JP3221765B2 - Lens that can shoot at close range - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens capable of photographing at a short distance, and more particularly to a large-diameter macro lens capable of photographing from infinity to near the same magnification and mainly used as a camera lens.

[0002]

2. Description of the Related Art Conventionally, many proposals have been made for a macro lens capable of photographing from infinity to about the same magnification. Particularly, as a method of improving the performance at the time of focusing with a three-group configuration of positive, positive, and negative, the following is proposed. Has been proposed.

First, as a focusing system in which the first and second positive lens units are integrally moved toward the object side with respect to the fixed negative third lens unit, Japanese Patent Application Laid-Open No. 3-141313 is known. In the case of this focusing method, there is an advantage that the focusing mechanism can be simplified, but it is difficult to ensure high performance in all states from infinity to short distance. In the case of the above-mentioned prior example, aberration correction at the same magnification is not sufficient, and particularly off-axis field curvature aberration is large.

Next, as a focusing method for moving the positive first lens unit and the second lens unit toward the object side with respect to the fixed negative third lens unit, see JP-A-56-107210 and JP-A-2-107. 198
No. 14 and the like are known. JP-A-56-10721
In the case of No. 0, when focusing to a close distance,
The spherical aberration that increases at the closest position is corrected by increasing the group interval of the second group. However, this floating method is effective for correcting spherical aberration,
There is a drawback that off-axis aberrations, particularly coma aberrations, are deteriorated and high performance cannot be ensured from the center to the periphery. In the case of Japanese Patent Application Laid-Open No. 2-19814, the distance between the first and second lens groups at the closest position is reduced by reducing the distance between the positive first lens unit and the second lens unit when focusing on a close distance. The composite focal length is reduced, and the amount of extension is reduced. However, in this floating method, the amount of spherical aberration generated in the extending group (the first and second positive groups) becomes extremely large during focusing at a close distance, and correction is difficult. In the latter prior example, the so-called orbicular spherical aberration, in which the curvature of spherical aberration is large at the same magnification and becomes overcorrected (plus) with a large-diameter luminous flux, is not completely corrected.

A focusing system in which the first positive lens unit, the second lens unit, and the third negative lens unit are respectively extended toward the object side is disclosed in
No. 228220 is known. Japanese Patent Application Laid-Open No. Sho 62-1775 discloses a focusing system in which the first, second, and third groups are moved toward the object side with respect to the fourth, negative group.
No. 09 is known. The above two prior examples have the disadvantage that the magnification of the negative lens group, which is the last lens group, is small, and the amount of extension of the positive lens group, particularly the first group, which is the front group, is large. This increase in the feeding amount places a burden on the feeding mechanism and leads to an increase in the size of the product. Further, since the refractive power of the final negative lens group is weak, it is difficult to correct Petzval sum, and correction of various off-axis aberrations is insufficient.

[0006]

As described above, many proposals have been made on a lens capable of photographing from infinity to near the same magnification, that is, a so-called macro lens. Positive, positive,
The type based on the negative lens group configuration can reduce the amount of extension when focusing from infinity to a close distance, and has many advantages in ensuring performance. Has been done. However, none of the prior arts is sufficiently corrected for aberrations at a close distance, and cannot be said to have high performance in all states from infinity to a close position near the same magnification.

When the photographing distance changes from infinity to a close distance near the same magnification, the first problem is that the amount of change in spherical aberration is large. This is because the light beam incident on the first positive lens group located closest to the object side greatly changes. Next, there is a problem that the off-axis aberration becomes larger negatively as the field curvature aberration becomes closer. As a result, especially near the same magnification, the peripheral best image plane falls to the object side, and the peripheral best image plane and the central best image plane do not match. Although many prior examples include correction of off-axis aberrations, they have been proposed with the main aim of correcting spherical aberration that increases when focusing on a close distance. Therefore, any correction of off-axis aberrations is not sufficient, and especially near the same magnification, curvature of field of off-axis aberrations,
The coma aberration is remarkably deteriorated.

The present invention has been made in view of such a problem of the prior art, and an object of the present invention is to change the photographing distance from infinity to a close distance of about 1 × in a macro lens capable of photographing at a short distance. An object of the present invention is to satisfactorily correct the above-described fluctuations in spherical aberration and various off-axis aberrations that sometimes cause performance degradation.

