Imaging lens and imaging device

Abstract

In the imaging lens, wide-angle and miniaturization are achieved while suitably correcting aberrations such as chromatic aberration. [Solution] The imaging lens comprises a lens system in which, in order from the object side toward the image plane side, a first lens having negative refractive power with a concave surface facing toward the image plane side, a second lens having positive refractive power with a convex surface facing toward the object side, an aperture, and a third lens having positive refractive power with a convex surface facing toward the image plane side are arranged. The lens system satisfies a predetermined condition when the focal length on the d line of the lens system is f, the focal length of the first lens is f1, the Abbe number of the first lens is νd1, the Abbe number of the second lens is νd2, the Abbe number of the third lens is νd3, the center thickness of the first lens is D1, the distance of the lens system from the object-side surface of the first lens to the image plane is TTL1, and the maximum image height is ImgH.

Description

Technical Field

[0001] The present disclosure relates to an imaging lens and an imaging device.

Background Art

[0002] Miniaturization and wide-angleization of an imaging lens are required in imaging devices for various applications using the imaging lens. For example, in Patent Document 1, a lens configuration for miniaturizing and wide-angleizing an imaging lens is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the lens configuration of Patent Document 1, when further miniaturizing or wide-angleizing the imaging lens, it is difficult to suitably correct aberrations such as chromatic aberration.

[0005] The present disclosure has been made in view of the above, and an object thereof is to provide an imaging lens and an imaging device capable of suitably correcting aberrations such as chromatic aberration while realizing wide-angleization and miniaturization.

Means for Solving the Problems

[0006] The imaging lens of this disclosure comprises a lens system in which, in order from the object side toward the image plane side, a first lens having a negative refractive power with a concave surface facing toward the image plane side, a second lens having a positive refractive power with a convex surface facing toward the object side, an aperture, and a third lens having a positive refractive power with a convex surface facing toward the image plane side are arranged. The lens system satisfies the following conditions (1) to (6), where f is the focal length of the lens system on the d line, f1 is the focal length of the first lens, νd1 is the Abbe number of the first lens, νd2 is the Abbe number of the second lens, νd3 is the Abbe number of the third lens, D1 is the center thickness of the first lens, TTL1 is the distance of the lens system from the object-side surface of the first lens to the image plane, and ImgH is the maximum image height. -1.0 <f1 / f<-0.45 ···(1) νd1>40 ···(2) νd1 / νd2>1.5 ···(3) νd3>40 ···(4) 0.15 <D1 / f<0.5 ···(5) 2.5 <TTL1 / ImgH<4 ···(6)

[0007] Furthermore, the imaging device of this disclosure includes the imaging lens described above. [Effects of the Invention]

[0008] The imaging lens and imaging device of this disclosure provide an imaging lens and imaging device that can suitably correct aberrations such as chromatic aberration while achieving wider angle and miniaturization. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram showing the configuration of an imaging device according to one embodiment. [Figure 2] Figure 2 shows the configuration of the imaging lens according to Example 1. [Figure 3] Figure 3 is an aberration diagram of the imaging lens according to Example 1. [Figure 4] Figure 4 shows the configuration of the imaging lens according to Example 2. [Figure 5] Figure 5 is an aberration diagram of the imaging lens according to Embodiment 2. [Figure 6] Figure 6 is a diagram showing the configuration of the imaging lens according to Embodiment 3. [Figure 7] Figure 7 is an aberration diagram of the imaging lens according to Embodiment 3. [Figure 8] Figure 8 is a diagram showing the configuration of the imaging lens according to Embodiment 4. [Figure 9] Figure 9 is an aberration diagram of the imaging lens according to Embodiment 4. [Figure 10] Figure 10 is a diagram showing the configuration of the imaging lens according to Embodiment 5. [Figure 11] Figure 11 is an aberration diagram of the imaging lens according to Embodiment 5. [Figure 12] Figure 12 is a diagram showing the configuration of the imaging lens according to Embodiment 6. [Figure 13] Figure 13 is an aberration diagram of the imaging lens according to Embodiment 6.

MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, an embodiment according to the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are illustrative and should not be construed as limiting.

[0011] Figure 1 is a diagram showing the configuration of an imaging device 100 according to an embodiment. The imaging device 100 shown in Figure 1 includes an imaging lens 110, an image acquisition unit 120, a processor 130, a memory 140, and an input / output unit 150. Examples of the imaging device 100 include, but are not limited to, those used in smartphones, distance measurement sensors, and VR (Virtual Reality) goggles, or those used as medical imaging devices such as endoscope devices.

[0012] The imaging lens 110 allows light reflected from an object serving as a subject to pass through and forms an optical image of the object on the image plane IA. Specifically, the imaging lens 110 includes a lens system 10 and an imaging element 50.

[0013] The lens system 10 includes, in order from the object side serving as the subject toward the image plane IA side of the imaging device 50, a first lens L1, a second lens L2, an aperture STO, and a third lens L3.

[0014] The first lens L1 has a surface S3 on the object side and a concave surface S4 on the image plane IA side. The first lens L1 is a lens having a negative refractive power with the concave surface facing the image plane IA side.

