JP2017009973A - Image capturing lens and image capturing device - Google Patents

Abstract

An imaging lens that has a high optical performance compatible with an imaging element whose pixel count has been increasing in recent years and that is small and lightweight and achieves a sufficiently wide angle, and an imaging apparatus using the imaging lens. In order from the object side, a first lens 110 having negative refractive power, a second lens 120 having negative refractive power, a third lens 130 having positive refractive power, an aperture stop 140, The fourth lens 150 has a positive refractive power, the fifth lens 160 has a negative refractive power, the sixth lens 170, and the seventh lens 180. The fourth lens 150 and the fifth lens 160 are bonded together. The lens satisfies the following conditional expression (1). 1 / f4 × ν4 + 1 / f5 × ν5 <0.0127 (1) where f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f is the focal length of the entire imaging lens system, and ν4. Represents the Abbe number of the fourth lens, and ν5 represents the Abbe number of the fifth lens. [Selection] Figure 1

Description

  The present invention relates to a single-focus wide-angle imaging lens used in an imaging apparatus equipped with a solid-state imaging device, such as a monitoring camera and an in-vehicle camera, and an imaging apparatus using the imaging lens.

  Imaging devices such as CCDs and CMOSs that constitute imaging devices such as surveillance cameras and in-vehicle cameras are becoming smaller and higher in pixel year by year, and accordingly, imaging lenses are also required to be smaller and have higher performance. It has become like this.

  In recent years, techniques for recognizing objects and the like have started to spread in surveillance cameras and in-vehicle cameras, and sufficient resolution performance is required for performing recognition processing, and higher performance is required.

  The following Patent Documents 1, 2, and 3 have been proposed as single-focus wide-angle imaging lenses that may be able to meet these demands. However, the single focus lenses described in Patent Documents 1, 2, and 3 are compatible with conventional image sensors, and thus cannot cope with an increase in the number of pixels.

JP 2008-268268 A JP 2009-008867 A JP 2010-054646 A

  The present invention has been made in view of the above points, and an object of the present invention is to have a high optical performance compatible with an imaging element with an increasing number of pixels, and to be sufficiently small and lightweight. An imaging lens that achieves a wide angle and an imaging apparatus using the imaging lens are provided.

  In order to achieve the above object, a lens of the present invention includes, in order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power. And an aperture stop, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, a sixth lens, and a seventh lens, and the fourth lens and the fifth lens are bonded together The lens satisfies the following conditional expression (1).

1 / f4 × ν4 + 1 / f5 × ν5 <0.0127 (1)
Where f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f is the focal length of the entire imaging lens system, ν4 is the Abbe number of the fourth lens, and ν5 is the Abbe number of the fifth lens. Indicates a number.

  Preferably, the first lens has a convex surface facing the object side, the second lens has a concave surface facing the image side, and the third lens has a convex surface facing the object side.

  Preferably, the material constituting the first lens has an Abbe number of 40 or more with respect to the d line of the material constituting the first lens, and an Abbe number of the material constituting the second lens with respect to the d line of 50 or more. The Abbe number with respect to the d line is set to 40 or less, respectively.

  Preferably, the first lens is made of a glass material.

  Preferably, the following conditional expression (2) is satisfied.

2W ≧ 180 ° (2)
However, 2W is the total angle of view of light rays incident on the horizontal image height position on the imaging plane.

  Preferably, the sixth lens and the seventh lens have positive refractive power.

  Preferably, the following conditional expression (3) is satisfied, where Bf is a distance from an image plane side surface of the seventh lens to an imaging plane, and f is a focal length of the entire imaging lens system. To do.

Bf / f ≧ 1.8 (3)
Preferably, the second lens and the seventh lens are made of a resin material, and at least one lens surface has an aspherical shape.

  In order to solve the above-described problems, an imaging apparatus according to the present invention includes any one of the imaging lenses described above and an imaging element that converts an optical image formed by the imaging lens into an electrical signal.

