JP2018084704A - Imaging lens, imaging lens unit and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens that can exhibit a stable resolution performance while accommodating environmental changes.SOLUTION: An imaging lens forms an image of near-infrared light. The imaging lens substantially consists of, in order from the object side, a positive first lens L1, a positive second lens L2, and a third lens L3. The first lens L1 is made of glass, the second and third lenses L2, L3 are made of resin, and the second and third lenses L2, L3 each have an aspheric surface on at least one side, satisfying the conditional expressions (1)-(6).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a near infrared imaging lens, and an imaging lens unit and an imaging apparatus incorporating the imaging lens.

  In-vehicle lenses that detect driver gaze and snoozing have been developed. A near-infrared optical system is mainly used for such a driver monitor lens. A lens for a driver monitor has a relatively narrow angle of view among in-vehicle lenses, and thus has a configuration similar to a lens for a mobile phone. However, a lens with a fixed focal point and resistant to environmental temperature changes is required. As a near-infrared light lens, a three-lens structure with a small number of lenses is known (see, for example, Patent Documents 1 and 2). In addition, although it is a lens for visible light, the thing with a small number of lenses of the 3 lens structure is well-known (for example, refer patent document 3).

  The lenses described in Patent Document 1 are all made of resin lenses and are difficult to cope with environmental temperature changes. The lens described in Patent Document 2 has a relatively large overall length. In the lens described in Patent Document 3, the ratio between the focal length of the second lens and the focal length of the third lens is relatively small, and the power of each lens is too strong when temperature changes are taken into account. Occasionally, various aberrations occur and the resolution performance is likely to deteriorate.

International Publication No. 2013/021659 JP 2014-167497 A JP 2004-252312 A

  The present invention has been made in view of the above-described background art, and an object thereof is to provide an imaging lens that can exhibit stable resolution performance while responding to environmental temperature changes.

  Another object of the present invention is to provide an imaging lens unit and an imaging apparatus incorporating the imaging lens.

In order to achieve the above object, an imaging lens according to the present invention is an imaging lens that forms near-infrared light, and in order from the object side, a positive first lens, a positive second lens, and a third lens The first lens is made of glass, the second and third lenses are made of resin, and the second and third lenses each have at least one aspheric surface, The following conditional expression is satisfied.
1.7 ≦ nd1 ≦ 2.2 (1)
10 ≦ νd1 ≦ 50 (2)
1e-6 ≦ α1 ≦ 1.2e-5 (3)
0.1 ≦ d1 / TL ≦ 0.25 (4)
−0.7 ≦ f2 / f3 ≦ 0.2 (5)
0.31 ≦ Y / TL ≦ 0.7 (6)
Here, the value nd1 is the d-line refractive index of the first lens, the value νd1 is the Abbe number of the first lens, the value α1 is the linear expansion coefficient per 1K in the first lens, and the value d1 is the first The axial thickness of the lens, the value TL is the total optical length, the value f2 is the focal length of the second lens, the value f3 is the focal length of the third lens, and the value Y is the maximum image height. The optical total length is the air equivalent length when a parallel plate is disposed between the third lens and the image plane. Further, the third lens may be any of negative, positive, and almost non-power. In the conditional expression (3), a power of 10 (for example, 1.2 × 10 ⁻⁵ ) is expressed using e (for example, 1.2e−5).

  According to the imaging lens, various sensing can be performed by imaging near infrared light. Further, by configuring the imaging lens from the object side to include the positive first lens, the positive second lens, and the third lens, the configuration is close to the telephoto type, and the optical total length can be easily shortened. In addition, the first lens is made of glass, and the second and third lenses are made of resin, so that fluctuations in performance can be suppressed even when the environmental temperature changes. Stable resolution performance can be exhibited even in an environment. In addition, by using a lens material satisfying the conditional expressions (1) and (2) for the first lens with strong power, the optical total length can be shortened and the radius of curvature can be increased, and spherical aberration and coma are generated. Can be suppressed. Further, by satisfying conditional expression (3), it is possible to reduce the power change of the lens at the time of high temperature or low temperature change, and to suppress the focal position shift. Moreover, it becomes easy to suppress curvature of field by falling below the upper limit of the value d1 / TL of conditional expression (4). On the other hand, exceeding the lower limit of the value d1 / TL of conditional expression (4) makes it easy to correct spherical aberration. Also, by satisfying conditional expression (5), the power change of the second and third lenses is not increased at the time of temperature change, and the occurrence of focal position shift and field curvature is suppressed, resulting in a decrease in resolution. Can be prevented. In addition, by falling below the upper limit of the value Y / TL of the conditional expression (6), the power of each lens is not excessively strong, and various aberrations are generated when the temperature changes to prevent the resolution performance from deteriorating significantly. Therefore, it is possible to prevent the productivity from being lowered. On the other hand, by exceeding the lower limit of the value Y / TL of conditional expression (6), the size of the lens does not become too large, the degree of freedom of installation is maintained, and the equipment on which the present imaging lens can be mounted is not limited.

Conditional expressions (4) and (6) are more preferably set to the following ranges.
0.12 ≦ d1 / TL ≦ 0.25 (4) ′
0.31 ≦ Y / TL ≦ 0.45 (6) ′

In a specific aspect of the invention, the imaging lens satisfies the following conditional expression.
1.52 ≦ nd2 ≦ 1.7 (7)
1.52 ≦ nd3 ≦ 1.7 (8)
| Nd2-nd3 | ≦ 0.05 (9)
Here, the value nd2 is the d-line refractive index of the second lens, and the value nd3 is the d-line refractive index of the third lens.

