JP2018092041A - Image capturing optical system and image capturing device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide-angle image capturing optical system which secures a sufficient amount of information in a peripheral part of an image and provides superior imaging performance over an entire field of view.SOLUTION: An image capturing optical system has a view angle in excess of 180 degrees and is of a stereoscopic projection type. The system consists of a first lens having negative refractive power and a convex surface on the object side, a second lens having negative refractive power, a third lens having negative refractive power, a fourth lens having positive refractive power, an aperture stop, a fifth lens having positive refractive power, a sixth lens having negative refractive power, and a seventh lens having positive refractive power, in order from the object side, and satisfies the following conditional expressions: -23<f1/f<-12 ...(1), -8<f2/f<-5 ...(2), 2.5<f5/f<4.5 ...(3), -3.0<f6/f<-1.9 ...(4).SELECTED DRAWING: Figure 1

Description

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

2. Description of the Related Art Conventionally, in a wide-angle imaging optical system that can capture a wide imaging range, a stereoscopic projection imaging optical system is known as an optical system that secures the amount of information at the periphery of an image. (For example, patent document 1 or patent document 2).

JP 2010-256627 A JP 2008-134494 A

  In recent years, cameras for video recording applications such as drive recorders have been mounted on vehicles and the like. In addition, cameras for security use are installed in public institutions and roads. For such a camera, an image with higher image quality is required, and it is required to realize a wide imaging area and achieve high imaging performance over the entire visual field.

  Furthermore, as an imaging optical system used in day / night cameras that achieve both daytime color reproducibility and nighttime low-light performance, a space for installing various optical element insertion / removal mechanisms such as infrared cut filters is used for these imaging optics. Required by the system.

  An object of the present invention is to solve the above conventional problems and achieve the following objects. That is, the present invention relates to an imaging optical system capable of obtaining a high imaging performance over the entire field of view while ensuring an information amount in an image peripheral portion in an imaging optical system having a wide angle of view capable of imaging a wide imaging range, and the imaging optical system. An object of the present invention is to provide an imaging apparatus using the above. Furthermore, it aims at providing the imaging optical system which has sufficient space for installing various optical element insertion / extraction mechanisms, such as an infrared cut filter, and an imaging device using this imaging optical system.

Means for solving the above problems are as follows. That is, the imaging optical system of the present invention is a stereoscopic projection imaging optical system having an angle of view exceeding 180 degrees, and has negative refractive power in order from the object side, with the convex surface facing the object side. A first lens having a negative refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, an aperture stop, and a first lens having a positive refractive power. 5 lenses, a sixth lens having a negative refractive power, and a seventh lens having a positive refractive power, and satisfy the following conditional expression.
−23 <f1 / f <−12 (1)
-8 <f2 / f <-5 (2)
2.5 <f5 / f <4.5 (3)
-3.0 <f6 / f <-1.9 (4)
here,
f is the focal length of the entire imaging optical system,
f1 is the focal length of the first lens,
f2 is the focal length of the second lens,
f5 is the focal length of the fifth lens,
f6 is the focal length of the sixth lens.

In the imaging optical system of the present invention, it is preferable that the following conditional expression is satisfied.
-0.02 <n6-n5 <0.16 (5)
here,
n5 is the refractive index of the fifth lens with respect to the d-line,
n6 is the refractive index of the sixth lens with respect to the d-line.

In the imaging optical system of the present invention, it is preferable that the following conditional expression is satisfied.
2.4 <f7 / f <3.0 (6)
here,
f7 is the focal length of the seventh lens.

In the imaging optical system of the present invention, it is preferable that the second lens has a concave surface facing the object side.

In the imaging optical system of the present invention, it is preferable that the material of the fifth lens is optical glass.

Moreover, the imaging device of this invention is equipped with the said imaging optical system and a solid-state image sensor.

  According to the present invention, in an imaging optical system having a wide field angle capable of imaging a wide imaging range, there is an effect that high imaging performance can be obtained over the entire visual field while ensuring the information amount of the image peripheral portion. Furthermore, there is an effect that a sufficient space for installing various optical element insertion / removal mechanisms such as an infrared cut filter can be secured.

