JP2019090948A - Image capturing lens, image capturing optical device, and digital equipment - Google Patents

Abstract

To provide an image capturing lens which features a bright F-number and a lighter focusing group, and yet is well corrected for aberrations from an infinity end to a proximity end and capable of providing uniform image quality over an entire image, and to provide an image capturing optical system and digital equipment having the same.SOLUTION: An image capturing lens LN comprises a first group Gr1 having positive power, a second group Gr2 having positive power, and a third group Gr3 having negative power in order from the object side. When shifting focus from infinity to an object in the proximity, the first group Gr1 is stationary, the distance between the first group Gr1 and the second group Gr2 decreases, and the distance between the second group Gr2 and the third group Gr3 increases. The second group Gr2 comprises a negative lens L21 and a positive lens L22 arranged in order from the object side. Dividing the first group Gr1 into two groups by a greatest air gap within the first group Gr1, and defining an object-side group as a front group Gr1a and an image-side group a rear group Gr1b, focal lengths of the front group Gr1a, rear group Gr1b, second group Gr2, and third group Gr3, an Abbe number of the second group Gr2 and the like are each set appropriately.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging lens, an imaging optical device, and a digital apparatus, and, for example, a compact, wide-angle, large-aperture imaging lens suitable for a lens-interchangeable digital camera for capturing an image of a subject by an imaging device, and the imaging lens and The present invention relates to an imaging optical device that outputs an image of a subject captured by an imaging device as an electrical signal, and 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 lens interchangeable cameras. In digital cameras, it is possible for the user to view an image at the same magnification on a monitor, so improvement in MTF (Modulation Transfer Function) performance is increasingly required from the infinite end to the near end. ing.

  In addition, among mirrorless lens interchangeable cameras in which a flip-up mirror is removed from a single-lens reflex camera, there are also cameras that can not use the phase difference AF (autofocus), which has been the mainstream in conventional single-lens reflex cameras. In such a camera, so-called contrast AF is used in which focusing is performed by scanning a focus group and searching for a place where the contrast is maximum.

  In the case of phase difference AF, since the amount of movement of the focus group necessary for focusing can be calculated using information from the AF sensor, the focus group can be moved according to the amount. On the other hand, in the case of contrast AF, the information obtained from the AF sensor is only the contrast value at that moment, and by moving the focus group and reading the change in contrast every time, searching for a place where the contrast is maximum The focus operation will be performed. Therefore, when the amount of movement of the focus group up to the in-focus state is compared between the contrast AF and the phase difference AF, the former case is overwhelmingly large.

  For example, in order to cope with contrast AF in a large aperture imaging lens having an F number of 2 or less, weight reduction of the focus group is a major point in order to speed up AF. Therefore, it is necessary to balance the weight reduction of the focus group for speeding up the AF and the improvement of the MTF performance (aberration performance) from the infinite end to the near end. As a large aperture imaging lens, for example, those proposed in Patent Document 1 can be mentioned. Further, as an imaging lens configured to focus in the positive second group, one proposed in Patent Document 2 can be mentioned.

JP, 2016-126279, A JP, 2013-186458, A

  In the large-aperture imaging lens proposed in Patent Document 1, the number of lenses in the focus group increases in order to ensure the performance at the time of focusing, and the weight reduction of the focus group is insufficient. Further, in the imaging lens proposed in Patent Document 2, there is a problem that the aberration fluctuation generated in the second group at the time of focusing is large.

  The present invention has been made in view of such a situation, and an object thereof is to correct aberration well from an infinite end to a near end while achieving both a bright F number and weight reduction of a focus group. It is an object of the present invention to provide an imaging lens capable of obtaining uniform image quality over the entire image, and an imaging optical apparatus and digital apparatus equipped with the imaging lens.

In order to achieve the above object, the imaging lens of the first invention comprises, in order from the object side, a first group of positive power, a second group of positive power, and a third group of negative power. In focusing from a distant object to a close object, the first group is fixed in position, the distance between the first group and the second group is reduced, and the distance between the second group and the third group is increased. A lens,
In the second group, a negative lens and a positive lens are disposed in order from the object side,
When the first group is divided into two groups with the largest air gap in the first group as a boundary, assuming that the object side group is a front group and the image side group is a rear group, the following conditional expressions It is characterized by satisfying (1) to (6).
1.3 <−f1a / f <3.5 (1)
0.9 <f1b / f <1.5 (2)
1.2 <f2 / f <1.8 (3)
1.2 <| f3 / f2 | <4.0 (4)
−1.8 <(ra + rb) / (ra−rb) <− 0.05 (5)
dd_2p-νd_2n> 25 (6)
However,
f1a: focal length of front group,
f1b: focal length of rear group,
f: focal length of the whole system,
f2: focal length of the second group,
f3: focal length of the third group,
ra: radius of curvature of the surface closest to the image side in the front group,
rb: radius of curvature of the surface closest to the object side in the rear group,
d d _2 p: Abbe number of the positive lens disposed second from the object side in the second group
d d _2 n: Abbe number of the negative lens placed first from the object side in the second group
It is.

The imaging lens of the second invention is characterized in that, in the first invention, the positive lens with the strongest power in the second group satisfies the following conditional expressions (7) and (8).
0.45 <f2p / f2 <1.2 (7)
θg, F-(-0.0018 d d + 0.6 484)> 0.009 (8)
However,
f2p: focal length of the most powerful positive lens in the second group,
f2: focal length of the second group,
θg, F: Partial dispersion ratio of lens material,
θg, F = (Ng-NF) / (NF-NC)
Ng: refractive index with respect to g-line,
NF: refractive index with respect to F ray,
NC: refractive index with respect to C ray,
d d: Abbe number related to d-line of lens material,
It is.

The imaging lens of the third invention is characterized in that, in the first or second invention, at least two positive lenses are included in the second group, and the following conditional expression (9) is satisfied. I assume.
2.0 <f2_ip / f2_op <4.5 (9)
However,
f2_op: focal length of the positive lens closest to the object in the second group,
f2_ip: focal length of the positive lens closest to the image side in the second group,
It is.

  The imaging lens of the fourth invention is characterized in that in the first to third inventions, the lens closest to the image in the second group is an aspheric lens.

  The imaging lens of the fifth invention is characterized in that in the first to fourth inventions, the surface closest to the object side in the third group has a shape in which the concave surface is directed to the object side. .

