JP5333406B2 - Photographic lens, optical apparatus, and method of manufacturing photographic lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photographic lens and so on capable of maintaining sufficient back focus as well as a sufficient angle of view, thereby simplifying the configuration of a lens barrel and shortening the entire length and the amount of movement. <P>SOLUTION: The photographic lens comprises, in order from an object side, a first lens group G1 of positive refractive power, a second lens group G2 of positive refractive power, and a third lens group G3 of negative refractive power. The first lens group has a negative meniscus lens L11 closest to the object and having a concave face directed toward the image side. An aperture diaphragm S is disposed between the first and second lens groups. When focusing from an infinity object point to a proximity object point, the first and second lens groups move toward the object while changing a space between the lens groups. A reflection preventing film is provided on at least one of optical faces of the first lens group. The reflection preventing film includes at least one layer formed by using a wet process. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a photographing lens, an optical apparatus having the photographing lens, and a method for manufacturing the photographing lens.

  Conventionally, many macro lenses capable of photographing a short-distance object point from an infinite object point to a photographing magnification of -1.0 times have been proposed (see, for example, Patent Document 1). Of the macro lenses, in a three-group lens, the first lens group and the second lens group form a so-called double gauss type, and a third lens group as a rear converter is added immediately thereafter. In particular, in order to reduce the overall length, the third lens group is often a negative lens group. Also, in recent years, for a three-group macro lens capable of photographing such a short distance object point, not only aberration performance but also ghost and flare, which are one of the factors that impair optical performance, have been severe. It is increasing. Therefore, higher performance is required for the antireflection film applied to the lens surface, and multilayer film design technology and multilayer film formation technology continue to advance to meet the demand (for example, see Patent Document 2).

JP 2000-284171 A JP 2000-356704 A

  However, if the third lens unit has a negative refractive power, there is a problem that the back divergent component is strong and the image plane is shifted toward the object side, so that sufficient back focus cannot be secured. At the same time, there has been a problem that reflected light that is ghost or flare is likely to be generated from the optical surface of such a photographing lens.

  The present invention has been made in view of such problems, and further reduces ghosts and flares, maintains a sufficient back focus while maintaining a sufficient angle of view, and simplifies the configuration of the lens barrel. It is an object of the present invention to provide a photographic lens capable of reducing the amount of movement of the group, an optical apparatus having the photographic lens, and a method for manufacturing the photographic lens.

In order to solve the above problems, the present invention provides:
From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups ,
The first lens group includes, in order from the object side, a negative meniscus lens disposed closest to the object side and having a concave surface facing the image side, a first positive lens, and a second positive lens .
An aperture stop is provided between the first lens group and the second lens group;
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
Provided is a photographic lens characterized by satisfying the following conditions .
0.10 <Da / Db <1.25
However,
Da: a distance on the optical axis between the most image side surface of the negative meniscus lens and the most object side surface of the first positive lens;
Db: Distance on the optical axis between the most image side surface of the first positive lens and the most object side surface of the second positive lens.
The present invention also provides:
From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups,
The first lens group includes a negative meniscus lens having a concave surface facing the image side closest to the object side,
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film includes at least one layer formed using a wet process,
Provided is a photographic lens characterized by satisfying the following conditions.
0.40 <X1 / f <0.90
However,
X1: absolute value of the amount of movement of the first lens unit on the optical axis when focusing from an infinite object point to the closest object point;
f: Focal length of the entire system.
The present invention also provides:
From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups,
The first lens group includes a negative meniscus lens having a concave surface facing the image side closest to the object side,
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film includes at least one layer formed using a wet process,
Provided is a photographic lens characterized by satisfying the following conditions.
0.35 <f / TL <1.20
However,
TL: Total length when focusing on infinity,
f: Focal length of the entire system.
The present invention also provides:
From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups,
The first lens group includes a negative meniscus lens that is disposed closest to the object side and has a concave surface facing the image side, and a positive lens that has a negative refractive power in combination, and an image side of the front group And a rear group having a positive refractive power in combination, and
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film includes at least one layer formed using a wet process,
Provided is a photographic lens characterized by satisfying the following conditions.
0.05 <fp / (− fn) <0.60
However,
fn: focal length of the front group,
fp: Focal length of the rear group.
The present invention also provides:
From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups,
The first lens group includes a negative meniscus lens that is disposed closest to the object side and has a concave surface facing the image side, and a positive lens that has a negative refractive power in combination, and an image side of the front group And a rear group having a positive refractive power in combination, and
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film includes at least one layer formed using a wet process,
Provided is a photographic lens characterized by satisfying the following conditions.
0.04 <f / (− fn) <0.40
However,
fn: focal length of the front group,
f: Focal length of the entire system.

  The present invention also provides an optical apparatus comprising the photographing lens.

The present invention also provides:
In order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power are substantially three lens groups. A method for producing a photographic lens comprising :
The first lens group includes, in order from the object side, a negative meniscus lens that is disposed closest to the object side with a concave surface facing the image side, a first positive lens, and a second positive lens .
An aperture stop is disposed between the first lens group and the second lens group,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Placed so that it is fixed to the image plane ,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
Provided is a method for manufacturing a photographic lens, which satisfies the following conditions .
0.10 <Da / Db <1.25
However,
Da: a distance on the optical axis between the most image side surface of the negative meniscus lens and the most object side surface of the first positive lens;
Db: Distance on the optical axis between the most image side surface of the first positive lens and the most object side surface of the second positive lens.

  According to the present invention, a photographic lens that can further reduce ghost and flare, maintain sufficient back focus while maintaining a sufficient angle of view, simplify the configuration of the lens barrel, and reduce the overall length and movement amount; It is possible to provide an optical apparatus provided with this and a method for manufacturing a photographic lens.

2A and 2B are cross-sectional views illustrating a configuration of a photographic lens according to a first example, where FIG. 3A illustrates a wide-angle end state, FIG. 3B illustrates an intermediate focal length state, and FIG. FIG. 2A is a diagram illustrating various aberrations of the photographing lens according to the first example, FIG. 3A is a diagram illustrating aberrations in an infinitely focused state, and FIG. (C) is an aberration diagram in the state where the imaging magnification is -1.0. It is sectional drawing which shows the structure of the imaging lens SL concerning 1st Example, Comprising: It is a figure explaining an example of a mode that the incident light ray reflects in the 1st ghost generating surface and the 2nd ghost generating surface. . It is sectional drawing which shows the structure of the photographic lens concerning 2nd Example, (a) shows a wide-angle end state, (b) shows an intermediate | middle focal-distance state, (c) shows a telephoto end state. FIG. 7 is a diagram illustrating various aberrations of the photographing lens according to the second example, (a) is a diagram illustrating various aberrations in an infinitely focused state, and (b) is a diagram illustrating various aberrations in a state where the imaging magnification is −0.5 times. (C) is an aberration diagram in the state where the imaging magnification is -1.0. It is sectional drawing which shows the structure of the photographic lens concerning 3rd Example, (a) shows a wide-angle end state, (b) shows an intermediate | middle focal-distance state, (c) shows a telephoto end state. FIG. 7A is a diagram illustrating various aberrations of the photographing lens according to the third example, FIG. 9A is a diagram illustrating aberrations in an infinitely focused state, and FIG. 9B is a diagram illustrating various aberrations in a state where the imaging magnification is −0.5 times. (C) is an aberration diagram in the state where the imaging magnification is -1.0. It is sectional drawing which shows the structure of the photographic lens concerning 4th Example, (a) shows a wide-angle end state, (b) shows an intermediate focal distance state, (c) shows a telephoto end state. FIG. 6A is a diagram illustrating various aberrations of the photographing lens according to the fourth example. FIG. 9A is a diagram illustrating various aberrations in the infinite focus state, and FIG. (C) is an aberration diagram in the state where the imaging magnification is -1.0. 1 is a cross-sectional view of a digital single-lens reflex camera equipped with a photographic lens according to the present embodiment. It is a flowchart for demonstrating the manufacturing method of the imaging lens concerning this embodiment. It is explanatory drawing which shows an example of the layer structure of an antireflection film. It is a graph which shows the spectral characteristic of an antireflection film. It is a graph which shows the spectral characteristic of the antireflection film concerning a modification. It is a graph which shows the incident angle dependence of the spectral characteristics of the antireflection film concerning a modification. It is a graph which shows the spectral characteristic of the anti-reflective film produced with the prior art. It is a graph which shows the incident angle dependence of the spectral characteristic of the anti-reflective film produced with the prior art.

  Hereinafter, the photographing lens according to the embodiment of the present invention will be described. The following embodiments are only for facilitating understanding of the invention, and exclude additions and substitutions that can be performed by those skilled in the art without departing from the technical idea of the present invention. Is not intended.

  The photographing lens according to the present embodiment includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power. Composed. The first lens group has a negative meniscus lens having a concave surface closest to the image side on the object side, and an aperture stop between the first lens group and the second lens group. In addition, when the photographing lens of the present embodiment is focused from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups. Is configured to do.

  As described above, the photographing lens according to the present embodiment uses the third lens group having a negative refractive power to collect the light collected by the lens group having a positive refractive power by the first lens group and the second lens group. By receiving it, the total length is shortened, and the lens barrel mechanism is simplified.

