WO2016136352A1

WO2016136352A1 - Macro lens and imaging device

Info

Publication number: WO2016136352A1
Application number: PCT/JP2016/051987
Authority: WO
Inventors: 祐美子上原; 文和金高; 久宇野
Original assignee: ソニー株式会社
Priority date: 2015-02-26
Filing date: 2016-01-25
Publication date: 2016-09-01

Abstract

A macro lens according to the present invention comprises: an object side lens group arranged nearest to an object side and having positive refractive power; a first focus lens group, arranged closer to the image plane than the object side lens group and moving from the object side toward the image plane side along the optical axis when focusing from an object at infinity to an object at close range; an aperture stop fixed in the optical axis direction during focusing; a second focus lens group composed of two or more lenses, arranged closer to the image plane than the first focus lens group, and moving from the image plane side toward the object side along the optical axis when focusing from an object at infinity to an object at close range; and a final lens group arranged nearest to the image plane and fixed in the optical axis direction during focusing.

Description

Macro lens and imaging device

The present disclosure relates to a macro lens and an imaging device. Specifically, a macro lens that is suitably used for a single-lens reflex camera, a mirrorless camera, a digital still camera, and the like, has a large maximum shooting magnification, and has been improved in performance, and an imaging apparatus including such a macro lens. About.

With the spread of single-lens reflex cameras, there is an increasing demand for providing lenses compatible with 35 mm version image sensors. In addition, there is a macro lens as a lens that enables shooting from an object at infinity to a short distance object whose shooting magnification is close to the same magnification. In particular, there is a floating optical system that performs focusing by moving a plurality of focus lens groups with different movement amounts, and a macro lens suitable for a single-lens reflex camera or the like has been proposed (for example, see Patent Document 1). In recent years, with the spread of mirrorless cameras, macro lenses suitable for them have also been proposed (see, for example, Patent Document 2 and Patent Document 3).

JP 2010-145830 A JP 2011-048232 A JP 2014-219601 A

From the user, it is possible to provide a lens that has a focal length of about 90 mm in terms of 35 mm as an angle of view suitable for portrait photography and macro photography of flowers, insects, and the like, and can be used for 35 mm version image sensors. Expected. In particular, in the case of corresponding to a 35 mm version image sensor, since the total length and diameter of the lens barrel tend to increase, it is important to realize a smaller size and a lighter weight.

However, in the disclosed example of Patent Document 1, the distance from the top of the lens on the most object side to the image sensor, that is, the optical total length is as large as about 160 mm. Also, in the disclosure example of Patent Document 2, the total optical length is as large as about 160 mm when it corresponds to a 35 mm version image sensor.

Furthermore, in recent years, since digital cameras have both still image and movie shooting functions, in addition to increasing the AF (autofocus) speed during still image shooting, it is possible to enable wobbling during movie shooting. It has been demanded. Here, wobbling means that the lens group is moved minutely in the optical axis direction by using a contrast method in order to detect the in-focus position during AF. In many cases, one lens group functions as both a focus lens group and a wobbling lens group. Here, in the disclosed example of Patent Document 2, since the lens of the focus lens group on the image plane side from the aperture stop tends to have a higher specific gravity, it is not optimal for increasing the AF speed or wobbling.

Further, in the disclosed example of Patent Document 3, the second focus lens group is composed of a single lens, and weight reduction can be realized. On the other hand, a low-dispersion glass aspherical lens is used for the second focus lens group. When the lens is made to correspond to a 35 mm version image sensor, the manufacturing difficulty increases as the lens diameter increases. There are challenges.

Therefore, the development of a lens system that has a focal length of about 90 mm corresponding to a 35 mm version image sensor, is capable of macro photography, has good optical performance, has a short optical total length, and has a reduced focus lens group. Is desired.

Therefore, it is desirable to provide a macro lens capable of reducing the weight of the focus lens group, and an imaging apparatus equipped with such a macro lens, while having good optical performance and a short optical total length.

A macro lens according to an embodiment of the present disclosure is disposed closest to the object side, has an object-side lens group having positive refractive power, and is closer to the image plane side than the object-side lens group, and is close to an object at infinity. A first focus lens group that moves on the optical axis from the object side to the image plane side during focusing on the object, an aperture stop that is fixed in the optical axis direction during focusing, and two or more lenses, and a first focus A second focus lens group that is arranged on the image plane side of the lens group and moves on the optical axis from the image plane side to the object side during focusing from an object at infinity to a short distance object; And a final lens unit that is fixed in the optical axis direction during focusing, and satisfies the following conditional expression.
0.25 <| fr / f | <2.0 (1)
0.65 <y '/ BF <1.3 (2)
However,
fr: focal length of the final lens group f: focal length of the entire system y ′: image height BF: air conversion length of back focus.

An imaging apparatus according to an embodiment of the present disclosure includes a macro lens and an imaging element that outputs an imaging signal corresponding to an optical image formed by the macro lens, and the macro lens is formed by the macro lens according to the present disclosure. It is composed.

In the macro lens or the imaging device according to an embodiment of the present disclosure, the focus lens group and other imaging devices have a good optical performance, the optical total length is short, and the focus lens group can be reduced in weight. The configuration of the lens group is optimized.

