JP6097426B2 - Cemented lens - Google Patents

Description

The present invention relates to a cemented lens mounted on an imaging lens.

An imaging lens equipped with a cemented lens in order to correct various aberrations such as chromatic aberration with a small number of lenses is known. The imaging lens described in Patent Document 1 includes, in order from the object side to the image side, a first lens having negative power, a second lens having negative power, a third lens having positive power, and a positive lens. The fourth lens is provided with the following power, and the fourth lens is a cemented lens. In the same document, the cemented surface of the two lenses constituting the fourth lens, that is, the image side lens surface of the object side lens and the object side lens surface of the image side lens constituting the fourth lens are both aspherical. It is said that.

JP 2006-284620 A

The cemented lens is configured by joining two lenses (an object side lens and an image side lens) with an acrylic resin adhesive. In addition, in a cemented lens, a resin adhesive layer formed between two lenses by a resin adhesive is required to be formed as thin as possible. Generally, a thickness dimension of a resin adhesive layer is 5 to 5 mm. 10 μm. This is because if the resin adhesive layer is thick, there is an adverse effect that the curvature of field on the tangential surface shifts to the plus side as compared with the simulation of the optical characteristics of the imaging lens at the time of design.

Here, in order to correct various aberrations better, it is conceivable that the image side lens surface of the object lens serving as the cemented surface and the object side lens surface of the image side lens have different aspherical shapes. . However, if the resin adhesive layer is made thin when the shapes of the bonding surfaces are different from each other, the bonding surfaces are brought into contact with each other during the bonding operation, and the risk of causing damage to each bonding surface increases. In addition, if the interval between the joint surfaces of each lens is narrowed in order to make the resin adhesive layer thin, the resin adhesive does not enter between these joint surfaces, and bubbles remain between the object side lens and the image side lens. May end up.

In view of such a point, an object of the present invention is to provide an easy-to-manufacture cemented lens that can be used in a high-resolution imaging lens and can correct various aberrations better.

In order to solve the above problems, a cemented lens of the present invention is a cemented lens including an object side lens having a negative power and an image side lens having a positive power. The cemented lens has a positive power and the negative power. A resin adhesive layer that bonds the object side lens and the image side lens having the positive power is provided, and both lens surfaces of the object side lens having the negative power are aspherical, and the positive side lens surface on the image side lens comprising a power Ri aspherical der both surfaces, the joining surface between the object side lens comprising the negative power the resin adhesive layer, and the image side lens comprising the positive power The bonding surface with the resin adhesive layer has a different aspherical shape, the thickness dimension of the resin adhesive layer on the optical axis is D, and the negative direction in the direction orthogonal to the optical axis. With the power of The sag amount of the cemented surface of the object side lens having the negative power at the height H at the effective diameter of the cemented surface of the body side lens is Sg1H, and the cemented surface of the image side lens having the positive power at the height H. When the sag amount is Sg2H, the following conditional expressions (1) , (2), and (3) are satisfied.
20 μm ≦ D (1)
Sg1H <Sg2H (2)
D ≦ 100μm (3)

According to the present invention, the cemented surface of the object side lens having negative power and the resin adhesive layer, which is the cemented surface of the two lenses constituting the cemented lens, and the image side lens having positive power, The joint surface with the resin adhesive layer has a different aspherical shape . As a result, it becomes easy to correct various aberrations such as chromatic aberration using the cemented lens, so that the resolution of the imaging lens can be increased. Further, since the conditional expression (1) and the conditional expression (2) are satisfied, the cemented surface of the object side lens having negative power and the cemented surface of the image side lens having positive power , which are different aspherical shapes from each other, are satisfied. The thickness dimension of the resin adhesive layer between them, that is, the interval between the cemented surfaces of the two lenses constituting the cemented lens can be increased. Therefore, it is possible to prevent or suppress the bonding surfaces from being brought into contact with each other during the bonding operation of bonding the two lenses and causing damage to each bonding surface. Moreover, since the space | interval of a joining surface is wide, it can prevent that a resin adhesive agent wraps around between joining surfaces, and a bubble remains between two lenses. Therefore, it becomes easy to manufacture the cemented lens. Furthermore, the imaging lens is designed such that the interval on the optical axis between the cemented surface of the object-side lens having negative power and the cemented surface of the image-side lens having positive power constituting the cemented lens is set to 20 μm to 100 μm in advance. Therefore, it is possible to design in consideration of the shift of the field curvature on the tangential surface to the plus side, and the shift of the field curvature to the plus side can be suppressed by the design. The sag amount is the lens surface from the reference surface at the height H at the effective diameter in the direction orthogonal to the optical axis when a plane that includes the intersection of the lens surface and the optical axis and is orthogonal to the optical axis is used as the reference surface. Is the distance in the optical axis direction. Furthermore, with the imaging lens of the present invention, it is possible to prevent or suppress the occurrence of a focus shift between shooting using visible light and shooting using near infrared rays. Therefore, for example, it can be mounted on an imaging apparatus that performs imaging using near infrared rays including a wavelength of 850 nm, such as light in a band of 800 nm to 1100 nm, and imaging using visible light. Note that the visible light is light having a wavelength in the range of 400 nm to less than 700 nm.

In the present invention, it is desirable to satisfy the following conditional expression (3).
D ≦ 100μm (3)

In this way, the shift to the plus side of the curvature of field on the tangential surface due to the increase in the distance between the object side lens and the image side lens can be kept within a correctionable range.

In the present invention, it is desirable that the following conditional expression (4) is satisfied, where f is the focal length of the entire lens system and Rs is the radius of curvature of the image side lens surface of the object side lens.
0.9 ≦ Rs / f ≦ 1.3 (4)

If the lower limit value of conditional expression (4) is not reached, the curvature of the cemented surface increases, so that it is not easy to join the image side lens, and the workability of joining the cemented lens decreases. If the upper limit value of conditional expression (4) is exceeded, it will be difficult to correct chromatic aberration.

In the present invention, when the focal length of the entire lens system is f, the focal length of the object side lens is f41, and the focal length of the image side lens is f42, it is preferable that the following conditional expression (5) is satisfied.
−3.0 ≦ (f41 / f42) /f≦−1.5 (5)

If the lower limit of conditional expression (5) is not reached, it will be difficult to balance axial chromatic aberration and lateral chromatic aberration, leading to a reduction in resolution in the peripheral portion of the image. If the upper limit value of conditional expression (5) is exceeded, it will be difficult to correct chromatic aberration. Here, the upper limit value and the lower limit value of the conditional expression (5) are values that take into account axial chromatic aberration and lateral chromatic aberration when using near-infrared light including a wavelength of 850 nm for imaging, and use visible light. In this case, the lower limit value is desirably −2.5.

In the present invention, in order to make the imaging lens a wide angle lens, the first lens is a meniscus lens having a convex shape on the object side lens surface, and the image side lens surface of the second lens has a concave shape. The third lens has a convex object-side lens surface, the radius of curvature of the object-side lens surface of the third lens is R31, and the radius of curvature of the image-side lens surface of the third lens is R32. It is preferable that the following conditional expression (6) is satisfied.
R31 ≦ | R32 | (6)

In this case, the imaging lens of the present invention can be a wide-angle lens having a half angle of view of 80 ° or more.

In the present invention, in order to satisfactorily correct chromatic aberration, the first lens, the second lens, and the image side lens have an Abbe number of 40 or more, preferably 56 or more, and the third lens The object-side lens preferably has an Abbe number of 31 or less.