  By using lens materials satisfying conditional expressions (7) to (9) for the second and third lenses, the Petzval sum can be reduced and the astigmatic difference can be suppressed.

In another aspect of the present invention, the imaging lens satisfies the following conditional expression.
Fn ≦ 3.5 (10)
Here, the value Fn is the F number of the entire system.

  When the conditional expression (10) is satisfied, since the power of each lens is increased, the spherical aberration and the coma aberration are increased, and the focal position shift and the field curvature fluctuation at the time of temperature change tend to be larger. Therefore, when the conditional expression (10) is satisfied, the effects of the conditional expressions (1) to (6) are more exhibited.

The conditional expression (10) is more preferably set to the following range.
Fn ≦ 2.8 (10) ′

In still another aspect of the present invention, the imaging lens satisfies the following conditional expression.
1 ≦ f1 / f ≦ 2 (11)
Here, the value f1 is the focal length of the first lens, and the value f is the focal length of the entire system.

  When the value f1 / f of the conditional expression (11) is below the upper limit, spherical aberration and coma are sufficiently corrected. On the other hand, the axial chromatic aberration can be easily corrected by exceeding the lower limit of the value f1 / f of the conditional expression (11).

The conditional expression (11) is more preferably set to the following range.
1.2 ≦ f1 / f ≦ 2 (11) ′

In still another aspect of the present invention, the imaging lens satisfies the following conditional expression.
0.6 ≦ f1 / f2 ≦ 2.5 (12)
Here, the value f1 is the focal length of the first lens, and the value f2 is the focal length of the second lens.

  By falling below the upper limit of the value f1 / f2 of the conditional expression (12), it is possible to prevent the focal position shift from occurring due to the power change of the second lens becoming too large when the temperature changes. On the other hand, the axial chromatic aberration can be easily corrected by exceeding the lower limit of the value f1 / f2 of the conditional expression (12).

The conditional expression (12) is more preferably set to the following range.
1.1 ≦ f1 / f2 ≦ 2.3 (12) ′

In still another aspect of the present invention, the imaging lens satisfies the following conditional expression.
0.8 ≦ f1 / f23 ≦ 5 (13)
Here, the value f1 is the focal length of the first lens, and the value f23 is the combined focal length of the second and third lenses.

  By falling below the upper limit of the value f1 / f23 of conditional expression (13), the size of the lens does not become too large, and the degree of freedom in installation is maintained, so that the apparatus on which the imaging lens can be mounted is not limited. On the other hand, by exceeding the lower limit of the value f1 / f23 of conditional expression (13), the power of the first lens does not become too large, and the spherical aberration and the coma aberration can be sufficiently corrected.

The conditional expression (13) is more preferably set to the following range.
0.8 ≦ f1 / f23 ≦ 1.5 (13) ′

  In still another aspect of the present invention, the first lens has spherical surfaces on both sides. In this case, by forming the first lens with a spherical surface, a molding die is unnecessary, and the cost can be reduced.

  In still another aspect of the present invention, an aperture stop is provided between the first lens and the second lens. With this arrangement, it is easy to correct lateral chromatic aberration. Also, with this arrangement, distortion aberration can be easily controlled, so that the distortion shape can easily be a natural shape having no inflection point.

In still another aspect of the present invention, the imaging lens satisfies the following conditional expression.
−1.9 ≦ (L1R1 + L1R2) / (L1R1−L1R2) ≦ −1 (14)
Here, the value L1R1 is the radius of curvature of the object side surface of the first lens, and the value L1R2 is the radius of curvature of the image side surface of the first lens.

  The spherical aberration can be easily corrected by falling below the upper limit of the value (L1R1 + L1R2) / (L1R1−L1R2) in the conditional expression (14). On the other hand, astigmatism can be suppressed by exceeding the lower limit of the value (L1R1 + L1R2) / (L1R1−L1R2) in conditional expression (14).

The conditional expression (14) is more preferably set to the following range.
−1.9 ≦ (L1R1 + L1R2) / (L1R1−L1R2) ≦ −1.5 (14) ′

  In order to achieve the above object, a lens unit according to the present invention includes the above-described imaging lens and a lens holder that holds the imaging lens.

  The lens unit includes the imaging lens described above, and can exhibit stable resolution performance while responding to environmental temperature changes.

  In order to achieve the above object, an imaging apparatus according to the present invention includes the imaging lens described above and an imaging element on which an image from the imaging lens is projected.

  The imaging apparatus includes the imaging lens described above, and imaging that exhibits stable resolution performance is possible while responding to changes in environmental temperature.

It is a figure explaining an imaging device provided with the imaging lens of one embodiment of the present invention. 2 is a cross-sectional view of an imaging lens and the like according to Embodiment 1. FIG. FIGS. 4A to 4C are longitudinal aberration diagrams of the imaging lens of Example 1. FIGS. FIGS. 4A to 4E are lateral aberration diagrams of the imaging lens of Example 1. FIGS. FIG. 6 is a cross-sectional view of an imaging lens and the like of Example 2. FIGS. 4A to 4C are longitudinal aberration diagrams of the imaging lens of Example 2. FIGS. FIGS. 7A to 7E are lateral aberration diagrams of the imaging lens of Example 2. FIGS. FIG. 6 is a cross-sectional view of an imaging lens and the like of Example 3. FIGS. 4A to 4C are longitudinal aberration diagrams of the imaging lens of Example 3. FIGS. FIGS. 7A to 7E are lateral aberration diagrams of the imaging lens of Example 3. FIGS. 6 is a cross-sectional view of an imaging lens and the like of Example 4. FIG. FIGS. 8A to 8C are longitudinal aberration diagrams of the imaging lens of Example 4. FIGS. FIGS. 4A to 4E are lateral aberration diagrams of the imaging lens of Example 4. FIGS.

