JP2023037909A - Optical system and imaging apparatus - Google Patents

Abstract

To provide a compact optical system having a wide angle of view and high optical performance.SOLUTION: An optical system is comprised of a first lens group B1 having negative or positive refractive power, an aperture stop SP, and a second lens group B2 having positive refractive power which are arranged in order from the object side to the image side, and has a half view angle of 80° or more. The first lens group has a plurality of negative lenses, including a first negative lens and a second negative lens, and at least one positive lens arranged in order from the object side to the image side. The second lens group has at least one negative lens and a plurality of positive lenses. The optical system satisfies conditions expressed as: 2.00≤td/f≤6.50 and 0.80≤|fn/fp|≤2.00, where td represents an optical axial distance from the most object-side lens surface to the most image-side lens surface, f represents a focal length of the optical system, fn represents an average focal length of the a plurality of negative lenses of the first lens group, and fp represents an average focal length of the at least one positive lens of the first lens group.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical system suitable for imaging devices such as digital still cameras, video cameras, surveillance cameras, and vehicle-mounted cameras.

The optical system as described above includes a fish-eye lens and a super-wide-angle lens having a half angle of view of 80° or more, as disclosed in Patent Documents 1 and 2. In addition, there is an imaging apparatus that performs image processing such as cutting out a part of an image obtained by imaging or synthesizing a plurality of images to generate a bird's-eye view image or a stereoscopic image.

JP-A-2002-72085 JP 2010-243711 A

Fish-eye lenses and ultra-wide-angle lenses used in such image pickup apparatuses are required to have high optical performance and miniaturization.

The present invention provides a compact optical system having a wide angle of view and high optical performance, and an imaging apparatus using the same.

An optical system as one aspect of the present invention comprises a first lens group with negative or positive refractive power, an aperture stop, and a second lens group with positive refractive power, arranged in order from the object side to the image side. , an optical system with a half angle of view of 80° or more. The first lens group has a plurality of negative lenses including a first negative lens and a second negative lens arranged in order from the object side to the image side, and at least one positive lens. The second lens group has at least one negative lens and a plurality of positive lenses. td is the distance on the optical axis from the most object-side lens surface to the most image-side lens surface, f is the focal length of the optical system, and the average value of the focal lengths of the plurality of negative lenses in the first lens group is fn, where fp is the average value of the focal lengths of the at least one positive lens in the first lens group,
2.00≤td/f≤6.50
0.80≦|fn/fp|≦2.00
satisfy the following conditions. An imaging device that images an object through the optical system also constitutes another aspect of the present invention.

According to the present invention, it is possible to provide a compact optical system having a wide angle of view and excellent optical performance by correcting aberrations well.

FIG. 2 is a cross-sectional view of the optical system of Example 1; FIG. 4 is a longitudinal aberration diagram of the optical system of Example 1; FIG. 5 is a cross-sectional view of the optical system of Example 2; FIG. 8 is a longitudinal aberration diagram of the optical system of Example 2; FIG. 10 is a cross-sectional view of the optical system of Example 3; FIG. 10 is a longitudinal aberration diagram of the optical system of Example 3; FIG. 2 is a diagram showing an image pickup apparatus provided with optical systems of Examples 1 to 3;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, prior to describing the optical systems of specific examples (1 to 3), the items common to the optical systems of each example will be described.

The optical system of each embodiment (hereinafter referred to as a wide-angle lens) is used as an imaging lens in various imaging devices such as digital still cameras, video cameras, surveillance cameras, and vehicle-mounted cameras.

1, 3 and 5 show cross sections of the wide-angle lenses of Examples 1-3. The wide-angle lens of each embodiment is a single focus lens (an optical system whose focal length does not change).

In each figure, the left side is the object side and the right side is the image side. If i is a number indicating the order of lens groups from the object side, Bi indicates the i-th lens group. SP is an aperture stop that determines (limits) the luminous flux of the open f-number. IP is the image plane. The imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, or the film plane (sightseeing plane) of a silver halide film camera is arranged on the image plane. GB is a glass block having no refractive power such as an optical filter.

