JP2015041012A - Inner focus lens and image capturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact wide-angle inner focus lens which is compatible with 35-mm film format image sensors and offers high imaging performance, and to provide an image capturing device having the same.SOLUTION: An inner focus lens comprises a first lens group Ghaving positive refractive power, a second lens group Ghaving negative refractive power, and a third lens group Ghaving positive refractive power arranged in order from the object side. The first lens group Gand the third lens group Gare stationary on an optical axis. The second lens group Gshifts focus from being focused on an object at infinity to being focused on an object at a closest distance by moving from the object side to the image side along the optical axis. A compact wide-angle inner focus lens which is compatible with 35-mm film format image sensors and offers high imaging performance is realized by satisfying predetermined conditions.

Description

  The present invention relates to an inner focus lens and an image pickup apparatus that are small and light and suitable for moving image shooting.

  With conventional single-focus lenses, a positive lens group can be placed behind the optical system to ensure back focus so that a long flange back with respect to the focal length can be secured, especially for single-lens reflex cameras. Many have adopted a configuration that makes it easier. However, in recent years, there has been an increase in cases where it is not necessary to ensure a long flange back due to the progress of miniaturization of camera bodies and the spread of digital cameras.

  Since digital cameras can also shoot moving images, high-speed autofocus processing that supports moving image shooting is also desired for digital cameras. In autofocus, first, a part of lens groups (focus group) are vibrated at high speed in the optical axis direction (wobbling) to create a non-focus state → a focus state → a non-focus state. Then, a signal component in a specific frequency band in a partial image region is detected from the output signal of the image sensor, the optimum position of the focus group that is in focus is obtained, and the focus group is moved to the optimum position. In particular, in moving image shooting, it is required to continuously repeat these series of operations at a high speed.

  When wobbling is introduced, the size of the image corresponding to the subject changes during wobbling. This is mainly due to the change in the focal length of the entire optical system due to the movement of the focus group in the optical axis direction, and when the change in photographing magnification due to wobbling is large, a sense of incongruity will be caused. . In order to reduce this uncomfortable feeling, it is known that focusing may be performed with a lens group behind the diaphragm. In particular, in order to perform wobbling, the focus group is required to be as small and light as possible so that the focus group can be driven at high speed.

  Therefore, in order to satisfy such a requirement, an inner focus type lens in which the focus group is reduced in size and weight has been proposed (see, for example, Patent Documents 1 to 3).

JP 2012-159613 A Japanese Patent Application Laid-Open No. 2012-242689 JP 2012-242690 A

  However, the inner focus type lens described in each of the above patent documents is compatible with a small-sized image sensor (APS-C size image sensor, etc.) although the focus group is reduced in size and weight. . For this reason, when the inner focus type lens described in each of the above patent documents is used in a camera equipped with a 35 mm film type image pickup device, vignetting occurs and a high-quality image cannot be obtained.

  An object of the present invention is to provide a small, wide-angle inner focus lens that can be applied to a 35 mm film type image pickup device and has high imaging performance in order to solve the above-described problems caused by the prior art. . It is another object of the present invention to provide a small inner focus lens in which a change in photographing magnification due to wobbling of a focus group is suppressed. Furthermore, it aims at providing the imaging device carrying such an inner focus type | mold lens.

In order to solve the above-described problems and achieve the object, an inner focus type lens according to the present invention includes a first lens group having a positive refractive power and a first lens group having a negative refractive power arranged in order from the object side. The second lens group is composed of one element, and the first lens group and the third lens group are optical axes. Focusing from the infinite object focusing state to the closest object focusing state is performed by moving the second lens group from the object side to the image plane side along the optical axis. The conditional expression shown is satisfied.
(1) 0.13 ≦ L1 / L ≦ 0.43
(2) 0.47 ≦ tan ω ≦ 0.74
Where L1 is the distance from the most object side lens surface vertex to the most image side lens surface vertex in the first lens group, and L is the most object side lens surface vertex in the first lens group and the most in the third lens group. The distance to the apex of the image surface side lens surface, ω, represents a half angle of view in the infinite object focusing state.

  According to the present invention, it is possible to provide a small, wide-angle inner focus lens that can be applied to a 35 mm film type image pickup device and has high imaging performance.

Furthermore, the inner focus type lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(3) 0.34 ≦ β3 ≦ 0.94
Here, β3 represents the imaging magnification of the third lens group in the infinite object focusing state.

  According to the present invention, the inner focus lens of the present invention can be further miniaturized.

Furthermore, the inner focus type lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(4) -1.91 ≦ f2 / f ≦ −0.57
Here, f2 represents the focal length of the second lens group, and f represents the focal length of the entire optical system.

  According to the present invention, by suppressing the amount of movement of the focus group during focusing, it is possible to suppress a change in photographing magnification due to wobbling of the focus group and to further reduce the size of the optical system.

Furthermore, the inner focus type lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(5) 1.95 ≦ ra2 / rb2 ≦ 10.22
Here, ra2 represents the radius of curvature of the most object side surface of the second lens group, and rb2 represents the radius of curvature of the most image side surface of the second lens group.

  According to the present invention, by suppressing the amount of movement of the focus group during focusing, it is possible to suppress a change in photographing magnification due to wobbling of the focus group and to further reduce the size of the optical system.

Furthermore, the inner focus type lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(6) -1.96 ≦ r1 / f ≦ −0.38
Here, f represents the focal length of the entire optical system, and r1 represents the radius of curvature of the outermost object side surface of the first lens group.

  According to the present invention, it is possible to reduce the aperture of the optical system and improve the imaging performance.

  The image pickup apparatus according to the present invention includes the inner focus lens and an image sensor that converts an optical image formed by the inner focus lens into an electrical signal.

  According to the present invention, it is possible to provide an imaging apparatus equipped with the inner focus lens.

  According to the present invention, it is possible to provide a small and wide-angle inner focus lens that can be applied to a 35 mm film type imaging device and has high imaging performance. In addition, there is an effect that it is possible to provide a small inner focus lens in which a change in photographing magnification due to wobbling of the focus group is suppressed. Furthermore, there is an effect that an imaging apparatus equipped with the inner focus lens can be provided.

It is a figure which shows one Embodiment of the imaging device concerning this invention. 1 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 1. FIG. FIG. 6 is a diagram illustrating various aberrations of the inner focus lens according to Example 1 in a state where an object at infinity is in focus. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to Example 2. FIG. 10 is a diagram illustrating various aberrations of the inner focus lens according to Example 2 in an infinite object focusing state. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 3; FIG. 10 is a diagram illustrating various aberrations of the inner focus lens according to Example 3 in a state where an object at infinity is in focus. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 4; FIG. 10 is a diagram illustrating various aberrations of the inner focus lens according to Example 4 in the state of focusing on an object at infinity. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 5; FIG. 10 is a diagram illustrating various aberrations of the inner focus lens according to Example 5 in an infinite object focusing state.