  In addition, in the photographing lens according to the present embodiment, an antireflection film is provided on at least one of the optical surfaces in the first lens group, and the antireflection film includes at least one layer formed using a wet process. It is out. With this configuration, the photographic lens according to the present embodiment can further reduce ghosts and flares caused by reflection of light from an object on an optical surface, and can achieve high imaging performance. .

  In the photographing lens according to the present embodiment, it is desirable that the antireflection film is a multilayer film, and the layer formed by the wet process is the outermost layer among the layers constituting the multilayer film. In this way, since the difference in refractive index with air can be reduced, it is possible to reduce the reflection of light and further reduce ghosts and flares.

  In the photographing lens according to the present embodiment, it is desirable that the refractive index nd is 1.30 or less, where nd is the refractive index of the layer formed using the wet process. In this way, since the difference in refractive index with air can be reduced, it is possible to reduce the reflection of light and further reduce ghosts and flares.

  In the photographing lens according to the present embodiment, it is desirable that the optical surface is a concave surface when viewed from the aperture stop. Since a ghost is likely to occur on a concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on this optical surface.

  In the photographic lens according to the present embodiment, it is desirable that the concave surface when viewed from the aperture stop is a lens surface on the image plane side. Since a ghost is likely to occur on a concave lens surface with respect to the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the photographic lens according to the present embodiment, it is desirable that the concave surface when viewed from the aperture stop is a lens surface on the object side. Since a ghost is likely to occur on a concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the photographic lens according to the present embodiment, it is desirable that the concave surface when viewed from the aperture stop is the lens surface of the lens closest to the object side. Since a ghost is likely to occur on a concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the photographing lens according to the present embodiment, it is desirable that the concave surface when viewed from the aperture stop is the lens surface of the second lens from the lens closest to the object side to the image surface side. Since a ghost is likely to occur on a concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the photographing lens according to the present embodiment, the antireflection film is not limited to a wet process, and may be formed by a dry process or the like. At this time, it is preferable that the antireflection film includes at least one layer having a refractive index of 1.30 or less. Thus, even if the antireflection film is formed by a dry process or the like, the same effect as that obtained when the wet process is used can be obtained. At this time, the layer having a refractive index of 1.30 or less is preferably the most surface layer among the layers constituting the multilayer film.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (1).
(1) (−β) ≧ 0.50
Where β is the image magnification when focused on the closest object point.

  Conditional expression (1) is a conditional expression that defines the image magnification when the closest object point is focused. By satisfying conditional expression (1), the effect as a macro lens can be exhibited and various aberrations can be corrected well to achieve high imaging performance.

  If the lower limit of conditional expression (1) is not reached, the effect as a macro lens cannot be exhibited.

  By setting the lower limit of conditional expression (1) to 0.75, various aberrations can be corrected better, and the effects of the present invention can be made more reliable. Further, by setting the lower limit of conditional expression (1) to 1.00, various aberrations can be corrected more favorably, and the effects of the present invention can be further ensured.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (2).
(2) 0.07 <f2 / f1 <0.35
Here, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

  Conditional expression (2) is a conditional expression that defines the ratio between the focal length of the first lens group and the focal length of the second lens group. By satisfying conditional expression (2), a predetermined back focus and angle of view can be secured and high imaging performance can be achieved.

  Since the photographic lens of this embodiment is configured to receive the light collected by the first lens group and the second lens group by the third lens group having a negative refractive power in order to shorten the total length, the divergence of the rear side If the component is strong, it is difficult to obtain sufficient back focus. In view of this, in the present photographing lens, the modified Gaussian group composed of the first lens group and the second lens group configured as a lens group having a positive refractive power has a retrofocus effect, and satisfies the conditional expression (2). As described above, the back focus and the angle of view can be secured by balancing the focal lengths of the first lens group and the second lens group.

  If the upper limit of conditional expression (2) is exceeded, the distance between the second lens group and the third lens group at the time of focusing on infinity is too close, and the second lens group and the third lens group interfere with each other. Further, since the power of the first lens group becomes too strong, it becomes difficult to correct spherical aberration and image surface.

  By setting the upper limit value of conditional expression (2) to 0.30, spherical aberration correction and image plane correction can be performed more favorably, and the effects of the present invention can be further ensured. Further, by setting the upper limit of conditional expression (2) to 0.25, spherical aberration correction and image plane correction can be performed more satisfactorily, and the effects of the present invention can be further ensured.

  If the lower limit of conditional expression (2) is not reached, the focal length of the first lens group is too long, and the amount of movement of the focusing group (first lens group) during focusing increases. Alternatively, the focal length of the second lens group becomes too short and the spherical aberration increases.

  By setting the lower limit of conditional expression (2) to 0.09, spherical aberration can be corrected more favorably, and the effect of the present invention can be made more reliable. Further, by setting the lower limit of conditional expression (2) to 0.11, spherical aberration can be corrected more satisfactorily, and the effects of the present invention can be further ensured.

In the photographing lens according to the present embodiment, the first lens group includes, in order from the object side, a negative lens having a concave surface facing the image side, a first positive lens, and a second positive lens. It is desirable to satisfy conditional expression (3).
(3) 0.10 <Da / Db <2.00
Where Da is the distance on the optical axis between the most image side surface of the negative lens and the most object side surface of the first positive lens, and Db is the most image side surface of the first positive lens and the most of the second positive lens. This is the distance on the optical axis from the object side surface.

  Conditional expression (3) indicates that the air distance between the negative lens disposed closest to the object side in the first lens group and the first positive lens disposed on the image side, and the first positive lens and the image side thereof. It is the conditional expression which prescribed | regulated the appropriate ratio about ratio of the air space | interval with the arrange | positioned 2nd positive lens. Since the negative lens arranged closest to the object side in the first lens group is a negative meniscus lens having a shorter radius of curvature on the image side surface, off-axis rays emitted from the negative meniscus lens are separated from the optical axis. The larger the distance, the larger the declination and the greater the aberration that occurs. Therefore, it is necessary to cancel the large aberration due to the negative refractive power of the negative meniscus lens with the positive refractive power of the positive lens arranged as close as possible. In addition, it is possible to straighten the spherical aberration by ensuring a sufficient distance from the first positive lens to the second positive lens.

  When the upper limit of conditional expression (3) is exceeded, the distance between the first positive lens and the second positive lens is too close, and the burden on the object-side negative lens and the first positive lens that tries to maintain the angle of view increases. Therefore, it becomes difficult to correct various aberrations including spherical aberration.

  By setting the upper limit of conditional expression (3) to 1.25, various aberrations including spherical aberration can be corrected more favorably, and the effects of the present invention can be made more reliable. In addition, by setting the upper limit of conditional expression (3) to 1.00, various aberrations including spherical aberration can be corrected more satisfactorily, and the effects of the present invention can be further ensured.

  If the lower limit value of conditional expression (3) is not reached, the distance between the first positive lens and the second positive lens is too wide to balance the various aberrations from the object point at infinity to the object point at close distance. Correction becomes difficult.

  By setting the lower limit of conditional expression (3) to 0.25, various aberrations such as chromatic aberration of magnification can be corrected more favorably, and the effects of the present invention can be made more reliable. Further, by setting the lower limit of conditional expression (3) to 0.20, various aberrations such as chromatic aberration of magnification can be corrected more favorably, and the effects of the present invention can be further ensured.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (4).
(4) 0.40 <X1 / f <0.90
However, X1 is the absolute value of the amount of movement of the first lens unit on the optical axis when focusing from an infinite object point to a short distance object point, and f is the focal length of the entire system.

  Conditional expression (4) is a conditional expression that defines the absolute value of the amount of movement of the first lens unit from the object point at infinity to the object point at short distance with respect to the maximum total length of the photographing lens by the focal length of the entire photographing lens system. It is. By satisfying conditional expression (4), it is possible to achieve a macro lens having a short overall length, a light weight and high imaging performance.

  If the upper limit value of conditional expression (4) is exceeded, the overall length becomes long, heavy, and an optical system that takes a long time to feed out. Alternatively, the image magnification is too small with respect to the change amount of the total length, and the macro lens cannot be configured. In addition, since the distance between the second lens group and the third lens group is too wide at the time of focusing, it is difficult to correct astigmatism.

  By setting the upper limit of conditional expression (4) to 0.74, astigmatism can be corrected more favorably, and the effect of the present invention can be made more reliable.

  If the lower limit value of conditional expression (4) is not reached, the amount of change in the total length is small, but the refractive power of each lens unit increases accordingly, and the amount of aberration increases. In particular, correction of coma becomes difficult as the image magnification is increased. Note that by setting the lower limit of conditional expression (4) to 0.50, coma can be corrected more favorably, and the effects of the present invention can be made more reliable.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (5).
(5) 0.35 <f / TL <1.20
However, TL is the total length when focusing on infinity, and f is the focal length of the entire system.

  Conditional expression (5) is a conditional expression that prescribes an appropriate ratio between the total length at the time of focusing on infinity and the focal length of the entire system, which determines the length of the lens barrel at the time of contraction. By satisfying this conditional expression, the present photographic lens can satisfactorily correct various aberrations in all regions from the object point at infinity to the object point at close distance, and can achieve high imaging performance.