The optical system (hereinafter referred to as a wide-angle lens) of each embodiment includes a first lens group (B1) with negative or positive refractive power, an aperture stop (SP) and a positive refractive power, which are arranged in order from the object side to the image side. The second lens group (B2) has a half field angle of 80° or more and 110° or less. The half angle of view is obtained by ray tracing. Further, in the wide-angle lens of each embodiment, the entire wide-angle lens moves in the optical axis direction during focusing.

The first lens group has a plurality of negative lenses including a first negative lens closest to the object and a second negative lens second from the object, and at least one positive lens. The second lens group has at least one negative lens and multiple positive lenses. The arrangement order of the negative lens and the positive lens in the second lens group does not matter. By constructing the first and second lens groups in this way, it becomes possible to appropriately correct the chromatic aberration of magnification, which tends to become particularly large in a wide-angle lens.

Furthermore, td is the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image, f is the focal length of the entire wide-angle lens system, and the average value of the focal lengths of the plurality of negative lenses in the first lens group. is fn, and the average focal length of at least one positive lens in the first lens group is fp. At this time, the wide-angle lens of each example satisfies the conditions of the following equations (1) and (2).

2.00≤td/f≤6.50 (1)
0.80≦|fn/fp|≦2.00 (2)
Equation (1) indicates a condition regarding a preferable relationship between the thickness of the entire wide-angle lens system in the optical axis direction and the focal length of the entire system. If the thickness of the entire system becomes too large such that td/f exceeds the upper limit of the formula (1), aberrations can be easily suppressed, but the size of the entire system increases, which is not preferable. On the other hand, if the thickness of the entire system becomes too small such that td/f falls below the lower limit of formula (1), this is good for miniaturization of the entire system, but it is not preferable because correction of curvature of field becomes difficult.

Equation (2) indicates a condition regarding a preferable relationship between the average value of the focal lengths of the plurality of negative lenses and the average value of the focal lengths of at least one positive lens in the first lens group. If the average value of the focal lengths of the plurality of negative lenses in the first lens group becomes too small such that |fn/fp| increases, which is undesirable. On the other hand, if the average value of the focal lengths of the plurality of negative lenses in the first lens group becomes too small so that |fn/fp| This is not preferable because it increases the size of the lens group.

By satisfying at least the conditions of formulas (1) and (2), the wide-angle lens of each embodiment has a wide angle of view and a small size, and also has high optical performance by satisfactorily correcting aberrations.

The wide-angle lens of each embodiment preferably satisfies at least one of the following conditions (3) to (13).

First, the distance on the optical axis from the lens surface closest to the object side of the wide-angle lens to the image surface (paraxial image surface) (lens total length) is L, and the optical axis from the lens surface closest to the image side of the wide-angle lens to the image surface When the back focus, which is the air-converted distance above, is sk, it is preferable to satisfy the condition of the following formula (3).

1.41≦L/sk≦7.08 (3)
Expression (3) is a condition regarding a preferable relationship between the total lens length of the wide-angle lens and the back focus. If the total length of the lens is too large such that L/sk exceeds the upper limit of the formula (3), it is easy to suppress the aberration, but this is not preferable because it leads to an increase in the size of the entire system. If the overall lens length is too short such that L/sk is below the lower limit of formula (3), it is easy to downsize the entire system, but it is not preferable because correction of curvature of field becomes difficult.

Moreover, it is preferable to satisfy the following formula (4).

0.25≦f/sk≦0.93 (4)
Equation (4) indicates a condition regarding a preferable relationship between the focal length of the entire wide-angle lens system and the back focus. Glass, an optical filter, a shutter unit, and the like are arranged between the lens surface closest to the image side of the wide-angle lens and the image plane to protect the imaging element arranged on the image plane. Therefore, f/sk is preferably within the range of formula (4).

Further, when the focal length of the first negative lens disposed closest to the object in the first lens group (wide-angle lens) is fg1, and the focal length of the entire wide-angle lens system is f, the following equation (5) is satisfied. Satisfied is preferred.

0.73≦|fg1/f|≦3.60 (5)
Equation (5) indicates a condition regarding a preferable relationship between the focal length of the first negative lens and the focal length of the entire system. If the focal length of the first negative lens is too small such that |fg1/f| exceeds the upper limit of expression (5), aberrations can be easily suppressed, but this is not preferable because it results in an increase in the size of the entire system. If the focal length of the first negative lens becomes too large such that |fg1/f| falls below the lower limit of equation (5), it is easy to downsize the entire system, but mainly it becomes difficult to correct curvature of field. Therefore, it is not preferable.