According to the macro lens or the imaging device according to the embodiment of the present disclosure, the configuration of the focus lens group and the other lens groups is optimized, so that the optical total length is obtained while having good optical performance. The focus lens group can be reduced in weight.
Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

It is a lens sectional view showing the 1st example of composition of the macro lens concerning one embodiment of this indication. It is an aberration diagram showing various aberrations at infinity in Numerical Example 1 in which specific numerical values are applied to the macro lens shown in FIG. FIG. 6 is an aberration diagram illustrating various aberrations at an intermediate shooting distance in Numerical Example 1 in which specific numerical values are applied to the macro lens illustrated in FIG. 1. It is an aberration diagram showing various aberrations at the same magnification shooting distance in Numerical Example 1 in which specific numerical values are applied to the macro lens shown in FIG. It is lens sectional drawing which shows the 2nd structural example of a macro lens. FIG. 6 is an aberration diagram illustrating various aberrations at infinity in Numerical Example 2 in which specific numerical values are applied to the macro lens illustrated in FIG. 5. FIG. 6 is an aberration diagram illustrating various aberrations at an intermediate shooting distance in Numerical Example 2 in which specific numerical values are applied to the macro lens illustrated in FIG. 5. FIG. 6 is an aberration diagram showing various aberrations at the same magnification shooting distance in Numerical Example 2 in which specific numerical values are applied to the macro lens shown in FIG. 5. It is lens sectional drawing which shows the 3rd structural example of a macro lens. FIG. 10 is an aberration diagram illustrating various aberrations at infinity in Numerical Example 3 in which specific numerical values are applied to the macro lens illustrated in FIG. 9. FIG. 10 is an aberration diagram illustrating various aberrations at an intermediate shooting distance in Numerical Example 3 in which specific numerical values are applied to the macro lens illustrated in FIG. 9. FIG. 10 is an aberration diagram illustrating various aberrations at the same magnification shooting distance in Numerical Example 3 in which specific numerical values are applied to the macro lens illustrated in FIG. 9. It is lens sectional drawing which shows the 4th structural example of a macro lens. FIG. 14 is an aberration diagram showing various aberrations at infinity in Numerical Example 4 in which specific numerical values are applied to the macro lens illustrated in FIG. 13. FIG. 14 is an aberration diagram illustrating various aberrations at an intermediate shooting distance in Numerical Example 4 in which specific numerical values are applied to the macro lens illustrated in FIG. 13. FIG. 14 is an aberration diagram showing various aberrations at the same magnification shooting distance in Numerical Example 4 in which specific numerical values are applied to the macro lens illustrated in FIG. 13. It is a block diagram which shows the example of 1 structure of an imaging device.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.
1. 1. Basic configuration of lens Action and effect 3. Application example to imaging device 4. Numerical example of lens Other embodiments

[1. Basic lens configuration]
FIG. 1 illustrates a first configuration example of a macro lens according to an embodiment of the present disclosure. FIG. 5 shows a second configuration example of the macro lens. FIG. 9 shows a third configuration example of the macro lens. FIG. 13 shows a fourth configuration example of the macro lens. Numerical examples in which specific numerical values are applied to these configuration examples will be described later. In FIG. 1 and the like, Z1 represents an optical axis. Between the macro lens and the image plane IMG, optical members such as a seal glass for protecting the image sensor and various optical filters FL may be disposed.
Hereinafter, the configuration of the macro lens according to the present embodiment will be described in association with the configuration example illustrated in FIG. 1 and the like as appropriate, but the technology according to the present disclosure is not limited to the illustrated configuration example.

The macro lens according to the present embodiment includes an object side lens group disposed closest to the object side, a first focus lens group disposed closer to the image plane than the object side lens group, an aperture stop S, and a first lens. A second focus lens group disposed on the image plane side with respect to the focus lens group, and a final lens group disposed on the most image plane side are provided.

The object side lens group has a positive refractive power and is fixed in the optical axis direction during focusing. The aperture stop S is fixed in the optical axis direction during focusing. In each of the macro lenses 1 to 4 in FIGS. 1, 5, 9, and 13, the first lens group GR1 corresponds to the object side lens group.

The macro lens according to the present embodiment is capable of focusing on an object within a range including an object distance from infinity to a short distance where the photographing magnification is equal magnification by the first focus lens group and the second focus lens group. is there.

In FIG. 1 and the like, the upper row shows the object distance at infinity, the middle row shows the intermediate shooting distance where the shooting magnification is -0.5 times, and the lower row shows the position of the lens group at the same shooting distance where the shooting magnification is the same magnification. Yes. Dashed arrows indicate movement during focusing. The first focus lens group and the second focus lens group exist at positions indicated by broken-line arrows as focusing from infinity to the same magnification photographing distance is performed. A solid arrow indicates a moving direction of an anti-vibration lens group described later.

The first focus lens group moves on the optical axis from the object side to the image plane side during focusing from an infinitely distant object to a close object. The second focus lens group includes two or more lenses, and moves on the optical axis from the image plane side to the object side during focusing from an infinitely distant object to a close object. In each of the macro lenses 1 to 4 in FIGS. 1, 5, 9, and 13, the second lens group GR2 corresponds to the first focus lens group. Further, in each of the macro lenses 1 to 3 of FIGS. 1, 5, and 9, the fourth lens group GR4 corresponds to the second focus lens group. In the macro lens 4 of FIG. 13, the third lens group GR3 corresponds to the second focus lens group.

The final lens group is fixed in the optical axis direction during focusing. In each of the macro lenses 1 to 3 in FIGS. 1, 5, and 9, the fifth lens group GR5 corresponds to the final lens group. In the macro lens 4 of FIG. 13, the fourth lens group GR4 corresponds to the final lens group.

The macro lens according to the present embodiment satisfies the following conditional expression.
0.25 <| fr / f | <2.0 (1)
0.65 <y '/ BF <1.3 (2)
However,
fr: focal length of the final lens group f: focal length of the entire system y ′: image height BF: air conversion length of back focus.

In addition, it is desirable that the macro lens according to the present embodiment satisfies a predetermined conditional expression described later.

