JP2017227799A - Image capturing lens, image capturing optical device, and digital equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact image capturing lens which has a wide view angle represented by an imaging view angle 2ω in excess of 65 degrees and a bright F-number, and yet offers reduced distortion aberration and uniform image quality over an entire image, and to provide an image capturing optical device and digital equipment having the same.SOLUTION: An image capturing lens LN has a first lens group Gr1 comprising first through fifth lenses L11-L15 having negative, negative, positive, negative, and positive power, respectively, and is configured to shift focus to an object at a short distance by moving a second lens group Gr2 toward the object side. The first lens L11 and the second lens L12 are meniscus-shaped and are convex on the object side, and the fourth lens L14 and the fifth lens L15 constitute a cemented lens and satisfy the following conditional expressions: -0.7<φ14/φ<-0.3, 0.1<φ15/φ<0.4, -3<φ14/φ15<-1.5, where φ14 represents power of the fourth lens, φ15 represents power of the fifth lens, and φ represents power of the entire system.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging lens, an imaging optical device, and a digital device. For example, an image of a subject is captured by an imaging device (for example, a CCD (Charge Coupled Device) type image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor, or the like. A compact, wide-angle, large-aperture imaging lens suitable for an interchangeable lens digital camera captured by a solid-state imaging device), 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. In addition, a wide-angle lens having a large aperture with an F-number of 2 or less is demanded in response to a demand for enlargement of the imaging region, while the wide angle of view is 2 °: 65 ° or more. In order to meet such demands, Patent Document 1 proposes an imaging lens as an interchangeable lens for a lens interchangeable digital camera.

JP 05-034592 A

  The imaging lens proposed in Patent Document 1 realizes a wide angle of view, but lacks correction of various aberrations including distortion, and the F value is about 2.8.

  The present invention has been made in view of such a situation, and an object of the present invention is to suppress distortion aberration while realizing a wide angle of view exceeding 2 °: 65 degrees and a bright F value, and to suppress distortion in the entire image. It is an object of the present invention to provide a small imaging lens capable of obtaining uniform image quality, an imaging optical apparatus and a digital apparatus having the same.

In order to achieve the above object, the imaging lens of the first invention comprises, in order from the object side, a first group and a second group having positive power,
The first group includes, in order from the object side, a first lens having negative power, a second lens having negative power, a third lens having positive power, a fourth lens having negative power, and positive power. A fifth lens having
The first lens and the second lens have a meniscus shape convex toward the object side;
The fourth lens and the fifth lens constitute a cemented lens,
Focusing on a short-distance object is performed by moving the second group to the object side with the position of the first group fixed.
The following conditional expressions (1) to (3) are satisfied.
−0.7 <φ14 / φ <−0.3 (1)
0.1 <φ15 / φ <0.4 (2)
−3 <φ14 / φ15 <−1.5 (3)
However,
φ14: power of the fourth lens in the first group,
φ15: the power of the fifth lens in the first group,
φ: Power of the entire system,
It is.

  The imaging lens according to a second aspect is characterized in that, in the first aspect, the cemented lens composed of the fourth and fifth lenses has a negative combined power.

An imaging lens according to a third aspect of the invention is characterized in that, in the first or second aspect of the invention, the following conditional expression (4) is satisfied.
Nd15> 1.8 (4)
However,
Nd15: Refractive index related to the d-line of the fifth lens of the first group,
It is.

  The imaging lens of a fourth invention is characterized in that, in any one of the first to third inventions, the lens located closest to the image side in the first group has a positive power.

An imaging lens according to a fifth invention is characterized in that, in any one of the first to fourth inventions, a lens located adjacent to the object side of the diaphragm satisfies the following conditional expression (5). .
θgf − (− 0.00162νd + 0.6415) <0.012 (5)
However,
θgf: partial dispersion ratio of the 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 a sixth invention is characterized in that, in any one of the first to fifth inventions, the first group has positive power.

An imaging lens according to a seventh invention is characterized in that, in any one of the first to sixth inventions, the following conditional expression (6) is satisfied.
Nd13> 1.8 (6)
However,
Nd13: the refractive index of the third lens of the first group with respect to the d-line,
It is.

  The imaging lens of an eighth invention is characterized in that, in any one of the first to seventh inventions, the second group has two or more positive lenses continuously from the object side.

  An imaging lens according to a ninth aspect is the imaging lens according to any one of the first to eighth aspects, wherein the second group includes, in order from the object side, a positive lens, a positive lens, a positive lens, a negative lens, a diaphragm, and a negative lens. , A positive lens, a positive lens, and a positive lens.

  An imaging lens of a tenth invention is characterized in that in any one of the first to ninth inventions, the imaging lens has three or more aspheric lenses.