Moreover, it is preferable to satisfy the condition of the following formula (6).

0.36≦|fg1/sk|≦2.09 (6)
Equation (6) indicates a condition regarding a preferable relationship between the focal length of the first negative lens and the back focus. If the focal length of the first negative lens is too small such that |fg1/sk| exceeds the upper limit of expression (6), aberrations can easily be suppressed, but the size of the entire system increases, which is not preferable. If the focal length of the first lens is too large such that |fg1/sk| , unfavorable.

Further, when the focal length of the second negative lens arranged second from the object side in the first lens group is fg2, it is preferable to satisfy the condition of the following formula (7).

0.43≦fg1/fg2≦1.54 (7)
Equation (7) indicates a condition regarding a preferable relationship between the focal length of the first negative lens and the focal length of the second negative lens. If the focal length of the first negative lens becomes too small such that fg1/fg2 exceeds the upper limit of the formula (7), the curvature of the image-side lens surface of the first negative lens becomes too small, making it difficult to process. Therefore, it is not preferable. If the focal length of the first negative lens becomes too large so that fg1/fg2 falls below the lower limit of equation (7), the curvature of the image-side lens surface of the first negative lens will be easy to process, but the overall system will be small. because it is difficult to convert I don't like it.

Further, when the focal length of the positive lens arranged third from the object side in the first lens group (hereinafter referred to as the third positive lens) is fg3, it is preferable to satisfy the following condition (8). .

0.47≦|fg2/fg3|≦2.02 (8)
Equation (8) shows the conditions for the preferred relationship between the focal length of the second negative lens and the focal length of the third positive lens. If the focal length of the third positive lens becomes too small to exceed the upper limit of equation (8), the curvature of the image-side lens surface of the second negative lens becomes too small. It is not preferable because the processing becomes difficult. On the other hand, if the focal length of the third positive lens becomes too large such that fg1/fg2 falls below the lower limit of equation (8), the image-side lens surface of the second negative lens has a curvature that is easy to process, but the overall system It is not preferable because it becomes difficult to reduce the size of the device.

Further, when the focal length of the second lens group having positive refractive power is fb2, it is preferable to satisfy the condition of the following formula (9).

0.91≦fb2/f≦3.95 (9)
Equation (9) indicates a condition regarding a preferable relationship between the focal length of the second lens group and the focal length of the entire system. If the focal length of the second lens group becomes too large such that fb2/f exceeds the upper limit of formula (9), it is preferable for correction of various aberrations, but it is not preferable because it becomes difficult to reduce the size of the entire system. If the focal length of the second lens group becomes too small so that fb2/f is less than the lower limit of formula (9), it is good for miniaturization of the entire system, but it is not preferable because correction of coma aberration becomes difficult.

Moreover, it is preferable to satisfy the condition of the following formula (10).

0.45≦fb2/sk≦2.29 (10)
Equation (10) indicates a condition regarding a preferable relationship between the focal length of the second lens group and the back focus. If the focal length of the second lens group becomes too large such that fb2/sk exceeds the upper limit of formula (10), it is preferable for correction of various aberrations, but it is not preferable because it becomes difficult to reduce the size of the entire system. On the other hand, if the focal length of the second lens group is too small so that fb2/sk is below the lower limit of formula (10), it is good for miniaturization of the entire system, but it becomes difficult to correct coma, which is preferable. do not have.

When the positive lens located closest to the image side in the second lens group is fgf, the focal length of the positive lens preferably satisfies the following equation (11).

1.35≤fgf/sk≤9.44 (11)
Equation (11) indicates a condition regarding a preferable relationship between the focal length of the positive lens closest to the image side in the second lens group and the back focus. If the focal length of the lens closest to the image side in the second lens group becomes too large so that fgf/sk exceeds the upper limit of formula (11), it is good for correction of various aberrations, but it is difficult to reduce the size of the entire system. It is not preferable because If the focal length of the lens closest to the image side in the second lens group becomes too large so that fgf/sk falls below the lower limit of equation (11), it is good for miniaturization of the entire system, but it is difficult to correct curvature of field. Therefore, it is not preferable.

Moreover, it is preferable to satisfy the condition of the following formula (12).