[2. Action / Effect]
Next, functions and effects of the macro lens according to the present embodiment will be described. In addition, a desirable configuration of the macro lens according to the present embodiment will be described.
Note that the effects described in the present specification are merely examples and are not limited, and other effects may be obtained.

According to the macro lens according to the present embodiment, by optimizing the configuration of the focus lens group and the other lens groups, macro shooting is possible and the optical total length is short while having good optical performance. The focus lens group can be reduced in weight. Accordingly, it is possible to provide a macro lens having a focal length of about 90 mm corresponding to a 35 mm version image sensor.

In the macro lens according to the present embodiment, when focusing from an object at infinity to a short distance object, the first focus lens group moves on the optical axis from the object side to the image plane side, and the second focus lens group moves to the optical axis. Move up from the image plane side to the object side. Other lens groups are fixed in the optical axis direction. Other than the first and second focus lens groups responsible for the focus function, an inner focus type macro lens whose position is fixed with respect to the image plane IMG is used. Thereby, the movable group can be reduced, and the AF speed can be increased and the power can be saved. Further, in focusing, moving the two lens groups is advantageous in correcting field curvature until shooting from an infinitely distant object to a close object with a photographing magnification near the same magnification.

Further, by fixing the aperture stop S to the image plane IMG at the time of focusing, the weight of the movable group can be reduced, which is effective for increasing the AF speed. In addition, by configuring the second focus lens group with two or more lenses, it is advantageous for correcting axial chromatic aberration and lateral chromatic aberration.

Also, in focusing, by fixing the last lens group closest to the image plane to the image plane IMG, the movable group can be reduced and the mechanical structure can be simplified.

In the macro lens according to the present embodiment, when the conditional expression (1) is satisfied, the power of the final lens group in the optical system becomes strong, which is advantageous for shortening the optical total length. Further, by satisfying the conditional expression (2), the final lens and the image plane IMG can be brought close to each other, which is also advantageous for shortening the total optical length. More specifically, the following actions and effects can be obtained.

Conditional expression (1) is an expression that prescribes the focal length of the final lens unit closest to the image plane in order to shorten the optical total length. When the value falls below the numerical range of conditional expression (1), the power of the final lens group becomes strong and the aberration generated by the peripheral luminous flux increases, so that the optical performance deteriorates. In addition, since the light incident angle on the image sensor approaches parallel to the image capturing surface, shading in the image sensor deteriorates. When the numerical value range of conditional expression (1) is exceeded, the power of the final lens group becomes weak, so that the optical total length becomes long, which is disadvantageous for downsizing of the lens barrel.

In order to further obtain the above effect, it is desirable to set the numerical range of conditional expression (1) to the range of conditional expression (1) ′ below.
0.4 <| fr / f | <1.0 (1) ′

Conditional expression (2) is an expression that defines the relationship between the back focus length and the image height, which are preferable for shortening the optical total length. If the numerical value range of conditional expression (2) is not reached, the back focus becomes long, so that the total optical length becomes long, which is disadvantageous for downsizing the lens barrel. When the conditional expression (2) is exceeded, the optical system is too close to the mechanical structure inside the camera body, and there is a possibility that the optical system and the parts of the camera body interfere with each other.

In order to further obtain the above effect, it is desirable to set the numerical range of conditional expression (2) to the range of conditional expression (2) ′ below.
0.65 <y '/ BF <1.2 (2)'

In order to further enhance the above effect, it is more desirable to set the numerical range to the range of the following conditional expression (2) ″.
0.7 <y '/ BF <1.15 (2)''

In the macro lens according to the present embodiment, it is preferable that the following conditional expression (3) is satisfied.
0 <f / ff <0.8 (3)
However,
ff: The combined focal length of the lens unit on the object side of the second focus lens unit.

Conditional expression (3) is an expression that prescribes the combined focal length of the lens group on the object side of the second focus lens group in order to reduce the weight of the second focus lens group. By satisfying conditional expression (3), the combined refractive power from the object side lens group to the lens group adjacent to the object side of the second focus lens group is optimized, which is advantageous for reducing the weight of the second focus lens group. It becomes. Further, it is advantageous for reducing the outer diameter of the lens barrel. If the numerical value range of conditional expression (3) is not reached, the combined refractive power of the lens group located on the object side of the second focus lens group becomes weak, so that the second focus lens while appropriately converging the light beam It becomes difficult to lead to a group. This increases the diameter of the second focus lens group, increases the weight, and makes it difficult to reduce the AF speed and provide a wobbling function. In addition, the outer diameter of the lens barrel is increased. When the numerical value range of the conditional expression (3) is exceeded, the combined refractive power of the group located closer to the object side than the second focus lens group becomes strong, and thus the occurrence of various aberrations such as field curvature increases. . Furthermore, since the light beam guided to the second focus lens group is not telecentric, fluctuations in aberration due to focusing also increase.

In order to further obtain the above effect, it is desirable to set the numerical range of conditional expression (3) to the range of conditional expression (3) ′ below.
0.3 <f / ff <0.8 (3) '

In order to further enhance the above effect, it is more desirable to set the numerical range within the range of the following conditional expression (3) ″.
0.35 <f / ff <0.7 (3) ''

In the macro lens according to the present embodiment, it is preferable that the following conditional expression (4) is satisfied.
0.24 <1 / GF <0.40 (4)
However,
GF: The average specific gravity of the second focus lens group.

Conditional expression (4) is an expression that regulates the average specific gravity of the second focus lens group in order to reduce the weight of the second focus lens group. When the conditional expression (4) is satisfied, the specific gravity of the lens of the second focus lens group is optimized, which is advantageous for reducing the weight of the second focus lens group, and effective for increasing the AF speed. It is also advantageous for wobbling used for moving image shooting and the like. When the value falls below the numerical range of the conditional expression (4), the second focus lens group becomes heavy, leading to a decrease in AF speed. In addition, it becomes difficult to provide a wobbling function used for moving image shooting or the like. When the numerical value range of conditional expression (4) is exceeded, the refractive index tends to decrease. Therefore, the focus sensitivity of the second focus lens group decreases, and the shooting magnification from the object at infinity is a short distance near the same magnification. The amount of movement in focusing to the object increases. This is disadvantageous for shortening the optical total length.