  Hereinafter, preferred embodiments of an inner focus lens and an imaging apparatus according to the present invention will be described in detail.

  The inner focus type lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the object side. And a lens group. In this inner focus type lens, the first lens group and the third lens group are fixed on the optical axis. Then, by moving the second lens group from the object side to the image plane side along the optical axis, focusing from the infinite object focusing state to the closest object focusing state is performed. The second lens group, which is the focus group, is preferably composed of a single element (lens) in order to reduce size and weight.

  Furthermore, in the present invention, in order to realize a small and wide-angle inner focus lens that can be applied to a 35 mm film type image pickup device and has high imaging performance, in addition to the above features, various conditions as shown below are used. It is set.

First, in the inner focus type lens according to the present invention, the distance from the most object side lens surface vertex to the most image side lens surface vertex in the first lens group is L1, and the distance from the most object side lens surface vertex in the first lens group is the first. It is preferable that the following conditional expression is satisfied, where L is the distance to the apex of the most image surface side lens surface in the three lens groups and ω is the half field angle in the infinite object focusing state.
(1) 0.13 ≦ L1 / L ≦ 0.43
(2) 0.47 ≦ tan ω ≦ 0.74

  Conditional expression (1) shows conditions for reducing the size of the optical system and improving the imaging performance. By satisfying conditional expression (1), the length of the first lens group relative to the length from the first lens group to the third lens group is appropriately set to shorten the overall length of the optical system and achieve high image formation. Performance can be obtained.

  If the lower limit of conditional expression (1) is not reached, distortion and spherical aberration are remarkably generated and correction thereof becomes difficult, and imaging performance deteriorates. On the other hand, if the upper limit in conditional expression (1) is exceeded, the total length of the optical system is extended, and it becomes impossible to realize downsizing of the optical system.

In addition, the said conditional expression (1) can anticipate a more preferable effect, if the range shown next is satisfied.
(1a) 0.16 ≦ L1 / L ≦ 0.38
By satisfying the range defined by the conditional expression (1a), it is possible to realize an inner focus type lens that is small in size and has superior imaging performance.

Furthermore, when the conditional expression (1a) satisfies the following range, a smaller and higher performance inner focus lens can be realized.
(1b) 0.19 ≦ L1 / L ≦ 0.33

  Conditional expression (2) represents a condition for realizing an inner focus type lens having a wide angle and high imaging performance that can be applied to a 35 mm film type image pickup device. If the lower limit of conditional expression (2) is not reached, it becomes impossible to obtain an angle of view compatible with a 35 mm film type image pickup device. On the other hand, exceeding the upper limit in conditional expression (2) is preferable for widening the angle, but it becomes difficult to correct various aberrations.

Furthermore, in the inner focus type lens according to the present invention, it is preferable that the following conditional expression is satisfied when the imaging magnification of the third lens group in an infinitely focused object state is β3.
(3) 0.34 ≦ β3 ≦ 0.94

  Conditional expression (3) shows conditions for achieving miniaturization of the optical system. By satisfying conditional expression (3), it is possible to appropriately set the imaging magnification of the third lens group in the state of focusing on an object at infinity and to shorten the entire length of the optical system. In addition, the imaging performance is not deteriorated.

  If the lower limit of conditional expression (3) is not reached, the combined focal length of the first lens group and the second lens group becomes longer, which hinders downsizing of the optical system, which is not preferable. On the other hand, if the upper limit in conditional expression (3) is exceeded, the occurrence of curvature of field becomes significant and its correction becomes difficult. In this case, the curvature of field can be corrected by increasing the number of lenses constituting the third lens group. However, an increase in the number of lenses constituting the third lens group is not preferable for downsizing the optical system.

In addition, if the said conditional expression (3) satisfies the range shown next, a more preferable effect can be anticipated.
(3a) 0.41 ≦ β3 ≦ 0.83
By satisfying the range defined by the conditional expression (3a), a smaller inner focus lens can be realized without deteriorating the imaging performance.

Furthermore, when the conditional expression (3a) satisfies the following range, a smaller and higher performance inner focus lens can be realized.
(3b) 0.49 ≦ β3 ≦ 0.72

  Another object of the present invention is to provide an inner focus lens suitable for moving image shooting. For this purpose, it is important to suppress changes in photographing magnification due to focus group wobbling, which is performed during autofocus processing or the like.

  By reducing the size and weight of the focus group, quick focusing is facilitated, so that good moving image shooting is possible. For this reason, in the present invention, as described above, the second lens group, which is the focus group, is composed of one element, thereby reducing the size and weight of the second lens group and enabling rapid focusing. Yes. Also, by reducing the size and weight of the second lens group, the load on the driving means that controls the driving of the focus group is also reduced, which contributes to power saving. In addition, in order to reduce the change in the photographing magnification due to the wobbling of the focus group, the second lens group as the focus group is not only arranged on the image plane side from the aperture stop, but also the second lens group during focusing. It is important to suppress the amount of movement.

Therefore, in the inner focus type lens according to the present invention, it is preferable that the following conditional expression is satisfied when the focal length of the second lens group is f2 and the focal length of the entire optical system is f.
(4) -1.91 ≦ f2 / f ≦ −0.57

  Conditional expression (4) represents a condition for suppressing the amount of movement of the focus group (second lens group) during focusing. If the amount of movement of the focus group is reduced, the total length of the optical system can be shortened, and when the auto focus is adopted, the load of the driving means that controls the drive of the focus group is reduced, which contributes to power saving. It also contributes to reducing the change in photographing magnification due to focus group wobbling.

  If the lower limit of conditional expression (4) is not reached, the refractive power of the second lens group becomes too weak and the amount of movement of the second lens group during focusing increases. In addition to the large change, it is not preferable for downsizing the optical system. On the other hand, if the upper limit in conditional expression (4) is exceeded, the refractive power of the second lens group becomes too strong, and the amount of movement of the second lens group during focusing is significantly reduced. In this case, it is advantageous for suppressing a change in photographing magnification due to wobbling of the second lens group and for reducing the size of the optical system. However, the sensitivity when moving the second lens group becomes too high, which not only makes it difficult to control the driving of the second lens group during focusing, but also causes excessive fluctuations in the angle of view. It becomes.

In addition, if the said conditional expression (4) satisfies the range shown next, a more preferable effect can be anticipated.
(4a) -1.75 ≦ f2 / f ≦ −0.65
By satisfying the range defined by the conditional expression (4a), it is possible to appropriately suppress the moving amount of the second lens unit during focusing and to realize a small inner focus lens suitable for moving image shooting. it can.

