JP2012027451A - Photographic lens, optical equipment having the photographic lens and photographic lens manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photographic lens which is a large diameter single focus wide angle lens of high ability having an aspheric surface which has adequate brightness and good optical performance.SOLUTION: A photographic lens SL mounted on a digital single lens reflex camera or the like has, seen from the object side, a first lens group G1, and a second lens group G2 with a positive refractive force. The first lens group G1 has, seen from the object side, a first lens component L11 of a negative meniscus shape with its convex side to the object side, a second lens component L12 of a negative meniscus shape with its convex side to the object side, and a third lens component L13. The third lens component L13 has a biconcave lens at the side closest to the object side and at least six lens components over the entire system.

Description

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

  Conventionally, a so-called retrofocus type lens preceded by a negative lens group is known as a single-focus wide-angle lens, but there are few proposals having an aspheric surface (for example, see Patent Documents 1 and 2). .

JP 2008-170720 A JP 2002-303790 A

  However, the prior arts shown in Patent Documents 1 and 2 have not yet proposed a large-aperture wide-angle lens with an open F value of 2.8 or higher and a brighter F value.

  The present invention has been made in view of such problems, and is a high-performance large-aperture single-focus wide-angle lens having an aspherical surface, which has sufficient brightness and excellent optical performance, and this photographic lens. It is an object of the present invention to provide an optical apparatus having the above and a method for manufacturing a photographic lens.

In order to solve the above-described problem, a photographic lens according to the present invention includes, in order from the object side, a first lens group and a second lens group having a positive refractive power. A negative meniscus first lens component having a convex surface facing the object side, a negative meniscus second lens component having a convex surface facing the object side, and a third lens component in order from the side; The lens component has a biconcave lens closest to the object side, and has at least six or more lens components in the entire system, where f is the focal length of the entire system, and the combined focal length of the first lens component and the second lens component Is represented by the following formula: 0.65 <f / (− fa) <1.15
Satisfy the conditions.

  In this photographing lens, it is preferable that at least one of the first lens component and the second lens component has an aspherical surface.

  In this photographing lens, it is preferable that at least one of the first lens component and the second lens component has an aspheric surface on the image plane side.

  In addition, this photographing lens preferably has an aperture stop between the first lens group and the second lens group.

  Further, in this photographing lens, the air space between the first lens group and the second lens group is fixed at the time of focusing on infinity, and between each lens in the first lens group and the second lens group. It is preferable that the air interval is fixed.

  In this photographing lens, it is preferable that at least a part of the first lens group is a focusing lens group.

  In this photographing lens, it is preferable that at least a part of the second lens group is a focusing lens group.

Further, in this photographic lens, when the focal length of the whole system is f and the focal length of the first lens component is f1, the following formula 0.40 <f / (− f1) <0.75
It is preferable to satisfy the following conditions.

In this photographic lens, when the radius of curvature of the object side surface of the first lens component is r1 and the radius of curvature of the image side surface is r2, the following equation −4.0 <(r2 + r1) / (r2− r1) <-1.1
It is preferable to satisfy the following conditions.

Further, in this photographing lens, when the focal length of the first lens component is f1 and the focal length of the second lens component is f2, the following expression 0.10 <f1 / f2 <1.00
It is preferable to satisfy the following conditions.

  An optical apparatus according to the present invention includes any one of the above-described photographing lenses.

The method for manufacturing a photographic lens according to the present invention is a method for manufacturing a photographic lens having a first lens group and a second lens group having a positive refractive power in order from the object side. Includes, in order from the object side, a negative meniscus first lens component having a convex surface facing the object side, a negative meniscus second lens component having a convex surface facing the object side, and a third lens component. The third lens component has a biconcave lens closest to the object side, is arranged so as to have at least six or more lens components in the entire system, the focal length of the entire system is f, and the first lens component and the second lens When the combined focal length of the components is fa, the following formula 0.65 <f / (− fa) <1.15
Arrange to satisfy the conditions.

  When the photographic lens, the optical apparatus having the photographic lens, and the manufacturing method of the photographic lens according to the present invention are configured as described above, a high-performance large-aperture single-focus wide-angle lens having an aspheric surface, which has sufficient brightness. Can be provided with excellent optical performance.

It is sectional drawing which shows the structure of the imaging lens by 1st Example. It is an aberration diagram in the infinity in-focus state of 1st Example. It is sectional drawing which shows the structure of the imaging lens by 2nd Example. FIG. 12 is a diagram illustrating various aberrations in the infinitely focused state according to the second example. It is sectional drawing which shows the structure of the photographic lens by 3rd Example. It is various aberrational figures in the infinite point focusing state of 3rd Example. It is sectional drawing which shows the structure of the photographic lens by 4th Example. It is an aberration diagram in the infinity in-focus state of 4th Example. It is sectional drawing which shows the structure of the imaging lens by 5th Example. It is an aberration diagram in the infinity in-focus state of 5th Example. 1 is a cross-sectional view of a digital single-lens reflex camera equipped with a photographing lens according to the present embodiment. It is a flowchart for demonstrating the manufacturing method of the imaging lens which concerns on this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In designing an objective optical system including a photographic lens, it is difficult to increase the aperture while simultaneously increasing the angle of view. In this embodiment, it has a large angle of view and a large aperture, but it is small enough to be used regularly, secures sufficient peripheral light quantity, has high optical performance, and can be used for mass production that can sufficiently produce aspheric lenses to be used. A technology developed.