[0015] The second lens L2 has a convex surface S5 on the object side and a surface S6 on the image plane IA side. The second lens L2 is a lens having a positive refractive power with the convex surface facing the object side.

[0016] The aperture STO adjusts the amount of light incident on the third lens L3 by changing the size of the opening in the central portion.

[0017] The third lens L3 has a surface S8 on the object side and a convex surface S9 on the image plane IA side. The third lens L3 is a lens having a positive refractive power with the convex surface facing the image plane IA side.

[0018] Each of the first lens L1, the second lens L2, and the third lens L3 may be a single lens formed integrally, or may be a composite lens formed by bonding a plurality of lenses. Also, the material used for each of the first lens L1, the second lens L2, and the third lens L3 can be any material according to the purpose and application. Further, the first lens L1, the second lens L2, and the third lens L3 are formed using, for example, a resin such as plastic. Other detailed configurations of the lens system 10 will be described later.

[0019] A windshield 20 is positioned on the object side of the lens system 10. The windshield 20 is formed from any material depending on the application and purpose. For example, if the imaging device 100 is a medical imaging device such as an endoscope, the windshield 20 is not limited to, but a biocompatible material such as synthetic quartz glass is used. It is also possible to omit the windshield 20 depending on the purpose and application of the imaging device 100. For example, if the imaging device 100 is a VR goggle, the windshield 20 can be omitted.

[0020] A light-transmitting member 30 is positioned on the image plane IA side of the lens system 10. The light-transmitting member 30 can also be formed as a filter glass that transmits visible light by applying an infrared-cutting coating agent that blocks infrared rays to the object side or the image plane side. In this case, the light-transmitting member 30 functions as a bandpass filter that transmits visible light with a wavelength in the range of, for example, 400 to 700 nm from the light passing through the lens system 10. The light-transmitting member 30 is formed using, for example, quartz glass or plastic, although this is not limited to this configuration. The light-transmitting member 30 may also be omitted depending on the purpose and application of the imaging device 100.

[0021] A cover glass 40 is placed on the image plane IA side of the light-transmitting member 30. The cover glass 40 protects the image plane IA, which is the sensor surface of the image sensor 50. The cover glass 40 is formed using, for example, borosilicate glass, although this is not limited to the cover glass. Depending on the purpose and application of the imaging device 100, it is also possible to omit the cover glass 40 from the imaging device 100.

[0022] The image sensor 50 is an optical sensor that detects light illuminating the image plane IA and converts it into an electrical signal to acquire an optical image of an object. The image sensor 50 is not limited to, but may include, for example, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor. The image sensor 50 also includes, not limited to, a light-receiving element such as a photodiode on the image plane IA.

[0023] The image acquisition unit 120 generates an image of an object from the optical image acquired by the imaging lens 110.

[0024] The processor 130 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and provides overall control of the imaging device 100.

[0025] The memory 140 includes, for example, RAM (Random Access Memory) or ROM (Read Only Memory) and stores information used for information processing performed by the processor 130.

[0026] The input / output unit 150 forms an interface that allows the user or robot to input commands or output images, etc.

[0027] The image acquisition unit 120, processor 130, memory 140, and input / output unit 150 are connected via a bus, enabling them to transmit data such as images or control signals to each other.

[0028] As described above, the lens system 10 comprises, in order from the object side toward the image plane IA side, a first lens L1 having a negative refractive power with its concave surface facing toward the image plane IA side, a second lens L2 having a positive refractive power with its convex surface facing toward the object side, an aperture, and a third lens L3 having a positive refractive power with its convex surface facing toward the image plane IA side. The lens system 10 satisfies the following conditions (1) to (6) when the focal length of the lens system 10 on the d line is f, the focal length of the first lens L1 is f1, the Abbe number of the first lens L1 is νd1, the Abbe number of the second lens L2 is νd2, the Abbe number of the third lens L3 is νd3, the center thickness of the first lens L1 is D1, the distance of the lens system 10 from the object-side surface S3 of the first lens L1 to the image plane IA is TTL1, and the maximum image height is ImgH. -1.0 <f1 / f<-0.45 ···(1) νd1>40 ···(2) νd1 / νd2>1.5 ···(3) νd3>40 ···(4) 0.15 <D1 / f<0.5 ···(5) 2.5 <TTL1 / ImgH<4 ···(6)

[0029] By satisfying the above conditions (1) to (6), the lens system 10 can guide the off-axis light rays, which are greatly refracted by the negative first lens L1, to the image plane IA at a gentle angle by the positive second lens L2 and third lens L3, which are positioned before and after the aperture STO.

[0030] Furthermore, by positioning the aperture STO between the second lens L2 and the third lens L3, the front element diameter can be reduced while minimizing the amount of off-axis light cut-off, thus easily ensuring sufficient peripheral illumination. In other words, the imaging lens 110 can be made wider and smaller.

