JP2010032813A - Optical device for camera mounted in vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure satisfactory image quality and a desired field angle while satisfactorily correcting the distortion of an image formed on an imaging element, trapezoidal distortion, image plane inclination, etc., by a compact configuration of an optical system by appropriately setting the optical system. <P>SOLUTION: The optical system mounted in a vehicle and used to image the inside or the outside of the vehicle includes four lenses and a diaphragm, wherein an optical path passing though the center of the diaphragm so as to be perpendicular to the diaphragm is used as a reference axis, at least one lens face is eccentric to the reference axis at an angle or in parallel, thereby satisfactorily correcting image distortion, trapezoidal distortion, image plane inclination, etc. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention mainly relates to a camera suitable for a camera that images a road surface and the like from an oblique direction using a solid-state imaging device in a vehicle-mounted camera, and more particularly to a vehicle-mounted camera optical system to which a wide-angle optical system for visually recognizing the rear of a vehicle is applied.

  Driving support devices that install an in-vehicle camera rearward on a rear trunk portion of a vehicle and present a captured image of the rear of the vehicle obtained from the in-vehicle camera to the driver are beginning to become widespread.

  FIG. 18 is an optical system configuration diagram of a conventional in-vehicle camera attached to a vehicle, and shows a relationship between an imaging optical system and an imaging element and a relationship between a road surface and the in-vehicle camera.

  In FIG. 18, G0 is an image pickup optical system, and IP is an image plane imaged by the image pickup optical system G0. The image plane includes an image pickup element that converts an image into an electrical signal. M is a camera body, and R is a road surface to be imaged. In the configuration of the imaging optical system G0, a plurality of lenses Ln are arranged to satisfactorily correct the diaphragm SP and various aberrations, and the plurality of lenses Ln pass through the center of the diaphragm SP and perpendicular to the diaphragm SP surface. When the path of the optical path is the reference axis K, it is basically a configuration of a coaxial optical system in which the optical axis matches the reference axis K.

An imaging optical system G0 for a vehicle-mounted camera has been proposed as an ultra-wide-angle optical system having a very wide angle of view in order to obtain a wide range of subject images. (For example, Patent Documents 1, 2, and 3)
In addition, when imaging is performed in a state where the road surface R and the reference axis K of the conventional imaging optical system G0 are not perpendicular to each other and have an inclination, the obtained image has a tilt depending on the obtained image even if the imaging optical system G0 is ideal. Distortion occurs.

The distortion due to this tilt becomes more prominent as the imaging angle of view of the imaging optical system G0 becomes wider, and as an optical system that can prevent the occurrence of distortion due to this tilt, for example, in a projection optical system used in a projector or the like, Various methods for preventing the occurrence of distortion by an optical system using a free-form surface have been proposed. Various methods have also been proposed that can reduce distortion due to tilt by image processing.
JP 2003-195161 A JP 2003-307664 A JP 2004-029262 A

  When distortion due to tilting using image processing is performed, the in-vehicle camera continuously captures images as moving images, and thus the burden on image processing increases. Furthermore, if image processing is performed, the image quality deteriorates accordingly, and it becomes difficult for the driver to correctly grasp the situation behind the vehicle.

  On the other hand, an optical system using a free-form surface can correct distortion due to tilt without deterioration in image quality, but it is difficult to manufacture a lens and a mirror surface that are not rotationally symmetric, and the cost increases. In the case of a vehicle-mounted camera, if the distortion due to tilt is completely removed, the image becomes uncomfortable, making it difficult for the driver to correctly grasp the situation behind the vehicle.

  In addition, a coaxial optical system in which the optical axes of a plurality of lenses are aligned with the reference axis K as described in Patent Documents 1, 2, and 3 is relatively easy to manufacture, but distortion due to tilting can be removed. This makes it difficult for the driver to correctly grasp the situation behind the vehicle.

  In the present invention, in consideration of the problems of these conventional examples, a configuration that takes into account the mass productivity of the optical system is realized, and the optical system that is required from the viewpoint of a vehicle-mounted camera is made compact, and the desired distortion is achieved. It is an object of the present invention to provide an in-vehicle camera optical system that realizes correction with an optical system and ensures good image quality and a desired angle of view.