Further, when the conditional expression (4a) satisfies the following range, a smaller inner focus lens suitable for moving image shooting can be realized.
(4b) −1.60 ≦ f2 / f ≦ −0.72

Further, in the inner focus type lens according to the present invention, when the radius of curvature of the outermost object side surface of the second lens group is ra2 and the radius of curvature of the outermost image side surface of the second lens group is rb2, the following conditional expression is satisfied. It is preferable to do.
(5) 1.95 ≦ ra2 / rb2 ≦ 10.22

  Conditional expression (5) defines the ratio of the radius of curvature of the most object side surface of the second lens group and the radius of curvature of the most image side surface of the second lens group. By satisfying conditional expression (5), it is possible to configure a focus group particularly suitable for moving image shooting.

  If the lower limit of conditional expression (5) is not reached, the refractive power of the second lens group becomes too weak and the amount of movement of the second lens group during focusing increases. In addition to the large change, it is not preferable for downsizing the optical system. On the other hand, if the upper limit of conditional expression (5) is exceeded, the refractive power of the second lens group becomes too strong, and the amount of movement of the second lens group during focusing is significantly reduced. In this case, it is advantageous for suppressing a change in photographing magnification due to wobbling of the second lens group and for reducing the size of the optical system. However, the sensitivity when moving the second lens group becomes too high, which not only makes it difficult to control the driving of the second lens group during focusing, but also causes excessive fluctuations in the angle of view. It becomes.

In addition, the said conditional expression (5) can anticipate a more preferable effect, if the range shown next is satisfied.
(5a) 2.20 ≦ ra2 / rb2 ≦ 9.37
By satisfying the range defined by the conditional expression (5a), it is possible to appropriately suppress the moving amount of the second lens unit during focusing and to realize a small inner focus lens suitable for moving image shooting. it can.

Furthermore, when the conditional expression (5a) satisfies the following range, a smaller inner focus lens suitable for moving image shooting can be realized.
(5b) 2.44 ≦ ra2 / rb2 ≦ 8.51

Furthermore, in the inner focus type lens according to the present invention, it is preferable that the following conditional expression is satisfied, where f is the focal length of the entire optical system and r1 is the radius of curvature of the first object group.
(6) -1.96 ≦ r1 / f ≦ −0.38

  Conditional expression (6) represents a condition for correcting the curvature of field appropriately, while reducing the size of the entire optical system. When trying to obtain a wide-angle focal length, it becomes a problem to sufficiently correct aberrations that are strongly influenced by the angle of view, particularly curvature of field. Therefore, by satisfying conditional expression (6), it is possible to dispose a lens having a concave surface on the object side on the most object side of the first lens group, and it is possible to effectively correct field curvature.

  If the lower limit of conditional expression (6) is not reached, the occurrence of curvature of field becomes remarkable and correction thereof becomes difficult, which is not preferable. On the other hand, if the upper limit in conditional expression (6) is exceeded, the aperture of the lens arranged on the most object side of the first lens group becomes large, which hinders downsizing of the optical system.

In addition, when the conditional expression (6) satisfies the following range, a more preferable effect can be expected.
(6a) −1.80 ≦ r1 / f ≦ −0.42
By satisfying the range defined by the conditional expression (6a), it is possible to appropriately correct the field curvature while reducing the size of the entire optical system.

Further, when the conditional expression (6a) satisfies the following range, it is possible to realize an inner focus type lens that is smaller and can correct the field curvature.
(6b) −1.63 ≦ r1 / f ≦ −0.47

  As described above, according to the present invention, it is possible to provide a small and wide-angle inner focus lens that can be applied to a 35 mm film type image pickup device and has high imaging performance. In addition, it is possible to provide a small inner focus lens in which a change in photographing magnification due to wobbling of the focus group is suppressed. In particular, by satisfying the above conditional expressions, it is possible to realize an inner focus lens having a smaller size and higher imaging performance, which is suitable for moving image shooting.

  Next, an imaging apparatus suitable for the inner focus lens of the present invention having the above-described features will be described. FIG. 1 is a diagram showing an embodiment of an imaging apparatus according to the present invention. This imaging apparatus can handle not only still images but also moving image shooting.

  The imaging device 100 includes a camera block 10 that performs an imaging function, a camera signal processing unit 20 that performs signal processing such as analog-digital conversion of a captured image signal, and an image processing unit 30 that performs recording and reproduction processing of the image signal. It is equipped with. In addition, the imaging apparatus 100 includes a display unit 40 configured by an LCD (Liquid Crystal Display) or the like that displays captured images, and an R / W (reader) that writes and reads image signals to and from the memory card 1000. / Writer) 50, a CPU (Central Processing Unit) 60 for controlling the entire imaging apparatus 100, an input unit 70 including various switches and the like that are operated by a user, and a lens disposed in the camera block 10 And a lens drive controller 80 for controlling the driving of the lens.

  The camera block 10 includes an optical system including an inner focus lens 11 and an imaging device 12 including a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), and the like. The inner focus lens 11 is an inner focus lens of the present invention having the above-described features. The image sensor 12 may be an APS-C size image sensor or a 35 mm film type image sensor.

  The camera signal processing unit 20 performs various types of signal processing such as conversion of the output signal from the image sensor 12 into a digital signal, noise removal, image quality correction, and conversion into a luminance / color difference signal.

  The image processing unit 30 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.

  The display unit 40 has a function of displaying various data such as an operation state of the user input unit 70 and a captured image.

  The R / W 50 writes the image data encoded by the image processing unit 30 to the memory card 1000 and reads the image data recorded on the memory card 1000.

  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, 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 a user to the CPU 60.

  The lens drive control unit 80 controls a motor (not shown) that drives the focus group of the inner focus lens 11 based on a control signal from the CPU 60.

  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.

  Subsequently, an operation in the imaging apparatus 100 will be described.

  In the shooting standby state, under the control of the CPU 60, an image signal shot by the camera block 10 is output to the display unit 40 via the camera signal processing unit 20 and displayed as a camera through image. 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 the inner focus lens 11 is controlled based on the control of the lens drive control unit 80. The focus group is moved.

  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.

  In focusing, for example, when the shutter release button of the input unit 70 is half-pressed or when the shutter release button is fully pressed for recording (photographing), the lens drive control unit 80 performs inner focus based on a control signal from the CPU 60. This is done by moving the focus group of the expression 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 reproduced image signal is output to the display unit 40 and the reproduced image is displayed.

  Embodiments of an inner focus lens according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the following examples.

FIG. 2 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the first embodiment. The inner focus type lens includes a first lens group G ₁₁ having a positive refractive power, a second lens group G ₁₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _13, is formed is disposed.