Next, an image pickup apparatus according to the present invention includes the above-described image pickup lens and an image pickup element disposed at a focal position of the image pickup lens.

According to the present invention, since it is possible to increase the resolution of the imaging lens, it is possible to increase the resolution of the imaging apparatus by mounting an imaging element having a large number of pixels.

An imaging device of the present invention includes the imaging lens described above, an imaging element disposed at a focal position of the imaging lens, and an optical filter that transmits near-infrared rays and visible rays in a band including a wavelength of 850 nm. The optical filter is disposed on the object side of the imaging lens or between the imaging lens and the imaging element.

According to the present invention, in the imaging lens, it is prevented or suppressed that a focus shift occurs between photographing using visible light and photographing using light in a predetermined band in the infrared region. Therefore, it is easy to configure an imaging apparatus that performs imaging using near infrared rays and visible rays using an imaging lens.

According to the present invention, since the cemented surfaces of the two lenses constituting the cemented lens have different aspherical shapes, it becomes easy to correct various aberrations such as chromatic aberration using the cemented lens, and the imaging lens. The resolution can be increased. Further, since the conditional expression (1) and the conditional expression (2) are satisfied, it is possible to prevent the bonding surfaces from being brought into contact with each other during the bonding operation for bonding the two lenses, or to damage each bonding surface. Can be suppressed. Moreover, it is easy for the resin adhesive to go around between the joint surfaces, and it is possible to prevent bubbles from remaining between the two lenses. Therefore, it becomes easy to manufacture the cemented lens. Furthermore, the imaging lens can be designed by setting the distance between the image side lens surface of the object side lens constituting the cemented lens and the object side lens surface of the image side lens on the optical axis in advance to 20 μm or more. It is possible to suppress the shift of the field curvature in the plane to the plus side. Further, according to the present invention, it is possible to prevent or suppress the occurrence of a focus shift between shooting using visible light and shooting using near infrared rays.

It is a block diagram of the imaging lens of Example 1 to which the present invention is applied. It is explanatory drawing of the amount of sag. FIG. 2 is a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens in FIG. 1. It is a spherical aberration diagram of the imaging lens of FIG. It is a block diagram of the imaging lens of Example 2 to which the present invention is applied. FIG. 6 is a spherical difference diagram, lateral aberration diagram, field curvature diagram, and distortion diagram of the imaging lens of FIG. 5. FIG. 6 is a spherical aberration diagram of the imaging lens of FIG. 5. It is a block diagram of the imaging lens of Example 3 to which the present invention is applied. FIG. 9 is a spherical difference diagram, lateral aberration diagram, field curvature diagram, and distortion diagram of the imaging lens of FIG. 8. FIG. 9 is a spherical aberration diagram of the imaging lens of FIG. 8. It is a block diagram of the imaging lens of Example 4 to which the present invention is applied. FIG. 12 is a spherical difference diagram, lateral aberration diagram, field curvature diagram, and distortion diagram of the imaging lens of FIG. 11. FIG. 12 is a spherical aberration diagram of the imaging lens of FIG. 11. It is a block diagram of the imaging lens of Example 5 to which the present invention is applied. FIG. 15 is a spherical difference diagram, lateral aberration diagram, field curvature diagram, and distortion diagram of the imaging lens of FIG. 14. FIG. 15 is a spherical aberration diagram of the imaging lens of FIG. 14. It is explanatory drawing of the imaging device carrying an imaging lens. 2 is a configuration diagram of an imaging lens of Reference Example 1. FIG. FIG. 19 is a spherical difference diagram, lateral aberration diagram, field curvature diagram, and distortion diagram of the imaging lens of FIG. 18. 6 is a configuration diagram of an imaging lens of Reference Example 2. FIG. FIG. 21 is a spherical difference diagram, lateral aberration diagram, field curvature diagram, and distortion diagram of the imaging lens in FIG. 20. 10 is a configuration diagram of an imaging lens of Reference Example 3. FIG. It is a spherical-difference figure, a lateral aberration figure, a field curvature figure, and a distortion aberration figure of the imaging lens of FIG.

An imaging lens in which the cemented lens of the present invention is applied as a fourth lens will be described below with reference to the drawings.

Example 1
FIG. 1 is a configuration diagram (ray diagram) of the imaging lens of the first embodiment. As shown in FIG. 1, the imaging lens 10 of this example includes, in order from the object side to the image side, a first lens 11 having a negative power, a second lens 12 having a negative power, and a positive power. It consists of a third lens 13 and a fourth lens 14 with positive power. A diaphragm 15 is disposed between the third lens 13 and the fourth lens 14, and a plate glass 16 is disposed on the image side of the fourth lens 14. The imaging plane I1 is located away from the plate glass 16. The fourth lens 14 is a cemented lens including an object side lens 17 having negative power and an image side lens 18 having positive power. The object side lens 17 and the image side lens 18 are bonded by a resin adhesive, and a resin adhesive layer B <b> 1 is formed between the object side lens 17 and the image side lens 18.

The first lens 11 is a meniscus lens in which the object side lens surface 11a protrudes toward the object side. The object side lens surface 11a and the image side lens surface 11b of the first lens 11 each have a positive curvature.

In the second lens 12, the object side lens surface 12a has a negative curvature, and the image side lens surface 12b has a positive curvature. Accordingly, the object side lens surface 12a has a concave curved surface portion that is recessed toward the image side toward the optical axis L1, and the image side lens surface 12b is a concave surface that is recessed toward the object side toward the optical axis L1. It has a part. The object side lens surface 12a and the image side lens surface 12b are aspherical.

In the third lens 13, the object side lens surface 13a has a positive curvature, and the image side lens surface 13b has a negative curvature. Therefore, the object side lens surface 13a includes a convex curved surface portion that protrudes toward the object side toward the optical axis L1, and the image side lens surface 13b protrudes toward the image side toward the optical axis L1. It has a part. The object side lens surface 13a and the image side lens surface 13b of the third lens 13 are aspherical.

The object side lens 17 of the fourth lens 14 has an object side lens surface 17a having a positive curvature and an image side lens surface 17b having a positive curvature. Accordingly, the object side lens surface 17a includes a convex curved surface portion that protrudes toward the object side toward the optical axis L1, and the image side lens surface 17b is a concave surface that is recessed toward the object side toward the optical axis L1. It has a part. The object side lens surface 17a and the image side lens surface 17b of the object side lens 17 are aspherical.

The image side lens 18 of the fourth lens 14 has an object side lens surface 18a having a positive curvature and an image side lens surface 18b having a negative curvature. Accordingly, the object side lens surface 18a includes a convex curved surface portion that protrudes toward the object side toward the optical axis L1, and the image side lens surface 18b protrudes toward the image axis toward the optical axis L1. It has a part. The object side lens surface 18a and the image side lens surface 18b of the image side lens 18 are aspherical.

