JP2018185378A - Macro lens and imaging device including macro lens - Google Patents

Abstract

An object of the present invention is to provide a macro lens capable of securing a magnification equal to or greater than 1x suitable for photographing at a finite distance while shortening the overall length of the lens and an imaging device capable of capturing a large subject even in close-up photography. A macro lens L has, in order from the object side, a biconvex first lens L1, a second lens L2 having a negative refractive power and a concave surface facing the object side, and a positive refractive power. And a meniscus third lens L3 having a convex surface facing the object side and a fourth meniscus lens L4 having negative refractive power and a concave surface facing the object side. It further includes an aperture stop St that includes a plurality of lenses and is located closer to the object side than the object side surface of the third lens L3. [Selection] Figure 1

Description

  The present disclosure relates to a macro lens and an imaging apparatus including the macro lens.

  In recent years, with the spread of small cameras and the like, small cameras have been used for reading two-dimensional barcodes, recording handwritten memos, and the like, and an imaging lens mounted on the small cameras is required to be compact.

  For example, Patent Document 1 below proposes an imaging lens that can be mounted on a smartphone, a tablet-type terminal, and the like and that includes four lenses.

US Patent US2016 / 0352984A1

  However, in the above prior art, since the imaging lens is not designed as a macro lens, it is difficult to capture a large subject even in close-up shooting, and it is difficult to obtain satisfactory performance when shooting at a magnification of 1 × or more. It was. For this reason, although it coped by enlarging the data image | photographed with the small camera, the subject that an image deteriorated occurred. In addition, an imaging device equipped with a macro lens is required to be able to shorten the entire lens length while satisfying the above-described photographing performance.

  In consideration of the above facts, the present disclosure can take a large image of a subject even with a macro lens and close-up photography that can secure a magnification equal to or greater than 1x suitable for photographing at a finite distance while shortening the overall length of the lens. The object is to obtain an imaging device.

  Specific means for solving the above problems include the following aspects. That is, the macro lens according to this aspect has, in order from the object side, a first lens having a biconvex shape, a second lens having a negative refractive power and a concave surface facing the object side, and a positive refractive power. And substantially four lenses comprising a meniscus third lens having a convex surface facing the object side and a meniscus fourth lens having negative refractive power and a concave surface facing the object side. And further comprising an aperture stop located closer to the object side than the object side surface of the third lens.

  In the macro lens of this aspect, “consisting essentially of four lenses” means that the macro lens of this aspect has no power other than the four lenses, an aperture, a cover glass, etc. It is meant to include an optical element other than a lens, a lens flange, a lens barrel, an image sensor, a mechanism portion such as a camera shake correction mechanism, and the like. In addition, for the lenses including the aspherical surface among the above lenses, the sign of the surface shape and refractive power in the paraxial region is used as the sign of the face shape and refractive power.

Further, the macro lens according to this aspect is any one of the following conditional expressions (1) to (4), (1-1) to (4-1), and (1-2) to (3-2). May be satisfied, or any combination may be satisfied.
1.5 <f3 / f <4 (1)
1.8 <f3 / f <3.9 (1-1)
2.8 <f3 / f <3.9 (1-2)
−55 <f4 / f <−2.5 (2)
−55 <f4 / f <−2.6 (2-1)
−54 <f4 / f <−8 (2-2)
1.5 <f34 / f <5.5 (3)
1.6 <f34 / f <5.4 (3-1)
3 <f34 / f <5.2 (3-2)
−0.65 <[(1-N1) / R2 + (N2-1) / R3-{((1-N1) · (N2-1)) / (R2 · R3)} · D2] · f <−0 .45 (4)
−0.62 <[(1-N1) / R2 + (N2-1) / R3-{((1-N1) · (N2-1)) / (R2 · R3)} · D2] · f <−0 .48 (4-1)
However,
f: focal length of the entire system f3: focal length of the third lens f4: focal length of the fourth lens f34: combined focal length of the third lens and the fourth lens D2: image side of the first lens The distance on the optical axis between the surface of the second lens and the object side surface of the second lens N1: Refractive index of the first lens N2: Refractive index of the second lens R2: Image side surface of the first lens Radius of curvature R3: radius of curvature of the object side surface of the second lens

  Furthermore, in the macro lens according to this aspect, the second lens has a biconcave shape.