The first lens group G ₁₁ includes a negative lens L ₁₁₁ , a positive lens L ₁₁₂ , an aperture stop S that defines a predetermined aperture, and a positive lens L _{113 in} order from the object side. The negative lens L ₁₁₁ and the positive lens L ₁₁₂ are cemented. The both surfaces of the positive lens L _113, aspheric surface is formed. The first lens group G ₁₁ is fixed on the optical axis.

The second lens group G ₁₂ includes, is composed of a negative lens L _121. On both surfaces of the negative lens L _121, aspheric surface is formed. The second lens group G ₁₂ includes, by moving toward the image side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₁₃ is constituted in order from the object side, a positive lens L _131, a negative lens L _132, a negative lens L _133, is the arrangement. The positive lens L ₁₃₁ and the negative lens L ₁₃₂ are cemented. Aspherical surfaces are formed on both surfaces of the negative lens _L133 . The third lens group G ₁₃ is fixed on the optical axis.

  Various numerical data related to the inner focus lens according to Example 1 will be described below.

(Lens data)
r ₁ = -23.10
d ₁ = 0.80 nd ₁ = 1.80 νd ₁ = 25.46
r ₂ = -85.23
d ₂ = 1.49 nd ₂ = 1.83 νd ₂ = 42.72
r ₃ = -42.36
d ₃ = 0.85
r ₄ = ∞ (aperture stop)
d ₄ = 1.40
r ₅ = 18.59 (aspherical surface)
d ₅ = 2.98 nd ₃ = 1.76 νd ₃ = 49.24
r ₆ = -45.03 (aspherical surface)
d ₆ = D (6) (variable)
r ₇ = 119.57 (aspherical surface)
d ₇ = 0.70 nd ₄ = 1.58 νd ₄ = 59.46
r ₈ = 14.18 (aspherical surface)
d ₈ = D (8) (variable)
r ₉ = 51.20
d ₉ = 5.36 nd ₅ = 1.83 νd ₅ = 42.72
r ₁₀ = -10.02
d ₁₀ = 1.00 nd ₆ = 1.63 νd ₆ = 34.57
r ₁₁ = 86.11
d ₁₁ = 4.95
r ₁₂ = -10.55 (aspherical surface)
d ₁₂ = 1.00 nd ₇ = 1.68 νd ₇ = 31.16
r ₁₃ = -14.19 (aspherical surface)
d ₁₃ = 20.03
r ₁₄ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(5th page)
k = 0,
A ₄ = -3.7579 × 10 ^-5 , A ₆ = -1.0389 × 10 ^-8 ,
A ₈ = -2.0023 × 10 ⁻¹⁰ , A ₁₀ = −4.1163 × 10 ⁻¹¹
(Sixth surface)
k = 0,
A ₄ = -5.9027 × 10 ^-6 , A ₆ = 5.5887 × 10 ^-7 ,
A ₈ = -1.1004 × 10 ^-8 , A ₁₀ = 3.9911 × 10 ^-11
(Seventh side)
k = 0,
A ₄ = 7.4881 × 10 ^-5 , A ₆ = -1.1023 × 10 ^-6 ,
A ₈ = -1.6439 × 10 ^-9 , A ₁₀ = 9.2542 × 10 ^-11
(8th page)
k = 0,
A ₄ = 1.0857 × 10 ⁻⁴ , A ₆ = −1.6255 × 10 ⁻⁶ ,
A ₈ = 9.5546 × 10 ^-9 , A ₁₀ = 7.7733 × 10 ^-11
(Twelfth surface)
k = 0,
A ₄ = 4.5713 × 10 ^-4 , A ₆ = -4.2921 × 10 ^-6 ,
A ₈ = 2.8083 × 10 ^-8 , A ₁₀ = -5.6441 × 10 ^-11
(13th page)
k = 0,
A ₄ = 4.1193 × 10 ⁻⁴ , A ₆ = −3.8255 × 10 ⁻⁶ ,
^{_{A 8 = 2.1891 × 10 -8,}} A 10 = -5.6738 × 10 -11

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 350mm)
D (6) 1.49 3.13
D (8) 5.53 3.89

f (focal length of the entire optical system) = 36.06
Fno (F number) = 2.884
ω (half angle of view) = 31.28
Y (image height) = 21.6

(Numerical value for conditional expression (1))
L1 (the distance from the most object side lens surface vertex of the first lens group G ₁₁ to the most image side lens surface vertex) = 7.52
L (distance from the most object side lens surface vertex in the first lens group G ₁₁ to the most image side lens surface vertex in the third lens group G ₁₃ ) = 27.55
L1 / L = 0.27

(Numerical value related to conditional expression (2))
tan ω = 0.61

(Numerical value for conditional expression (3))
.beta.3 (imaging magnification of the third lens group G ₁₃ in the infinite object in-focus state) = 0.49

(Numerical values related to conditional expression (4))
f2 (the focal length of the second lens group G ₁₂₎ = - 27.55
f2 / f = -0.76

(Numerical values related to conditional expression (5))
ra2 (curvature of the most object side surface of the second lens group G ₁₂ radius) = 119.57
rb2 (curvature of the most image plane side surface of the second lens group G ₁₂ radius) = 14.18
ra2 / rb2 = 8.43

(Numerical values related to conditional expression (6))
r1 (curvature of the most object side surface of the first lens group G ₁₁ radius) = - 23.10
r1 / f = -0.64

  FIG. 3 is a diagram illustrating various aberrations of the inner focus lens according to Example 1 in the state of focusing on an object at infinity. In the figure, the curve represents the aberration of the wavelength corresponding to the d-line (λ = 587.56 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 4 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the second embodiment. The inner focus type lens includes a first lens group G ₂₁ having a positive refractive power, a second lens group G ₂₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _23, is formed are disposed.

The first lens group G ₂₁ includes a negative lens L ₂₁₁ , an aperture stop S that defines a predetermined aperture, and a positive lens L _{212 in} order from the object side. The image-side surface of the negative lens L _211, and on both surfaces of the positive lens L _212, the aspheric surface is formed. The first lens group G ₂₁ includes, is fixed on the optical axis.

The second lens group G ₂₂ includes, is composed of a negative lens L _221. An aspheric surface is formed on both surfaces of the negative lens L ₂₂₁ . The second lens group G ₂₂ includes, by moving toward the image side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₂₃ includes, in order from the object side, a positive lens L _231, a negative lens L _232, a negative lens L _233, is formed are disposed. The positive lens L ₂₃₁ and the negative lens L ₂₃₂ are cemented. Aspherical surfaces are formed on both surfaces of the negative lens _L233 . The third lens group G ₂₃ is fixed on the optical axis.

  Various numerical data related to the inner focus lens according to Example 2 will be described below.