It is sectional drawing which follows the optical axis which shows the optical structure of the imaging optical system concerning Example 1 of this invention. FIG. 6 is a diagram illustrating (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) when the imaging optical system according to the example 1 is focused on an object point at infinity. It is sectional drawing which follows the optical axis which shows the optical structure of the imaging optical system concerning Example 2 of this invention. FIG. 10 is a diagram illustrating (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion aberration (DT) when an imaging optical system according to Example 2 is focused on an object point at infinity. It is sectional drawing which follows the optical axis which shows the optical structure of the imaging optical system concerning Example 3 of this invention. FIG. 10 is a diagram illustrating (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion aberration (DT) during focusing on an object point at infinity of the imaging optical system according to the third example. It is sectional drawing which follows the optical axis which shows the optical structure of the imaging optical system concerning Example 4 of this invention. FIG. 10 is a diagram illustrating (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion aberration (DT) during focusing on an object point at infinity of the imaging optical system according to the fourth example. It is sectional drawing which follows the optical axis which shows the optical structure of the imaging optical system concerning Example 5 of this invention. FIG. 10 is a diagram illustrating (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion aberration (DT) during focusing on an object point at infinity of the imaging optical system according to the fifth example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view along an optical axis showing an example of an optical configuration of an imaging optical system according to an embodiment of the present invention. The optical configuration of FIG. 1 corresponds to the optical configuration of the first embodiment.

The imaging optical system of the present invention includes, in order from the object side, a meniscus first lens L1 having a negative refractive power with a convex surface facing the object side, a second lens L2 having a negative refractive power, and negative refraction. A third lens L3 having a power, a fourth lens L4 having a positive refractive power, an aperture stop S, a fifth lens L5 having a positive refractive power, a sixth lens L6 having a negative refractive power, The seventh lens L7 has a positive refractive power.
Hereinafter, in all the examples, CG represents a cover glass and I represents an imaging surface of an imaging element in the optical configuration cross-sectional views.

  An imaging element such as a CCD is disposed on the imaging surface I of the imaging optical system of the present invention. Various optical element insertion / removal mechanisms such as an infrared cut filter may be disposed in the space between the seventh lens L7 and the cover glass CG.

In addition, the imaging optical system of the present invention is configured as a three-dimensional projection type optical system as a projection method in order to ensure the amount of information (visibility) in the peripheral part of a wide visual field.

In the imaging optical system of the present embodiment, it is preferable that the first lens and the fifth lens are glass, and at least the second lens is an aspheric plastic lens.

In the imaging optical system of the present embodiment, the first lens L1 to the fourth lens L4 that constitute the front group realize an imaging optical system that has a field angle of more than 180 degrees and a stereoscopic projection method, and that constitutes the rear group. Various aberrations generated in these wide-angle stereoscopic projection images are effectively corrected by the fifth lens L5 to the seventh lens L7. In the imaging optical system of the present embodiment, since the fifth lens constituting the rear group is glass as described above, the aberration correction effect of the imaging optical system is stabilized while preventing aberration fluctuation due to temperature environment changes. You can increase the sex.

Further, by forming a concave shape on the object side in the vicinity of the optical axis of the second lens L2, the distance (back focus) on the optical axis from the image side surface of the seventh lens L7 to the image surface becomes longer, and the seventh A space for installing various optical element insertion / removal mechanisms such as an infrared cut filter can be secured between the lens L7 and the cover glass CG.

In addition, the imaging optical system of the present embodiment satisfies the following conditional expression.
−23 <f1 / f <−12 (1)
-8 <f2 / f <-5 (2)
2.5 <f5 / f <4.5 (3)
-3.0 <f6 / f <-1.9 (4)
here,
f is the focal length of the entire imaging optical system,
f1 is the focal length of the first lens,
f2 is the focal length of the second lens,
f5 is the focal length of the fifth lens,
f6 is the focal length of the sixth lens.

Conditional expressions (1) to (4) are conditional expressions for enabling both a wide-angle stereoscopic projection image and reduction of various aberrations.