In order to further obtain the above effect, it is desirable to set the numerical range of conditional expression (4) to the range of conditional expression (4) ′ below.
0.28 <1 / GF <0.40 (4) '

In order to further enhance the above effect, it is more desirable to set the numerical range within the range of the following conditional expression (4) ″.
0.28 <1 / GF <0.32 (4) ''

The macro lens according to the present embodiment may further include an anti-vibration lens group that moves in a direction perpendicular to the optical axis Z1. In each of the macro lenses 1 to 3 in FIGS. 1, 5, and 9, the third lens group GR3 corresponds to an anti-vibration lens group. Further, in the macro lens 4 of FIG. 13, a part of the fourth lens group GR4 corresponds to the anti-vibration lens group.

The anti-vibration lens group moves so as to have a component perpendicular to the optical axis Z1, and shifts the imaging position in the direction perpendicular to the optical axis Z1. The anti-vibration lens group is located on the image plane side with respect to the first focus lens group and on the object side with respect to the second focus lens group, as in the configuration examples of the macro lenses 1 to 3 in FIGS. It is desirable to be arranged in. Thereby, the focus shift | offset | difference which generate | occur | produces at the time of vibration isolation can be reduced. In particular, when photographing at a long distance, since the telecentric axial light beam passes through the anti-vibration lens group, fluctuations in on-axis performance during anti-vibration can be suppressed.

When the anti-vibration lens group is disposed closer to the image plane than the first focus lens group and closer to the object side than the second focus lens group, it is desirable that the anti-vibration lens group has a positive refractive power. Accordingly, since the light flux is converged and guided to the second focus lens group, the height of the light flux can be lowered, which is advantageous for reducing the diameter of the second focus lens group.

Further, as in the configuration example of the macro lens 4 in FIG. 13, a part of the lenses in the final lens group can be set as a vibration-proof lens group. In this case, it is desirable that the image stabilizing lens group has a negative refractive power. In this case, since vibration isolation is possible at a position farther from the aperture stop S, the axial light beam and the peripheral light beam are guided to the final lens group in a state of being separated from each other. Thereby, in the final lens group, aberration correction can be performed separately for the axial light beam and the peripheral light beam, and deterioration of the peripheral performance at the time of image stabilization can be suppressed.

In the macro lens according to the present embodiment, it is desirable that at least one lens surface of the plurality of lens surfaces constituting the object side lens group is aspherical. Since the object side lens group has a high light beam height at all photographing magnifications, it is possible to always correct the aberration of the peripheral luminous flux and to guide the luminous flux with little residual aberration to the first focus lens group.

Further, it is desirable that the final lens group includes at least one negative lens and one positive lens. Since the negative lens can diverge the light beam with a small aperture, the back focus can be shortened and the entire optical system can be downsized. Further, chromatic aberration can be corrected well by combining a negative lens and a positive lens.

In addition, it is desirable that the most image side surface of the final lens group is a convex surface. Thereby, generation | occurrence | production of a ghost can be suppressed.

[3. Application example to imaging device]
FIG. 17 shows a configuration example of the imaging apparatus 100 to which the macro lens according to the present embodiment is applied. The imaging device 100 is, for example, a digital still camera, and includes a camera block 10, a camera signal processing unit 20, an image processing unit 30, an LCD (Liquid Crystal Display) 40, and an R / W (reader / writer) 50. , A CPU (Central Processing Unit) 60, an input unit 70, and a lens drive control unit 80.

The camera block 10 is responsible for an imaging function, and includes an optical system including an imaging lens 11 and an imaging device 12 such as a CCD (Charge-Coupled Devices) or a CMOS (Complementary Metal-Oxide Semiconductor). The imaging element 12 outputs an imaging signal (image signal) corresponding to the optical image by converting the optical image formed by the imaging lens 11 into an electrical signal. As the imaging lens 11, the macro lenses 1 to 4 of the respective configuration examples shown in FIGS. 1, 5, 9, and 13 can be applied.

The camera signal processing unit 20 performs various signal processing such as analog-digital conversion, noise removal, image quality correction, and conversion to luminance / color difference signals on the image signal output from the image sensor 12.

The image processing unit 30 performs recording and reproduction processing of an image signal, and performs compression encoding / decompression decoding processing of an image signal based on a predetermined image data format, conversion processing of data specifications such as resolution, and the like. It has become.

The LCD 40 has a function of displaying various data such as an operation state of the user input unit 70 and a photographed image. The R / W 50 performs writing of the image data encoded by the image processing unit 30 to the memory card 1000 and reading of the image data recorded on the memory card 1000. The memory card 1000 is a semiconductor memory that can be attached to and detached from a slot connected to the R / W 50, for example.

The CPU 60 functions as a control processing unit that controls each circuit block provided in the imaging apparatus 100, and controls each circuit block based on an instruction input signal or the like from the input unit 70. The input unit 70 includes various switches and the like that are operated by a user. The input unit 70 includes, for example, a shutter release button for performing a shutter operation, a selection switch for selecting an operation mode, and the like, and outputs an instruction input signal corresponding to an operation by the user to the CPU 60. ing. The lens drive control unit 80 controls driving of the lenses arranged in the camera block 10 and controls a motor (not shown) that drives each lens of the imaging lens 11 based on a control signal from the CPU 60. It has become.