[0009]

In order to achieve the above object, the present invention provides a short-distance photographable lens comprising a first lens unit (G1) having a positive refractive power and a second lens unit having a positive refractive power in order from the object side. (G2), a third lens group (G3) having a negative refractive power, the first lens group (G1) has at least one negative lens, and the second lens group (G2) has at least one lens. Group (G _2a ) having a negative lens and a rear group (G _2b ) having a positive refractive power
When focusing from infinity to a close distance, the first
Lens group (G1), and moves relatively in the object side with respect to the second lens group (G2) is the third lens group (G3), and said second lens group (G2) of the front group (G _2a ) And the rear group (G _2b ) move toward the object side such that the distance between them becomes wider when focusing on a short distance than when focusing on infinity, and further satisfies the following conditions. is there. −3.3 <f ₃ /f<−1.5 (1) 0.01 <Δd _ab / m ₁ <0.20 (2) where f is the total in the infinity in-focus state. The focal length of the system,
f ₃ is the focal length of the third lens group (G3), Δd _ab is infinity close distance the second lens group upon focusing on (G2) in the front group (G _2a) and the rear group (G _2b ) Is the maximum distance change amount, and m ₁ is the movement amount of the first lens group (G1) when focusing from infinity to a close distance.

In this case, when focusing from infinity to a short distance, the second lens group (G
In the case where the distance between the front group (G _2a ) and the rear group (G _2b ) in ₂ ) does not change, and when focusing is performed at a close distance beyond the intermediate magnification, the front group (G) in the second lens group (G2) is focused. _2a ) and the rear group (G _2b ) are desirably moved to the object side so as to widen the distance therebetween near a short distance.

[0011]

The reason and operation of the above configuration will be described below. The macro lens having three groups of positive, positive and negative according to the present invention basically has a positive and negative configuration, a positive lens group having a short focal length is arranged in the front group, and a negative lens group in the rear group. Has an enlargement magnification, and focuses on a short distance by extending a front lens group which is a positive lens group having a short focal length. In the case of this focusing method, there is an advantage that the amount of extension at the time of focusing on a short distance can be reduced as compared with the focusing method based on the whole extension. However, since the rear lens group has an enlargement magnification, there is a disadvantage that the aberration of the front group is enlarged, and it is necessary to sufficiently correct each aberration in the front group.

The lens arrangement according to the present invention has at least one lens in each of the first group (G1) and the second group (G2) having a positive refractive power in order to suppress the above-mentioned various aberrations in the front group. Has a negative lens. This is a condition necessary to set the aberration in each lens group small, and a condition necessary to suppress various aberrations in the front group (G1 to G2). It effectively works to correct spherical aberration and off-axis coma in the state.

When the photographing distance changes from infinity to a close distance near the same magnification with a macro lens having a positive / positive / negative configuration, a particular problem is that the amount of change in spherical aberration is large. This is because the light beam incident on the first positive lens group located closest to the object side changes greatly. By sufficiently correcting the spherical aberration generation amount in the front group (G1 to G2), the change amount can be reduced. However, if the amount of spherical aberration generated in the front group is reduced as much as possible, the spherical aberration is corrected favorably at infinity, and the amount of change in spherical aberration with respect to a short-distance object point is reduced as much as possible, near the same magnification. In other words, spherical aberration tends to be overcorrected (plus) at large diameters, so-called annular spherical aberration increases.

The next problem is the curvature of field and the coma which are greatly deteriorated near the same magnification. The lens configuration of the present invention is an advantageous configuration for keeping the Petzval sum good by the combination of the negative power and the positive power in the final lens group, and the field curvature at infinity focusing. It is relatively easy to satisfactorily correct astigmatism. However, it is difficult to ensure good image quality in the close-distance focusing state unless the amount of aberration generation is sufficiently suppressed in the front group (G1 to G2) and the rear group (G3).
In particular, near the same magnification, the amount of off-axis coma aberration and curvature of field aberration is large, and there is a problem that the best image surface in the peripheral portion falls to the object side.

A major feature of the present invention is that the second positive lens group (G2) in the front group includes a front group (G _2a ) having at least one negative lens and a rear group (G _2b ) having a positive refractive power. Composed of
When focusing from infinity to a close distance, the distance between the front group (G _2a ) of the second group and the rear group (G _2b ) of the positive refracting power is shorter when focusing on a short distance is closer to infinity. Moving to the object side to make it wider. By floating at this distance, it is possible to set a spherical aberration that is overcorrected (plus) with a large aperture in a close-up state near the same magnification, and at the same time, it is possible to raise an off-axis best image plane. Become.