In addition, the imaging optical system of the present embodiment satisfies the following conditional expression.
-0.02 <n6-n5 <0.16 (5)
here,
n5 is the refractive index of the fifth lens with respect to the d-line,
n6 is the refractive index of the sixth lens with respect to the d-line.

In addition, the imaging optical system of the present embodiment satisfies the following conditional expression.
2.4 <f7 / f <3.0 (6)
here,
f7 is the focal length of the seventh lens.

Conditional expression (5) reduces the refractive index difference between the fifth lens and the sixth lens by appropriately selecting the glass materials of the fifth lens L5 and the sixth lens L6, and improves the field curvature aberration generated in the optical system. It is a conditional expression for correcting to. Further, the seventh lens has the configuration of conditional expression (6), which is a conditional expression for further favorably correcting the field curvature aberration generated in the optical system.

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

Next, specific numerical examples of the imaging optical system of the present invention will be shown. 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: lens thickness or air spacing on the optical axis nd: refractive index νd of lens material with respect to d-line : Abbe number of lens material Also, in each example, the surface described with “*” after each surface number is an aspheric surface.

The aspherical shape is expressed by the following equation (I) where z is the optical axis direction, y is the direction orthogonal to the optical axis, K is the conic coefficient, and A4, A6, A8, A10. ).
z = (y ² / r) / [1+ {1− (1 + K) (y / r) ² } ^1/2 ] + A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰ (I)
In the aspheric coefficient, E represents a power of 10, for example, 2.3 × 10 ⁻² is represented as 2.3E-002. The symbols of these specification values are also common in the numerical data of the examples described later.

Example 1
Next, the imaging 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 the imaging optical system according to the first embodiment.

FIG. 2 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) during focusing on an object point at infinity of the imaging optical system according to the first example. FIG. In the figure, Y indicates the image height. The symbols in the aberration diagrams are the same in the examples described later.

As shown in FIG. 1, the imaging optical system has a meniscus first lens L1 having a negative refractive power with a convex surface facing the object side, and a concave surface facing the object side in the vicinity of the optical axis. A second lens L2 having a negative refractive power, 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 having a positive refractive power. It has a lens L5, a biconcave sixth lens L6 having negative refractive power, and a biconvex seventh lens L7 having positive refractive power.

The overall specifications of the imaging optical system of Example 1 are shown below.
f: 1.41 mm
FNO: 2.40
FOV (2ω): 200.00 °
The surface data of the imaging optical system of Example 1 is shown below (unit: mm).

The aspheric data of the imaging optical system of Example 1 is shown below.
Third side
K = 0
A4 = 1.536E-003, A6 = -1.751E-005, A8 = 1.240E-007
4th page
K = 0
A4 = -2.337E-003, A6 = 2.002E-004, A8 = -5.741E-006
5th page
K = 0
A4 = -7.238E-004, A6 = 1.894E-005, A8 = 2.413E-007
6th page
K = 0
A4 = 7.762E-003, A6 = -8.094E-004, A8 = 3.592E-005
7th page
K = 0
A4 = -4.132E-003, A6 = -4.829E-004, A8 = 1.851E-005
8th page
K = 0
A4 = -1.128E-003, A6 = 2.332E-004, A8 = -9.641E-006
12th page
K = 0
A4 = -1.359E-002, A6 = -2.113E-004, A8 = 2.842E-004, A10 = -7.497E-004, A12 = 2.668E-004
Side 13
K = 0
A4 = -1.084E-002, A6 = 2.829E-003, A8 = -1.047E-003, A10 = 1.730E-004, A12 = -6.323E-006
14th page
K = 0
A4 = -1.066E-002, A6 = 1.421E-003, A8 = 8.494E-005, A10 = -4.719E-005, A12 = 5.737E-006
15th page
K = 0
A4 = 3.301E-004, A6 = -4.694E-004, A8 = 1.674E-004, A10 = 2.976E-006, A12 = 2.162E-006

Values corresponding to conditional expressions (1) to (4) of the imaging optical system of Example 1 are shown below.
(1) f1 / f = -16.27
(2) f2 / f = −6.63
(3) f5 / f = 3.00
(4) f6 / f = −2.24
(5) n6-n5 = 0.15
(6) f7 / f = 2.88
In the imaging optical system of Example 1, the first and fifth lenses are made of a glass material, and the other lenses are made of a plastic material.