  According to the present invention, there is provided a wide-angle imaging lens having high optical performance by appropriately setting the shape of the lens, the lens material, the shape of the aspherical surface, etc. while being small, light and inexpensive by the seven-lens configuration. Can do. As a result, it is possible to realize a compact, high-resolution wide-angle imaging lens that can be mounted on a surveillance camera or a vehicle-mounted camera, which has an increased number of pixels of an image sensor and a recognition technology, and an imaging apparatus using the same. it can.

It is a figure which shows the basic composition of the imaging lens of embodiment of this invention. 2 is a diagram illustrating a configuration of an imaging lens employed in Example 1. FIG. In Example 1, it is an aberrational figure which shows spherical aberration, distortion aberration, and astigmatism. 6 is a diagram illustrating a configuration of an imaging lens employed in Example 2. FIG. In Example 2, it is an aberrational figure which shows spherical aberration, distortion aberration, and astigmatism. 6 is a diagram illustrating a configuration of an imaging lens employed in Example 3. FIG. In Example 3, it is an aberrational figure which shows spherical aberration, distortion aberration, and astigmatism. 6 is a diagram illustrating a configuration of an imaging lens employed in Example 4. FIG. In Example 4, it is an aberrational figure which shows spherical aberration, a distortion aberration, and astigmatism. 6 is a diagram illustrating a configuration of an imaging lens employed in Example 5. FIG. FIG. 10 is an aberration diagram showing spherical aberration, distortion, and astigmatism in Example 5. 10 is a diagram illustrating a configuration of an imaging lens employed in Example 6. FIG. In Example 6, it is an aberrational figure which shows spherical aberration, a distortion aberration, and astigmatism. 10 is a diagram illustrating a configuration of an imaging lens employed in Example 7. FIG. FIG. 10 is an aberration diagram showing spherical aberration, distortion, and astigmatism in Example 7. It is a figure which shows the relationship between conditional expression (1) and axial chromatic aberration. It is a figure which shows the basic composition of the imaging device of this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the lens configuration of the embodiment in an optical section. In these embodiments, in order from the object side, the first lens 110, the second lens 120, the third lens 130, the aperture stop 140, the fourth lens 150, the fifth lens 160, the sixth lens 170, the seventh lens 180, and the CCD. This is a single-focus imaging lens 100 having a seven-lens configuration in which an imaging device 190 such as (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor device) is arranged.

  The seven lenses shown in FIG. 1 include, in order from the object side, a first lens 110 having a negative refractive power, a second lens 120 having a negative refractive power, a third lens 130 having a positive refractive power, and an aperture. A diaphragm 140, a fourth lens 150 having a positive refractive power, a fifth lens 160 having a negative refractive power, a sixth lens 170 having a positive refractive power, and a seventh lens 180 having a positive refractive power. It is arranged. Moreover, 1 (R1) -15 (R14) of FIG. 1 is a surface number of each component.

  The aperture stop 140 is disposed between the third lens 130 and the fourth lens 150. If the aperture stop 140 is disposed on the image side of the fourth lens 150, the lens system becomes large. Moreover, if it arrange | positions between the 2nd lens 120 and the 3rd lens 130, Bf will become long. Therefore, by disposing the lens between the third lens 130 and the fourth lens 150 described above, it is possible to correct various aberrations and make the lens system compact.

  Occurrence of chromatic aberration can be suppressed by using the fourth lens 150 and the fifth lens 160 as a bonded lens. This makes it possible to obtain good resolution performance.

  The imaging lens 100 is configured to satisfy, for example, conditional expression (1).

1 / f4 × ν4 + 1 / f5 × ν5 <0.0127 (1)
Here, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f is the focal length of the entire imaging lens system, ν4 is the Abbe number of the fourth lens, and ν5 is the Abbe number of the fifth lens.

  Conditional expression (1) is obtained by multiplying the focal lengths and Abbe numbers of the fourth and fifth lenses, which are bonded lenses, and associating the sum of these product values. By satisfying conditional expression (1), it is possible to easily correct axial chromatic aberration. When the upper limit value of conditional expression (1) is exceeded, the power of the fourth lens becomes too large, and it becomes difficult to correct chromatic aberration with the fifth lens.