  An imaging optical device according to an eleventh aspect includes an imaging lens according to any one of the first to tenth 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 twelfth aspect of the present invention, there is provided a digital apparatus including the imaging optical device according to the eleventh aspect of the present invention, to which at least one function of still image shooting and moving image shooting of a subject is added.

  According to the present invention, there is provided a small imaging lens and an imaging optical device that can achieve a wide field angle of 2ω: 65 degrees and a bright F value while suppressing distortion while achieving uniform image quality over the entire image. Can be realized. By using the imaging lens or the imaging optical device for a digital device (for example, a digital camera), a high-performance image input function can be added to the digital device in a 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). 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 lateral aberration diagram at the first focus position in Example 1; FIG. 5 is a lateral aberration diagram at the second focus position in Example 1; FIG. 10 is a lateral aberration diagram at the first focus position in Example 2. FIG. 6 is a lateral aberration diagram at the second focus position in Example 2. FIG. 10 is a lateral aberration diagram at the first focus position in Example 3. FIG. 6 is a lateral aberration diagram at the second focus position in Example 3. FIG. 12 is a lateral aberration diagram at the first focus position in Example 4; FIG. 6 is a lateral aberration diagram at the second focus position in Example 4; FIG. 3 is a schematic diagram illustrating a schematic configuration example of a digital device equipped with an imaging optical device.

  Hereinafter, an imaging lens, an imaging optical device, and a digital device according to an embodiment of the present invention will be described. An imaging lens according to an embodiment of the present invention includes, in order from the object side, a first group and a second group having positive power (power: an amount defined by the reciprocal of the focal length), and the first lens. In order from the object side, the group has a first lens having negative power, a second lens having negative power, a third lens having positive power, a fourth lens having negative power, and a fifth lens having positive power. And a lens. The first lens and the second lens have a meniscus shape convex toward the object side, the cemented lens is configured by the fourth lens and the fifth lens, and the position of the first group is fixed. Then, the second group is moved to the object side to perform focusing on a short-distance object.

Further, the imaging lens satisfies the following conditional expressions (1) to (3).
−0.7 <φ14 / φ <−0.3 (1)
0.1 <φ15 / φ <0.4 (2)
−3 <φ14 / φ15 <−1.5 (3)
However,
φ14: power of the fourth lens (that is, the reciprocal of the focal length f14 of the fourth lens constituting the first group),
φ15: power of the fifth lens (that is, the reciprocal of the focal length f15 of the fifth lens constituting the first group),
φ: power of the entire system (that is, the reciprocal of the combined focal length f of the entire system),
It is.

  In the first group, by giving negative power to the first lens and the second lens in order from the object side, each power can be weakened and various aberrations represented by distortion aberration can be reduced. In addition, the first and second lenses are both meniscus shaped with a convex surface facing the object side, so that rays incident from a wide angle of view are gently bent to prevent field curvature and coma. Negative distortion generated in the first lens and the second lens can be appropriately corrected by the third lens having a positive power.

  By making the fourth lens and the fifth lens a negative-positive cemented lens and having an appropriate power arrangement that satisfies the conditional expressions (1) to (3), it is possible to reduce the occurrence of spherical aberration and field curvature, and to achieve design performance. Not only can the final product performance be improved. A resin layer having a thickness on the optical axis of 1 mm or less does not constitute the cemented lens. Therefore, a lens (for example, a composite aspherical lens) in which a resin is formed on the lens surface with a core thickness of 1 mm or less as a material for forming the lens is considered as a single lens, not a cemented lens.

  Conditional expression (1) defines a preferable condition range regarding the power of the fourth lens. If the lower limit of conditional expression (1) is exceeded, the negative power will not become too strong, and the increase in the total length can be prevented. On the other hand, below the upper limit of conditional expression (1), the negative power does not become too weak, and various aberrations such as field curvature and axial chromatic aberration can be corrected well.

  Conditional expression (2) defines a preferable condition range regarding the power of the fifth lens. If the lower limit of conditional expression (2) is exceeded, the positive power does not become too weak, and the first group can be brought closer to an afocal optical system, so that fluctuations in aberrations can be suppressed when focusing on a close object. it can. Further, it is possible to prevent the total length from increasing. On the other hand, below the upper limit of the conditional expression (2), the positive power does not become too strong, and the occurrence of various aberrations including spherical aberration can be prevented.

  Conditional expression (3) optimizes the power defined by conditional expression (1) and conditional expression (2) by the power ratio of the fourth lens and the fifth lens in the first group. If the lower limit of conditional expression (3) is exceeded, the power of the negative lens will not be too strong with respect to the positive lens, and it will be possible to prevent distortion from becoming too large. Below the upper limit of conditional expression (3), the power of the negative lens does not become too weak with respect to the positive lens, and various aberrations such as field curvature and longitudinal chromatic aberration can be corrected well.