  In order to achieve the above object, the in-vehicle camera optical system of the present invention is composed of four lenses and a diaphragm, and the path of the optical path that passes through the center of the aperture of the diaphragm and perpendicular to the diaphragm surface. When the reference axis is used, the gist is that at least one lens surface is inclined and / or parallel eccentric with respect to the reference axis.

  Preferably, each lens surface of the four lenses constituting the on-vehicle camera optical system is formed with a rotationally symmetric surface shape with respect to each optical axis.

Preferably, when the angle between the tilted decentered lens surface and the reference axis is θ,
−5 ° ≦ θ ≦ + 5 °
Satisfied.

Preferably, when the amount of deviation between the optical axis of the decentered lens surface and the reference axis is dy,
−1.0 <dy <1.0
Satisfied.

  Preferably, at least one of the lens surfaces of the four lenses has an aspheric surface.

  Preferably, at least one of the four lenses has a plastic lens.

  Preferably, the optical system includes, in order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a stop, and a fourth lens having a positive refractive power. The first lens is a glass lens.

  Preferably, the first lens is a meniscus lens that is convex toward the object side.

Preferably, the lens is an imaging lens intended to form an image on an imaging device that converts an image into an electrical signal, and when the angle of view in the long side direction of the imaging device is ωH,
ωH> 110 °
Satisfied.

  Preferably, the Abbe number with respect to the d-line of the material constituting the first lens is set to 35 or more, and the Abbe number with respect to the d-line of the material constituting the third lens is set to 40 or less. To do.

Preferably, when the focal length of the first lens is f1, and the focal length of the entire system is f,
−6.5 <f1 / f <−3.0
Satisfy the following conditions.

Preferably, when the focal length of the second lens is f2 and the focal length of the entire system is f,
-3.0 <f2 / f <-1.0
Satisfy the following conditions.

Preferably, when the focal length of the third lens is f3, the focal length of the fourth lens is f4, and the focal length of the entire system is f,
2.0 <f3 / f <4.0
1.5 <f4 / f <3.0
The gist is to satisfy the following conditions.

  According to the present invention, it is possible to achieve an in-vehicle camera optical system that achieves desired distortion correction with the optical system and that can obtain a good image quality and a desired angle of view while reducing the size of the optical system.

  Hereinafter, embodiments of an imaging optical system of the present invention and an in-vehicle camera using the same will be described with reference to the drawings.

  FIG. 1 shows a Z-axis (reference axis K) when a three-dimensional coordinate system (X, Y, Z) having a Z-axis as a path (reference axis K) of an optical path that passes perpendicularly to the aperture plane is defined. FIG. 2 is a cross-sectional view taken along the XZ plane passing through the Z axis (reference axis K) in the coordinate system. The X-axis direction corresponds to the long side direction of the image plane IP described later, and the Y-axis direction corresponds to the short side direction. FIG. 3 is a lateral aberration diagram of the image pickup optical system according to the first embodiment. FIG. 4 is an explanatory diagram of a distorted state of the imaging optical system according to the first embodiment. The first embodiment is an imaging optical system having a focal length of 1.22 mm, an F number of 3.0, and a maximum image height from the optical axis to the imaging surface of 2.30 mm.

  FIG. 5 shows the Z axis (reference axis K) when a three-dimensional coordinate system (X, Y, Z) is defined with the path of the optical path (reference axis K) passing perpendicularly to the aperture plane as the Z axis. FIG. 6 is a cross-sectional view taken along the XZ plane passing through the Z axis (reference axis K) in the coordinate system. The X-axis direction corresponds to the long side direction of the image plane IP described later, and the Y-axis direction corresponds to the short side direction. FIG. 7 is a lateral aberration diagram of the image pickup optical system according to the second embodiment. FIG. 8 is an explanatory diagram of a distorted state of the imaging optical system according to the second embodiment. The second embodiment is an imaging optical system having a focal length of 1.56 mm, an F number of 2.9, and a maximum image height on the imaging surface from the optical axis of 2.30 mm.