The operation will be described in detail. At close distances near the same magnification, the spherical aberration of the large-diameter luminous flux becomes excessively corrected (plus), that is, the so-called orbicular spherical aberration increases. This is because high-order spherical aberration in the first positive lens unit (G1) is corrected. It is because it cannot be completed. In the present invention, the second
By floating the interval in the group (G2),
By changing the luminous flux incident on the rear group (G _2b ) having strong positive power in the second group (G2), high-order aberrations generated in the first group (G1) in the second group (G2) are reduced. Higher order aberrations are compensated for, and the amount of aberrations generated in the front group (G1 to G2) is reduced. This makes it possible to satisfactorily correct spherical aberration that is overcorrected (plus) by a large-diameter luminous flux at a close distance near the same magnification, so-called annular spherical aberration.

At the same time, the amount of curvature of field generated in the second lens unit (G2) at a close distance near the same magnification is reduced, and off-axis coma can be corrected with the change of the principal ray. Change in direction. As a result, the inclination of the curvature of field is corrected at a close distance near the same magnification, the center best image plane and the peripheral best image plane coincide, and it is possible to secure good image quality from the center to the periphery.

Next, specific conditions will be described. The condition (1) is a condition relating to the refractive power of the third group (G3), which is a negative lens group, and is a condition that defines a refractive power arrangement where the lens of the present invention can exert its effect, and exceeds the upper limit. Then, the amount of aberration generated in the third lens unit (G3) increases, and it becomes impossible to satisfactorily correct the aberration as a whole. In particular, the inclination of the curvature of field becomes extremely large at a close distance near the same magnification, and the distortion is increased to a large extent. When the lower limit of the condition (1) is exceeded, the third lens group (G
3) The amount of aberrations generated in (3) is reduced, which is advantageous for aberration correction. However, since the Petzval sum becomes large, the astigmatic difference of off-axis aberrations becomes extremely large at infinity, resulting in good image quality. Will be difficult to secure. Also, the second
The group interval between the group (G2) and the third group (G3) is reduced, and a problem of mechanical interference occurs.
-It is necessary to take measures such as weakening the power of the second unit, and eventually the overall length of the lens is increased.

The condition (2) is a condition for defining a floating amount in the second lens unit (G2) which is a feature of the present invention.
When the value exceeds the upper limit of the condition (2), the field curvature aberration of the off-axis aberration becomes excessively corrected in a close distance state near the same magnification, and
At the same time, the spherical aberration becomes negatively large, resulting in insufficient correction. In addition, with the deterioration of the spherical aberration, the off-axis coma becomes worse and cannot be corrected. If the lower limit of the condition (2) is exceeded, the aberration correction effect due to floating, which is the object of the present invention, will not be exhibited, and the spherical aberration of the annular zone will become extremely large at a close distance near the same magnification. Becomes large positively, and at the same time, the field curvature aberration largely falls to the object side, so that the central best image plane and the peripheral best image plane do not coincide with each other.

The combined focal length of the front group (G1 to G2) at infinity is f ₁₂ , and the first lens group (G
The refractive power of 1) is taken as f _1, by satisfying the following conditions, it is possible to further reduce the aberration generation amount upon focusing close range focus in front group (G1～G2) in .

1.5 <f ₁ / f ₁₂ <2.0 (3) Exceeding the upper limit of the above condition (3), the first positive lens group (G1)
When the refractive power of becomes weaker, the second
The positive refractive power of the lens group (G2) increases. In addition, since the ray convergence in the first group (G1) is weak, the second group (G1)
The light beam incident on 2) spreads. As a result, the amount of generation of various aberrations in the second positive lens unit (G2) increases, and spherical aberration increases particularly at a close distance, and correction cannot be completed. When the refractive power is increased beyond the lower limit of the condition (3), the refractive power of the rear group (G _2b ) having a particularly strong positive refractive power in the second group (G2) can be set weakly. This is advantageous for correcting spherical aberration when focusing at a close distance. However, the amount of aberrations generated in the first lens unit (G1) at the time of focusing on a close distance increases, and in particular, at the same time as the inclination of the image plane increases, the astigmatic difference increases and correction cannot be performed.

When the focal length of the entire system at infinity is f and the radius of curvature r _1R of the lens surface closest to the image side in the first lens unit (G1), the following condition is satisfied. It is easy to maintain good aberrations at infinity with a large aperture lens.