  Setting the power arrangement of the 4th lens and 5th lens to satisfy the conditional expressions (1) to (3) realizes uniform image quality and bright F-number in the entire image while improving the aberration and having a wide angle of view. can do. However, when each lens is decentered, the occurrence of aberration, particularly the occurrence of coma on the axis, becomes significant, and it may be difficult to exhibit its original performance. In order to solve this problem, the fourth lens and the fifth lens constitute a cemented lens. If the fourth and fifth lenses are cemented lenses, there is no problem caused by the eccentricity of the lens, so that not only the design performance but also the final product performance can be improved.

  In other words, according to the above-described characteristic configuration, a small imaging that can obtain a uniform image quality over the entire image while suppressing a variety of aberrations such as distortion while realizing a wide field angle of 2ω: 65 degrees and a bright F value. A lens and an imaging optical device including the lens can be realized. 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 an imaging lens having the above-described characteristic configuration is suitable as an interchangeable lens for a digital camera or a video camera, a lightweight, small, and high-performance 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.

Regarding the fourth lens, it is desirable to satisfy the following conditional expression (1a), and it is more desirable to satisfy the conditional expression (1b).
−0.6 <φ14 / φ <−0.3 (1a)
−0.55 <φ14 / φ <−0.35 (1b)
These conditional expressions (1a) and (1b) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (1). Therefore, the above effect can be further enhanced by preferably satisfying conditional expression (1a), more preferably satisfying conditional expression (1b).

Regarding the fifth lens, it is preferable that the following conditional expression (2a) is satisfied, and it is more preferable that the conditional expression (2b) is satisfied.
0.2 <φ15 / φ <0.4 (2a)
0.2 <φ15 / φ <0.3 (2b)
These conditional expressions (2a) and (2b) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (2). Therefore, the above effect can be further enhanced by preferably satisfying conditional expression (2a), more preferably satisfying conditional expression (2b).

Regarding the fourth and fifth lenses, it is preferable that the following conditional expression (3a) is satisfied.
-3 <φ14 / φ15 <-2 (3a)
This conditional expression (3a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (3). Therefore, the above effect can be further increased preferably by satisfying conditional expression (3a).

  It is preferable that the cemented lens including the fourth and fifth lenses has a negative combined power. If the fourth lens with negative power and the fifth lens with positive power are cemented lenses, and the cemented lens has negative power, it is possible to correct curvature of field, so that a good image can be obtained up to the periphery of the screen. it can.

Regarding the fifth lens, it is preferable that the following conditional expression (4) is satisfied.
Nd15> 1.8 (4)
However,
Nd15: Refractive index related to the d-line of the fifth lens of the first group,
It is.

  When the fifth lens constituting the cemented lens in the first group satisfies the conditional expression (4), the curvature of the lens surface can be reduced (that is, the curvature can be reduced), and the generation of spherical aberration is effective. Can be reduced. In addition, since the curvature of the joining surface can be reduced, joining is facilitated, and there is an advantage that reliability is improved.

  The lens located closest to the image side in the first group preferably has positive power. When the most image-side lens in the first group has positive power, the height of light incident on the second group can be reduced, and the focus group can be downsized. In addition, since the first group can be brought close to an afocal optical system, it is possible to suppress fluctuations in aberrations when focusing on a short-distance object.

It is desirable that the lens located adjacent to the object side of the diaphragm satisfies the following conditional expression (5).
θgf − (− 0.00162νd + 0.6415) <0.012 (5)
However,
θgf: partial dispersion ratio of the 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 expression (5) defines a preferable range regarding the partial dispersion ratio of the lenses located adjacent to the object side of the stop. According to this configuration, it is possible to reduce axial chromatic aberration and prevent color blurring.

It is desirable that the lens positioned adjacent to the object side of the diaphragm satisfies the following conditional expression (5a), and more desirably satisfies the following conditional expression (5b).
θgf − (− 0.00162νd + 0.6415) <0.006 (5a)
θgf − (− 0.00162νd + 0.6415) <0.003 (5b)
These conditional expressions (5a) and (5b) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (5). Therefore, the above effect can be further enhanced by preferably satisfying conditional expression (5a), more preferably satisfying conditional expression (5b).

  The first group preferably has positive power. By giving positive power to the first group, the total length can be shortened.

Regarding the third lens, it is preferable that the following conditional expression (6) is satisfied.
Nd13> 1.8 (6)
However,
Nd13: the refractive index of the third lens of the first group with respect to the d-line,
It is.

