JP7286893B2 - WIDE-ANGLE OPTICAL SYSTEM AND IMAGING DEVICE HAVING THE SAME - Google Patents

Description

The present invention relates to a wide-angle optical system having an angle of view exceeding 180 degrees and an imaging apparatus having the same.

2. Description of the Related Art Conventionally, a wide-angle optical system capable of imaging a wide imaging range suitable for an in-vehicle camera or a surveillance camera has been known. (For example, Patent Document 1 or Patent Document 2).

JP 2008-134494 A Japanese Patent No. 2010-256627

By the way, in recent years, as applications for cameras using these wide-angle optical systems, in addition to the conventional rear view camera for the purpose of visual field assistance, Advanced Driving Assistance Systems (ADAS: Advanced Driver Assistance Systems) that enhance preventive safety of automobiles such as automatic braking Cameras for Driving Assistant System) are rapidly becoming popular. In addition, cameras for recording driving images such as drive recorders are becoming popular. In addition to these in-vehicle applications, cameras for security purposes are widely installed in public institutions, roads, and the like. These cameras are required to have high image quality and high imaging performance over the entire imaging range in order to accurately capture people and objects over a wide range.

In addition, it is required to eliminate fluctuations in the focal position and suppress the occurrence of various aberrations over the entire range of wavelengths used in a wide range of environmental temperatures (extremely high and extremely low temperatures) in which the camera operates.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems and to achieve the following objects. That is, the present invention achieves high image quality and high imaging performance over the entire imaging range, and eliminates fluctuations in focal position and over the entire operating wavelength range in a wide range of environmental temperatures (extremely high and extremely low temperatures) in which the camera operates. It is an object of the present invention to provide a wide-angle optical system and an imaging device that suppress the occurrence of various aberrations.

A wide-angle optical system according to claim 1 is a wide-angle optical system having an angle of view exceeding 180 degrees, comprising a front group, an aperture stop and a rear group arranged in order from the object side, the front group comprising: Consisting of a first lens with negative refractive power, a second lens with negative refractive power, a third lens with negative refractive power, and a fourth lens with positive refractive power, arranged in order from the object side, The rear group includes a fifth lens having positive refractive power, a sixth lens having negative refractive power, a seventh lens having negative refractive power, and a third lens having positive refractive power, which are arranged in order from the object side. It consists of 8 lenses,
A wide-angle optical system characterized by satisfying the following conditional expression.
-0.05<f/f6-f/f7<0.05 (1)
0.3<r12/r13<1.5 (3)
here,
f is the focal length of the entire wide-angle optical system,
f6 is the focal length of the sixth lens,
f7 is the focal length of the seventh lens,
r12 is the radius of curvature of the image-side surface of the sixth lens;
r13 is the radius of curvature of the object-side surface of the seventh lens;
is.

The wide-angle optical system described in claim 2 preferably satisfies the following conditional expression instead of conditional expression (1) in the wide-angle optical system described in claim 1.
-0.05<f/f6-f/f7<0 (2)

A wide-angle optical system according to claim 3 is the wide-angle optical system according to claim 1 or claim 2 , wherein any two of the fifth lens, the sixth lens, and the seventh lens constituting the rear group Preferably, the material of the lens is optical glass, and the material of one lens is plastic.

The wide-angle optical system described in claim 4 is the wide-angle optical system described in any one of claims 1 to 3, wherein the seventh lens is preferably a biconcave lens.

The imaging device according to claim 5 , the wide-angle optical system according to any one of claims 1 to 4,
and a solid-state imaging device.

According to the present invention, it is possible to achieve both high image quality and high imaging performance over the entire field of view of a wide imaging area, eliminate fluctuations in focal position due to temperature changes in the usage environment, and generate various aberrations over the entire range of usage wavelengths. can be suppressed.