(Example 2)
Next, an imaging 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 imaging optical system according to the second embodiment.

FIG. 4 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) during focusing on an object point at infinity of the imaging optical system according to the second example. FIG. In the figure, Y indicates the image height.

As shown in FIG. 3, the imaging optical system has a meniscus first lens L1 having a negative refractive power with a convex surface facing the object side, and a concave surface facing the object side in the vicinity of the optical axis. A second lens L2 having a negative refractive power, 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 having a positive refractive power. It has a lens L5, a biconcave sixth lens L6 having negative refractive power, and a biconvex seventh lens L7 having positive refractive power.

The overall specifications of the imaging optical system of Example 2 are shown below.
f: 1.45 mm
FNO: 2.40
FOV (2ω): 200.00 °
The surface data of the imaging optical system of Example 2 is shown below (unit: mm).

Aspherical data of the imaging optical system of Example 2 is shown below.
Third side
K = 0
A4 = 1.130E-003, A6 = -1.039E-005, A8 = 4.932E-008
4th page
K = 0
A4 = -1.643E-003, A6 = 1.228E-004, A8 = -2.519E-006
5th page
K = 0
A4 = -3.266E-004, A6 = 2.495E-005, A8 = -2.675E-007
6th page
K = 0
A4 = 5.975E-003, A6 = -9.557E-004, A8 = 4.175E-005
7th page
K = 0
A4 = -3.140E-003, A6 = -5.222E-004, A8 = 2.730E-005
8th page
K = 0
A4 = -9.075E-003, A6 = 8.271E-005, A8 = 1.933E-006
12th page
K = 0
A4 = -1.405E-002, A6 = 9.911E-004, A8 = 4.864E-004, A10 = -4.359E-004, A12 = 1.209E-004
Side 13
K = 0
A4 = -1.232E-002, A6 = 1.415E-003, A8 = -3.683E-004, A10 = 6.337E-005, A12 = 1.551E-006
14th page
K = 0
A4 = -9.145E-003, A6 = 2.898E-004, A8 = 2.352E-005, A10 = -6.228E-006, A12 = -1.434E-006
15th page
K = 0
A4 = 2.241E-003, A6 = -1.824E-004, A8 = 1.492E-004, A10 = 9.869E-006, A12 = -4.696E-006

Values corresponding to conditional expressions (1) to (4) of the imaging optical system of Example 2 are shown below.
(1) f1 / f = −22.45
(2) f2 / f = −6.82
(3) f5 / f = 3.02
(4) f6 / f = −2.12
(5) n6-n5 = 0.14
(6) f7 / f = 2.72
In the imaging optical system of Example 2, the first and fifth lenses are made of a glass material, and the other lenses are made of a plastic material.

(Example 3)
Next, an imaging 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 imaging optical system according to the third embodiment.

FIG. 6 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion aberration (DT) when the imaging optical system according to the example 3 is focused on an object point at infinity. FIG. In the figure, Y indicates the image height.

As shown in FIG. 5, the imaging optical system has a meniscus first lens L1 having a negative refractive power with a convex surface facing the object side, and a concave surface facing the object side in the vicinity of the optical axis. A second lens L2 having a negative refractive power, 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 having a positive refractive power. It has a lens L5, a biconcave sixth lens L6 having negative refractive power, and a biconvex seventh lens L7 having positive refractive power.

The overall specifications of the imaging optical system of Example 3 are shown below.
f: 1.53 mm
FNO: 2.40
FOV (2ω): 200.00 °
Surface data of the imaging optical system of Example 3 is shown below (unit: mm).

