JP7387312B2 - Optical system and imaging device including it - Google Patents

Description

The present invention relates to an optical system and an imaging device having the same, and is particularly suitable as an imaging optical system used in imaging devices such as digital still cameras, video cameras, surveillance cameras, and vehicle-mounted cameras.

In recent years, the number of pixels in image sensors such as CCD and CMOS sensors has increased, and the imaging optical system used in imaging devices using image sensors must have high optical performance and a wide imaging field of view (wide angle of view). ) is desired. In recent years, fisheye lenses and ultra-wide-angle lenses have been proposed as optical systems that can capture an area with an imaging half angle of view exceeding 80 degrees within an image circle of a specific size (Patent Documents 1 and 2).

JP2013-238684A Japanese Patent Application Publication No. 2002-72085

There is a strong demand for an imaging optical system used in an imaging device to have a wide angle of view and high optical performance while the entire lens system is small. Generally, in a wide-angle imaging optical system, a lens group with negative refractive power is arranged on the object side of the aperture stop, and a lens group with positive refractive power is arranged on the image side of the aperture stop. Since a wide-field-angle imaging optical system has a lens configuration asymmetrical with respect to the aperture stop, it is difficult to achieve a wide field-of-view while satisfactorily correcting chromatic aberrations such as chromatic aberration of magnification and achieving high optical performance.

Orthographic projection, equisolid angle projection, equidistant projection, and stereoscopic projection are known as projection methods for fisheye lenses. Among these, the equisolid angle projection method is used for visual environment evaluation because it has the property that the solid angle of a figure on a spherical surface is proportional to the area on the projection surface. On the other hand, unlike an ultra-wide-angle lens, a fisheye lens has a configuration that generates negative distortion, making it difficult to satisfactorily correct lateral chromatic aberration.

In order to effectively correct various aberrations such as lateral chromatic aberration while reducing the size and weight of the imaging optical system, the optical arrangement of each lens group, the refractive power of each lens group, and the dispersion characteristics of the material must be appropriately set. becomes important.

An object of the present invention is to provide an optical system having a wide angle of view, a compact overall system, and high optical performance, and an imaging device having the optical system.

The optical system of the present invention includes a first lens group with a negative refractive power, an aperture stop, and a second lens group with a positive refractive power, which are arranged in order from the object side to the image side. The system includes six or more lenses having refractive power, and the first lens group includes a negative lens G1N disposed closest to the object side of the first lens group, and a negative lens G1N adjacent to the negative lens G1N on the image side. The second lens group has at least one negative lens and at least one positive lens, and the focal length of the negative lens G1N is fG1N, and the second lens group has at least one negative lens and at least one positive lens. The focal length of the negative lens GLN having the largest negative refractive power is fGLN, the focal length of the optical system is f, the focal length of the first lens group is f1, the focal length of the negative lens G2N is fG2N, the second When the focal length of the lens group is f2, and the average value of the Abbe numbers of the materials of all the positive lenses included in the second lens group is νdP2,
0.70<fG1N/f1<1.0
2.00<|fGLN/f|<2.5
0.441≦fG1N/fG2N<0.80
-2.0<f1/f2<-1.0
75<νdP2<100
It is characterized by satisfying the following conditional expression.

According to the present invention, an optical system having a wide angle of view, a compact overall system, and high optical performance can be obtained.

Lens sectional view of the optical system of Example 1 Aberration diagram of the optical system of Example 1 when focused at infinity Lens sectional view of the optical system of Example 2 Aberration diagram of the optical system of Example 2 when focused at infinity Lens sectional view of the optical system of Example 3 Aberration diagram of the optical system of Example 3 when focused at infinity Schematic diagram of main parts of an imaging device of the present invention

Preferred embodiments of the present invention will be described below based on the accompanying drawings.

The optical system of the present invention includes a first lens group with negative refractive power, an aperture stop, and a second lens group with positive refractive power, which are arranged in order from the object side to the image side. During focusing, the entire lens system moves.

