JP2016212288A - Imaging lens, imaging optical device and digital instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a downsized imaging lens that is a small F-value large-aperture medium telephoto lens, and has a front lens diameter and weight of a focus group curbed, and to provide an imaging optical device and digital instrument that include the lens.SOLUTION: An imaging lens LN includes, in order from an object side, a positive first group Gr1 and positive second group Gr2. The first group Gr1 includes, in order from the object side, positive, positive, positive, and negative first to fourth lenses L1 to L4. Of lenses consisting of the second group Gr2, a lens on the most object side is a positive lens, and at least one piece is a negative lens. Upon focusing from infinity to a close distance, a position of the first group Gr1 is stationary, and at least the second group Gr2 moves to the object side. The imaging lens satisfies a conditional expression :Nd1 max-Nd1 min>0.1, and νd1 max-νd1 min>15, (where let a refractive index and Abbe number with respect to d-line be Nd and νd, Nd1 max and Nd1 min: a maximum value and minimum of Nd of the positive lens in the first group: a maximum value and minimum of νd of the positive lens in the first group).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging lens, an imaging optical device, and a digital apparatus. More specifically, the present invention relates to an image pickup device (for example, a CCD (Charge Coupled Device) type image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) type image). A compact and large-diameter imaging lens suitable for an interchangeable lens digital camera captured by a solid-state imaging device such as a sensor, and an imaging optical device that outputs an image of a subject captured by the imaging lens and the imaging device as an electrical signal; The present invention relates to a digital device with an image input function such as a digital camera equipped with the imaging optical device.

  In recent years, digital cameras have become common as interchangeable lens cameras. In digital cameras, it is possible for a user to view a photographed image at the same magnification on a monitor. Therefore, improvement in MTF (Modulation Transfer Function) performance and reduction in chromatic aberration are increasingly required. However, in a medium telephoto lens and a telephoto lens, chromatic aberration generally increases as the focal length increases. Further, since the influence of camera shake becomes more prominent as the focal length increases, a faster shutter speed is required. As a result, a lens having a bright F value (F value = 1.0 to 2.0) is desired. In order to meet these requirements, Patent Documents 1 to 3 propose single-focus large-diameter medium telephoto lenses as interchangeable lenses for interchangeable lens digital cameras.

Japanese Patent No. 0558946 JP 2013-025157 A Japanese Patent No. 0561598

  In the medium telephoto lenses proposed in Patent Documents 1 and 2, the F value is bright and the chromatic aberration is well corrected, but there is a problem that the front lens diameter and the weight of the focus group become large. In the medium telephoto lens proposed in Patent Document 3, the F value is as bright as about 1.4 and the weight of the focus group is suppressed. However, when the focal length is further increased, the chromatic aberration cannot be corrected sufficiently. There is. Further, since the amount of movement increases in addition to the weight of the focus group, there is a problem that the movement time of the focus group is prolonged as a result.

  The present invention has been made in view of such circumstances, and its object is to achieve a large aperture medium telephoto lens with a bright F value, while reducing the front lens diameter and the weight of the focus group, and improving chromatic aberration. It is an object of the present invention to provide a corrected small imaging lens, an imaging optical device including the same, and a digital device.

In order to achieve the above object, the imaging lens of the first invention has, in order from the object side, at least a first group of positive power and a second group of positive power,
The first group includes at least a first lens having positive power, a second lens having positive power, a third lens having positive power, and a fourth lens having negative power in order from the object side. And
Among the lenses constituting the second group, the most object side lens is a positive lens, and at least one lens is a negative lens,
When focusing from infinity to short distance, the first group is fixed in position, and at least the second group moves to the object side,
The following conditional expressions (1) and (2) are satisfied.
Nd1max−Nd1min> 0.1 (1)
νd1max−νd1min> 15 (2)
However, if the refractive index for the d-line is Nd and the Abbe number for the d-line is νd,
Nd1max: the maximum value of Nd of the positive lens in the first group,
Nd1min: the minimum value of Nd of the positive lens in the first group,
νd1max: the maximum value of νd of the positive lens in the first group,
νd1min: the minimum value of νd of the positive lens in the first group,
It is.

The imaging lens of the second invention is characterized in that, in the first invention, the following conditional expression (3) is satisfied.
φ2 / φ> 1.0 (3)
However,
φ2: Power of the second group,
φ: Power of the entire system,
It is.

The imaging lens of the third invention is characterized in that, in the first or second invention, the following conditional expressions (4) and (5) are satisfied.
0.1 <φ1 / φ <1.0 (4)
0 <φ1 / φ2 <0.5 (5)
However,
φ1: Power of the first group,
φ2: Power of the second group,
φ: Power of the entire system,
It is.

An imaging lens according to a fourth aspect of the invention is characterized in that, in any one of the first to third aspects of the invention, the following conditional expression (6) is satisfied.
D1Gr / D2Gr> 1.5 (6)
However, if the diameter of the parallel light beam that enters the lens from the object side to the full aperture that determines the F value is the Fno light beam diameter,
D1Gr: Maximum Fno beam diameter in the first group,
D2Gr: maximum Fno beam diameter in the second group,
It is.

An imaging lens according to a fifth aspect of the invention is characterized in that, in any one of the first to fourth aspects of the invention, the following conditional expression (7) is satisfied.
1.4 <DG1F / IMG <1.8 (7)
However,
DG1F: effective radius of the object side surface of the first lens,
IMG: Effective radius of image circle,
It is.

  An imaging lens according to a sixth invention is characterized in that, in any one of the first to fifth inventions, an aperture stop is provided in the second group.

  The imaging lens according to a seventh aspect of the present invention is the imaging lens according to any one of the first to sixth aspects, further comprising a third group on the image side of the second group, the third group being fixed in position during focusing. It is characterized by that.

An imaging lens according to an eighth invention is characterized in that, in the seventh invention, a cemented lens that satisfies the following conditional expressions (8) to (10) is included in the third group.
-1.0 <R3 / f <0 (8)
NL3p-NL3n> 0 (9)
−20 <νL3p−νL3n <0 (10)
However,
R3: radius of curvature of the joint surface,
f: focal length of the entire system,
NL3p: refractive index with respect to d-line of a positive lens having a cemented surface that satisfies conditional expression (8),
NL3n: refractive index with respect to d-line of a negative lens having a cemented surface that satisfies the conditional expression (8),
νL3p: Abbe number related to the d-line of a positive lens having a cemented surface that satisfies conditional expression (8),
νL3n: Abbe number related to the d-line of a negative lens having a cemented surface that satisfies conditional expression (8),
It is.

An imaging lens according to a ninth invention is the imaging lens according to any one of the first to eighth inventions, wherein the third lens and the fourth lens constitute a cemented lens, and the following conditional expression (11) and (12) is satisfied.
NL1p-NL1n> 0 (11)
−20 <νL1p−νL1n <0 (12)
However,
NL1p: refractive index with respect to d-line of the third lens,
NL1n: refractive index of the fourth lens with respect to the d-line,
νL1p: Abbe number related to the d-line of the third lens,
νL1n: Abbe number related to the d-line of the fourth lens,
It is.