  FIG. 9 shows the Z axis (reference axis K) when a three-dimensional coordinate system (X, Y, Z) is defined in which the path of the optical path (reference axis K) passing perpendicularly to the aperture plane is the Z axis. FIG. 10 is a cross-sectional view taken along the XZ plane passing through the Z axis (reference axis K) in the coordinate system. The X-axis direction corresponds to the long side direction of the image plane IP described later, and the Y-axis direction corresponds to the short side direction. FIG. 11 is a lateral aberration diagram of the image pickup optical system according to the third embodiment. FIG. 12 is an explanatory diagram of a distorted state of the imaging optical system according to the third embodiment. The third embodiment is an imaging optical system having a focal length of 1.50 mm, an F number of 2.3, and a maximum image height on the imaging surface from the optical axis of 2.30 mm.

  FIG. 13 shows the Z-axis (reference axis K) when a three-dimensional coordinate system (X, Y, Z) is defined with the path of the optical path (reference axis K) passing perpendicularly to the aperture plane as the Z-axis. FIG. 14 is a cross-sectional view taken along the XZ plane passing through the Z axis (reference axis K) in the coordinate system. The X-axis direction corresponds to the long side direction of the image plane IP described later, and the Y-axis direction corresponds to the short side direction. FIG. 15 is a lateral aberration diagram of the image pickup optical system according to the fourth embodiment. FIG. 16 is an explanatory diagram of a distorted state of the imaging optical system according to the fourth embodiment. The fourth embodiment is an imaging optical system having a focal length of 1.50 mm, an F number of 2.7, and a maximum image height on the imaging surface from the optical axis of 2.30 mm.

  In the optical system cross-sectional views of the first to fourth embodiments, the left side is the subject side (object side) and the right side is the image side (imaging plane side). In the optical system sectional view, G0 is an imaging optical system, and a plurality of lenses of a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4, which are meniscus glass lenses convex toward the object side. It is made up of. SP is an aperture stop, which is located in the optical path between the third lens L3 and the fourth lens L4.

  In each embodiment, R is a road surface and is located on the subject side, and the imaging optical system G0 and the reference axis K are attached to the road surface R so as to be inclined in the Y direction. G is a glass block provided by design corresponding to a crystal low-pass filter, a protective glass for protecting the image sensor, an infrared cut filter, and the like. IP is an image plane, on which a photosensitive surface of a solid-state imaging device that converts an image such as a CCD sensor or a CMOS sensor into an electric signal is arranged.

  The lateral aberration diagram displays the d-line (587.56 nm) and the g-line (435.835 nm). As shown in FIG. 17, at a plurality of points F1 to F7 in the imaging region of the image plane IP, the image plane is viewed from the road surface R. This is when the ray is traced to the IP. The evaluation target point F1 is the center point of the image plane IP with respect to the image plane IP, and the evaluation target points F2 to F7 are defined as a two-dimensional coordinate system (x, y) having F1 as the origin. When the diagonal positions of the light receiving areas belonging to the first quadrant and the third quadrant are connected by a straight line, the positions intersecting with the tangent circle connecting the short side direction of the image plane IP with the origin F1 as the center are F2 and F3, and the origin F1 F4 and F5 are the positions that intersect with the tangent circle that connects the long side direction of the image plane IP with the center of F1, and F6 and F7 the positions that intersect with the tangent circle that connects the diagonal position of the image plane with the origin F1 as the center. .

  The distortion shows the projection image itself when the light ray is traced from the road surface R to the image plane IP.

  In this embodiment, the focus from the object at infinity to the object at a short distance is fixed at the pan focus position, and the imaging optical system G0 is not extended, but the imaging optical system G0 is extended to the object side or imaging optical You may carry out by extending | stretching one part among several lenses which comprise the system G0.

  Hereinafter, the configuration and operation of the imaging optical system of the present embodiment will be described.

  In the imaging optical system G0 of the present embodiment, at least one lens surface is tilted eccentrically or parallel eccentrically with respect to the reference axis K. With this configuration, the trapezoidal distortion caused by the inclination of the road surface R and the imaging optical system G0 is appropriately corrected.

  The imaging optical system G0 is in the order from the object side to the image side, and the first lens L1 has a convex object-side surface whose absolute value of the refractive power of the object-side surface is smaller than that of the image-side surface. It consists of a meniscus glass lens whose surface is convex on the object side. Thus, by using the first lens L1 as a glass lens, it is possible to satisfy the severe environmental performance of the in-vehicle camera.

  Further, all surfaces of the plurality of lenses constituting the imaging optical system G0 are formed in a rotationally symmetric surface shape with respect to the optical axis of each lens surface. Thus, by making all the lens surfaces into a rotationally symmetric surface shape, it is possible to reduce the manufacturing difficulty level and to create an accurate optical system, and as a result, the optical performance during mass production is improved.