  In addition, the imaging apparatus according to this aspect includes the macro lens according to this aspect.

  As described above, the macro lens according to an embodiment of the present invention has an excellent effect that it is possible to ensure a magnification equal to or greater than 1 × suitable for photographing at a finite distance while shortening the entire lens length.

  In addition, the imaging apparatus according to an embodiment of the present invention has an excellent effect that a subject can be photographed greatly even in close-up photography.

It is sectional drawing which shows the lens structure and light ray locus | trajectory of the macro lens which concern on 1st Embodiment. It is sectional drawing which shows the lens structure of the macro lens which concerns on 2nd Embodiment. It is sectional drawing which shows the lens structure of the macro lens which concerns on 3rd Embodiment. It is sectional drawing which shows the lens structure of the macro lens which concerns on 4th Embodiment. It is sectional drawing which shows the lens structure of the macro lens which concerns on 5th Embodiment. It is an aberration diagram showing the spherical aberration of the macro lens according to the first embodiment. FIG. 5 is an aberration diagram showing astigmatism of the macro lens according to the first embodiment. It is an aberration diagram which shows the distortion aberration of the macro lens which concerns on 1st Embodiment. FIG. 5 is an aberration diagram showing lateral chromatic aberration of the macro lens according to the first embodiment. It is an aberration diagram showing the spherical aberration of the macro lens according to the second embodiment. It is an aberration diagram showing astigmatism of the macro lens according to the second embodiment. It is an aberration diagram showing distortion of the macro lens according to the second embodiment. It is an aberration diagram showing the lateral chromatic aberration of the macro lens according to the second embodiment. It is an aberration diagram showing the spherical aberration of the macro lens according to the third embodiment. It is an aberration diagram showing astigmatism of the macro lens according to the third embodiment. It is an aberration diagram showing distortion of the macro lens according to the third embodiment. It is an aberration diagram showing the lateral chromatic aberration of the macro lens according to the third embodiment. It is an aberration diagram showing the spherical aberration of the macro lens according to the fourth embodiment. It is an aberration diagram showing astigmatism of the macro lens according to the fourth embodiment. It is an aberration diagram which shows the distortion aberration of the macro lens which concerns on 4th Embodiment. It is an aberration diagram showing the lateral chromatic aberration of the macro lens according to the fourth embodiment. It is an aberration diagram showing the spherical aberration of the macro lens according to the fifth embodiment. It is an aberration diagram showing astigmatism of the macro lens according to the fifth embodiment. It is an aberration diagram showing the distortion aberration of the macro lens according to the fifth embodiment. It is an aberration diagram showing the lateral chromatic aberration of the macro lens according to the fifth embodiment. It is a perspective view which shows the structure of the smart phone as an imaging device provided with the macro lens which concerns on 1st Embodiment-5th Embodiment.

  Hereinafter, a first embodiment of a macro lens according to the present disclosure will be described. FIG. 1 shows a cross section of a “macro lens L” according to this embodiment, and this cross section corresponds to the lens configuration of numerical examples (Tables 1 and 2) according to the first embodiment to be described later. doing. FIG. 1 also shows the ray trajectory (optical path) of the on-axis light beam 10, the light beam 12 with the maximum field angle, and the half value ω of the maximum field angle in a state in which an object located at a finite distance is in focus. In the luminous flux 12 having the maximum field angle, the principal ray 14 having the maximum field angle is indicated by a one-dot chain line. Similarly, FIGS. 2 to 5 show cross-sectional configurations of macro lenses L according to second to fifth embodiments, which will be described later, respectively, and these are the second to fifth embodiments, respectively. Corresponds to the numerical examples (Tables 3 to 10).