  For example, the first lens 110 may have a convex surface facing the object side, the second lens 120 may have a concave surface facing the image side, and the third lens 130 may have a convex surface facing the image side.

  Accordingly, the first lens 110 can make light from the object side incident at a wide angle of view by directing the convex surface toward the object side. Similarly, the second lens 120 has a concave surface facing the image side in order to achieve a sufficiently wide angle. In the third lens 130 having positive refractive power, the convex surface is directed toward the object side, so that the sensitivity near the aperture stop 140 is reduced, and the imaging lens 100 is easy to manufacture.

  In addition, the imaging lens 100 has, for example, an Abbe number with respect to the d-line of the material constituting the first lens 110 being 40 or more, an Abbe number with respect to the d-line of the material constituting the second lens 120 being 50 or more, and the third lens 130. The Abbe number with respect to the d-line of the material constituting each is set to 40 or less.

  As a result, the larger the Abbe number with respect to the d-line of the material constituting the first lens 110 and the second lens 120 of the negative lens located closer to the object side than the aperture stop 140, the more the first lens 110 and the second lens 120 generate. The lateral chromatic aberration is reduced. Similarly, the smaller the Abbe number of the material constituting the third lens 130 of the positive lens located on the object side than the aperture stop 140 is, the better the chromatic aberration of magnification can be corrected.

  Further, by forming the first lens 110 with a glass material, it is possible to satisfy severe environmental performance such as physical durability and chemical durability applied to a monitoring camera or a vehicle-mounted camera.

  Further, the imaging lens 100 may be configured to satisfy, for example, the conditional expression (2).

2W ≧ 180 ° (2)
However, 2W is the total angle of view of light rays incident on the horizontal image height position on the imaging plane.
By setting the numerical value range of the conditional expression (2), it is possible to ensure a wider shooting range as a monitoring camera or a vehicle-mounted camera.

  In addition, since the sixth lens 170 and the seventh lens 180 have positive refractive power, the power of each lens constituting the imaging lens 100 can be dispersed and weakened, the sensitivity can be relaxed, and manufacturing can be facilitated. it can.

  Further, the imaging lens 100 may be configured to satisfy, for example, the conditional expression (3).

Bf / f ≧ 1.8 (3)
However, the distance from the image plane side surface of the fifth lens to the imaging plane is Bf, and the focal length of the entire imaging lens system is f.

  Conditional expression (3) relates the ratio of the distance from the image plane side surface of the fifth lens to the imaging plane with respect to the focal length of the entire imaging lens system. If the lower limit value of conditional expression (3) is exceeded, the ratio of Bf to f becomes small, so that an indispensable device such as an IR cut filter or low-pass filter cannot be inserted, and docking with the image sensor becomes difficult.

  In addition, by forming the second lens 120 and the seventh lens 180 from a resin material, it is possible to reduce the weight and cost and to easily manufacture an aspherical shape. Since these lenses are formed in an aspherical shape, aberration correction is easy, and it is possible to obtain good resolution performance while being small.

  The aspherical shape of the lens described in the following numerical examples is positive in the direction from the object side to the image plane side, k is a conical coefficient, A is a fourth-order aspheric coefficient, B Is a 6th-order aspheric coefficient, C is an 8th-order aspheric coefficient, and D is a 10th-order aspheric coefficient. h represents the height of the light beam, c represents the reciprocal of the central radius of curvature, and Z represents the depth from the tangent plane with respect to the surface vertex.

  Examples 1 to 7 according to specific numerical values of the imaging lens 100 are shown below. In the numerical examples of Examples 1 to 7, the focal length, F value, image height, total lens length, back focus, and axial chromatic aberration are as shown in Table 1 below. Similarly, in the numerical examples of Examples 1 to 7, the numerical data of the conditional expressions (1) to (3) are the values described in Table 2 below.

  The basic configuration of the imaging lens 100A in Embodiment 1 is shown in FIG. 2, each numerical data (setting value) is shown in Tables 3 and 4, and the aberration diagram showing spherical aberration, distortion aberration, and astigmatism is shown in FIG. Respectively.