  In addition, at least one of the imaging optical system G0 of the present embodiment has a plastic lens. The plastic lens is superior to the glass lens in terms of molding stability, weight, and cost, so the lens configuration is used as long as the harsh environmental performance of the in-vehicle camera can be satisfied. Plastic lenses can be easily aspherical at low cost due to molding.

  Taking advantage of the characteristics of the plastic lens that can be easily aspherical, in the present embodiment, at least one of the plurality of lenses constituting the imaging optical system G0 is aspherical to obtain good imaging characteristics. .

  Further, since the plastic lens is molded, the accuracy is high even during mass production, and stable performance can be obtained even if the object side surface and the image side surface constituting the single lens are tilted and parallel decentered. In this embodiment, tilt eccentricity and parallel eccentricity are given in the Y-axis direction with reference to the gate cut position of the plastic lens.

  In addition, regarding the glass lens, in this embodiment, an eccentricity is given by devising the lens abutting portion of the holding frame that holds the lens by using an optical system in which no single lens is given the eccentricity. Specifically, by attaching an adhesive tape to the Y-axis direction part of the lens abutting part and the fitting part and incorporating a glass lens, the Y-axis direction tilt eccentricity and parallel eccentricity of the lens alone are given.

  In this example, the adhesive tape is attached to the holding frame to generate the eccentricity. However, the holding frame may be made of a resin material and may be a holding frame that has the eccentricity in advance when the mold is manufactured.

  Also, the plastic lens may be configured to have an eccentricity by a holding frame that holds the lens, similarly to the glass lens.

  Further, the glass lens may be a molded product like the plastic lens, and the mold itself may be provided with an inclination eccentricity and a parallel eccentricity.

  As described above, each lens has a lens configuration that achieves both a desired eccentric position and aberration correction, and the road surface R such as trapezoidal distortion and the imaging optical system G0 are inclined while maintaining good performance. The various aberrations caused by the desired tilt are corrected satisfactorily.

  Furthermore, the imaging optical system G0 of the present embodiment satisfies the following conditions in order to configure as an optimal on-vehicle camera and to correct various aberrations satisfactorily.

(1-1) The following conditions are preferable for satisfactorily correcting various aberrations.
−5 ° <θ <+ 5 ° (Condition 1)
Here, θ represents an angle formed by the reference axis K and the lens surface that is tilted eccentrically with respect to the reference axis K.

  Conditional expression (1) is an expression that defines the amount of tilt decentering of the plurality of lenses constituting the imaging optical system G0. If tilt decentering is performed exceeding the upper limit value of conditional expression (1), it becomes difficult to correct various aberrations at the peripheral image height of the image plane IP, and further from the viewpoint of compacting the optical system, This is not preferable because it is necessary to provide a large space between them. Similarly, even if the lower limit value is exceeded, it is not preferable as with the upper limit value.

(1-2) The following conditions are preferable for satisfactorily correcting various aberrations.
−0.1 <dy <0.1 (Condition 2)
Here, dy indicates the amount of deviation between the optical axis of the lens surface causing the parallel eccentricity with respect to the reference axis K and the reference axis K.

  Conditional expression (2) is an expression that defines the deviation amounts of the plurality of lenses constituting the imaging optical system G0. If parallel decentering is performed from the reference axis K exceeding the upper limit value of the conditional expression (2), it becomes difficult to correct various aberrations at the peripheral image height of the image plane IP, and further from the viewpoint of compacting the optical system. A large deviation from the axis K is not preferable because it is necessary to provide a wide space on the XY plane as the imaging optical system G0 in which a rotationally symmetric lens shape is arranged. Similarly, even if the lower limit value is exceeded, it is not preferable as with the upper limit value.

(1-3) The following conditions are preferable for the configuration as an optimal on-vehicle camera.
ωH> 110 ° (Condition 3)
Here, ωH represents the angle of view in the long side direction of the image plane IP.

  Conditional expression (3) is an expression relating to the horizontal angle of view of the imaging optical system G0. If the horizontal angle of view narrows beyond the lower limit value of conditional expression (3), the vehicle-mounted camera cannot cover the area that becomes a blind spot from the driver's field of view behind the vehicle, which is not preferable as the vehicle-mounted camera.