[0031] Conditional equation (1) defines the relationship between the focal length f1 of the first lens L1 on the d line and the focal length f of the lens system 10 on the d line, using the focal length ratio f1 / f. By making the focal length ratio f1 / f greater than the lower limit of conditional equation (1), the negative refractive power of the first lens L1 becomes moderately strong, allowing a wide angle of view to be secured at a short distance TTL1. On the other hand, by making the focal length ratio f1 / f smaller than the upper limit of conditional equation (1), it is possible to prevent the negative refractive power of the first lens L1 from becoming excessively strong, and as a result of correcting off-axis aberrations, good resolution performance can be obtained.

[0032] The lower limit of conditional equation (1) is -1.0, preferably -0.9. The upper limit of conditional equation (1) is -0.45, preferably -0.55. Therefore, the ratio of focal lengths f1 / f may be, for example, in the range greater than -0.9 and less than -0.45 or -0.55, or in the range greater than -1.0 and less than -0.45.

[0033] Conditional equation (2) specifies the lower limit of the Abbe number νd1 at the d-line of the first lens L1. By forming the first lens L1, which has a high off-axis ray height, using a material whose Abbe number νd1 is greater than the lower limit, the occurrence of chromatic aberration of off-axis rays can be suppressed. The lower limit of conditional equation (2) is 40.

[0034] Conditional equation (3) specifies a lower limit for the ratio νd1 / νd2 of the Abbe number νd1 of the first lens L1 on the d line to the Abbe number νd2 of the second lens L2 on the d line. The materials forming the first lens L1 and the second lens L2 are selected such that the Abbe number νd1 of the first lens L1 is greater than the Abbe number νd2 of the second lens L2, and as shown in conditional equation (1), the Abbe number νd1 of the first lens L1 exceeds 40. The first lens L1 and the second lens L2 are positioned on the object side of the aperture STO, and by setting the ratio νd1 / νd2 of the Abbe numbers to exceed the lower limit, chromatic aberration can be suitably corrected for the wavelength range of visible light, and a lens system 10 with suppressed chromatic aberration can be realized. The lower limit of conditional equation (3) is 1.5, preferably 1.8.

[0035] Furthermore, condition (4) specifies the lower limit of the Abbe number νd3 at the d line of the third lens L3. When only the third lens L3 is placed on the image plane IA side of the aperture STO, chromatic aberration can be suppressed by forming the third lens L3, which has positive refractive power, using a material in which the Abbe number νd3 is greater than the lower limit. The lower limit of condition (4) is 40.

[0036] Conditional equation (5) defines the relationship between the central thickness D1 of the first lens L1 and the focal length f at the d-line of the lens system 10 using the ratio D1 / f of the central thickness D1 to the focal length f. By making the ratio D1 / f greater than the lower limit, the central thickness D1 of the first lens L1 can be maintained so that deformation or cracking of the first lens L1 does not occur as the lens system 10 is miniaturized. On the other hand, by making the ratio D1 / f less than the upper limit, the increase in the central thickness D1 of the first lens L1 can be suppressed, the height of off-axis rays passing through the first lens L1 can be suppressed, and the effective diameter of the object-side surface S3 of the first lens L1, i.e., the front element diameter, can be kept small. Therefore, by satisfying conditional equation (5), the quality of the first lens L1 can be ensured while miniaturizing the imaging lens 110. The lower limit of conditional equation (5) is 0.15. The upper limit of conditional equation (5) is 0.5.

[0037] Conditional equation (6) defines the relationship between the distance TTL1 of the lens system 10 on the optical axis from the object-side surface S3 of the first lens L1 to the image plane IA and the maximum image height ImgH, using the ratio of the distance TTL1 to the maximum image height ImgH. By satisfying conditional equation (6), aberrations such as chromatic aberration can be suitably corrected while miniaturizing the imaging lens 110. The lower limit of conditional equation (6) is 2.5, and the upper limit of conditional equation (6) is 4.0.

[0038] In this embodiment, the lens system 10 preferably satisfies the following condition (7) when the entrance pupil diameter of the lens system 10 is EPD. f / EPD>3.8 ···(7)

[0039] Condition (7) defines the relationship between the focal length f and the entrance pupil diameter EPD at the d line of the lens system 10, and is the condition that defines the so-called F number. By satisfying condition (8), the diameter of the off-axis rays passing through the first lens L1 can be kept small, and therefore the effective diameter of the object-side surface S3 of the first lens L1, i.e., the front element diameter, can be kept small. The lower limit of condition (6) is 3.8.

[0040] The lens system 10 according to this embodiment preferably satisfies the following condition (8) when the focal length of the second lens is f2. 0.6 <f2 / f<1.5 ···(8)

[0041] Conditional equation (8) defines the relationship between the focal length f2 of the second lens L2 on the d line and the focal length f of the lens system 10 on the d line, using the focal length ratio f2 / f. By making the focal length ratio f2 / f larger than the lower limit of conditional equation (8), the refractive power of the second lens L2 does not become excessively strong, aberrations occurring in the second lens L2 are suppressed, and performance degradation due to eccentricity errors is reduced, thus enabling both aberration suppression and wide-angle correction.