  First, the basic structure of this embodiment will be described. As shown in FIG. 1, the photographing lens SL according to the present embodiment is a retrofocus type photographing composed of a first lens group G1 and a second lens group G2 having a positive refractive power in order from the object side. This is the lens SL. The first lens group G1 includes, in order from the object side, a negative meniscus first lens component L11 having a convex surface facing the object side, a negative meniscus second lens component L12 having a convex surface facing the object side, The third lens component L13 has a biconcave lens closest to the object side, and further includes a plurality of negative lenses and positive lenses. With this configuration, good aberration correction centering on off-axis aberration is performed.

  In addition, since at least one of the first lens component L11 and the second lens component L12 has an aspheric surface, it is possible to perform further better aberration correction and to achieve a reduction in size. Further, by manufacturing this aspherical surface by the glass mold method, it is possible to provide an inexpensive and highly accurate product.

  In addition, the photographic lens SL of the present embodiment is configured to have at least six lens components in the entire system. Each lens component may be composed of a single lens or a cemented lens. Therefore, in addition to FIG. 1 used in the above description, in the photographing lens SL of FIGS. 3 and 5, the third lens component is composed of a single lens (biconcave lens L13). In the photographing lens SL shown, the third lens component is composed of a cemented lens CL1 of a biconcave lens L13 and a biconvex lens L14. Furthermore, the photographing lens SL of the present embodiment is configured so that the focal length does not change except during focusing. With this configuration, it is possible to provide a photographic lens SL with a single focal point and a large angle of view and a large aperture.

  In addition, the photographing lens SL according to the present embodiment desirably has an aperture stop S between the first lens group G1 and the second lens group G2, but the lens is not provided with a member as an aperture stop. The role may be substituted in the frame.

  In the photographic lens SL according to the present embodiment, the air space between the first lens group G1 and the second lens group G2 is fixed when focusing on infinity, and the first lens group G1 and the first lens group G1 It is desirable that the air spacing between the lenses in the two-lens group G2 is also fixed. With this configuration, the mechanism can be simplified, the assembly is easy, the optical performance during assembly is small, and good optical performance can be obtained.

  The conditions for configuring such a photographing lens SL will be described. In the photographic lens SL of the present embodiment, when the focal length of the entire system is f and the combined focal length of the first lens component L11 and the second lens component L12 of the first lens group G1 is fa, the following conditional expression ( It is desirable to satisfy 1).

0.65 <f / (− fa) <1.15 (1)

  Conditional expression (1) is a relational expression between the focal length of the entire system and the combined focal length of the first lens component L11 and the second lens component L12, and is a conditional expression for obtaining an optimum power arrangement of the entire optical system. is there. If the upper limit value of the conditional expression (1) is exceeded, the combined power of the first lens component L11 and the second lens component L12 is relatively strong with respect to the focal length of the entire system. And the correction becomes excessive. In particular, the sagittal frame and field curvature are deteriorated, which is not preferable. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 1.09. In order to further secure the effect of the present embodiment, it is more preferable to set the upper limit of conditional expression (1) to 1.00. On the other hand, if the lower limit value of conditional expression (1) is not reached, the combined power of the first lens component L11 and the second lens component L12 is relatively weak with respect to the focal length of the entire system. Incorrect correction of coma. In particular, the sagittal piece deteriorates. Further, since the power shortage is forcibly corrected by the second lens group G2, spherical aberration is also deteriorated, which is not preferable. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.75. In order to further secure the effect of the present embodiment, it is more preferable to set the lower limit of conditional expression (1) to 0.85.

  In addition, it is desirable that the photographing lens SL of the present embodiment satisfies the following conditional expression (2), where f is the focal length of the entire system and f1 is the focal length of the first lens component L11.

0.40 <f / (− f1) <0.75 (2)

  Conditional expression (2) is a relational expression between the focal length of the entire system and the focal length of the first lens component L11, and is a conditional expression for obtaining an optimum power arrangement of the entire optical system. If the upper limit value of the conditional expression (2) is exceeded, the power of the first lens component L11 becomes relatively strong with respect to the focal length of the entire system, so that correction of field curvature and coma aberration becomes excessive. In particular, the sagittal frame and field curvature are deteriorated, which is not preferable. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.70. In order to further secure the effect of the present embodiment, it is more preferable to set the upper limit of conditional expression (2) to 0.65. On the other hand, if the lower limit value of conditional expression (2) is not reached, the power of the first lens component L11 becomes relatively weak with respect to the focal length of the entire system, so that correction of curvature of field and coma is insufficient. . In particular, the sagittal piece deteriorates. Further, since the power shortage is forcibly corrected by the second lens group G2, spherical aberration is also deteriorated, which is not preferable. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.45. In order to further secure the effect of this embodiment, it is more preferable to set the lower limit of conditional expression (2) to 0.50.