In the imaging lens of a tenth invention according to any one of the first to ninth inventions, at least one negative lens in the first group satisfies the following conditional expressions (13) and (14): It is characterized by that.
(0.6425- [theta] gF) / [nu] d> 0.0015 (13)
νd <50 (14)
However,
θgF: partial dispersion ratio of lens material,
θgF = (Ng−NF) / (NF−NC)
Ng: refractive index for g-line,
NF: refractive index for F-line,
NC: Refractive index for C-line,
νd: Abbe number related to the d-line of the lens material,
It is.

The imaging lens of an eleventh aspect of the invention is characterized in that, in the eighth aspect of the invention, the following conditional expression (15) is satisfied.
-0.6 <φ3 / φ <0.6 (15)
However,
φ3: Power of the third group,
φ: Power of the entire system,
It is.

  The imaging lens of a twelfth aspect of the invention is characterized in that, in any one of the first to eleventh aspects of the invention, the second group includes only one negative lens.

  An imaging optical device according to a thirteenth aspect includes an imaging lens according to any one of the first to twelfth aspects, and an imaging element that converts an optical image formed on the imaging surface into an electrical signal. And the imaging lens is provided so that an optical image of a subject is formed on the imaging surface of the imaging device.

  According to a fourteenth aspect of the present invention, there is provided a digital apparatus including the imaging optical device according to the thirteenth aspect, to which at least one function of still image shooting and moving image shooting of a subject is added.

  According to the present invention, it is possible to realize a small imaging lens and an imaging optical apparatus in which the front lens diameter and the weight of the focus group are suppressed and the chromatic aberration is well corrected while being a large aperture medium telephoto lens having a bright F value. Can do. By using the imaging lens or the imaging optical device for a digital device (for example, a digital camera), it is possible to add a high-performance image input function to the digital device in a lightweight and compact manner.

The lens block diagram of 1st Embodiment (Example 1). The lens block diagram of 2nd Embodiment (Example 2). The lens block diagram of 3rd Embodiment (Example 3). The lens block diagram of 4th Embodiment (Example 4). The lens block diagram of 5th Embodiment (Example 5). FIG. 3 is a longitudinal aberration diagram of Example 1. FIG. 6 is a longitudinal aberration diagram of Example 2. FIG. 6 is a longitudinal aberration diagram of Example 3. FIG. 6 is a longitudinal aberration diagram of Example 4. FIG. 6 is a longitudinal aberration diagram of Example 5. FIG. 4 is a lateral aberration diagram of Example 1. FIG. 4 is a lateral aberration diagram of Example 2. FIG. 4 is a lateral aberration diagram of Example 3. FIG. 6 is a lateral aberration diagram of Example 4. FIG. 6 is a lateral aberration diagram of Example 5. FIG. 3 is a schematic diagram illustrating a schematic configuration example of a digital device including an imaging optical device.

Hereinafter, an imaging lens, an imaging optical device, and a digital device according to the present invention will be described. The imaging lens according to the present invention has at least a first group of positive power and a second group of positive power in order from the object side (power: an amount defined by the reciprocal of the focal length), and the first lens. The group has at least a first lens having positive power, a second lens having positive power, a third lens having positive power, and a fourth lens having negative power in order from the object side, Among the lenses constituting the second group, the lens closest to the object side is a positive lens, and at least one lens is a negative lens. In focusing from infinity to short distance, the first group is fixed in position, and at least the second group moves to the object side, and satisfies the following conditional expressions (1) and (2): It is said.
Nd1max−Nd1min> 0.1 (1)
νd1max−νd1min> 15 (2)
However, if the refractive index for the d-line is Nd and the Abbe number for the d-line is νd,
Nd1max: the maximum value of Nd of the positive lens in the first group,
Nd1min: the minimum value of Nd of the positive lens in the first group,
νd1max: the maximum value of νd of the positive lens in the first group,
νd1min: the minimum value of νd of the positive lens in the first group,
It is.

  In a telephoto type telephoto lens capable of shortening the total length, the off-axis light beam is greatly bent in the second group having negative power, so that the off-axis light beam passing through the first group has a relatively high height and ensures ambient illuminance. Therefore, there is a problem that the diameter of the front lens tends to be large. Further, when focusing is performed by movement of the second group, the height of off-axis rays passing through the second group greatly fluctuates, making it difficult to suppress fluctuations in off-axis aberrations due to focusing. Therefore, the use of the second group having positive power as the focus group facilitates a design that suppresses off-axis aberrations due to focusing, particularly fluctuations in field curvature. In addition, by adopting the inner focus method (inner focus method) in this way and reducing the weight of the focus group, it is possible to increase the autofocus speed and reduce the focus movement time. There are merits that a feeling can be obtained and a load of a motor can be reduced.

  In general, chromatic aberration can be satisfactorily reduced by using a lens made of a positive anomalous partial dispersion material such as fluorite for the lens group on the object side. However, since such a material has a low refractive index, it is necessary to increase the curvature of the lens surface in order to obtain a desired power. As a result, spherical aberration and field curvature are likely to occur. Further, the negative lens combined with the positive lens needs to shift to the low dispersion side as the material of the positive lens shifts to the low dispersion side. Even in this case, the curvature of the lens surface of the negative lens must be increased in order to satisfy the necessary achromatic condition. As a result, the amount of coma generated increases.

  If the lenses in the first lens group are arranged in positive and negative power arrangements in order from the object side and satisfy the conditional expressions (1) and (2), the curvature can be adjusted while using a positive lens with anomalous dispersion characteristics that suppress chromatic aberration. Since it is not made too strong, spherical aberration, coma aberration, curvature of field, etc. can be corrected well. Further, by making the most object-side lens in the second group a positive lens, it is possible to obtain an effect of reducing the focus weight by suppressing the height of the second and subsequent beams. Further, if the second group has at least one negative lens, the second group alone can suppress chromatic aberration, and thus an effect of maintaining good performance during focusing can be obtained.

  According to the above characteristic configuration, the focal length is long (for example, 135 equivalent focal length: 80 to 150) and the F value is bright (for example, FNO: 1.0 to 2.0). It is possible to realize a small imaging lens in which the front lens diameter and the weight of the focus group are suppressed and chromatic aberration is favorably corrected, and an imaging optical apparatus including the same. By using the imaging lens or imaging optical device in a digital device (for example, a digital camera), it becomes possible to add a high-performance image input function to the digital device in a lightweight and compact manner. It can contribute to cost, high performance and high functionality. For example, since the imaging lens according to the present invention is suitable as an interchangeable lens for a digital camera or a video camera, a lightweight and compact interchangeable lens that is convenient to carry can be realized. In the following, conditions for obtaining such effects in a well-balanced manner and achieving higher optical performance, light weight, downsizing, and the like will be described.