1 is a cross-sectional view along an optical axis showing an optical configuration of a wide-angle optical system according to Example 1 of the present invention; FIG. 4A and 4B are diagrams showing (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 1 is focused on an object point at infinity; FIG. 5 is a cross-sectional view along the optical axis showing the optical configuration of a wide-angle optical system according to Example 2 of the present invention; 8A and 8B are diagrams showing (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 2 is focused on an object point at infinity; FIG. 10 is a cross-sectional view along the optical axis showing the optical configuration of a wide-angle optical system according to Example 3 of the present invention; FIG. 11 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 3 is focused on an object point at infinity. FIG. 5 is a cross-sectional view along the optical axis showing the optical configuration of a wide-angle optical system according to Example 4 of the present invention; FIG. 12 is a diagram showing (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when focusing on an object point at infinity of the wide-angle optical system according to Example 4; FIG. 11 is a cross-sectional view along the optical axis showing the optical configuration of a wide-angle optical system according to Example 5 of the present invention; FIG. 10 is a diagram showing (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when focusing on an object point at infinity of the wide-angle optical system according to Example 5; FIG. 6 is a cross-sectional view along the optical axis showing the optical configuration of a wide-angle optical system according to Example 6 of the present invention; FIG. 10 is a diagram showing (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when focusing on an object point at infinity of the wide-angle optical system according to Example 6;

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view along the optical axis showing an example of the optical configuration of a wide-angle optical system according to an embodiment of the present invention. The optical arrangement of FIG. 1 corresponds to the optical arrangement of the first embodiment.

The wide-angle optical system of the present invention comprises, in order from the object side, a front group, an aperture stop S, and a rear group. , a second lens L2 having negative refractive power, a third lens L3 having negative refractive power, and a fourth lens L4 having positive refractive power.

The lens group in the rear group with the aperture diaphragm S interposed therebetween is, in order from the object side, a fifth lens L5 having positive refractive power, a sixth lens L6 having negative refractive power, and a negative refractive power. and an eighth lens L8 having a positive refractive power.
In all the examples below, CG indicates a cover glass, and I indicates an imaging surface of an imaging element in cross-sectional views of the optical configuration.

The rear lens group of the present invention has a four-lens structure including two negative lenses arranged adjacent to the positive lens L5 closest to the object side. Variation can be minimized.

In the wide-angle optical system of the present invention, both the fifth lens L5 and the sixth lens L6 are cemented lenses made of glass, and at least the seventh lens is an aspherical plastic lens. However, as shown in a fourth embodiment described later, the fifth lens L5 and the seventh lens L7 are glass lenses, the sixth lens L6 is a plastic lens, and the fifth lens L5 and the sixth lens L6 may be non-bonded.

An imaging element such as a CCD is arranged on the imaging plane I of the wide-angle optical system of the present invention. Various optical elements such as an infrared cut filter may be arranged in the space between the eighth lens L8 and the cover glass CG.

Further, the wide-angle optical system according to the present embodiment is preferably configured as an optical system of a stereoscopic projection method as a projection method in order to ensure the amount of information (visibility) in the peripheral portion of the wide field of view.

The wide-angle optical system according to the present embodiment realizes a wide-angle optical system with an angle of view exceeding 180 degrees and a stereoscopic projection method by the first lens L1 to the fourth lens L4 that constitute the front group, and constitutes the rear group. The fifth lens L5 through the eighth lens L8 enable effective correction of various aberrations occurring in these wide-angle stereoscopic projection images.

Further, in the wide-angle optical system according to the present embodiment, the second lens L2 has a concave surface on the object side in the vicinity of the optical axis. (back focus) becomes longer, and a space for installing various optical elements such as an infrared cut filter can be secured between the eighth lens L8 and the cover glass CG.

Further, the wide-angle optical system according to this embodiment satisfies the following conditional expressions.
-0.05<f/f6-f/f7<0.05 (1)
here,
f is the focal length of the entire wide-angle optical system,
f6 is the focal length of the sixth lens,
f7 is the focal length of the seventh lens,
is.

Conditional expression (1) is a conditional expression for making it possible to eliminate fluctuations in the focal position even in a wide range of operating environments from extremely low temperatures to extremely high temperatures.