  In the imaging lens according to a sixth aspect of the invention, in the focusing according to any one of the first to fifth aspects, the second group moves toward the object side and the third group is in the image plane during focusing from infinity to a close object. It is characterized by moving to the side.

The imaging lens of the seventh invention is characterized in that, in the sixth invention, the following conditional expression (10) is satisfied.
0.2 <| d_2Gr / d_3Gr | <1.2 (10)
However,
d_2Gr: Movement amount of second group in focusing from infinity to any object distance,
d_3Gr: moving amount of the third group in focusing from infinity to any object distance,
It is.

  An imaging lens according to an eighth invention is characterized in that, in any one of the first to seventh inventions, a diaphragm is disposed between the first group and the second group.

The imaging lens of the ninth invention is characterized in that, in any one of the first to eighth inventions, the following conditional expression (11) is satisfied.
0.2 <f / TL <0.45 (11)
However,
f: focal length of the whole system,
TL: distance from the surface closest to the object side of the imaging lens to the image plane,
It is.

  An imaging optical apparatus according to a tenth aspect of the invention includes the imaging lens according to any one of the first to ninth aspects of the invention, and an imaging element that converts an optical image formed on an imaging surface into an electrical signal. The imaging lens is provided such that an optical image of a subject is formed on an imaging surface of the imaging device.

  An eleventh aspect of the present invention is characterized in that at least one of still image shooting and moving image shooting of a subject is added by providing the imaging optical apparatus according to the tenth aspect of the present invention.

  According to the present invention, while achieving both bright F-number and weight reduction of the focus group, the aberration is corrected well from the infinite end to the near end, and imaging capable of obtaining uniform image quality over the entire image A lens and an imaging optical device can be realized. By using the imaging lens or the imaging optical device for a digital device (for example, a digital camera), it is possible to compactly add a high-performance image input function to the digital device.

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. 5 is a longitudinal aberration diagram of Example 1; FIG. 7 is a longitudinal aberration diagram of Example 2; FIG. 7 is a longitudinal aberration diagram of Example 3; FIG. 7 shows longitudinal aberration of Example 4; FIG. 16 shows longitudinal aberration of Example 5; FIG. 7 shows lateral aberration at the first focus position in Example 1. FIG. 7 shows lateral aberration at the second focus position in Example 1. FIG. 10 shows lateral aberration at the first focus position in Example 2. FIG. 7 shows lateral aberration at the second focus position in Example 2. FIG. 20 shows lateral aberration at the first focus position in Example 3. FIG. 20 shows lateral aberration at the second focus position in Example 3. FIG. 20 shows lateral aberration at the first focus position in Example 4. FIG. 20 shows lateral aberration at the second focus position in Example 4. FIG. 20 shows lateral aberration at the first focus position in Example 5. FIG. 20 shows lateral aberration at the second focus position in Example 5. FIG. 2 is a schematic view showing an example of a schematic configuration of a digital device equipped with an imaging optical device.

  Hereinafter, an imaging lens, an imaging optical device, and a digital apparatus according to an embodiment of the present invention will be described. The imaging lens according to the embodiment of the present invention includes, in order from the object side, a first group of positive power, a second group of positive power, and a third group of negative power (power: reciprocal of focal length) In focusing from an infinite distance to a close object, the first group is fixed in position, and the distance between the first group and the second group is reduced, and the second group and the third group are reduced. The distance to the group increases. In the second group, a negative lens and a positive lens are disposed in order from the object side.

When the first group is divided into two groups with the largest air gap in the first group as a boundary, the object side group is a front group, and the image side group is a rear group. The lens is characterized by satisfying the following conditional expressions (1) to (6).
1.3 <−f1a / f <3.5 (1)
0.9 <f1b / f <1.5 (2)
1.2 <f2 / f <1.8 (3)
1.2 <| f3 / f2 | <4.0 (4)
−1.8 <(ra + rb) / (ra−rb) <− 0.05 (5)
dd_2p-νd_2n> 25 (6)
However,
f1a: focal length of front group,
f1b: focal length of rear group,
f: focal length of the whole system,
f2: focal length of the second group,
f3: focal length of the third group,
ra: radius of curvature of the surface closest to the image side in the front group,
rb: radius of curvature of the surface closest to the object side in the rear group,
d d _2 p: Abbe number of the positive lens disposed second from the object side in the second group
d d _2 n: Abbe number of the negative lens placed first from the object side in the second group
It is.

  Three groups of positive and negative are arranged in order from the object side, and in focusing from an infinite distance to a close object, the position of the first group is fixed, the distance between the first group and the second group is reduced, and the second and third groups are arranged. If a configuration in which the distance from the group is enlarged is adopted, an effect of suppressing aberration fluctuation at the time of focusing can be obtained. Further, by disposing the negative lens and the positive lens in order from the object side in the second group, it is possible to make an advantageous configuration for coma aberration correction of off-axis light.

  If the lower limit of conditional expression (1) is exceeded, the negative power of the front group does not become too strong, and expansion of the total length is prevented, and aberrations such as coma aberration etc. are gradually refracted Can be reduced. If the upper limit of conditional expression (1) is exceeded, the negative power of the front group is not too weak, and the back focal position of the first group can be made closer to the second group. The amount of driving of the lens can be suppressed, and the spherical aberration variation associated with focusing can be suppressed.

  If the lower limit of conditional expression (2) is exceeded, the positive power of the rear group does not become too strong, and the back focal position of the first group can be brought closer to the second group. The amount of driving of the lens can be suppressed, and the spherical aberration variation associated with focusing can be suppressed. Below the upper limit of conditional expression (2), the positive power of the rear group does not become too weak, and by appropriately sharing the positive power with the second group, field curvature, spherical aberration, etc. associated with focusing Fluctuations can be suppressed.

  If the lower limit of conditional expression (3) is exceeded, the power of the second group will not be too strong, and spherical aberration fluctuation due to movement of the second group at the time of focusing can be suppressed. Below the upper limit of the conditional expression (3), it is possible to prevent an increase in the amount of movement of the second group and to suppress a change in curvature of field due to the movement of the second group. Moreover, the increase in the effective diameter of the second group can be suppressed.

  If the lower limit of conditional expression (4) is exceeded, it is possible to prevent an increase in the amount of movement of the focus group, and to suppress the curvature of field due to the focus. Below the upper limit of conditional expression (4), the positive power of the rear group does not become too weak, and the positive power can be shared with the second group, so variations in field curvature, spherical aberration, etc. associated with focusing It can be suppressed.