[0042] On the other hand, by making the ratio of focal lengths f2 / f smaller than the upper limit of conditional equation (8), the refractive powers of the second lens L2 and the third lens L3 can be adjusted to a suitable range while maintaining the miniaturization of the lens system 10. Therefore, the angle of light rays incident on the image plane IA in the lens system 10 can be kept small, and space can be secured on the image plane IA side of the third lens L3 for inserting the light-transmitting member 30 and the cover glass. For example, as mentioned above, the light-transmitting member 30 can be formed as a filter glass that blocks infrared rays and transmits visible light, so that an imaging lens 110 capable of blocking infrared rays can be constructed.

[0043] The lower limit of condition (8) is 0.6. The upper limit of condition (8) is 1.5.

[0044] In this embodiment, the lens system 10 preferably satisfies the following condition (9) when the effective diameter of the first lens L1 is ED1. 1.0 <ED1 / ImgH<2.4 ···(9)

[0045] Conditional equation (9) defines the relationship between the effective diameter ED1 of the object-side surface S3 of the first lens L1 and the maximum image height ImgH using the ratio ED1 / ImgH of the effective diameter ED1 to the maximum image height ImgH. By making the ratio ED1 / ImgH greater than the lower limit, the effective diameter ED1 of the object-side surface S3 of the first lens L1, i.e., the front element diameter, can be maintained at a constant value, enabling suitable correction of aberrations such as chromatic aberration, and thus allowing for the acquisition of suitable resolution performance. On the other hand, by making the ratio ED1 / ImgH smaller than the upper limit, the effective diameter ED1 of the object-side surface S3 of the first lens L1, i.e., the front element diameter, can be kept small, thus maintaining the miniaturization of the first lens L1.

[0046] The lower limit of conditional equation (9) is 1, preferably 1.3. The upper limit of conditional equation (9) is 2.4, preferably 2.1. Therefore, the ratio of focal lengths f1 / f may be, for example, in the range greater than 1.3 and less than 2.1 or 2.4, or in the range greater than 1 and less than 2.1.

[0047] In the lens system 10 according to this embodiment, the first lens L1 is preferably made of plastic. By making the first lens L1 out of plastic, a low-cost and high-precision aspherical lens can be created, and the weight can be reduced. Furthermore, in the lens system 10 according to this embodiment, the object-side surface S3 of the first lens L1 is preferably flat.

[0048] Furthermore, the lens system 10 according to this embodiment further includes a wind glass 20 arranged on the object side of the first lens L1, and it is preferable that the following conditional expression (10) is satisfied when the central thickness of the wind glass 20 is D0. 0.05 ≤ D0 / ImgH ≤ 0.3 ···(10)

[0049] Conditional equation (10) defines the relationship between the central thickness D0 of the windshield 20 and the maximum image height ImgH using the ratio D0 / ImgH of the central thickness D0 to the maximum image height ImgH. By making the ratio D0 / ImgH greater than the lower limit, the central thickness D0 of the windshield 20 can be maintained so that deformation or cracking of the windshield 20 does not occur as the lens system 10 is miniaturized. On the other hand, by making the ratio D0 / ImgH less than the upper limit, the height of off-axis rays passing through the windshield 20 can be suppressed, thereby maintaining the miniaturization of the first lens L1. Therefore, by satisfying conditional equation (10), the quality of the windshield 20 can be ensured while miniaturizing the imaging lens 110. The lower limit of conditional equation (10) is 0.05. The upper limit of conditional equation (10) is 0.3.

[0050] In the lens system 10 according to this embodiment, the aperture STO is preferably formed as a light-shielding film or light-shielding sheet on the image plane IA side of the second lens L2. The light-shielding film is formed by, for example, applying black photoresist. By forming the light-shielding film by applying black photoresist, a black light-shielding film with low reflectivity, low gloss, lightweight, or high sliding properties can be formed, thereby improving the quality of the imaging lens 110. The light-shielding sheet is formed using a resin film or metal as a substrate. The surface of the light-shielding sheet is coated with black paint. By coating the surface of the light-shielding sheet with black paint, a light-shielding sheet with high light-shielding properties can be formed, thereby improving the quality of the imaging lens 110. Furthermore, by providing a light-shielding film or light-shielding sheet on the image plane IA side of the second lens L2, a highly light-shielding aperture STO can be formed.

[0051] In the lens system 10 according to this embodiment, the aperture STO is formed as a light-shielding film on the image plane IA side of the second lens L2, and it is preferable that the second lens L2 satisfies the following conditional equation (11) when the sag amount on the image plane IA side of the second lens L2 is SR. |SR|<0.1 ···(11)

[0052] Condition (11) specifies the absolute value of the sag amount SR at the effective diameter end of the image plane IA side surface S6 of the second lens L2 when the aperture STO is formed as a light-shielding film on the image plane IA side surface of the second lens L2. By satisfying condition (11), the photomask with the pattern for forming the light-shielding film and the second lens L2 can be brought into close proximity, thereby stabilizing the shape of the light-shielding film formed on the image plane IA side surface of the second lens L2. The upper limit of the absolute value of the sag amount SR is 0.1.