0.40≦fgf/L≦2.00 (12)
Equation (12) indicates a condition regarding a preferable relationship between the focal length of the positive lens closest to the image side in the second lens group and the overall lens length. If the focal length of the lens closest to the image side in the second lens group becomes too large so that fgf/L exceeds the upper limit of formula (12), it is good for correction of various aberrations, but it is difficult to reduce the size of the entire system. It is not preferable because If the focal length of the lens closest to the image side in the second lens group becomes too small so that fgf/L falls below the lower limit of equation (12), it is good for miniaturization of the entire system, but it is difficult to correct curvature of field. Therefore, it is not preferable.

Further, the second lens group includes a cemented lens in which a positive lens and a negative lens are cemented for correction of longitudinal chromatic aberration, and when the focal lengths of the positive lens and the negative lens in the cemented lens are fgp and fgn, respectively, It is preferable to satisfy the condition of the following formula (13).

0.32≦|fgp/fgn|≦1.23 (13)
Expression (13) indicates a condition regarding a preferable relationship between the focal length fgp of the positive lens and the focal length fgn of the negative lens of the cemented lens included in the second lens group. If the focal length of the positive lens of the cemented lens becomes too large so that |fgp/fgn| exceeds the upper limit of the formula (13), it is good for correction of axial chromatic aberration, but it becomes difficult to reduce the size of the entire system. , unfavorable. If the focal length of the positive lens of the cemented lens becomes too small so that |fgp/fgn| , unfavorable.

It is more preferable to set the numerical ranges of formulas (1) to (13) as follows.

2.70≤td/f≤6.45 (1a)
0.85≦|fn/fp|≦1.50 (2a)
1.97≦L/sk≦6.14 (3a)
0.35≦f/sk≦0.80 (4a)
1.03≦|fg1/f|≦3.12 (5a)
0.51≦|fg1/sk|≦1.81 (6a)
0.60≦fg1/fg2≦1.34 (7a)
0.66≦|fg2/fg3|≦1.75 (8a)
1.27≦fb2/f≦3.42 (9a)
0.63≦fb2/sk≦1.98 (10a)
1.89≤fgf/sk≤8.18 (11a)
0.56≦fgf/L≦1.73 (12a)
0.45≦|fgp/fgn|≦1.06 (13a)
It is more preferable to set the numerical ranges of formulas (1) to (13) as follows.

3.30≤td/f≤6.40 (1b)
0.90≦|fn/fp|≦1.35 (2b)
2.53≦L/sk≦5.19 (3b)
0.45≦f/sk≦0.68 (4b)
1.32≦|fg1/f|≦2.64 (5b)
0.65≦|fg1/sk|≦1.53 (6b)
0.77≦fg1/fg2≦1.13 (7b)
0.85≦|fg2/fg3|≦1.48 (8b)
1.63≦fb2/f≦2.90 (9b)
0.81≦fb2/sk≦1.68 (10b)
2.43≤fgf/sk≤6.92 (11b)
0.72≦fgf/L≦1.47 (12b)
0.58≦|fgp/fgn|≦0.90 (13b)
In addition, the first lens group includes a negative meniscus lens convex to the object side as a first negative lens, a biconcave negative lens as a second negative lens, and a third positive lens, which are arranged in order from the object side to the image side. It preferably consists of three lenses. This makes it possible to satisfactorily correct both the chromatic aberration of magnification and the curvature of field with a small number of lenses.

The second lens group is arranged from the object side to the image side and is composed of a cemented lens in which a positive lens and a negative lens are cemented, a positive lens, and a positive lens, for good correction of various aberrations. preferred.

Moreover, it is preferable that all the lenses included in the wide-angle lens be spherical lenses that can be manufactured at a lower cost than aspherical lenses.

Examples 1 to 3 will be described below. Numerical examples 1 to 3 corresponding to Examples 1 to 3 are shown after the description of Examples 1 to 3. FIG.

The wide-angle lens of Example 1 (numerical example 1) shown in FIG. 1 is a single focus lens with a focal length of 8.20 mm, an open F number of 4.12, and a half angle of view of 86.4°.

The wide-angle lens of this embodiment comprises a first lens group B1 with negative refractive power, an aperture stop SP, and a second lens group B2 with positive refractive power, which are arranged in order from the object side to the image side. When focusing from infinity to very close, the entire wide-angle lens moves toward the object.