  Conditional expression (5) defines the curvatures of the most image-side surface of the front group and the most object-side surface of the rear group. If the lower limit of conditional expression (5) is exceeded, the diverging action of the surface closest to the object side in the rear group is suppressed, and the occurrence of spherical aberration can be reduced. Below the upper limit of the conditional expression (5), the diverging action on the surface closest to the image side in the front group is not excessive, and the occurrence of coma aberration in off-axis light flux can be reduced.

  When conditional expression (6) is satisfied, the generation of axial chromatic aberration due to the second group is suppressed, so that the generation of chromatic aberration can be suppressed over the entire focus region.

  According to the above-described characteristic configuration, while achieving both a bright F-number and a reduction in the weight of the focus group, the aberration is corrected well from the infinite end to the close end, and uniform image quality can be obtained in the entire image. An imaging lens and an imaging optical apparatus provided with the same can be realized. 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, making the digital device compact and low. It can contribute to costing, higher performance, higher functionality, etc. For example, since the imaging lens having the above-described characteristic configuration is suitable as an interchangeable lens for digital cameras and video cameras, a lightweight, compact, high-performance interchangeable lens that is easy to carry can be realized. The conditions for achieving such effects in a well-balanced manner, as well as achieving higher optical performance, lighter weight, miniaturization, and the like will be described below.

It is desirable to satisfy the following conditional expression (2a).
0.9 <f1b / f <1.4 (2a)
The conditional expression (2a) defines a further preferable condition range based on the viewpoint and the like among the conditional ranges defined by the conditional expression (2). Therefore, preferably, the above effect can be further enhanced by satisfying the conditional expression (2a).

It is desirable to satisfy the following conditional expression (4a).
1.2 <| f3 / f2 | <3.5 (4a)
The conditional expression (4a) defines a further preferable condition range based on the viewpoint and the like among the condition ranges defined by the conditional expression (4). Therefore, preferably, the above effect can be further enhanced by satisfying the conditional expression (4a).

It is desirable that the most powerful positive lens in the second group satisfies the following conditional expressions (7) and (8).
0.45 <f2p / f2 <1.2 (7)
θg, F-(-0.0018 d d + 0.6 484)> 0.009 (8)
However,
f2p: focal length of the most powerful positive lens in the second group,
f2: focal length of the second group,
θg, F: Partial dispersion ratio of lens material,
θg, F = (Ng-NF) / (NF-NC)
Ng: refractive index with respect to g-line,
NF: refractive index with respect to F ray,
NC: refractive index with respect to C ray,
d d: Abbe number related to d-line of lens material,
It is.

  Conditional expression (7) defines the power of the positive lens having the strongest power in the second group. If the lower limit of conditional expression (7) is exceeded, the power of the positive lens will not be too strong, and fluctuations in field curvature when the second lens unit is moved at the time of focusing can be suppressed. When the value falls below the upper limit of the conditional expression (7), the power of the positive lens does not become too weak, and it is possible to suppress comatic aberration in off-axis light flux.

  Conditional expression (8) defines anomalous dispersion of the positive lens having the strongest optical power in the second group. By satisfying conditional expression (8), it is possible to effectively reduce axial chromatic aberration fluctuation associated with focusing. Furthermore, by satisfying the conditional expression (8), the positive lens with the strongest power in the second group can exhibit the chromatic aberration correction effect to the maximum.

It is further desirable that the most powerful positive lens in the second group satisfies the following conditional expression (7a).
0.45 <f2p / f2 <1.0 (7a)
The conditional expression (7a) defines a further preferable condition range based on the viewpoint and the like among the condition ranges defined by the conditional expression (7). Therefore, preferably, the above effect can be further enhanced by satisfying the conditional expression (7a).

It is desirable that at least two positive lenses be provided in the second group, and the following conditional expression (9) be satisfied.
2.0 <f2_ip / f2_op <4.5 (9)
However,
f2_op: focal length of the positive lens closest to the object in the second group,
f2_ip: focal length of the positive lens closest to the image side in the second group,
It is.

  Conditional expression (9) defines the power ratio of the plurality of positive lenses disposed in the second group. In the second group, a positive lens on the object side performs focusing and a positive lens on the image mainly performs field curvature correction, thereby reducing fluctuations in spherical aberration, field curvature, etc. involved in focusing. be able to. If the lower limit of conditional expression (9) is exceeded, the positive power of the image side lens will not be too strong, and the front principal point position of the second group can be made closer to the first group. The amount is reduced, and the spherical aberration fluctuation at the time of focusing can be suppressed. If the upper limit of conditional expression (9) is exceeded, the positive power of the image side lens will not be too weak, and field curvature of the off-axis light flux can be effectively reduced. Furthermore, when the second group is configured by three lenses of negative, positive and positive, it is the most effective configuration in suppressing the aberration fluctuation at the time of focusing while reducing the weight of the second group.

  The lens closest to the image in the second group is preferably an aspheric lens. By having an aspheric surface in the lens closest to the image side in the second group, it is possible to effectively suppress the field curvature aberration. It is preferable that the aspheric shape of the lens on the most image side in the second group is a meniscus shape in which the positive power gradually decreases from the optical axis toward the periphery. Adopting such an aspheric shape makes it possible to effectively correct curvature of field while suppressing coma aberration generated by off-axis light flux. It is further desirable that the lens surface closest to the image in the second group be an aspheric surface, and the above effect can be further enhanced.

  It is desirable that the surface closest to the object side in the third group have a shape in which the concave surface is directed to the object side. By making the surface closest to the object side in the third group to be the object side and having a concave surface, it is possible to reduce the change in incident angle to the surface involved with focusing, thereby suppressing coma aberration variation during focusing. Field curvature can also be corrected effectively.

  In focusing from an infinite distance to a close object, it is preferable that the second group move to the object side and the third group move to the image plane side. When the second unit is driven in the object direction at the time of focusing and the third unit is driven in the image direction, various aberrations such as spherical aberration and field curvature generated in the second and third units are canceled out. It becomes possible. Therefore, good optical performance can be obtained from the infinite end to the near end.

Regarding the second and third groups, it is desirable to satisfy the following conditional expression (10).
0.2 <| d_2Gr / d_3Gr | <1.2 (10)
However,
d_2Gr: Movement amount of second group in focusing from infinity to any object distance,
d_3Gr: moving amount of the third group in focusing from infinity to any object distance,
It is.