  If the upper limit value of conditional expression (5) is exceeded, the total length is too short, and it is difficult to correct aberrations well in all regions from an infinite object point to a short distance object point. Further, it is difficult to correct the image plane at the closest object point, and it is difficult to correct coma aberration as a whole. Note that by setting the upper limit value of conditional expression (5) to 0.51, coma aberration can be corrected more favorably in all regions from the object point at infinity to the object point at close distance, and the effect of the present invention can be achieved. It can be made more reliable.

  If the lower limit of conditional expression (5) is not reached, the total length is too long with respect to the focal length, and the first lens group and the third lens group are separated from each other, making it difficult to ensure a sufficient angle of view and brightness. It becomes. In addition, correction of spherical aberration becomes difficult. In addition, by setting the lower limit value of conditional expression (5) to 0.41, a sufficient angle of view and brightness can be secured, spherical aberration can be corrected more satisfactorily, and the effect of the present invention can be further ensured. it can.

In the photographing lens according to the present embodiment, the first lens group includes, in order from the object side, a negative lens having a concave surface facing the image side, and a positive lens, and satisfies the following conditional expression (6). It is desirable.
(6) 0.90 <(r2 + r1) / (r2-r1) <2.50
Here, r1 is the radius of curvature of the surface closest to the image side of the negative lens, and r2 is the radius of curvature of the surface closest to the object side of the positive lens.

  Conditional expression (6) is a conditional expression in which the air space between the negative lens and the positive lens included in the first lens group is considered as an air lens, and the shape of the air lens is represented by a shape factor expression. This air lens has a positive meniscus shape having a convex surface having a slightly large curvature on the object side and a concave surface having a small curvature on the image side. In this photographic lens, the light emitted from the negative lens located closest to the object is received by the positive meniscus air lens shown in the range of the conditional expression (6), so that the object lens is close to the object point. It is possible to satisfactorily correct the coma aberration by suppressing a rapid change in the angle of the light beam to the object point.

  When the upper limit of conditional expression (6) is exceeded, the radius of curvature r1 of the surface closest to the image side of the negative lens or the radius of curvature r2 of the surface closest to the object side of the positive lens is too short, and both interfere. Further, coma aberration increases when focusing from an infinite object point to a short-distance object point. By setting the upper limit of conditional expression (6) to 2.35, coma aberration when focusing from an infinite object point to a close object point can be corrected more favorably, and the effect of the present invention can be more reliably achieved. Can be. Further, by setting the upper limit value of conditional expression (6) to 2.10, coma aberration when focusing from an infinite object point to a short distance object point can be corrected more satisfactorily, and the effect of the present invention can be further ensured. Can be.

  If the lower limit of conditional expression (6) is not reached, the chromatic aberration on the axis of the g-line and the chromatic aberration of magnification deteriorate. By setting the lower limit of conditional expression (6) to 1.20, axial chromatic aberration and magnification chromatic aberration can be corrected more favorably, and the effect of the present invention can be made more reliable. Further, by setting the lower limit value of conditional expression (6) to 1.51, axial chromatic aberration and magnification chromatic aberration can be corrected more satisfactorily, and the effect of the present invention can be further ensured.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (7).
(7) 0.30 <f × (−β) / f2 <1.50
Where β is the image magnification when focusing on the closest object point, f is the focal length of the entire system, and f2 is the focal length of the second lens group.

  Conditional expression (7) is a conditional expression that defines an appropriate ratio of the focal length of the second lens group to the focal length of the entire system. By satisfying this conditional expression, the photographic lens can satisfactorily correct spherical aberration and coma and can achieve high imaging performance.

  If the upper limit of conditional expression (7) is exceeded, the focal length of the second lens group is too short, making it difficult to correct spherical aberration and coma. By setting the upper limit of conditional expression (7) to 1.40, spherical aberration and coma can be corrected more favorably, and the effects of the present invention can be made more reliable. Further, by setting the upper limit of conditional expression (7) to 1.30, spherical aberration and coma can be corrected more satisfactorily, and the effects of the present invention can be further ensured.

  If the lower limit value of conditional expression (7) is not reached, the focal length of the entire system is too short to ensure a working distance (distance between the lens surface closest to the object side of this photographing lens and the object point). . Further, a sufficient image magnification cannot be ensured and a macro lens cannot be constructed. In addition, it is difficult to satisfactorily correct chromatic aberration and off-axis aberration at the closest focus. By setting the lower limit value of conditional expression (7) to 0.50, the chromatic aberration and off-axis aberration at the closest focus can be corrected more favorably, and the effect of the present invention can be further ensured. Further, by setting the lower limit value of conditional expression (7) to 0.70, the chromatic aberration and off-axis aberration at the closest focus can be corrected more satisfactorily, and the effect of the present invention can be further ensured.

  In the photographic lens according to the present embodiment, the first lens group includes, in order from the object side, a negative lens having a concave surface facing the image side and a front lens group that includes a positive lens and has a negative refractive power in combination. It is desirable to form the rear group which is disposed on the image side of the front group and has a positive refractive power by synthesis. With this configuration, it is possible to suppress the incident height of off-axis rays in the first lens group, so it is possible to correct field angle-dependent aberrations such as coma and astigmatism, and to improve spherical aberration and the like in the second lens group. It can be corrected.

In addition, it is desirable that the first lens group configured of the front group and the rear group as described above satisfies the following conditional expressions (8) to (10).
(8) 0.05 <fp / (− fn) <0.60
(9) 0.04 <f / (− fn) <0.40
(10) 0.07 <f / fp <0.80
Here, fn is the focal length of the front group, fp is the focal length of the rear group, and f is the focal length of the entire system.

  Conditional expression (8) defines the ratio between the focal length of the front group and the focal length of the rear group of the first lens group. By satisfying conditional expression (8), the photographic lens can satisfactorily correct various aberrations and achieve high imaging performance.

  If the upper limit value of conditional expression (8) is exceeded, the power of the rear group of the first lens group becomes too strong, and the correction of spherical aberration becomes insufficient. In addition, the sensitivity of the lens position in manufacturing becomes strict, which is not preferable. By setting the upper limit value of conditional expression (8) to 0.50, spherical aberration can be corrected more satisfactorily and the effects of the present invention can be made more reliable. Further, by setting the upper limit of conditional expression (8) to 0.40, spherical aberration can be corrected more satisfactorily, and the effects of the present invention can be further ensured.

  If the lower limit of conditional expression (8) is not reached, the power of the front group of the first lens group is strong, and when the first lens group moves from an infinite object point to a short-distance object point, the incident angle and exit of the light beam This is not preferable because the angle changes greatly and it becomes difficult to balance aberrations over the entire focusing area such as coma aberration balance and field curvature fluctuation. By setting the lower limit value of conditional expression (8) to 0.07, coma aberration balance and field curvature fluctuation can be made better, and the effects of the present invention can be made more reliable. . Further, by setting the lower limit value of conditional expression (8) to 0.10, coma aberration balance and field curvature fluctuation can be further improved, and the effects of the present invention can be further ensured. .

  Conditional expression (9) is a conditional expression in which an appropriate ratio of the combined focal length of the front group of the first lens group is defined by the focal length of the entire system. By satisfying conditional expression (9), the photographic lens can satisfactorily correct various aberrations, and can achieve high imaging performance.

  If the upper limit of conditional expression (9) is exceeded, the refractive power of the front group of the first lens group is too strong with respect to the focal length of the entire system, and astigmatism short-range fluctuations cannot be suppressed. Further, since the Abbe number of the negative lens disposed closest to the object side in the first lens group tends to be small, it is difficult to correct chromatic aberration. In addition, the refractive power of the front group of the first lens group is strong, and when the first lens group moves from an infinite object point to a short-distance object point, the behavior of the incident angle and exit angle of the light beam changes greatly. It becomes difficult to correct chromatic aberration over the entire focal area.

  By setting the upper limit of conditional expression (9) to 0.30, chromatic aberration can be corrected more favorably, and the effects of the present invention can be made more reliable. Further, by setting the upper limit of conditional expression (9) to 0.20, chromatic aberration can be corrected more satisfactorily, and the effects of the present invention can be further ensured.

  If the lower limit value of conditional expression (9) is not reached, the refractive power of the front group of the first lens group is too weak with respect to the focal length of the entire system, the total length and the optical system become huge, and the amount of movement of the first lens group becomes large. It gets bigger. Further, when the refractive power of the front group of the first lens group is too weak with respect to the focal length of the entire system, coma aberration occurs in the light rays below the principal ray.

  Conditional expression (10) is a conditional expression in which an appropriate ratio of the combined focal length of the rear group of the first lens group is defined by the focal length of the entire system. By satisfying conditional expression (10), the photographic lens can satisfactorily correct various aberrations such as spherical aberration, and can achieve high imaging performance.

  If the upper limit of conditional expression (10) is exceeded, the refractive power of the rear group of the first lens group is too weak with respect to the focal length of the entire system, and spherical aberration and coma aberration cannot be suppressed. By setting the upper limit value of conditional expression (10) to 0.70, spherical aberration and coma aberration can be corrected more satisfactorily, and the effects of the present invention can be made more reliable. Further, by setting the upper limit value of conditional expression (10) to 0.60, spherical aberration and coma aberration can be corrected more satisfactorily, and the effects of the present invention can be further ensured.