1, 3, and 5 are cross-sectional views of lenses of optical systems according to Examples 1 to 3 of the present invention. 2, 4, and 6 are aberration diagrams of the optical systems of Examples 1 to 3.

Example 1 is an optical system with an F number of 4.0 and an imaging half angle of view of 91 degrees. Example 2 is an optical system with an F number of 4.0 and an imaging half angle of view of 91 degrees. Example 3 is an optical system with an F number of 4.0 and an imaging half angle of view of 90 degrees.

The optical system of each embodiment is an imaging optical system used in an imaging device such as a digital still camera, a video camera, a surveillance camera, or a vehicle-mounted camera. In the cross-sectional view of the lens, the left side is the object side (front), and the right side is the image side (back). L0 is an optical system. L1 is a first lens group, and L2 is a second lens group.

SP is an aperture diaphragm that determines (restricts) the luminous flux of the open F number (Fno). IP is an image plane, and when used as a photographing optical system of a digital still camera or a video camera, the image pickup plane of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is placed.

In the aberration diagram, Fno is the F number, and ω is the imaging half angle of view (degrees), which is the angle of view determined by ray tracing. In the spherical aberration diagram, d is the d-line (wavelength 587.56 nm), and g is the g-line (wavelength 435.835 nm).

In the astigmatism diagram, ΔS is the sagittal image plane for the d-line, and ΔM is the meridional image plane for the d-line. Distortion aberration is shown for the d-line. In the lateral chromatic aberration diagram, g is the g-line.

The projection method in the optical system L0 of each embodiment of the present invention employs an equal solid angle projection method (Y=2·f·sin(θ/2)). Note that in the optical system L0 according to the present invention, the projection method is not limited to equisolid angle projection, and any projection method may be used.

The optical system L0 of the present invention includes a first lens group L1 with negative refractive power, an aperture stop SP, and a second lens group L2 with positive refractive power, which are arranged in order from the object side to the image side. The first lens group L1 and the second lens group each have a negative lens. Let fG1N be the focal length of the negative lens G1N closest to the object in the first lens group L1. Let fGLN be the focal length of the negative lens GLN having the largest negative refractive power in the second lens group. The focal length of the optical system L0 is f, and the focal length of the first lens group L1 is f1. At this time, the following conditional expression is satisfied.
0.10<fG1N/f1<1.00...(1)
0.10<|fGLN/f|<2.50...(2)

Here, the total lens length is a value obtained by adding the air-equivalent back focus to the distance from the first lens surface on the object side to the lens surface closest to the image side. Generally, as the overall length of the lens is shortened and the overall optical system is made more compact, various aberrations, especially chromatic aberrations such as chromatic aberration of magnification, occur more frequently, and optical performance deteriorates. In particular, in a retrofocus type optical system that aims to shorten the overall lens length, the first lens group L1 with negative refractive power tends to be large, so it is necessary to appropriate the lens configuration and refractive power arrangement of the first lens group L1. becomes important.

In each embodiment, the overall length of the lens and the back focus are shortened by optimizing the negative refractive power of the negative lens GLN in the second lens group L2.

Conditional expression (1) defines the focal length of the negative lens G1N that is closest to the object in the first lens group L1 by the focal length of the first lens group L1, and reduces the size and widens the angle of view of the optical system L0. The purpose is to achieve this goal. Exceeding the upper limit of conditional expression (1) is advantageous for correcting lateral chromatic aberration, but the effective diameter of the front lens becomes larger. When the lower limit of conditional expression (1) is exceeded, it becomes difficult to correct field curvature and distortion, the number of lenses increases, and the total lens length increases.

Conditional expression (2) defines the focal length of the negative lens GLN, which has the largest negative refractive power in the second lens group L2, as the focal length of the optical system L0, and reduces the back focus and the overall lens length. This is to shorten the time. When the upper limit of conditional expression (2) is exceeded, aberration correction becomes easy, but it becomes difficult to shorten the back focus, the total lens length increases, and the optical system becomes larger. Exceeding the lower limit of conditional expression (2) is not preferable because the change in image height due to off-axis comatic aberration becomes large, it becomes difficult to correct field curvature and astigmatism, and the number of lenses increases.