  Conditional expression (10) defines the ratio of the focus movement amounts of the second and third groups. When the value goes below the lower limit of the conditional expression (10), it is possible to prevent an increase in the power of the second group and to suppress spherical aberration fluctuation at the time of focusing. Below the upper limit of the conditional expression (10), the movement amount of the second group is controlled so as not to be too large relative to the movement amount of the third group, and the spherical surface by simultaneous driving of the second and third groups The amount of fluctuation such as aberration and curvature of field can be reduced.

  It is desirable that a diaphragm be disposed between the first group and the second group. When the stop is disposed between the first and second groups, an increase in the effective diameter of the second group is suppressed, which enables weight reduction of the second group, leading to an increase in focus speed. In addition, by arranging groups having positive power to face each other across the stop, it is possible to make an advantageous configuration for reducing coma.

It is desirable to satisfy the following conditional expression (11).
0.2 <f / TL <0.45 (11)
However,
f: focal length of the whole system,
TL: distance from the surface closest to the object side of the imaging lens to the image plane,
It is.

  Conditional expression (11) defines the ratio of the total length of the imaging lens to the focal length. If the lower limit of conditional expression (11) is exceeded, the diameter of the off-axis ray in the first group can be suppressed, and the occurrence of coma can be suppressed. If the upper limit of the conditional expression (11) is exceeded, the diameter of the off-axis ray in the first group will not be too small, so that correction of chromatic aberration and the like will be facilitated.

  The imaging lens described above is suitable for use as an imaging lens for a digital device with an image input function (for example, a lens-interchangeable digital camera), and by combining this with an imaging element or the like, the image of a subject is optically The imaging optical apparatus can be configured to capture the signal and output it as an electrical signal. The imaging optical device is an optical device that is a main component of a camera used for still image shooting and moving image shooting of an object, and for example, an imaging lens that forms an optical image of an object in order from the object (that is, object). And an imaging element (image sensor) for converting an optical image formed by the imaging lens into an electrical signal. Then, the imaging lens having the above-described characteristic configuration is disposed so that the optical image of the subject is formed on the light receiving surface (that is, the imaging surface) of the imaging element, thereby achieving high performance with small size and low cost. It is possible to realize an imaging optical device and a digital apparatus equipped with the imaging optical device.

  Examples of digital devices with an image input function include cameras such as digital cameras, video cameras, surveillance cameras, security cameras, on-vehicle cameras, and cameras for videophones. In addition, personal computers, portable digital devices (for example, mobile phones, smart phones (high-performance mobile phones), tablet terminals, mobile computers, etc.), peripheral devices of these (scanners, printers, mice, etc.) and other digital devices (drives) There is a camera, a camera, a defense device, etc. with a built-in or external camera function. As understood 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, it is possible to configure a digital device with an image input function such as a camera-equipped mobile phone.

  FIG. 21 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 apparatus DU shown in FIG. 21 includes, in order from the object (ie, object) side, an imaging lens LN (AX: optical axis) that forms an optical image (image plane) IM of the object; And an imaging element SR configured to convert an optical image IM formed on the light receiving surface (imaging surface) SS by the imaging lens LN into an electrical signal, and a plane parallel plate (for example, the imaging element SR). Cover glass; corresponding to an optical low pass filter, an optical filter such as an infrared cut filter, etc., which are disposed as necessary.

  When the digital device DU with an image input function is configured by the imaging optical device LU, the imaging optical device LU is usually disposed inside the body, but a form according to the necessity is adopted when realizing the camera function. It is possible. For example, the unitized imaging optical apparatus LU may be configured to be rotatable with respect to the main body of the digital apparatus DU, and the unitized imaging optical apparatus LU is used as an interchangeable lens with an image sensor as a digital apparatus DU (that is, a lens It may be configured to be removable from the main body of the interchangeable camera).

  The imaging lens LN is, for example, a wide-angle single-focus lens composed of at least three groups, and at least the second group in a state in which the position of the first group is fixed (that is, in a state where the position is fixed with respect to the image plane IM). By moving along the optical axis AX, focusing to a near distance object is performed, and an optical image IM is formed on the light receiving surface SS of the imaging element SR. As the imaging element SR, for example, a solid-state imaging element such as a CCD (Charge Coupled Device) type image sensor having a plurality of pixels or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor is used. The imaging lens LN is provided such 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. Therefore, the optical image IM formed by the imaging lens LN is an imaging element It is converted into an electrical 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 imaging element SR is subjected to predetermined digital image processing, image compression processing, and the like by the signal processing unit 1 as necessary, and is recorded as digital video signals in the memory 3 (semiconductor memory, optical disk, etc.) In some cases, the signal is converted to an infrared signal or the like through a cable and transmitted to another device (for example, a communication function of a mobile phone). The control unit 2 comprises a microcomputer and controls functions such as a photographing function (still image photographing function, moving image photographing function, etc.) and an image reproducing function; focusing control of a lens moving mechanism for focusing, camera shake correction, etc. Do. For example, the control unit 2 controls the imaging optical apparatus LU so as to perform at least one of still image shooting and moving image shooting of a subject. The display unit 5 is a portion including 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 portion including operation members such as an operation button (for example, a release button) and an operation dial (for example, a photographing 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 respectively corresponding to the imaging lenses LN constituting the first to fifth embodiments, and show the lens arrangement in an infinite distance object distance state in an optical cross section. A plane-parallel plate PT is disposed between the imaging lens LN and the image plane IM, and the plane-parallel plate PT has a total optical thickness of a cover glass of the image sensor SR and a low pass filter for preventing moire. Is a glass plate equivalent to

  In the first to fifth embodiments, in order from the object side, positive and negative three groups consisting of a first lens group Gr1 of positive power, a second lens group Gr2 of positive power, and a third lens group Gr3 of negative power. It is configured as a compact, wide-angle, large-aperture single-focus interchangeable lens. In FIGS. 1 to 5, L1 # (# = 1, 2,..., 8) is the #th lens from the object side in the first group Gr1, and L2 # (# = 1, 2, 3) is the second lens In the group Gr2, it is the #th lens from the object side, and L31 is a single lens constituting the third group Gr3.