It is desirable to satisfy the following conditional expressions (1a) and (2a), and it is more desirable to satisfy the conditional expressions (1b) and (2b).
Nd1max−Nd1min> 0.15 (1a)
Nd1max−Nd1min> 0.2 (1b)
νd1max−νd1min> 20 (2a)
νd1max−νd1min> 30 (2b)
These conditional expressions (1a), (1b), (2a), and (2b) are more preferable based on the above viewpoints, etc., within the condition ranges defined by the conditional expressions (1) and (2). Specifies the condition range. Therefore, the above effects can be further enhanced by preferably satisfying conditional expressions (1a) and (2a), more preferably satisfying conditional expressions (1b) and (2b).

It is desirable to satisfy the following conditional expression (3).
φ2 / φ> 1.0 (3)
However,
φ2: Power of the second group,
φ: Power of the entire system,
It is.

  Conditional expression (3) defines a preferable condition range regarding the power of the second group. If the lower limit of conditional expression (3) is not reached, the power of the second lens group becomes weak and the focus movement amount tends to increase. Therefore, by satisfying conditional expression (3), it is possible to reduce the amount of focus movement of the second group and achieve a reduction in size of the imaging lens and improvement in aberration performance in a balanced manner.

It is desirable to satisfy the following conditional expression (3a), and it is more desirable to satisfy conditional expression (3b).
φ2 / φ> 1.2 (3a)
φ2 / φ> 1.4 (3b)
These conditional expressions (3a) and (3b) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (3). Therefore, the above effect can be further enhanced by preferably satisfying conditional expression (3a), more preferably satisfying conditional expression (3b).

It is desirable to satisfy the following conditional expressions (4) and (5).
0.1 <φ1 / φ <1.0 (4)
0 <φ1 / φ2 <0.5 (5)
However,
φ1: Power of the first group,
φ2: Power of the second group,
φ: Power of the entire system,
It is.

  Conditional expression (4) defines a preferable condition range regarding the power of the first group. If the lower limit of the conditional expression (4) is not reached, the power of the first group becomes weak and the whole system tends to be enlarged. Furthermore, since the lens diameter of the second group also increases, the focus weight tends to increase. If the upper limit of conditional expression (4) is exceeded, the power of the second group becomes relatively weak and the focus movement amount of the second group tends to increase. Therefore, by satisfying conditional expression (4), it is possible to reduce the focus weight and the amount of focus movement, and to achieve a reduction in weight and size of the imaging lens and improvement in aberration performance in a balanced manner.

  Conditional expression (5) defines a preferable range of the power ratio between the first group and the second group. If the lower limit of conditional expression (5) is not reached, the power of the second group becomes negative. As described above, it becomes difficult to increase the diameter of the front lens or to suppress fluctuations in off-axis aberrations due to focusing. Telephoto type problems such as If the upper limit of conditional expression (5) is exceeded, the power of the second lens group becomes relatively weak and the focus movement amount tends to increase. That is, by using the second group having a positive power as the focus group, it becomes easy to suppress the off-axis aberration, particularly the field curvature fluctuation due to focusing. Therefore, by satisfying conditional expression (5), it is possible to reduce the amount of focus movement and achieve a good balance between downsizing the imaging lens and improving aberration performance.

It is desirable to satisfy the following conditional expressions (4a) and (5a), and it is more desirable to satisfy the conditional expressions (4b) and (5b).
0.2 <φ1 / φ <0.75 (4a)
0.2 <φ1 / φ <0.5 (4b)
0 <φ1 / φ2 <0.4 (5a)
0.1 <φ1 / φ2 <0.3 (5b)
These conditional expressions (4a), (4b), (5a), and (5b) are more preferable based on the above viewpoints, etc., within the condition ranges defined by the conditional expressions (4) and (5). Specifies the condition range. Therefore, the above effects can be further enhanced by preferably satisfying conditional expressions (4a) and (5a), more preferably satisfying conditional expressions (4b) and (5b).

It is desirable to satisfy the following conditional expression (6).
D1Gr / D2Gr> 1.5 (6)
However, if the diameter of the parallel light beam that enters the lens from the object side to the full aperture that determines the F value is the Fno light beam diameter,
D1Gr: Maximum Fno beam diameter in the first group,
D2Gr: maximum Fno beam diameter in the second group,
It is.

  Conditional expression (6) defines a preferable range of the maximum Fno beam diameter ratio between the first group and the second group. If the lower limit of conditional expression (6) is not reached, the lens diameter of the second group increases and the focus weight tends to increase. Therefore, by satisfying the conditional expression (6), it is possible to reduce the focus weight and achieve a good balance between the reduction in weight and size of the imaging lens and the improvement in aberration performance.

It is more desirable to satisfy the following conditional expression (6a).
D1Gr / D2Gr> 1.7 (6a)
The conditional expression (6a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (6). Therefore, the above effect can be further enhanced preferably by satisfying conditional expression (6a).

It is desirable to satisfy the following conditional expression (7).
1.4 <DG1F / IMG <1.8 (7)
However,
DG1F: effective radius of the object side surface of the first lens,
IMG: Effective radius of image circle,
It is.

  Conditional expression (7) defines a preferable range of the ratio of the effective diameter on the object side of the first lens to the effective diameter of the image circle (that is, the effective image circle diameter) representing the range that can be imaged on the image plane (the range that can be photographed). doing. When the upper limit of conditional expression (7) is exceeded, the front lens diameter tends to be too large, and when the lower limit of conditional expression (7) is exceeded, it becomes difficult to secure the peripheral light amount. In order to secure the peripheral light amount, it is necessary to shorten the total length. As a result, the aberration (spherical aberration, curvature of field, etc.) tends to deteriorate due to the increase in power of the first group. Therefore, by satisfying conditional expression (7), it is possible to achieve a reduction in weight and size of the imaging lens and improvement in aberration performance in a balanced manner.

  It is desirable to have an aperture stop in the second group. If an aperture stop is disposed in the second group, the stop diameter can be reduced, and the weight of the focus group can be reduced. In addition, off-axis performance fluctuations (for example, field curvature fluctuations) during focusing can be suppressed.

  It is desirable that a third group is further provided on the image side of the second group, and the third group is fixed in position during focusing. By providing the third group with a fixed focus position, it becomes possible to control various aberrations without increasing the focus weight.

It is desirable that a cemented lens that satisfies the following conditional expressions (8) to (10) is included in the third group.
-1.0 <R3 / f <0 (8)
NL3p-NL3n> 0 (9)
−20 <νL3p−νL3n <0 (10)
However,
R3: radius of curvature of the joint surface,
f: focal length of the entire system,
NL3p: refractive index with respect to d-line of a positive lens having a cemented surface that satisfies conditional expression (8),
NL3n: refractive index with respect to d-line of a negative lens having a cemented surface that satisfies the conditional expression (8),
νL3p: Abbe number related to the d-line of a positive lens having a cemented surface that satisfies conditional expression (8),
νL3n: Abbe number related to the d-line of a negative lens having a cemented surface that satisfies conditional expression (8),
It is.