Further, the wide-angle optical system of this embodiment satisfies the following conditional expressions.
0.3<r12/r13<1.5 (2)
here,
r12 is the radius of curvature of the image-side surface of the sixth lens;
r13 is the radius of curvature of the object-side surface of the seventh lens.

Conditional expression (2) optimizes the radius of curvature of the image-side surface of the sixth lens L6 and the radius of curvature of the object-side surface of the seventh lens L7 to satisfactorily correct spherical aberration occurring in the optical system. is a conditional expression.

An imaging apparatus of the present invention includes the imaging optical system of the present invention and a solid-state imaging device such as CCD or CMOS.

Next, specific numerical examples of the wide-angle optical system of the present invention will be shown. The symbols used in each example are as follows.

f: Focal length of the entire imaging optical system FNO: F-number FOV (2ω): Angle of view r: Paraxial radius of curvature d: Thickness of lens on optical axis or air gap nd: Refractive index of lens material for d-line νd : Abbe number of lens material In addition, in each example, the surfaces with "*" after each surface number are surfaces having an aspherical shape.

Further, the aspherical shape is defined by the following formula (I ).
z=(y ² /r)/[1+{1−(1+K)(y/r) ² } ^1/2 ]+A4y ⁴ +A6y ⁶ +A8y ⁸ +A10y ¹⁰ (I)
In addition, in the aspheric coefficient, E indicates a power of 10, and for example, 2.3×10 ⁻² is expressed as 2.3E-002. Also, the symbols of these specification values are common to the numerical data of the embodiments described later.

Next, a wide-angle optical system according to Example 1 will be described.
FIG. 1 is a cross-sectional view along the optical axis showing the optical configuration of a wide-angle optical system according to Example 1. FIG.

FIG. 2 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 1 is focused on an object point at infinity. It is a diagram. Further, Y in the drawing indicates the image height. It should be noted that the symbols in the aberration diagrams are also common to the examples described later.

As shown in FIG. 1, this wide-angle optical system includes, in order from the object side, a meniscus first lens L1 having a convex surface facing the object side and having negative refractive power, and a negative lens L1 having a biconcave shape near the optical axis. a second lens L2 having a refractive power of, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, an aperture stop S, and a fifth lens L5 having a positive refractive power and a sixth lens L6 having negative refractive power, a seventh lens L7 having a biconcave shape and having negative refractive power, and a biconvex seventh lens L7 having positive refractive power, there is

In the wide-angle optical system according to Example 1, both the fifth lens L5 and the sixth lens L6 are glass cemented lenses, and at least the seventh lens is an aspherical plastic lens.

In this wide-angle optical system, the fifth lens L5 and the sixth lens L6 are cemented glass lenses, and the seventh lens is a plastic lens. can be prevented.

The overall specifications of the wide-angle optical system of Example 1 are shown below.
f: 0.79mm
FNO: 2.40
FOV (ω): 100.00°
Surface data of the wide-angle optical system of Example 1 are shown below (unit: mm).

Aspheric surface data of the wide-angle optical system of Example 1 are shown below.
3rd side
K=0
A4=1.881E-03, A6=-2.524E-05, A8=1.804E-07
4th side
K=0
A4=-7.476E-03, A6= 5.099E-04, A8=-1.242E-05
5th side
K=0
A4=5.106E-03, A6=-7.694E-04, A8=3.194E-05
6th side
K=0
A4=2.166E-02, A6=-1.030E-02, A8=5.075E-04
7th side
K=0
A4=1.266E-02, A6=-3.655E-03, A8=2.677E-04
8th side
K=0
A4=3.480E-03, A6=8.644E-04, A8=1.742E-04
13th side
K=0
A4=-3.524E-02, A6= 9.327E-03, A8=-1.434E-03
14th side
K=0
A4=-2.077E-02, A6=9.154E-03, A8=-3.144E-03
15th side
K=0
A4=5.655E-03, A6= 3.239E-03, A8= -1.382E-03, A10= -2.450E-05
16th side
K=0
A4=3.094E-02, A6=-1.530E-03, A8=2.400E-03, A10=9.255E-07

Values corresponding to conditional expressions (1) to (4) of the wide-angle optical system of Example 1 are shown below.
(1) f/f6-f/f7=-0.036
(2) r12/r13 = 0.440
In the wide-angle optical system of Example 1, the fifth and sixth lenses are made of glass material, and the other lenses are made of plastic material.