Here, the image-side lens surface 17b of the object-side lens 17 and the object-side lens surface 18a of the image-side lens 18 which are the cemented surfaces of the object-side lens 17 and the image-side lens 18 have different aspherical shapes. Yes. Further, the thickness of the resin adhesive layer B1 on the optical axis L1 is D, and the object side lens 17 at the height H at the effective diameter of the image side lens surface 17b of the object side lens 17 in the direction orthogonal to the optical axis L1. When the sag amount of the image-side lens surface 17b is Sg1H and the sag amount of the object-side lens surface 18a of the image-side lens 18 at the height H is Sg2H, the imaging lens 10 of this example has the following conditional expression (1 ) And conditional expression (2) are satisfied. The sag amount is the image side lens surface 17b of the object side lens 17 in the direction orthogonal to the optical axis L1 when a plane that includes the intersection of the lens surface and the optical axis L1 and is orthogonal to the optical axis L1 is used as a reference plane. Is the distance in the direction of the optical axis L1 from the reference surface to the lens surface at the height H at the effective diameter. FIG. 2 is an explanatory diagram of the sag amount. S1 indicates a reference surface with respect to the image side lens surface 17b of the object side lens 17, and S2 indicates a reference surface with respect to the object side lens surface 18a of the image side lens 18.
20 μm ≦ D (1)
Sg1H <Sg2H (2)

Conditional expression (1) and conditional expression (2) indicate that the resin adhesive layer between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 which have different aspherical shapes. The thickness dimension of B1, that is, the distance between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 which are the cemented surfaces of the two lenses constituting the cemented lens is defined. Is.

Since the fourth lens 14 which is a cemented lens in this example satisfies the conditional expressions (1) and (2), the distance between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 is satisfied. Can be widened. Accordingly, during the bonding operation of bonding the object side lens 17 and the image side lens 18, the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 are brought into contact with each other, and each lens surface is contacted. It is possible to prevent or suppress the occurrence of damage. Further, since the distance between the image-side lens surface 17b of the object-side lens 17 and the object-side lens surface 18a of the image-side lens 18 is wide, it is easy for the resin adhesive to go around between these lens surfaces. It is possible to prevent bubbles from remaining.

Further, the fourth lens 14 which is a cemented lens of this example satisfies the following conditional expression (3).
D ≦ 100μm (3)

Conditional expression (3) is for suppressing an increase in the shift of the field curvature on the tangential surface to the plus side. If the upper limit value of conditional expression (3) is exceeded, the shift of the field curvature to the plus side becomes large, and correction becomes difficult. In this example, since D = 20 μm, it is possible to correct the shift to the plus side of the curvature of field in the tangential plane by design.

Furthermore, when the radius of curvature of the image side lens surface 17b of the object side lens 17 is Rs and the focal length of the entire lens system is f, the imaging lens 10 of the present example satisfies the following conditional expression (4).
0.9 ≦ Rs / f ≦ 1.3 (4)

If the lower limit of conditional expression (4) is not reached, the curvature of the image side lens surface 17b of the object side lens 17 becomes large, so that it is not easy to join the image side lens 18, and workability of joining the cemented lens is reduced. To do. On the other hand, if the upper limit value of conditional expression (4) is exceeded, it will be difficult to correct chromatic aberration. In this example, since Rs / f = 1.077, it is easy to join the cemented lens, and the chromatic aberration is corrected well.

Further, when the focal length of the entire lens system is f, the focal length of the object side lens 17 is f41, and the focal length of the image side lens 18 is f42, the imaging lens 10 of this example has the following conditional expression (5) Meet.
−3.0 ≦ (f41 / f42) /f≦−1.5 (5)

If the lower limit of conditional expression (5) is not reached, it will be difficult to balance axial chromatic aberration and lateral chromatic aberration, resulting in a decrease in the resolution of the peripheral portion of the image. If the upper limit value of conditional expression (5) is exceeded, it will be difficult to correct chromatic aberration. In this example, (f41 / f42) /f=−1.54, so that a reduction in resolution can be suppressed and chromatic aberration can be corrected well.

Here, in the imaging lens 10 of this example, when the radius of curvature of the object side lens surface 13a of the third lens 13 is R31 and the radius of curvature of the image side lens surface 13b of the third lens 13 is R32, R31 = 3. .573 and R32 = −5.766, which satisfies the following conditional expression (6).
R31 ≦ | R32 | (6)

In the imaging lens 10 of this example, the Abbe number of the first lens 11, the second lens 12, and the image side lens 18 is 40 or more, and the Abbe number of the third lens 13 and the object side lens 17 is 31 or less. Thus, chromatic aberration is corrected.

The F number of the imaging lens 10 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 99.4 °
L = 16.089mm

The focal length of the entire lens system is f, the focal length of the first lens 11 is f1, the focal length of the second lens 12 is f2, the focal length of the third lens 13 is f3, and the focal length of the fourth lens 14 is f4. When the focal length of the object side lens 17 is f41 and the focal length of the image side lens 18 is f42, these values are as follows.
f = 1.155mm
f1 = −8.193 mm
f2 = −2.685mm
f3 = 4.126mm
f4 = 3.275mm
f41 = −3.351 mm
f42 = 1.85mm

Next, Table 1A shows lens data of each lens surface of the imaging lens 10. In Table 1A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. The 7th surface is the diaphragm 15, and the 12th and 13th surfaces are the object side glass surface and the image side glass surface of the plate glass 16. The unit of curvature radius and spacing is millimeters. Note that the values of Nd (refractive index) and νd (Abbe number) of the 10 surfaces indicate the values of the resin adhesive layer B1.

Next, Table 1B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 1B, each lens surface is specified in the order counted from the object side.

The aspherical shape adopted for the lens surface is such that Y is the sag amount, c is the reciprocal of the radius of curvature, K is the cone coefficient, h is the ray height, 4th order, 6th order, 8th order, 10th order, 12th order, When the 14th and 16th order aspherical coefficients are A4, A6, A8, A10, A12, A14, and A16, respectively, they are expressed by the following equations.

(Function and effect)
3A to 3D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 10. In the longitudinal aberration diagram of FIG. 3A, the horizontal axis indicates the position where the light beam intersects the optical axis L1, and the vertical axis indicates the height at the pupil diameter. In the lateral aberration diagram of FIG. 3B, the horizontal axis indicates the entrance pupil coordinates, and the vertical axis indicates the amount of aberration. 3A and 3B show simulation results for a plurality of light beams having different wavelengths. In the field curvature diagram of FIG. 3C, the horizontal axis indicates the distance in the direction of the optical axis L1, and the vertical axis indicates the height of the image. In FIG. 3C, S represents the field curvature aberration on the sagittal surface, and T represents the field curvature aberration on the tangential surface. In the distortion diagram of FIG. 3D, the horizontal axis indicates the amount of image distortion, and the vertical axis indicates the height of the image.

As shown in FIG. 3A, according to the imaging lens 10 of this example, the axial chromatic aberration is corrected well. Further, as shown in FIG. 3B, color bleeding is suppressed. Further, as shown in FIGS. 3A and 3B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Furthermore, as shown in FIG. 3C, according to the imaging lens 10 of this example, the field curvature is corrected well. Therefore, the imaging lens 10 has a high resolution.

Here, in this example, the fourth lens 14 that is a cemented lens is designed by setting the distance between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 on the optical axis L1 in advance to 20 μm or more. doing. Therefore, at the time of designing, it is possible to consider the shift to the plus side of the curvature of field on the tangential surface, which occurs when the resin adhesive layer B1 becomes thick. Therefore, according to the imaging lens 10 of the present example, as shown in FIG. 3C, the shift of the curvature of field on the tangential surface to the plus side is suppressed.