[0053] As described above, according to this embodiment, parameters such as focal length, Abbe number, overall length, and maximum image height in the lens system 10 are appropriately set, and a balance is maintained between wide-angle and miniaturization of the imaging lens and aberration correction in the visible light wavelength range. Therefore, it is possible to achieve wide-angle and miniaturization while suitably correcting aberrations such as chromatic aberration.

[0054] The following describes embodiments of the imaging lens 110 according to this disclosure. The parameters used in each embodiment are as follows. In the lens data and lens system specifications tables, the unit of angle is "degrees" and the unit of length is "mm". The object distance (OBJ) in each embodiment is 12 mm. The object distance is defined as the distance along the optical axis from the object-side surface S1 of the windshield 20 to the object. f: Focal length on the d line of lens systems 11, 12, 13, 14, 15, and 16 Fno: F number (=f / EPD) ω: Half angle of view ImgH: Maximum image height TTL: Total optical length of lens systems 11, 12, 13, 14, 15, and 16 (distance along the optical axis from the object-side surface S1 of the front glass 20 to the image plane IA) TTL1: Distance along the optical axis of lens system 10 from the object-side surface S3 of the first lens L1 to the image plane IA. i: Face number in lens systems 11, 12, 13, 14, 15, 16 (i=1, ..., 11, 12) Ri: radius of curvature on the i-th face Si Di: Center distance between the i-th face Si and the (i+1)-th face S(i+1) nd: Refractive index of lens material relative to the d line νd: Abbe number of lens material

[0055] Note that "INF" in the radius of curvature indicates that the surface is planar.

[0056] In each of the following embodiments, all lens surfaces Si have an aspherical shape. Here, the aspherical shape can be expressed by the amount of sag X in the direction of the optical axis from the tangent plane of the surface vertex, and the amount of sag X is obtained by the following equation, where H is the height from the optical axis, R is the radius of curvature, K is the cone constant, and Am is the m-th aspherical coefficient. X=(H 2 / R) / [1+{1-(1+K)H 2 / R 2} 1 / 2 ]+ΣAm·H m

[0057] Therefore, below, the aspherical shape is identified by showing the value of the aspherical coefficient Am in the above aspherical formula. In the table of aspherical data shown below, the numerical value of the aspherical coefficient "E±n" (where n is a natural number) is in base 10 exponential form. That is, "E±n" is "×10 ±n It means "...".

[0058] Furthermore, the imaging lens 110 in each embodiment includes, in order from the object side toward the image plane IA side, a first lens L1, a second lens L2, an aperture STO, and a third lens L3. [Examples]

[0059] Figure 2 shows the configuration of the imaging lens 110 according to Embodiment 1. In Figure 2, the front glass 20, the lens system 11 corresponding to the lens system 10 shown in Figure 1, the light-transmitting member 30, the cover glass 40, and the image plane IA of the image sensor 50 are shown.

[0060] Surface number 1 corresponds to the object-side surface of the windshield 20, and surface number 2 corresponds to the image plane IA-side surface of the windshield 20. Surface number 7 corresponds to the aperture STO surface. Surface number 10 corresponds to the object-side surface of the light-transmitting member 30. Surface number 11 corresponds to the image plane IA-side surface of the light-transmitting member 30 and the object-side surface of the cover glass 40.

[0061] Furthermore, Figure 3 is an aberration diagram of the imaging lens 110 shown in Figure 2. In the spherical aberration diagram of Figure 3, the dashed line shows the aberration at line F, the solid line shows the aberration at line d, and the short dashed line shows the aberration at line C.

[0062] In Example 1, the first lens L1 is a lens with negative refractive power, with a flat surface facing the object plane and a concave surface facing the image plane IA. The second lens L2 is a lens with positive refractive power, with a convex surface facing the object plane and a convex surface facing the image plane IA. The third lens L3 is a lens with positive refractive power, with a concave surface facing the object plane and a convex surface facing the image plane IA.

[0063] Table 1 shows the lens data of the imaging lens 110 according to Example 1.

[0064] [Table 1]

[0065] Furthermore, Tables 2 and 3 below show the aspherical data of the imaging lens 110 according to Example 1. Specifically, Tables 2 and 3 show the cone constant K and aspherical coefficient Am in the lens system 11.

[0066] [Table 2]

[0067] [Table 3]

[0068] Furthermore, Table 4 below shows the specifications of the lens system related to Example 1. Specifically, Table 4 shows the focal length f, F number Fno, half-angle of view ω, maximum image height ImgH, optical length TTL, and distance TTL1 of the lens system 11.

[0069] [Table 4] [Examples]

[0070] Figure 4 shows the configuration of the imaging lens 110 according to Embodiment 2. In Figure 4, the front glass 20, the lens system 12 corresponding to the lens system 10 shown in Figure 1, the light-transmitting member 30, the cover glass 40, and the image plane IA of the image sensor 50 are shown. The surface numbers of the front glass 20, aperture STO, light-transmitting member 30, and cover glass 40 are defined in the same way as in Embodiment 1.

[0071] Furthermore, Figure 5 is an aberration diagram of the imaging lens 110 shown in Figure 4. In the spherical aberration diagram of Figure 5, the dashed line shows the aberration at line F, the solid line shows the aberration at line d, and the short dashed line shows the aberration at line C.