  In order to correct distortion occurring in the first lens and the second lens having negative power, the third lens is desired to have a strong curvature (that is, a curvature having a large absolute value). By satisfying conditional expression (6), the curvature of the lens surface can be relaxed (that is, the absolute value of the curvature can be reduced). Therefore, the occurrence of spherical aberration can be effectively reduced.

  The second group preferably includes two or more positive lenses continuously from the object side. According to this configuration, when the positive power is borne by two or more lenses, the light incident on the second group can be gently bent, and the occurrence of various aberrations including spherical aberration is effectively reduced. be able to.

  The second group preferably includes, in order from the object side, a positive lens, a positive lens, a positive lens, a negative lens, a diaphragm, a negative lens, a positive lens, a positive lens, and a positive lens. According to this configuration, since the power arrangement of the lenses constituting the second group is symmetric with respect to the stop, the occurrence of coma aberration, distortion aberration, lateral chromatic aberration, and the like can be reduced.

  It is desirable to have three or more aspheric lenses. When the imaging lens having the above-described characteristic configuration has three or more aspheric lenses, each aspheric lens can be specialized for specific aberration correction, and various aberrations can be corrected more effectively. Can do. For example, when an aspheric lens is disposed on the first to third lenses from the object side in the first group, it is possible to effectively correct distortion and curvature aberrations in particular. When an aspherical lens is disposed on the first to third lenses from the stop, spherical aberration can be corrected particularly effectively. When an aspherical lens is disposed on the first to third lenses from the image side, coma and curvature aberrations can be particularly effectively corrected.

  The imaging lens described above is suitable for use as an imaging lens for a digital device with an image input function (for example, an interchangeable lens digital camera). By combining this with an imaging device, an image of a subject is optically displayed. It is possible to configure an image pickup 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, An image pickup device (image sensor) that converts an optical image formed by the image pickup lens into an electrical signal is provided. 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. 17 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. 17 includes an imaging lens LN (AX: optical axis) that forms an optical image (image plane) IM of the object in order from the object (that is, 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 may be configured to be rotatable with respect to the main body of the digital device DU. The unitized imaging optical device LU is used as an interchangeable lens with an image sensor, and the digital device DU (that is, the lens) You may comprise so that attachment or detachment with respect to the main body of a replaceable camera is possible.

  The imaging lens LN is a wide-angle lens having a two-group configuration, and the second group having a positive power along the optical axis AX in a state where the position of the first group is fixed (that is, the position is fixed with respect to the image plane IM). By moving to the object side, focusing on a short-distance object is performed, 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 fourth embodiments. 1 to 4 are lens configuration diagrams respectively corresponding to the imaging lenses LN constituting the first to fourth embodiments, and the lens arrangement at the first focus position POS1 (subject infinite state) is an optical cross section. Is shown. The first to fourth embodiments have, in order from the object side, a positive two-group configuration including a first group Gr1 having a positive power and a second group Gr2 having a positive power, and are compact and wide-angle. -It is suitable for a large-diameter interchangeable lens (focal length 28 mm, F1.4 class). 1 to 4, L1 # (# = 1, 2,..., 6) is the #th lens from the object side in the first group Gr1, and L2 # (# = 1, 2,..., 8) is This is the #th lens from the object side in the second group Gr2.

  In the first to fourth embodiments, when focusing on a short-distance object, the first group Gr1 is fixed with respect to the image plane IM, and the second group Gr2 moves toward the object side along the optical axis AX. To do. 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. Further, in the third embodiment, it is desirable to divide the second group Gr2 into the front group and the rear group at the position of the stop ST and to feed them out to the object side with different amounts of movement (so-called floating). This makes it possible to correct curvature of field caused by fluctuations in shooting distance, and the image quality at the shortest shooting distance is further improved. At this time, the aperture stop ST may move together with the front group or may move together with the rear group in consideration of the configuration of the lens barrel and the distance from the lens.

  In the first to fourth embodiments, the first group Gr1 includes, in order from the object side, a negative power first lens L11, a negative power second lens L12, a positive power third lens L13, and a negative power. The lens includes a fourth lens L14 having power, a fifth lens L15 having positive power, and a sixth lens L16 having positive power. The first lens L11 and the second lens L12 have a convex meniscus shape on the object side, and the fourth lens L14 and the fifth lens L15 constitute a negative power cemented lens LS. Further, by appropriately setting the power of the fourth lens L14 and the fifth lens L15, and the combined power thereof (power of the cemented lens LS) and the like, favorable aberration correction can be performed. Further, the positive power of the sixth lens L16 enables the second group Gr2 to be reduced in size and focus performance to be improved.