  For example, in the case of a three-piece cemented lens having one cemented surface that satisfies the conditional expression (8), it is preferable that the positive lens and the negative lens that form the cemented surface satisfy the conditional expressions (9) and (10). In the case of a three-piece cemented lens having two cemented surfaces that satisfy the conditional expression (8), the positive lens and the negative lens that form one of the cemented surfaces satisfy the conditional expressions (9) and (10). Is preferred.

  Conditional expressions (8) to (10) define a preferable range for the cemented lens disposed in the third group. The cemented surface that satisfies the conditional expression (8) is a cemented surface with the concave surface facing the object side, and is composed of the image side surface of the positive lens and the object side surface of the negative lens. According to the configuration including the cemented lens satisfying the conditional expressions (8) to (10) in the third group, the remaining spherical aberration is adjusted by controlling the spherical aberration while suppressing the fluctuation of other aberrations on the cemented surface. Easy to do.

It is further desirable to satisfy the following conditional expressions (8a) to (10a).
−0.6 <R3 / f <−0.2 (8a)
NL3p-NL3n> 0.05 (9a)
−10 <νL3p−νL3n <0 (10a)
These conditional expressions (8a) to (10a) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expressions (8) to (10). Therefore, the above effect can be further enhanced preferably by satisfying conditional expressions (8a) to (10a).

It is desirable that the third lens and the fourth lens constitute a cemented lens and satisfy the following conditional expressions (11) and (12).
NL1p-NL1n> 0 (11)
−20 <νL1p−νL1n <0 (12)
However,
NL1p: refractive index with respect to d-line of the third lens,
NL1n: refractive index of the fourth lens with respect to the d-line,
νL1p: Abbe number related to the d-line of the third lens,
νL1n: Abbe number related to the d-line of the fourth lens,
It is.

  Conditional expressions (11) and (12) define a preferred range for positive and negative cemented lenses arranged in the first group. According to the configuration in which the cemented lens satisfying the conditional expressions (11) and (12) is included in the first group, other aberrations occur on the cemented surface including the image side surface of the third lens and the object side surface of the fourth lens. It becomes easy to adjust the residual coma aberration by controlling the coma aberration while suppressing the fluctuation.

It is further desirable to satisfy the following conditional expressions (11a) and (12a).
NL1p-NL1n> 0.05 (11a)
−10 <νL1p−νL1n <0 (12a)
The conditional expressions (11a) and (12a) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expressions (11) and (12). Therefore, the above effect can be further increased preferably by satisfying conditional expressions (11a) and (12a).

It is desirable that at least one negative lens in the first group satisfies the following conditional expressions (13) and (14).
(0.6425- [theta] gF) / [nu] d> 0.0015 (13)
νd <50 (14)
However,
θgF: partial dispersion ratio of lens material,
θgF = (Ng−NF) / (NF−NC)
Ng: refractive index for g-line,
NF: refractive index for F-line,
NC: Refractive index for C-line,
νd: Abbe number related to the d-line of the lens material,
It is.

  Conditional expressions (13) and (14) define a preferable range regarding the partial dispersion ratio and the like of at least one negative lens arranged in the first group. According to this configuration, other aberrations can be suppressed while suppressing chromatic aberrations more effectively.

  Specific examples of the lens material that satisfies the conditional expressions (13) and (14) include the following glass materials. In addition, similar effects can be obtained even when glass materials not described below have equivalent optical performance.

  As glass materials manufactured by HOYA Corporation, E-FEL1, E-FEL2, E-FL5, E-FL6, E-F2, E-F5, BAFD7, BAFD8, LAF2, NBF1, NBFD3, NBFD10, NBFD11, NBFD13, NBFD15, NBFD15-W, TAF1, TAF3, TAFD5F, TAFD25, TAFD30, TAFD33, TAFD35, TAFD37, TAFD45, BAF10, BAF11, E-ADF10, E-ADF50, E-BAF8, E-F1, E-F3, E-F8, E-FEL6, LAF3, NBFD12, TAF2, TAF4, TAF5, M-LAF81, M-NBF1, M-NBFD10, M-NBFD130, M-TAF1, M-TAF31, M-TAF101, M-TAF105, M-TAF4 1, MP-TAF401, M-TAFD51, M-TAFD305, M-TAFD307 the like.

  As glass materials manufactured by OHARA INC., S-BSM28, S-BAM3, S-BAM4, S-BAM12, S-BAH10, S-BAH11, S-BAH27, S-BAH28, S-BAH32, S-TIL 1 , S-TIL 2, S-TIL 6, S-TIL 25, S-TIL 26, S-TIL 27, S-TIM 2, S-TIM 3, S-TIM 5, S-TIM 8, S-LAM 2, S- LAM 3, S-LAM 7, S-LAM 51, S-LAM 52, S-LAM 54, S-LAM 55, S-LAM 58, S-LAM 59, S-LAM 60, S-LAM 61, S-LAM 66, S-LAH 51, S- LAH52, S-LAH53, S-LAH55V, S-LAH58, S-LAH59, S-LAH60, S-LAH63, S-LAH64, S LAH65V, S-LAH66, S-LAH71, S-LAH79, S-LAH88, S-LAH89, S-LAH92, S-NBM51, S-NBH5, S-NBH8, S-NBH51, S-NBH52, S- Examples include NBH53, L-LAM60, L-LAM69, L-LAH53, L-LAH84, L-LAH85V, L-LAH86, L-LAH90, and L-LAH91.

  As glass materials manufactured by Kogaku Glass Co., Ltd., J-KZFH1, J-BAF3, J-BAF4, J-BAF8, J-BAF10, J-BAF11, J-BAF12, J-BASF6, J-BASF7, J-BASF8, J -SSK8, J-LLF1, J-LLF2, J-LLF6, J-LF5, J-LF6, J-LF7, J-F1, J-F2, J-F3, J-F5, J-F8, J-LAF2 , J-LAF3, J-LAF7, J-LAF01, J-LAF02, J-LAF04, J-LAF05, J-LAF09, J-LAF010, J-LAF016, J-LASF01, J-LASF02, J-LASF03, J -LASF05, J-LASF08, J-LASF09, J-LASF010, J-LASF013, J-LASF014, J-LASF 15, J-LASF016, J-LASF017, J-LASFH2, J-LASFH6, J-LASFH9, J-LASFH13 the like.

It is more desirable to satisfy the following conditional expression (14a).
νd <40 (14a)
This conditional expression (14a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (14). Therefore, the above effect can be further enhanced preferably by satisfying conditional expression (14a).

It is desirable to satisfy the following conditional expression (15).
-0.6 <φ3 / φ <0.6 (15)
However,
φ3: Power of the third group,
φ: Power of the entire system,
It is.

  Conditional expression (15) defines a preferable condition range regarding the power of the third group. If the power of the third group is set within the range of the conditional expression (15), the power of the third group becomes small, so that the occurrence of aberration can be suppressed. Therefore, it is possible to obtain the maximum effect of suppressing the spherical aberration by the third group alone (that is, the effect of easily adjusting the remaining spherical aberration by controlling the spherical aberration while suppressing the fluctuation of other aberrations).