  The imaging lens 100B according to the first embodiment is designed when 1 / (f4 × ν4) + 1 / (f5 × ν5) = − 0.00004.

  As shown in FIG. 2, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape with a concave surface facing the image side, and the third lens 130 has a convex surface facing the object side. The fourth lens 150 arranged on the image side of the aperture stop 140 is a biconvex shape with the convex surface facing the image side, the fifth lens 160 is the meniscus shape with the convex surface facing the image side, and the sixth lens 170 is The biconvex shape with the convex surface facing the image side, and the seventh lens 180 has a meniscus shape with the convex surface facing the image side. The second lens 120 has an aspheric surface on both sides, and the seventh lens 160 has an aspheric surface on one side.

  Further, as shown in FIG. 2, the distance between the R1 surface 1 and the R2 surface 2 that is the thickness of the first lens 110 is D1, and the distance from the R2 surface 2 of the first lens 110 to the R3 surface 3 of the second lens 120. D2, the distance between the R3 surface 3 and the R4 surface 4 that is the thickness of the second lens 120, D3, the distance between the R4 surface 4 of the second lens 120 and the R5 surface 5 of the third lens 130, D4, The distance between the R5 surface 5 and the R6 surface 6 having a thickness of 130 is D5, the distance between the R6 surface 6 of the third lens 130 and the surface 7 of the aperture stop 140 is D6, the surface 7 of the aperture stop 140 and the fourth lens 150. The distance between the R7 surface 8 is D7, the distance between the R7 surface 8 and the R8 surface 9 that is the thickness of the fourth lens 150 is D8, and the distance between the R8 surface 9 and the R9 surface 10 that is the thickness of the fifth lens 160 is D9, the R9 surface 10 of the fifth lens 160 and the R10 surface 1 of the sixth lens 170. The distance between the R10 surface 11 and the R11 surface 12 that is the thickness of the sixth lens 170 is D11, the distance between the R11 surface 12 and the R12 surface 13 that is the thickness of the seventh lens 180 is D12, The distance from the R12 surface 13 of the lens 180 to the image sensor (imaging surface) 190 is D13. In the following Examples 2 to 7, R1 surface 1 to R12 surface 13 and D1 to D13 mean the same distance.

Table 3 shows the stop corresponding to each surface number of the imaging lens 100A in Example 1, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. In Table 3, the surface with * in the surface number indicates an aspherical shape. Table 4 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 1>

  3A shows a spherical aberration (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, 656.3 nm from the left) and FIG. 3B shows an astigmatism (solid line: left) in Example 1. 35.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm sagittal rays, dotted line: 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm tangential rays from the left), Figure 3 (C) Distortion aberrations (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, and 656.3 nm overlap) are shown. 3B and 3C, the vertical axis represents the half field angle ω. In FIG. 3B, the solid line S represents the sagittal image plane value, and the broken line T represents the tangential image plane value. (The same applies to FIGS. 5, 7, 9, 11, 13, and 15).

  The basic configuration of the imaging lens 100B in Embodiment 2 is shown in FIG. 4, each numerical data (setting value) is shown in Tables 5 and 6, and the aberration diagram showing spherical aberration, distortion aberration, and astigmatism is shown in FIG. Respectively.

  The imaging lens 100B according to the second embodiment is designed when 1 / (f4 × ν4) + 1 / (f5 × ν5) = 0.0002.

  As shown in FIG. 4, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape with a concave surface facing the image side, and the third lens 130 has a convex surface facing the object side. The fourth lens 150 arranged on the image side of the aperture stop 140 is a biconvex shape with the convex surface facing the image side, the fifth lens 160 is the meniscus shape with the convex surface facing the image side, and the sixth lens 170 is The biconvex shape with the convex surface facing the image side, and the seventh lens 180 has a meniscus shape with the convex surface facing the image side. The second lens 120 has an aspheric surface on both sides, and the seventh lens 160 has an aspheric surface on one side.