  In the imaging lens SL of the present embodiment, when the radius of curvature of the object side surface of the first lens component L11 is r1, and the radius of curvature of the image side surface is r2, the following conditional expression (3) is satisfied. It is desirable to do.

−4.0 <(r2 + r1) / (r2-r1) <− 1.1 (3)

  Conditional expression (3) is a conditional expression for determining the optimum shape of the first lens component L11. Exceeding the upper limit of conditional expression (3) is not preferable because the power of the first lens component L11 increases as a whole, and good aberration correction cannot be performed due to field curvature, coma aberration, and distortion aberration. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to −1.3. In order to further secure the effect of the present embodiment, it is more preferable to set the upper limit of conditional expression (3) to −1.5. On the other hand, if the lower limit of conditional expression (3) is not reached, the power of the first lens component L11 becomes too small, and it becomes difficult to realize a large angle of view, and the field curvature, coma aberration, and distortion aberration are good. This is not preferable because it cannot be corrected. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to −3.0. In order to further secure the effect of the present embodiment, it is more preferable to set the lower limit of conditional expression (3) to −2.5.

  In addition, it is desirable that the photographing lens SL of the present embodiment satisfies the following conditional expression (4) when the focal length of the first lens component L11 is f1 and the focal length of the second lens component L12 is f2. .

0.10 <f1 / f2 <1.00 (4)

  Conditional expression (4) is a relational expression between the focal length of the first lens component L11 and the focal length of the second lens component L12, and is a conditional expression for obtaining an optimum power arrangement. If the upper limit value of the conditional expression (4) is exceeded, the power of the second lens component L12 becomes larger than the power of the first lens component L11, and the field curvature, coma aberration, and distortion aberration can be corrected in a well-balanced manner. Since it becomes impossible, it is not preferable. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.85. In order to further secure the effect of the present embodiment, it is more preferable to set the upper limit of conditional expression (4) to 0.65. On the other hand, if the lower limit of conditional expression (4) is not reached, the power of the second lens component L12 is too small relative to the power of the first lens component L11, and the field curvature, coma aberration, and distortion are good. This is not preferable because correction cannot be performed. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.15. In order to further secure the effect of the present embodiment, it is more preferable to set the lower limit of conditional expression (4) to 0.20.

  FIG. 11 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 including the above-described photographing lens SL. 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 illustrated in FIG. 11 may be configured to hold the photographing lens SL in a detachable manner, or may be formed integrally with the photographing lens SL. The camera 1 may be a so-called single-lens reflex camera or a compact camera without a quick return mirror or the like.

  The contents described below can be appropriately adopted as long as the optical performance is not impaired.

  First, in the above description and the embodiments described below, the two-group configuration is shown. However, the above-described configuration conditions and the like can be applied to other group configurations such as the third group. Further, a configuration in which a lens or a lens group is added to the most object side, or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group indicates a portion having at least one lens separated by an air interval.

  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 at least a part of the first lens group G1 or the second lens group G2 is 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 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.

  Further, each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

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

  Hereinafter, an outline of a method for manufacturing the photographic lens SL 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 this embodiment, for example, in order from the object side, a negative meniscus lens L11 (first lens component) having a convex surface facing the object side, and a negative meniscus lens L12 (second lens component) having a convex surface facing the object side. ), A biconcave lens L13 (third lens component), a biconvex lens L14, a cemented lens CL1 of a negative meniscus lens L15 having a convex surface facing the object side and a biconvex lens L16, and a positive meniscus lens L17 having a convex surface facing the object side. The first lens group G1 is arranged, and in order from the object side, a biconcave lens L21, a positive meniscus lens L22 having a convex surface facing the object side, a negative meniscus lens L23 having a convex surface facing the object side, and a biconvex lens L24 are joined. A lens CL2, a biconvex lens L25, and a cemented lens CL of a negative meniscus lens L26 having a convex surface facing the object side and a biconvex lens L27 It was placed to the second lens group G2 with. The imaging lens SL is manufactured by arranging the lens groups thus prepared.

  Further, when the focal length of the entire system is f and the combined focal length of the first lens component L11 and the second lens component L12 is fa, each lens group is arranged so as to satisfy the above-described conditional expression (1) ( Step S200).

  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1, 3, 5, 7, and 9 show the configurations of the photographing lenses SL1 to SL5. As shown in these drawings, the photographing lenses SL1 to SL5 of each embodiment are configured in order from the object side, a first lens group G1 and a second lens group G2 having a positive refractive power. In each embodiment, the aperture stop S is located between the first lens group G1 and the second lens group G2.