In each embodiment, as explained above, each element is appropriately set so as to satisfy conditional expressions (1) and (2). This provides a compact optical system in which various aberrations such as chromatic aberration are well corrected.

In each embodiment, it is more preferable to set the numerical ranges of conditional expressions (1) and (2) as follows.
0.50<fG1N/f1<0.92...(1a)
1.00<|fGLN/f|<2.40...(2a)

More preferably, the numerical ranges of conditional expressions (1a) and (2a) are set as follows.
0.70<fG1N/f1<0.88 (1b)
2.00<|fGLN/f|<2.30...(2b)

In each example, as described above, by optimizing the configuration of each lens group and satisfying conditional expressions (1) and (2), a large aperture ratio was achieved, the entire lens system was compact, and chromatic aberration was well corrected. An optical system with high imaging performance has been obtained.

Furthermore, the radius of curvature of the object-side lens surface of the negative lens GLN is R1GLN, and the radius of curvature of the image-side lens surface of the negative lens GLN is R2GLN. Here, the radius of curvature of the lens surface on the object side and the radius of curvature of the lens surface on the image side mean the base R (radius of the reference quadratic curved surface) when the lens surface is aspherical. Let ndGLN be the refractive index of the material of the negative lens GLN. Let the total length of the lens of the optical system be TD.

Let the back focus of the optical system be SK. The first lens group L1 is disposed adjacent to the image side of the negative lens G1N and has a negative lens G2N, and the focal length of the negative lens G2N is fG2N. Let f2 be the focal length of the second lens group L2. The second lens group L2 has one or more positive lenses, and the average Abbe number of the material of the positive lenses included in the second lens group L2 is νdP2. In addition, the Abbe number νd of the material is when the refractive index at the d line, F line, and C line of Fraunhofer lines is Nd, NF, and NC.
νd=(Nd-1)/(NF-NC)
Defined by Let ndN2 be the average value of the refractive index of the material of the negative lens included in the second lens group L2.

In an imaging device having an image sensor that receives an image formed by the optical system of each embodiment, the imaging half angle of view by ray tracing is assumed to be ω.

At this time, it is preferable that one or more of the following conditional expressions be satisfied.
1.0<(R2GLN+R1GLN)/
(R2GLN-R1GLN)<6.0...(3)
1.85<ndGLN<2.40 (4)
1.0<TD/f<10.0...(5)
0.5<SK/f<2.6...(6)
0.30<fG1N/fG2N<0.80...(7)
-2.0<f1/f2<-1.0...(8)
75<νdP2<100 (9)
1.86<ndN2<2.40 (10)
80°<ω<120°...(11)

Next, the technical meaning of each of the above conditional expressions will be explained.

Conditional expression (3) specifies the shape factor (lens shape) of the negative lens GLN, which has the largest negative refractive power in the second lens group L2, and mainly corrects the curvature of field while achieving back focus. This is to shorten the time period. If the upper limit of conditional expression (3) is exceeded, the meniscus shape of the negative lens GLN becomes strong, making it difficult to secure the desired refractive power, increasing the overall length of the lens, which is not preferable, and making it difficult to manufacture the negative lens GLN. It becomes difficult. If the lower limit of conditional expression (3) is exceeded, distortion tends to occur strongly in the positive direction, which is undesirable, and it becomes difficult to achieve both field curvature correction and magnification chromatic aberration correction.

Conditional expression (4) defines the refractive index of the material of the negative lens GLN, which has the largest negative refractive power in the second lens group L2. Due to the characteristics of optical materials, as the refractive index increases, the Abbe number decreases and lateral chromatic aberration becomes undercorrected. Therefore, in order to correct chromatic aberration, the refractive power must be weakened, which increases the overall length of the lens.

Furthermore, in a retrofocus optical system, when the number of constituent lenses is reduced to reduce the size, the Petzval sum tends to take a negative value, the image plane tilts toward the overside, and the astigmatism difference becomes large. Therefore, it is important to optimize the refractive index of the material of the negative lens to satisfactorily correct field curvature and astigmatism.