  FIG. 1 is a cross-sectional view showing an imaging apparatus 100 according to an embodiment of the present invention. The imaging apparatus 100 includes a camera module 30 for forming an image signal, and a processing unit 60 that exhibits the function of the imaging apparatus 100 by operating the camera module 30.

  The camera module 30 includes a lens unit 40 including the imaging lens 10 and a sensor unit 50 that converts a subject image formed by the imaging lens 10 into an image signal.

  The lens unit 40 includes an imaging lens 10 and a lens barrel 41 incorporating the imaging lens 10. Although details will be described later, the imaging lens 10 includes a first lens L1, a second lens L2, and a third lens L3. The lens barrel 41 is formed of a resin, a metal, a resin mixed with glass fiber, or the like, and stores and holds a lens or the like therein. When the lens barrel 41 is formed of a metal or a resin in which a class fiber is mixed, it is less likely to expand than the resin and the imaging lens 10 can be stably fixed. The lens barrel 41 has an opening OP through which a light beam from the object side is incident.

  The first to third lenses L1 to L3 constituting the imaging lens 10 are directly or indirectly held on the inner surface side of the lens barrel 41 at the flange portion or the outer peripheral portion thereof, and the optical axis AX direction and the optical axis AX Positioning in a direction perpendicular to the direction is made.

  The sensor unit 50 includes an image sensor (solid-state image sensor) 51 (for example, a CMOS image sensor) that photoelectrically converts a subject image formed by the imaging lens 10, and supports the image sensor 51 from the back, wiring, and peripherals. And a substrate 52 provided with a circuit or the like. The sensor unit 50 is held in the lens barrel 41 and is positioned and fixed with respect to the optical axis AX.

  The image pickup device (solid-state image pickup device) 51 has a photoelectric conversion unit 51a as the image pickup surface I, and a signal processing circuit (not shown) is formed around it. Pixels, that is, photoelectric conversion elements are two-dimensionally arranged in the photoelectric conversion unit 51a. Note that the image sensor 51 is not limited to the above-described CMOS type image sensor, but may be one to which another device such as a CCD is applied.

  The processing unit 60 includes a drive unit 61, an input unit 62, a storage unit 63, a display unit 64, and a control unit 68. The drive unit 61 operates the image pickup device 51 by receiving supply of a voltage and a clock signal for driving the image pickup device 51 from the control unit 68 and outputting them to a circuit associated with the image pickup device 51. In addition, the drive unit 61 outputs the digital pixel signal from the image sensor 51 as it is or after being processed to the external circuit under the control of the control unit 68. The input unit 62 is a part that accepts user operations, the storage unit 63 is a part that stores information necessary for the operation of the imaging apparatus 100, image data acquired by the camera module 30, and the like. This is a part for displaying information to be presented to the user, captured images, and the like. The control unit 68 comprehensively controls operations of the drive unit 61, the input unit 62, the storage unit 63, the display unit 64, and the like, and performs various image processing on the image data obtained by the camera module 30, for example. be able to.

  Although detailed description is omitted, the specific function of the processing unit 60 is appropriately adjusted according to the application of the device in which the imaging apparatus 100 is incorporated. The imaging apparatus 100 according to the present embodiment employs a near-infrared optical system for a driver monitor, for example, and is used for applications that detect a driver's line of sight or doze. As a light source of a driver monitor system incorporating the imaging device 100, for example, a near infrared LED or the like can be used. The imaging lens 10 mounted on the imaging device 100 has a configuration like a portable lens because the angle of view is relatively narrow among in-vehicle lenses. However, the imaging lens 10 needs to cope with environmental temperature changes at a fixed focus, which will be described later. As described above, glass is used for the first lens L1 closest to the object side. In addition to the driver monitor system, the imaging apparatus 100 can also be incorporated in a camera that recognizes the movement of a human body or the like.

  Hereinafter, the details of the imaging lens 10 of the embodiment will be described with reference to FIG. 1. The imaging lens 10 illustrated in FIG. 1 has the same configuration as an imaging lens 10A of Example 1 described later.

  The illustrated imaging lens 10 is an imaging lens that forms a subject image on the imaging surface I of the imaging element 51.

  The imaging lens 10 substantially includes a positive first lens L1, a positive second lens L2, and a third lens L3 in order from the object side. The first lens L1 is a glass lens and has a spherical surface or an aspherical surface on at least one surface. The first lens L1 having a large influence is made of glass in order to suppress focal position fluctuations and performance deterioration during temperature changes. The first lens L1 more preferably has spherical surfaces on both sides. By forming the first lens L1 with a spherical surface, a molding die is unnecessary, and the cost can be reduced. The second and third lenses L2 and L3 are resin lenses, and each has at least one aspheric surface. By making the second and third lenses L2, L3 made of resin, cost reduction is realized. Note that the third lens L3 may be any of negative, positive, and almost non-power.