Aspherical data of the imaging optical system of Example 3 is shown below.
Third side
K = 0
A4 = 1.076E-003, A6 = -1.035E-005, A8 = 7.293E-008
4th page
K = 0
A4 = -1.310E-003, A6 = 1.066E-004, A8 = -2.098E-006
5th page
K = 0
A4 = -3.286E-004, A6 = 2.405E-005, A8 = -3.119E-007
6th page
K = 0
A4 = 5.806E-003, A6 = -7.171E-004, A8 = 3.669E-005
7th page
K = 0
A4 = -3.214E-003, A6 = -4.535E-004, A8 = 4.060E-005
8th page
K = 0
A4 = 3.024E-004, A6 = 2.075E-004, A8 = -2.456E-006
12th page
K = 0
A4 = -1.562E-002, A6 = 9.400E-004, A8 = 5.674E-004, A10 = -3.533E-004, A12 = 8.439E-005
Side 13
K = 0
A4 = -1.338E-002, A6 = 1.344E-003, A8 = -3.617E-003, A10 = 6.042E-004, A12 = -3.803E-006
14th page
K = 0
A4 = -9.253E-003, A6 = 4.798E-004, A8 = 8.326E-005, A10 = 9.779E-006, A12 = -1.839E-006
15th page
K = 0
A4 = 6.664E-004, A6 = 1.783E-004, A8 = 2.115E-004, A10 = 2.653E-005, A12 = 2.670E-006

Values corresponding to conditional expressions (1) to (4) of the imaging optical system of Example 3 are shown below.
(1) f1 / f = -20.22
(2) f2 / f = −7.68
(3) f5 / f = 2.87
(4) f6 / f = -1.94
(5) n6-n5 = 0.14
(6) f7 / f = 2.44
In the imaging optical system of Example 3, the first and fifth lenses are made of a glass material, and the other lenses are made of a plastic material.

Example 4
Next, an imaging 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 image pickup optical system according to the fourth embodiment.

FIG. 8 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion aberration (DT) when the imaging optical system according to the example 4 is focused on an object point at infinity. FIG. In the figure, Y indicates the image height.

In this imaging optical system, as shown in FIG. 7, in order from the object side, a meniscus first lens L1 having a negative refractive power with a convex surface facing the object side, and a concave surface facing the object side in the vicinity of the optical axis. A second lens L2 having a negative refractive power, 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 having a positive refractive power. It has a lens L5, a biconcave sixth lens L6 having negative refractive power, and a biconvex seventh lens L7 having positive refractive power.

The overall specifications of the imaging optical system of Example 4 are shown below.
f: 0.98 mm
FNO: 2.20
FOV (2ω): 200.00 °
Surface data of the imaging optical system of Example 4 is shown below (unit: mm).

The aspheric data of the imaging optical system of Example 4 is shown below.
Third side
K = 0
A4 = 3.345E-003, A6 = -6.891E-005, A8 = 7.587E-007
4th page
K = 0
A4 = -4.979E-003, A6 = 5.702E-004, A8 = -2.068E-005
5th page
K = 0
A4 = -1.333E-002, A6 = 1.056E-003, A8 = -3.025E-005
6th page
K = 0
A4 = -9.408E-003, A6 = 4.586E-004, A8 = -7.702E-006
7th page
K = 0
A4 = 3.504E-003, A6 = -4.639E-004, A8 = 1.234E-005
8th page
K = 0
A4 = 5.090E-003, A6 = -2.766E-004, A8 = 2.752E-006
12th page
K = 0
A4 = 1.420E-002, A6 = 5.504E-003, A8 = -6.112E-004
Side 13
K = 0
A4 = -2.883E-002, A6 = 2.488E-002, A8 = -5.881E-003
14th page
K = 0
A4 = -4.781E-002, A6 = 2.324E-002, A8 = -4.097E-003
15th page
K = 0
A4 = 2.329E-002, A6 = -9.893E-004, A8 = 1.709E-003

Values corresponding to conditional expressions (1) to (4) of the imaging optical system of Example 4 are shown below.
(1) f1 / f = -12.88
(2) f2 / f = −5.37
(3) f5 / f = 3.75
(4) f6 / f = -2.50
(5) n6-n5 = −0.02
(6) f7 / f = 2.69
In the imaging optical system of Example 4, the first and fifth lenses are made of a glass material, and the other lenses are made of a plastic material.