Each embodiment has an aspheric lens. In this aspheric surface, the height in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangent plane of each vertex of the aspheric surface to each aspheric surface at the height y is S (y ), The radius of curvature of the reference sphere (paraxial radius of curvature) is r, the conic constant is κ, and the nth-order aspherical coefficient is An, and is expressed by the following equation (a). For example, “E−n” indicates “× 10 ⁻ⁿ ”. In each embodiment, the secondary aspheric coefficient A2 is zero. In the table of each example, an aspherical surface is marked with * on the left side of the surface number.

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 (a)

[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 includes, in order from the object side, a negative meniscus lens L11 (first lens component) having a convex surface facing the object side, and a negative meniscus lens L12 having a convex surface facing the object side. (Second lens component), biconcave lens L13 (third lens component), biconvex lens L14, cemented lens CL1 of negative meniscus lens L15 having a convex surface facing the object side and biconvex lens L16, and convex surface facing the object side The positive meniscus lens L17. Further, the negative meniscus lenses L11 and L12 having a convex surface facing the object side have a glass mold aspheric surface on the image surface side.

  The second lens group G2, in order from the object side, includes a biconcave lens L21, a positive meniscus lens L22 with a convex surface facing the object side, a cemented lens CL2 of a negative meniscus lens L23 with a convex surface facing the object side, and a biconvex lens L24, The lens includes a convex lens L25 and a cemented lens CL3 of a negative meniscus lens L26 having a convex surface facing the object side and a biconvex lens L27. Further, the negative meniscus lens L26 having a convex surface facing the object side has an aspheric surface on the object side.

  In the first example, focusing from infinity to a short-distance object point is performed by a cemented lens CL1 of a negative meniscus lens L15 having a convex surface facing the object side of the first lens group G1 and a biconvex lens L16, and on the object side. The positive meniscus lens L17 having a convex surface is moved in the image plane direction.

  Table 1 below lists values of specifications of the photographing lens SL1 according to the first example. In Table 1, f represents the focal length, 2ω represents the angle of view, FNO represents the F number, and Bf represents the back focus. Furthermore, the surface number is the order of the lens surfaces from the object side along the direction of travel of the light beam, the surface interval is the distance on the optical axis from each optical surface to the next optical surface, and the refractive index and Abbe number are each The value for the d-line (λ = 587.6 nm) is shown. Here, “mm” is generally used for the focal length, the radius of curvature, the surface interval, and other length units listed in all the following specifications, but the optical system is proportionally enlarged or reduced. However, the same optical performance can be obtained, and the present invention is not limited to this. The curvature radius 0.000 indicates a plane, and the curvature radius ∞ indicates an opening. The refractive index of air of 1.0000 is omitted. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 1)
f = 18.4
2ω = 100.3 °
F.NO = 1.84

Surface number Curvature radius Surface spacing Abbe number Refractive index
1 57.119 2.50 55.34 1.67790
* 2 15.500 12.56
3 55.930 2.00 52.64 1.74100
* 4 25.916 10.96
5 -41.336 2.00 82.52 1.49782
6 42.788 0.10
7 39.300 6.64 39.58 1.80440
8 -166.812 (d8)
9 42.931 2.00 42.71 1.83481
10 20.000 8.75 47.04 1.62374
11 -81.122 0.10
12 169.295 3.24 64.10 1.51680
13 314.929 (d13)
14 0.000 5.67 (Aperture stop S)
15 -43.335 1.00 42.72 1.83481
16 293.607 0.10
17 43.567 4.62 50.80 1.57099
18 118.468 0.10
19 33.408 1.00 49.45 1.77279
20 20.000 10.42 82.52 1.49782
21 -161.758 1.57
22 35.268 9.59 82.52 1.49782
23 -38.947 0.10
* 24 157.428 1.00 40.92 1.80610
25 20.000 8.77 61.13 1.58913
26 -520.433 (Bf)

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 -329.29
Second lens group 15 44.92

  In the first embodiment, the lens surfaces of the second surface, the fourth surface and the 24th surface are formed in an aspherical shape. Table 2 below shows aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 2)
κ A4 A6 A8 A10
Second side 0.1077 6.43851E-06 -1.03467E-08 7.31449E-11 -1.76329E-13
4th surface -0.5549 1.92571E-05 2.19908E-08 -5.95114E-11 5.24054E-13
24th surface -190.0565 -7.21005E-06 -2.58492E-08 3.51696E-11 0.00000E + 00

  In this first example, the axial air distance d0 between the object surface and the first lens group G1, and the axial air distance between the biconvex lens L14 of the first lens group G1 and the negative meniscus lens L15 having a convex surface facing the object side. d8 and the axial air distance d13 between the positive meniscus lens L17 having a convex surface facing the object side and the aperture stop S change during focusing. Table 3 below shows variable intervals in an infinitely focused state and an imaging magnification of 1/30 times.