  An aperture stop ST is provided between the first lens L1 and the second lens L2. With this arrangement, it is easy to correct lateral chromatic aberration. Also, with this arrangement, distortion aberration can be easily controlled, so that the distortion shape can easily be a natural shape having no inflection point.

  A filter F that is a parallel plate can be disposed between the lens unit 40 and the sensor unit 50. The filter F is a bandpass filter that transmits, for example, near infrared light (700 nm to 1000 nm, preferably 800 nm to 900 nm), and prevents light other than near infrared light from entering.

The imaging lens 10 satisfies the following conditional expressions (1) to (6).
1.7 ≦ nd1 ≦ 2.2 (1)
10 ≦ νd1 ≦ 50 (2)
1e-6 ≦ α1 ≦ 1.2e-5 (3)
0.1 ≦ d1 / TL ≦ 0.25 (4)
−0.7 ≦ f2 / f3 ≦ 0.2 (5)
0.31 ≦ Y / TL ≦ 0.7 (6)
Here, the value nd1 is the d-line refractive index of the first lens L1, the value νd1 is the Abbe number of the first lens L1, the value α1 is the linear expansion coefficient per 1K in the first lens L1, and the value d1 Is the axial thickness of the first lens L1, the value TL is the total optical length, the value f2 is the focal length of the second lens L2, the value f3 is the focal length of the third lens L3, and the value Y is the maximum The image height. Note that the optical total length is the air conversion length when a parallel plate (for example, the filter F) is disposed between the third lens L3 and the image plane (corresponding to the imaging plane I). In the conditional expression (3), a power of 10 (for example, 1.2 × 10 ⁻⁵ ) is expressed using e (for example, 1.2e−5).

  By using a lens material satisfying the conditional expressions (1) and (2) for the first lens L1 having a high power, the optical total length can be shortened and the radius of curvature can be increased, thereby generating spherical aberration and coma. Can be suppressed. The first lens L1 that satisfies the conditional expressions (1) and (2) is a high refraction / high dispersion material and easily causes chromatic aberration. However, the imaging lens 10 forms near-infrared light. Therefore, it is not necessary to prioritize chromatic aberration correction over other aberration corrections. Further, by satisfying conditional expression (3), it is possible to reduce the power change of the lens at the time of high temperature or low temperature change, and to suppress the focal position shift. Moreover, it becomes easy to suppress curvature of field by falling below the upper limit of the value d1 / TL of conditional expression (4). On the other hand, exceeding the lower limit of the value d1 / TL of conditional expression (4) makes it easy to correct spherical aberration. In an optical system in the near infrared (700 nm to 1000 nm, preferably in the vicinity of 800 nm to 900 nm), correction of spherical aberration and coma aberration is more important than chromatic aberration compared to an optical system for visible light. Therefore, by using a high refractive / high dispersion material for the first lens L1 so as to satisfy the conditional expressions (1) to (4), the curvature is relaxed and the thickness is set appropriately, thereby shortening the overall length and aberration performance. , Productivity can be achieved. In addition, by satisfying conditional expression (5), the power change of the second and third lenses L2 and L3 does not increase at the time of temperature change, and it is possible to suppress the occurrence of focal position shift and field curvature. A decrease in resolution can be prevented. In other words, by appropriately defining the focal length ratio of the second and third lenses L2 and L3, it is configured to cancel out the performance fluctuation at the time of temperature change. In addition, by falling below the upper limit of the value Y / TL of the conditional expression (6), the power of each lens is not excessively strong, and various aberrations are generated when the temperature changes to prevent the resolution performance from deteriorating significantly. Therefore, it is possible to prevent the productivity from being lowered. On the other hand, exceeding the lower limit of the value Y / TL of the conditional expression (6) does not increase the size of the lenses L1 to L3, maintains the degree of freedom of installation, and does not limit the equipment on which the imaging lens 10 can be mounted.

Conditional expressions (4) and (6) are more preferably set to the following ranges.
0.12 ≦ d1 / TL ≦ 0.25 (4) ′
0.31 ≦ Y / TL ≦ 0.45 (6) ′

The imaging lens 10 preferably satisfies the following conditional expressions (7) to (9) in addition to the conditional expressions (1) to (6).
1.52 ≦ nd2 ≦ 1.7 (7)
1.52 ≦ nd3 ≦ 1.7 (8)
| Nd2-nd3 | ≦ 0.05 (9)
Here, the value nd2 is the d-line refractive index of the second lens L2, and the value nd3 is the d-line refractive index of the third lens L3.

  By using a lens material satisfying conditional expressions (7) to (9) for the second and third lenses L2 and L3, the Petzval sum can be reduced and the astigmatic difference can be suppressed.

Moreover, it is desirable that the imaging lens 10 satisfies the following conditional expression (10) in addition to the conditional expressions (1) to (6).
Fn ≦ 3.5 (10)
Here, the value Fn is the F number of the entire system.

  When the conditional expression (10) is satisfied, the power of each of the lenses L1 to L3 increases, so that the spherical aberration and the coma increase, and the focus position shift and the field curvature fluctuation at the time of temperature change tend to become larger. Therefore, when the conditional expression (10) is satisfied, the effects of the conditional expressions (1) to (6) are more exhibited.

The conditional expression (10) is more preferably set to the following range.
Fn ≦ 2.8 (10) ′

In addition, it is desirable that the imaging lens 10 satisfies the following conditional expression (11) in addition to the conditional expressions (1) to (6).
1 ≦ f1 / f ≦ 2 (11)
Here, the value f1 is the focal length of the first lens L1, and the value f is the focal length of the entire system.