(Example 5)
Next, an imaging 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 image pickup optical system according to the fifth embodiment.

FIG. 10 shows (a) spherical aberration (SA), (b) astigmatism (AS), and (c) distortion (DT) during focusing on an object point at infinity of the imaging optical system according to the fifth example. FIG. In the figure, Y indicates the image height.

As shown in FIG. 9, the imaging optical system has a meniscus first lens L1 having a negative refractive power with a convex surface facing the object side, and a concave surface facing the object side in the vicinity of the optical axis. A second lens L2 having a negative refractive power, 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 having a positive refractive power. It has a lens L5, a biconcave sixth lens L6 having negative refractive power, and a biconvex seventh lens L7 having positive refractive power.

The overall specifications of the imaging optical system of Example 5 are shown below.
f: 0.92 mm
FNO: 2.20
FOV (2ω): 200.00 °
Surface data of the imaging optical system of Example 5 is shown below (unit: mm).

The aspheric data of the imaging optical system of Example 5 is shown below.
Third side
K = 0
A4 = 3.291E-003, A6 = -6.832E-005, A8 = 7.455E-007
4th page
K = 0
A4 = -6.794E-003, A6 = 7.016E-004, A8 = -3.043E-005
5th page
K = 0
A4 = -1.318E-002, A6 = 1.050E-003, A8 = -3.091E-005
6th page
K = 0
A4 = -9.549E-003, A6 = 4.430E-004, A8 = -9.188E-006
7th page
K = 0
A4 = 3.530E-003, A6 = -4.726E-004, A8 = 1.185E-005
8th page
K = 0
A4 = 5.178E-003, A6 = -2.727E-004, A8 = 3.212E-006
12th page
K = 0
A4 = 1.391E-002, A6 = 6.171E-003, A8 = 1.022E-003
Side 13
K = 0
A4 = -3.023E-002, A6 = 2.507E-002, A8 = -5.824E-003
14th page
K = 0
A4 = -4.734E-002, A6 = 2.309E-002, A8 = -4.098E-003
15th page
K = 0
A4 = 2.966E-002, A6 = -1.207E-003, A8 = 1.902E-003

Values corresponding to conditional expressions (1) to (4) of the imaging optical system of Example 5 are shown below.
(1) f1 / f = -13.30
(2) f2 / f = −5.63
(3) f5 / f = 4.48
(4) f6 / f = -2.90
(5) n6-n5 = −0.02
(6) f7 / f = 2.83
In the imaging optical system of Example 5, the first and fifth lenses are made of a glass material, and the other lenses are made of a plastic material.

L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens CG Cover glass I Imaging surface S Aperture stop

Claims (6)

A stereoscopic projection imaging optical system having an angle of view exceeding 180 degrees,
From the object side,
A first lens having negative refractive power and having a convex surface facing the object side;
A second lens having negative refractive power;
A third lens having negative refractive power;
A fourth lens having a positive refractive power;
An aperture stop,
A fifth lens having positive refractive power;
A sixth lens having negative refractive power;
A seventh lens having positive refractive power;
Consists of
An imaging optical system characterized by satisfying the following conditional expression:
−23 <f1 / f <−12 (1)
-8 <f2 / f <-5 (2)
2.5 <f5 / f <4.5 (3)
-3.0 <f6 / f <-1.9 (4)
here,
f is the focal length of the entire imaging optical system,
f1 is the focal length of the first lens,
f2 is the focal length of the second lens,
f5 is the focal length of the fifth lens,
f6 is the focal length of the sixth lens. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
-0.02 <n6-n5 <0.16 (5)
here,
n5 is the refractive index of the fifth lens with respect to the d-line,
n6 is the refractive index of the sixth lens with respect to the d-line. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
2.4 <f7 / f <3.0 (6)
here,
f7 is the focal length of the seventh lens.   The imaging optical system according to claim 1, wherein the second lens has a concave surface facing the object side.   The imaging optical system according to any one of claims 1 to 4, wherein a material of the fifth lens is optical glass. The imaging optical system according to any one of claims 1 to 4,
An imaging device comprising: a solid-state imaging device.