Next, FIG. 4 is a spherical aberration diagram of the imaging lens 10, and the solid line indicates the spherical aberration with respect to a light beam having a wavelength of 588 nm (visible light beam). A dotted line indicates spherical aberration with respect to a light ray having a wavelength of 850 nm (near infrared ray). The horizontal axis of the spherical aberration diagram is the position where the light beam intersects the optical axis, and the vertical axis is the height at the pupil diameter. As shown in FIG. 4, in the imaging lens 10, spherical aberration with respect to a light beam having a wavelength of 850 nm is corrected, and it is not necessary to perform focusing when photographing under visible light and when photographing under near infrared rays. That is, in the imaging lens 10 of the present example, it is possible to suppress occurrence of a focus shift between shooting using visible light and shooting using near infrared rays. In the case where the fourth lens 14 is composed of a single lens that is not a cemented lens, both spherical aberration for a light beam having a wavelength of 588 nm (visible light) and spherical aberration for a light beam having a wavelength of 850 nm (near infrared light) are balanced. It is difficult to correct well so that no out-of-focus occurs between photographing using visible light and photographing using near infrared rays.

(Example 2)
FIG. 5 is a configuration diagram (ray diagram) of the imaging lens of the second embodiment. As shown in FIG. 5, the imaging lens 20 of this example includes, in order from the object side to the image side, a first lens 21 having a negative power, a second lens 22 having a negative power, and a positive power. It consists of a third lens 23 and a fourth lens 24 with positive power. A diaphragm 25 is disposed between the third lens 23 and the fourth lens 24, and a plate glass 26 is disposed on the image side of the fourth lens 24. The image plane I2 is located away from the plate glass 26. The fourth lens 24 is a cemented lens including an object side lens 27 having negative power and an image side lens 28 having positive power. The object side lens 27 and the image side lens 28 are bonded by a resin adhesive, and a resin adhesive layer B <b> 2 is formed between the object side lens 27 and the image side lens 28. Since the shape of each lens constituting the imaging lens 20 of this example is the same as the shape of each corresponding lens of the imaging lens 10 of Example 1, the description thereof is omitted.

The F number of the imaging lens 20 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 97.6 °
L = 15.598mm

The focal length of the entire lens system is f, the focal length of the first lens 21 is f1, the focal length of the second lens 22 is f2, the focal length of the third lens 23 is f3, and the focal length of the fourth lens 24 is f4. When the focal length of the object side lens 27 is f41 and the focal length of the image side lens 28 is f42, these values are as follows.
f = 1.141mm
f1 = −8.378 mm
f2 = -2.600mm
f3 = 4.060mm
f4 = 3.199mm
f41 = −3.520 mm
f42 = 1.889mm

In the imaging lens 20 of this example, the thickness dimension of the resin adhesive layer B2 on the optical axis L2 is D, and the effective diameter of the image side lens surface 27b of the object side lens 27 in the direction orthogonal to the optical axis L2. The sag amount of the image side lens surface 27b of the object side lens 27 at the height H is Sg1H, the sag amount of the object side lens surface 28a of the image side lens 28 at the height H is Sg2H, and the image side lens surface 27b of the object side lens 27. In the description of the first embodiment, Rs is the radius of curvature, R31 is the radius of curvature of the object side lens surface 23a of the third lens 23, and R32 is the radius of curvature of the image side lens surface 23b of the third lens 23. Conditional expressions (1) to (6) are satisfied, and the values of conditional expressions (1) and (3) to (6) are as follows.
20 μm ≦ D = 20 μm (1)
Sg1H <Sg2H (2)
D = 20 μm ≦ 100 μm (3)
0.9 ≦ Rs / f = 1.112 ≦ 1.3 (4)
−3.0 ≦ (f41 / f42) /f=−1.69≦−1.5 (5)
R31 = 3.428 ≦ | R32 | = | −5.958 | (6)

Furthermore, in the imaging lens 20 of this example, the Abbe number of the first lens 21, the second lens 22, and the image side lens 28 is 40 or more, and the Abbe number of the third lens 23 and the object side lens 27 is 31 or less. Thus, chromatic aberration is corrected.

Next, Table 2A shows lens data of each lens surface of the imaging lens 20. In Table 2A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. The 7th surface is the aperture 25, and the 12th and 13th surfaces are the object side glass surface and the image side glass surface of the plate glass 26. The unit of curvature radius and spacing is millimeters. In addition, the value of Nd (refractive index) and νd (Abbe number) of the tenth surface indicates the value of the resin adhesive layer B2.

Next, Table 2B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 2B, each lens surface is specified in the order counted from the object side.

(Function and effect)
6A to 6D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 20, respectively. As shown in FIG. 6A, according to the imaging lens 20 of this example, the axial chromatic aberration is corrected well. In addition, as shown in FIG. 6B, color bleeding is suppressed. Also,
As shown in FIGS. 6A and 6B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Furthermore, as shown in FIG. 6C, according to the imaging lens 20 of the present example, the curvature of field is favorably corrected. Therefore, the imaging lens 20 has a high resolution.

In this example, the fourth lens 24, which is a cemented lens, is designed by setting the distance between the image side lens surface 27b of the object side lens 27 and the object side lens surface 28a of the image side lens 28 on the optical axis L2 in advance to 20 μm or more. ing. Therefore, at the time of designing, it is possible to consider the shift to the plus side of the curvature of field on the tangential surface that occurs due to the thick resin adhesive layer B2. Therefore, according to the imaging lens 20 of this example, as shown in FIG. 6C, the shift of the field curvature on the tangential surface to the plus side is suppressed.

Next, FIG. 7 is a spherical aberration diagram of the imaging lens 20, and a solid line indicates spherical aberration with respect to a light beam having a wavelength of 588 nm (visible light beam). A dotted line indicates spherical aberration with respect to a light ray having a wavelength of 850 nm (near infrared ray). The horizontal axis is the position where the light beam intersects the optical axis, and the vertical axis is the height at which the light beam enters the optical system. As shown in FIG. 7, in the imaging lens 20, spherical aberration with respect to a light beam having a wavelength of 850 nm is corrected, so that it is not necessary to perform focusing when photographing under visible light and when photographing under near infrared rays. In other words, in the imaging lens 20 of this example, that is, in the imaging lens 20 of this example, occurrence of a focus shift between shooting using visible light and shooting using near infrared rays is suppressed.

(Example 3)
FIG. 8 is a configuration diagram (ray diagram) of the imaging lens of the third embodiment. As shown in FIG. 8, the imaging lens 30 of this example includes, in order from the object side to the image side, a first lens 31 having a negative power, a second lens 32 having a negative power, and a positive power. It consists of a third lens 33 and a fourth lens 34 having positive power. A diaphragm 35 is disposed between the third lens 33 and the fourth lens 34, and a plate glass 36 is disposed on the image side of the fourth lens 34. The imaging plane I3 is located away from the plate glass 36. The fourth lens 34 is a cemented lens including an object side lens 37 having negative power and an image side lens 38 having positive power. The object side lens 37 and the image side lens 38 are bonded by a resin adhesive, and a resin adhesive layer B <b> 3 is formed between the object side lens 37 and the image side lens 38. Since the shape of each lens constituting the imaging lens 30 of this example is the same as the shape of each corresponding lens of the imaging lens 10 of Example 1, the description thereof is omitted.