  When the value f1 / f of the conditional expression (11) is below the upper limit, spherical aberration and coma are sufficiently corrected. On the other hand, the axial chromatic aberration can be easily corrected by exceeding the lower limit of the value f1 / f of the conditional expression (11).

The conditional expression (11) is more preferably set to the following range.
1.2 ≦ f1 / f ≦ 2 (11) ′

Moreover, it is desirable that the imaging lens 10 satisfies the following conditional expression (12) in addition to the conditional expressions (1) to (6).
0.6 ≦ f1 / f2 ≦ 2.5 (12)
Here, the value f1 is the focal length of the first lens L1, and the value f2 is the focal length of the second lens L2.

  By falling below the upper limit of the value f1 / f2 of the conditional expression (12), it is possible to prevent the focal position shift from occurring due to the power change of the second lens L2 being excessively large when the temperature changes. On the other hand, the axial chromatic aberration can be easily corrected by exceeding the lower limit of the value f1 / f2 of the conditional expression (12).

The conditional expression (12) is more preferably set to the following range.
1.1 ≦ f1 / f2 ≦ 2.3 (12) ′

Moreover, it is desirable that the imaging lens 10 satisfies the following conditional expression (13) in addition to the conditional expressions (1) to (6).
0.8 ≦ f1 / f23 ≦ 5 (13)
Here, the value f1 is the focal length of the first lens L1, and the value f23 is the combined focal length of the second and third lenses L2 and L3.

  By falling below the upper limit of the value f1 / f23 of the conditional expression (13), the size of the lenses L1 to L3 does not become too large, and the degree of freedom of installation is maintained, so that the device on which the imaging lens 10 can be mounted is not limited. On the other hand, by exceeding the lower limit of the value f1 / f23 of the conditional expression (13), the power of the first lens L1 does not become too large, and the spherical aberration and the coma aberration can be sufficiently corrected.

The conditional expression (13) is more preferably set to the following range.
0.8 ≦ f1 / f23 ≦ 1.5 (13) ′

Moreover, it is desirable that the imaging lens 10 satisfies the following conditional expression (14) in addition to the conditional expressions (1) to (6).
−1.9 ≦ (L1R1 + L1R2) / (L1R1−L1R2) ≦ −1 (14)
Here, the value L1R1 is the curvature radius of the object side surface of the first lens L1, and the value L1R2 is the curvature radius of the image side surface of the first lens L1. The lens shape satisfying the conditional expression (14) is, for example, that one lens surface is a flat surface and the other lens surface is a convex surface or a concave surface, or both lens surfaces are convex surfaces or concave surfaces.

  The spherical aberration can be easily corrected by falling below the upper limit of the value (L1R1 + L1R2) / (L1R1−L1R2) in the conditional expression (14). On the other hand, astigmatism can be suppressed by exceeding the lower limit of the value (L1R1 + L1R2) / (L1R1−L1R2) in conditional expression (14).

The conditional expression (14) is more preferably set to the following range.
−1.9 ≦ (L1R1 + L1R2) / (L1R1−L1R2) ≦ −1.5 (14) ′

  With the imaging lens 10 described above, various sensing can be performed by imaging near-infrared light. By using near-infrared light, the imaging lens 10 can stably exhibit performance regardless of the bright and dark environment. Further, by configuring the imaging lens 10 to include the positive first lens L1, the positive second lens L2, and the third lens L3 from the object side, the configuration is close to the telephoto type, and the total optical length can be easily shortened. . In addition, the first lens L1 is made of glass and the second and third lenses L3 are made of resin, so that performance fluctuations can be suppressed even when the environmental temperature changes. Stable resolution performance can be exhibited even in a moderate temperature environment.

〔Example〕
Examples of the imaging lens of the present invention will be shown below. Symbols used in each example are as follows. The unit of length is “mm”, and the unit of angle is “° (degrees)”. Further, the focal length Fl has a calculation wavelength of 950 nm.
Fl: Focal length of the entire imaging lens system Fno: F number w: Half angle of view ymax: Maximum image height TL: Optical total length (distance on the optical axis from the lens surface closest to the object side to the imaging surface)
BF: Back focus R: Radius of curvature D: Axial distance nd: Refractive index νd of lens material with respect to d-line: Abbe number of lens material

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ：曲率半径
Ｋ：円錐定数 In each embodiment, the surface described with “*” after each surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and the X axis in the optical axis direction. The height in the direction perpendicular to the optical axis is h, and is expressed by the following “Equation 1”.

However,
Ai: i-th order aspheric coefficient R: radius of curvature K: conic constant

[Example 1]
Data of the lens surface of the imaging lens of Example 1 is shown in Table 1 below. In Table 1 below, the surface number is represented by “Surf.N”, the aperture stop ST is represented by “ST”, the infinity is represented by “INF”, the object surface is represented by “object”, and the imaging surface I (or image plane) is represented by “image”. “*” Attached to the surface number represents an aspherical surface.
[Table 1]
Surf.NR (mm) D (mm) nd νd
object INF 660.000
1 6.118 1.137 1.91082 35.25
2 (ST) 22.151 1.587
3 * -2.456 1.877 1.54440 55.89
4 * -1.694 0.200
5 * 5.803 1.990 1.54440 55.89
6 * 2.629 2.248
image INF