  In FIG. 1 to FIG. 5, the symbol Ri is the i-th surface to which the surface of the lens element closest to the object side is the first, and is added so as to increase sequentially toward the image side (imaging side). Shows the radius of curvature. On the other hand, the symbol Di indicates the distance (surface interval) between the i-th surface and the (i + 1) -th surface on the optical axis Z1. Since the basic configuration is the same in each embodiment, the following description is based on the configuration example of the macro lens shown in FIG.

  The macro lens L is a variety of imaging devices using an imaging element such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), particularly a relatively small portable terminal device such as a digital still camera, a surveillance camera, and a camera. It can be used for a mobile phone, a smart phone, a tablet terminal, a PDA (Personal Digital Assistant), and the like. The macro lens L includes a “first lens L 1”, a “second lens L 2”, a “third lens L 3”, and a “fourth lens L 4” in order from the object side along the optical axis Z 1. I have.

  On the other hand, FIG. 11 shows a “smart phone 16” as an imaging device. The smartphone 16 includes a macro lens L according to the present embodiment, and a camera unit including an imaging element 18 (see FIGS. 1 to 5) such as a CCD that outputs an imaging signal corresponding to an optical image formed by the macro lens L. 20. The image sensor 18 is disposed on the imaging surface (imaging surface) of the macro lens L. The macro lens L can also be used for the camera unit 22 on the back side of the smartphone 16. Moreover, according to the performance calculated | required by the macro lens L, the macro lens L which concerns on 2nd Embodiment-5th Embodiment mentioned later may be mounted in the smart phone 16. FIG.

  Returning to FIG. 1, various optical members 24 may be disposed between the fourth lens L <b> 4 and the image sensor 18 depending on the configuration on the camera side where the lens is mounted. For example, a flat optical member such as a cover glass for protecting the imaging surface and an infrared cut filter may be disposed. In this case, for example, a flat cover glass having a filter effect coating such as an infrared cut filter or ND (Neutral Density) filter or a material having a similar effect may be used as the optical member 24. Good.

  Further, the fourth lens L4 may be coated without using the optical member 24, and the same effect as the optical member 24 may be provided. Thereby, it is possible to reduce the number of parts and the overall length of the lens.

  The macro lens L includes an “aperture stop St” disposed on the object side of the object side surface of the third lens L3. When the aperture stop St is arranged in this way, it is possible to suppress an increase in the incident angle of the light beam passing through the optical system to the imaging surface (imaging device), particularly in the periphery of the imaging region. As a result, it is possible to suppress a decrease in the amount of light around the periphery. The phrase “arranged closer to the object side than the object side surface of the third lens L3” means that the position of the aperture stop St in the optical axis direction is the same as the intersection of the axial marginal ray and the object side surface of the third lens L3. It means that it is at the position or the object side from it.

  The first lens L1 has a biconvex shape. For this reason, the object side surface of the first lens L1 and the image side surface share the positive refractive power, thereby securing the refractive power of the first lens L1 and the object side surface of the first lens L1. It is possible to prevent the absolute value of the paraxial radius of curvature of the image side surface from becoming too small, and as a result, it is easy to correct spherical aberration.

  The second lens L2 has a negative refractive power in the vicinity of the optical axis. For this reason, spherical aberration, curvature of field and axial chromatic aberration can be corrected satisfactorily. In addition, since the second lens L2 has a biconcave shape, the overall length of the lens can be suitably shortened, and spherical aberration can be favorably corrected. Moreover, since the second lens L2 has a concave surface facing the object side, the image side surface of the first lens L1 and the object side surface of the second lens L2 can be in the same direction, and as a result, It is possible to suppress the occurrence of high-order aberrations when entering the second lens L2. In addition, the 2nd lens L2 which concerns on 2nd Embodiment among 1st Embodiment-5th Embodiment has the shape which orient | assigned the convex surface to the image side in the optical axis vicinity.

  The third lens L3 has a positive refractive power in the vicinity of the optical axis. For this reason, the total lens length can be further shortened. The third lens L3 has a meniscus shape with a convex surface facing the object side in the vicinity of the optical axis. For this reason, it is advantageous for shortening the total lens length, and spherical aberration can be easily corrected. Furthermore, the rear principal point position of the third lens L3 can be easily moved toward the object side, and the overall length of the lens can be shortened more suitably.