(Lens data)
r ₁ = -19.93
d ₁ = 0.80 nd ₁ = 1.68 νd ₁ = 31.16
r ₂ = 137.06 (aspherical surface)
d ₂ = 0.80
r ₃ = ∞ (aperture stop)
d ₃ = 1.06
r ₄ = 18.58 (aspherical surface)
d ₄ = 3.05 nd ₂ = 1.76 νd ₂ = 49.24
r ₅ = -27.11 (aspherical surface)
d ₅ = D (5) (variable)
r ₆ = 48.85 (aspherical surface)
d ₆ = 0.7 nd ₃ = 1.58 νd ₃ = 59.46
r ₇ = 18.98 (aspherical surface)
d ₇ = D (7) (variable)
r ₈ = 73.56
d ₈ = 5.45 nd ₄ = 1.83 νd ₄ = 42.72
r ₉ = -10.80
d ₉ = 2.39 nd ₅ = 1.63 νd ₅ = 34.57
r ₁₀ = 90.94
d ₁₀ = 5.61
r ₁₁ = -10.36 (aspherical surface)
d ₁₁ = 1.00 nd ₆ = 1.68 νd ₆ = 31.16
r ₁₂ = -13.76 (aspherical surface)
d ₁₂ = 18.49
r ₁₃ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(Second side)
k = 0,
A ₄ = -9.1976 × 10 ^-5 , A ₆ = 8.5125 × 10 ^-7 ,
A ₈ = -4.8209 × 10 ^-9 , A ₁₀ = 1.8905 × 10 ^-11
(Fourth surface)
k = 0,
A ₄ = -1.1683 × 10 ⁻⁴ , A ₆ = 4.0156 × 10 ⁻⁷ ,
A ₈ = -3.3565 × 10 ^-9 , A ₁₀ = 1.6350 × 10 ^-11
(5th page)
k = 0,
A ₄ = 1.3533 × 10 ⁻⁵ , A ₆ = −2.5357 × 10 ⁻⁷ ,
A ₈ = 1.5784 × 10 ⁻⁹ , A ₁₀ = −7.4131 × 10 ⁻¹²
(Sixth surface)
k = 0,
A ₄ = 4.6250 × 10 ⁻⁵ , A ₆ = −5.9295 × 10 ⁻⁷ ,
A ₈ = 6.5099 × 10 ⁻⁹ , A ₁₀ = −6.5296 × 10 ⁻¹¹
(Seventh side)
k = 0,
A ₄ = 6.3043 × 10 ^-5 , A ₆ = -5.0087 × 10 ^-7 ,
A ₈ = 3.9486 × 10 ⁻⁹ , A ₁₀ = −1.6257 × 10 ⁻¹¹
(11th page)
k = 0,
A ₄ = 4.1167 × 10 ^-4 , A ₆ = -4.1098 × 10 ^-6 ,
A ₈ = 2.6475 × 10 ⁻⁸ , A ₁₀ = −4.7111 × 10 ⁻¹¹
(Twelfth surface)
k = 0,
A ₄ = 3.7570 × 10 ⁻⁴ , A ₆ = −3.7443 × 10 ⁻⁶ ,
A ₈ = 2.2776 × 10 ⁻⁸ , A ₁₀ = −6.2208 × 10 ⁻¹¹

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 350mm)
D (5) 1.51 5.05
D (7) 7.71 4.17

f (focal length of the entire optical system) = 36.04
Fno (F number) = 2.884
ω (half angle of view) = 31.42
Y (image height) = 21.6

(Numerical value for conditional expression (1))
L1 (the distance from the most object side lens surface vertex of the first lens group G ₂₁ to the most image side lens surface vertex) = 5.72
L (distance from the most object side lens surface vertex in the first lens group G ₂₁ to the most image side lens surface vertex in the third lens group G ₂₃ ) = 30.08
L1 / L = 0.19

(Numerical value related to conditional expression (2))
tan ω = 0.61

(Numerical value for conditional expression (3))
.beta.3 (imaging magnification of the third lens group G ₂₃ in the infinite object in-focus state) = 0.63

(Numerical values related to conditional expression (4))
f2 (the focal length of the second lens group G ₂₂₎ = - 53.47
f2 / f = -1.48

(Numerical values related to conditional expression (5))
ra2 (curvature of the most object side surface of the second lens group G ₂₂ radius) = 48.85
rb2 (curvature of the most image plane side surface of the second lens group G ₂₂ radius) = 18.98
ra2 / rb2 = 2.57

(Numerical values related to conditional expression (6))
r1 (curvature of the most object side surface of the first lens group G ₂₁ radius) = - 19.93
r1 / f = -0.55

  FIG. 5 is a diagram illustrating various aberrations of the inner focus lens according to Example 2 in the state of focusing on an object at infinity. In the figure, the curve represents the aberration of the wavelength corresponding to the d-line (λ = 587.56 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 6 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the third example. The inner focus type lens includes a first lens group G ₃₁ having a positive refractive power, a second lens group G ₃₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _33, is formed are disposed.

The first lens group G ₃₁ includes a negative lens L ₃₁₁ , a positive lens L ₃₁₂ , an aperture stop S that defines a predetermined aperture, and a positive lens L _{313 in} order from the object side. The negative lens L ₃₁₁ and the positive lens L ₃₁₂ are cemented. Aspherical surfaces are formed on both surfaces of the positive lens _L313 . The first lens group G ₃₁ is fixed on the optical axis.

The second lens group G ₃₂ is constituted by a negative lens L _321. Aspherical surfaces are formed on both surfaces of the negative lens _L321 . The second lens group G ₃₂ is, by moving toward the image side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₃₃ includes a positive lens L ₃₃₁ , a negative lens L _332, and a negative lens L ₃₃₃ arranged in this order from the object side. The positive lens L ₃₃₁ and the negative lens L ₃₃₂ are cemented. Aspheric surfaces are formed on both surfaces of the negative lens _L333 . The third lens group _G33 is fixed on the optical axis.

  Various numerical data relating to the inner focus lens according to Example 3 will be described below.