The F number of the imaging lens 30 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 96.0 °
L = 12.637 mm

The focal length of the entire lens system is f, the focal length of the first lens 31 is f1, the focal length of the second lens 32 is f2, the focal length of the third lens 33 is f3, and the focal length of the fourth lens 34 is f4. When the focal length of the object side lens 37 is f41 and the focal length of the image side lens 48 is f42, these values are as follows.
f = 0.847mm
f1 = −5.553 mm
f2 = -1.712mm
f3 = 2.742mm
f4 = 2.317mm
f41 = −2.670 mm
f42 = 1.493mm

In the imaging lens 30 of this example, the thickness dimension of the resin adhesive layer B3 on the optical axis L3 is D, and the effective diameter of the image side lens surface 37b of the object side lens 37 in the direction orthogonal to the optical axis L3. The sag amount of the image side lens surface 37b of the object side lens 37 at the height H is Sg1H, the sag amount of the object side lens surface 38a of the image side lens 38 at the height H is Sg2H, and the image side lens surface 37b of the object side lens 37. In the description of the first embodiment, Rs is the radius of curvature, R31 is the radius of curvature of the object side lens surface 33a of the third lens 33, and R32 is the radius of curvature of the image side lens surface 33b of the third lens 33. Conditional expressions (1) to (6) are satisfied, and the values of conditional expressions (1) and (3) to (6) are as follows.
20 μm ≦ D = 20 μm (1)
Sg1H <Sg2H (2)
D = 20 μm ≦ 100 μm (3)
0.9 ≦ Rs / f = 1.103 ≦ 1.3 (4)
−3.0 ≦ (f41 / f42) /f=−2.11≦−1.5 (5)
R31 = 1.824 ≦ | R32 | = | −8.292 | (6)

Further, in the imaging lens 30 of this example, the Abbe number of the first lens 31, the second lens 32, and the image side lens 38 is 40 or more, and the Abbe number of the third lens 33 and the object side lens 37 is 31 or less. Thus, chromatic aberration is corrected.

Next, Table 3A shows lens data of each lens surface of the imaging lens 30. In Table 3A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. Surface 7 is a diaphragm 35, and surfaces 12 and 13 are an object-side glass surface and an image-side glass surface of the plate glass 36. The unit of curvature radius and spacing is millimeters. Note that the values of Nd (refractive index) and νd (Abbe number) of the tenth surface indicate the values of the resin adhesive layer B3.

Next, Table 3B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 3B, each lens surface is specified in the order counted from the object side.

(Function and effect)
9A to 9D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 30. FIG. As shown in FIG. 9A, according to the imaging lens 30 of this example, the axial chromatic aberration is corrected well. Further, as shown in FIG. 9B, color bleeding is suppressed. Further, as shown in FIGS. 9A and 9B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Furthermore, as shown in FIG. 9C, according to the imaging lens 30 of this example, the field curvature is corrected well. Therefore, the imaging lens 30 has a high resolution.

Further, in this example, the fourth lens 34 that is a cemented lens is designed by setting the distance between the image side lens surface 37b of the object side lens 37 and the object side lens surface 38a of the image side lens 38 on the optical axis L3 in advance to 20 μm or more. ing. Therefore, at the time of designing, it is possible to consider the shift to the plus side of the curvature of field on the tangential surface, which occurs when the resin adhesive layer B3 becomes thick. Therefore, according to the imaging lens 30 of the present example, as shown in FIG. 9C, the shift of the curvature of field on the tangential surface to the plus side is suppressed.

  Next, FIG. 10 is a spherical aberration diagram of the imaging lens 30, and a solid line indicates spherical aberration with respect to a light beam having a wavelength of 588 nm (visible light beam). A dotted line indicates spherical aberration with respect to a light ray having a wavelength of 850 nm (near infrared ray). The horizontal axis is the position where the light beam intersects the optical axis, and the vertical axis is the height at which the light beam enters the optical system. As shown in FIG. 10, in the imaging lens 30, the spherical aberration with respect to the light beam having a wavelength of 850 nm is corrected, so that it is not necessary to perform focusing when photographing under visible light and when photographing under near infrared rays. That is, in the imaging lens 30 of this example, it is possible to suppress the occurrence of a focus shift between shooting using visible light and shooting using near infrared rays.

Example 4
FIG. 11 is a configuration diagram (ray diagram) of the imaging lens of Example 4. As shown in FIG. 11, the imaging lens 40 of this example includes, in order from the object side to the image side, a first lens 41 having a negative power, a second lens 42 having a negative power, and a positive power. It consists of a third lens 43 and a fourth lens 44 with positive power. A diaphragm 45 is disposed between the third lens 43 and the fourth lens 44, and a plate glass 46 is disposed on the image side of the fourth lens 44.
The imaging plane I4 is located away from the plate glass 46. The fourth lens 44 is a cemented lens including an object side lens 47 having negative power and an image side lens 48 having positive power. The object side lens 47 and the image side lens 48 are bonded by a resin adhesive, and a resin adhesive layer B <b> 4 is formed between the object side lens 47 and the image side lens 48. Since the shape of each lens constituting the imaging lens 40 of this example is the same as the shape of each corresponding lens of the imaging lens 10 of Example 1, the description thereof is omitted.

The F number of the imaging lens 40 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 96.0 °
L = 13.514mm

The focal length of the entire lens system is f, the focal length of the first lens 41 is f1, the focal length of the second lens 42 is f2, the focal length of the third lens 43 is f3, and the focal length of the fourth lens 44 is f4. When the focal length of the object side lens 47 is f41 and the focal length of the image side lens 48 is f42, these values are as follows.
f = 0.994mm
f1 = −8.279 mm
f2 = -1.785 mm
f3 = 2.929mm
f4 = 2.394mm
f41 = −3.114 mm
f42 = 1.479mm

Further, in the imaging lens 40 of this example, the thickness dimension of the resin adhesive layer B4 on the optical axis L4 is D, and the effective diameter of the image side lens surface 47b of the object side lens 47 in the direction orthogonal to the optical axis L4. The sag amount of the image side lens surface 47b of the object side lens 47 at the height H is Sg1H, the sag amount of the object side lens surface 48a of the image side lens 48 at the height H is Sg2H, and the image side lens surface 47b of the object side lens 47. In the description of the first embodiment, Rs is the radius of curvature, R31 is the radius of curvature of the object side lens surface 43a of the third lens 43, and R32 is the radius of curvature of the image side lens surface 43b of the third lens 43. Conditional expressions (1) to (6) are satisfied, and the values of conditional expressions (1) and (3) to (6) are as follows.
20 μm ≦ D = 20 μm (1)
Sg1H <Sg2H (2)
D = 20 μm ≦ 100 μm (3)
0.9 ≦ Rs / f = 1.189 ≦ 1.3 (4)
−3.0 ≦ (f41 / f42) /f=−2.12≦−1.5 (5)
R31 = 2.115 ≦ | R32 | = | −5.863 | (6)

Further, in the imaging lens 40 of this example, the Abbe number of the first lens 41, the second lens 42, and the image side lens 48 is 40 or more, and the Abbe number of the third lens 43 and the object side lens 47 is 31 or less. Thus, chromatic aberration is corrected.

Next, Table 4A shows lens data of each lens surface of the imaging lens 40. In Table 4A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. The 7th surface is an aperture 45, and the 12th and 13th surfaces are an object side glass surface and an image side glass surface of the plate glass 46. The unit of curvature radius and spacing is millimeters. In addition, the value of Nd (refractive index) and νd (Abbe number) of the tenth surface indicates the value of the resin adhesive layer B4.

Next, Table 4B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 4B, each lens surface is specified in the order counted from the object side.