  In the first and fourth embodiments, in focusing from the first focus position POS1 (infinite end: infinite object distance state) to the second focus position POS2 (close end: close object distance condition), the first group The positions of Gr1 and the third lens unit Gr3 are fixed relative to the image plane IM, and the distance between the first lens unit Gr2 and the second lens unit Gr2 is narrowed, and the distance between the second lens unit Gr2 and the third lens unit Gr3 is increased. The second group Gr2 which is a focus group moves to the object side along the optical axis AX. In the second, third, and fifth embodiments, in focusing from the first focus position POS1 to the second focus position POS2, the first group Gr1 is fixed in position with respect to the image plane IM, and the first group Gr1 And the second group Gr2 and the third group Gr3 which are focus groups extend in the reverse direction along the optical axis AX so that the distance between the second group Gr2 and the second group Gr2 narrows and the distance between the second group Gr2 and the third group Gr3 widens. Move to Arrows m1, m2 and m3 respectively indicate movement trajectories of the first group Gr1, the second group Gr2 and the third group Gr3 and are disposed between the first group Gr1 and the second group Gr2. The stop (aperture stop) ST and the plane-parallel plate PT disposed on the image plane IM side of the imaging lens LN are fixed in focus position together with the first group Gr1.

  In the second, third, and fifth embodiments, the floating focus method is adopted as described above, and the second lens unit Gr2 moves to the object side in focusing from the infinite end to the close end. On the other hand, the third lens unit Gr3 moves to the image side. When the focus movement directions of the second lens unit Gr2 and the third lens unit Gr3 are reversed in this way and the distance between the second lens unit Gr2 and the third lens unit Gr3 is increased, fluctuations in aberrations such as curvature of field at the time of focusing Can be advantageously canceled out in the second group Gr2 and the third group Gr3. Therefore, the aberration deterioration at the time of focusing can be corrected more effectively, and the image quality at the closest end POS2 can be further improved.

  When the first group Gr1 is divided into two groups with the largest air gap in the first group Gr1 as a boundary, the group on the object side is the front group Gr1a, and the group on the image side is the rear group Gr1b. In the first to fifth embodiments, the front group Gr1a has negative power and the rear group Gr1b has positive power, and the power arrangement of the front group Gr1a and the rear group Gr1b is appropriately set. By setting, good aberration correction is possible.

  The imaging lens LN (FIG. 1) according to the first embodiment has a positive / negative three-group configuration, and each group is configured in the following order from the object side. The first group Gr1 is composed of a front group Gr1a and a rear group Gr1b, the front group Gr1a is composed of a negative meniscus lens L11 concave on the image side, and the rear group Gr1b is a negative meniscus lens concave on the image side A cemented lens including L12 and a biconvex positive lens L13, a cemented lens including a biconcave negative lens L14 and a biconvex positive lens L15, a biconvex positive lens L16, a biconvex positive lens L17 and a biconcave lens And a cemented lens composed of the negative lens L18. The second lens unit Gr2 is composed of a negative meniscus lens L21 concave to the object side, a biconvex positive lens L22, and a positive meniscus lens L23 (both surfaces are aspheric) convex to the image side. The third lens unit Gr3 is composed of a biconcave negative lens L31.

  The imaging lens LN (FIG. 2) of the second embodiment has a positive / negative three-group configuration, and each group is configured in the following order from the object side. The first lens group Gr1 is composed of a front lens group Gr1a and a rear lens group Gr1b, the front lens group Gr1a is composed of a negative meniscus lens L11 concave on the image side, and the rear lens group Gr1b is a biconcave negative lens L12 and an object A cemented lens consisting of a positive meniscus lens L13 convex to the side, a cemented lens consisting of a biconcave negative lens L14 and a biconvex positive lens L15, a biconvex positive lens L16, a biconvex positive lens L17 and a biconcave And a cemented lens composed of the negative lens L18. The second lens unit Gr2 is composed of a negative meniscus lens L21 concave to the object side, a biconvex positive lens L22, and a positive meniscus lens L23 (both surfaces are aspheric) convex to the image side. The third lens unit Gr3 is composed of a biconcave negative lens L31.

  The imaging lens LN (FIG. 3) of the third embodiment has a positive / negative three-group configuration, and each group is configured in the following order from the object side. The first group Gr1 comprises a front group Gr1a and a rear group Gr1b. The front group Gr1a is a negative meniscus lens L11 concave on the image side, a positive meniscus lens L12 convex on the object side, and a negative meniscus concave on the image side The rear lens unit Gr1b includes a cemented lens including a biconcave negative lens L14 and a biconvex positive lens L15, and a biconvex positive lens L16 (both surfaces are aspheric). And a cemented lens composed of a biconvex positive lens L17 and a biconcave negative lens L18. The second lens unit Gr2 is composed of a negative meniscus lens L21 concave on the object side (aspheric both surfaces), a biconvex positive lens L22, and a positive meniscus lens L23 convex on the image side (aspheric both surfaces). It is done. The third lens unit Gr3 is composed of a plano-concave negative lens L31 concave on the object side.

  The imaging lens LN (FIG. 4) of the fourth embodiment has a positive / negative three-group configuration, and each group is configured in the following order from the object side. The first group Gr1 is composed of a front group Gr1a and a rear group Gr1b. The front group Gr1a is composed of negative meniscus lenses L11 and L12 concave on the image side of the two sheets, and the rear group Gr1b is biconcave. A cemented lens including a negative lens L13 and a biconvex positive lens L14, and a biconvex positive lens L15. The second lens unit Gr2 is composed of a negative meniscus lens L21 concave to the object side, a biconvex positive lens L22, and a positive meniscus lens L23 (both surfaces are aspheric) convex to the image side. The third lens unit Gr3 is composed of a negative meniscus lens L31 concave on the object side.

  The imaging lens LN (FIG. 5) according to the fifth embodiment has a positive / negative three-group configuration, and each group is configured in the following order from the object side. The first group Gr1 is composed of a front group Gr1a and a rear group Gr1b. The front group Gr1a is composed of a negative meniscus lens L11 concave on the image side, and the rear group Gr1b is a biconvex positive lens L12 and both lenses. A cemented lens consisting of a concave negative lens L13, a cemented lens consisting of a biconcave negative lens L14 and a biconvex positive lens L15, a biconvex positive lens L16, and a negative meniscus lens L17 concave on the image side And an aspheric surface). The second lens unit Gr2 is composed of a negative meniscus lens L21 concave to the object side, a biconvex positive lens L22, and a positive meniscus lens L23 (both surfaces are aspheric) convex to the image side. The third lens unit Gr3 is composed of a negative meniscus lens L31 (both surfaces are aspheric) that is concave toward the object side.