Although illustration is omitted, the imaging apparatus 100 includes a shake detection unit that detects a shake of the apparatus due to a camera shake.

Hereinafter, an operation in the imaging apparatus 100 will be described.
In a shooting standby state, under the control of the CPU 60, an image signal shot by the camera block 10 is output to the LCD 40 via the camera signal processing unit 20 and displayed as a camera through image. Further, for example, when an instruction input signal for focusing is input from the input unit 70, the CPU 60 outputs a control signal to the lens drive control unit 80, and a predetermined value of the imaging lens 11 is controlled based on the control of the lens drive control unit 80. The lens moves.

When a shutter (not shown) of the camera block 10 is operated by an instruction input signal from the input unit 70, the captured image signal is output from the camera signal processing unit 20 to the image processing unit 30 and subjected to compression encoding processing. Converted to digital data in data format. The converted data is output to the R / W 50 and written to the memory card 1000.

Note that focusing is performed by the lens drive control unit 80 based on a control signal from the CPU 60, for example, when the shutter release button of the input unit 70 is half-pressed or when it is fully pressed for recording (photographing). This is performed by moving a predetermined lens of the imaging lens 11.

When reproducing the image data recorded on the memory card 1000, predetermined image data is read from the memory card 1000 by the R / W 50 in response to an operation on the input unit 70, and decompressed and decoded by the image processing unit 30. After the processing is performed, the reproduction image signal is output to the LCD 40 and the reproduction image is displayed.

Further, the CPU 60 operates the lens drive control unit 80 based on a signal output from a shake detection unit (not shown), and moves the image stabilizing lens group in a direction substantially perpendicular to the optical axis Z1 according to the shake amount.

In the above-described embodiment, an example in which the imaging device is applied to a digital still camera has been described. However, the application range of the imaging device is not limited to a digital still camera, and can be applied to other various imaging devices. It is. For example, it can be applied to a single-lens reflex camera, a mirrorless camera, and a digital video camera. Further, it can be widely applied as a camera unit of a digital input / output device such as a mobile phone with a camera incorporated therein or a PDA (Personal Digital Assistant) with a camera incorporated therein. The present invention can also be applied to an interchangeable lens camera.

<4. Numerical Examples of Lens>
Next, specific numerical examples of the macro lens according to the present embodiment will be described. Here, numerical examples in which specific numerical values are applied to the macro lenses 1 to 4 of the respective configuration examples shown in FIGS. 1, 5, 9 and 13 will be described.

The meanings of symbols shown in the following tables and explanations are as shown below. “Surface number” indicates the number of the i-th surface counted from the object side to the image side. “Ri” indicates the value (mm) of the paraxial radius of curvature of the i-th surface. “Di” indicates a value (mm) of an interval on the optical axis between the i-th surface and the (i + 1) -th surface. “Ni” indicates the value of the refractive index at the d-line (wavelength 587.6 nm) of the material of the optical element having the i-th surface. “Νi” represents the value of the Abbe number in the d-line of the material of the optical element having the i-th surface. The portion where the value of “ri” is “∞” indicates a flat surface or a diaphragm surface (aperture stop S). The surface indicated as “STO” in “surface number” indicates the aperture stop S. “F” indicates the focal length of the entire lens system, “Fno” indicates the F number, and “ω” indicates the half angle of view.

Some lenses used in each numerical example have an aspheric lens surface. In the “surface number”, the surface marked with * is an aspherical surface. The aspheric shape is defined by the following aspheric expression. In each table showing aspherical coefficients described later, “E−i” represents an exponential expression with a base of 10, that is, “10 ⁻ⁱ ”. For example, “0.12345E-05” represents “ 0.12345 × 10 ⁻⁵ ”.

(Aspherical formula)
x = cy ² / [1+ {1− (1 + κ) c ² y ² } ^1/2 ] + Ay ⁴ + By ⁶ + Cy ⁸ + Dy ¹⁰

here,
x: Sag amount (distance in the optical axis direction from the apex of the lens surface)
y: Height in the direction perpendicular to the optical axis c: Paraxial curvature at the lens apex (reciprocal of paraxial radius of curvature)
κ: conic constant A: fourth-order aspheric coefficient B: sixth-order aspheric coefficient C: eighth-order aspheric coefficient D: tenth-order aspheric coefficient

[Numerical Example 1]
Table 1 shows lens data of Numerical Example 1 in which specific numerical values are applied to the macro lens 1 shown in FIG.

The macro lens 1 shown in FIG. 1 includes a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, A fourth lens group GR4 having negative refractive power and a fifth lens group GR5 having negative refractive power are arranged in order from the object side to the image plane side.

The macro lens 1 satisfies the basic configuration of the lens described in the above embodiment, and the first lens group GR1 corresponds to an object side lens group. The second lens group GR2 corresponds to the first focus lens group, and the fourth lens group GR4 corresponds to the second focus lens group. The fifth lens group GR5 corresponds to the final lens group. The third lens group GR3 corresponds to an anti-vibration lens group.

The first lens group GR1 includes a biconvex positive lens G1, a cemented lens in which a biconvex positive lens G2 and a biconcave negative lens G3 are cemented, and a meniscus shape with a convex surface facing the object side. A positive lens G4 is arranged in order from the object side to the image plane side.

The second lens group GR2 includes a biconcave negative lens G5, a cemented lens formed by cementing a biconcave negative lens G6 and a meniscus positive lens G7 having a convex surface facing the object side, from the object side. They are arranged in order toward the image plane side.

The third lens group GR3 is constituted by a cemented lens in which a meniscus negative lens G8 having a convex surface directed toward the object side and a biconvex positive lens G9 are cemented.