(Function and effect)
12A to 12D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 40. FIG. As shown in FIG. 12A, according to the imaging lens 40 of this example, the axial chromatic aberration is corrected well. Further, as shown in FIG. 12B, color bleeding is suppressed. Further, as shown in FIGS. 12A and 12B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Furthermore, as shown in FIG. 12C, according to the imaging lens 40 of the present example, the curvature of field is favorably corrected. Therefore, the imaging lens 40 has a high resolution.

Further, in this example, the fourth lens 44 that is a cemented lens is designed by setting the distance between the image side lens surface 47b of the object side lens 47 and the object side lens surface 48a of the image side lens 48 on the optical axis L4 in advance to 20 μm or more. ing. Accordingly, at the time of designing, it is possible to consider the shift to the plus side of the curvature of field on the tangential surface that occurs due to the thick resin adhesive layer B4. Therefore, according to the imaging lens 40 of the present example, as shown in FIG. 12C, the shift of the curvature of field on the tangential surface to the plus side is suppressed.

Next, FIG. 13 is a spherical aberration diagram of the imaging lens 40, and the solid line shows the spherical aberration with respect to a light beam having a wavelength of 588 nm (visible light beam). A dotted line indicates spherical aberration with respect to a light ray having a wavelength of 850 nm (near infrared ray). The horizontal axis is the position where the light beam intersects the optical axis, and the vertical axis is the height at which the light beam enters the optical system. As shown in FIG. 13, in the imaging lens 40, spherical aberration with respect to a light beam having a wavelength of 850 nm is corrected, and it is not necessary to perform focusing when photographing under visible light and when photographing under near infrared rays. That is, in the imaging lens 40 of the present example, it is possible to suppress the occurrence of a focus shift between shooting using visible light and shooting using near infrared rays.

(Example 5)
FIG. 14 is a configuration diagram (ray diagram) of the imaging lens of Example 5. As shown in FIG. 14, the imaging lens 50 of this example includes, in order from the object side to the image side, a first lens 51 having a negative power, a second lens 52 having a negative power, and a positive power. It consists of a third lens 53 and a fourth lens 54 having positive power. A diaphragm 55 is disposed between the third lens 53 and the fourth lens 54, and a plate glass 56 is disposed on the image side of the fourth lens 54.
The imaging plane I5 is located away from the plate glass 56. The fourth lens 54 is a cemented lens including an object side lens 57 having negative power and an image side lens 58 having positive power. The object side lens 57 and the image side lens 58 are bonded by a resin adhesive, and a resin adhesive layer B <b> 5 is formed between the object side lens 57 and the image side lens 58. The shape of each lens composing the imaging lens 50 of this example is the same as the shape of each corresponding lens of the imaging lens 10 of Example 1, and therefore the description thereof is omitted.

The F number of the imaging lens 50 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 100.0 °
L = 19.664 mm

The focal length of the entire lens system is f, the focal length of the first lens 51 is f1, the focal length of the second lens 52 is f2, the focal length of the third lens 53 is f3, and the focal length of the fourth lens 54 is f4. When the focal length of the object side lens 57 is f41 and the focal length of the image side lens 58 is f42, these values are as follows.
f = 1.248mm
f1 = −8.890 mm
f2 = -2.602 mm
f3 = 4.265 mm
f4 = 3.481mm
f41 = −4.227mm
f42 = 1.479mm

Further, in the imaging lens 50 of this example, the thickness dimension of the resin adhesive layer B5 on the optical axis L5 is D, and the effective diameter of the image side lens surface 57b of the object side lens 57 in the direction orthogonal to the optical axis L5. The sag amount of the image side lens surface 57b of the object side lens 57 at the height H is Sg1H, the sag amount of the object side lens surface 58a of the image side lens 58 at the height H is Sg2H, and the image side lens surface 57b of the object side lens 57. In the description of the first embodiment, the radius of curvature of the third lens 53 is Rs, the radius of curvature of the object-side lens surface 53a of the third lens 53 is R31, and the radius of curvature of the image-side lens surface 53b of the third lens 53 is R32. Conditional expressions (1) to (6) are satisfied, and the values of conditional expressions (1) and (3) to (6) are as follows.
20 μm ≦ D = 20 μm (1)
Sg1H <Sg2H (2)
D = 20 μm ≦ 100 μm (3)
0.9 ≦ Rs / f = 1.120 ≦ 1.3 (4)
−3.0 ≦ (f41 / f42) /f=−1.50≦−1.5 (5)
R31 = 2.828 ≦ | R32 | = | −13.176 | (6)

Furthermore, in the imaging lens 50 of the present example, the Abbe number of the first lens 51, the second lens 52, and the image side lens 58 is 40 or more, and the Abbe number of the third lens 53 and the object side lens 57 is 31 or less. Thus, chromatic aberration is corrected.

Next, Table 5A shows lens data of each lens surface of the imaging lens 50. In Table 5A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. Surface 7 is a diaphragm 55, and surfaces 12 and 13 are an object side glass surface and an image side glass surface of the plate glass 56. The unit of curvature radius and spacing is millimeters. In addition, the value of Nd (refractive index) and νd (Abbe number) of the tenth surface indicates the value of the resin adhesive layer B5.

Next, Table 5B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 5B, each lens surface is specified in the order counted from the object side.

(Function and effect)
15A to 15D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 50. FIG. As shown in FIG. 15A, according to the imaging lens 50 of this example, the axial chromatic aberration is corrected well. Further, as shown in FIG. 15B, color bleeding is suppressed.
Further, as shown in FIGS. 15A and 15B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Further, as shown in FIG. 15C, according to the imaging lens 50 of the present example, the curvature of field is favorably corrected. Therefore, the imaging lens 50 has a high resolution.

Further, in this example, the fourth lens 54 which is a cemented lens is designed with an interval on the optical axis L5 between the image side lens surface 57b of the object side lens 57 and the object side lens surface 58a of the image side lens 58 set to 20 μm or more in advance. ing. Accordingly, at the time of designing, it is possible to consider the shift to the plus side of the curvature of field on the tangential surface, which occurs when the resin adhesive layer B5 becomes thick. Therefore, according to the imaging lens 50 of the present example, as shown in FIG. 15C, the shift of the field curvature on the tangential surface to the plus side is suppressed.

Next, FIG. 16 is a spherical aberration diagram of the imaging lens 50, and the solid line shows the spherical aberration with respect to a light beam having a wavelength of 588 nm (visible light beam). A dotted line indicates spherical aberration with respect to a light ray having a wavelength of 850 nm (near infrared ray). The horizontal axis is the position where the light beam intersects the optical axis, and the vertical axis is the height at which the light beam enters the optical system. As shown in FIG. 16, in the imaging lens 50, spherical aberration with respect to a light beam having a wavelength of 850 nm is corrected, and it is not necessary to perform focusing when photographing under visible light and when photographing under near infrared rays. That is, in the imaging lens 50 of the present example, it is possible to suppress the occurrence of a focus shift between shooting using visible light and shooting using near infrared rays.

(Other embodiments)
In the imaging lenses 10 to 50, the image side lens surfaces (13b, 23b, 33b, 43b, 53b) of the third lens have a negative curvature, and are convex curved surfaces that protrude toward the image side toward the optical axis. This image side lens surface (13b, 23b, 33b, 43b, 53b) has a positive curvature and a concave curved surface portion that is recessed toward the object side toward the optical axis. Also good. Also in this case, satisfying conditional expression (6) makes it easy to make the imaging lenses 10 to 50 wide-angle lenses.