(Table 3)
β Infinity -1/30
d0 ∞ 521.48
d8 1.51 2.35
d13 4.14 3.30
Bf 40.00 40.00

  Table 4 below shows values corresponding to the conditional expressions of the photographic lens SL1 according to the first example. In addition, although description of the code | symbol in this Table 4 is shown below, this code | symbol description is the same also in a subsequent Example. In Table 4, f is the focal length of the entire system, fa is the combined focal length of the first lens component L11 and the second lens component L12 of the first lens group G1, and f1 is the focal length of the first lens component L11. R1 and r2 represent the radius of curvature of the object side surface and the radius of curvature of the image side surface of the first lens component L11, respectively.

(Table 4)
(1) f / (− fa) = 0.97
(2) f / (− f1) = 0.57
(3) (r2 + r1) / (r2-r1) = − 1.7
(4) f1 / f2 = 0.48

  FIG. 2 is a diagram showing various aberrations when focusing on infinity according to the first embodiment. In each aberration diagram, FNO is the F number, Y is the image height, A is the half field angle, d is the aberration curve for the d-line (λ = 587.6 nm), and g is the g-line (λ = 435.8 nm). Aberration curves for) are shown respectively. In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. As is apparent from each aberration diagram, it can be seen that the first embodiment is well corrected for aberrations.

[Second Embodiment]
FIG. 3 is a diagram illustrating a configuration of the photographic lens SL2 according to the second example. In the photographic lens SL2 of FIG. 3, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 (first lens component) having a convex surface facing the object side, and a negative meniscus lens L12 having a convex surface facing the object side. (Second lens component), biconcave lens L13 (third lens component), biconvex lens L14, and cemented lens of a negative meniscus lens L15 having a convex surface facing the object side and a positive meniscus lens L16 having a convex surface facing the object side It is composed of CL1. Further, the negative meniscus lenses L11 and L12 having a convex surface facing the object side have a glass mold aspheric surface on the image surface side.

  The second lens group G2, in order from the object side, is a cemented lens CL2 of a biconvex lens L21 and a negative meniscus lens L22 having a concave surface facing the object side, a biconvex lens L23, a biconvex lens L24, and a biconcave lens L25 and a biconvex lens L26. And a cemented lens CL3. The biconcave lens L25 has an aspheric surface on the object side.

  In the second embodiment, focusing from infinity to a short distance object point is performed by joining a negative meniscus lens L15 having a convex surface toward the object side of the first lens group G1 and a positive meniscus lens L16 having a convex surface toward the object side. This is done by moving the lens CL1 in the image plane direction.

  Table 5 below lists values of specifications of the second embodiment.

(Table 5)
f = 20.4
2ω = 94.7 °
F.NO = 1.84

Surface number Curvature radius Surface spacing Abbe number Refractive index
1 58.184 2.50 55.34 1.67790
* 2 15.500 7.92
3 36.850 2.00 52.64 1.74100
* 4 24.431 9.97
5 -45.723 2.00 82.52 1.49782
6 64.259 1.29
7 58.335 6.52 39.58 1.80440
8 -77.755 (d8)
9 44.405 1.00 42.71 1.83481
10 21.000 8.44 47.04 1.62374
11 112.446 (d11)
12 0.000 1.10 (Aperture stop S)
13 51.855 7.86 82.52 1.49782
14 -55.109 1.00 49.45 1.77279
15 337.630 0.10
16 40.646 9.15 82.52 1.49782
17 -50.439 4.10
18 125.172 5.52 82.52 1.49782
19 -52.959 0.10
* 20 -115.391 1.00 40.92 1.80610
21 21.015 9.19 61.13 1.58913
22 -72.261 (Bf)

[Lens focal length]
Lens group Start surface Focal length first lens group 1 -46.91
Second lens group 13 39,90

  In the second embodiment, the lens surfaces of the second surface, the fourth surface and the twentieth surface are formed in an aspherical shape. Table 6 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 6)
κ A4 A6 A8 A10
2nd surface 0.5010 -7.68272E-06 -1.86678E-08 -7.57497E-12 -1.46293E-13
4th surface -0.5449 2.20823E-05 1.24878E-08 1.05153E-10 -3.04569E-14
20th surface 0.0000 -1.10223E-05 -8.84178E-10 -7.31469E-12 0.00000E + 00

  In the second embodiment, the axial air distance d0 between the object surface and the first lens group G1, and the axial air distance between the biconvex lens L14 of the first lens group G1 and the negative meniscus lens L15 having a convex surface facing the object side. d8 and the axial air distance d11 between the positive meniscus lens L16 having a convex surface facing the object side and the aperture stop S change during focusing. Table 7 below shows variable intervals in an infinitely focused state and an imaging magnification of 1/30 times.