It is desirable to satisfy the following conditional expression (15a), and it is more desirable to satisfy conditional expression (15b).
−0.4 <φ3 / φ <0.4 (15a)
-0.2 <φ3 / φ <0.2 (15b)
These conditional expressions (15a) and (15b) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (15). Therefore, the above effect can be further enhanced by preferably satisfying conditional expression (15a), more preferably satisfying conditional expression (15b).

  It is desirable that only one negative lens is included in the second group. By using only one negative lens included in the second group, the focus weight can be effectively suppressed.

  The imaging lens according to the present invention is suitable for use as an imaging lens for a digital device with an image input function (for example, an interchangeable lens digital camera). Therefore, it is possible to configure an imaging optical device that takes in and outputs as an electrical signal. The imaging optical device is an optical device that constitutes a main component of a camera used for still image shooting and moving image shooting of a subject, for example, an imaging lens that forms an optical image of an object in order from the object (that is, subject) side, And an imaging device that converts an optical image formed by the imaging lens into an electrical signal. Then, the imaging lens having the above-described characteristic configuration is arranged so that an optical image of the subject is formed on the light receiving surface (that is, the imaging surface) of the imaging device, and thus has high performance at a small size, low cost. An imaging optical device and a digital device including the imaging optical device can be realized.

  Examples of digital devices with an image input function include cameras such as digital cameras, video cameras, surveillance cameras, security cameras, in-vehicle cameras, and videophone cameras. In addition, personal computers, portable digital devices (for example, mobile phones, smart phones (high performance mobile phones), tablet terminals, mobile computers, etc.), peripheral devices (scanners, printers, mice, etc.), and other digital devices (drives) Recorders, defense equipment, etc.) with built-in or external camera functions. As can be seen from these examples, it is possible not only to configure a camera by using an imaging optical device, but also to add a camera function by mounting the imaging optical device on various devices. For example, a digital device with an image input function such as a mobile phone with a camera can be configured.

  FIG. 16 is a schematic cross-sectional view showing a schematic configuration example of a digital device DU as an example of a digital device with an image input function. The imaging optical device LU mounted on the digital device DU shown in FIG. 16 includes an imaging lens LN (AX: optical axis) that forms an optical image (image plane) IM of the object in order from the object (namely, subject) side, An imaging element SR that converts the optical image IM formed on the light receiving surface (imaging surface) SS by the imaging lens LN into an electrical signal, and a parallel flat plate (for example, the imaging element SR) as necessary. (Corresponding to an optical filter such as an optical low-pass filter and an infrared cut filter, which are arranged as necessary). When a digital device DU with an image input function is constituted by this imaging optical device LU, the imaging optical device LU is usually arranged inside the body, but when necessary to realize the camera function, a form as necessary is adopted. Is possible. For example, the unitized imaging optical device LU can be configured to be detachable or rotatable with respect to the main body of the digital device DU.

  The imaging lens LN is an imaging lens having a three-group configuration. By moving the second group of positive power toward the object side along the optical axis AX while fixing the positions of the first group and the third group, the imaging lens LN is infinite. An inner focus method that performs focusing from a long distance to a short distance is adopted, and an optical image IM is formed on the light receiving surface SS of the image sensor SR. As the image sensor SR, for example, a solid-state image sensor such as a CCD image sensor or a CMOS image sensor having a plurality of pixels is used. Since the imaging lens LN is provided so that the optical image IM of the subject is formed on the light receiving surface SS which is a photoelectric conversion unit of the imaging element SR, the optical image IM formed by the imaging lens LN is the imaging element. It is converted into an electric signal by SR.

  The digital device DU includes a signal processing unit 1, a control unit 2, a memory 3, an operation unit 4, a display unit 5 and the like in addition to the imaging optical device LU. The signal generated by the image sensor SR is subjected to predetermined digital image processing, image compression processing, and the like in the signal processing unit 1 as necessary, and recorded as a digital video signal in the memory 3 (semiconductor memory, optical disc, etc.) In some cases, it is transmitted to other devices via a cable or converted into an infrared signal or the like (for example, a communication function of a mobile phone). The control unit 2 is composed of a microcomputer, and controls functions such as shooting functions (still image shooting function, movie shooting function, etc.) and image playback functions; focusing, lens movement mechanism control for camera shake correction, etc. Do it. For example, the control unit 2 controls the imaging optical device LU so as to perform at least one of still image shooting and moving image shooting of a subject. The display unit 5 includes a display such as a liquid crystal monitor, and performs image display using an image signal converted by the image sensor SR or image information recorded in the memory 3. The operation unit 4 is a part including operation members such as an operation button (for example, a release button) and an operation dial (for example, a shooting mode dial), and transmits information input by the operator to the control unit 2.

  Next, specific optical configurations of the imaging lens LN will be described in more detail with reference to first to fifth embodiments. 1 to 5 are lens configuration diagrams corresponding to the imaging lenses LN constituting the first to fifth embodiments, respectively, and the lens arrangement at the first focus position POS1 (subject infinite state) is an optical cross section. Is shown. The first, second and fourth embodiments have a positive / positive three-group structure, and the third and fifth embodiments have a positive / negative three-group structure. During focusing, the first group Gr1 and With the position of the third group Gr3 fixed, the second group Gr2 moves to the object side along the optical axis AX. That is, the second group Gr2, which is the focus group, moves from the first focus position POS1 to the second focus position POS2 (subject close-up state) in focusing from infinity to a short distance, as indicated by an arrow mF. To do.

  In the first to third embodiments, the first group Gr1 includes, in order from the object side, a first lens L11 having positive power, a second lens L12 having positive power, and a third lens L13 having positive power. And a fourth lens L14 having negative power (power arrangement of first to fourth lenses L11 to L14: positive, positive, negative). In the fourth embodiment, the first group Gr1 includes, in order from the object side, a first lens L11 having positive power, a second lens L12 having positive power, a third lens L13 having positive power, and a negative power. The lens includes a fourth lens L14 having power and a fifth lens L15 having negative power (power arrangement of the first to fifth lenses L11 to L15: positive / positive / negative / negative). In the fifth embodiment, in order from the object side, the first group Gr1 includes a first lens L11 having positive power, a second lens L12 having positive power, a third lens L13 having positive power, and a negative power. The lens includes a fourth lens L14 having power and a fifth lens L15 having positive power (power arrangement of the first to fifth lenses L11 to L15: positive / positive / negative / positive).

  In the first, third, and fifth embodiments, the third lens L13 and the fourth lens L14 constitute a cemented lens. In the first to fifth embodiments, among the lenses constituting the second group Gr2, the lens L21 closest to the object side is a positive lens, and the negative lens is only one of a biconcave negative lens L22. In the first to fifth embodiments, the aperture stop ST is disposed between the lens L21 and the lens L22 in the second group Gr2. In the first to fourth embodiments, the third lens group Gr3 includes a cemented lens including a positive lens L31 and a negative lens L32. In the fifth embodiment, the third lens group Gr3 is a negative lens. It is composed of a single cemented lens composed of L31, a positive lens L32, and a negative lens L33.