The first lens group B1 includes a negative meniscus lens convex to the object side as a first negative lens, a biconcave negative lens as a second negative lens, and a third positive lens, which are arranged in order from the object side to the image side. It is composed of The second lens group B2 is composed of a cemented lens in which a positive lens and a negative lens are cemented, a positive meniscus lens convex to the image side, and a biconvex positive lens arranged in order from the object side to the image side. ing.

FIG. 2 shows the longitudinal aberration (spherical aberration, astigmatism, distortion and chromatic aberration) of the wide-angle lens of this embodiment when focused on infinity. In the spherical aberration diagrams, Fno indicates the open F-number, the solid line indicates spherical aberration for the d-line (wavelength 587.6 nm), and the chain double-dashed line indicates spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagrams, ω is the half angle of view (°), the solid line S indicates the sagittal image plane, and the dashed line M indicates the meridional image plane. The distortion diagram shows the distortion with respect to the d-line. The chromatic aberration diagram shows the chromatic aberration of magnification at the g-line. The wide-angle lens of this embodiment adopts the equisolid angle projection method (Y=2fsin(θ/2)), but the distortion aberration is shown by the general aberration diagram display method. However, the projection method is not limited to the equisolid angle projection method, and other projection methods may be adopted. The explanation for these aberration diagrams is the same for other embodiments described later.

Table 1 summarizes the values corresponding to formulas (1) to (13) in this embodiment. As can be seen from Table 1, the wide-angle lens of this embodiment satisfies Equations (1) to (13).

The wide-angle lens of Example 2 (numerical example 2) shown in FIG. 3 is a single focus lens with a focal length of 7.09 mm, an open F number of 4.12, and a half angle of view of 105.0°.

The wide-angle lens of this embodiment comprises a first lens group B1 with positive refractive power, an aperture stop SP, and a second lens group B2 with positive refractive power, which are arranged in order from the object side to the image side. When focusing from infinity to very close, the entire wide-angle lens moves toward the object.

The first lens group B1 includes a negative meniscus lens convex to the object side as a first negative lens, a biconcave negative lens as a second negative lens, and a third positive lens, which are arranged in order from the object side to the image side. It is composed of The second lens group B2 includes a cemented lens in which a positive lens and a negative lens are cemented, arranged in order from the object side to the image side, a positive meniscus lens convex to the image side, and a positive meniscus lens convex to the object side. It is composed of

FIG. 4 shows the longitudinal aberration of the wide-angle lens of this embodiment when focused on infinity.

Table 1 summarizes the values corresponding to formulas (1) to (13) in this embodiment. As can be seen from Table 1, the wide-angle lens of this embodiment satisfies Equations (1) to (13).

The wide-angle lens of Example 3 (numerical example 3) shown in FIG. 5 is a single focus lens with a focal length of 8.20 mm, an open F number of 4.12, and a half angle of view of 86.2°.

The wide-angle lens of this embodiment comprises a first lens group B1 with positive refractive power, an aperture stop SP, and a second lens group B2 with positive refractive power, which are arranged in order from the object side to the image side. When focusing from infinity to very close, the entire wide-angle lens moves toward the object.

The first lens group B1 includes a negative meniscus lens convex to the object side as a first negative lens, a biconcave negative lens as a second negative lens, and a third positive lens, which are arranged in order from the object side to the image side. It is composed of The second lens group B2 is composed of a cemented lens in which a positive lens and a negative lens are cemented, and a positive meniscus lens convex to the image side, which are arranged in order from the object side to the image side.

FIG. 6 shows the longitudinal aberration of the wide-angle lens of this embodiment when focused on infinity.

Table 1 summarizes the values corresponding to formulas (1) to (13) in this embodiment. As can be seen from Table 1, the wide-angle lens of this embodiment satisfies Equations (1) to (13).

In each of the above embodiments, the first lens group B1 includes only one positive lens and the second lens group B2 includes only one negative lens. A lens may be included, and a plurality of negative lenses may be included in the second lens group B2. However, from the viewpoint of miniaturization, it is preferable that the total number of wide-angle lenses is 8 or less.