Next, a wide-angle optical system according to Example 2 will be described.
FIG. 3 is a cross-sectional view along the optical axis showing the optical configuration of the wide-angle optical system according to the second embodiment.

FIG. 4 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 2 is focused on an object point at infinity. It is a diagram. Further, Y in the drawing indicates the image height. It should be noted that the symbols in the aberration diagrams are also common to the examples described later.

As shown in FIG. 3, this wide-angle optical system includes, in order from the object side, a meniscus-shaped first lens L1 having a convex surface facing the object side and having negative refractive power, and a negative lens L1 having a biconcave shape near the optical axis. a second lens L2 having a refractive power of, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, an aperture stop S, and a fifth lens L5 having a positive refractive power and a sixth lens L6 having negative refractive power, a seventh lens L7 having a biconcave shape and having negative refractive power, and a biconvex seventh lens L7 having positive refractive power, there is

In the wide-angle optical system according to Example 2, both the fifth lens L5 and the sixth lens L6 are glass cemented lenses, and at least the seventh lens is an aspherical plastic lens.

In this wide-angle optical system, the fifth lens L5 and the sixth lens L6 are cemented glass lenses, and the seventh lens is a plastic lens. can be prevented.

The overall specifications of the wide-angle optical system of Example 2 are shown below.
f: 0.79mm
FNO: 2.40
FOV (ω): 105.00°
Surface data of the wide-angle optical system of Example 2 are shown below (unit: mm).

Aspheric surface data of the wide-angle optical system of Example 2 are shown below.
3rd side
K=0
A4=2.099E-03, A6=-3.180E-05, A8=2.584E-07
4th side
K=0
A4=-7.296E-03, A6=4.189E-04, A8=-1.090E-06
5th side
K=0
A4=2.914E-03, A6=-1.813E-04, A8=4.035E-06
6th side
K=0
A4=2.204E-02, A6=-9.309E-03, A8=-3.111E-04
7th side
K=0
A4=1.717E-02, A6=-5.137E-03, A8=8.153E-08
8th side
K=0
A4=7.211E-03, A6=5.385E-04, A8=-4.523E-08
13th side
K=0
A4=-1.035E-02
14th side
K=0
A4=-4.544E-03
15th side
K=0
A4=-1.329E-02, A6=6.944E-03, A8=-1.323E-03
16th side
K=0
A4=2.834E-02, A6=-2.931E-05, A8=2.318E-03

Values corresponding to conditional expressions (1) to (4) of the wide-angle optical system of Example 2 are shown below.
(1) f/f6-f/f7=-0.017
(2) r12/r13 = 1.311
In the wide-angle optical system of Example 2, the fifth and sixth lenses are made of glass material, and the other lenses are made of plastic material.

Next, a wide-angle optical system according to Example 3 will be described.
FIG. 5 is a cross-sectional view along the optical axis showing the optical configuration of the wide-angle optical system according to the third embodiment.

FIG. 6 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 3 is focused on an object point at infinity. It is a diagram. Further, Y in the drawing indicates the image height. It should be noted that the symbols in the aberration diagrams are also common to the examples described later.

As shown in FIG. 5, this wide-angle optical system includes, in order from the object side, a meniscus-shaped first lens L1 having a convex surface facing the object side and having negative refractive power, and a negative lens L1 having a biconcave shape near the optical axis. a second lens L2 having a refractive power of, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, an aperture stop S, and a fifth lens L5 having a positive refractive power and a sixth lens L6 having negative refractive power, a seventh lens L7 having a biconcave shape and having negative refractive power, and a biconvex seventh lens L7 having positive refractive power, there is

In the wide-angle optical system according to Example 3, both the fifth lens L5 and the sixth lens L6 are glass cemented lenses, and at least the seventh lens is an aspherical plastic lens.