(Lens data)
r ₁ = -22.52
d ₁ = 1.00 nd ₁ = 1.81 νd ₁ = 25.46
r ₂ = -83.18
d ₂ = 2.00 nd ₂ = 1.83 νd ₂ = 42.72
r ₃ = -39.25
d ₃ = 1.74
r ₄ = ∞ (aperture stop)
d ₄ = 1.74
r ₅ = 19.06 (aspherical surface)
d ₅ = 3.09 nd ₃ = 1.77 νd ₃ = 49.24
r ₆ = -43.71 (aspherical surface)
d ₆ = D (6) (variable)
r ₇ = 53.43 (aspherical surface)
d ₇ = 0.70 nd ₄ = 1.58 νd ₄ = 59.46
r ₈ = 13.66 (aspherical surface)
d ₈ = D (8) (variable)
r ₉ = 113.98
d ₉ = 5.32 nd ₅ = 1.83 νd ₅ = 42.72
r ₁₀ = -9.85
d ₁₀ = 1.00 nd ₆ = 1.64 νd ₆ = 34.57
r ₁₁ = 106.37
d ₁₁ = 4.47
r ₁₂ = -12.46 (aspherical surface)
d ₁₂ = 1.00 nd ₇ = 1.69 νd ₇ = 31.16
r ₁₃ = -17.05 (Aspherical surface)
d ₁₃ = 20.58
r ₁₄ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(5th page)
k = 0,
A ₄ = -3.7970 × 10 ^-5 , A ₆ = 1.1566 × 10 ^-8 ,
A ₈ = -2.4478 × 10 ^-9 , A ₁₀ = 1.8357 × 10 ^-11
(Sixth surface)
k = 0,
A ₄ = -8.2768 × 10 ^-6 , A ₆ = 4.5442 × 10 ^-7 ,
A ₈ = -7.7578 × 10 ^-9 , A ₁₀ = 4.5036 × 10 ^-11
(Seventh side)
k = 0,
A ₄ = 5.4481 × 10 ⁻⁵ , A ₆ = −8.6181 × 10 ⁻⁷ ,
A ₈ = 3.6766 × 10 ⁻¹⁰ , A ₁₀ = −3.3227 × 10 ⁻¹²
(8th page)
k = 0,
A ₄ = 9.7814 × 10 ⁻⁵ , A ₆ = −1.2192 × 10 ⁻⁶ ,
A ₈ = 1.9500 × 10 ^-9 , A ₁₀ = 3.9252 × 10 ^-11
(Twelfth surface)
k = 0,
A ₄ = 4.3871 × 10 ^-4 , A ₆ = -4.6942 × 10 ^-6 ,
A ₈ = 2.6627 × 10 ⁻⁸ , A ₁₀ = −7.0111 × 10 ⁻¹¹
(13th page)
k = 0,
A ₄ = 4.0917 × 10 ⁻⁴ , A ₆ = −4.0925 × 10 ⁻⁶ ,
A ₈ = 2.0762 × 10 ⁻⁸ , A ₁₀ = −4.4805 × 10 ⁻¹¹

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 350mm)
D (6) 1.47 3.08
D (8) 5.47 3.86

f (focal length of the entire optical system) = 36.10
Fno (F number) = 2.884
ω (half angle of view) = 31.09
Y (image height) = 21.6

(Numerical value for conditional expression (1))
L1 (distance from the vertex of the most object side lens surface to the vertex of the most image side lens surface in the first lens group G ₃₁ ) = 9.57
L (distance from the most object side lens surface vertex in the first lens group G ₃₁ to the most image side lens surface vertex in the third lens group G ₃₃ ) = 29.00
L1 / L = 0.33

(Numerical value related to conditional expression (2))
tan ω = 0.60

(Numerical value for conditional expression (3))
.beta.3 (imaging magnification of the third lens group G ₃₃ in the infinite object in-focus state) = 0.71

(Numerical values related to conditional expression (4))
f2 (the focal length of the second lens group G ₃₂₎ = - 31.56
f2 / f = -0.87

(Numerical values related to conditional expression (5))
ra2 (curvature of the most object side surface of the second lens group G ₃₂ radius) = 53.43
rb2 (curvature of the most image plane side surface of the second lens group G ₃₂ radius) = 13.66
ra2 / rb2 = 3.91

(Numerical values related to conditional expression (6))
r1 (curvature of the most object side surface of the first lens group G ₃₁ radius) = - 22.52
r1 / f = -0.62

  FIG. 7 is a diagram illustrating various aberrations of the inner focus lens according to Example 3 in the state of focusing on an object at infinity. In the figure, the curve represents the aberration of the wavelength corresponding to the d-line (λ = 587.56 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 8 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the fourth example. The inner focus type lens includes a first lens group G ₄₁ having a positive refractive power, a second lens group G ₄₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _43, is formed are disposed.

The first lens group G ₄₁ includes a negative lens L ₄₁₁ , an aperture stop S that defines a predetermined aperture, and a positive lens L _{412 in} order from the object side. An aspherical surface is formed on the image side surface of the negative lens L ₄₁₁ and both surfaces of the positive lens L ₄₁₂ . The first lens group _G41 is fixed on the optical axis.

The second lens group _G42 includes a negative lens _L421 . An aspheric surface is formed on both surfaces of the negative lens _L421 . The second lens group G ₄₂ is, by moving toward the image side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₄₃ includes, in order from the object side, a positive lens L _431, a negative lens L _432, a negative lens L _433, is formed are disposed. The positive lens L ₄₃₁ and the negative lens L ₄₃₂ are cemented. Aspherical surfaces are formed on both surfaces of the negative lens _L433 . The third lens group _G43 is fixed on the optical axis.

  Various numerical data relating to the inner focus lens according to Example 4 will be described below.

(Lens data)
r ₁ = -50.99
d ₁ = 0.80 nd ₁ = 1.69 νd ₁ = 31.16
r ₂ = 23.23 (aspherical surface)
d ₂ = 2.00
r ₃ = ∞ (aperture stop)
d ₃ = 2.82
r ₄ = 19.79 (aspherical surface)
d ₄ = 4.00 nd ₂ = 1.82 νd ₂ = 42.71
r ₅ = -29.79 (aspherical surface)
d ₅ = D (5) (variable)
r ₆ = 164.06 (aspherical surface)
d ₆ = 0.7 nd ₃ = 1.81 νd ₃ = 40.73
r ₇ = 32.34 (aspherical surface)
d ₇ = D (7) (variable)
r ₈ = 132.06
d ₈ = 5.11 nd ₄ = 1.83 νd ₄ = 42.72
r ₉ = -9.80
d ₉ = 2.50 nd ₅ = 1.67 νd ₅ = 32.17
r ₁₀ = -182.53
d ₁₀ = 4.42
r ₁₁ = -11.13 (aspherical surface)
d ₁₁ = 1.00 nd ₆ = 1.82 νd ₆ = 24.06
r ₁₂ = -14.16 (aspherical surface)
d ₁₂ = 21.17
r ₁₃ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(Second side)
k = 0,
A ₄ = 8.9590 × 10 ⁻⁶ , A ₆ = 2.6924 × 10 ⁻⁷ ,
A ₈ = 3.0033 × 10 ⁻⁹ , A ₁₀ = 3.2944 × 10 ⁻¹²
(Fourth surface)
k = 0,
A ₄ = -6.4444 × 10 ⁻⁵ , A ₆ = −2.7162 × 10 ⁻⁷ ,
A ₈ = -4.7892 × 10 ^-10 , A ₁₀ = 3.3933 × 10 ^-11
(5th page)
k = 0,
A ₄ = -3.0477 × 10 ⁻⁵ , A ₆ = −9.1908 × 10 ⁻⁸ ,
A ₈ = -1.4445 × 10 ^-9 , A ₁₀ = 2.8211 × 10 ^-11
(Sixth surface)
k = 0,
A ₄ = 2.4254 × 10 ⁻⁴ , A ₆ = −2.7472 × 10 ⁻⁶ ,
A ₈ = 2.6567 × 10 ⁻⁸ , A ₁₀ = −1.4511 × 10 ⁻¹⁰
(Seventh side)
k = 0,
A ₄ = 2.7890 × 10 ⁻⁴ , A ₆ = −2.5865 × 10 ⁻⁶ ,
A ₈ = 2.4217 × 10 ⁻⁸ , A ₁₀ = −9.0326 × 10 ⁻¹¹
(11th page)
k = 0,
A ₄ = 5.8217 × 10 ⁻⁴ , A ₆ = −5.1945 × 10 ⁻⁶ ,
A ₈ = 2.8060 × 10 ^-8 , A ₁₀ = -7.5097 × 10 ^-11
(Twelfth surface)
k = 0,
A ₄ = 5.3249 × 10 ⁻⁴ , A ₆ = −4.11956 × 10 ⁻⁶ ,
A ₈ = 1.6761 × 10 ^-8 , A ₁₀ = -2.5652 × 10 ^-11