  The fourth lens L4 has a negative refractive power in the vicinity of the optical axis. Therefore, it is possible to satisfactorily correct the curvature of field while preferably shortening the total lens length. The fourth lens L4 has a meniscus shape with a concave surface facing the object side in the vicinity of the optical axis. For this reason, the angle of incident light can be reduced, the occurrence of higher-order aberrations can be suppressed, and field curvature can be corrected well.

  Next, operations and effects relating to the conditional expression of the macro lens L configured as described above will be described in detail. In addition, it is preferable that the macro lens L satisfies any one of the conditional expressions or any combination of the following conditional expressions. Moreover, it is preferable that the satisfying conditional expression is appropriately selected according to the matters required for the macro lens L.

First, it is preferable that the focal length f3 of the third lens L3 and the focal length f of the entire system satisfy the following conditional expression (1).
1.5 <f3 / f <4 (1)

Conditional expression (1) defines a preferable numerical range of the ratio of the focal length f3 of the third lens L3 to the focal length f of the entire system. Spherical aberration can be corrected satisfactorily by avoiding being below the lower limit of conditional expression (1). On the other hand, by making sure that the upper limit of conditional expression (1) is not exceeded, the overall lens length can be suitably shortened. In order to enhance this effect, the ratio of the focal length f3 of the third lens L3 to the focal length f of the entire system preferably satisfies the following conditional expression (1-1).
1.8 <f3 / f <3.9 (1-1)

Furthermore, in order to further enhance this effect, it is more preferable that the ratio of the focal length f3 of the third lens L3 to the focal length f of the entire system satisfies the following conditional expression (1-2).
2.8 <f3 / f <3.9 (1-2)

Further, it is preferable that the focal length f4 of the fourth lens L4 and the focal length f of the entire system satisfy the following conditional expression (2).
−55 <f4 / f <−2.5 (2)

Conditional expression (2) defines a preferable numerical range of the ratio of the focal length f4 of the fourth lens L4 to the focal length f of the entire system. By preventing the lower limit of conditional expression (2) from being reached, it is possible to prevent the negative refractive power of the fourth lens L4 from becoming too weak with respect to the refractive power of the entire system. The field curvature can be favorably corrected while realizing the shortening of the image. On the other hand, spherical aberration can be satisfactorily corrected by avoiding exceeding the upper limit of conditional expression (2). In order to enhance this effect, it is preferable that the ratio of the focal length f4 of the fourth lens L4 to the focal length f of the entire system satisfies the following conditional expression (2-1).
−55 <f4 / f <−2.6 (2-1)

Furthermore, in order to further enhance this effect, it is more preferable that the ratio of the focal length f4 of the fourth lens L4 to the focal length f of the entire system satisfies the following conditional expression (2-2).
−54 <f4 / f <−8 (2-2)

Further, it is preferable that the combined focal length f34 of the third lens L3 and the fourth lens L4 and the focal length f of the entire system satisfy the following conditional expression (3).
1.5 <f34 / f <5.5 (3)

Conditional expression (3) defines a preferable numerical range of the ratio of the combined focal length f34 of the third lens L3 and the fourth lens L4 to the focal length f of the entire system. By making sure that the lower limit of conditional expression (3) is not exceeded, it is advantageous for shortening the total lens length. On the other hand, by avoiding exceeding the upper limit of conditional expression (3), it is possible to more suitably suppress an increase in the incident angle of the light beam passing through the optical system to the imaging surface (imaging device), In addition, distortion (distortion aberration) and lateral chromatic aberration can be suitably corrected. In order to enhance this effect, the ratio of the combined focal length f34 of the third lens L3 and the fourth lens L4 to the focal length f of the entire system preferably satisfies the following conditional expression (3-1).
1.6 <f34 / f <5.4 (3-1)

Furthermore, in order to further enhance this effect, the ratio of the combined focal length f34 of the third lens L3 and the fourth lens L4 to the focal length f of the entire system satisfies the following conditional expression (3-2). preferable.
3 <f34 / f <5.2 (3-2)