Numerical examples 1 to 3 are shown below. In each numerical example, the surface number i indicates the order of surfaces counted from the object side. r is the radius of curvature of the i-th surface from the object side (mm), d is the lens thickness or air gap (mm) between the i-th and (i+1)-th surfaces, and nd is the distance between the i-th and (i+1)-th surfaces. is the refractive index for the d-line of the optical material. νd is the Abbe number with respect to the d-line of the optical material between the i-th surface and the (i+1)-th surface. The Abbe number νd is defined as νd=(Nd−1 )/(NF-NC).

sk is the back focus (mm), which is the air-converted distance on the optical axis from the lens surface closest to the image side of the wide-angle lens to the image plane, as described above. The total lens length is the length obtained by adding the back focus to the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the wide-angle lens.

(Numerical example 1)
unit mm

Surface data surface number rd nd νd
1 24.739 1.00 1.90366 31.3
2 7.409 6.20
3 -26.697 1.00 1.49700 81.5
4 9.521 1.17
5 12.154 3.10 2.00100 29.1
6 -63.879 3.88
7 (Aperture) ∞ 1.00
8 -44.003 5.73 1.59522 67.7
9 -5.028 1.00 1.78472 25.7
10 -12.591 0.10
11 -110.196 2.85 1.49700 81.5
12 -14.971 0.10
13 37.049 2.88 1.48749 70.2
14 -51.617 14.38
15 ∞ 1.50 1.51633 64.1
16 ∞ 0.58
Image plane ∞

Focal length 8.20
F number 4.12
Angle of view (°) 86.4 (by ray tracing)
Image height 11.15
Lens length 45.94
sk 15.94

Lens group data group Starting surface Focal length
1 1 -63.08
2 7 14.87
3 15 ∞

(Numerical example 2)
unit mm

Surface data surface number rd nd νd
1 36.734 4.20 1.90366 31.3
2 8.980 9.10
3 -30.038 1.00 1.49700 81.5
4 11.011 3.22
5 16.020 3.23 2.00100 29.1
6 -53.904 4.60
7 (Aperture) ∞ 1.05
8 -89.022 5.50 1.59522 67.7
9 -4.632 1.00 1.78472 25.7
10 -12.747 0.47
11 -35.508 3.01 1.49700 81.5
12 -11.169 3.29
13 16.638 2.98 1.48749 70.2
14 29.711 9.52
15 ∞ 1.50 1.51633 64.1
16 ∞ 0.48
Image plane ∞

Focal length 7.09
F number 4.12
Angle of view (°) 105.0 (by ray tracing)
Image height 11.15
Lens length 53.63
sk 10.98

Lens group data group Starting surface Focal length
1 1 121.08
2 7 16.24
3 15 ∞

(Numerical example 3)
unit mm

Surface data surface number rd nd νd
1 42.529 2.00 1.90366 31.3
2 12.269 8.34
3 -48.409 1.00 1.49700 81.5
4 11.929 9.30
5 22.640 2.94 2.00100 29.1
6 -182.933 9.58
7 (Aperture) ∞ 1.39
8 746.972 4.74 1.59522 67.7
9 -5.553 1.00 1.78472 25.7
10 -11.714 8.75
11 -44.629 2.95 1.49700 81.5
12 -16.884 11.87
13 ∞ 1.50 1.51633 64.1
14 ∞ 0.58
Image plane ∞

Focal length 8.20
F number 4.12
Angle of view (°) 86.2 (by ray tracing)
Image height 11.15
Lens length 65.44
BF 13.44

Lens group data group Starting surface Focal length
1 1 223.89
2 7 21.60
3 13 ∞

FIG. 7 shows a digital still camera as an imaging apparatus using the wide-angle lens of each of the above embodiments as an imaging optical system. Reference numeral 10 denotes a camera body, and 11 denotes a wide-angle lens according to any one of Examples 1-3. Reference numeral 12 denotes a solid-state imaging device such as a CCD sensor or CMOS sensor, which is built in the camera body 10 and captures an optical image (object image) formed by the wide-angle lens 11 .

By using the wide-angle lens of each embodiment, it is possible to obtain a compact image pickup apparatus having high optical performance. Note that the imaging device may be a single-lens reflex camera having a quick turn mirror or a mirrorless camera without a quick turn mirror.