When the upper limit of conditional expression (4) is exceeded, it becomes easy to correct the image plane, but it becomes difficult to correct distortion aberration and lateral chromatic aberration. Exceeding the lower limit of conditional expression (4) is not preferable because it is necessary to weaken the refractive power of the material of the negative lens GLN in order to correct field curvature, and as a result, back focus increases.

Conditional expression (5) defines the lens total length TD by the focal length f of the optical system L0, and is mainly used to downsize the optical system while properly correcting off-axis aberrations. If the upper limit of conditional expression (5) is exceeded, the entire optical system becomes larger, and correction of off-axis aberrations, especially coma flare in the sagittal direction, increases, which is not preferable. When the lower limit of conditional expression (5) is exceeded, the total lens length becomes short, making it difficult to correct various aberrations such as coma and curvature of field.

Conditional expression (6) defines the back focus SK by the focal length f of the optical system L0, and defines a so-called retro ratio. If the back focus becomes longer than the upper limit of conditional expression (6), it becomes difficult to correct distortion aberration and curvature of field, and the number of lenses increases, which is not preferable. If the lower limit of conditional expression (6) is exceeded and the back focus becomes short, it becomes difficult to arrange a shutter member or the like on the image side.

Conditional expression (7) defines the sharing of the refractive power of the negative lens G1N and the refractive power of the negative lens G2N. Conditional expression (7) stipulates that two negative lenses are arranged in order from the object side to the image side, and their refractive power is shared, in order to make the optical system more compact and widen the angle of view. When the upper limit of conditional expression (7) is exceeded and the negative refractive power of the negative lens G1N closest to the object becomes weaker (as the absolute value of the negative refractive power becomes smaller), the effective diameter of the front lens increases. If the lower limit of conditional expression (7) is exceeded and the negative refractive power of the negative lens G1N closest to the object becomes stronger (the absolute value of the negative refractive power becomes larger), it will be advantageous for downsizing the optical system. , it becomes difficult to correct field curvature and astigmatism.

Conditional expression (8) defines the focal length f1 of the first lens group L1 with negative refractive power as the focal length f2 of the second lens group L2 with positive refractive power. When the negative refractive power of the first lens group L1 becomes strong beyond the upper limit of conditional expression (8), the divergence effect of the marginal ray becomes large, making it difficult to correct spherical aberration and coma aberration in the second lens group L2. When the lower limit of conditional expression (8) is exceeded and the positive refractive power of the second lens group L2 becomes stronger, the convergence effect of the second lens group L2 increases, making it possible to correct the secondary spectrum of lateral chromatic aberration and longitudinal chromatic aberration. It becomes difficult and I don't like it.

Conditional expression (9) defines the average value νdP2 of the Abbe number of the material of the positive lens included in the second lens group L2, and mainly aims to reduce the overall length of the lens while improving longitudinal chromatic aberration and lateral chromatic aberration. This is for correction. If the upper limit of conditional expression (9) is exceeded, it becomes easy to correct axial chromatic aberration and lateral chromatic aberration, but the radius of curvature of the lens surface of each lens increases, resulting in insufficient correction of spherical aberration and coma aberration, which is not preferable. When the lower limit of conditional expression (9) is exceeded, chromatic aberration increases, making it difficult to correct the aberration of the optical system as a whole.

Conditional expression (10) defines the average value ndN2 of the refractive index of the material of the negative lens included in the second lens group L2, and is mainly used to satisfactorily correct curvature of field and distortion aberration. be. When the upper limit of conditional expression (10) is exceeded, it becomes easy to downsize the optical system, but it becomes difficult to correct lateral chromatic aberration. If the lower limit of conditional expression (10) is exceeded, it becomes difficult to correct the curvature of field.

Conditional expression (11) defines the imaging half angle of view ω by ray tracing in an imaging device having an imaging element that receives an image formed by the optical system of each embodiment. If the maximum imaging half angle of view increases beyond the upper limit of conditional expression (11), image compression for each angle of view becomes high, making it difficult to obtain sufficient resolution. If the lower limit of conditional expression (11) is exceeded, it becomes difficult to obtain the angle of view necessary for a circumferential fisheye lens.