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 350mm)
D (5) 1.54 4.03
D (7) 6.16 3.67

f (focal length of the entire optical system) = 30.90
Fno (F number) = 2.884
ω (half angle of view) = 35.77
Y (image height) = 21.6

(Numerical value for conditional expression (1))
L1 (distance from the vertex of the most object side lens surface to the vertex of the most image side lens surface in the first lens group G ₄₁ ) = 9.62
L (distance from the most object side lens surface vertex in the first lens group G ₄₁ to the most image side lens surface vertex in the third lens group G ₄₃ ) = 31.05
L1 / L = 0.31

(Numerical value related to conditional expression (2))
tan ω = 0.72

(Numerical value for conditional expression (3))
.beta.3 (imaging magnification of the third lens group G ₄₃ in the infinite object in-focus state) = 0.55

(Numerical values related to conditional expression (4))
f2 (the focal length of the second lens group G ₄₂₎ = - 49.79
f2 / f = -1.61

(Numerical values related to conditional expression (5))
ra2 (curvature of the most object side surface of the second lens group G ₄₂ radius) = 164.06
rb2 (curvature of the most image plane side surface of the second lens group G ₄₂ radius) = 32.34
ra2 / rb2 = 5.07

(Numerical values related to conditional expression (6))
r1 (the radius of curvature of the most object side surface of the first lens group G ₄₁ ) = − 50.99
r1 / f = -1.65

  FIG. 9 is a diagram illustrating various aberrations of the inner focus lens according to Example 4 when the object at infinity is in focus. In the figure, the curve represents the aberration of the wavelength corresponding to the d-line (λ = 587.56 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 10 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the fifth example. The inner focus type lens includes a first lens group G ₅₁ having a positive refractive power, a second lens group G ₅₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _53, is formed are disposed.

The first lens group G ₅₁ includes, in order from the object side, a negative lens L ₅₁₁ , an aperture stop S that defines a predetermined aperture, and a positive lens L ₅₁₂ . Aspherical surfaces are formed on both surfaces of the positive lens L ₅₁₂ . The first lens group G ₅₁ is fixed on the optical axis.

The second lens group G ₅₂ includes a negative lens L ₅₂₁ . An aspheric surface is formed on both surfaces of the negative lens L ₅₂₁ . The second lens group G ₅₂ is, by moving toward the image side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₅₃ includes a positive lens L ₅₃₁ , a negative lens L _532, and a negative lens L ₅₃₃ arranged in order from the object side. The positive lens L ₅₃₁ and the negative lens L ₅₃₂ are cemented. Aspherical surfaces are formed on both surfaces of the negative lens _L533 . The third lens group G ₅₃ is fixed on the optical axis.

  Various numerical data relating to the inner focus lens according to Example 5 will be described below.

(Lens data)
r ₁ = -20.97
d ₁ = 1.24 nd ₁ = 1.65 νd ₁ = 33.84
r ₂ = -36.16
d ₂ = 1.74
r ₃ = ∞ (aperture stop)
d ₃ = 1.74
r ₄ = 16.76 (aspherical surface)
d ₄ = 4.48 nd ₂ = 1.58 νd ₂ = 59.46
r ₅ = -29.89 (aspherical surface)
d ₅ = D (5) (variable)
r ₆ = 38.80 (aspherical surface)
d ₆ = 0.7 nd ₃ = 1.83 νd ₃ = 37.29
r ₇ = 15.74 (aspherical surface)
d ₇ = D (7) (variable)
r ₈ = 31.75
d ₈ = 5.32 nd ₄ = 1.74 νd ₄ = 0.45
r ₉ = -10.35
d ₉ = 1.00 nd ₅ = 1.60 νd ₅ = 39.22
r ₁₀ = 26.14
d ₁₀ = 8.71
r ₁₁ = -9.23 (aspherical surface)
d ₁₁ = 1.00 nd ₆ = 1.50 νd ₆ = 81.56
r ₁₂ = -13.63 (aspherical surface)
d ₁₂ = 18.24
r ₁₃ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(Fourth surface)
k = 0,
A ₄ = -3.5566 × 10 ⁻⁵ , A ₆ = −1.3254 × 10 ⁻⁷ ,
A ₈ = 1.9653 × 10 ⁻¹⁰ , A ₁₀ = −5.8389 × 10 ⁻¹²
(5th page)
k = 0,
A ₄ = 2.3395 × 10 ⁻⁵ , A ₆ = −4.2314 × 10 ⁻⁹ ,
A ₈ = -1.0787 × 10 ^-9 , A ₁₀ = 3.4862 × 10 ^-12
(Sixth surface)
k = 0,
A ₄ = 5.5796 × 10 ⁻⁵ , A ₆ = −6.11311 × 10 ⁻⁷ ,
A ₈ = 3.1801 × 10 ⁻⁹ , A ₁₀ = 6.3089 × 10 ⁻¹²
(Seventh side)
k = 0,
A ₄ = 7.0740 × 10 ⁻⁵ , A ₆ = −3.33531 × 10 ⁻⁷ ,
A ₈ = -2.8816 × 10 ^-9 , A ₁₀ = 1.1528 × 10 ^-10
(11th page)
k = 0,
A ₄ = 2.1568 × 10 ^-4 , A ₆ = -3.0025 × 10 ^-6 ,
A ₈ = 2.5309 × 10 ⁻⁸ , A ₁₀ = −7.7120 × 10 ⁻¹¹
(Twelfth surface)
k = 0,
A ₄ = 1.8610 × 10 ⁻⁴ , A ₆ = −3.2328 × 10 ⁻⁶ ,
A ₈ = 2.5833 × 10 ^-8 , A ₁₀ = -1.0834 × 10 ^-10