The aspheric coefficients of the lens surfaces of Example 1 are shown in Table 2 below. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is represented using e (for example, 2.5e-02).
[Table 2]
Third side
K = -4.9940e-001, A4 = -2.0122e-002, A6 = 1.1780e-002, A8 = -1.5542e-002,
A10 = 7.9382e-003, A12 = -1.3242e-003, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
4th page
K = -3.6452e + 000, A4 = -6.1685e-002, A6 = 2.2789e-002, A8 = -7.5424e-003,
A10 = 1.2976e-003, A12 = -8.3285e-005, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
5th page
K = -3.9475e + 001, A4 = 1.8755e-002, A6 = -4.6788e-003, A8 = 6.6919e-004,
A10 = -4.6793e-005, A12 = 1.2705e-006, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
6th page
K = -6.9480e + 000, A4 = -3.3850e-003, A6 = 3.3928e-004, A8 = -1.7154e-004,
A10 = 2.4108e-005, A12 = -1.0191e-006, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000

The focal length (Fl), F number (Fno), half field angle (w), maximum image height (ymax), optical total length (TL), and back focus (BF) of the entire imaging lens system of Example 1 are as follows. Table 3 shows.
[Table 3]
Fl: 5.190 (mm)
Fno.:2.600
w: 33.275 (°)
ymax: 3.150 (mm)
TL: 8.913 (mm)
BF: 2.122 (mm)

Table 4 below shows the focal lengths of the lenses constituting the imaging lens of Example 1. Each focal length has a calculated wavelength of 950 nm (the same applies to the following examples).
[Table 4]
Lens number Focal length (mm)
1 9.223
2 5.495
3 -11.506

  FIG. 2 is a cross-sectional view of the imaging lens 10A of the first embodiment. The imaging lens 10A according to the first exemplary embodiment includes, in order from the object side, a positive first lens L1, a positive second lens L2, and a negative third lens L3. The first lens L1 is a glass lens, and the second lens L2 and the third lens L3 are resin lenses. The optical surfaces of the first lens L1 are both spherical. The optical surfaces of the second and third lenses L2, L3 are both aspheric. An aperture stop ST is disposed between the first lens L1 and the second lens L2 (specifically, on the image side surface of the first lens L1). A filter F having an appropriate thickness is disposed between the third lens L3 and the image sensor 51. The filter F is a parallel plate assuming a band-pass filter, a seal glass of the image sensor 51, and the like. Reference numeral I denotes an imaging surface that is a projection surface of the imaging element 51 (the same applies to the following embodiments).

  3A to 3C are aberration diagrams (spherical aberration, astigmatism, and distortion aberration) of the imaging lens 10A. In the spherical aberration diagram, Fn2.6 represents an F number. In the astigmatism diagrams, the solid line represents the sagittal image plane and the dotted line represents the tangential image plane (the same applies to the following examples).

  4A to 4E show the case where the image height of the imaging lens 10A is changed (specifically, the image height ratios 0.0, 0.2, 0.4, 0.6, and 0). .8) lateral aberration (in the tangential plane and in the sagittal plane) is shown (the same applies to the following examples).

[Example 2]
The data of the lens surface of the imaging lens of Example 2 is shown in Table 5 below.
[Table 5]
Surf.NR (mm) D (mm) nd νd
object INF INF
1 * 4.390 1.919 1.77250 49.62
2 * 17.107 0.100
3 (ST) INF 1.328
4 * -2.084 1.942 1.58550 29.91
5 * -2.007 0.200
6 * 3.367 1.990 1.54440 55.89
7 * 2.597 1.542
image INF

The aspherical coefficients of the lens surfaces of Example 2 are shown in Table 6 below.
[Table 6]
First side
K = 1.5038e + 000, A4 = -2.2667e-003, A6 = -1.4519e-005, A8 = -1.1723e-004,
A10 = 1.8795e-006, A12 = 0.0000e + 000, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
Second side
K = -1.3101e + 003, A4 = 2.5145e-002, A6 = -3.4630e-002, A8 = 2.5694e-002,
A10 = -8.4135e-003, A12 = 0.0000e + 000, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
4th page
K = 7.5217e-001, A4 = -4.9557e-003, A6 = -2.1153e-002, A8 = 1.4280e-002,
A10 = -5.3518e-003, A12 = 6.6138e-004, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
5th page
K = -4.5191e-001, A4 = -2.8245e-002, A6 = 1.3747e-002, A8 = -4.2107e-003,
A10 = 6.5194e-004, A12 = -4.4321e-005, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
6th page
K = -1.4106e + 001, A4 = -1.4943e-003, A6 = 2.0180e-003, A8 = -3.6518e-004,
A10 = 3.1288e-005, A12 = -1.1597e-006, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
7th page
K = -8.6082e-001, A4 = -3.0300e-002, A6 = 3.1635e-003, A8 = -1.6371e-004,
A10 = -3.6245e-006, A12 = 3.5302e-007, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000

Table 7 below shows the focal length, F number, half angle of view, maximum image height, total optical length, and back focus of the entire imaging lens of Example 2.
[Table 7]
Fl: 5.069 (mm)
Fno.:2.000
w: 28.502 (°)
ymax: 2.800 (mm)
TL: 8.932 (mm)
BF: 1.453 (mm)

Table 8 below shows the focal lengths of the lenses constituting the imaging lens of Example 2.
[Table 8]
Lens number Focal length (mm)
1 7.323
2 9.445
3 -212.411

  FIG. 5 is a cross-sectional view of the imaging lens 10B of the second embodiment. The imaging lens 10B of Example 2 includes, in order from the object side, a positive first lens L1, a positive second lens L2, and a negative third lens L3. The first lens L1 is a glass lens, and the second lens L2 and the third lens L3 are resin lenses. The optical surface of the first lens L1 has both aspheric surfaces. The optical surfaces of the second and third lenses L2, L3 are both aspheric. An aperture stop ST is disposed between the first lens L1 and the second lens L2. A filter F having an appropriate thickness is disposed between the third lens L3 and the image sensor 51. The filter F is a parallel plate assuming a band-pass filter, a seal glass of the image sensor 51, and the like.