Preferably, the numerical ranges of conditional expressions (3) to (10) are set as follows.
1.3<(R2GLN+R1GLN)/(R2GLN-R1GLN)<3.0...(3a)
1.95<ndGLN<2.20...(4a)
3.0<TD/f<8.0...(5a)
1.2<SK/f<2.4...(6a)
0.35<fG1N/fG2N<0.70...(7a)
-1.6<f1/f2<-1.1...(8a)
80<νdP2<95...(9a)
1.90<ndN2<2.10...(10a)

More preferably, the numerical ranges of conditional expressions (3a) to (10a) are set as follows.
1.6<(R2GLN+R1GLN)/(R2GLN-R1GLN)<2.0...(3b)
2.00<ndGLN<2.10...(4b)
6.0<TD/f<7.0...(5b)
1.6<SK/f<2.2...(6b)
0.40<fG1N/fG2N<0.60...(7b)
-1.4<f1/f2<-1.2...(8b)
85<νdP2<92...(9b)
1.92<ndN2<1.98...(10b)

As described above, according to the present invention, it is possible to obtain an optical system in which the entire system is compact, corrects chromatic aberration well, and has high optical performance.

In addition, in the optical system of each example, it is preferable that the first lens group L1 has at least two negative lenses including the negative lens G1N. This facilitates widening the angle of view of the optical system.

In addition, in the optical system of each example, it is preferable that the lens surface closest to the image side has a convex shape toward the image side. This makes it possible to reduce ghosts caused by light reflected on the imaging surface.

Further, it is preferable that the optical system of each embodiment is composed of eight or fewer lenses. This makes it possible to configure the optical system to be compact and lightweight while obtaining the necessary optical performance.

Further, it is desirable that the optical system of each embodiment has an aperture stop between the first lens group L1 and the second lens group L2. The first lens group L1 is preferably composed of a negative lens, a negative lens, and a positive lens arranged in order from the object side to the image side. Further, the second lens group L2 is preferably composed of a positive lens, a negative lens, a positive lens, and a negative lens arranged in order from the object side to the image side. Further, the second lens group L2 is preferably composed of a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens arranged in order from the object side to the image side.

Although each embodiment describes a so-called single focus lens, the present invention is not limited thereto. The optical system of the present invention may be a zoom lens with a variable focal length. In that case, each conditional expression only needs to be satisfied at the wide-angle end of the zoom lens.

Next, a digital still camera (imaging device) using the optical system of the present invention will be described with reference to FIG. In FIG. 7, 10 is a camera body, and 11 is an imaging optical system configured by any of the optical systems described in Examples 1 to 3. Reference numeral 12 denotes an image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor, which is built into the camera body and receives a subject image formed by the image pickup optical system 11.

Specific numerical data of Examples 1 to 3 will be shown below. In each numerical data, i indicates the order counted from the object side, ri is the radius of curvature of the i-th optical surface (i-th surface), and di is on the axis between the i-th surface and the (i+1)-th surface. Indicates the interval. Further, ndi and vdi are the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. The aspherical shape has the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the direction of light travel as positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, and A8 are each the aspherical coefficients. when

It is expressed by the following formula. * means a surface having an aspherical shape. "ex" means 10 ^-x . BF is back focus in terms of air. Further, Table 1 shows the relationship between the parameters regarding each of the above-mentioned conditional expressions and the numerical data for each conditional expression.