(Table 7)
β Infinity -1/30
d0 ∞ 583.06
d8 11.67 15.81
d11 7.01 2.87
Bf 39.00 39.00

  Table 8 below shows values corresponding to the conditional expressions in the second embodiment.

(Table 8)
(1) f / (− fa) = 0.90
(2) f / (− f1) = 0.64
(3) (r2 + r1) / (r2-r1) = − 1.7
(4) f1 / f2 = 0.30

  FIG. 4 shows various aberration diagrams when focusing on infinity according to the second embodiment. As is apparent from the respective aberration diagrams, it can be seen that the second embodiment is well corrected for aberrations.

[Third embodiment]
FIG. 5 is a diagram illustrating a configuration of the photographic lens SL3 according to the third example. In the photographic lens SL3 of FIG. 5, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 (first lens component) having a convex surface facing the object side, and a negative meniscus lens L12 having a convex surface facing the object side. (Second lens component), biconcave lens L13 (third lens component), biconvex lens L14, negative meniscus lens L15 having a convex surface facing the object side, negative meniscus lens L16 and biconvex lens L17 having a convex surface facing the object side And a cemented lens CL1. Further, the negative meniscus lenses L11 and L12 having a convex surface facing the object side have a glass mold aspheric surface on the image surface side.

  The second lens group G2, in order from the object side, is a biconcave lens L21, a biconvex lens L22, a cemented lens CL2 of a biconcave lens L23 and a biconvex lens L24, a biconvex lens L25, and a cemented lens of a biconcave lens L26 and a biconvex lens L27. It is composed of CL3. The biconcave lens L26 has an aspheric surface on the object side.

  In the third example, focusing from infinity to a short-distance object point is performed by moving the biconvex lens L25 of the second lens group G2 and the cemented lens CL3 of the biconcave lens L26 and the biconvex lens L27 in the object direction. .

  Table 9 below lists values of specifications of the third example.

(Table 9)
f = 18.4
2ω = 100.3 °
F.NO = 1.84

Surface number Curvature radius Surface spacing Abbe number Refractive index
1 46.689 2.50 55.34 1.67790
* 2 15.662 12.59
3 49.621 2.00 52.64 1.74100
* 4 24.385 10.01
5 -52.182 2.00 82.52 1.49782
6 48.151 3.96
7 42.796 7.47 39.58 1.80440
8 -70.815 0.80
9 29.872 3.00 42.71 1.83481
10 22.318 4.17
11 38.373 1.00 47.04 1.62374
12 18.570 10.45 64.10 1.51680
13 -44.148 0.10
14 0.000 5.00 (Aperture stop S)
15 -51.745 1.00 42.72 1.83481
16 81.989 0.10
17 38.285 4.90 50.80 1.57099
18 -193.104 0.11
19 -249.218 1.00 49.45 1.77279
20 41.277 8.31 82.52 1.49782
21 -37.820 (d21)
22 46.769 7.54 82.52 1.49782
23 -42.145 0.10
* 24 -602.680 1.00 40.92 1.80610
25 23.141 7.63 61.13 1.58913
26 -97.706 (Bf)

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 48.37
Second lens group 15 59.19

  In the third embodiment, the lens surfaces of the second surface, the fourth surface and the 24th surface are formed in an aspherical shape. Table 10 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 10)
κ A4 A6 A8 A10
2nd surface 0.0671 7.12460E-06 1.50230E-08 -5.73850E-11 0.00000E + 00
4th surface 2.0611 5.92490E-06 1.13480E-08 8.21020E-11 0.00000E + 00
24th surface 1.0000 -6.78210E-06 -7.69510E-09 3.12160E-11 -7.67700E-14

  In the third embodiment, the axial air distance d0 between the object plane and the first lens group G1, the axial air distance d21 between the biconvex lens L24 and the biconvex lens L25 of the second lens group G2, and the back focus Bf are as follows. , Changes in focus. Table 11 below shows variable intervals in an infinitely focused state and an imaging magnification of 1/30 times.

(Table 11)
β Infinity -1/30
d0 ∞ 532.34
d21 3.25 2.61
Bf 40.05 40.68

  Table 12 below shows values corresponding to the conditional expressions in the third embodiment.

(Table 12)
(1) f / (− fa) = 0.89
(2) f / (− f1) = 0.51
(3) (r2 + r1) / (r2-r1) = − 2.0
(4) f1 / f2 = 0.54

  FIG. 6 shows various aberration diagrams when focusing on infinity according to the third embodiment. As is apparent from the respective aberration diagrams, it can be seen that the third embodiment is well corrected for aberrations.

[Fourth embodiment]
FIG. 7 is a diagram illustrating a configuration of the photographic lens SL4 according to the fourth example. In the photographic lens SL4 of FIG. 7, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 (first lens component) having a convex surface facing the object side, and a negative meniscus lens L12 having a convex surface facing the object side. (Second lens component), a cemented lens CL1 (third lens component) of a biconcave lens L13 and a biconvex lens L14, a negative meniscus lens L15 having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side It consists of a cemented lens CL2 with L16. Further, the negative meniscus lenses L11 and L12 having a convex surface facing the object side have a glass mold aspheric surface on the image surface side.