The fourth lens group GR4 includes, from the object side, a biconvex positive lens G11, a biconvex positive lens G12, and a meniscus negative lens G12 having a concave surface facing the object side. They are arranged in order toward the image plane side.

In the fifth lens group GR5, a meniscus positive lens G13 having a concave surface facing the object side, a biconcave negative lens G14, and a meniscus negative lens G15 having a concave surface facing the object side are arranged from the object side. They are arranged in order toward the image plane side.

An optical filter FL is disposed between the fifth lens group GR5 and the image plane IMG. The aperture stop S is disposed on the object side of the third lens group GR3.

In the macro lens 1, aspherical surfaces are formed on the seventh surface and the nineteenth surface. The values of the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D along with the values of the conic constant κ are shown in [Table 2].

[Table 3] shows the focal length f, F number Fno, and half angle of view ω of the entire lens system. In the macro lens 1, the distance d <b> 7 between the first lens group GR <b> 1 and the second lens group GR <b> 2 changes during focusing from infinity to the equal magnification shooting distance. Further, the distance d12 between the second lens group GR2 and the third lens group GR3 changes. Further, the distance d16 between the aperture stop S and the fourth lens group GR4 changes. Further, the distance d21 between the fourth lens group GR4 and the fifth lens group GR5 changes. Table 4 shows the values of the variable intervals at infinity, intermediate shooting distance (shooting magnification -0.5 times), and equal magnification shooting distance (shooting magnification -1.0 times).

2 to 4 show various aberrations in Numerical Example 1. FIG. 2 shows various aberrations at infinity, FIG. 3 shows an intermediate shooting distance, and FIG. 2 to 4 show spherical aberration, astigmatism (field curvature), and distortion (distortion aberration) as various aberrations. In the aberration diagram of field curvature, a solid line (S) indicates a value on a sagittal image plane, and a broken line (M) indicates a value on a meridional image plane. The same applies to aberration diagrams in other numerical examples.

As can be seen from each aberration diagram, the macro lens 1 according to Numerical Example 1 has excellent imaging performance in which each aberration is well corrected at infinity, intermediate shooting distance, and equal shooting distance. It is clear that

[Numerical Example 2]
Table 5 shows lens data of Numerical Example 2 in which specific numerical values are applied to the macro lens 2 shown in FIG.

The macro lens 2 shown in FIG. 5 includes a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, A fourth lens group GR4 having negative refractive power and a fifth lens group GR5 having negative refractive power are arranged in order from the object side to the image plane side.

The macro lens 2 satisfies the basic configuration of the lens described in the above embodiment, and the first lens group GR1 corresponds to an object side lens group. The second lens group GR2 corresponds to the first focus lens group, and the fourth lens group GR4 corresponds to the second focus lens group. The fifth lens group GR5 corresponds to the final lens group. The third lens group GR3 corresponds to an anti-vibration lens group.

In the macro lens 2, an aspheric surface is formed on the seventh surface. The values of the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D on the aspheric surface are shown in [Table 6] together with the value of the conic constant κ.

[Table 7] shows the focal length f, F number Fno, and half angle of view ω of the entire lens system. In the macro lens 2, the distance d7 between the first lens group GR1 and the second lens group GR2 changes during focusing from infinity to the equal magnification shooting distance. Further, the distance d12 between the second lens group GR2 and the third lens group GR3 changes. Further, the distance d16 between the aperture stop S and the fourth lens group GR4 changes. Further, the distance d21 between the fourth lens group GR4 and the fifth lens group GR5 changes. Table 8 shows the values of variable intervals at infinity, intermediate shooting distance (shooting magnification -0.5 times), and equal magnification shooting distance (shooting magnification -1.0 times).

6 to 8 show various aberrations in Numerical Example 2. FIG. 6 shows various aberrations at infinity, FIG. 7 shows an intermediate shooting distance, and FIG. 8 shows an equal magnification shooting distance.

As can be seen from each aberration diagram, the macro lens 2 according to Numerical Example 2 has excellent imaging performance in which each aberration is well corrected at infinity, an intermediate shooting distance, and an equal magnification shooting distance. It is clear that

[Numerical Example 3]
Table 9 shows lens data of Numerical Example 3 in which specific numerical values are applied to the macro lens 3 shown in FIG.

The macro lens 3 shown in FIG. 9 includes a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, A fourth lens group GR4 having negative refractive power and a fifth lens group GR5 having negative refractive power are arranged in order from the object side to the image plane side.

The macro lens 3 satisfies the basic configuration of the lens described in the above embodiment, and the first lens group GR1 corresponds to an object side lens group. The second lens group GR2 corresponds to the first focus lens group, and the fourth lens group GR4 corresponds to the second focus lens group. The fifth lens group GR5 corresponds to the final lens group. The third lens group GR3 corresponds to an anti-vibration lens group.

The first lens group GR1 includes a biconvex positive lens G1, a cemented lens in which a biconvex positive lens G2 and a biconcave negative lens G3 are cemented, and a biconvex positive lens G4. They are arranged in order from the object side to the image plane side.

In the second lens group GR2, a biconcave negative lens G5 and a cemented lens formed by cementing a biconcave negative lens G6 and a biconvex positive lens G7 are arranged in order from the object side to the image plane side. Has been configured.

The third lens group GR3 includes a biconvex positive lens G8 and a meniscus negative lens G9 having a concave surface facing the object side, which are arranged in order from the object side to the image surface side.

The fourth lens group GR4 is composed of a cemented lens in which a meniscus negative lens G10 having a convex surface directed toward the object side and a biconvex positive lens G11 are cemented.

The fifth lens group GR5 includes a cemented lens in which a meniscus positive lens G12 having a concave surface facing the object side and a biconcave negative lens G13 are cemented, and a meniscus negative lens G14 having a concave surface facing the object side. Are arranged in order from the object side to the image plane side.