More preferably, by setting the numerical range of the conditional expression (3) as in the following conditional expression (3a), it is possible to secure a more preferable shooting range as an in-vehicle camera.
ωH> 115 ° (Condition 3a)
(1-4) The following conditions are preferable for good aberration correction of the optical system.
ν1> 35.0 (Condition 4)
ν3 <40.0 (Condition 5)
Here, ν1 represents the Abbe number of the material of the first lens L1, and ν3 represents the Abbe number of the material of the third lens L3.

  Conditional expression (4) defines the Abbe number of the material of the first lens L1. If the Abbe number decreases beyond the lower limit of conditional expression (4), it is difficult to correct chromatic aberration, particularly lateral chromatic aberration, which is not preferable.

  Conditional expression (5) defines the Abbe number of the material of the third lens L3. If the Abbe number increases beyond the upper limit of conditional expression (5), it is difficult to correct lateral chromatic aberration as in conditional expression (4), which is not preferable.

More preferably, by setting the numerical ranges of the conditional expressions (4) and (5) as the following conditional expressions (4a) and (5a), it is possible to correct the aberration of the optical system, in particular, the chromatic aberration. Correction is possible.
ν1> 40.0 (Condition 4)
ν3 <32.0 (Condition 5)
(1-5) The following conditions are preferable for good aberration correction of the optical system while reducing the size.
−6.5 <f1 / f <−3.0 (Condition 6)
Here, f1 indicates the focal length of the first lens L1, and f indicates the focal length of the imaging lens G0.

  Conditional expression (6) defines the refractive power of the first lens L1. If the refractive power of the first lens L1 exceeds the upper limit value of the conditional expression (6), various aberrations increase and correction becomes difficult. On the other hand, if the lower limit value of conditional expression (6) is exceeded, the refractive power of the first lens L1 becomes weak and the optical system becomes large, which is not preferable for aiming to reduce the size of the optical system.

More preferably, by setting the numerical range of the conditional expression (6) as in the following conditional expression (6a), it is possible to reduce the size of the imaging optical system G0 with higher optical performance while maintaining cost reduction. It becomes possible to form.
−6.2 <f1 / f <−3.5 (Condition 6a)
(1-6) The following conditions are preferable for good aberration correction of the optical system while facilitating manufacture.
−3.0 <f2 / f <−1.0 (Condition 7)
Here, f2 indicates the focal length of the second lens L2, and f indicates the focal length of the imaging optical system G0.

  Conditional expression (7) defines the refractive power of the second lens L2. When the upper limit of conditional expression (7) is exceeded and the refractive power of the second lens L2 becomes strong, the shape of the surface constituting the second lens L2 becomes tight, and the deviation ratio between the vicinity of the optical axis of the lens and the vicinity of the edge becomes large. Since it becomes large and manufacture becomes difficult, it is not preferable. On the other hand, if the lower limit value of conditional expression (7) is exceeded, the refractive power of the second lens L2 will be weakened, making it difficult to secure a preferable photographing range as an in-vehicle camera, and it will be difficult to correct various aberrations. .

More preferably, by setting the numerical range of the conditional expression (7) as in the following conditional expression (7a), it is possible to reduce the size of the imaging optical system G0 with higher optical performance while maintaining the cost reduction. It becomes possible to form.
−2.8 <f2 / f <−1.5 (Condition 7a)
(1-7) The following conditions are preferable for good aberration correction of the optical system while reducing the size.
2.0 <f3 / f <4.0 (Condition 8)
1.5 <f4 / f <3.0 (Condition 9)
Here, f3 indicates the focal length of the third lens L3, f4 indicates the focal length of the fourth lens L4, and f indicates the focal length of the imaging optical system G0.

  Conditional expression (8) defines the refractive power of the third lens L3. If the refractive power of the third lens L3 is increased beyond the lower limit value of the conditional expression (8), various aberrations increase and correction becomes difficult. On the other hand, when the upper limit value of conditional expression (8) is exceeded, the refractive power of the third lens L3 is weakened and the optical system becomes large, which is not preferable for aiming to reduce the size of the optical system.