  If the lower limit of conditional expression (10) is not reached, if the same focal length is maintained with the same total length, the front group of the first lens group becomes a lens group having positive refractive power, and the spherical aberration is curved. Further, the Petzval sum becomes too large, and the field curvature is displaced to the minus side. By setting the lower limit of conditional expression (10) to 0.15, spherical aberration and field curvature can be corrected more favorably, and the effects of the present invention can be made more reliable. Further, by setting the lower limit value of conditional expression (10) to 0.20, spherical aberration and field curvature can be corrected more satisfactorily, and the effects of the present invention can be further ensured.

  In the photographing lens according to the present embodiment, it is desirable that the third lens group has at least one negative lens and at least one positive lens. The third lens group is preferably composed of four or less lenses. Furthermore, it is desirable that the third lens group has a positive lens closest to the image side. With this configuration, when the light emitted from the second group is received by the positive lens, the exit pupil can be displaced toward the object side to ensure telecentricity, and coma aberration and the like can be easily corrected.

  In the photographing lens according to the present embodiment, it is desirable that the third lens group is fixed with respect to the image plane at the time of focusing. With this configuration, it is possible to correct coma aberration when focusing on a short-distance object point and simplify the configuration of the lens barrel.

  FIG. 10 is a schematic cross-sectional view of a digital single-lens reflex camera 1 (hereinafter simply referred to as a camera) as an optical apparatus provided with a photographic lens SL shown in a first embodiment described later. In this camera 1, light from an object (subject) (not shown) is collected by the taking lens 2 (shooting lens SL) and imaged on the focusing screen 4 via the quick return mirror 3. The light imaged on the focusing screen 4 is reflected a plurality of times in the pentaprism 5 and guided to the eyepiece lens 6. Thus, the photographer can observe the object (subject) image as an erect image through the eyepiece 6.

  Further, when a release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and light of an object (subject) (not shown) condensed by the photographing lens 2 is captured on the image sensor 7. Form an image. Thereby, the light from the object (subject) is captured by the image sensor 7 and recorded as an object (subject) image in a memory (not shown). In this way, the photographer can shoot an object (subject) with the camera 1. Note that the camera 1 shown in FIG. 10 may hold the photographic lens SL in a detachable manner, or may be formed integrally with the photographic lens SL. The camera 1 may be a so-called single-lens reflex camera or a compact camera (mirrorless camera) that does not have a quick return mirror or the like. The camera 1 can be mounted not only with the first embodiment described above but also with a photographic lens of another embodiment.

  Next, an outline of a method for manufacturing a photographic lens according to the present embodiment will be described with reference to FIG. First, each lens is arranged and a lens group is prepared (step S100). Specifically, in the present embodiment, for example, in the case of a first example described later, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a concave surface facing the image side, and a biconvex positive lens. L12, a biconvex positive lens L13, and a biconcave negative lens L14 are arranged. The second lens group G2 includes a cemented lens of a biconcave negative lens L21 and a biconvex positive lens L22, and a biconvex positive lens L23 in order from the object side. The third lens group G3 includes, in order from the object side, a negative meniscus lens L31 having a concave surface facing the image side and a positive meniscus lens L32 having a concave surface facing the object side. The aperture stop S is arranged between the first lens group G1 and the second lens group G2. The lens groups prepared in this manner are arranged in a lens barrel to manufacture the photographing lens SL.

  At this time, when focusing from an infinite object point to a short-distance object point, the first lens group G1 and the second lens group G2 are arranged so as to move to the object side while changing the distance between the lens groups. (Step S200). Thus, the production of the taking lens according to the present embodiment is completed.

(Example)
Hereinafter, each example according to the present embodiment will be described with reference to the accompanying drawings. 1, 4, 6, and 8 show the lens groups in the refractive power distribution and the change in the focal length state from the wide-angle end state (W) to the telephoto end state (T). The movement of is shown. In each figure, (a) shows each lens group in the wide-angle end state, (b) shows a lens group in the intermediate focal length state, and (c) shows a lens group in the telephoto end state. As shown in these drawings, the photographic lenses SL1 to SL4 of the respective examples are arranged in order from the object side, the first lens group G1 having a positive refractive power, the aperture stop S, and the second lens having a positive refractive power. The lens group G2 includes a third lens group G3 having negative refractive power. The first lens group G1 includes, in order from the object side, a front group G1F having a negative refractive power and a rear group G1R having a positive refractive power.

  In the first, third, and fourth embodiments, a spatial frequency equal to or higher than the limit resolution in a solid-state imaging device such as a CCD disposed on the image plane I between the third lens group G3 and the image plane I. Has a low-pass filter P1 for cutting.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangential plane of the apex of each aspheric surface to each aspheric surface at height y. Is S (y), r is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and An is the nth-order aspheric coefficient, and is expressed by the following equation (a). . In the following examples, “E−n” indicates “× 10 ⁻ⁿ ”.
(A) S (y) = (y ² / r) / {1+ (1−κ × y ² / r ² ) ^1/2 }
+ A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰

  In each embodiment, the secondary aspheric coefficient A2 is zero. In the table of each example, an aspherical surface is marked with * on the right side of the surface number.

[First embodiment]
FIG. 1 is a diagram illustrating a configuration of a photographic lens SL1 according to the first example. In the photographic lens SL1 of FIG. 1, the first lens group G1 has a positive refractive power as a whole, and in order from the object side, a front group G1F having a negative refractive power and a rear group G1R having a positive refractive power. It consists of and. The front group G1F is composed of two lenses, a negative meniscus lens L11 having a concave surface facing the image side and a biconvex positive lens L12 in order from the object side. The rear group G1R is in order from the object side. The lens is composed of two lenses, a biconvex positive lens L13 and a biconcave negative lens L14.

  The second lens group G2 has a positive refractive power as a whole, and in order from the object side, a cemented lens of a biconcave negative lens L21 and a biconvex positive lens L22, and a biconvex positive lens L23. It consists of three lenses.

  The third lens group G3 has a negative refractive power as a whole, and in order from the object side, there are two lenses, a negative meniscus lens L31 having a concave surface facing the image side and a positive meniscus lens L32 having a concave surface facing the object side. It consists of a lens.

  The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and when focusing from an infinite object point to a short-distance object point, together with the second lens group G2, is located on the object side. Moving.

  In the photographing lens SL1 according to the first example, an antireflection film to be described later is provided on the object side lens surface of the negative meniscus lens L11 of the first lens group G1 and the object side lens surface of the biconvex positive lens L12. Is formed.

  Table 1 below lists values of specifications of the photographing lens SL1 according to the first example. In Table 1 (lens surface data), the surface number indicates the order of the lens surfaces from the object side along the light traveling direction, and the surface interval is the interval on the optical axis from each optical surface to the next optical surface. The refractive index and the Abbe number indicate values for the d-line (λ = 587.6 nm), respectively.

In (aspherical surface data), κ represents a conic constant, and An represents an nth-order aspherical coefficient. “E-n” indicates “× 10 ⁻ⁿ ”. In (various data), f is the focal length, FNO is the F number, Bf is the distance from the image side surface of the optical element disposed closest to the image side to the image plane I, and 2ω is the angle of view (unit: unit). °) respectively.

  Further, (variable interval data) indicates variable intervals in the infinitely focused state, the imaging magnification (β) −0.5 times state, and the imaging magnification (β) −1.0 times state. In addition, the total length, the total air conversion length, and the air conversion Bf (the air conversion value of the distance from the image side surface of the optical element having the refractive power arranged closest to the image side) to the image plane are shown. The total length represents the distance on the optical axis from the first surface of the lens surface to the image plane I when focusing on infinity. D0 is the axial air gap between the object and the first lens group G1, d1a is the axial air gap between the first lens group G1 and the aperture stop S, and d1b is the distance between the aperture stop S and the second lens group G2. On-axis air spacing, d2 represents on-axis air spacing between the second lens group G2 and the third lens group G3. Further, the axial air gap d1 between the first lens group G1 and the second lens group G2 is expressed by d1 = d1a + d1b.

  In (corresponding value of conditional expression), β is the maximum photographing magnification, f1 is the focal length of the first lens group G1, f2 is the focal length of the second lens group G2, and Da is the negative value of the first lens group G1. The distance on the optical axis between the most image side surface of the meniscus lens L11 and the most object side surface of the biconvex lens L12, and Db is the most image side surface of the biconvex lens L12 and the most object side surface of the biconvex lens L13. , F is the focal length of the entire system, X1 is the absolute value of the amount of movement of the first lens group G1 on the optical axis when focusing from infinity to a short-distance object point, and TL is The total length at the time of focusing on infinity, r1 is the radius of curvature of the surface closest to the image side of the negative meniscus lens L11, r2 is the radius of curvature of the surface closest to the object side of the biconvex lens L12, and fn is the focal length of the front group G1F. Fp represents the focal length of the rear group G1R.

  The unit of focal length, curvature radius, surface interval, and other lengths listed in all the following specifications is generally “mm”, but the optical system may be proportionally enlarged or reduced. Since equivalent optical performance can be obtained, the present invention is not limited to this. The curvature radius “∞” indicates a plane, and the refractive index of air 1.000 is omitted. The explanation of these symbols and the description of the specification table are the same in the following examples, and the explanation in the following examples is omitted.

