on infinity is LD, 0.05<LB / LD<0.60 4. The optical system according to claim 1, wherein the following condition is satisfied:

5. When the focus sensitivity of the front lens group when focusing on infinity is ESinf, 0.2<ESinf<2.0 5. The optical system according to claim 1, wherein the following condition is satisfied:

6. a diaphragm is provided within the front group, When focusing at infinity, the distance on the optical axis from the object side surface of the lens closest to the object to the stop is PD, and the distance on the optical axis from the object side surface of the lens closest to the object to the image side surface of the last lens is LD. PD / LD<0.45 6. The optical system according to claim 1, wherein the following condition is satisfied:

7. a diaphragm is provided within the front group, When the focal length of the first sub-lens group arranged on the object side of the aperture stop in the front group is f11, -3.0<f11 / f<12.0 7. The optical system according to claim 1, wherein the following condition is satisfied:

8. a diaphragm is provided within the front group, 8. The optical system according to claim 1, wherein a first sub-lens group arranged on the object side of the stop in the front group includes three lenses.

9. The optical system according to claim 8 , wherein the first sub-lens group includes a lens having a positive refractive power.

10. When the distance between the lens closest to the object and the second lens closest to the object is L12, and the distance between the second lens closest to the object and the third lens closest to the object is L23, 0.1<L12 / L23<5.0 10. The optical system according to claim 1, wherein the following condition is satisfied:

11. When the radius of curvature of the image side surface of the second lens from the object side is G2R2, and the radius of curvature of the object side surface of the third lens from the object side is G3R1, -8.0<(G2R2+G3R1) / (G2R2-G3R1)<-0.1 11. The optical system according to claim 1, wherein the following condition is satisfied:

12. When the focal length of the lens having negative refractive power closest to the object side in the front group is fGn1, and the focal length of the first sub-lens group arranged on the object side of the aperture stop in the front group is f11, 0.1<fGn1 / f11<7.0 10. The optical system according to claim 3, wherein the following condition is satisfied:

13. When the average Abbe number of the material of the lenses having negative refractive power in the front group is νdn and the average Abbe number of the material of the lenses having positive refractive power in the front group is νdp, 0.3<νdn / νdp<4.5 13. The optical system according to claim 1, wherein the following condition is satisfied:

14. 14. The optical system according to claim 1, wherein the lens arranged closest to the object side in the front group is a negative meniscus lens having a convex surface facing the object side.

15. 15. An imaging apparatus comprising: the optical system according to claim 1; and an imaging element that receives an image formed by the optical system.

Images