  Conditional expression (9) defines the refractive power of the fourth lens L4. If the lower limit of conditional expression (9) is exceeded and the refractive power of the fourth lens L4 increases, various aberrations increase and correction becomes difficult. On the other hand, when the lower limit value of conditional expression (9) is exceeded, the refractive power of the fourth lens L4 is weakened and the optical system becomes large, which is not preferable for aiming to reduce the size of the optical system.

More preferably, by setting the numerical ranges of conditional expression (8) and conditional expression (9) as in the following conditional expressions (8a) and (9a), the imaging optical system having a smaller optical size and higher optical performance can be obtained. G0 can be formed.
2.1 <f3 / f <3.6 (Condition 8a)
1.9 <f4 / f <2.4 (Condition 9a)
The numerical data of Numerical Examples 1 to 4 corresponding to Embodiments 1 to 4 are shown below. In each numerical example, i indicates the order of the surfaces from the object side, ri is the radius of curvature of the i-th surface, di is the distance between the i-th surface and the (i + 1) -th surface, and ni and νi are for the d-line, respectively. Refractive index and Abbe number are shown. The two surfaces closest to the image side correspond to a crystal low-pass filter, protective glass, and the like, and are glass blocks G provided by design. The aspherical shape is when the displacement in the optical axis direction at the position of the height H from the optical axis is x with respect to the surface vertex.

It is represented by Where R is a paraxial radius of curvature, A, B, C, D, and E are aspherical coefficients, and K is a conic constant.

Numerical example 1
Unit mm

・ Surface data
i r d n ν
Object surface: ∞ 1000
1: 9.000 0.700 1.729 54.7
2: 3.250 2.513
3 *: 7.855 0.700 1.530 56.2
4 *: 0.957 0.557
5 *: 1.645 2.536 1.585 29.9
6 *: -23.475 0.678
7 (Aperture): ∞ 0.306
8 *: -159.311 1.825 1.530 56.2
9 *: -1.282 0.100
10: ∞ 0.800 1.516 64.1
11: ∞ 2.130
Image plane: ∞
* Aspherical

・ Aspherical surface number K A B C D
3: 0.108449 -1.47047E-02 1.23042E-03 -3.10467E-05 0.00000E-00
4: -1.227204 -2.23468E-02 2.46992E-03 -3.04906E-04 0.00000E-00
5: -0.373666 -9.00445E-03 2.69101E-03 -5.74808E-04 0.00000E-00
6: -0.003557 5.95947E-02 6.02822E-03 6.69641E-03 0.00000E-00
8: -0.000005 -9.42488E-02 2.60627E-01 -3.49066E-01 2.55122E-01
9: -0.695912 1.36204E-02 1.46554E-02 -1.74114E-02 7.78431E-03

・ Eccentric data
dy (mm) θ (degrees)
Object surface: 0.000 15.000
1: 0.222 5.000
2: 0.222 5.000
3: 0.036 1.156
4: 0.036 1.156
5: 0.013 0.990
6: 0.013 0.990
8: 0.000 0.424
9: 0.000 0.424
Image plane: -0.060 -1.123

・ Various focal length 1.22mm
F number 3.0
Diagonal angle of view 133.0 °
Horizontal angle of view (ωH) 118.0 °
Image height 2.3mm
Optical system total length 12.8mm
BF 2.130mm

Numerical example 2
Unit mm

・ Surface data
i r d n ν
Object surface: ∞ 1000
1: 74.869 0.700 1.729 54.7
2: 3.997 2.089
3 *: 119.680 0.700 1.530 56.2
4 *: 1.389 0.774
5 *: 2.576 2.461 1.585 29.9
6 *: -5.011 1.905
7 (Aperture): ∞ 0.359
8 *: 19.867 2.116 1.530 56.2
9 *: -2.113 0.445
10: ∞ 1.200 1.516 64.1
11: ∞ 2.280
Image plane: ∞
* Aspherical

・ Aspherical surface number K A B C D
3: -0.000054 -2.81065E-03 -8.93747E-06 3.80764E-06 0.00000E-00
4: -0.987371 -2.22110E-02 1.43212E-04 9.86381E-06 0.00000E-00
5: -1.666208 3.76482E-04 -1.07876E-04 -3.77328E-06 0.00000E-00
6: -1.287996 4.30013E-03 1.33200E-05 6.20831E-06 0.00000E-00
8: -0.000474 -2.63407E-02 2.69851E-02 -2.37727E-02 1.24498E-02
9: 0.127602 1.68673E-02 2.12467E-03 -8.64006E-04 5.69840E-04