0.25 <r _1R /f<0.35 (4) When the value goes below the lower limit of the condition (4), the aberration in the sagittal direction is particularly deteriorated, and the curvature of the image plane is increased. External coma aberration worsens, so-called sagittal coma flare increases, and it becomes impossible to correct aberrations at infinity. When the value exceeds the upper limit of the condition (4), the refractive power due to the surface tends to be weaker, which is advantageous for aberration correction. However, the Petzval sum becomes large, and the astigmatic difference at infinity is corrected. It will not cut. If the upper limit is exceeded, the position of the rear principal point of the front group (G1 to G2) shifts to the image plane side, which causes an increase in group spacing and an increase in back focus, resulting in an increase in the overall lens length.

The feature of the present invention is that the second group (G
The floating of the lens interval in 2) compensates the aberration in the first group (G1) generated in the close range state, and reduces the amount of aberration generated in the front group (G1 to G2). The first group (G
In the case where the amount of aberration generation in 1) is suppressed as much as possible, when focusing from infinity to a close distance, the correction by floating becomes excessive at the intermediate magnification on the long distance side, and especially the center best image plane and the peripheral best. The image planes may not match. In order to maintain high image quality in all states from infinity to a close distance near the same magnification, it is necessary to set the aberration generation amount in each group as small as possible, especially in each lens group in infinity state. Needs to be reduced. In such a case, the phenomenon of deterioration of aberration occurs only in a close distance state after the intermediate magnification. That is, in order to obtain the best image quality in all conditions from infinity to a close distance near the unity magnification, when the photographing state exceeds the intermediate magnification, the image quality in the second group (G2) of the present invention is reduced. It can be said that a method of performing aberration correction by performing floating is more effective.

In the present invention, when focusing is performed from infinity to a close distance state near the same magnification, the first positive lens group (G1) and the second positive lens group (G2) change the distance between the groups. Even when the lens moves relatively to the object side with respect to the third lens group (G3), aberration can be corrected well by using the above-mentioned floating in the second group (G2). In addition to the floating in the second group (G2) of the present invention, the first positive lens group (G1) and the second positive lens group (G2) move to the object side so as to widen the group interval near a short distance. In this case, it is possible to set a smaller spherical aberration amount near the same magnification, and the first positive lens group (G1)
When the lens and the second positive lens group (G2) move toward the object side so as to reduce the distance between the groups in the vicinity of a short distance, the amount of extension of the lens when focusing from infinity to a close distance state near the same magnification is determined. It can be set smaller.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 8 of the macro lens of the present invention will be described below with reference to the drawings. The lens data will be described later. FIG. 1 is a lens cross-sectional view of Example 1 when focusing on infinity (a) and at the same magnification (b), and FIGS. 2, 3, and 4 show examples. FIGS. 2A and 2B are lens cross-sectional views of Examples 3, 3, and 4 when focused on infinity. Examples 5, 7, and 8 have substantially the same lens cross section as Example 1 and Example 6 as Example 2, so that illustration is omitted.

The first to eighth embodiments are macro lenses capable of photographing from infinity to the same magnification, and have a first lens unit G1 having a positive refractive power.
The second lens group G2 has a positive refracting power and the third lens group G3 has a negative refracting power.
Lens group G2, the second lens group G2 moves to the object side, and the front group G _2a and the rear group G _2b of the second lens group has a focusing moves to the object side while the interval .

Embodiments 1, 5, 7 to 8 show a biconvex lens from the object side, a positive meniscus lens having a convex surface facing the object side,
A first group G1 of positive refractive power composed of a negative meniscus lens having a strong concave surface facing the image surface side, a cemented lens of a biconcave lens and a biconvex lens, a positive meniscus lens having a convex surface facing the image surface side, and a positive lens composed of a biconvex lens A second group G2 having a refractive power, a biconvex lens, a biconcave lens, and a third group G3 having a negative refractive power composed of a positive meniscus lens having a convex surface facing the object side. When focusing from infinity to a short distance, the first group G1, second lens group G2 moves to the object side, and a cemented lens of a biconcave lens and a biconvex lens that is a second group G2 of the front group G _2a, is the group G _2b after the second group G2 A positive meniscus lens having a convex surface facing the image surface side and a biconvex lens move toward the object side while widening the group interval to focus.