[0072] In Example 2, the first lens L1 is a lens with negative refractive power, with a flat surface facing the object plane and a concave surface facing the image plane IA. The second lens L2 is a lens with positive refractive power, with a convex surface facing the object plane and a convex surface facing the image plane IA. The third lens L3 is a lens with positive refractive power, with a convex surface facing the object plane and a convex surface facing the image plane IA.

[0073] Table 5 shows the lens data of the imaging lens 110 according to Example 2.

[0074] [Table 5]

[0075] Furthermore, Tables 6 and 7 below show the aspherical data of the imaging lens 110 according to Example 2. Specifically, Tables 6 and 7 show the cone constant K and aspherical coefficient Am in the lens system 12.

[0076] [Table 6]

[0077] [Table 7]

[0078] Furthermore, Table 8 below shows the specifications of the lens system relating to Example 2. Specifically, Table 8 shows the focal length f, F number Fno, half-angle of view ω, maximum image height ImgH, optical length TTL, and distance TTL1 of the lens system 12.

[0079] [Table 8] [Examples]

[0080] Figure 6 shows the configuration of the imaging lens 110 according to Example 3. In Figure 6, the front glass 20, the lens system 13 corresponding to the lens system 10 shown in Figure 1, the light-transmitting member 30, the cover glass 40, and the image plane IA of the image sensor 50 are shown. As shown in Figure 6, in Example 3, an adhesive portion 60 is provided between the image plane IA side surface of the front glass 20 and the first lens L1, with the gap filled with the same resin as the material of the first lens L1. The surface numbers of the front glass 20, aperture STO, light-transmitting member 30, and cover glass 40 are defined in the same way as in Example 1 and Example 2.

[0081] Furthermore, Figure 7 is an aberration diagram of the imaging lens 110 shown in Figure 6. In the spherical aberration diagram of Figure 9, the dashed line shows the aberration at line F, the solid line shows the aberration at line d, and the short dashed line shows the aberration at line C.

[0082] In Example 3, the first lens L1 is a lens with negative refractive power, with a flat surface facing the object plane and a concave surface facing the image plane IA. The second lens L2 is a lens with positive refractive power, with a convex surface facing the object plane and a flat surface facing the image plane IA. The third lens L3 is a lens with positive refractive power, with a convex surface facing the object plane and a convex surface facing the image plane IA.

[0083] Table 9 shows the lens data for the imaging lens 110 according to Example 3.

[0084] [Table 9]

[0085] Furthermore, Tables 10 and 11 below show the aspherical data of the imaging lens 110 according to Example 3. Specifically, Tables 10 and 11 show the cone constant K and aspherical coefficient Am in the lens system 13.

[0086] [Table 10]

[0087] [Table 11]

[0088] Furthermore, Table 12 below shows the specifications of the lens system relating to Example 3. Specifically, Table 12 shows the focal length f, F number Fno, half-angle of view ω, maximum image height ImgH, optical length TTL, and distance TTL1 of the lens system 13.

[0089] [Table 12] [Examples]

[0090] Figure 8 shows the configuration of the imaging lens 110 according to Example 4. In Figure 8, the front glass 20, the lens system 14 corresponding to the lens system 10 shown in Figure 1, the light-transmitting member 30, the cover glass 40, and the image plane IA of the image sensor 50 are shown. The surface numbers of the front glass 20, aperture STO, light-transmitting member 30, and cover glass 40 are defined in the same way as in Examples 1 to 3.

[0091] Figure 9 is an aberration diagram of the imaging lens 110 shown in Figure 8. In the spherical aberration diagram of Figure 9, the dashed line shows the aberration at line F, the solid line shows the aberration at line d, and the short dashed line shows the aberration at line C.

[0092] In Example 4, the first lens L1 is a lens with negative refractive power, with a flat surface facing the object plane and a concave surface facing the image plane IA. The second lens L2 is a lens with positive refractive power, with a convex surface facing the object plane and a concave surface facing the image plane IA. The third lens L3 is a lens with positive refractive power, with a convex surface facing the object plane and a convex surface facing the image plane IA.

[0093] Table 13 shows the lens data for the imaging lens 110 according to Example 4.

[0094] [Table 13]

[0095] Furthermore, Tables 14 and 15 below show the aspherical data of the imaging lens 110 according to Example 4. Specifically, Tables 14 and 15 show the cone constant K and aspherical coefficient Am in the lens system 14.

[0096] [Table 14]

[0097] [Table 15]

[0098] Furthermore, Table 16 below shows the specifications of the lens system related to Example 4. Specifically, Table 16 shows the focal length f, F number Fno, half-angle of view ω, maximum image height ImgH, optical length TTL, and distance TTL1 of lens system 14.

[0099] [Table 16] [Examples]

[0100] Figure 10 shows the configuration of the imaging lens 110 according to Example 5. In Figure 10, the front glass 20, the lens system 15 corresponding to the lens system 10 shown in Figure 1, the light-transmitting member 30, the cover glass 40, and the image plane IA of the image sensor 50 are shown. The surface numbers of the front glass 20, aperture STO, light-transmitting member 30, and cover glass 40 are defined in the same way as in Examples 1 to 4.