  In the first embodiment, the second group Gr2 includes, in order from the object side, a positive lens L21, a positive lens L22, a positive lens L23, a negative lens L24, a stop ST, a negative lens L25, and a positive lens. L26, a positive lens L27, and a positive lens L28. In the second to fourth embodiments, the second group Gr2 includes, in order from the object side, a positive lens L21, a positive lens L22, a negative lens L23, a diaphragm ST, a negative lens L24, and a positive lens L25. And a positive lens L26 and a positive lens L27. In the first to fourth embodiments, the stop (aperture stop) ST is provided in the second group Gr2, and the lens located adjacent to the object side of the stop ST is negative in the first embodiment. The lens L24 is the negative lens L23 in the second to fourth embodiments. If the partial dispersion ratio of the lens located adjacent to the object side of the aperture stop ST is set within a predetermined range, it is possible to reduce axial chromatic aberration and prevent color blurring.

  In the imaging lens LN (FIG. 1) of the first embodiment, each lens group is configured as follows in order from the object side. The first group Gr1 includes a compound aspherical lens (image side is aspherical) composed of a negative meniscus lens L11 convex toward the object side, a negative meniscus lens L12 convex toward the object side, a biconvex positive lens L13, It is composed of a negative cemented lens LS composed of a biconcave negative lens L14 and a biconvex positive lens L15, and a biconvex positive lens L16 (power arrangement: negative negative positive positive positive). The second group Gr2 includes a positive meniscus lens L21 convex on the object side, a biconvex positive lens L22, a cemented lens composed of a biconvex positive lens L23 and a biconcave negative lens L24, a stop ST, and a biconcave A negative lens L25 and a biconvex positive lens L26 (image side is aspheric), a biconvex positive lens L27, and a positive meniscus lens L28 (both sides are aspheric) convex to the image side. (Power arrangement: positive / positive / negative / ST / negative / positive / positive / positive).

  In the imaging lens LN (FIG. 2) of the second embodiment, each lens group is configured in order from the object side as follows. The first group Gr1 includes a composite aspherical lens (image side is aspherical) composed of a negative meniscus lens L11 convex toward the object side, a negative meniscus lens L12 convex toward the object side, and a positive meniscus lens convex toward the image side. L13, a negative cemented lens LS composed of a biconcave negative lens L14, a positive meniscus lens L15 convex toward the object side, and a biconvex positive lens L16 (power arrangement: negative negative positive positive positive ). The second group Gr2 includes a biconvex positive lens L21, a cemented lens composed of a biconvex positive lens L22 and a biconcave negative lens L23, an aperture ST, a biconcave negative lens L24, and a biconvex positive lens L25. It is composed of a cemented lens composed of (aspheric image side surface), a positive biconvex lens L26, and a positive meniscus lens L27 convex on the image side (both aspheric surfaces) (power arrangement: positive / negative / ST, negative positive positive positive).

  In the imaging lens LN (FIG. 3) of the third embodiment, each lens group is configured as follows in order from the object side. The first group Gr1 includes a negative meniscus lens L11 that is convex on the object side, a negative meniscus lens L12 that is convex on the object side (image side is aspheric), a positive meniscus lens L13 that is convex on the image side, and a biconcave negative lens. The lens includes a negative cemented lens LS composed of a lens L14 and a biconvex positive lens L15, and a biconvex positive lens L16 (power arrangement: negative / negative / positive / positive / positive). The second group Gr2 includes a biconvex positive lens L21, a cemented lens composed of a biconvex positive lens L22 and a biconcave negative lens L23, an aperture ST, a biconcave negative lens L24, and a biconvex positive lens L25. And a positive meniscus lens L27 (both surfaces are aspherical) (power arrangement: positive / negative / ST / negative positive / positive) .

  In the imaging lens LN (FIG. 4) according to the fourth embodiment, each lens group is configured as follows in order from the object side. The first group Gr1 includes a compound aspherical lens (image side is aspherical) composed of a negative meniscus lens L11 convex toward the object side, a negative meniscus lens L12 convex toward the object side, a biconvex positive lens L13, The lens includes a biconcave negative lens L14, a negative cemented lens LS composed of a positive meniscus lens L15 convex on the object side, and a biconvex positive lens L16 (power arrangement: negative negative positive positive negative positive). The second group Gr2 includes a biconvex positive lens L21, a cemented lens composed of a biconvex positive lens L22 and a biconcave negative lens L23, an aperture ST, a biconcave negative lens L24, and a biconvex positive lens L25. A cemented lens, a biconvex positive lens L26 (both aspheric surfaces), and a positive meniscus lens L27 convex on the image side (power arrangement: positive / negative / ST / negative positive / positive) .