Further, the distance D2 on the optical axis Z1 between the image side surface of the first lens L1 and the object side surface of the second lens L2, the refractive index N1 of the first lens L1, the refractive index N2 of the second lens L2, The relationship between the curvature radius R2 of the image side surface of the first lens L1 and the curvature radius R3 of the object side surface of the second lens L2 preferably satisfies the following conditional expression (4). In addition, a portion surrounded by square brackets in the conditional expression (4) is a lens in which a space between the image side surface of the first lens L1 and the object side surface of the second lens L2 is filled with air. When the air lens is considered, the refractive power Pair23 of the air lens is shown.
−0.65 <[(1-N1) / R2 + (N2-1) / R3-{((1-N1) · (N2-1)) / (R2 · R3)} · D2] · f <−0 .45 (4)

Conditional expression (4) is preferably the product of the refractive power PAir23 of the air lens including the image side surface of the first lens L1 and the object side surface of the second lens L2 and the focal length f of the entire system. Defines the numerical range. By preventing the conditional expression (4) from being lower than the lower limit, it is possible to suppress the occurrence of distortion and lateral chromatic aberration. On the other hand, by preventing the conditional expression (4) from exceeding the upper limit, the Petzval sum can be kept small and the flatness of the image plane can be improved. In order to enhance this effect, it is preferable that the product of the refractive power PAir23 and the focal length f of the entire system satisfies the following conditional expression (4-1).
−0.62 <[(1-N1) / R2 + (N2-1) / R3-{((1-N1) · (N2-1)) / (R2 · R3)} · D2] · f <−0 .48 (4-1)

 As described above, the macro lens L according to the present embodiment can ensure a magnification of equal to or higher than that suitable for photographing at a finite distance while shortening the overall length of the lens. In addition, the smartphone 16 according to the present embodiment can mount the macro lens L so that the subject can be greatly photographed even in close-up photography.

  Next, specific numerical examples of the macro lens L according to the present embodiment will be described. Tables 1 and 2 below show specific lens data corresponding to the configuration of the macro lens L shown in FIG. Table 1 shows basic lens data of each lens constituting the macro lens L, and Table 2 shows data related to the aspherical surface of each lens. In the field of the surface number Si in the lens data shown in Table 1, in the macro lens L according to the present embodiment, the object side surface of the optical element closest to the object side is the first, and sequentially toward the image side. The number of the i-th surface, which is numbered to increase, is shown. In the column of the curvature radius Ri, the value (mm) of the curvature radius of the i-th surface from the object side is shown in correspondence with the reference symbol Ri in FIG. Similarly, in the column of the surface interval Di, the interval (mm) on the optical axis Z1 between the i-th surface Si and the i + 1-th surface Si + 1 from the object side is also shown. In the column of the refractive index Nj, the refractive index value for the d-line (wavelength 587.6 nm) of the j-th optical element from the object side is shown. The Abbe number νj column shows the Abbe number value for the d-line of the j-th optical element from the object side.

  Table 1 also includes the aperture stop St and the optical member 24. In Table 1, the surface number and the word (St) are written in the surface number column of the surface corresponding to the aperture stop St, and the surface number and (IMG) in the surface number column of the surface corresponding to the image surface. ). The sign of the radius of curvature is positive for a surface shape with a convex surface facing the object side, and negative for a surface shape with a convex surface facing the image side. Further, in the upper part outside the frame of each lens data, as the various data, the focal length f (mm) of the entire system, the back focus Bf (mm), the F number FNo. The maximum angle of view 2ω (°) is shown. The back focus Bf represents a value converted into air. Further, in the present embodiment and the second to fifth embodiments described later, the macro lens L is used for shooting a subject at a close distance such as close-up shooting, and condensing at a finite distance is assumed. The back focus Bf is illustratively a negative value.

  In the macro lens L according to the present embodiment, both surfaces of all the lenses in the first lens L1 to the fourth lens L4 are aspherical. Therefore, the numerical value of the radius of curvature of the lens surface shown in Table 1 is the numerical value of the radius of curvature near the aspherical optical axis of the lens surface (paraxial radius of curvature).