In the macro lens 3, aspheric surfaces are formed on the sixth surface, the eighth surface, and the twentieth surface. The values of the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D along with the values of the conic constant κ are shown in [Table 10].

[Table 11] shows values of the focal length f, the F number Fno, and the half angle of view ω of the entire lens system. In the macro lens 3, the distance d7 between the first lens group GR1 and the second lens group GR2 changes during focusing from infinity to the equal magnification shooting distance. Further, the distance d12 between the second lens group GR2 and the third lens group GR3 changes. Further, the distance d17 between the aperture stop S and the fourth lens group GR4 changes. Further, the distance d20 between the fourth lens group GR4 and the fifth lens group GR5 changes. Table 12 shows the values of the variable intervals at infinity, intermediate shooting distance (shooting magnification -0.5 times), and equal magnification shooting distance (shooting magnification -1.0 times).

10 to 12 show various aberrations in Numerical Example 3. FIG. FIG. 10 shows various aberrations at infinity, FIG. 11 shows an intermediate shooting distance, and FIG.

As can be seen from each aberration diagram, the macro lens 3 according to Numerical Example 3 has excellent imaging performance with each aberration being corrected well at infinity, an intermediate shooting distance, and an equal magnification shooting distance. It is clear that

[Numerical Example 4]
Table 13 shows lens data of Numerical Example 4 in which specific numerical values are applied to the macro lens 4 shown in FIG.

The macro lens 4 shown in FIG. 13 includes a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, and a negative lens power. The fourth lens group GR4 having a refractive power of 1 is arranged in order from the object side to the image plane side.

The macro lens 4 satisfies the basic configuration of the lens described in the above embodiment, and the first lens group GR1 corresponds to an object side lens group. The second lens group GR2 corresponds to the first focus lens group, and the third lens group GR3 corresponds to the second focus lens group. The fourth lens group GR4 corresponds to the final lens group. Part of the lenses G11 and G12 of the fourth lens group GR4 corresponds to a vibration-proof lens group.

The first lens group GR1 includes a biconvex positive lens G1, a biconvex positive lens G2, a meniscus negative lens G3 having a concave surface facing the object side, and a convex surface facing the object side. Are arranged in order from the object side to the image side.

The second lens group GR2 includes a meniscus negative lens G5 having a convex surface facing the object side, and a cemented lens formed by cementing a biconcave negative lens G6 and a biconvex positive lens G7 from the object side. They are arranged in order toward the image side.

The third lens group GR3 includes, from the object side, a biconvex positive lens G8, a cemented lens formed by cementing a meniscus negative lens G9 having a convex surface facing the object side, and a biconvex positive lens G10. They are arranged in order toward the image side.

The fourth lens group GR4 includes a cemented lens in which a biconvex positive lens G11 and a biconcave negative lens G12 are cemented, a meniscus positive lens G13 having a convex surface on the object side, and a concave surface on the object side. Is arranged in order from the object side to the image side.

An optical filter FL is disposed between the fourth lens group GR4 and the image plane IMG. The aperture stop S is disposed between the second lens group GR2 and the third lens group GR3.

[Table 14] shows the focal length f, F number Fno, and half angle of view ω of the entire lens system. In the macro lens 4, the distance d7 between the first lens group GR1 and the second lens group GR2 changes during focusing from infinity to the equal magnification shooting distance. Further, the distance d12 between the second lens group GR2 and the aperture stop S changes. Further, the distance d13 between the aperture stop S and the third lens group GR3 changes. Further, the distance d18 between the third lens group GR3 and the fourth lens group GR4 changes. Table 15 shows the values of the variable intervals at infinity, intermediate shooting distance (shooting magnification -0.5 times), and equal magnification shooting distance (shooting magnification -1.0 times).

14 to 16 show various aberrations in Numerical Example 4. FIG. FIG. 14 shows various aberrations at infinity, FIG. 15 shows an intermediate shooting distance, and FIG.

As can be seen from each aberration diagram, the macro lens 4 according to Numerical Example 4 has excellent imaging performance in which each aberration is well corrected at infinity, intermediate shooting distance, and equal shooting distance. It is clear that

[Other numerical data of each example]
[Table 16] shows a summary of values relating to the above-described conditional expressions for each numerical example. As can be seen from [Table 16], with respect to the basic conditional expressions (1) to (4), the values of the numerical examples are within the numerical range.

<5. Other Embodiments>
The technology according to the present disclosure is not limited to the description of the above-described embodiments and examples, and various modifications can be made.
For example, the shapes and numerical values of the respective parts shown in the numerical examples are merely examples of embodiments for carrying out the present technology, and the technical scope of the present technology is interpreted in a limited manner by these. There should be no such thing.

In the above-described embodiments and examples, the configuration including substantially five or four lens groups has been described. However, a configuration further including a lens having substantially no refractive power may be used.