  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 4 (EX1 to 4) listed here are numerical examples corresponding to the first to fourth embodiments, respectively, and are lens configuration diagrams representing the first to fourth embodiments. (FIGS. 1-4) has shown the optical structure of the corresponding Examples 1-4, 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, IM: image surface), paraxial radius of curvature Ri (mm), axial top surface spacing. Di (mm), refractive index Nd for d line (wavelength: 587.56 nm), and Abbe number νd for 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 Ri),
K: conic constant,
Aj: j-order aspheric coefficient,
It is.

  As various data, the focal length f (mm), F number (F value) FNO. , Full field angle 2ω (°), maximum image height y′max (mm), total lens length TL (mm), back focus BF (mm), partial dispersion ratio θgf as related data of conditional expression (5), first group The focal length f1 (mm) of Gr1, the focal length f2 (mm) of the second group Gr2, the focal length f14 (mm) of the fourth lens L4, the focal length f15 (mm) of the fifth lens L5, the fourth and fifth The focal length f1s (mm) of the cemented lens LS composed of the lenses L4 and L5 and the focal length f1i of the lens L16 located closest to the image side in the first group Gr1 are shown. However, in the back focus BF, the distance from the lens final surface to the paraxial image plane IM is expressed by an air conversion 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. It is a thing. Table 1 shows values corresponding to the conditional expressions of the respective examples.

  5 to 8 are longitudinal aberration diagrams corresponding to Examples 1 to 4 (EX1 to EX4), respectively, and (A) to (C) are the first focus positions POS1 and (D) to (F). Indicates various aberrations at the second focus position POS2. 5 to 8, (A) and (D) are spherical aberration diagrams, (B) and (E) are astigmatism diagrams, and (C) and (F) are distortion 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. 9, 11, 13 and 15 are lateral aberration diagrams respectively corresponding to Examples 1 to 4 (EX1 to EX4) at the first focus position POS1, and FIGS. FIGS. 16A and 16B are lateral aberration diagrams respectively corresponding to Examples 1 to 4 (EX1 to EX4) at the second focus position POS2. 9 to 16, the meridional coma aberration (mm) is shown in the left column, the sagittal coma aberration (mm) is shown in the right column, and the image height Y ′ (mm) is shown. 5 to 8, the alternate long and short dash line is the C line (wavelength 656.28 nm), the solid line is the d line (wavelength 587.56 nm), and the broken line is the g line (wavelength 435.84 nm).

Example 1
Unit: mm
Surface data
i Ri (mm) Di (mm) Nd νd
0 (OB) ∞ ∞ to 105.61
1 70.017 2.50 1.68893 31.2
2 29.640 10.58
3 94.105 2.40 1.71300 53.9
4 31.773 0.05 1.51380 53.0
5 * 27.197 9.49
6 164.736 4.94 1.84666 23.8
7 -131.025 4.85
8 -46.832 2.15 1.56883 56.0
9 134.737 4.17 1.88300 40.8
10 -366.912 3.03
11 70.316 7.09 1.77250 49.6
12 -99.338 7.70 to 1.42
13 55.349 4.20 1.72916 54.7
14 289.177 0.15
15 111.310 4.00 1.69680 55.5
16 -158.345 0.15
17 322.096 5.79 1.59282 68.6
18 -37.124 1.50 1.73800 32.3
19 37.221 5.60
20 (ST) ∞ 5.78
21 -24.127 1.30 1.80610 33.3
22 47.257 5.35 1.83220 40.1
23 * -131.725 0.30
24 64.397 8.98 1.59282 68.6
25 -28.781 0.15
26 * -280.388 3.71 1.69350 53.2
27 * -55.502 38.47 to 44.77
28 (IM) ∞

Aspheric data 5th surface
K = -1.81201E + 00
A4 = 5.07910E-06
A6 = -6.20262E-09
A8 = 1.15776E-11
A10 = -2.04179E-14
A12 = 1.90900E-17

Aspheric data 23rd surface
K = 0.00000E + 00
A4 = 3.38686E-06
A6 = -1.03975E-09
A8 = 5.14761E-11
A10 = 1.18111E-14
A12 = -1.11410E-16

Aspheric data 26th surface
K = 0.00000E + 00
A4 = -1.45264E-05
A6 = -2.74974E-08
A8 = 4.08509E-11
A10 = -1.22050E-13
A12 = 2.18038E-15
A14 = -3.26000E-18

Aspherical data 27th surface
K = 1.61294E + 00
A4 = -4.86948E-06
A6 = -2.36249E-08
A8 = 7.19463E-11
A10 = -3.12054E-13
A12 = 2.11838E-15
A14 = -2.42000E-18

Various data
f = 28.41
FNO. = 1.45
2ω = 75.42
y'max = 21.6
TL = 144.38
BF = 38.47
θgF = 0.5899
f1 = 151.32
f2 = 52.75
f14 = -60.83
f15 = 112.04
f1s = -137.42
f1i = 54.29