Table 5 shows the stop corresponding to each surface number of the imaging lens 100B in Example 2, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. In Table 5, the surface numbered with * indicates that the surface is aspherical. Table 6 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 2>

  5A is a spherical aberration (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, 656.3 nm from the left) and FIG. 5B is an astigmatism (solid line: left) in Example 2. (5) to 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm sagittal rays, dotted line: 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm tangential rays from the left). Distortion aberrations (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, and 656.3 nm overlap) are shown.

  The basic configuration of the imaging lens 100C according to the third embodiment is shown in FIG. 6, each numerical data (setting value) is shown in Tables 7 and 8, and the aberration diagram showing spherical aberration, distortion, and astigmatism is shown in FIG. Respectively.

  The imaging lens 100C according to the third embodiment is designed in the case where 1 / (f4 × ν4) + 1 / (f5 × ν5) = 0.0072.

  As shown in FIG. 6, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape with a concave surface facing the image side, and the third lens 130 has a convex surface facing the object side. The fourth lens 150 arranged on the image side of the aperture stop 140 is a biconvex shape with the convex surface facing the image side, the fifth lens 160 is the meniscus shape with the convex surface facing the image side, and the sixth lens 170 is The biconvex shape with the convex surface facing the image side, and the seventh lens 180 has a meniscus shape with the convex surface facing the image side. The second lens 120 has an aspheric surface on both sides, and the seventh lens 160 has an aspheric surface on one side.

Table 7 shows the stop corresponding to each surface number of the imaging lens 100C in Example 3, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. In Table 7, the surface numbered with * indicates that the surface is aspherical. Table 8 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 3>

  7A is a spherical aberration (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, 656.3 nm from the left), and FIG. 7B is an astigmatism (solid line: left). To 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm sagittal rays, dotted line: from the left 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm tangential rays), Fig. 7 (C) Distortion aberrations (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, and 656.3 nm overlap) are shown.

  The basic configuration of the imaging lens 100D according to the fourth embodiment is shown in FIG. 8. Each numerical data (setting value) is shown in Tables 9 and 10, and the aberration diagrams showing spherical aberration, distortion, and astigmatism are shown in FIG. Respectively.

  The imaging lens 100D in Example 4 is designed when 1 / (f4 × ν4) + 1 / (f5 × ν5) = 0.0107.

  As shown in FIG. 8, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape with a concave surface facing the image side, and the third lens 130 has a convex surface facing the object side. The fourth lens 150 arranged on the image side of the aperture stop 140 is a biconvex shape with the convex surface facing the image side, the fifth lens 160 is the meniscus shape with the convex surface facing the image side, and the sixth lens 170 is The biconvex shape with the convex surface facing the image side, and the seventh lens 180 has a meniscus shape with the convex surface facing the image side. The second lens 120 has an aspheric surface on both sides, and the seventh lens 160 has an aspheric surface on one side.

Table 9 shows the stop corresponding to each surface number of the imaging lens 100D in Example 4, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. In Table 9, the surface numbered with * indicates that the surface is aspherical. Table 10 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 4>

  FIG. 9 shows the spherical aberration (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, 656.3 nm from the left) and FIG. 9B shows the astigmatism (solid line: left) in Example 4. 95.8G, 486.1nm, 546.1nm, 587.6nm, 656.3nm sagittal rays, dotted line: from the left 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm tangential rays), Figure 9 (C) Distortion aberrations (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, and 656.3 nm overlap) are shown.

  The basic configuration of the imaging lens 100E according to Embodiment 5 is shown in FIG. 10, each numerical data (setting value) is shown in Tables 11 and 12, and the aberration diagram showing spherical aberration, distortion, and astigmatism is shown in FIG. Respectively.

  The imaging lens 100E in Example 5 is designed in the case of 1 / (f4 × ν4) + 1 / (f5 × ν5) = 0.0118.

  As shown in FIG. 10, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape with a concave surface facing the image side, and the third lens 130 has a convex surface facing the object side. The fourth lens 150 arranged on the image side of the aperture stop 140 is a biconvex shape with the convex surface facing the image side, the fifth lens 160 is the meniscus shape with the convex surface facing the image side, and the sixth lens 170 is The biconvex shape with the convex surface facing the image side, and the seventh lens 180 has a meniscus shape with the convex surface facing the image side. The second lens 120 has an aspheric surface on both sides, and the seventh lens 160 has an aspheric surface on one side.