  Hereinafter, the configuration and the like of the imaging lens according to the present invention will be described more specifically with reference to construction data and the like of the embodiments. Examples 1 to 5 (EX 1 to 5) listed here are numerical value examples respectively corresponding to the first to fifth embodiments described above, and are lens configuration diagrams representing the first to fifth embodiments. (FIGS. 1-5) has shown the optical structure of corresponding Examples 1-5, respectively.

  In the construction data of each example, as surface data, surface number i (OB: object surface, ST: aperture, IM: image surface), radius of curvature ri (mm) in paraxial direction, axial top surface interval sequentially from the left column The refractive index nd with respect to di (mm) and d line (wavelength: 587.56 nm), the Abbe number d d with respect to d line, and the effective radius Ri (mm) are shown.

The surface with * attached to the surface number i is aspheric, and the surface shape is defined by the following expression (AS) using the local orthogonal coordinate system (x, y, z) with the surface vertex as the origin Ru. Aspheric surface coefficients etc. are shown as aspheric surface data. In the aspheric surface data of each example, the coefficient of a term not indicated is 0, and E−n = × 10 ⁻ⁿ for all data.
z = (c · h ² ) / [1 + {{1-(1 + K) · c ² · h ² }] + ((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: amount of sag in the direction of the optical axis AX at the position of height h (surface vertex reference),
c: Curvature at face vertex (reciprocal of radius of curvature ri),
K: Conical constant,
Aj: j-th order aspheric coefficient,
It is.

  As various data, focal length f (mm) of the whole system, F number (FNO), total angle of view 2 ω (°), total lens length TL (distance from the surface on the most object side of imaging lens LN to image plane IM (air No conversion), mm), back focus BF (distance from the image side surface of the plane parallel plate PT to the image plane IM, mm) is shown. Furthermore, as variable parameters that change due to focusing, the aperture diameter (effective radius) Ri and the variable axial upper surface distance di, the first focus position POS1 (infinity object distance state), the second focus position POS2 (close object distance state) It shows about each. The amount of movement d_2Gr of the second lens unit Gr2 and the amount of movement d_3Gr of the third lens unit Gr3 when focusing is moved from the first focus position POS1 to the second focus position POS2 are shown in Table 1 Table 2 shows the related data of the conditional expression.

  FIGS. 6 to 10 are longitudinal aberration diagrams respectively corresponding to Examples 1 to 5 (EX1 to EX5), wherein (A) to (C) show the first focus position POS1, (D) to (F). These show the various aberrations in 2nd focus position POS2, respectively. Further, in FIGS. 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 indicated with the solid line (wavelength 587.56 nm), and the g-line indicated with the broken line (wavelength 435.84 nm). The amount of spherical aberration is represented by the amount of deviation (mm) in the direction of the optical axis AX from the paraxial image plane, and the vertical axis is a value obtained by normalizing the incident height to the pupil by its maximum height (that is, the relative pupil Represents the height). In the astigmatism diagram, the broken line T represents the tangential image plane with respect to the d-line, and the solid line S represents the sagittal image plane with respect to the d-line by the amount of deviation (mm) in the optical axis AX direction from the paraxial image plane, The vertical axis represents the image height (IMG HT, mm). In the distortion aberration diagram, the horizontal axis represents distortion (%) to the d-line, and the vertical axis represents image height (IMG HT, mm). The maximum value of the image height IMG HT corresponds to the maximum image height on the image plane IM.

  FIGS. 11, 13, 15, 17, and 19 are lateral aberration diagrams respectively corresponding to Examples 1 to 5 (EX1 to EX5) at the first focus position POS1, and FIGS. FIGS. 16, 18, and 20 are lateral aberration diagrams respectively corresponding to Examples 1 to 5 (EX1 to EX5) at the second focus position POS2. In each of FIGS. 11 to 20, the left column shows the transverse aberration (mm) with tangential light flux, and the right column shows the transverse aberration (mm) with sagittal light flux. In addition, transverse aberration at the image height ratio (half angle of view ω °) represented by RELATIVE FIELD HEIGHT is indicated by a C-line (wavelength 656.28 nm) indicated by an alternate long and short dash line, d-line indicated by a solid line (wavelength 587.56 nm) , G-line (wavelength 435.84 nm) indicated by a broken line. The image height ratio is a relative image height obtained by normalizing the image height IMG HT with the maximum image height.

Example 1
Unit: mm
Surface data
i ri di nd d d Ri
0 (OB) d d0
1 3.6505 0.102 1.69895 30.05 0.974
2 0.8575 0.526 0.741
3 20.9253 0.092 1.51680 64.20 0.735
4 2.5328 0.219 1.92286 20.88 0.726
5-11.9373 0.295 0.716
6-1.7717 0.119 1.62004 36.30 0.668
7 1.9685 0.181 1.61997 63.88 0.671
8-6.8.010 0.027 0.672
9 3.1070 0.281 1.88100 40.14 0.665
10-2.2357 0.005 0.651
11 2.0457 0.236 1.77250 49.62 0.537
12 -1.6840 0.060 1.71736 29.50 0.514
13 1.9949 0.169 0.459
14 (ST) d d14 R14
15-0.8083 0.162 1.80518 25.46 0.366
16-1.3785 0.044 0.423
17 1.9910 0.278 1.59282 68.62 0.535
18-1.3431 0.172 0.553
19 * -3.2245 0.100 1.83220 40.10 0.569
20 * -1.7591 d20 0.583
21 -2.3650 0.093 1.80518 25.46 0.604
22 8.6281 0.603 0.640
23 0.06 0.069 1.51480 64.14 1.200
24 BF 1.200
25 (IM) ∞

Aspheric data
i 19 20
K 0 0
A4-2.604E-01-5.854E-04
A6 1.934E-01 3.059E-01
A8 0.000 E + 00 0.000 E + 00
A10 0.000 E + 00 0.000 E + 00
A12 0.000 E + 00 0.000 E + 00

Various data
f 1.13
FNO 1.85
2ω 83.0
TL 4.414
BF 0.0462
Variable parameter Object distance d0 R14 d14 d20
∞ (POS1) 0.425 0.395 0.139
7.14 mm (POS2) 0.420 0.277 0.257
Group movement amount (POS1 → POS2)
Gr2
-0.118