[Numerical data 1]
Unit: mm

Surface data surface number rd nd νd θgF
1 48.855 2.20 1.76385 48.49 0.5589
2 11.031 8.00
3 13.330 1.50 1.53775 74.70 0.5392
4 8.150 7.29
5 -48.351 6.58 1.85025 30.05 0.5979
6 -26.933 4.00
7(Aperture) ∞ 4.00
8* -38.065 5.26 1.49710 81.56 0.5377
9* -9.535 1.12
10 12.869 1.50 1.85025 30.05 0.5979
11 9.695 9.98 1.43700 95.10 0.5326
12 -12.615 1.50 2.05090 26.94 0.6054
13 -38.769 11.72
14 ∞ 1.50 1.51633 64.14 0.5353
15 ∞ 0.50
Image plane ∞

Aspheric data 8th surface
K = 6.24411e+001 A 4=-1.54425e-004 A 6=-3.30729e-006

9th page
K = 9.25963e-001 A 4= 4.65880e-005 A 6=-1.63395e-008 A 8= 4.39179e-009

Various data

Focal length 8.10
F number 4.00
Half angle of view (degrees) 90.84
Image height 11.50
Lens total length 66.13
BF 13.21

Group data group Starting plane Focal length Lens length Front principal point position Rear principal point position
1 1 -21.96 25.56 -2.21 -32.37
2 7 17.16 23.36 5.35 -10.27

Single lens data lens starting surface focal length
1 1 -19.13
2 3 -43.40
3 5 62.67
4 8 24.12
5 10 -59.04
6 11 14.52
7 12 -18.33

[Numerical data 2]
Unit: mm

Surface data surface number rd nd νd θgF
1 49.348 2.20 1.77250 49.60 0.5520
2 11.602 8.36
3 16.043 1.50 1.59522 67.74 0.5442
4 8.639 8.43
5 -127.111 7.34 1.85025 30.05 0.5979
6 -32.443 4.00
7(Aperture) ∞ 4.00
8* -37.935 5.08 1.49710 81.56 0.5377
9* -9.832 1.12
10 12.990 1.50 1.85025 30.05 0.5979
11 10.208 7.08 1.43700 95.10 0.5326
12 -11.612 1.50 2.00100 29.13 0.5997
13 -37.657 14.46
14 ∞ 1.50 1.51633 64.14 0.5353
15 ∞ 0.50
Image plane ∞

Aspheric data 8th surface
K = 6.25847e+001 A 4=-1.19636e-004 A 6=-1.68125e-006

9th page
K = 1.14514e+000 A 4= 6.06644e-005 A 6=-4.08608e-008 A 8= 2.18193e-008

Various data

Focal length 8.05
F number 4.00
Half angle of view (degrees) 90.96
Image height 11.50
Lens total length 68.06
BF 15.95

Group data group Starting plane Focal length Lens length Front principal point position Rear principal point position
1 1 -25.02 27.82 -4.13 -40.41
2 7 18.32 20.28 5.83 -8.26

Single lens data lens starting surface focal length
1 1 -20.15
2 3 -34.02
3 5 49.47
4 8 25.19
5 10 -74.51
6 11 13.79
7 12 -17.27

[Numerical data 3]
Unit: mm

Surface data surface number rd nd νd θgF
1 47.043 2.20 1.75500 52.32 0.5474
2 10.972 8.05
3 16.238 1.50 1.59282 68.63 0.5446
4 8.975 8.46
5 -56.618 6.70 1.85025 30.05 0.5979
6 -25.741 4.00
7(Aperture) ∞ 4.00
8* -36.732 6.16 1.49710 81.56 0.5377
9* -10.650 1.12
10 16.329 1.40 1.85025 30.05 0.5979
11 14.422 6.07 1.43700 95.10 0.5326
12 -13.895 0.24
13 -12.740 1.10 2.00330 28.27 0.5980
14 -50.712 0.25
15 -625.576 2.25 1.43700 95.10 0.5326
16 -26.985 15.44
17 ∞ 1.50 1.51633 64.14 0.5353
18 ∞ 0.50
Image plane ∞

Aspheric data 8th surface
K = 5.26909e+001 A 4=-5.71261e-005 A 6= 4.12322e-007

9th page
K = 1.08114e+000 A 4= 5.10417e-005 A 6= 3.13406e-007 A 8= 8.03706e-009

Various data

Focal length 8.05
F number 4.00
Half angle of view (degrees) 90.07
Image height 11.40
Lens total length 70.43
BF 16.93