Table 11 shows the stop corresponding to each surface number of the imaging lens 100E in Example 5, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. In Table 11, a surface numbered with * indicates that it has an aspherical shape. Table 12 shows the aspheric coefficient of the predetermined surface.
<Numerical example 5>

  11A is a spherical aberration (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, 656.3 nm from the left), and FIG. 11B is an astigmatism (solid line: left) in Example 5. 115.8C, 486.1nm, 546.1nm, 587.6nm, 656.3nm sagittal rays, dotted line: 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm tangential rays from the left), Figure 11 (C) Distortion aberrations (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, and 656.3 nm overlap) are shown.

  The basic configuration of the imaging lens 100F according to the sixth embodiment is shown in FIG. 12, each numerical data (setting value) is shown in Table 13 and Table 14, and the aberration diagram showing spherical aberration, distortion, and astigmatism is shown in FIG. Respectively.

  The imaging lens 100F in Example 6 is designed when 1 / (f4 × ν4) + 1 / (f5 × ν5) = 0.0124.

  As shown in FIG. 12, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape with a concave surface facing the image side, and the third lens 130 has a convex surface facing the object side. The fourth lens 150 arranged on the image side of the aperture stop 140 is a biconvex shape with the convex surface facing the image side, the fifth lens 160 is the meniscus shape with the convex surface facing the image side, and the sixth lens 170 is The biconvex shape with the convex surface facing the image side, and the seventh lens 180 has a meniscus shape with the convex surface facing the image side. The second lens 120 has an aspheric surface on both sides, and the seventh lens 160 has an aspheric surface on one side.

Table 13 shows the diaphragm corresponding to each surface number of the imaging lens 100F in Example 6, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. In Table 13, the surface with * in the surface number indicates an aspherical shape. Table 14 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 6>

  13A is a spherical aberration (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, 656.3 nm from the left) and FIG. 13B is an astigmatism (solid line: left) in Example 6. To 135.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm sagittal rays, dotted line: from the left 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm tangential rays), Fig. 13 (C) Distortion aberrations (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, and 656.3 nm overlap) are shown.

The basic configuration of the imaging lens 100G in the seventh embodiment is shown in FIG. 14, each numerical data (setting value) is shown in Tables 15 and 16, and the aberration diagram showing spherical aberration, distortion, and astigmatism is shown in FIG. Respectively.
The imaging lens 100G in Example 7 is designed in the case where 1 / (f4 × ν4) + 1 / (f5 × ν5) = 0.0126.

  As shown in FIG. 14, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape with a concave surface facing the image side, and the third lens 130 has a convex surface facing the object side. The fourth lens 150 arranged on the image side of the aperture stop 140 is a biconvex shape with the convex surface facing the image side, the fifth lens 160 is the meniscus shape with the convex surface facing the image side, and the sixth lens 170 is The biconvex shape with the convex surface facing the image side, and the seventh lens 180 has a meniscus shape with the convex surface facing the image side. The second lens 120 has an aspheric surface on both sides, and the seventh lens 160 has an aspheric surface on one side.

Table 15 shows the stop corresponding to each surface number of the imaging lens 100G in Example 7, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. In Table 15, the surface numbered with * indicates that the surface is aspherical. Table 16 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 7>

  15A is a spherical aberration (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, 656.3 nm from the left) and FIG. 15B is an astigmatism (solid line: left) in Example 7. To 155.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm sagittal rays, dotted line: 435.8nm, 486.1nm, 546.1nm, 587.6nm, 656.3nm tangential rays from the left), Fig. 15 (C) Distortion aberrations (435.8 nm, 486.1 nm, 546.1 nm, 587.6 nm, and 656.3 nm overlap) are shown.