Example 2
Unit: mm
Surface data
i Ri (mm) Di (mm) Nd νd
0 (OB) ∞ ∞ to 107.60
1 66.672 2.50 1.68893 31.2
2 28.712 8.98
3 56.823 2.40 1.71300 53.9
4 28.412 0.05 1.51380 53.0
5 * 24.516 11.59
6 -2348.135 4.07 1.84666 23.8
7 -92.947 4.37
8 -43.410 2.15 1.51742 52.2
9 80.132 4.33 1.90366 31.3
10 1085.535 1.91
11 73.043 6.88 1.78590 43.9
12 -91.416 8.54 to 2.58
13 46.311 6.62 1.69680 55.5
14 -141.275 0.15
15 194.148 6.41 1.59282 68.6
16 -35.968 1.60 1.69895 30.1
17 35.308 5.75
18 (ST) ∞ 5.93
19 -23.264 1.30 1.80610 33.3
20 136.595 3.84 1.80860 40.4
21 * -106.158 0.30
22 76.607 9.38 1.59282 68.6
23 -27.879 0.15
24 * -1000.000 4.67 1.58313 59.4
25 * -47.677 38.46 to 44.47
26 (IM) ∞

Aspheric data 5th surface
K = -1.10465E + 00
A4 = 3.19310E-06
A6 = -6.36058E-09
A8 = 2.46244E-11
A10 = -5.90274E-14
A12 = 5.62500E-17

Aspheric data 21st surface
K = 0.00000E + 00
A4 = 7.43892E-06
A6 = -1.81682E-09
A8 = 1.12774E-10
A10 = -5.38027E-13
A12 = 1.58865E-15
A14 = -2.11000E-18

Aspheric data 24th surface
K = 0.00000E + 00
A4 = -8.53923E-06
A6 = -2.53210E-08
A8 = 1.21664E-10
A10 = -4.87477E-13
A12 = 1.66812E-15
A14 = -1.32000E-18

Aspheric data 25th surface
K = -2.80034E-02
A4 = -2.22686E-06
A6 = -1.70714E-08
A8 = 4.04178E-11
A10 = -7.22433E-15
A12 = 1.79700E-17
A14 = 8.80000E-19

Various data
f = 28.00
FNO. = 1.45
2ω = 76.22
y'max = 21.6
TL = 142.33
BF = 38.46
θgF = 0.6028
f1 = 196.28
f2 = 51.26
f14 = -54.10
f15 = 95.55
f1s = -126.94
f1i = 52.63

Example 3
Unit: mm
Surface data
i Ri (mm) Di (mm) Nd νd
0 (OB) ∞ ∞ to 138.17
1 84.724 2.50 1.83400 37.4
2 28.860 5.07
3 35.391 2.50 1.74320 49.3
4 * 23.788 14.14
5 -106.146 3.20 1.90366 31.3
6 -68.380 3.84
7 -40.703 2.15 1.51680 64.2
8 630.888 4.10 1.84666 23.8
9 -145.820 0.20
10 78.882 7.80 1.83481 42.7
11 -108.522 6.87 to 1.92
12 47.354 7.71 1.72916 54.7
13 -130.704 0.15
14 218.659 6.50 1.59282 68.6
15 -39.980 1.76 1.69895 30.1
16 41.230 7.32
17 (ST) ∞ 6.54
18 -24.171 1.30 1.80610 33.3
19 73.665 4.76 1.61800 63.4
20 -88.480 1.00
21 58.034 9.29 1.59282 68.6
22 -35.531 0.15
23 * -591.406 4.54 1.74320 49.3
24 * -51.826 38.45 to 43.39
25 (IM) ∞

Aspheric data 4th surface
K = -2.11415E-01
A4 = -3.13492E-06
A6 = -6.95430E-09
A8 = 7.46840E-12
A10 = -2.12227E-14

Aspheric data 23rd surface
K = 0.00000E + 00
A4 = -1.26144E-05
A6 = -8.93725E-09
A8 = -6.31579E-11
A10 = 2.26171E-13
A12 = -1.83200E-16

Aspheric data 24th surface
K = 1.10874E + 00
A4 = -2.22064E-06
A6 = -8.29680E-09
A8 = -3.55044E-11
A10 = 1.88045E-13
A12 = -2.13667E-16
A14 = 6.33384E-20

Various data
f = 28.00
FNO. = 1.45
2ω = 76.22
y'max = 21.6
TL = 141.84
BF = 38.45
θgF = 0.6028
f1 = 447.46
f2 = 52.10
f14 = -73.91
f15 = 140.23
f1s = -164.01
f1i = 55.77