  6A to 6C are aberration diagrams (spherical aberration, astigmatism, and distortion aberration) of the imaging lens 10B.

  FIGS. 7A to 7E show transverse aberration (in the tangential plane and in the sagittal plane) when the image height of the imaging lens 10B is changed.

Example 3
Data on the lens surface of the imaging lens of Example 3 is shown in Table 9 below.
[Table 9]
Surf.NR (mm) D (mm) nd νd
object INF INF
1 5.906 1.552 2.00100 29.13
2 (ST) 21.838 1.820
3 * -3.079 2.080 1.54440 55.89
4 * -1.491 0.200
5 * 7.531 1.562 1.54440 55.89
6 * 1.967 1.472
image INF

The aspheric coefficients of the lens surfaces of Example 3 are shown in Table 10 below.
[Table 10]
Third side
K = 7.4293e-002, A4 = -2.6845e-002, A6 = 1.2571e-002, A8 = -1.5988e-002,
A10 = 7.2999e-003, A12 = -1.2345e-003, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
4th page
K = -3.3643e + 000, A4 = -6.1544e-002, A6 = 2.2720e-002, A8 = -7.5593e-003,
A10 = 1.2827e-003, A12 = -8.7677e-005, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
5th page
K = -4.5545e + 001, A4 = 1.5078e-002, A6 = -4.5020e-003, A8 = 6.8638e-004,
A10 = -4.6898e-005, A12 = 9.1785e-007, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
6th page
K = -4.8968e + 000, A4 = -5.0413e-003, A6 = 1.5861e-004, A8 = -1.5008e-004,
A10 = 2.5224e-005, A12 = -1.1919e-006, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000

Table 11 below shows the focal length, F-number, half angle of view, maximum image height, optical total length, and back focus of the entire imaging lens of Example 3.
[Table 11]
Fl: 4.904 (mm)
Fno.:2.600
w: 30.853 (°)
ymax: 3.150 (mm)
TL: 8.572 (mm)
BF: 1.358 (mm)

Table 12 below shows the focal lengths of the lenses constituting the imaging lens of Example 3.
[Table 12]
Lens number Focal length (mm)
1 7.963
2 3.714
3 -5.522

  FIG. 8 is a cross-sectional view of the imaging lens 10C of the third embodiment. The imaging lens 10C of Example 3 includes, in order from the object side, a positive first lens L1, a positive second lens L2, and a negative third lens L3. The first lens L1 is a glass lens, and the second lens L2 and the third lens L3 are resin lenses. The optical surfaces of the first lens L1 are both spherical. The optical surfaces of the second and third lenses L2, L3 are both aspheric. An aperture stop ST is disposed between the first lens L1 and the second lens L2 (specifically, on the image side surface of the first lens L1). A filter F having an appropriate thickness is disposed between the third lens L3 and the image sensor 51. The filter F is a parallel plate assuming a band-pass filter, a seal glass of the image sensor 51, and the like.

  9A to 9C are aberration diagrams (spherical aberration, astigmatism, and distortion aberration) of the imaging lens 10C.

  10A to 10E show lateral aberrations (in the tangential plane and in the sagittal plane) when the image height of the imaging lens 10C is changed.

Example 4
Data of the lens surface of the imaging lens of Example 4 is shown in Table 13 below.
[Table 13]
Surf.NR (mm) D (mm) nd νd
object INF 500.000
1 * 4.485 1.916 1.77250 49.62
2 * (ST) 20.195 1.619
3 * -1.970 1.562 1.58550 29.91
4 * -1.967 0.200
5 * 3.060 1.763 1.53550 56.00
6 * 2.640 1.668
image INF

The aspheric coefficients of the lens surfaces of Example 4 are shown in Table 14 below.
[Table 14]
First side
K = 1.0599e + 000, A4 = -1.6265e-003, A6 = 1.7815e-005, A8 = -6.7414e-005,
A10 = -6.8342e-008, A12 = 0.0000e + 000, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
Second side
K = -2.4605e + 003, A4 = 3.0739e-002, A6 = -5.2625e-002, A8 = 5.2496e-002,
A10 = -2.2110e-002, A12 = 0.0000e + 000, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
Third side
K = 4.4158e-001, A4 = 4.4327e-003, A6 = -2.3396e-002, A8 = 1.4962e-002,
A10 = -4.5827e-003, A12 = 8.6769e-004, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
4th page
K = -3.7738e-001, A4 = -2.9414e-002, A6 = 1.3947e-002, A8 = -4.2646e-003,
A10 = 6.7690e-004, A12 = -3.5015e-005, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
5th page
K = -1.0543e + 001, A4 = -6.1386e-003, A6 = 2.4524e-003, A8 = -4.0706e-004,
A10 = 3.6501e-005, A12 = -1.7439e-006, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000
6th page
K = -8.8316e-001, A4 = -3.2951e-002, A6 = 3.1160e-003, A8 = -1.6281e-004,
A10 = -3.5184e-006, A12 = 3.5577e-007, A14 = 0.0000e + 000, A16 = 0.0000e + 000,
A18 = 0.0000e + 000, A20 = 0.0000e + 000