(Imaging device)
FIG. 17 is an explanatory diagram of an image pickup apparatus equipped with an image pickup lens using the cemented lens of the present invention. As shown in FIG. 17, the imaging device 60 includes an imaging device 61 in which a sensor surface 61 a is arranged on the imaging plane I <b> 1 (focal position) of the imaging lens 10. The image sensor 61 is a CCD sensor or a CMOS sensor.

According to this example, since the resolution of the imaging lens is high, the imaging device 60 can have a high resolution by adopting an imaging device having a large number of pixels as the imaging device 61. Here, in the imaging device 60, the imaging lenses 20 to 50 can be mounted in the same manner as the imaging lens 10, and the same effect can be obtained in this case as well.

As indicated by a two-dot chain line in FIG. 17, in the imaging device 60, near-infrared rays and visible rays in a band including a wavelength of 850 nm are transmitted between the imaging lens 10 and the imaging element 61 and guided to the imaging lens 10. By disposing the optical filter 62, it is possible to obtain an imaging device that uses near infrared rays and visible rays. In other words, the imaging lens 10 prevents or suppresses the occurrence of a focus shift between shooting using visible light and shooting using near infrared rays. Therefore, only by mounting the optical filter 62 on the imaging device 60, imaging using near infrared rays including a wavelength of 850 nm, for example, light in a band of 800 nm to 1100 nm, and visible light, that is, light having a wavelength of 400 nm to 700 nm. It is possible to configure an image pickup apparatus that performs both shootings using the. Also, in the imaging lenses 20 to 50, the occurrence of a focus shift between shooting using visible light and shooting using near infrared rays is prevented or suppressed. Accordingly, as in the case of using the imaging lens 10, an imaging device that performs both imaging using near infrared rays including a wavelength of 850 nm and imaging using visible light only by mounting the optical filter 62 on the imaging device 60 is configured. Is possible. The optical filter 62 may be disposed on the object side of the imaging lenses 10-50.

(Reference Example 1)
The imaging lenses of Reference Examples 1 to 3 will be described below with reference to FIGS. The imaging lenses of Reference Examples 1 to 3 have the same configuration as in Examples 1 to 5, but the thickness on the optical axis of the resin adhesive layer that bonds the two lenses constituting the cemented lens. The dimension, that is, the distance on the optical axis between the two lenses constituting the cemented lens is less than 20 μm.

FIG. 18 is a configuration diagram (ray diagram) of the imaging lens of Reference Example 1. As shown in FIG. 18, the imaging lens 70 of this example includes, in order from the object side to the image side, a first lens 71 having negative power, a second lens 72 having negative power, and positive power. It consists of a third lens 73 and a fourth lens 74 having positive power. A diaphragm 75 is disposed between the third lens 73 and the fourth lens 74, and a plate glass 76 is disposed on the image side of the fourth lens 74. The image plane I7 is located away from the plate glass 76. The fourth lens 74 is a cemented lens including an object side lens 77 having negative power and an image side lens 78 having positive power.
The image side lens surface 77b of the object side lens 77 and the object side lens surface 78a of the image side lens 78, which are the cemented surfaces of the cemented lens, have the same shape. The object side lens 77 and the image side lens 78 are bonded by a resin adhesive, but the gap between the object side lens 77 and the image side lens 78 is practically zero.

The F number of the imaging lens 70 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 88.6 °
L = 12.499mm

The focal length of the entire lens system is f, the focal length of the first lens 71 is f1, the focal length of the second lens 72 is f2, the focal length of the third lens 73 is f3, and the focal length of the fourth lens 74 is f4. When the focal length of the object side lens 77 is f41 and the focal length of the image side lens 78 is f42, these values are as follows.
f = 1.444mm
f1 = −6.918 mm
f2 = −2.422mm
f3 = 3.349mm
f4 = 3.215mm
f41 = −3.243mm
f42 = 1.752mm

Further, the imaging lens 70 of the present example has a sag amount of the image side lens surface 77b of the object side lens 77 at a height H at an effective diameter of the image side lens surface 77b of the object side lens 77 in a direction orthogonal to the optical axis L7. Sg1H, the sag amount of the object side lens surface 78a of the image side lens 78 at the height H is Sg2H, the radius of curvature of the image side lens surface 77b of the object side lens 77 is Rs, and the object side lens surface 73a of the third lens 73 is Conditional expression (2), conditional expression (5), and conditional expression (6) shown in the description of the first embodiment when the curvature radius is R31 and the curvature radius of the image side lens surface 73b of the third lens 73 is R32. Meet. The values of conditional expression (5) and conditional expression (6) are as follows.
Sg1H <Sg2H (2)
−3.0 ≦ (f41 / f42) /f=−1.28≦−1.5 (5)
R31 = 2.400 ≦ | R32 | = | −8.121 | (6)

Furthermore, in the imaging lens 70 of this example, the Abbe number of the first lens 71, the second lens 72, and the image side lens 78 is 40 or more, and the Abbe number of the third lens 73 and the object side lens 77 is 31 or less. Thus, chromatic aberration is corrected.

In the imaging lens 70, Rs / f = 0.848, which is below the lower limit value of the conditional expression (4).

Next, Table 6A shows lens data of each lens surface of the imaging lens 70. In Table 6A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. Surface 7 is a diaphragm 75, and surfaces 11 and 12 are an object side glass surface and an image side glass surface of the plate glass 76. The unit of curvature radius and spacing is millimeters.

Next, Table 6B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 6B, each lens surface is specified in the order counted from the object side.

19A to 19D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 70. FIG. As shown in FIG. 19A, according to the imaging lens 70 of this example, the axial chromatic aberration is corrected well. In addition, as shown in FIG. 19B, color bleeding is suppressed.
Further, as shown in FIGS. 19A and 19B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Furthermore, as shown in FIG. 19C, according to the imaging lens 70 of the present example, the field curvature is corrected well.

(Reference Example 2)
FIG. 20 is a configuration diagram (ray diagram) of the imaging lens of Reference Example 2. As shown in FIG. 20, the imaging lens 80 of this example includes, in order from the object side to the image side, a first lens 81 having negative power, a second lens 82 having negative power, and positive power. It consists of a third lens 83 and a fourth lens 84 having positive power. A diaphragm 85 is disposed between the third lens 83 and the fourth lens 84, and a plate glass 86 is disposed on the image side of the fourth lens 84. The image plane I8 is located away from the plate glass 86. The fourth lens 84 is a cemented lens including an object side lens 87 having negative power and an image side lens 88 having positive power.
The image side lens surface 87b of the object side lens 87 and the object side lens surface 88a of the image side lens 88, which are the cemented surfaces of the cemented lens, have the same shape. The object side lens 87 and the image side lens 88 are bonded by a resin adhesive, but the gap between the object side lens 87 and the image side lens 88 is practically zero.