Example 4
Unit: mm
Surface data
i Ri (mm) Di (mm) Nd νd
0 (OB) ∞ ∞ to 97.87
1 58.571 2.60 1.80610 33.3
2 29.732 6.90
3 43.559 2.50 1.70154 41.2
4 26.564 0.05 1.51380 53.0
5 * 22.956 11.38
6 449.499 4.01 1.84666 23.8
7 -123.672 4.69
8 -44.185 2.15 1.51680 64.2
9 61.803 4.61 1.90366 31.3
10 175.163 4.25
11 69.416 6.61 1.78590 43.9
12 -91.544 7.59 to 1.19
13 45.255 6.73 1.69680 55.5
14 -130.769 0.15
15 155.733 6.06 1.59282 68.6
16 -37.096 1.75 1.69895 30.1
17 40.187 4.30
18 (ST) ∞ 6.19
19 -23.672 1.30 1.80610 33.3
20 42.685 5.54 1.59282 68.6
21 -86.448 0.35
22 * 74.406 7.03 1.74320 49.3
23 * -40.669 0.15
24 -75.737 6.50 1.69680 55.5
25 -30.960 38.44 to 45.15
26 (IM) ∞

Aspheric data 5th surface
K = -1.12166E + 00
A4 = 4.89075E-06
A6 = -3.96587E-09
A8 = 2.47445E-11
A10 = -6.08112E-14
A12 = 7.08946E-17

Aspheric data 22nd surface
K = 0.00000E + 00
A4 = -5.15675E-06
A6 = 9.03138E-09
A8 = -1.69741E-11
A10 = 9.37387E-16

Aspheric data 23rd surface
K = -1.38896E + 00
A4 = 6.15995E-06
A6 = -1.84291E-09
A8 = 7.07932E-11
A10 = -4.62572E-13
A12 = 1.30408E-15
A14 = -1.47433E-18

Various data
f = 28.50
FNO. = 1.45
2ω = 75.22
y'max = 21.6
TL = 141.83
BF = 38.44
θgF = 0.6028
f1 = 249.48
f2 = 50.72
f14 = -49.48
f15 = 103.55
f1s = -93.94
f1i = 51.11

DU digital device LU imaging optical device LN imaging lens Gr1 first group Gr2 second group L1 # #th lens from the object side in the first group (# = 1, 2,..., 6; first to sixth lenses)
L2 # #th lens from the object side in the second group (# = 1, 2,..., 8)
LS cemented lens ST stop 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 (12)

In order from the object side, the first group and a second group having positive power,
The first group includes, in order from the object side, a first lens having negative power, a second lens having negative power, a third lens having positive power, a fourth lens having negative power, and positive power. A fifth lens having
The first lens and the second lens have a meniscus shape convex toward the object side;
The fourth lens and the fifth lens constitute a cemented lens,
Focusing on a short-distance object is performed by moving the second group to the object side with the position of the first group fixed.
An imaging lens that satisfies the following conditional expressions (1) to (3):
−0.7 <φ14 / φ <−0.3 (1)
0.1 <φ15 / φ <0.4 (2)
−3 <φ14 / φ15 <−1.5 (3)
However,
φ14: power of the fourth lens,
φ15: power of the fifth lens,
φ: Power of the entire system,
It is.   The imaging lens according to claim 1, wherein the cemented lens including the fourth and fifth lenses has a negative combined power. The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied:
Nd15> 1.8 (4)
However,
Nd15: refractive index of the fifth lens relating to the d-line,
It is.   4. The imaging lens according to claim 1, wherein a lens located closest to the image side in the first group has positive power. 5. The imaging lens according to any one of claims 1 to 4, wherein a lens positioned adjacent to the object side of the diaphragm satisfies the following conditional expression (5):
θgf − (− 0.00162νd + 0.6415) <0.012 (5)
However,
θgf: partial dispersion ratio of the 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 1, wherein the first group has positive power. The imaging lens according to claim 1, wherein the following conditional expression (6) is satisfied:
Nd13> 1.8 (6)
However,
Nd13: the refractive index of the third lens relating to the d-line,
It is.   The imaging lens according to any one of claims 1 to 7, wherein the second group has two or more positive lenses continuously from the object side.   The second group includes, in order from the object side, a positive lens, a positive lens, a positive lens, a negative lens, a diaphragm, a negative lens, a positive lens, a positive lens, and a positive lens. The imaging lens of Claim 1.   The imaging lens according to claim 1, comprising three or more aspheric lenses.   An imaging lens according to any one of claims 1 to 10, 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.   12. A digital apparatus comprising the imaging optical device according to claim 11 to which at least one function of still image shooting and moving image shooting of a subject is added.

Images