・ Eccentric data
dy (mm) θ (degrees)
Object surface: 0.000 30.000
1: 0.598 0.694
2: 0.598 0.694
3: 0.353 -3.260
4: 0.304 -3.698
5: 0.468 -5.000
6: -0.045 -3.289
8: -0.032 -5.000
9: -0.115 -1.743
Image plane: -0.347 -2.883

-Various data focal length 1.56mm
F number 2.9
Diagonal angle of view 172.6 °
Horizontal angle of view (ωH) 125.2 °
Image height 2.3mm
Optical system total length 15.0mm
BF 2.280mm

Numerical Example 3
Unit mm

・ Surface data
i r d n ν
Object surface: ∞ 1000
1: 12.564 0.700 1.883 40.8
2: 4.310 2.787
3 *: -3.615 0.700 1.530 56.2
4 *: 5.614 0.973
5: 9.580 1.616 1.946 18.0
6: -9.580 1.762
7 (Aperture): ∞ 1.027
8 *: 7.140 1.885 1.530 56.2
9 *: -2.093 0.100
10: ∞ 1.200 1.516 64.1
11: ∞ 2.250
Image plane: ∞
* Aspherical

・ Aspherical surface number K A B C D
3: -36.309673 -3.34179E-03 5.24219E-04 -2.72826E-05 4.94037E-07
4: 3.145569 3.37921E-02 -1.01913E-02 1.83819E-03 -1.22656E-04
8: -4.347978 -2.59443E-02 1.17891E-03 6.90123E-04 2.21338E-04
9: -0.096471 6.08078E-03 2.17358E-03 -1.80014E-03 4.88195E-04

・ Eccentric data
dy (mm) θ (degrees)
Object surface: 0.000 30.000
1: -0.945 3.854
2: -0.081 -0.072
3: 0.150 1.298
4: 0.065 -0.217
5: 0.395 0.678
6: -0.156 1.435
8: -0.002 -0.717
9: 0.021 0.551

-Various data focal length 1.50mm
F number 2.3
Diagonal angle of view 164.2 °
Horizontal angle of view (ωH) 135.6 °
Image height 2.3mm
Optical system total length 15.0mm
BF 2.250mm

Numerical Example 4
Unit mm

・ Surface data
i r d n ν
Object surface: ∞ 1000
1: 19.921 0.700 1.516 64.1
2: 3.500 2.683
3 *: -1.829 0.700 1.530 56.2
4 *: 4.511 0.416
5: 2.699 2.300 1.846 23.8
6: ∞ 0.762
7 (Aperture): ∞ 0.664
8 *: 16.576 1.964 1.530 56.2
9 *: -1.617 0.100
10: ∞ 1.200 1.516 64.1
11: ∞ 2.253
Image plane: ∞
* Aspherical

・ Aspherical surface number K A B C D
3: -9.847877 1.51742E-02 -3.04650E-03 2.93484E-04 -1.12643E-05
4: 0.396006 1.12168E-01 -3.19191E-02 6.88842E-03 -6.14606E-04
8: 0.622705 -7.31563E-02 5.76600E-02 -5.99749E-02 1.79041E-02
9: -0.613332 7.79421E-03 -1.28442E-02 6.26307E-03 -1.63430E-03

・ Eccentric data
dy (mm) θ (degrees)
Object surface: 0.000 30.000
1: 0.174 -0.685
2: 0.174 -0.685
3: 0.034 0.048
4: 0.034 0.048
5: 0.035 0.224
6: 0.035 0.224
8: 0.010 0.045
9: 0.010 0.045

-Various data focal length 1.50mm
F number 2.7
Diagonal angle of view 164.4 °
Horizontal angle of view (ωH) 133.2 °
Image height 2.3mm
Optical system total length 13.8mm
BF 2.253mm

  According to the imaging optical system of the present embodiment described above, it is suitable for an imaging system using a solid-state imaging device, particularly an in-vehicle camera that images a road surface or the like from an oblique direction, and high optical performance is required and there is no sense of incongruity. An imaging optical system suitable for outputting an ultra-wide angle image can be realized.