  In the imaging lens LN (FIG. 1) of the first embodiment, each group is configured as follows in order from the object side. The first group Gr1 includes two positive meniscus lenses L11 and L12 that are convex on the object side, and a cemented lens that includes a biconvex positive lens L13 and a biconcave negative lens L14. The second group Gr2 includes a positive meniscus lens L21 convex on the object side, an aperture stop ST, a biconcave negative lens L22, a biconvex positive lens L23, and a biconvex positive lens L24 (double-sided aspheric surface). , Is composed of. The third group Gr3 includes a cemented lens including a positive meniscus lens L31 convex to the image side and a biconcave negative lens L32, and a biconvex positive lens L33.

  In the imaging lens LN (FIG. 2) of the second embodiment, each group is configured as follows in order from the object side. The first group Gr1 includes three positive meniscus lenses L11, L12, and L13 that are convex on the object side, and a negative meniscus lens L14 that is concave on the image side. The second group Gr2 includes a positive meniscus lens L21 convex toward the object side, an aperture stop ST, a biconcave negative lens L22, and two biconvex positive lenses L23 and L24. The third group Gr3 includes a cemented lens including a positive meniscus lens L31 convex on the image side and a biconcave negative lens L32, and a positive meniscus lens L33 convex on the object side.

  In the imaging lens LN (FIG. 3) of the third embodiment, each group is configured as follows in order from the object side. The first group Gr1 includes two positive meniscus lenses L11 and L12 that are convex on the object side, and a cemented lens that includes a biconvex positive lens L13 and a biconcave negative lens L14. The second group Gr2 includes a positive meniscus lens L21 convex on the object side, an aperture stop ST, a biconcave negative lens L22, a biconvex positive lens L23, and a biconvex positive lens L24 (double-sided aspheric surface). , Is composed of. The third group Gr3 includes a cemented lens including a positive meniscus lens L31 convex to the image side and a biconcave negative lens L32, and a biconvex positive lens L33.

  In the imaging lens LN (FIG. 4) of the fourth embodiment, each group is configured as follows in order from the object side. The first lens unit Gr1 includes a cemented lens including two positive meniscus lenses L11 and L12 convex on the object side, a positive meniscus lens L13 convex on the object side, and a negative meniscus lens L14 concave on the image side, and an image side. And a concave negative meniscus lens L15. The second group Gr2 includes a positive meniscus lens L21 convex toward the object side, an aperture stop ST, a biconcave negative lens L22, and two biconvex positive lenses L23 and L24. The third group Gr3 includes a cemented lens including a positive meniscus lens L31 convex to the image side and a biconcave negative lens L32, and a biconvex positive lens L33.

  In the imaging lens LN (FIG. 5) of the fifth embodiment, each group is configured as follows in order from the object side. The first group Gr1 includes two positive meniscus lenses L11 and L12 convex on the object side, a cemented lens including a biconvex positive lens L13 and a biconcave negative lens L14, and a positive meniscus lens L15 convex on the object side. And is composed of. The second group Gr2 includes a positive meniscus lens L21 (double-sided aspheric surface) convex toward the object side, an aperture stop ST, a biconcave negative lens L22, and two biconvex positive lenses L23 and L24. Has been. The third group Gr3 includes a cemented lens including a biconcave negative lens L31, a biconvex positive lens L32, and a negative meniscus lens L33 concave on the object side.

  Hereinafter, the configuration and the like of the imaging lens embodying the present invention will be described more specifically with reference to the construction data of the examples. Examples 1 to 5 (EX1 to 5) listed here are numerical examples corresponding to the first to fifth embodiments, respectively, and are lens configuration diagrams illustrating the first to fifth embodiments. (FIGS. 1 to 5) show the optical configurations of the corresponding Examples 1 to 5, respectively.

  In the construction data of each embodiment, as surface data, in order from the left column, surface number i (OB: object surface, ST: aperture surface, IM: image surface), radius of curvature r (mm) in paraxial, axial upper surface The distance d (mm), the refractive index Nd for the d line (wavelength: 587.56 nm), and the Abbe number νd for the d line are shown. Note that the variable shaft upper surface distance di (i: surface number, mm) that changes due to focusing is shown for each of the first focus position POS1 to the second focus position POS2.

The surface with * in the surface number i is an aspheric surface, and the surface shape is defined by the following formula (AS) using a local orthogonal coordinate system (x, y, z) with the surface vertex as the origin. The As aspheric data, an aspheric coefficient or the like is shown. It should be noted that the coefficient of the term not described in the aspherical data of each example is 0, and E−n = × 10 ⁻ⁿ for all data.
z = (c · h ² ) / [1 + √ {1− (1 + K) · c ² · h ² }] + Σ (Aj · h ^j ) (AS)
However,
h: height in the direction perpendicular to the z axis (optical axis AX) (h ² = x ² + y ² ),
z: the amount of sag in the direction of the optical axis AX at the position of the height h (based on the surface vertex),
c: curvature at the surface vertex (the reciprocal of the radius of curvature r),
K: conic constant,
Aj: j-order aspheric coefficient,
It is.

  As various data, the focal length f (mm, 135 converted value = f × 21.6 / y′max), F number (F value) FNO. , Full field angle 2ω (°), maximum image height y′max (mm), total lens length TL (mm), back focus BF (mm), focal length f1 (mm) of the first group Gr1, and second group Gr2. Focal length f2 (mm), focal length f3 (mm) of the third group Gr3, maximum Fno beam diameter D1Gr (mm) in the first group Gr1, maximum Fno beam diameter D2Gr (mm) in the second group Gr2, The effective radius DG1F (mm) of the object side surface of one lens L11, the effective radius IMG (mm) of the image circle, and the partial dispersion ratio θgF of the negative lens in the first group Gr1 are shown. However, in the back focus BF, the distance from the lens final surface to the paraxial image surface is expressed in terms of air length, and the total lens length TL is obtained by adding the back focus BF to the distance from the lens front surface to the lens final surface. Is. Table 1 shows values corresponding to the conditional expressions of the respective examples.

  6 to 10 are longitudinal aberration diagrams corresponding to Examples 1 to 5 (EX1 to EX5), respectively. (A) to (C) are the first focus positions POS1 and (D) to (F). Indicates various aberrations at the second focus position POS2. 6 to 10, (A) and (D) are spherical aberration diagrams, (B) and (E) are astigmatism diagrams, and (C) and (F) are distortion aberration diagrams.