  The second lens group G2, in order from the object side, is a cemented lens CL3 of a biconvex lens L21 and a negative meniscus lens L22 having a concave surface facing the object side, a biconvex lens L23, a biconvex lens L24, and a biconcave lens L25 and a biconvex lens L26. And a cemented lens CL4. The biconcave lens L25 has an aspheric surface on the object side.

  In the fourth example, focusing from infinity to a short-distance object point is performed by joining a negative meniscus lens L15 having a convex surface toward the object side of the first lens group G1 and a positive meniscus lens L16 having a convex surface toward the object side. This is done by moving the lens CL2 in the image plane direction.

  Table 13 below provides values of specifications of the fourth example.

(Table 13)
f = 20.5
2ω = 94.5 °
F.NO = 1.85

Surface number Curvature radius Surface spacing Abbe number Refractive index
1 63.744 2.50 55.34 1.67790
* 2 15.500 6.48
3 34.255 2.00 52.64 1.74100
* 4 25.218 10.88
5 -57.486 2.00 82.52 1.49782
6 38.579 8.73 39.58 1.80440
7 -1431.273 (d7)
8 53.305 1.00 42.71 1.83481
9 37.094 6.02 47.04 1.62374
10 507.844 (d10)
11 0.000 12.08 (Aperture stop S)
12 258.113 8.66 82.52 1.49782
13 -27.323 1.00 49.45 1.77279
14 -85.607 0.10
15 27.957 10.77 82.52 1.49782
16 -87.769 4.29
17 156.732 5.08 82.52 1.49782
18 -69.917 0.10
* 19 -272.320 1.00 40.92 1.80610
20 21.000 9.47 61.13 1.58913
21 -75.047 (Bf)

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 -42.24
Second lens group 12 38.36

  In the fourth embodiment, the second, fourth, and nineteenth lens surfaces are formed in an aspherical shape. Table 14 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 14)
κ A4 A6 A8 A10
2nd surface 0.4420 -1.36385E-05 -2.78020E-08 -6.54972E-11 5.23238E-14
4th surface -0.2325 2.45601E-05 3.40714E-08 1.25606E-10 -1.51997E-14
19th surface 0.0000 -1.35372E-05 -1.06042E-08 -1.45748E-11 0.00000E + 00

  In this fourth example, the axial air distance d0 between the object surface and the first lens group G1, and the axial air distance between the biconvex lens L14 of the first lens group G1 and the negative meniscus lens L15 having a convex surface facing the object side. d7 and the on-axis air distance d10 between the positive meniscus lens L16 having a convex surface facing the object side and the aperture stop S change during focusing. Table 15 below shows variable intervals in an infinitely focused state and an imaging magnification of −1/30 times.

(Table 15)
β Infinity -1/30
d0 ∞ 591.96
d7 1.05 2.48
d10 6.23 4.80
Bf 39.00 39.00

  Table 16 below shows values corresponding to the conditional expressions in the fourth embodiment.

(Table 16)
(1) f / (− fa) = 0.86
(2) f / (− f1) = 0.66
(3) (r2 + r1) / (r2-r1) = − 1.6
(4) f1 / f2 = 0.22

  FIG. 8 shows various aberrations during focusing on infinity according to the fourth example. As is apparent from the respective aberration diagrams, it can be seen that the fourth embodiment is well corrected for aberrations.

[Fifth embodiment]
FIG. 9 is a diagram illustrating a configuration of the photographic lens SL5 according to the fifth example. 9, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 (first lens component) having a convex surface facing the object side, and a negative meniscus lens L12 having a convex surface facing the object side. (Second lens component) and a cemented lens CL1 (third lens component) of a biconcave lens L13 and a biconvex lens L14. Further, the negative meniscus lenses L11 and L12 having a convex surface facing the object side have a glass mold aspheric surface on the image plane side. The biconvex lens L13 has an aspheric surface on the object side.

  The second lens group G2, in order from the object side, is a cemented lens CL2, a biconvex lens L23 of a biconvex lens L21 and a negative meniscus lens L22 having a concave surface facing the object side, a biconvex lens L24, a biconcave lens L25, and a biconvex lens L26. And a cemented lens CL3. The biconvex lens L26 has an aspheric surface on the image plane side.

  In the fifth embodiment, focusing from infinity to a short-distance object point is performed by moving the entire photographing lens SL in the object direction.

  Table 17 below provides values of specifications of the fifth example.