Group data group Starting plane Focal length Lens length Front principal point position Rear principal point position
1 1 -26.07 26.92 -5.08 -42.53
2 7 19.16 22.59 8.62 -8.15

Single lens data lens starting surface focal length
1 1 -19.46
2 3 -36.67
3 5 50.48
4 8 27.98
5 10 -219.23
6 11 17.32
7 13 -17.21
8 15 64.46

L1 1st lens group L2 2nd lens group SP Aperture diaphragm

Claims (13)

In an optical system that includes a first lens group with negative refractive power, an aperture stop, and a second lens group with positive refractive power, which are arranged in order from the object side to the image side,
The optical system has six or more lenses having refractive power,
The first lens group includes a negative lens G1N disposed closest to the object side of the first lens group, and a negative lens G2N disposed adjacent to the negative lens G1N on the image side,
The second lens group includes at least one negative lens and at least one positive lens ,
The focal length of the negative lens G1N is fG1N, the focal length of the negative lens GLN with the largest negative refractive power in the second lens group is fGLN, the focal length of the optical system is f, and the focal length of the first lens group is f1, the focal length of the negative lens G2N is fG2N, the focal length of the second lens group is f2, and the average value of the Abbe numbers of the materials of all the positive lenses included in the second lens group is νdP2,
0.70<fG1N/f1<1.0
2.00<|fGLN/f|<2.5
0.441≦fG1N/fG2N<0.80
-2.0<f1/f2<-1.0
75<νdP2<100
An optical system characterized by satisfying the following conditional expression. When the radius of curvature of the object-side lens surface of the negative lens GLN is R1GLN, and the radius of curvature of the image-side lens surface of the negative lens GLN is R2GLN,
1.0<(R2GLN+R1GLN)/(R2GLN-R1GLN)<6.0
The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. In an optical system composed of a first lens group with a negative refractive power, an aperture stop, and a second lens group with a positive refractive power, arranged in order from the object side to the image side,
The optical system has six or more lenses having refractive power,
The first lens group includes a negative lens G1N disposed closest to the object side of the first lens group, and a negative lens G2N disposed adjacent to the negative lens G1N on the image side,
The second lens group includes at least one negative lens,
The focal length of the negative lens G1N is fG1N, the focal length of the negative lens GLN having the largest negative refractive power in the second lens group is fGLN, the focal length of the optical system is f, and the focal length of the first lens group is f1, the focal length of the negative lens G2N is fG2N, the focal length of the second lens group is f2, the radius of curvature of the object side lens surface of the negative lens GLN is R1GLN, the image side lens surface of the negative lens GLN is When the radius of curvature is R2GLN,
0.70<fG1N/f1<1.0
2.00<|fGLN/f|<2.5
0.441≦fG1N/fG2N<0.80
-2.0<f1/f2<-1.0
1.0<(R2GLN+R1GLN)/(R2GLN-R1GLN)<6.0
An optical system characterized by satisfying the following conditional expression. When the refractive index of the material of the negative lens GLN is ndGLN,
1.85<ndGLN<2.40
4. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the total lens length of the optical system is TD,
1.0<TD/f<10.0
5. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the back focus of the optical system is SK,
0.5<SK/f<2.6
6. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the average value of the refractive index of the material of the negative lens included in the second lens group is ndN2,
1.86<ndN2<2.40
7. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. 8. The optical system according to claim 1, wherein the lens surface closest to the image side in the optical system has a convex shape toward the image side. 9. The optical system according to claim 1, wherein the total number of lenses constituting the optical system is eight or less. 10. The optical system according to claim 1, wherein the number of lenses constituting the second lens group is three or more. 11. The optical system according to claim 1, wherein the second lens group includes a plurality of negative lenses. An imaging device comprising: the optical system according to any one of claims 1 to 11; and an imaging element that receives an image formed by the optical system. It has the optical system according to any one of claims 1 to 12 and an image sensor that receives an image formed by the optical system, and when the imaging half angle of view by ray tracing is ω,
80°＜ω＜120°
An imaging device characterized by satisfying the following conditional expression.

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