On the other hand, Table 2 shows aspherical data in the macro lens L according to the present embodiment. In the numerical values shown as aspherical data, the symbol “E” indicates that the subsequent numerical value is a “power exponent” with a base of 10, and the numerical value represented by an exponential function with the base of 10 is Indicates that the value before “E” is multiplied. For example, “1.0E-02” indicates “1.0 × 10 ⁻² ”.

  Table 2 shows the values of the coefficients Ai and KA in the aspheric surface expression represented by the following expression (A) as aspheric data. Each coefficient used in equation (A) is described below, but if Z is supplementarily described, Z is determined from a point on the aspheric surface at a height h from the optical axis Z1. The length (mm) of the perpendicular line drawn on the tangent plane (plane perpendicular to the optical axis Z1) of the apex of the spherical surface is shown, and hereinafter referred to as “aspheric surface depth”.

However,
Z: Depth of aspheric surface (mm)
h: Distance from the optical axis to the lens surface (height) (mm)
C: Paraxial curvature = 1 / R
(R: paraxial radius of curvature)
Ai: i-th order (i is an integer of 4 or more) aspheric coefficient KA: aspheric coefficient

  In the present embodiment, as the aspheric coefficient Ai, i is an even number from the 4th order to the 10th order. However, the present invention is not limited to this, and an aspherical surface whose i is an integer of 3 or less is used. The coefficient Ai may be used, or an aspheric coefficient Ai where i is an integer larger than 10 may be used.

  Similarly to the macro lens L according to the first embodiment described above, specific lens data corresponding to the configuration of the macro lens L illustrated in FIGS. 2 to 5 is represented as a second embodiment to a fifth embodiment. 3 to Table 10. In the macro lens L according to the second to fifth embodiments, as in the first embodiment described above, both surfaces of the first lens L1 to the fourth lens L4 are all aspherical. Yes. In all the embodiments except the second embodiment, the magnification of the macro lens L is equal, and the magnification of the macro lens L according to the second embodiment is twice.

  6A to 6D show aberration diagrams representing the spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration (chromatic aberration of magnification) of the macro lens L according to the first embodiment in this order. Yes.

  Each aberration diagram showing spherical aberration, astigmatism (field curvature) and distortion (distortion aberration) shows aberrations with the d-line (wavelength 587.6 nm) as the reference wavelength. Also shows aberrations for F-line (wavelength 486.1 nm) and C-line (wavelength 656.3 nm). On the other hand, in the magnification chromatic aberration diagram, aberrations for the F-line and the C-line are shown. In the astigmatism diagram, the solid line shows the sagittal direction (S) aberration, and the broken line shows the tangential direction (T) aberration. Further, FNo. Appropriately shown in each figure indicates an F number, and ω indicates a half value of the maximum angle of view in a state in which an object located at a finite distance is in focus.

  Similarly, FIGS. 7A to 10D show various aberrations of the macro lens L according to the second to fifth embodiments. The aberration diagrams shown in FIGS. 7A to 10D are all for the case where the object distance is a finite distance.

  Table 11 relates to the conditional expressions (1) to (4), (1-1) to (4-1), and (1-2) to (3-2) described above in the respective embodiments. Values are shown.

  As can be seen from the above numerical data and aberration diagrams, in the macro lens L according to each embodiment, the lens overall length is shortened and the same magnification or more suitable for photographing at a finite distance, specifically, equal magnification and 2 Double magnification can be ensured.

  The configuration of the macro lens L is not limited to the above-described embodiments, and the above-described conditional expressions (1) to (4), (1-1) to (4-1), and (1- Any material satisfying at least one of 2) to (3-2) may be used. That is, the radius of curvature, the surface interval, the refractive index, the Abbe number, the aspheric coefficient, etc. of each lens component are not limited to the values shown in each embodiment, and are within a range that satisfies at least one of the conditional expressions described above. Other values may be taken at.