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 350mm)
D (5) 1.50 3.50
D (7) 5.90 3.90

f (focal length of the entire optical system) = 44.99
Fno (F number) = 2.884
ω (half angle of view) = 25.69
Y (image height) = 21.6

(Numerical value for conditional expression (1))
L1 (the distance from the most object side lens surface vertex of the first lens group G ₅₁ to the most image side lens surface vertex) = 9.20
L (distance from the most object side lens surface vertex in the first lens group G ₅₁ to the most image side lens surface vertex in the third lens group G ₅₃ ) = 33.33
L1 / L = 0.28

(Numerical value related to conditional expression (2))
tan ω = 0.48

(Numerical value for conditional expression (3))
.beta.3 (imaging magnification of the third lens group G ₅₃ in the infinite object in-focus state) = 0.72

(Numerical values related to conditional expression (4))
f2 (the focal length of the second lens group G ₅₂₎ = - 31.98
f2 / f = -0.71

(Numerical values related to conditional expression (5))
ra2 (curvature of the most object side surface of the second lens group G ₅₂ radius) = 38.80
rb2 (curvature of the most image plane side surface of the second lens group G ₅₂ radius) = 15.74
ra2 / rb2 = 2.46

(Numerical values related to conditional expression (6))
r1 (curvature of the most object side surface of the first lens group G ₅₁ radius) = - 20.97
r1 / f = -0.47

  FIG. 11 is a diagram of various aberrations of the inner focus lens according to Example 5 in the state of focusing on an object at infinity. In the figure, the curve represents the aberration of the wavelength corresponding to the d-line (λ = 587.56 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

In the numerical data in each of the above embodiments, r ₁ , r ₂ ,... Are the curvature radii of the respective lenses and diaphragm surfaces, and d ₁ , d ₂ ,. thickness or their surface separations, nd _1, nd _2, the refractive index with respect to ... the d-line of each lens _{(λ = 587.56nm), νd 1} , νd 2, ···· are each lens d The Abbe number for the line (λ = 587.56 nm) is shown. The unit of length is all “mm”, and the unit of angle is “°”.

In addition, each of the above aspheric shapes has a depth of the aspheric surface Z, a curvature c (1 / r), a height from the optical axis h, a cone coefficient k, 4th order, 6th order, 8th order, 10th order. When the following aspheric coefficients are A ₄ , A ₆ , A ₈ , and A ₁₀ , respectively, and the light traveling direction is positive, the following aspheric coefficients are expressed by the following equations.

  In each of the above-described embodiments, an example of a small and wide-angle inner focus lens that can be applied to a 35 mm film type image pickup device and has high imaging performance is shown. The inner focus type lens in each of the above embodiments can perform better movie shooting by reducing the size and weight of the focus group and suppressing the change in shooting magnification due to wobbling of the focus group. In particular, by satisfying the above conditional expressions, it is possible to realize an inner focus lens having a smaller size and higher imaging performance, which is suitable for moving image shooting.

  In each of the above embodiments, an inner focus lens having a three-group configuration is shown. However, even if a lens having substantially no power is added to the three-group inner focus lens, the above conditional expressions are satisfied. Only then can the object of the present invention be achieved.

  As described above, the inner focus type lens according to the present invention is useful for a small-sized imaging device such as a photographic camera or a video camera, and is particularly suitable for an imaging device for moving image shooting. The imaging device according to the present invention is an imaging device suitable for the inner focus lens of the present invention having high imaging performance.

_{G 11, G 21, G 31} , G 41, G 51 first lens group _{G 12, G 22, G 32} , G 42, G 52 second lens group _{G 13, G 23, G 33} , G 43, G 53 the third lens group _{L 111, L 121, L 132} , L 133, L 211, L 221, L 232, L 233, L 311, L 321, L 332, L 333, L 411, L 421, L 432, L _{433, L 511, L 521,} L 532, L 533 negative lens _{L 112, L 113, L 131} , L 212, L 231, L 312, L 313, L 331, L 412, L 431, L 512, L 531 Positive lens S Aperture stop 10 Camera block 20 Camera signal processing unit 30 Image processing unit 40 Display unit 50 R / W (reader / writer)
60 CPU
DESCRIPTION OF SYMBOLS 70 Input part 80 Lens drive control part 100 Imaging device 1000 Memory card

Claims (6)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, arranged in order from the object side;
The second lens group is composed of one element,
The first lens group and the third lens group are fixed on an optical axis;
By moving the second lens group from the object side to the image plane side along the optical axis, focusing from the infinite object focusing state to the closest object focusing state is performed,
An inner focus type lens satisfying the following conditional expression:
(1) 0.13 ≦ L1 / L ≦ 0.43
(2) 0.47 ≦ tan ω ≦ 0.74
Where L1 is the distance from the most object side lens surface vertex to the most image side lens surface vertex in the first lens group, and L is the most object side lens surface vertex in the first lens group and the most in the third lens group. A distance to the apex of the image surface side lens surface, ω, represents a half angle of view in an infinitely focused object state. The inner focus type lens according to claim 1, wherein the following conditional expression is satisfied.
(3) 0.34 ≦ β3 ≦ 0.94
Here, β3 represents the imaging magnification of the third lens group in the infinite object focusing state. The inner focus lens according to claim 1, wherein the following conditional expression is satisfied.
(4) -1.91 ≦ f2 / f ≦ −0.57
Here, f2 represents the focal length of the second lens group, and f represents the focal length of the entire optical system. The inner focus type lens according to claim 1, wherein the following conditional expression is satisfied.
(5) 1.95 ≦ ra2 / rb2 ≦ 10.22
Here, ra2 represents the radius of curvature of the most object side surface of the second lens group, and rb2 represents the radius of curvature of the most image side surface of the second lens group. 5. The inner focus lens according to claim 1, wherein the following conditional expression is satisfied.
(6) -1.96 ≦ r1 / f ≦ −0.38
Here, f represents the focal length of the entire optical system, and r1 represents the radius of curvature of the outermost object side surface of the first lens group.   6. An image pickup comprising: the inner focus lens according to claim 1; and an image pickup device that converts an optical image formed by the inner focus lens into an electrical signal. apparatus.

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