2 is a sectional view of the optical system in the YZ direction of the imaging optical system according to the first embodiment. FIG. It is an optical system sectional view of the XZ direction of the image pick-up optical system of Embodiment 1. FIG. 3 is an aberration diagram of the imaging optical system according to the first embodiment. It is explanatory drawing of the distortion containing the tilt of the imaging optical system of this Embodiment 1. FIG. It is an optical system sectional view of the YZ direction of the imaging optical system of Embodiment 2. It is an optical system sectional view of the XZ direction of the image pick-up optical system of Embodiment 2. FIG. 6 is an aberration diagram of the image pickup optical system according to the second embodiment. It is explanatory drawing of the distortion containing the tilt of the imaging optical system of this Embodiment 2. FIG. It is an optical system sectional view of the YZ direction of the imaging optical system of this Embodiment 3. It is an optical system sectional view of the XZ direction of the image pick-up optical system of Embodiment 3. FIG. 10 is an aberration diagram of the image pickup optical system according to the third embodiment. It is explanatory drawing of the distortion containing the tilt of the imaging optical system of this Embodiment 3. FIG. It is an optical system sectional view of the YZ direction of the imaging optical system of this Embodiment 4. It is an optical system sectional view of the XZ direction of the imaging optical system of this Embodiment 4. FIG. 10 is an aberration diagram of the image pickup optical system according to the fourth embodiment. It is explanatory drawing of the distortion containing the tilt of the imaging optical system of this Embodiment 4. It is a figure for demonstrating the setting method of the evaluation object points F1-F7 of the aberrational figure of the imaging optical system of this embodiment. It is an optical system block diagram of the conventional vehicle-mounted camera.

Explanation of symbols

G0 Imaging optical system L1 First lens L2 Second lens L3 Third lens L4 Fourth lens SP Aperture stop IP Image surface G Glass block K Reference axis R Road surface (object surface)
Ln Multiple lenses M Camera body

Claims (13)

An in-vehicle camera optical system that images inside or outside of a vehicle,
Consists of four lenses and an aperture,
When the path of the optical path passing through the center of the aperture of the diaphragm and perpendicular to the diaphragm surface is a reference axis, at least one lens surface of the lens is inclined and / or parallel decentered with respect to the reference axis. An optical system for a vehicle-mounted camera.   2. The on-vehicle camera optical system according to claim 1, wherein each of the lens surfaces of the four lenses has a surface shape that is rotationally symmetric with respect to each optical axis. When the angle formed between the lens surface that is decentered and the reference axis is θ,
−5 ° ≦ θ ≦ + 5 °
The on-vehicle camera optical system according to claim 1, wherein: When the amount of deviation between the optical axis of the parallel decentered lens surface and the reference axis is dy,
−1.0 <dy <1.0
The optical system for vehicle-mounted cameras according to claim 1, wherein:   The on-vehicle camera optical system according to claim 1, wherein at least one of the four lens surfaces has an aspheric surface.   The on-vehicle camera optical system according to claim 1, wherein at least one of the four lenses includes a plastic lens.   The optical system includes, in order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a diaphragm, and a fourth lens having a positive refractive power. The on-vehicle camera optical system according to claim 1, wherein the first lens is a glass lens.   The on-vehicle camera optical system according to claim 1, wherein the first lens is a meniscus lens that is convex toward the object side. The optical system is an imaging optical system intended to form an image on an image sensor that converts an image into an electrical signal, and when the angle of view in the long side direction of the image sensor is ωH,
ωH> 110 °
The vehicle-mounted camera optical system according to claim 1, wherein:   2. The Abbe number for the d-line of the material constituting the first lens is set to 35 or more, and the Abbe number for the d-line of the material constituting the third lens is set to 40 or less, respectively. The optical system for vehicle-mounted cameras in any one of -9. When the focal length of the first lens is f1, and the focal length of the entire system is f,
−6.5 <f1 / f <−3.0
The on-vehicle camera optical system according to claim 1, wherein the following condition is satisfied. When the focal length of the second lens is f2, and the focal length of the entire system is f,
-3.0 <f2 / f <-1.0
The on-vehicle camera optical system according to claim 1, wherein the following condition is satisfied. When the focal length of the third lens is f3, the focal length of the fourth lens is f4, and the focal length of the entire system is f,
2.0 <f3 / f <4.0
1.5 <f4 / f <3.0
The vehicle-mounted camera optical system according to claim 1, wherein the following condition is satisfied.