  In each embodiment, the description is based on the premise that the fixed focus is used. However, it is possible to adopt a configuration in which focus adjustment is possible. For example, the entire lens system can be extended, or a part of the lenses can be moved on the optical axis to enable autofocusing.

DESCRIPTION OF SYMBOLS 10 Axial light beam 12 Light beam of maximum field angle 14 Principal light beam of maximum field angle 16 Smartphone 18 Image sensor 20 Camera unit 22 Camera unit 24 Optical member D1-D11 Surface interval L Macro lens L1 First lens L2 Second lens L3 Third Lens L4 Fourth lens R1 to R12 Radius of curvature St Aperture stop Z1 Optical axis ω Half value of maximum field angle

Claims (14)

From the object side,
A biconvex first lens;
A second lens having negative refractive power and having a concave surface facing the object side;
A meniscus third lens having positive refractive power and having a convex surface facing the object side;
Consisting of substantially four lenses having a negative refractive power and a fourth meniscus lens having a concave surface facing the object side,
A macro lens further comprising an aperture stop positioned closer to an object side than an object side surface of the third lens. The macro lens according to claim 1, further satisfying the following conditional expression:
1.5 <f3 / f <4 (1)
However,
f: focal length of the entire system f3: focal length of the third lens Furthermore, the macro lens of Claim 1 or Claim 2 which satisfies the following conditional expressions.
−55 <f4 / f <−2.5 (2)
However,
f: focal length of the entire system f4: focal length of the fourth lens The macro lens according to any one of claims 1 to 3, further satisfying the following conditional expression.
1.5 <f34 / f <5.5 (3)
However,
f: focal length of the entire system f34: combined focal length of the third lens and the fourth lens The macro lens according to any one of claims 1 to 4, further satisfying the following conditional expression.
−0.65 <[(1-N1) / R2 + (N2-1) / R3-{((1-N1) · (N2-1)) / (R2 · R3)} · D2] · f <−0 .45 (4)
However,
f: Focal length of the entire system D2: Distance on the optical axis between the image side surface of the first lens and the object side surface of the second lens N1: Refractive index of the first lens N2: Second Refractive index of the lens R2: radius of curvature of the image side surface of the first lens R3: radius of curvature of the object side surface of the second lens The second lens has a biconcave shape;
The macro lens according to any one of claims 1 to 5. The macro lens according to claim 1, further satisfying the following conditional expression.
1.8 <f3 / f <3.9 (1-1)
However,
f: focal length of the entire system f3: focal length of the third lens The macro lens according to claim 1, further satisfying the following conditional expression.
−55 <f4 / f <−2.6 (2-1)
However,
f: focal length of the entire system f4: focal length of the fourth lens Furthermore, the macro lens of any one of Claims 1-8 which satisfy | fills the following conditional expressions.
1.6 <f34 / f <5.4 (3-1)
However,
f: focal length of the entire system f34: combined focal length of the third lens and the fourth lens Furthermore, the macro lens of any one of Claims 1-9 which satisfies the following conditional expressions.
−0.62 <[(1-N1) / R2 + (N2-1) / R3-{((1-N1) · (N2-1)) / (R2 · R3)} · D2] · f <−0 .48 (4-1)
However,
f: Focal length of the entire system D2: Distance on the optical axis between the image side surface of the first lens and the object side surface of the second lens N1: Refractive index of the first lens N2: Second Refractive index of the lens R2: radius of curvature of the image side surface of the first lens R3: radius of curvature of the object side surface of the second lens The macro lens according to claim 1, further satisfying the following conditional expression.
2.8 <f3 / f <3.9 (1-2)
However,
f: focal length of the entire system f3: focal length of the third lens Furthermore, the macro lens of any one of Claims 1-11 which satisfy | fills the following conditional expressions.
−54 <f4 / f <−8 (2-2)
However,
f: focal length of the entire system f4: focal length of the fourth lens Furthermore, the macro lens of any one of Claims 1-12 which satisfy | fills the following conditional expressions.
3 <f34 / f <5.2 (3-2)
However,
f: focal length of the entire system f34: combined focal length of the third lens and the fourth lens   The imaging device provided with the macro lens of any one of Claims 1-13.