For example, this technique can take the following composition.
[1]
An object side lens group that is disposed closest to the object side and has a positive refractive power;
A first focus lens group that is closer to the image plane than the object side lens group and moves on the optical axis from the object side to the image plane side during focusing from an object at infinity to a near distance object;
An aperture stop fixed in the optical axis direction during focusing;
Consists of two or more lenses, arranged closer to the image plane than the first focus lens group, and moves from the image plane side to the object side on the optical axis when focusing from an object at infinity to a near object. A second focus lens group,
A final lens group that is arranged closest to the image plane and fixed in the optical axis direction during focusing,
A macro lens that satisfies the following conditional expression.
0.25 <| fr / f | <2.0 (1)
0.65 <y '/ BF <1.3 (2)
However,
fr: focal length of the last lens group f: focal length of the entire system y ′: image height BF: air conversion length of back focus.
[2]
The macro lens according to [1], further satisfying the following conditional expression:
0 <f / ff <0.8 (3)
However,
ff: The combined focal length of the lens unit on the object side of the second focus lens unit.
[3]
The macro lens according to [1] or [2], further satisfying the following conditional expression:
0.24 <1 / GF <0.40 (4)
However,
GF: The average specific gravity of the second focus lens group.
[4]
The macro lens according to any one of [1] to [3], further including a vibration-proof lens group that moves in a direction perpendicular to the optical axis.
[5]
The anti-vibration lens group includes:
The macro lens according to [4], wherein the macro lens is disposed closer to the image plane than the first focus lens group and closer to the object side than the second focus lens group.
[6]
The macro lens according to [4] or [5], wherein the vibration-proof lens group has a positive refractive power.
[7]
The macro lens according to any one of [1] to [3], wherein a part of the lenses in the final lens group is an anti-vibration lens group that moves in a direction perpendicular to the optical axis.
[8]
The macro lens according to [7], wherein the anti-vibration lens group has negative refractive power.
[9]
Focusing on an object within a range including an object distance from an infinite distance to a close distance where the photographing magnification is equal to the magnification is performed by the first focus lens group and the second focus lens group. The macro lens according to any one of the above.
[10]
The macro lens according to any one of [1] to [9], further including a lens having substantially no refractive power.
[11]
A macro lens, and an image sensor that outputs an image signal corresponding to an optical image formed by the macro lens,
The macro lens is
An object side lens group that is disposed closest to the object side and has a positive refractive power;
A first focus lens group that is closer to the image plane than the object side lens group and moves on the optical axis from the object side to the image plane side during focusing from an object at infinity to a near distance object;
An aperture stop fixed in the optical axis direction during focusing;
Consists of two or more lenses, arranged closer to the image plane than the first focus lens group, and moves from the image plane side to the object side on the optical axis when focusing from an object at infinity to a near object. A second focus lens group,
A final lens group that is arranged closest to the image plane and fixed in the optical axis direction during focusing,
An imaging apparatus that satisfies the following conditional expression.
0.25 <| fr / f | <2.0 (1)
0.65 <y '/ BF <1.3 (2)
However,
fr: focal length of the last lens group f: focal length of the entire system y ′: image height BF: air conversion length of back focus.
[12]
The imaging device according to [11], wherein the macro lens further includes a lens having substantially no refractive power.

This application claims priority on the basis of Japanese Patent Application No. 2015-036470 filed on February 26, 2015 at the Japan Patent Office. The entire contents of this application are incorporated herein by reference. This is incorporated into the application.

Those skilled in the art will envision various modifications, combinations, subcombinations, and changes, depending on design requirements and other factors, which are within the scope of the appended claims and their equivalents. It is understood that

Claims

An object side lens group that is disposed closest to the object side and has a positive refractive power;
A first focus lens group that is closer to the image plane than the object side lens group and moves on the optical axis from the object side to the image plane side during focusing from an object at infinity to a near distance object;
An aperture stop fixed in the optical axis direction during focusing;
Consists of two or more lenses, arranged closer to the image plane than the first focus lens group, and moves from the image plane side to the object side on the optical axis when focusing from an object at infinity to a near object. A second focus lens group,
A final lens group that is arranged closest to the image plane and fixed in the optical axis direction during focusing,
A macro lens that satisfies the following conditional expression.
0.25 <| fr / f | <2.0 (1)
0.65 <y '/ BF <1.3 (2)
However,
fr: focal length of the last lens group f: focal length of the entire system y ′: image height BF: air conversion length of back focus.
The macro lens according to claim 1, further satisfying the following conditional expression.
0 <f / ff <0.8 (3)
However,
ff: The combined focal length of the lens unit on the object side of the second focus lens unit.
The macro lens according to claim 1, further satisfying the following conditional expression.
0.24 <1 / GF <0.40 (4)
However,
GF: The average specific gravity of the second focus lens group.
The macro lens according to claim 1, further comprising an anti-vibration lens group that moves in a direction perpendicular to the optical axis.
The anti-vibration lens group includes:
The macro lens according to claim 4, wherein the macro lens is disposed closer to the image plane than the first focus lens group and closer to the object side than the second focus lens group.
The macro lens according to claim 5, wherein the vibration-proof lens group has a positive refractive power.
The macro lens according to claim 1, wherein some lenses in the final lens group are anti-vibration lens groups that move in a direction perpendicular to the optical axis.
The macro lens according to claim 7, wherein the anti-vibration lens group has negative refractive power.
2. The macro lens according to claim 1, wherein focusing is performed on an object within a range including an object distance from an infinite distance to a short distance at which the photographing magnification is equal to magnification by the first focus lens group and the second focus lens group.
A macro lens, and an image sensor that outputs an image signal corresponding to an optical image formed by the macro lens,
The macro lens is
An object side lens group that is disposed closest to the object side and has a positive refractive power;
A first focus lens group that is closer to the image plane than the object side lens group and moves on the optical axis from the object side to the image plane side during focusing from an object at infinity to a near distance object;
An aperture stop fixed in the optical axis direction during focusing;
Consists of two or more lenses, arranged closer to the image plane than the first focus lens group, and moves from the image plane side to the object side on the optical axis when focusing from an object at infinity to a near object. A second focus lens group,
A final lens group that is arranged closest to the image plane and fixed in the optical axis direction during focusing,
An imaging apparatus that satisfies the following conditional expression.
0.25 <| fr / f | <2.0 (1)
0.65 <y '/ BF <1.3 (2)
However,
fr: focal length of the last lens group f: focal length of the entire system y ′: image height BF: air conversion length of back focus.