Each embodiment described above is merely a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

B1 First lens group SP Aperture diaphragm B2 Second lens group

Claims (17)

An optical system with a half angle of view of 80° or more, consisting of a first lens group with negative or positive refractive power, an aperture diaphragm, and a second lens group with positive refractive power, arranged in order from the object side to the image side. and
The first lens group has a plurality of negative lenses including a first negative lens and a second negative lens arranged in order from the object side to the image side, and at least one positive lens,
The second lens group has at least one negative lens and a plurality of positive lenses,
td is the distance on the optical axis from the most object-side lens surface to the most image-side lens surface in the optical system, f is the focal length of the optical system, and the focal points of the plurality of negative lenses in the first lens group Let fn be the average distance and fp be the average focal length of the at least one positive lens in the first lens group,
2.00≤td/f≤6.50
0.80≦|fn/fp|≦2.00
An optical system characterized by satisfying the following condition. 2. The optical system according to claim 1, wherein said half angle of view is 110[deg.] or less. When the distance on the optical axis from the most object side lens surface to the image plane is L, and the air conversion distance on the optical axis from the most image side lens surface to the image plane is sk,
1.41≤L/sk≤7.08
3. The optical system according to claim 1, wherein the following condition is satisfied. When the air conversion distance on the optical axis from the most image side lens surface to the image plane is sk,
0.25≤f/sk≤0.93
4. The optical system according to any one of claims 1 to 3, wherein the following condition is satisfied. When the focal length of the first negative lens is fg1,
0.73≦|fg1/f|≦3.60
5. The optical system according to any one of claims 1 to 4, wherein the following condition is satisfied. When the focal length of the first negative lens is fg1 and the air conversion distance on the optical axis from the most image side lens surface to the image plane is sk,
0.36≦|fg1/sk|≦2.09
6. The optical system according to any one of claims 1 to 5, wherein the following condition is satisfied. When the focal length of the first negative lens is fg1 and the focal length of the second negative lens is fg2,
0.43≦fg1/fg2≦1.54
7. The optical system according to any one of claims 1 to 6, wherein the following condition is satisfied. When the focal length of the second negative lens is fg2, and the focal length of the positive lens arranged third from the object side in the first lens group is fg3,
0.47≦|fg2/fg3|≦2.02
8. The optical system according to any one of claims 1 to 7, wherein the following condition is satisfied. When the focal length of the second lens group is fb2,
0.91≦fb2/f≦3.95
9. The optical system according to any one of claims 1 to 8, wherein the following condition is satisfied. When the focal length of the second lens group is fb2, and the air conversion distance on the optical axis from the lens surface closest to the image side to the image plane is sk,
0.45≦fb2/sk≦2.29
10. The optical system according to any one of claims 1 to 9, wherein the following condition is satisfied. When one of the at least one positive lens in the second lens group is arranged closest to the image side, fgf is the focal length of the positive lens, and on the optical axis from the lens surface closest to the image side to the image plane. When the air conversion distance of is sk,
1.35≤fgf/sk≤9.44
11. The optical system according to any one of claims 1 to 10, wherein the following condition is satisfied. When one of the at least one positive lens in the second lens group is arranged closest to the image side, fgf is the focal length of the positive lens, and on the optical axis from the lens surface closest to the object side to the image plane. When the distance between is L,
0.40≤fgf/L≤2.00
12. The optical system according to any one of claims 1 to 11, wherein the following condition is satisfied. The second lens group has a cemented lens in which a positive lens and a negative lens are cemented,
When the focal lengths of the positive lens and the negative lens in the cemented lens are fgp and fgn, respectively,
0.32≦|fgp/fgn|≦1.23
13. The optical system according to any one of claims 1 to 12, wherein the following condition is satisfied. 14. The first lens group according to any one of claims 1 to 13, wherein the first lens group comprises a negative meniscus lens convex to the object side as the first negative lens, a biconcave lens as the second negative lens, and the positive lens. 1. The optical system according to claim 1. 15. The second lens group according to any one of claims 1 to 14, wherein the second lens group comprises a cemented lens in which a positive lens and a negative lens are cemented, a positive lens, and a positive lens, which are arranged in order from the object side to the image side. 2. The optical system according to item 1. 16. The optical system according to any one of claims 1 to 15, wherein all lens surfaces of said optical system are spherical. an optical system according to any one of claims 1 to 16;
and an imaging device for imaging an object through the optical system.

Images