  The spherical aberration diagram shows the amount of spherical aberration with respect to the C line (wavelength 656.28 nm) indicated by the alternate long and short dash line, the amount of spherical aberration with respect to the d line (wavelength 587.56 nm) indicated by the solid line, and the g line (wavelength 435.84 nm) indicated by the broken line. The amount of spherical aberration is represented by the amount of deviation (mm) in the optical axis AX direction from the paraxial image plane, and the vertical axis represents the F value. In the astigmatism diagram, the broken line M represents the meridional image plane with respect to the d-line, and the solid line S represents the sagittal image plane with respect to the d-line in terms of the deviation (mm) in the optical axis AX direction from the paraxial image plane. The axis represents the image height Y ′ (mm). In the distortion diagram, the horizontal axis represents the distortion (%) with respect to the d line, and the vertical axis represents the image height Y ′ (mm). Note that the image height Y ′ corresponds to the maximum image height y′max (half the diagonal length of the light receiving surface SS of the image sensor SR) on the image plane IM.

  FIGS. 11 to 15 are lateral aberration diagrams corresponding to Examples 1 to 5 (EX1 to EX5), respectively. In each of FIGS. 11 to 15, (A) to (C) are lateral aberration (mm) at the first focus position POS1, and (D) to (F) are lateral aberration (mm) at the second focus position POS2. The meridional coma aberration at each image height Y ′ is shown.

Example 1
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
0 (OB) ∞ ∞ 〜414.98
1 53.755 3.93 1.67790 50.7
2 350.142 0.09
3 22.513 6.50 1.57300 66.2
4 57.815 1.37
5 69.005 5.29 1.80520 25.5
6 -666.360 1.37 1.68890 31.2
7 15.095 9.37-3.48
8 17.134 1.75 1.8348 42.7
9 22.970 3.00
10 (ST) ∞ 2.54
11 -33.605 0.70 1.69890 30.1
12 23.715 3.06
13 40.309 2.50 1.80420 46.5
14 -142.127 0.09
15 * 47.035 3.50 1.72920 54.7
16 * -39.742 1.22-7.11
17 -44.803 2.21 1.80810 22.8
18 -21.006 1.15 1.68890 31.2
19 28.815 1.32
20 47.925 3.08 1.87350 38.5
21 -48.505 19.67
22 (IM) ∞

Aspheric data 15th surface
K = 0.00000E + 00
A4 = -0.11123E-04
A6 = -0.44679E-07
A8 = 0.50592E-09
A10 = -0.78074E-11

Aspheric data 16th surface
K = 0.00000E + 00
A4 = -0.48511E-05
A6 = -0.24615E-07
A8 = 0.66312E-11
A10 = -0.46542E-11

Various data
f = 51.46
FNO. = 1.45
2ω = 23.76
y'max = 10.8
TL = 72.67
BF = 19.67
f1 = 145.0
f2 = 35.9
f3 = 364.8
D1Gr = 35.5 (first side)
D2Gr = 19.6 (8th surface)
DG1F = 18.4
IMG = 10.8
θgF = 0.599 (L14)

Example 2
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
0 (OB) ∞ ∞ to 364.78
1 34.147 6.04 1.72920 54.7
2 156.973 0.09
3 25.518 5.25 1.49700 81.6
4 48.788 2.55
5 90.036 3.78 1.48750 70.4
6 165.925 0.45
7 144.500 1.40 1.63980 34.6
8 15.362 11.08 to 4.35
9 29.365 1.70 1.83480 42.7
10 67.786 1.50
11 (ST) ∞ 2.45
12 -22.171 0.70 1.69890 30.1
13 31.585 2.73
14 288.292 2.81 1.80610 33.3
15 -46.685 0.09
16 46.842 4.47 1.72920 54.7
17 -29.823 0.94 to 7.67
18 -373.884 3.48 1.80520 25.5
19 -22.010 1.15 1.72820 28.3
20 22.039 1.25
21 28.059 2.74 1.91080 35.3
22 598.454 19.31
23 (IM) ∞

Various data
f = 51.48
FNO. = 1.45
2ω = 23.88
y'max = 10.8
TL = 75.98
BF = 19.31
f1 = 161.0
f2 = 33.1
f3 = 2095.5
D1Gr = 35.5 (first side)
D2Gr = 19.6 (17th surface)
DG1F = 18.3
IMG = 10.8
θgF = 0.592 (L14)

Example 3
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
0 (OB) ∞ ∞ 〜414.98
1 30.472 5.79 1.61800 63.4
2 108.887 0.09
3 22.612 6.50 1.49700 81.6
4 71.822 1.42
5 113.717 2.77 1.90370 31.3
6 -419.470 1.25 1.65410 39.7
7 14.722 9.28 to 4.18
8 19.978 1.65 1.83480 42.7
9 28.826 2.50
10 (ST) ∞ 3.04
11 -24.932 0.75 1.69890 30.1
12 30.794 2.61
13 45.216 2.50 1.80420 46.5
14 -74.605 0.09
15 * 63.820 3.45 1.74320 49.3
16 * -32.854 1.18 to 6.31
17 -32.560 1.76 1.95370 32.3
18 -20.560 1.15 1.64770 33.8
19 39.391 1.28
20 116.615 3.89 1.91080 35.3
21 -46.086 19.70
22 (IM) ∞

Aspheric data 15th surface
K = 0.00000E + 00
A4 = -0.93344E-05
A6 = 0.58978E-07
A8 = 0.10523E-09

Aspheric data 16th surface
K = -0.77799E-01
A4 = 0.21185E-05
A6 = 0.55563E-07

Various data
f = 51.45
FNO. = 1.45
2ω = 23.76
y'max = 10.8
TL = 72.67
BF = 19.70
f1 = 136.4
f2 = 32.9
f3 = -2137.9
D1Gr = 35.5 (first side)
D2Gr = 19.6 (8th surface)
DG1F = 17.8
IMG = 10.8
θgF = 0.574 (L14)

Example 4
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
0 (OB) ∞ ∞ to 364.78
1 33.464 5.06 1.80450 45.5
2 85.716 0.09
3 37.837 2.20 1.83810 42.7
4 47.721 0.09
5 24.052 5.44 1.49700 81.6
6 65.150 1.25 1.60340 38.0
7 27.016 2.40
8 41.362 1.25 1.74580 27.5
9 16.149 10.81 to 3.61
10 26.423 1.57 1.83480 42.7
11 47.386 1.82
12 (ST) ∞ 3.06
13 -25.777 0.70 1.69890 30.1
14 36.085 2.13
15 128.492 2.49 1.80610 33.3
16 -56.272 0.09
17 46.544 4.24 1.72920 54.7
18 -36.939 0.98 to 8.18
19 -43.992 1.90 1.90370 31.3
20 -22.851 1.15 1.64770 33.8
21 28.683 1.25
22 41.944 2.78 1.91080 35.3
23 -85.981 20.44
24 (IM) ∞

Various data
f = 52.25
FNO. = 1.45
2ω = 23.52
y'max = 10.8
TL = 73.19
BF = 20.44
f1 = 152.7
f2 = 36.3
f3 = 429.5
D1Gr = 36.0 (first side)
D2Gr = 19.7 (10th surface)
DG1F = 19.4
IMG = 10.8
θgF = 0.583 (L14)