Table 15 below shows the focal length, F-number, half angle of view, maximum image height, optical total length, and back focus of the entire imaging lens of Example 4.
[Table 15]
Fl: 5.161 (mm)
Fno.:2.600
w: 30.238 (°)
ymax: 3.150 (mm)
TL: 8.641 (mm)
BF: 1.582 (mm)

Table 16 below shows the focal lengths of the lenses constituting the imaging lens of Example 4.
[Table 16]
Lens number Focal length (mm)
1 7.234
2 12.001
3 82.044

  FIG. 11 is a cross-sectional view of the imaging lens 10D of the fourth embodiment. The imaging lens 10D of Example 4 includes, in order from the object side, a positive first lens L1, a positive second lens L2, and a positive third lens L3. The first lens L1 is a glass lens, and the second lens L2 and the third lens L3 are resin lenses. The optical surface of the first lens L1 has both aspheric surfaces. The optical surfaces of the second and third lenses L2, L3 are both aspheric. An aperture stop ST is disposed between the first lens L1 and the second lens L2 (specifically, on the image side surface of the first lens L1). A filter F having an appropriate thickness is disposed between the third lens L3 and the image sensor 51. The filter F is a parallel plate assuming a band-pass filter, a seal glass of the image sensor 51, and the like.

  12A to 12C are aberration diagrams (spherical aberration, astigmatism, and distortion aberration) of the imaging lens 10D.

  FIGS. 13A to 13E show transverse aberration (in the tangential plane and in the sagittal plane) when the image height of the imaging lens 10D is changed.

For reference, Table 17 below summarizes the values of Examples 1 to 4 corresponding to the conditional expressions (1) to (14).
[Table 17]

  Although the imaging lens according to the embodiment has been described above, the imaging lens 10 according to the present invention is not limited to the above embodiment. For example, the imaging lens 10 may further include another optical element (for example, a lens) that has substantially no power.

  In the imaging apparatus 100, the filter F is disposed between the lens unit 40 and the sensor unit 50. However, the filter F may not be provided.

AX ... Optical axis, F ... Filter, I ... Imaging surface, L1, L2, L3 ... Lens, OP ... Aperture, 10, 10A, 10B, 10C, 10D ... Imaging lens, 30 ... Camera module, 40 ... Lens unit, 41 DESCRIPTION OF SYMBOLS ... 50 ... Sensor part 51 ... Image sensor 51a ... Photoelectric conversion part 52 ... Substrate 60 ... Processing part 61 ... Drive part 62 ... Input part 63 ... Storage part 64 ... Display part 68 ... Control unit, 100 ... Imaging device

Claims (11)

An imaging lens for imaging near-infrared light,
In order from the object side, the first lens is substantially composed of a first positive lens, a second positive lens, and a third lens.
The first lens is made of glass,
The second and third lenses are made of resin,
The second and third lenses each have at least one aspheric surface,
An imaging lens satisfying the following conditional expression:
1.7 ≦ nd1 ≦ 2.2 (1)
10 ≦ νd1 ≦ 50 (2)
1e-6 ≦ α1 ≦ 1.2e-5 (3)
0.1 ≦ d1 / TL ≦ 0.25 (4)
−0.7 ≦ f2 / f3 ≦ 0.2 (5)
0.31 ≦ Y / TL ≦ 0.7 (6)
here,
nd1: d-line refractive index νd1: first Abbe number α1: linear expansion coefficient per 1K of the first lens d1: axial thickness TL of the first lens: optical total length f2: the above Focal length f3 of the second lens: Focal length Y of the third lens Y: Maximum image height The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
1.52 ≦ nd2 ≦ 1.7 (7)
1.52 ≦ nd3 ≦ 1.7 (8)
| Nd2-nd3 | ≦ 0.05 (9)
here,
nd2: d-line refractive index of the second lens nd3: d-line refractive index of the third lens The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
Fn ≦ 3.5 (10)
here,
Fn: F number of all systems The imaging lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
1 ≦ f1 / f ≦ 2 (11)
here,
f1: Focal length of the first lens f: Focal length of the entire system The imaging lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied.
0.6 ≦ f1 / f2 ≦ 2.5 (12)
here,
f1: Focal length of the first lens f2: Focal length of the second lens The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.8 ≦ f1 / f23 ≦ 5 (13)
here,
f1: Focal length of the first lens f23: Composite focal length of the second and third lenses   The imaging lens according to claim 1, wherein the first lens has spherical surfaces on both sides.   The imaging lens according to claim 1, further comprising an aperture stop between the first lens and the second lens. The imaging lens according to any one of claims 1 to 8, wherein the following conditional expression is satisfied.
−1.9 ≦ (L1R1 + L1R2) / (L1R1−L1R2) ≦ −1 (14)
here,
L1R1: radius of curvature of the object side surface of the first lens L1R2: radius of curvature of the image side surface of the first lens The imaging lens according to any one of claims 1 to 9,
A lens barrel for holding the imaging lens;
An imaging lens unit comprising: The imaging lens according to any one of claims 1 to 9,
An image sensor on which an image by the imaging lens is projected;
An imaging apparatus comprising:

Images