[0101] Figure 11 is an aberration diagram of the imaging lens 110 shown in Figure 10. In the spherical aberration diagram of Figure 10, the dashed line shows the aberration at line F, the solid line shows the aberration at line d, and the short dashed line shows the aberration at line C.

[0102] In Example 5, the first lens L1 is a lens with negative refractive power, with a flat surface facing the object plane and a concave surface facing the image plane IA. The second lens L2 is a lens with positive refractive power, with a convex surface facing the object plane and a concave surface facing the image plane IA. The third lens L3 is a lens with positive refractive power, with a convex surface facing the object plane and a convex surface facing the image plane IA.

[0103] Table 17 shows the lens data of the imaging lens 110 according to Example 5.

[0104] [Table 17]

[0105] Furthermore, Tables 18 and 19 below show the aspherical data of the imaging lens 110 according to Example 5. Specifically, Tables 18 and 19 show the cone constant K and aspherical coefficient Am in the lens system 15.

[0106] [Table 18]

[0107] [Table 19]

[0108] Furthermore, Table 20 below shows the specifications of the lens system related to Example 5. Specifically, Table 20 shows the focal length f, F number Fno, half-angle of view ω, maximum image height ImgH, optical length TTL, and distance TTL1 of lens system 15.

[0109] [Table 20] [Examples]

[0110] Figure 12 shows the configuration of the imaging lens 110 according to Embodiment 6. In Figure 12, the front glass 20, the lens system 14 corresponding to the lens system 10 shown in Figure 1, the light-transmitting member 30, the cover glass 40, and the image plane IA of the image sensor 50 are shown. As shown in Figure 12, in Embodiment 6, the object-side surface of the first lens L1 is joined to the image plane IA-side surface of the front glass 20.

[0111] In Example 6, surface number 1 corresponds to the object-side surface of the windshield 20, as in the other embodiments described above. However, the assignment of surface numbers 2 and beyond in Example 6 differs from the other embodiments. Surface number 2 corresponds to the image plane IA-side surface of the windshield 20. Since the object-side surface of the first lens L1 is joined to this surface, the object-side surface of the first lens L1 is also assigned surface number 2. Surface number 6 corresponds to the aperture STO surface. Surface number 9 corresponds to the object-side surface of the light-transmitting member 30. Surface number 10 corresponds to the image plane IA-side surface of the light-transmitting member 30 and the object-side surface of the cover glass 40. Surface number 11 corresponds to the image plane IA-side surface of the cover glass 40.

[0112] Figure 13 is an aberration diagram of the imaging lens 110 shown in Figure 12. In the spherical aberration diagram of Figure 12, the dashed line shows the aberration at line F, the solid line shows the aberration at line d, and the short dashed line shows the aberration at line C.

[0113] In Example 6, the first lens L1 is a lens with negative refractive power, with a flat surface facing the object plane and a concave surface facing the image plane IA. The second lens L2 is a lens with positive refractive power, with a convex surface facing the object plane and a concave surface facing the image plane IA. The third lens L3 is a lens with positive refractive power, with a convex surface facing the object plane and a convex surface facing the image plane IA.

[0114] Table 21 shows the lens data of the imaging lens 110 according to Example 6.

[0115] [Table 21]

[0116] Furthermore, Tables 22 and 23 below show the aspherical data of the imaging lens 110 according to Example 6. Specifically, Tables 22 and 23 show the cone constant K and aspherical coefficient Am in the lens system 16.

[0117] [Table 22]

[0118] [Table 23]

[0119] Furthermore, Table 24 below shows the specifications of the lens system relating to Example 6. Specifically, Table 24 shows the focal length f, F-number Fno, half-angle of view ω, maximum image height ImgH, optical length TTL, and distance TTL1 of lens system 16.

[0120] [Table 24]

[0121] Tables 25 and 26 show the corresponding values ​​for conditional equations (1) to (11) in lens systems 11 to 16 of Examples 1 to 6 described above. Tables 27 and 28 show the individual parameters related to conditional equations (1) to (11). As shown in Tables 25 and 26, all of the examples satisfy all of conditional equations (1) to (11).

[0122] [Table 25]

[0123] [Table 26]

[0124] [Table 27]

[0125] [Table 28]

[0126] Furthermore, as shown in the aberration diagrams for each embodiment (Figures 3, 5, 7, 9, 11, and 13), lens systems 11 to 16 have been realized that can suitably correct aberrations despite having a wide angle of view near half a 60-degree angle of view.

[0127] While embodiments of this disclosure have been described above, the configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications are possible as appropriate, without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments, but is limited only by the claims.

[0128] Furthermore, each aspect disclosed herein can be combined with any other features disclosed herein.

[0129] The disclosure described above includes the following clauses [1] through [8].