Example 5
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
0 (OB) ∞ ∞ 〜414.98
1 29.454 5.85 1.61800 63.4
2 88.264 0.09
3 28.490 5.74 1.49700 81.6
4 125.746 1.36
5 173.734 2.81 1.80810 22.8
6 -136.555 1.25 1.69890 30.1
7 14.785 1.21
8 15.391 3.29 1.80810 22.8
9 18.264 8.72 to 2.72
10 * 17.718 1.80 1.74320 49.3
11 * 23.185 2.57
12 (ST) ∞ 3.05
13 -32.405 0.70 1.75520 27.5
14 30.415 2.09
15 57.491 2.60 1.83480 42.7
16 -52.541 0.09
17 185.151 2.60 1.89190 37.1
18 -34.923 1.25-7.25
19 -35.396 1.15 1.68890 31.2
20 229.095 3.48 1.88300 40.8
21 -23.024 1.15 1.58 140 40.9
22 -129.976 20.40
23 (IM) ∞

Aspheric data 10th surface
K = 0.00000E + 00
A4 = -0.26752E-05
A6 = 0.65045E-08
A8 = -0.96869E-08
A10 = 0.14711E-09
A12 = -0.15144E-11
A14 = 0.48148E-14

Aspheric data 11th surface
K = 0.00000E + 00
A4 = 0.17164E-04
A6 = -0.23747E-06
A8 = -0.40655E-08
A10 = 0.67655E-10
A12 = -0.11248E-11
A14 = 0.47608E-14

Various data
f = 51.45
FNO. = 1.45
2ω = 23.9
y'max = 10.8
TL = 73.26
BF = 20.40
f1 = 138.0
f2 = 35.9
f3 = -5499.3
D1Gr = 35.5 (first side)
D2Gr = 19.4 (10th surface)
DG1F = 18.1
IMG = 10.8
θgF = 0.603 (L14)

DU Digital equipment LU Imaging optical device LN Imaging lens Gr1 First group Gr2 Second group Gr3 Third group L11, L12, L13, L14 Lens (first to fourth lenses)
ST Aperture stop (aperture face)
SR Image sensor SS Light-receiving surface (imaging surface)
IM image plane (optical image)
AX Optical axis 1 Signal processing unit 2 Control unit 3 Memory 4 Operation unit 5 Display unit

Claims (14)

In order from the object side, it has at least a first group of positive power and a second group of positive power,
The first group includes at least a first lens having positive power, a second lens having positive power, a third lens having positive power, and a fourth lens having negative power in order from the object side. And
Among the lenses constituting the second group, the most object side lens is a positive lens, and at least one lens is a negative lens,
When focusing from infinity to short distance, the first group is fixed in position, and at least the second group moves to the object side,
An imaging lens that satisfies the following conditional expressions (1) and (2):
Nd1max−Nd1min> 0.1 (1)
νd1max−νd1min> 15 (2)
However, if the refractive index for the d-line is Nd and the Abbe number for the d-line is νd,
Nd1max: the maximum value of Nd of the positive lens in the first group,
Nd1min: the minimum value of Nd of the positive lens in the first group,
νd1max: the maximum value of νd of the positive lens in the first group,
νd1min: the minimum value of νd of the positive lens in the first group,
It is. The imaging lens according to claim 1, wherein the following conditional expression (3) is satisfied:
φ2 / φ> 1.0 (3)
However,
φ2: Power of the second group,
φ: Power of the entire system,
It is. The imaging lens according to claim 1 or 2, wherein the following conditional expressions (4) and (5) are satisfied:
0.1 <φ1 / φ <1.0 (4)
0 <φ1 / φ2 <0.5 (5)
However,
φ1: Power of the first group,
φ2: Power of the second group,
φ: Power of the entire system,
It is. The imaging lens according to claim 1, wherein the following conditional expression (6) is satisfied:
D1Gr / D2Gr> 1.5 (6)
However, if the diameter of the parallel light beam that enters the lens from the object side to the full aperture that determines the F value is the Fno light beam diameter,
D1Gr: Maximum Fno beam diameter in the first group,
D2Gr: maximum Fno beam diameter in the second group,
It is. The imaging lens according to claim 1, wherein the following conditional expression (7) is satisfied:
1.4 <DG1F / IMG <1.8 (7)
However,
DG1F: effective radius of the object side surface of the first lens,
IMG: Effective radius of image circle,
It is.   The imaging lens according to claim 1, further comprising an aperture stop in the second group.   The imaging lens according to claim 1, further comprising a third group on an image side of the second group, wherein the third group is fixed in position during focusing. The imaging lens according to claim 7, wherein a cemented lens that satisfies the following conditional expressions (8) to (10) is included in the third group.
-1.0 <R3 / f <0 (8)
NL3p-NL3n> 0 (9)
−20 <νL3p−νL3n <0 (10)
However,
R3: radius of curvature of the joint surface,
f: focal length of the entire system,
NL3p: refractive index with respect to d-line of a positive lens having a cemented surface that satisfies conditional expression (8),
NL3n: refractive index with respect to d-line of a negative lens having a cemented surface that satisfies the conditional expression (8),
νL3p: Abbe number related to the d-line of a positive lens having a cemented surface that satisfies conditional expression (8),
νL3n: Abbe number related to the d-line of a negative lens having a cemented surface that satisfies conditional expression (8),
It is. 9. The cemented lens is constituted by the third lens and the fourth lens, and satisfies the following conditional expressions (11) and (12): 9. Imaging lens;
NL1p-NL1n> 0 (11)
−20 <νL1p−νL1n <0 (12)
However,
NL1p: refractive index with respect to d-line of the third lens,
NL1n: refractive index of the fourth lens with respect to the d-line,
νL1p: Abbe number related to the d-line of the third lens,
νL1n: Abbe number related to the d-line of the fourth lens,
It is. The imaging lens according to any one of claims 1 to 9, wherein at least one negative lens in the first group satisfies the following conditional expressions (13) and (14).
(0.6425- [theta] gF) / [nu] d> 0.0015 (13)
νd <50 (14)
However,
θgF: partial dispersion ratio of lens material,
θgF = (Ng−NF) / (NF−NC)
Ng: refractive index for g-line,
NF: refractive index for F-line,
NC: Refractive index for C-line,
νd: Abbe number related to the d-line of the lens material,
It is. The imaging lens according to claim 8, wherein the following conditional expression (15) is satisfied:
-0.6 <φ3 / φ <0.6 (15)
However,
φ3: Power of the third group,
φ: Power of the entire system,
It is.   The imaging lens according to claim 1, wherein only one negative lens is included in the second group.   An imaging lens according to claim 1, and an imaging device that converts an optical image formed on the imaging surface into an electrical signal, and a subject on the imaging surface of the imaging device. An imaging optical apparatus, wherein the imaging lens is provided so that an optical image of the above is formed.   14. A digital apparatus comprising the imaging optical device according to claim 13 to which at least one function of still image shooting and moving image shooting of a subject is added.

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