  FIG. 16 shows the relationship between conditional expression (1) and axial chromatic aberration in Examples 1 to 7. Where f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f is the focal length of the entire imaging lens system, ν4 is the Abbe number of the fourth lens, and ν5 is the Abbe number of the fifth lens. As can be seen from FIG. 16, the axial chromatic aberration decreases as the value of 1 / (f4 × ν4) + 1 / (f5 × ν5) in conditional expression (1) decreases. 1 / f4 × ν4 + 1 / f5 × ν5 <0.0127 must be satisfied in order to fall below the axial chromatic aberration of 0.13 mm, which is an index of resolution performance.

  However, as the value of 1 / (f4 × ν4) + 1 / (f5 × ν5) decreases, the radius of curvature R of the fourth lens 150 and the fifth lens 160 decreases, and the processed shape becomes difficult.

  Further, according to the imaging lens of the present embodiment, it is suitable for a camera or the like equipped with an imaging device, and an imaging device including a wide-angle imaging lens having high optical performance while being small, light, and inexpensive can be realized.

  FIG. 17 shows a cross-sectional view of an embodiment of an imaging apparatus using the imaging lens 100 according to the present invention. The imaging lens 100 and the imaging element 210 such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor device) are defined and held by a housing 220. At this time, the imaging surface 190 of the imaging lens 100 is disposed so as to coincide with the light receiving surface of the imaging element 210.

  The subject image captured by the imaging lens 100 and formed on the light receiving surface of the imaging element 210 is converted into an electrical signal by the photoelectric conversion function of the imaging element 210 and output from the imaging apparatus 200 as an image signal.

  The imaging lens 100 as described above is small, thin, lightweight, and can be compact in mounting space, and thus is suitable for imaging devices for various applications. In addition, although it is a wide-angle imaging lens, it can correct the occurrence of various aberrations well, form a subject image with high optical performance on the light receiving surface of the imaging device 210, and output an image signal with excellent visibility. Since it has high weather resistance that can cope with the heat generation of the electric system, it is possible to realize an imaging device that has a superior advantage particularly in surveillance cameras and in-vehicle cameras that require a sealed structure.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention.

100, 100A to 100G ... Imaging lens 110 ... First lens 120 ... Second lens 130 ... Third lens 140 ... Aperture stop 150 ... Fourth lens 160 ... Fifth Lens 170 ... Sixth lens 180 ... Seventh lens 190 ... Imaging surface 200 ... Imaging device 210 ... Imaging element 220 ... Housing

Claims (9)

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, an aperture stop, and a fourth lens having a positive refractive power. It is composed of a lens, a fifth lens having negative refractive power, a sixth lens, and a seventh lens. The fourth lens and the fifth lens are used as a cemented lens, and the following conditional expression (1) is satisfied. A characteristic imaging lens.
1 / f4 × ν4 + 1 / f5 × ν5 <0.0127 (1)
Where f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f is the focal length of the entire imaging lens system, ν4 is the Abbe number of the fourth lens, and ν5 is the Abbe number of the fifth lens. Indicates a number.   The imaging lens according to claim 1, wherein the first lens has a convex surface facing the object side, the second lens has a concave surface facing the image side, and the third lens has a convex surface facing the object side.   The Abbe number for the d-line of the material constituting the first lens is 40 or more, the Abbe number for the d-line of the material constituting the second lens is 50 or more, and the d-line of the material constituting the third lens is The imaging lens according to claim 1, wherein the Abbe number is set to 40 or less.   The imaging lens according to claim 1, wherein the first lens is made of a glass material. The imaging lens according to claim 1, wherein the following conditional expression (2) is satisfied.
2W ≧ 180 ° (2)
However, 2W is the total angle of view of light rays incident on the horizontal image height position on the imaging plane.   The imaging lens according to claim 1, wherein the sixth lens and the seventh lens have positive refractive power. The following conditional expression (3) is satisfied, where Bf is a distance from an image plane side surface of the seventh lens to an imaging plane, and f is a focal length of the entire imaging lens system. The imaging lens according to any one of 1 to 6.
Bf / f ≧ 1.8 (3)   The imaging lens according to claim 1, wherein the second lens and the seventh lens are formed of a resin material, and at least one lens surface has an aspherical shape.   An imaging apparatus comprising: the imaging lens according to claim 1; and an imaging element that converts an optical image formed through the imaging lens into an electrical signal.