(Table 1) First Example

(Lens surface data)
Surface number Curvature radius Surface spacing Abbe number Refractive index surface ∞ ∞
1 177.4342 2.000 70.40 1.48749
2 15.9007 3.530
3 63.8566 5.000 40.77 1.80604
4 -72.9715 6.961
5 31.3195 5.000 58.73 1.61272
6 -25.7820 0.678
7 -40.2105 2.000 37.00 1.61293
8 23.7239 (d1a)
9 (Aperture) ∞ (d1b)
10 -13.8798 1.200 37.00 1.61293
11 186.0079 3.710 60.29 1.62041
12 -18.9606 0.100
13 80.2528 3.445 63.73 1.61881
14 * -25.3622 (d2)
15 -311.9251 1.200 70.40 1.48749
16 31.2577 1.550
17 -1620.7830 2.550 44.79 1.74400
18 -66.5158 0.100
19 0.0000 2.000 64.12 1.51680
20 0.0000 (Bf)
Image plane ∞

(Aspheric data)
Surface 14 κ = 0.3210
A4 = 4.54813E-06
A6 = 5.40478E-09
A8 = -5.17090E-12
A10 = 5.14254E-15

(Various data)
f = 40.00
Bf = 37.65 (constant)
F.NO = 2.68
2ω = 39.0 °

(Variable interval data)
β Infinity -0.5 times -1.0 times
d0 80.4055 38.9287
d1a 2.96840 3.21650 5.33230
d1b 4.00000 4.00000 4.00000
d1 6.96840 7.21650 9.33230
d2 1.21000 13.37100 25.70880
Total length 86.85516 99.26436 113.71791
Total air equivalent 86.17372 98.58293 113.03648
Air conversion Bf 36.97047 36.97047 36.97047

(Values for conditional expressions)
(1) (-β) = 1.000
(2) f2 / f1 = 0.154
(3) Da / Db = 0.507
(4) X1 / f = 0.672
(5) f / TL = 0.461
(6) (r2 + r1) / (r2-r1) = 1.663
(7) f × (−β) /f2=1.173
(8) fp / (− fn) = 0.273
(9) f / (− fn) = 0.059
(10) f / fp = 0.215

  2A and 2B show various aberration diagrams of the taking lens SL1 according to the first example, in which FIG. 2A is an aberration diagram in an infinitely focused state, and FIG. 2B is an imaging magnification of −0.5 times. Various aberrations are shown. (C) shows various aberrations when the imaging magnification is -1.0 times. In each aberration diagram, FNO is an F number, Y is an image height, d is an aberration curve for the d-line (λ = 587.6 nm), and g is an aberration curve for the g-line (λ = 435.8 nm). Show. The spherical aberration diagram shows the F-number corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum value of the image height Y, and the coma diagram shows the value of each image height. In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. The description of this aberration diagram is the same in the following examples.

  As is apparent from the respective aberration diagrams, the photographic lens SL1 according to the first example has excellent imaging performance with various aberrations corrected well from the infinity in-focus state to the close-up photographing state. I understand that.

  FIG. 3 shows a state where a ghost is generated by the light beam BM incident from the object side in the photographing lens SL1 of the first embodiment. In FIG. 3, when a light beam BM from the object side is incident on the photographing lens SL1 as shown in the drawing, the object side lens surface (the first ghost generation surface and its surface number is 3) in the biconvex positive lens L12. The reflected light is reflected again by the object-side lens surface of the negative meniscus lens L11 (the second ghost generating surface, whose surface number is 1) and reaches the image surface I to generate a ghost. I will let you. The first ghost generation surface (surface number 3) and the second ghost generation surface (surface number 1) are concave lens surfaces with respect to the aperture stop. A ghost can be effectively reduced by forming an antireflection film corresponding to a wide incident angle in a wider wavelength range on such a surface.

[Second Embodiment]
FIG. 4 is a diagram illustrating a configuration of the photographic lens SL2 according to the second embodiment. In the photographic lens SL2 of FIG. 4, the first lens group G1 has a positive refractive power as a whole, and in order from the object side, a front group G1F having a negative refractive power and a rear group having a positive refractive power. And G1R. The front group G1F is composed of two lenses, a negative meniscus lens L11 having a concave surface facing the image side and a biconvex positive lens L12 in order from the object side. The rear group G1R is in order from the object side. The lens is composed of two lenses, a biconvex positive lens L13 and a biconcave negative lens L14.

  The second lens group G2 has a positive refractive power as a whole, and in order from the object side, a cemented lens of a biconcave negative lens L21 and a biconvex positive lens L22, and a biconvex positive lens L23. It consists of three lenses.

  The third lens group G3 has a negative refracting power as a whole, and in order from the object side, a biconcave negative lens L31, a biconcave negative lens L32, and a biconvex positive lens L33. It is made up of lenses.

  The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and when focusing from an infinite object point to a short-distance object point, together with the second lens group G2, is located on the object side. Moving.

  In the photographic lens SL2 according to the second embodiment, an antireflection film, which will be described later, is provided on the image side lens surface of the negative meniscus lens L11 of the first lens group G1 and the object side lens surface of the biconvex positive lens L12. Is formed.

  Table 2 below provides values of specifications of the photographic lens SL2 according to the second example.

(Table 2) Second Example

(Lens surface data)
Surface number Curvature radius Surface spacing Abbe number Refractive index surface ∞ ∞
1 38.6400 1.200 60.29 1.62041
2 14.6115 4.088
3 67.4515 2.559 27.51 1.75520
4 -68.1015 7.094
5 29.5588 4.303 57.03 1.62280
6 -24.8308 0.174
7 -48.5997 1.200 33.80 1.64769
8 22.1617 (d1a)
9 (Aperture) ∞ (d1b)
10 -13.9430 1.200 33.80 1.64769
11 36.8604 4.373 48.08 1.70000
12 -22.4714 0.100
13 81.7598 3.741 60.29 1.62041
14 * -22.1829 (d2)
15 -86.3137 1.200 61.15 1.58887
16 26.6709 1.973
17 -92.6459 1.200 39.22 1.59551
18 71.2964 0.100
19 43.7866 4.727 44.79 1.74400
20 -42.6411 (Bf)
Image plane ∞

(Aspheric data)
14th page
κ = 0.3963
A4 = 9.62328E-06
A6 = 9.25444E-09
A8 = 1.06569E-11
A10 = 0.00000E + 00

(Various data)
f = 40.00
Bf = 42.10 (constant)
F.NO = 2.80
2ω = 39.2 °

(Variable interval data)
β Infinity -0.5 times -1.0 times
d0 80.7078 39.5433
d1a 1.70000 2.56538 4.17576
d1b 3.05000 3.05000 3.05000
d1 4.75000 5.61538 7.22576
d2 1.00000 10.95186 21.03119
Total length 87.08321 97.90046 109.59017
Total air equivalent 87.08321 97.90046 109.59017
Air conversion Bf 42.10051 42.10051 42.10051

(Values for conditional expressions)
(1) (-β) = 1.000
(2) (f2 / f1) = 0.154
(3) Da / Db = 0.576
(4) X1 / f = 0.563
(5) f / TL = 0.459
(6) (r2 + r1) / (r2-r1) = 1.553
(7) f × (−β) /f2=1.270
(8) fp / (− fn) = 0.232
(9) f / (− fn) = 0.052
(10) f / fp = 0.224

  5A and 5B show various aberration diagrams of the taking lens SL2 according to the second example, where FIG. 5A is an aberration diagram in an infinitely focused state, and FIG. 5B is an imaging magnification of −0.5 times. (C) shows various aberrations when the imaging magnification is -1.0 times. As is apparent from the respective aberration diagrams, the photographic lens SL2 according to the second example has excellent imaging performance with various aberrations corrected well from the infinite focus state to the close-up state. Recognize.

[Third embodiment]
FIG. 6 is a diagram illustrating a configuration of the photographic lens SL3 according to the third example. In the photographic lens SL3 of FIG. 6, the first lens group G1 has a positive refractive power as a whole, and in order from the object side, a front group G1F having a negative refractive power and a rear group G1R having a positive refractive power. It consists of and. The front group G1F is composed of two lenses, a negative meniscus lens L11 having a concave surface facing the image side and a biconvex positive lens L12 in order from the object side. The rear group G1R is in order from the object side. , And a biconvex positive lens L13 and a biconcave negative lens L14.

  The second lens group G2 has a positive refractive power as a whole, and in order from the object side, a cemented lens of a biconcave negative lens L21 and a biconvex positive lens L22, and a biconvex positive lens L23. It consists of three lenses.

  The third lens group G3 has a negative refractive power as a whole, and is composed of two lenses, a negative meniscus lens L31 having a concave surface directed toward the image side and a biconvex positive lens L32 in order from the object side. ing.

  The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and when focusing from an infinite object point to a short-distance object point, together with the first lens group G1, is located on the object side. Moving.

  In the photographic lens SL3 according to the third example, an antireflection film to be described later is formed on both the image side lens surface and the object side lens surface of the negative meniscus lens L11 of the first lens group G1. Yes.

  Table 3 below lists values of specifications of the photographing lens SL3 according to the third example.