In this wide-angle optical system, the fifth lens L5 and the sixth lens L6 are cemented glass lenses, and the seventh lens is a plastic lens. can be prevented.

The overall specifications of the wide-angle optical system of Example 3 are shown below.
f: 0.80mm
FNO: 2.40
FOV (ω): 105.00°
Surface data of the wide-angle optical system of Example 3 are shown below (unit: mm).

Aspheric surface data of the wide-angle optical system of Example 3 are shown below.
3rd side
K=0
A4=1.949E-03, A6=-2.796E-05, A8=2.369E-07
4th side
K=0
A4=-1.155E-02, A6=8.234E-04, A8=-3.218E-05
5th side
K=0
A4=8.288E-04, A6=-1.357E-04, A8=1.202E-05, A10=-5.925E-08
6th side
K=0
A4=1.864E-02, A6=-1.228E-02, A8=2.908E-04, A10=-1.026E-05
7th side
K=0
A4=1.070E-02, A6=-4.430E-03, A8=1.233E-05
8th side
K=0
A4=-3.990E-04, A6=1.069E-02, A8=-3.872E-03
13th side
K=0
A4=-2.558E-03, A6=-7.605E-04, A8= 4.215E-04
14th side
K=0
A4=5.892E-05, A6=-1.936E-03, A8=-3.012E-05
15th side
K=0
A4=-1.716E-02, A6=1.346E-02, A8=-2.006E-03
16th side
K=0
A4=2.916E-02, A6=-2.385E-03, A8=4.931E-03

Values corresponding to conditional expressions (1) to (4) of the wide-angle optical system of Example 3 are shown below.
(1) f/f6-f/f7=0.028
(2) r12/r13 = 1.159
In the wide-angle optical system of Example 3, the fifth and sixth lenses are made of glass material, and the other lenses are made of plastic material.

Next, a wide-angle optical system according to Example 4 will be described.
FIG. 7 is a cross-sectional view along the optical axis showing the optical configuration of the wide-angle optical system according to the fourth embodiment.

FIG. 8 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 4 is focused on an object point at infinity. It is a diagram. Further, Y in the drawing indicates the image height. It should be noted that the symbols in the aberration diagrams are also common to the examples described later.

As shown in FIG. 7, this wide-angle optical system includes, in order from the object side, a meniscus-shaped first lens L1 having a convex surface facing the object side and having negative refractive power, and a negative lens L1 having a biconcave shape near the optical axis. a second lens L2 having a refractive power of, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, an aperture stop S, and a fifth lens L5 having a positive refractive power and a sixth lens L6 having negative refractive power, a seventh lens L7 having a biconcave shape and having negative refractive power, and a biconvex seventh lens L7 having positive refractive power, there is

In the wide-angle optical system according to Example 4, the fifth lens L5 and the seventh lens L7 are glass lenses, the sixth lens L6 is a plastic lens, and the fifth lens L5 and the sixth lens L6 are non-bonded.

In this wide-angle optical system, the fifth lens L5 and the seventh lens L7 are made of glass, and the sixth lens is made of plastic. can do

The overall specifications of the wide-angle optical system of Example 4 are shown below.
f: 0.795mm
FNO: 2.40
FOV (ω): 100.00°
Surface data of the wide-angle optical system of Example 4 are shown below (unit: mm).

Aspheric surface data of the wide-angle optical system of Example 4 are shown below.
3rd side
K=0
A4= 2.099E-03, A6= -3.086E-05, A8= 3.035E-07
4th side
K=0
A4= -1.362E-02, A6= 9.751E-04, A8= -4.749E-05
5th side
K=0
A4= 1.746E-03, A6= -5.037E-05, A8= 1.089E-05
6th side
K=0
A4= 2.240E-02, A6= -1.392E-02, A8= -5.032E-05
7th side
K=0
A4= 9.964E-03, A6= -4.875E-03, A8= -7.363E-04
8th side
K=0
A4= 6.040E-03, A6= 9.955E-03, A8= -3.155E-03
16th side
K=0
A4= -5.089E-03, A6= 1.698E-02, A8= -2.255E-03
17th side
K=0
A4= 4.181E-02, A6= 5.650E-04, A8= 6.916E-03

Values corresponding to conditional expressions (1) to (4) of the wide-angle optical system of Example 4 are shown below.
(1) f/f6-f/f7=-0.020
(2) r12/r13 = 1.241
In the wide-angle optical system of Example 4, the fifth and seventh lenses are made of glass material, and the other lenses are made of plastic material.