[0130] The lens system comprises, in order from the object side toward the image plane side, a first lens having negative refractive power with a concave surface facing the image plane side, a second lens having positive refractive power with a convex surface facing the object side, an aperture, and a third lens having positive refractive power with a convex surface facing the image plane side. The aforementioned lens system is When f is the focal length of the lens system on the d line, f1 is the focal length of the first lens, νd1 is the Abbe number of the first lens, νd2 is the Abbe number of the second lens, νd3 is the Abbe number of the third lens, D1 is the center thickness of the first lens, TTL1 is the distance of the lens system from the object-side surface of the first lens to the image plane, and ImgH is the maximum image height, an imaging lens that satisfies the following conditions (1) to (6). -1.0 <f1 / f<-0.45 ···(1) νd1>40 ···(2) νd1 / νd2>1.5 ···(3) νd3>40 ···(4) 0.15 <D1 / f<0.5 ···(5) 2.5 <TTL1 / ImgH<4 ···(6)

[0131] [Clause 2] The aforementioned lens system is The imaging lens described in Clause 1, which satisfies the following condition (7), when the entrance pupil diameter of the lens system is EPD. f / EPD>3.8 ···(7)

[0132] [Clause 3] The aforementioned lens system is When the focal length of the second lens is f2, the imaging lens described in clause 1 or 2 satisfies the following condition (8). 0.6 <f2 / f<1.5 ···(8)

[0133] [Clause 4] The aforementioned lens system is When the effective diameter of the first lens is ED1, the imaging lens described in any one of clauses 1 to 3 satisfies the following condition (9). 1 <ED1 / ImgH<2.4 ···(9)

[0134] [Clause 5] The first lens is, An imaging lens according to any one of the clauses 1 to 4, wherein the surface facing the object is flat. 0.05 ≤ D0 / ImgH ≤ 0.3 ···(10)

[0135] [Clause 6] The aforementioned lens system is The first lens further comprises a wind glass positioned on the object side, When the central thickness of the windshield is D0, the imaging lens described in any one of clauses 1 to 5 satisfies the following condition (10). 0.05 ≤ D0 / ImgH ≤ 0.3 ···(10)

[0136] [Clause 7] The aperture is formed as a light-shielding film or light-shielding sheet on the image plane side surface of the second lens, according to any one of the claims 1 to 6.

[0137] [Clause 8] The aperture is formed as the light-shielding film, The second lens is, When the sag amount on the image plane side of the second lens is denoted as SR, the imaging lens described in clause 7 satisfies the following condition (11). |SR|<0.1 ···(11)

[0138] [Clause 9] An imaging device equipped with an imaging lens as described in any one of clauses 1 to 8. [Explanation of Symbols]

[0139] 10, 11, 12, 13, 14, 15, 16 Lens system, 20 Front glass, 30 Light-transmitting material, 40 Cover glass, 50 Image sensor, 60 Adhesive part, 100 Imaging device, 110 Imaging lens, 120 Image acquisition unit, 130 Processor, 140 Memory, 150 Input / Output unit, L1 First lens, L2 Second lens, L3 Third lens, STO Aperture.

Claims

1. The lens system comprises, in order from the object side toward the image plane side, a first lens having negative refractive power with a concave surface facing the image plane side, a second lens having positive refractive power with a convex surface facing the object side, an aperture, and a third lens having positive refractive power with a convex surface facing the image plane side. The aforementioned lens system is When the focal length of the lens system on the d line is f, the focal length of the first lens is f1, the Abbe number of the first lens is νd1, the Abbe number of the second lens is νd2, the Abbe number of the third lens is νd3, the center thickness of the first lens is D1, the distance of the lens system from the object-side surface of the first lens to the image plane is TTL1, and the maximum image height is ImgH, an imaging lens that satisfies the following conditions (1) to (6). -1.0<f1 / f<-0.45...(1) νd1>40...(2) νd1 / νd2>1.5...(3) νd3>40...(4) 0.15<D1 / f<0.5 (5) 2.5<TTL1 / ImgH<4...(6)

2. The aforementioned lens system is The imaging lens according to claim 1, wherein the entrance pupil diameter of the lens system is EPD, and the following condition (7) is satisfied. f / EPD>3.8...(7)

3. The aforementioned lens system is The imaging lens according to claim 1, wherein the following condition (8) is satisfied when the focal length of the second lens is f2. 0.6<f2 / f<1.5...(8)

4. The aforementioned lens system is The imaging lens according to claim 1, wherein the effective diameter of the first lens is ED1, and the following conditional equation (9) is satisfied. 1<ED1 / ImgH<2.4 (9)

5. The first lens is, It is made of plastic, and the surface facing the object is flat. The aforementioned lens system is The first lens further comprises a wind glass positioned on the object side, The imaging lens according to claim 1, wherein the central thickness of the windshield is D0, and the following conditional equation (10) is satisfied. 0.05 ≤ D0 / ImgH ≤ 0.3 ... (10)

6. The imaging lens according to claim 1, wherein the aperture is formed as a light-shielding film or light-shielding sheet on the image plane side surface of the second lens.

7. The aperture is formed as the light-shielding film, The second lens is, The imaging lens according to claim 6, wherein the amount of sag on the image plane side of the second lens is SR, and the following conditional equation (11) is satisfied. |SR|<0.1...(11)

8. An imaging device comprising an imaging lens according to any one of claims 1 to 7.

Images