(Table 17)
f = 20.2
2ω = 97.4 °
F.NO = 1.85

Surface number Curvature radius Surface spacing Abbe number Refractive index
1 43.400 2.00 55.34 1.67790
* 2 14.700 8.80
3 40.930 1.50 52.64 1.74100
* 4 31.487 9.55
* 5 -44.271 2.00 82.52 1.49782
6 34.432 15.00 39.58 1.80440
7 -144.886 12.46
8 0.000 6.42 (Aperture stop S)
9 119.763 8.74 82.52 1.49782
10 -28.514 1.00 49.45 1.77280
11 -70.685 0.99
12 34.375 10.24 82.52 1.49782
13 -87.851 4.21
14 69.680 5.54 82.52 1.49782
15 -78.466 1.39 40.92 1.80610
16 23.736 9.60 61.13 1.58913
* 17 -52.519 (Bf)

[Lens focal length]
Lens group Start surface Focal length first lens group 1 -35.31
Second lens group 9 37.17

  In the fifth embodiment, the second, fourth, fifth and seventeenth lens surfaces are formed in an aspherical shape. Table 18 below shows aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 18)
κ A4 A6 A8 A10
2nd surface 0.4759 -1.10225E-05 -2.84986E-09 -8.83468E-11 -3.30023E-14
4th surface -0.2716 2.31803E-05 3.75925E-09 2.32637E-10 -3.37989E-13
5th surface -0.2538 3.04922E-07 3.27983E-09 -2.25260E-11 2.77982E-14
17th -9.7414 4.25887E-06 1.37568E-08 2.57088E-11 0.00000E + 00

  In the fifth embodiment, the axial air gap d0 between the object plane and the first lens group G1 and the back focus Bf change during focusing. Table 19 below shows variable intervals in an infinitely focused state and an imaging magnification of -1/100 times.

(Table 19)
β Infinity -1/100
d0 ∞ 2000.026
Bf 39.000 39.202

  Table 20 below shows values corresponding to the conditional expressions in the fifth embodiment.

(Table 20)
(1) f / (− fa) = 0.73
(2) f / (− f1) = 0.59
(3) (r2 + r1) / (r2-r1) = − 2.0
(4) f1 / f2 = 0.17

  FIG. 10 shows various aberration diagrams when focusing on infinity according to the fifth embodiment. As is apparent from the respective aberration diagrams, it can be seen that the fifth embodiment is well corrected for aberrations.

SL (SL1 to SL5) Shooting lens G1 First lens group G2 Second lens group L11 First lens component L12 Second lens component L13, CL1 Third lens component S Aperture stop 1 Digital single lens reflex camera (optical apparatus)

Claims (12)

From the object side,
A first lens group;
A second lens group having a positive refractive power,
The first lens group includes:
In order from the object side, a negative meniscus first lens component having a convex surface facing the object side, a negative meniscus second lens component having a convex surface facing the object side, and a third lens component,
The third lens component has a biconcave lens closest to the object side,
The entire system has at least six lens components,
When the focal length of the entire system is f and the combined focal length of the first lens component and the second lens component is fa, the following expression 0.65 <f / (− fa) <1.15
A photographic lens characterized by satisfying the above conditions.   The photographing lens according to claim 1, wherein at least one of the first lens component and the second lens component has an aspherical surface.   3. The photographing lens according to claim 1, wherein at least one of the first lens component and the second lens component has the aspheric surface on the image plane side.   The photographic lens according to claim 1, further comprising an aperture stop between the first lens group and the second lens group.   At the time of focusing on infinity, the air interval between the first lens unit and the second lens unit is fixed, and the air interval between the lenses in the first lens unit and the second lens unit is fixed. The photographic lens according to claim 1, wherein the photographic lens is also fixed.   The photographing lens according to claim 1, wherein at least a part of the first lens group is a focusing lens group.   The photographing lens according to claim 1, wherein at least a part of the second lens group is a focusing lens group. When the focal length of the entire system is f and the focal length of the first lens component is f1, the following formula 0.40 <f / (− f1) <0.75
The photographic lens according to claim 1, wherein the following condition is satisfied. When the radius of curvature of the object-side surface of the first lens component is r1, and the radius of curvature of the image-side surface is r2, the following equation −4.0 <(r2 + r1) / (r2−r1) <− 1. 1
The photographic lens according to claim 1, wherein the following condition is satisfied. When the focal length of the first lens component is f1, and the focal length of the second lens component is f2, the following expression 0.10 <f1 / f2 <1.00
The imaging lens according to claim 1, wherein the following condition is satisfied.   An optical apparatus comprising the photographing lens according to claim 1. In order from the object side, a manufacturing method of a photographing lens having a first lens group and a second lens group having a positive refractive power,
The first lens group includes:
In order from the object side, a negative meniscus first lens component having a convex surface facing the object side, a negative meniscus second lens component having a convex surface facing the object side, and a third lens component,
The third lens component has a biconcave lens closest to the object side,
The entire system is arranged to have at least six lens components,
When the focal length of the entire system is f and the combined focal length of the first lens component and the second lens component is fa, the following expression 0.65 <f / (− fa) <1.15
A method of manufacturing a photographic lens, characterized by being arranged so as to satisfy the above condition.

Images