Example 2
Unit: mm
Surface data
i ri di nd d d Ri
0 (OB) d d0
1 5.2537 0.102 1.6644 35.91 0.975
2 0.9322 0.551 0.758
3-30. 4018 0.092 1.62004 36. 30 0.737
4 1.9408 0.224 1.92286 20.88 0.719
5 24.9372 0.235 0.707
6 -1.8836 0.092 1.69895 30.05 0.686
7 2.6962 0.265 1.83481 42.72 0.699
8-3.2039 0.009 0.701
9 2.1418 0.231 1.88300 40.76 0.670
10 -7.1415 0.009 0.648
11 1.7434 0.281 1.83481 42.72 0.566
12 -1.8840 0.060 1.69895 30.05 0.526
13 1.4348 0.191 0.444
14 (ST) d d14 R14
15 -0.7488 0.055 1.75520 27.53 0.361
16-2.4434 0.024 0.375
17 2.3343 0.269 1.59282 68.62 0.460
18-0.9873 0.109 0.491
19 * -5.8696 0.135 1.82080 42.71 0.524
20 * -1.9402 d20 0.560
21-4.0712 0.092 1.72047 34.71 0.693
22 20.1119 d22 0.676
23 0.06 0.069 1.51680 64.14 1.200
24 BF 1.200
25 (IM) ∞

Aspheric data
i 19 20
K 0 0
A4 -4.148E-01 -1.172E-01
A6 -1.186E + 00-9.748E-01
A8 5.555E-01 1.023E + 00
A10 0.000 E + 00 0.000 E + 00
A12 0.000 E + 00 0.000 E + 00

Various data
f 1.14
FNO 1.85
2ω 82.6
TL 4.414
BF 0.0448
Variable parameter Object distance d0 R14 d14 d20 d22
∞ (POS1) 0.416 0.387 0.120 0.760
7.14 mm (POS2) 0.400 0.299 0.402 0.565
Group movement amount (POS1 → POS2)
Gr2 Gr3
-0.088 0.194

Example 3
Unit: mm
Surface data
i ri di nd d d Ri
0 (OB) d d0
1 2.5424 0.102 1.65844 50.85 1.054
2 0.9246 0.439 0.807
3 2.0808 0.190 1.92286 20.88 0.776
4 3.5916 0.102 1.48749 70.32 0.737
5 1.1233 0.453 0.650
6 -1.5692 0.092 1.67270 32.17 0.624
7 1.1681 0.404 1.88100 40.14 0.643
8-3.0812 0.027 0.638
9 * 1.7767 0.211 1.82080 42.71 0.587
10 * -7.1583 0.029 0.570
11 3.1208 0.229 1.84850 43.79 0.533
12 -1. 8099 0.060 1.69895 30.05 0.512
13 1.7205 0.179 0.464
14 (ST) d d14 R14
15 *-0.9487 0.055 1.83441 37.28 0.398
16 * -3.3164 0.033 0.416
17 3.1258 0.267 1.59282 68.62 0.426
18-0.8904 0.206 0.450
19 * -4.1856 0.132 1.74330 49.33 0.485
20 * -1.8713 d20 0.566
21-4.0518 0.081 1.74077 27.76 0.580
22 d d22 0.693
23 0.07 0.074 1.51480 64.14 0.713
24 BF 1.200
25 (IM) ∞

Aspheric data
i 9 10 15
K 0 0 0
A4 1.636E-02 5.124E-02-4.036E-01
A6 2.187E-02 1.402E-02-2.480E-01
A8 4.840E-03 7.649E-03 1.966E-01
A10 0.000 E + 00 0.000 E + 00 0.000 E + 00
A12 0.000 E + 00 0.000 E + 00 0.000 E + 00
i 16 19 20
K 0 0 0
A4 -7.313E-02 1.200E-01 2.110E-01
A6 1.763E-01 1.845E-01 2.880E-01
A8 7.632E-01 -7.940E-02 1.652E-01
A10 0.000 E + 00 0.000 E + 00-1.677 E-01
A12 0.000 E + 00 0.000 E + 00 0.000 E + 00

Various data
f 1.14
FNO 1.85
2ω 82.7
TL 4.736
BF 0.0448
Variable parameter Object distance d0 R14 d14 d20 d22
∞ (POS1) 0.439 0.347 0.176 0.813
6.58 mm (POS2) 0.419 0.264 0.484 0.587
Group movement amount (POS1 → POS2)
Gr2 Gr3
-0.083 0.226

Example 4
Unit: mm
Surface data
i ri di nd d d Ri
0 (OB) d d0
1 1.6401 0.102 1.51823 58.96 0.869
2 0.8915 0.188 0.726
3 0.9243 0.180 1.92286 20.88 0.684
4 0.8935 0.510 0.608
5-1.0838 0.234 1.72047 34.70 0.552
6 2.2788 0.308 1.77250 49.62 0.583
7-1.4605 0.018 0.592
8 1.4871 0.244 1.59282 68.62 0.599
9-6.8881 0.254 0.587
10 (ST) d d10 R10
11 -1.1493 0.055 1.59270 35.31 0.479
12-39. 1 824 0.02 0.495
13 1.5461 0.289 1.59282 68.62 0.583
14-2.0569 0.325 0.597
15 *-33. 5028 0.117 1. 76450 49. 09 0.628
16 *-2.4463 d16 0.635
17 -1.3689 0.083 1.51742 52.15 0.659
18-22.9117 0.52 0.721
19 0.06 0.069 1.51680 64.12 1.200
20 BF 1.200
21 (IM) ∞

Aspheric data
i 15 16
K 0 0
A4 1.447E-01 1.447E-01
A6 -2.083E-01 -2.083E-01
A8 2.196E + 00 2.196E + 00
A10 -2.759E + 00 -2.759E + 00
A12 0.000 E + 00 0.000 E + 00

Various data
f 1.57
FNO 1.85
2ω 64.9
TL 4.345
BF 0.0462
Variable parameter Object distance d0 R10 d10 d16
∞ (POS1) 0.518 0.521 0.259
9.5 mm (POS2) 0.518 0.315 0.465
Group movement amount (POS1 → POS2)
Gr2
-0.205