Next, a wide-angle optical system according to Example 5 will be described.
FIG. 9 is a cross-sectional view along the optical axis showing the optical configuration of the wide-angle optical system according to the fifth embodiment.

FIG. 10 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 5 is focused on an object point at infinity. It is a diagram. Further, Y in the drawing indicates the image height. It should be noted that the symbols in the aberration diagrams are also common to the examples described later.

As shown in FIG. 9, this wide-angle optical system includes, in order from the object side, a meniscus-shaped first lens L1 having a convex surface facing the object side and having negative refractive power, and a negative lens L1 having a biconcave shape near the optical axis. a second lens L2 having a refractive power of, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, an aperture stop S, and a fifth lens L5 having a positive refractive power and a sixth lens L6 having negative refractive power, a seventh lens L7 having a biconcave shape and having negative refractive power, and a biconvex seventh lens L7 having positive refractive power, there is

In the wide-angle optical system according to Example 5, both the fifth lens L5 and the sixth lens L6 are glass cemented lenses, and at least the seventh lens is an aspherical plastic lens.

In this wide-angle optical system, the fifth lens L5 and the sixth lens L6 are cemented glass lenses, and the seventh lens is a plastic lens. can be prevented.

The overall specifications of the wide-angle optical system of Example 5 are shown below.
f: 0.793mm
FNO: 2.40
FOV (ω): 100.00°
Surface data of the wide-angle optical system of Example 5 are shown below (unit: mm).

Aspheric surface data of the wide-angle optical system of Example 5 are shown below.
3rd side
K=0
A4=1.848E-03, A6=-2.527E-05, A8=1.826E-07
4th side
K=0
A4=-7.331E-03, A6=5.378E-04, A8=-1.427E-05
5th side
K=0
A4=4.947E-03, A6=-7.888E-04, A8=3.584E-05
6th side
K=0
A4=2.231E-02, A6=-1.005E-02, A8=4.644E-04
7th side
K=0
A4=1.260E-02, A6=-3.725E-03, A8=2.570E-04
8th side
K=0
A4=3.008E-03, A6=1.320E-03, A8=1.919E-04
13th side
K=0
A4=-3.904E-02, A6=9.894E-03, A8=-6.975E-04
14th side
K=0
A4=-1.934E-02, A6=8.297E-03, A8=-2.774E-03
15th side
K=0
A4=8.420E-03, A6=4.813E-03, A8=-1.924E-03
16th side
K=0
A4=2.770E-02, A6=-1.074E-03, A8=2.813E-03

Values corresponding to conditional expressions (1) to (4) of the wide-angle optical system of Example 5 are shown below.
(1) f/f6-f/f7=-0.010
(2) r12/r13 = 0.396
In the wide-angle optical system of Example 5, the fifth and sixth lenses are made of glass material, and the other lenses are made of plastic material.

Next, a wide-angle optical system according to Example 5 will be described.
Next, a wide-angle optical system according to Example 6 will be described.
FIG. 11 is a cross-sectional view along the optical axis showing the optical configuration of the wide-angle optical system according to the sixth embodiment.

FIG. 12 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the wide-angle optical system according to Example 6 is focused on an object point at infinity. It is a diagram. Further, Y in the drawing indicates the image height. It should be noted that the symbols in the aberration diagrams are also common to the examples described later.