(Table 3) Third Example

(Lens surface data)
Surface number Curvature radius Surface spacing Abbe number Refractive index surface ∞ ∞
1 66.2716 1.418 59.84 1.52249
2 13.9775 2.100
3 43.7571 3.136 34.96 1.80 100
4 -94.4864 6.897
5 27.6455 3.505 44.79 1.74400
6 -25.2375 0.110
7 -38.5571 1.084 33.79 1.64769
8 18.4448 (d1a)
9 (Aperture) ∞ (d1b)
10 -15.8877 2.788 32.11 1.67270
11 42.6316 5.000 50.70 1.67790
12 -23.9294 0.280
13 81.7271 3.504 61.18 1.58913
14 * -23.6977 (d2)
15 1153.7120 1.001 64.12 1.51680
16 33.6937 1.274
17 37757.7137 2.795 35.92 1.66446
18 -82.6158 0.100
19 0.0000 2.000 64.12 1.51680
20 0.0000 (Bf)
Image plane ∞

(Aspheric data)
14th page
κ = 0.2972
A4 = 4.92425E-06
A6 = 7.19036E-09
A8 = -6.48152E-11
A10 = 1.69010E-13

(Various data)
f = 39.28
Bf = 37.40 (constant)
F.NO = 2.89
2ω = 39.9 °

(Variable interval data)
β Infinity -0.5 times -1.0 times
d0 80.3134 39.4435
d1a 2.09400 2.09400 2.09400
d1b 3.50000 4.80603 6.87863
d1 5.59400 6.90003 8.97263
d2 1.00000 12.75385 24.77361
Total length 80.98205 94.04193 108.13429
Air equivalent total length 80.30062 93.36050 107.45286
Air conversion Bf 38.81447 38.81447 38.81447

(Values for conditional expressions)
(1) (-β) = 1.000
(2) (f2 / f1) = 0.217
(3) Da / Db = 0.305
(4) X1 / f = 0.691
(5) f / TL = 0.485
(6) (r2 + r1) / (r2-r1) = 1.939
(7) f × (−β) /f2=1.183
(8) fp / (− fn) = 0.122
(9) f / (− fn) = 0.033
(10) f / fp = 0.271

  FIG. 7 shows various aberration diagrams of the photographic lens SL3 according to the third example. (A) is an aberration diagram in the infinitely focused state, and (b) is an imaging magnification of −0.5 times. Various aberrations are shown. (C) shows various aberrations when the imaging magnification is -1.0 times. As is apparent from each aberration diagram, the photographic lens SL3 according to the third example has excellent imaging performance with various aberrations corrected well from the infinite focus state to the close-up state. I understand that.

[Fourth embodiment]
FIG. 8 is a diagram illustrating a configuration of the photographic lens SL4 according to the fourth example. In the photographing lens SL4 of FIG. 8, the first lens group G1 has a positive refractive power as a whole, and in order from the object side, a front group G1F having a negative refractive power and a rear group G1R having a positive refractive power. It consists of and. The front group G1F is composed of two lenses, a negative meniscus lens L11 having a concave surface facing the image side and a biconvex positive lens L12 in order from the object side. The rear group G1R is in order from the object side. And a biconvex positive lens L13 and a biconcave negative lens L14.

  The second lens group G2 has a positive refractive power as a whole, and in order from the object side, a biconcave negative lens L21, a positive meniscus lens L22 having a convex surface facing the image side, and a biconvex positive lens It consists of three lenses of L23.

  The third lens group G3 has a negative refractive power as a whole, and is composed of two lenses, a negative meniscus lens L31 having a concave surface directed toward the image side and a biconvex positive lens L32 in order from the object side. ing.

  The aperture stop S is disposed between the first lens group 1 and the second lens group G2, and when focusing from an infinite object point to a short-distance object point, together with the second lens group G2, is located on the object side. Moving.

  In the photographic lens SL4 according to the fourth example, an antireflection film, which will be described later, is provided on the image side lens surface of the negative meniscus lens L11 of the first lens group G1 and the object side lens surface of the biconvex positive lens L12. Is formed.

  Table 4 below provides values of specifications of the photographing lens SL4 according to the fourth example.

(Table 4) Fourth Example

(Lens surface data)
Surface number Curvature radius Surface spacing Abbe number Refractive index surface ∞ ∞
1 51.6845 2.000 70.45 1.48749
2 13.3424 2.400
3 72.5939 3.800 34.96 1.80100
4 -77.4442 6.714
5 26.8652 3.700 44.79 1.74400
6 -25.5925 0.305
7 -36.0893 1.004 33.79 1.64769
8 21.4639 (d1a)
9 (Aperture) ∞ (d1b)
10 -21.4083 4.500 30.13 1.69895
11 62.1356 0.800
12 -182.0364 3.338 56.17 1.65100
13 -21.2614 0.567
14 45.8709 5.000 65.44 1.60300
15 -30.2914 (d2)
16 111.1120 0.996 54.00 1.61720
17 30.8981 1.100
18 261.1151 2.866 27.51 1.75520
19 -181.5345 0.100
20 0.0000 2.000 64.12 1.51680
21 0.0000 (Bf)
Image plane ∞

(Various data)
f = 39.57
Bf = 37.89 (constant)
F.NO = 2.89
2ω = 39.6 °

(Variable interval data)
β Infinity -0.5 times -1.0 times
d0 79.5612 38.8435
d1a 2.50442 3.41171 5.25214
d1b 2.35000 2.35000 2.35000
d1 4.85442 5.76171 7.60214
d2 1.00000 12.52131 24.29696
Total length 84.93454 97.36315 110.97925
Air equivalent total length 84.25310 96.68171 110.29781
Air conversion Bf 39.30979 39.30979 39.30979

(Values for conditional expressions)
(1) (-β) = 1.000
(2) (f2 / f1) = 0.291
(3) Da / Db = 0.357
(4) X1 / f = 0.663
(5) f / TL = 0.463
(6) (r2 + r1) / (r2-r1) = 1.450
(7) f × (−β) /f2=1.131
(8) fp / (− fn) = 0.341
(9) f / (− fn) = 0.151
(10) f / fp = 0.443

  FIG. 9 shows various aberration diagrams of the taking lens SL4 according to the fourth example. (A) is an aberration diagram in the infinitely focused state, and (b) is an imaging magnification of −0.5 times. Various aberrations are shown. (C) shows various aberrations when the imaging magnification is -1.0 times. As is apparent from each aberration diagram, the photographic lens SL4 according to the fourth example has excellent imaging performance with various aberrations corrected well from the infinite focus state to the close-up state. I understand that.

  Next, an antireflection film (also referred to as a multilayer broadband antireflection film) used for the photographing lenses SL1 to SL4 (hereinafter collectively referred to as SL) according to the embodiment will be described. FIG. 12 is a diagram illustrating an example of a film configuration of the antireflection film. The antireflection film 101 is composed of seven layers and is formed on the optical surface of the optical member 102 such as a lens. The first layer 101a is formed of aluminum oxide deposited by a vacuum deposition method. Further, a second layer 101b made of a mixture of titanium oxide and zirconium oxide deposited by a vacuum deposition method is further formed on the first layer 101a. Further, a third layer 101c made of aluminum oxide deposited by a vacuum deposition method is formed on the second layer 101b, and titanium oxide and zirconium oxide deposited by a vacuum deposition method are formed on the third layer 101c. A fourth layer 101d made of the mixture is formed. Furthermore, a fifth layer 101e made of aluminum oxide deposited by vacuum deposition is formed on the fourth layer 101d, and titanium oxide and zirconium oxide deposited by vacuum deposition on the fifth layer 101e. A sixth layer 101f made of the mixture is formed.

  Then, a seventh layer 101g made of a mixture of magnesium fluoride and silica is formed on the sixth layer 101f formed in this way by a wet process, and the antireflection film 101 of this embodiment is formed. For the formation of the seventh layer 101g, a sol-gel method which is a kind of wet process is used. The sol-gel method is a method in which a sol obtained by mixing raw materials is made into a non-flowable gel by hydrolysis / polycondensation reaction, etc., and this gel is heated and decomposed to obtain a product, In the production of an optical thin film, a film can be formed by applying an optical thin film material sol on the optical surface of an optical member and forming a gel film by drying and solidifying. The wet process is not limited to the sol-gel method, and a method of obtaining a solid film without going through a gel state may be used.

Thus, the first layer 101a to the sixth layer 101f of the antireflection film 101 are formed by electron beam evaporation which is a dry process, and the seventh layer 101g which is the uppermost layer is prepared by a hydrofluoric acid / magnesium acetate method. It is formed by the following procedure by a wet process using the prepared sol solution. First, an aluminum oxide layer to be the first layer 101a, a titanium oxide-zirconium oxide mixed layer to be the second layer 101b, a third layer on the lens film formation surface (the optical surface of the optical member 102 described above) in advance using a vacuum deposition apparatus, An aluminum oxide layer to be the layer 101c, a titanium oxide-zirconium oxide mixed layer to be the fourth layer 101d, an aluminum oxide layer to be the fifth layer 101e, and a titanium oxide-zirconium oxide mixed layer to be the sixth layer 101f are formed in this order. And after taking out the optical member 102 from a vapor deposition apparatus, the thing which added the silicon alkoxide to the sol liquid prepared by the hydrofluoric acid / magnesium acetate method is apply | coated by the spin coat method, The magnesium fluoride used as the 7th layer 101g A layer made of a mixture of silica and silica is formed. The reaction formula when prepared by the hydrofluoric acid / magnesium acetate method is shown in the following formula (b).
(B) 2HF + Mg (CH3COO) 2 → MgF2 + 2 + CH3COOH

  The sol solution used for the film formation is used for film formation after mixing raw materials and subjecting to an autoclave at 140 ° C. for 24 hours at a high temperature and pressure. The optical member 102 is completed by heat treatment at 160 ° C. for 1 hour in the air after the seventh layer 101g is formed. By using such a sol-gel method, the seventh layer 101g is formed by depositing particles having a size of several nm to several tens of nm leaving a void.