The F number of the imaging lens 80 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 100.8 °
L = 13.301 mm

The focal length of the entire lens system is f, the focal length of the first lens 81 is f1, the focal length of the second lens 82 is f2, the focal length of the third lens 83 is f3, and the focal length of the fourth lens 84 is f4. When the focal length of the object side lens 87 is f41 and the focal length of the image side lens 88 is f42, these values are as follows.
f = 1.187mm
f1 = −6.813 mm
f2 = −2.080mm
f3 = 3.061mm
f4 = 3.238mm
f41 = -2.699mm
f42 = 1.743mm

Further, in the imaging lens 80 of the present example, the sag amount of the image side lens surface 87b of the object side lens 87 at the height H at the effective diameter of the image side lens surface 87b of the object side lens 87 in the direction orthogonal to the optical axis L8. Sg1H, the sag amount of the object side lens surface 88a of the image side lens 88 at height H is Sg2H, the radius of curvature of the image side lens surface 87b of the object side lens 87 is Rs, and the object side lens surface 83a of the third lens 83 is Conditional expression (2), conditional expression (4), and conditional expression (6) shown in the description of the first embodiment when the curvature radius is R31 and the curvature radius of the image side lens surface 83b of the third lens 83 is R32. Meet. The values of conditional expression (4) and conditional expression (6) are as follows.
Sg1H <Sg2H (2)
0.9 ≦ Rs / f = 1.016 ≦ 1.3 (4)
R31 = 2.437 ≦ | R32 | = | −5.274 | (6)

Furthermore, in the imaging lens 80 of this example, the Abbe number of the first lens 81, the second lens 82, and the image side lens 88 is 40 or more, and the Abbe number of the third lens 83 and the object side lens 87 is 31 or less. Thus, chromatic aberration is corrected.

The imaging lens 80 has (f41 / f42) /f=-1.30, which exceeds the upper limit value of the conditional expression (5).

Next, Table 7A shows lens data of each lens surface of the imaging lens 80. In Table 7A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. The 7th surface is a diaphragm 85, and the 11th and 12th surfaces are an object side glass surface and an image side glass surface of the plate glass 86. The unit of curvature radius and spacing is millimeters.

Next, Table 7B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 7B, each lens surface is specified in the order counted from the object side.

21A to 21D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 80. FIG. As shown in FIG. 21A, according to the imaging lens 80 of this example, the axial chromatic aberration is corrected well. In addition, as shown in FIG. 21B, color bleeding is suppressed.
Further, as shown in FIGS. 21A and 21B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Furthermore, as shown in FIG. 21C, according to the imaging lens 80 of this example, the curvature of field is corrected well.

(Reference Example 3)
FIG. 22 is a configuration diagram (ray diagram) of the imaging lens of Reference Example 3. As shown in FIG. 22, the imaging lens 90 of this example includes, in order from the object side to the image side, a first lens 91 having negative power, a second lens 92 having negative power, and positive power. It consists of a third lens 93 and a fourth lens 94 having positive power. A diaphragm 95 is disposed between the third lens 93 and the fourth lens 94, and a plate glass 96 is disposed on the image side of the fourth lens 94. The imaging plane I9 is located away from the plate glass 96. The fourth lens 94 is a cemented lens including an object side lens 97 having negative power and an image side lens 98 having positive power.
The image side lens surface 97b of the object side lens 97 and the object side lens surface 98a of the image side lens 98, which are the cemented surfaces of the cemented lens, have the same shape. The object side lens 97 and the image side lens 98 are bonded by a resin adhesive, but the gap between the object side lens 97 and the image side lens 98 is practically zero.

The F number of the imaging lens 90 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 97.6 °
L = 15.633mm

The focal length of the entire lens system is f, the focal length of the first lens 91 is f1, the focal length of the second lens 92 is f2, the focal length of the third lens 93 is f3, and the focal length of the fourth lens 94 is f4. When the focal length of the object side lens 97 is f41 and the focal length of the image side lens 98 is f42, these values are as follows.
f = 1.149mm
f1 = −8.499mm
f2 = −2.585mm
f3 = 3.991 mm
f4 = 3.208mm
f41 = -3.508mm
f42 = 1.833mm

Further, the imaging lens 90 of the present example has a sag amount of the image side lens surface 97b of the object side lens 97 at the height H at the effective diameter of the image side lens surface 97b of the object side lens 97 in the direction orthogonal to the optical axis L9. Sg1H, the sag amount of the object side lens surface 98a of the image side lens 98 at the height H is Sg2H, the radius of curvature of the image side lens surface 97b of the object side lens 97 is Rs, and the object side lens surface 93a of the third lens 93 is When the radius of curvature is R31 and the radius of curvature of the image side lens surface 93b of the third lens 93 is R32, the conditional expressions (2) and (4) to (6) shown in the description of the first embodiment are satisfied. . The values of conditional expressions (4) to (6) are as follows.
Sg1H <Sg2H (2)
0.9 ≦ Rs / f = 1.110 ≦ 1.3 (4)
−3.0 ≦ (f41 / f42) /f=−1.67≦−1.5 (5)
R31 = 3.342 ≦ | R32 | = | −5.935 | (6)

Furthermore, in the imaging lens 90 of this example, the Abbe number of the first lens 91, the second lens 92, and the image side lens 98 is 40 or more, and the Abbe number of the third lens 93 and the object side lens 97 is 31 or less. Thus, chromatic aberration is corrected.

Next, Table 8A shows lens data of each lens surface of the imaging lens 90. In Table 8A, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. Surface 7 is a diaphragm 95, and surfaces 11 and 12 are an object side glass surface and an image side glass surface of the plate glass 96. The unit of curvature radius and spacing is millimeters.

Next, Table 8B shows aspheric coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 8B, each lens surface is specified in the order counted from the object side.

23A to 23D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 90. FIG. As shown in FIG. 23A, according to the imaging lens 90 of this example, the axial chromatic aberration is corrected well. Further, as shown in FIG. 23B, color bleeding is suppressed.
Further, as shown in FIGS. 23A and 23B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Further, as shown in FIG. 23C, according to the imaging lens 90 of the present example, the curvature of field is well corrected.

10, 20, 30, 40, 50 Imaging lenses 11, 21, 31, 41, 51 First lens 12, 22, 32, 42, 52 Second lens 13, 23, 33, 43, 53 Third lens 14, 24・ 34 ・ 44 ・ 54 4th lens (Bonded lens)
17, 27, 37, 47, 57 Object side lens 18, 28, 38, 48, 58 Image side lens 15, 25, 35, 45, 55 Aperture B1, B2, B3, B4, B5 Resin adhesive layer L1, L2 L3, L4, L5 Optical axes I1, I2, I3, I4, I5 Imaging surface 60 Imaging device 61 Imaging element 61a Sensor surface 62 Optical filter

Claims (3)

A resin adhesive layer comprising a lens having a negative power and a lens having a positive power, and having a positive power and bonding the lens having the negative power and the lens having the positive power. With
The joining surface between the lens having negative power and the resin adhesive layer and the joining surface between the lens having positive power and the resin adhesive layer have different aspherical shapes. ,
The Abbe number of the lens having the negative power is 31 or less, and the Abbe number of the lens having the positive power is 56 or more,
The lens having the negative power at the height H at the effective diameter of the joint surface of the lens having the negative power in the direction orthogonal to the optical axis D and the thickness dimension of the resin adhesive layer on the optical axis Where Sg1H is the sag amount of the lens and the sag amount of the lens having the positive power at the height H is Sg2H, the following conditional expressions (1) , (2), and The cemented lens characterized by satisfying (3) .
20 μm ≦ D (1)
Sg1H <Sg2H (2)
D ≦ 100μm (3) 2. The cemented lens according to claim 1, wherein both lens surfaces of the lens having negative power have an aspheric shape, and both lens surfaces of the lens having positive power have an aspheric shape. An imaging lens comprising the cemented lens according to claim 1.

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