Example 5
Unit: mm
Surface data
i ri di nd d d Ri
0 (OB) d d0
1 4.6232 0.102 1.51680 64.13 0.832
2 0.8784 0.354 0.673
3 4.0730 0.258 1.95375 32.33 0.657
4-2.0290 0.083 1. 60342 38.03 0.640
5 3.2358 0.108 0.569
6 -1.2945 0.172 1.68893 31.16 0.548
7 1.7517 0.329 1.85150 40.78 0.631
8-1.7517 0.018 0.645
9 1.1917 0.368 1.49700 81.61 0.653
10-3.5528 0.009 0.631
11 * 4.1556 0.057 1.83441 37.28 0.587
12 * 1.9836 0.187 0.557
13 (ST) d d13 R13
14 -0.9917 0.062 1.61293 36.94 0.478
15-5.7 790 0.012 0.495
16 2.1244 0.282 1.59282 68.62 0.544
17 -1.3918 0.209 0.562
18 * -8.4171 0.098 1.69350 53.20 0.599
19 *-2.8176 d19 0.614
20 * -1.8973 0.083 1.58313 59.46 0.645
21 * -6.9348 d21 0.704
22 0.07 0.074 1.51680 64.13 1.200
23 BF 1.200
24 (IM) ∞

Aspheric data
i 11 12 18
K -4.9288 -0.4693 15.3255
A4 -9.582E-02 -8.355E-02 -2.063E-01
A6 5.043E-01 5.689E-01 6.890E-02
A8-4.618E-01-2.913E-01 0.000E + 00
A10 0.000 E + 00 0.000 E + 00 0.000 E + 00
A12 0.000 E + 00 0.000 E + 00 0.000 E + 00
i 19 20 21
K-0.9347-0.1889 0
A4-2.416E-03 -1.143E-01-9.359E-02
A6 1.158E-01 -1.549E-01 -1.873E-01
A8 1.983E-01 0.000E + 00 1.909E-01
A10-1.130E-01 0.000E + 00 -1.298E-01
A12 0.000 E + 00 0.000 E + 00 0.000 E + 00

Various data
f 1.57
FNO 1.85
2ω 64.9
TL 4.553
BF 0.0425
Variable parameter Object distance d0 R13 d13 d19 d21
∞ (POS1) 0.533 0.514 0.229 0.751
7.0 mm (POS2) 0.509 0.283 0.666 0.545
Group movement amount (POS1 → POS2)
Gr2 Gr3
-0.230 0.206

DU digital equipment LU imaging optical device LN imaging lens Gr1 first lens group Gr2 second lens group Gr3 third lens group Gr1a front lens group Gr1b rear lens group L1 # lens # 1 from the object side in the first lens group (# = 1, 2, ..., 8)
L2 # # lens from the object side in the second group (# = 1, 2, 3)
L31 Lenses that make up the third lens group ST Aperture SR Image sensor SS Photosensitive 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 (11)

From the object side, it has a first group of positive power, a second group of positive power, and a third group of negative power, and in focusing from infinity to a close object, the first group is fixed in position and An imaging lens in which an interval between the first group and the second group is reduced and an interval between the second group and the third group is increased,
In the second group, a negative lens and a positive lens are disposed in order from the object side,
When the first group is divided into two groups with the largest air gap in the first group as a boundary, assuming that the object side group is a front group and the image side group is a rear group, the following conditional expressions An imaging lens characterized by satisfying (1) to (6);
1.3 <−f1a / f <3.5 (1)
0.9 <f1b / f <1.5 (2)
1.2 <f2 / f <1.8 (3)
1.2 <| f3 / f2 | <4.0 (4)
−1.8 <(ra + rb) / (ra−rb) <− 0.05 (5)
dd_2p-νd_2n> 25 (6)
However,
f1a: focal length of front group,
f1b: focal length of rear group,
f: focal length of the whole system,
f2: focal length of the second group,
f3: focal length of the third group,
ra: radius of curvature of the surface closest to the image side in the front group,
rb: radius of curvature of the surface closest to the object side in the rear group,
d d _2 p: Abbe number of the positive lens disposed second from the object side in the second group
d d _2 n: Abbe number of the negative lens placed first from the object side in the second group
It is. The imaging lens according to claim 1, wherein the positive lens having the strongest power in the second group satisfies the following conditional expressions (7) and (8):
0.45 <f2p / f2 <1.2 (7)
θg, F-(-0.0018 d d + 0.6 484)> 0.009 (8)
However,
f2p: focal length of the most powerful positive lens in the second group,
f2: focal length of the second group,
θg, F: Partial dispersion ratio of lens material,
θg, F = (Ng-NF) / (NF-NC)
Ng: refractive index with respect to g-line,
NF: refractive index with respect to F ray,
NC: refractive index with respect to C ray,
d d: Abbe number related to d-line of lens material,
It is. 3. The imaging lens according to claim 1, further comprising at least two positive lenses in the second group, wherein the following conditional expression (9) is satisfied:
2.0 <f2_ip / f2_op <4.5 (9)
However,
f2_op: focal length of the positive lens closest to the object in the second group,
f2_ip: focal length of the positive lens closest to the image side in the second group,
It is.   The imaging lens according to any one of claims 1 to 3, wherein the lens closest to the image in the second group is an aspheric lens.   The imaging lens according to any one of claims 1 to 4, wherein the surface closest to the object side in the third group has a shape in which a concave surface is directed to the object side.   The imaging according to any one of claims 1 to 5, wherein in focusing from infinity to a closest object, the second group moves to the object side, and the third group moves to the image plane side. lens. The imaging lens according to claim 6, wherein the following conditional expression (10) is satisfied:
0.2 <| d_2Gr / d_3Gr | <1.2 (10)
However,
d_2Gr: Movement amount of second group in focusing from infinity to any object distance,
d_3Gr: moving amount of the third group in focusing from infinity to any object distance,
It is.   The imaging lens according to any one of claims 1 to 7, wherein a diaphragm is disposed between the first group and the second group. The imaging lens according to any one of claims 1 to 8, wherein the following conditional expression (11) is satisfied:
0.2 <f / TL <0.45 (11)
However,
f: focal length of the whole system,
TL: distance from the surface closest to the object side of the imaging lens to the image plane,
It is.   An imaging lens according to any one of claims 1 to 9 and an imaging device for converting an optical image formed on the imaging surface into an electrical signal, the subject on the imaging surface of the imaging device An imaging optical apparatus, wherein the imaging lens is provided such that an optical image of the above is formed.   A digital apparatus characterized in that at least one of still image shooting and moving image shooting of an object is added by providing the imaging optical device according to claim 10.

Images