  The optical performance of the optical member having the antireflection film 101 formed in this way will be described using the spectral characteristics shown in FIG.

  The optical member (lens) having the antireflection film according to this embodiment is formed under the conditions shown in Table 5 below. Here, Table 5 shows that the reference wavelength is λ, and the layers 101a (first layer) to 101g (seventh layer) of the antireflection film 101 when the refractive index (optical member) of the substrate is 1.62, 1.74, and 1.85. The optical film thickness of each layer is determined. In Table 5, aluminum oxide is represented by Al2O3, a mixture of titanium oxide and zirconium oxide is represented by ZrO2 + TiO2, and a mixture of magnesium fluoride and silica is represented by MgF2 + SiO2.

  FIG. 13 shows spectral characteristics when light rays are perpendicularly incident on an optical member in which the reference wavelength λ is 550 nm in Table 5 and the optical film thickness of each layer of the antireflection film 101 is designed.

  From FIG. 13, it can be seen that the optical member having the antireflection film 101 designed with the reference wavelength λ of 550 nm can suppress the reflectance to 0.2% or less over the entire wavelength range of 420 nm to 720 nm. Further, even in the optical member having the antireflection film 101 in which each optical film thickness is designed with the reference wavelength λ as the d-line (wavelength 587.6 nm) in Table 5, the spectral characteristics are hardly affected, and the reference shown in FIG. It is known that the spectral characteristics are almost the same as when the wavelength λ is 550 nm.

(Table 5)
Substance Refractive index Optical film thickness Optical film thickness Optical film thickness
Medium air 1
7th layer MgF2 + SiO2 1.26 0.268λ 0.271λ 0.269λ
6th layer ZrO2 + TiO2 2.12 0.057λ 0.054λ 0.059λ
5th layer Al2O3 1.65 0.171λ 0.178λ 0.162λ
4th layer ZrO2 + TiO2 2.12 0.127λ 0.13λ 0.158λ
3rd layer Al2O3 1.65 0.122λ 0.107λ 0.08λ
Second layer ZrO2 + TiO2 2.12 0.059λ 0.075λ 0.105λ
1st layer Al2O3 1.65 0.257λ 0.03λ 0.03λ
Refractive index of substrate 1.62 1.74 1.85

  Next, a modified example of the antireflection film will be described. This antireflection film is composed of five layers, and similarly to Table 5, the optical film thickness of each layer with respect to the reference wavelength λ is designed under the conditions shown in Table 6 below. In this modification, the above-described sol-gel method is used for forming the fifth layer.

  FIG. 14 shows the spectral characteristics in Table 6 when light rays are perpendicularly incident on an optical member having an antireflection film with a refractive index of the substrate of 1.52 and a reference wavelength λ of 550 nm and each optical film thickness designed. Yes. From FIG. 14, it can be seen that the antireflection film of this modification has a reflectivity of 0.2% or less over the entire wavelength range of 420 nm to 720 nm. In Table 6, even an optical member having an antireflection film whose optical film thickness is designed with the reference wavelength λ as the d-line (wavelength 587.6 nm) hardly affects the spectral characteristics, and the spectral characteristics shown in FIG. It is known that it has almost the same characteristics.

  FIG. 15 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 14 are 30, 45, and 60 degrees, respectively. 14 and 15 do not show the spectral characteristics of the optical member having the antireflection film whose refractive index is 1.46 shown in Table 6, but the refractive index of the substrate is almost equal to 1.52. It is known that it has the following spectral characteristics.

(Table 6)
Material Refractive index Optical film thickness Optical film thickness Medium Air 1
5th layer MgF2 + SiO2 1.26 0.275λ 0.269λ
4th layer ZrO2 + TiO2 2.12 0.045λ 0.043λ
3rd layer Al2O3 1.65 0.212λ 0.217λ
Second layer ZrO2 + TiO2 2.12 0.077λ 0.066λ
1st layer Al2O3 1.65 0.288λ 0.290λ
Refractive index of substrate 1.46 1.52

  For comparison, FIG. 16 shows an example of an antireflection film formed only by a dry process such as a conventional vacuum deposition method. FIG. 16 shows the spectral characteristics when a light beam is perpendicularly incident on an optical member designed with an antireflection film configured under the conditions shown in Table 7 below at a refractive index of 1.52 of the same substrate as in Table 6. FIG. 17 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 16 are 30, 45, and 60 degrees, respectively.

(Table 7)
Material Refractive index Optical film thickness Medium Air 1
7th layer MgF2 1.39 0.243λ
6th layer ZrO2 + TiO2 2.12 0.119λ
5th layer Al2O3 1.65 0.057λ
4th layer ZrO2 + TiO2 2.12 0.220λ
3rd layer Al2O3 1.65 0.064λ
Second layer ZrO2 + TiO2 2.12 0.057λ
1st layer Al2O3 1.65 0.193λ
Refractive index of substrate 1.52

  When comparing the spectral characteristics of the optical member having the antireflection film according to the present embodiment shown in FIGS. 13 to 15 with the spectral characteristics of the conventional example shown in FIGS. 16 and 17, the antireflection film has any incidence. It can be seen that the corner also has a lower reflectivity and has a lower reflectivity over a wider band.

  Next, an example in which the antireflection films shown in Tables 5 and 6 are applied to the first to fourth examples described above will be described.

  In the photographing lens SL1 of the first example, the refractive index of the negative meniscus lens L11 of the first lens group G1 is nd = 1.48749 as shown in Table 1, and the biconvex shape of the first lens group G1. Since the refractive index of the positive lens L12 is nd = 1.80604, the antireflection film 101 (see Table 6) corresponding to the refractive index of the substrate of 1.46 is provided on the object-side lens surface of the negative meniscus lens L11. The reflection light from each lens surface can be reduced by using an antireflection film (see Table 5) corresponding to the refractive index of the substrate of 1.85 on the object-side lens surface of the biconvex positive lens L12. , Ghosting and flare can be reduced.

  In the photographic lens SL2 of the second example, the refractive index of the negative meniscus lens L11 of the first lens group G1 is nd = 1.62041 as shown in Table 2, and both of the first lens group G1. Since the refractive index of the convex positive lens L12 is nd = 1.75520, the antireflective film 101 corresponding to the refractive index of the substrate of 1.62 on the image side lens surface of the negative meniscus lens L11 (Table 5). And an antireflection film (see Table 5) corresponding to a refractive index of the substrate of 1.74 is used on the object-side lens surface of the biconvex positive lens L12. , And ghost and flare can be reduced.

  In the photographic lens SL3 of the third example, since the refractive index of the negative meniscus lens L11 of the first lens group G1 is nd = 1.52249 as shown in Table 3, the image in the negative meniscus lens L11 By using anti-reflective coatings (see Table 6) with a substrate refractive index of 1.52 on both the lens and object side lens surfaces, the reflected light from each lens surface can be reduced, reducing ghosts and flares. can do.

  In the photographic lens SL4 of the fourth example, the refractive index of the negative meniscus lens L11 of the first lens group G1 is nd = 1.48749 as shown in Table 4, and both of the first lens group G1 Since the refractive index of the convex positive lens L12 is nd = 1.80100, the antireflective film 101 (Table 6) has a refractive index of the substrate corresponding to 1.46 on the image-side lens surface of the negative meniscus lens L11. Reflection) from each lens surface by using an antireflection film 101 (see Table 5) corresponding to a refractive index of the substrate of 1.85 on the object-side lens surface of the biconvex positive lens L12. Light can be reduced, and ghost and flare can be reduced.

  In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

  In the above description and the embodiments described below, the three-group configuration is shown, but the present invention can also be applied to other group configurations such as the fourth group, the fifth group, and the like. Further, a configuration in which a lens or a lens group is added on the object side or a configuration in which a lens or a lens group is added on the most image side may be used. The lens group refers to a portion having at least one lens separated by an air interval that changes during zooming.

  In addition, a single lens group or a plurality of lens groups, or a partial lens group may be moved along the optical axis to be a focusing lens group that performs focusing from an object at infinity to a near object. In this case, the focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (such as an ultrasonic motor). In particular, it is desirable that the first lens group G1 or the second lens group G2 be a focusing lens group.

  Image stabilization that corrects image blur caused by camera shake by moving the lens group or partial lens group so as to have a component perpendicular to the optical axis, or by rotating (swinging) the lens group or partial lens group in the in-plane direction including the optical axis It may be a lens group. In particular, it is preferable that at least a part of the second lens group G2 or the third lens group G3 is an anti-vibration lens group.

  Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. It is preferable that the lens surface is a spherical surface or a flat surface because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment is prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. In addition, when the lens surface is aspheric, this aspherical surface is an aspherical surface by grinding, a glass mold aspherical surface made of glass with an aspherical shape, and a composite type in which resin is formed on the glass surface in an aspherical shape. Any aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  As described above, the aperture stop S is preferably disposed between the first lens group G1 and the second lens group G2, but instead of providing a member as an aperture stop, the role of the lens diaphragm is substituted. You may do it.

  In the photographic lens SL of the present embodiment, it is preferable that the first lens group G1 has two positive lens components and two negative lens components. In the first lens group G1, it is preferable to dispose the lens components in the order of negative, positive and negative in order from the object side with an air gap interposed therebetween. In the photographic lens SL of the present embodiment, it is preferable that the second lens group G2 has two positive lens components. Alternatively, in the photographic lens SL of the present embodiment, it is preferable that the second lens group G2 has one positive lens component and one negative lens component. In the photographic lens SL of the present embodiment, it is preferable that the third lens group G3 has one positive lens component and one negative lens component. In the third lens group G3, it is preferable to dispose the lens components in the order of negative and positive in order from the object side with an air gap interposed therebetween.

  In addition, in order to explain the present invention in an easy-to-understand manner, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.

  As described above, according to the present invention, it is possible to further reduce ghosts and flares, maintain a sufficient back focus while maintaining a sufficient angle of view, simplify the configuration of the lens barrel, and reduce the overall length and movement amount. It is possible to provide a photographing lens that can be used, an optical apparatus including the same, and a manufacturing method.

SL (SL1 to SL4) Shooting lens G1 First lens group G2 Second lens group G3 Third lens group G1F Front group
G1R Rear group S Aperture stop 1 Electronic still camera (optical equipment)
101 Antireflection film 101a 1st layer 101b 2nd layer 101c 3rd layer 101d 4th layer 101e 5th layer 101f 6th layer 101g 7th layer 102 Optical member

Claims (27)

From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups ,
The first lens group includes, in order from the object side, a negative meniscus lens disposed closest to the object side and having a concave surface facing the image side, a first positive lens, and a second positive lens .
An aperture stop is provided between the first lens group and the second lens group;
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
A photographic lens characterized by satisfying the following conditions .
0.10 <Da / Db <1.25
However,
Da: a distance on the optical axis between the most image side surface of the negative meniscus lens and the most object side surface of the first positive lens;
Db: Distance on the optical axis between the most image side surface of the first positive lens and the most object side surface of the second positive lens. From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups ,
The first lens group includes a negative meniscus lens having a concave surface facing the image side closest to the object side,
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
A photographic lens characterized by satisfying the following conditions .
0.40 <X1 / f <0.90
However,
X1: absolute value of the amount of movement of the first lens unit on the optical axis when focusing from an infinite object point to the closest object point;
f: Focal length of the entire system. From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups ,
The first lens group includes a negative meniscus lens having a concave surface facing the image side closest to the object side,
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
A photographic lens characterized by satisfying the following conditions .
0.35 <f / TL <1.20
However,
TL: Total length when focusing on infinity,
f: Focal length of the entire system. From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups ,
The first lens group includes a negative meniscus lens that is disposed closest to the object side and has a concave surface facing the image side, and a positive lens that has a negative refractive power in combination, and an image side of the front group And a rear group having a positive refractive power in combination , and
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
A photographic lens characterized by satisfying the following conditions .
0.05 <fp / (− fn) <0.60
However,
fn: focal length of the front group,
fp: Focal length of the rear group. From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
The third lens group having a negative refractive power substantially consists of three lens groups ,
The first lens group includes a negative meniscus lens that is disposed closest to the object side and has a concave surface facing the image side, and a positive lens that has a negative refractive power in combination, and an image side of the front group And a rear group having a positive refractive power in combination , and
An aperture stop is provided between the first lens group and the second lens group;
The third lens group has a positive lens closest to the image side,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Fixed to the image plane,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
A photographic lens characterized by satisfying the following conditions .
0.04 <f / (− fn) <0.40
However,
fn: focal length of the front group,
f: Focal length of the entire system. The photographic lens according to claim 1, wherein the third lens group includes a positive lens closest to the image side. The first lens group includes, in order from the object side, a negative lens having a concave surface directed to the image side, a first positive lens, and a second positive lens.
Photographing lens according to any one of claims 2 to 5, characterized in that the following condition is satisfied.
0.10 <Da / Db <2.00
However,
Da: the distance on the optical axis between the most image side surface of the negative lens and the most object side surface of the first positive lens;
Db: Distance on the optical axis between the most image side surface of the first positive lens and the most object side surface of the second positive lens. Photographing lens according to any one of claims 1, 3 to 5, characterized in that the following condition is satisfied.
0.40 <X1 / f <0.90
However,
X1: absolute value of the amount of movement of the first lens unit on the optical axis when focusing from an infinite object point to the closest object point;
f: Focal length of the entire system. The photographic lens according to claim 1 , wherein the following condition is satisfied.
0.35 <f / TL <1.20
However,
TL: Total length when focusing on infinity,
f: Focal length of the entire system. The first lens group includes, in order from the object side, a front lens group including a negative lens having a concave surface directed toward the image side and a positive lens, and a combined negative refractive power, and an image side of the front lens group. And a rear group having a positive refractive power in combination,
Photographing lens according to claim 1 or 5, characterized in that the following condition is satisfied.
0.05 <fp / (− fn) <0.60
However,
fn: focal length of the front group,
fp: Focal length of the rear group. The first lens group includes, in order from the object side, a front lens group including a negative lens having a concave surface directed toward the image side and a positive lens, and a combined negative refractive power, and an image side of the front lens group. And a rear group having a positive refractive power in combination,
The photographic lens according to claim 1, wherein the following condition is satisfied.
0.04 <f / (− fn) <0.40
However,
fn: focal length of the front group,
f: Focal length of the entire system. The antireflection film is a multilayer film,
The photographic lens according to any one of claims 1 to 11 , wherein the layer formed by the wet process is a layer on a most surface side among layers constituting the multilayer film. Wherein when the refractive index of the layer formed using a wet process was nd, imaging lens according to claim 1, any one of 12, characterized in that nd is 1.30 or less. The optical surface, the imaging lens according to any one of claims 1 to 13, characterized in that when viewed from the aperture stop is a concave surface. 15. The photographic lens according to claim 14 , wherein the concave surface when viewed from the aperture stop is a lens surface on the image plane side. The photographic lens according to claim 14 , wherein the concave surface when viewed from the aperture stop is a lens surface on the object side. The photographic lens according to claim 14 , wherein the concave surface when viewed from the aperture stop is a lens surface of a lens closest to the object side. 15. The photographic lens according to claim 14 , wherein the concave surface when viewed from the aperture stop is a lens surface of a second lens closest to the image plane side from the lens closest to the object side. Photographing lens according to any one of claims 1 to 18, characterized in that the following condition is satisfied.
(−β) ≧ 0.50
However,
β: Image magnification when focusing on the closest object point. The photographic lens according to any one of claims 1 to 19 , wherein the following condition is satisfied.
0.07 <f2 / f1 <0.35
However,
f1: the focal length of the first lens group,
f2: focal length of the second lens group. The first lens group includes, in order from the object side, a negative lens having a concave surface facing the image side, and a positive lens.
Photographing lens according to any one of claims 1 20, characterized in that the following condition is satisfied.
0.90 <(r2 + r1) / (r2-r1) <2.50
However,
r1: radius of curvature of the surface closest to the image side of the negative lens,
r2: radius of curvature of the surface closest to the object side of the positive lens. The photographic lens according to any one of claims 1 to 21 , wherein the following condition is satisfied.
0.30 <f × (−β) / f2 <1.50
However,
f: focal length of the entire system,
β: Image magnification when focusing on the closest object point,
f2: focal length of the second lens group. The first lens group includes, in order from the object side, a front lens group including a negative lens having a concave surface directed toward the image side and a positive lens, and a combined negative refractive power, and an image side of the front lens group. And a rear group having a positive refractive power in combination,
The photographing lens according to any one of claims 1 to 22 , wherein the following condition is satisfied.
0.07 <f / fp <0.80
However,
fp: focal length of the rear group,
f: Focal length of the entire system. The photographic lens according to any one of claims 1 to 23 , wherein the third lens group includes at least one negative lens and at least one positive lens. The photographic lens according to any one of claims 1 to 24 , wherein the third lens group includes three lenses. An optical apparatus comprising the photographing lens according to any one of claims 1 to 25 . In order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power are substantially three lens groups. A method for producing a photographic lens comprising :
The first lens group includes, in order from the object side, a negative meniscus lens that is disposed closest to the object side with a concave surface facing the image side, a first positive lens, and a second positive lens .
An aperture stop is disposed between the first lens group and the second lens group,
When focusing from an infinite object point to a short-distance object point, the first lens group and the second lens group move to the object side while changing the distance between the lens groups, and the third lens group Placed so that it is fixed to the image plane ,
An antireflection film is provided on at least one of the optical surfaces in the first lens group,
The antireflection film viewed at least So含a layer formed using a wet process,
A method for producing a photographic lens, characterized by satisfying the following conditions:
0.10 <Da / Db <1.25
However,
Da: a distance on the optical axis between the most image side surface of the negative meniscus lens and the most object side surface of the first positive lens;
Db: Distance on the optical axis between the most image side surface of the first positive lens and the most object side surface of the second positive lens.

Images