As shown in FIG. 11, this wide-angle optical system includes, in order from the object side, a meniscus-shaped first lens L1 having a convex surface facing the object side and having negative refractive power, and a negative lens L1 having a biconcave shape near the optical axis. a second lens L2 having a refractive power of, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, an aperture stop S, and a fifth lens L5 having a positive refractive power and a sixth lens L6 having negative refractive power, a seventh lens L7 having a biconcave shape and having negative refractive power, and a biconvex seventh lens L7 having positive refractive power, there is

In the wide-angle optical system according to Example 6, both the fifth lens L5 and the sixth lens L6 are glass cemented lenses, and at least the seventh lens is an aspherical plastic lens.

In this wide-angle optical system, the fifth lens L5 and the sixth lens L6 are cemented glass lenses, and the seventh lens is a plastic lens. can be prevented.

The overall specifications of the wide-angle optical system of Example 6 are shown below.
f: 0.79mm
FNO: 2.40
FOV (ω): 100.00°
Surface data of the wide-angle optical system of Example 6 are shown below (unit: mm).

Aspheric surface data of the wide-angle optical system of Example 6 are shown below.
3rd side
K=0
A4=2.053E-03, A6=-2.645E-05, A8=1.876E-07
4th side
K=0
A4=-7.632E-03, A6=5.375E-04, A8=-1.165E-05
5th side
K=0
A4=5.133E-03, A6=-8.450E-04, A8=3.455E-05
6th side
K=0
A4=1.760E-02, A6=-1.147E-02, A8=5.344E-04
7th side
K=0
A4=9.003E-03, A6=-4.014E-03, A8=1.457E-04
8th side
K=0
A4=3.226E-03, A6=6.333E-04, A8=3.703E-04
13th side
K=0
A4=-4.044E-02, A6=-5.132E-04, A8=3.464E-03
14th side
K=0
A4=-3.640E-02, A6=1.019E-02, A8=-1.671E-03
15th side
K=0
A4=-6.792E-03, A6=1.241E-02, A8=-1.979E-03
16th side
K=0
A4=3.060E-02, A6=1.222E-03, A8=2.906E-03

Values corresponding to conditional expressions (1) to (4) of the wide-angle optical system of Example 6 are shown below.
(1) f/f6-f/f7=-0.049
(2) r12/r13 = 0.691
In the wide-angle optical system of Example 6, the fifth and sixth lenses are made of glass material, and the other lenses are made of plastic material.

L1 First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth lens L6 Sixth lens L7 Seventh lens L8 Eighth lens CG Cover glass I Imaging surface S Aperture diaphragm

Claims (5)

A wide-angle optical system having an angle of view exceeding 180 degrees,
A front group, an aperture stop, and a rear group are arranged in order from the object side,
The front group includes a first lens having negative refractive power, a second lens having negative refractive power, a third lens having negative refractive power, and a third lens having positive refractive power, which are arranged in order from the object side. It consists of 4 lenses,
The rear group includes a fifth lens having positive refractive power, a sixth lens having negative refractive power, a seventh lens having negative refractive power, and a third lens having positive refractive power, which are arranged in order from the object side. It consists of 8 lenses,
A wide-angle optical system characterized by satisfying the following conditional expression.
-0.05<f/f6-f/f7<0.05 (1)
0.3<r12/r13<1.5 (3)
here,
f is the focal length of the entire wide-angle optical system,
f6 is the focal length of the sixth lens,
f7 is the focal length of the seventh lens,
r12 is the radius of curvature of the image-side surface of the sixth lens;
r13 is the radius of curvature of the object-side surface of the seventh lens;
is. 2. A wide-angle optical system according to claim 1, wherein the following conditional expression is satisfied instead of conditional expression (1) .
-0.05<f/f6-f/f7<0 (2) The material of any two lenses among the fifth lens, the sixth lens, and the seventh lens constituting the rear group is optical glass, and the material of one lens is plastic. The wide-angle optical system according to claim 1 or 2 . 4. The wide-angle optical system according to claim 1, wherein the seventh lens is a biconcave lens. A wide-angle optical system according to any one of claims 1 to 4 ;
and a solid-state imaging device.

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