The second and sixth embodiments have a first group G1 having a positive refractive power composed of a biconvex lens, a positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a strong concave surface facing the image side. A second unit G2 having a positive refractive power including a cemented lens of a biconcave lens and a biconvex lens, a biconvex lens, and a third unit having a negative refractive power including a biconvex lens, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. G3, when focusing from infinity to a short distance, the first group G1 and the second group G
2 is moved to the object side, and a cemented lens of a biconcave lens and a biconvex lens that is a second group G2 of the front group G _2a, the second group G2
The biconvex lens, which is the rear group _G2b , moves to the object side while focusing to increase the distance between the groups, and focuses. Note that Example 2 is on the object-side surface of the biconvex lens of the first group G1, and Example 6 is on the second side.
Object-side surface of the biconvex lens group G _2b after the group G2, is used one aspherical surface, respectively.

In the third embodiment, the first group of positive refractive power includes a biconvex lens from the object side, two positive meniscus lenses having a convex surface facing the object side, and a negative meniscus lens having a strong concave surface facing the image side. G1, a cemented lens of a biconcave lens and a biconvex lens, a positive meniscus lens having a convex surface facing the image side, a second group G2 of positive refractive power composed of a biconvex lens, a biconvex lens, a biconcave lens, and a convex surface facing the object side A third lens unit G3 composed of a positive meniscus lens and having a negative refractive power. When focusing from infinity to a short distance, the first lens unit G1 and the second lens unit G2 move to the object side, and the second lens unit G2. a biconcave lens and a cemented lens of a double convex lens which is G2 of the front group G _2a, the rear group of the second group G2 G _2b
The positive meniscus lens and the biconvex lens having the convex surface facing the image plane move toward the object side while widening the group interval to focus.

In the fourth embodiment, a first group G1 having a positive refractive power, comprising a biconvex lens, a positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a strong concave surface facing the image side, is used. A second group G2 having a positive refractive power including a cemented lens of a concave lens and a biconvex lens, a positive meniscus lens having a convex surface facing the image surface side, a positive meniscus lens having a convex surface facing the object side, and having a convex surface facing the image surface side. A third lens unit G3 having a negative refractive power, comprising a positive meniscus lens, a biconcave lens, and a biconvex lens. The first unit G3 is used when focusing from infinity to a short distance.
1, the second group G2 moves toward the object side, and a cemented lens of a biconcave lens and a biconvex lens that is a second group G2 of the front group G _2a, image plane side is a group G _2b after the second group G2 A positive meniscus lens having a convex surface directed toward the object and a positive meniscus having a convex surface directed toward the object side move toward the object side while widening the group interval to focus.

[0032] In Example 4-6, infinite to the photographing magnification 1/10 from far away, the distance between the front group G _2a and the rear group G _2b of the second group in G2 is by unchanged, the magnification of Even at relatively small shooting distances, better performance is maintained.

Similarly, in the seventh embodiment, the front group G _2a and the rear group G _2b in the second group G2 from infinity to a photographing magnification of 1/2.
Is invariable, and is moved so as to increase this distance when focusing from 撮 影 magnification to 1 × magnification.

In the eighth embodiment, the photographing magnification is 1/1 from infinity.
Up to 0 ×, the distance between the front group G _2a and the rear group G _2b in the second group G2 is unchanged, and this distance increases when focusing from 1/10 × to 1 ×. It moves and moves to the object side while the distance between the first group G1 and the second group G2 decreases.

In each embodiment, the aperture stop is the first stop.
It is arranged in the space between the group G1 and the second group G2. FIG.
32 to 32 are aberration diagrams of the respective examples. 5 to 7 are aberration diagrams of the first embodiment at infinity, 1/2 times, and 1: 1. In each state, spherical aberration, astigmatism, and distortion are shown. 8 to 10 are similar aberration diagrams according to the second embodiment, and FIGS. 11 to 13 are similar aberration diagrams according to the second embodiment. FIG. 14 to FIG. 17 show infinity, 1 /
FIG. 4 is an aberration diagram in a 10 ×, 1/2 ×, and 1 × state, and similarly shows spherical aberration, astigmatism, and distortion in each state. 18 to 21 are similar aberration diagrams according to the fifth embodiment, and FIGS. 22 to 25 are similar aberration diagrams according to the sixth embodiment. 26 to 28 show infinity, 1/2 of the seventh embodiment.
FIG. 29 to FIG. 32 are aberration diagrams at infinity, 1/10 ×, 倍 ×, and 1 × of the eighth embodiment, respectively. In each aberration diagram, F represents an F number, and Y represents an image height.

The lens data of Examples 1 to 8 above are shown below, where the symbols are as above, f is the focal length at infinity focusing, F _NO is the F-number at infinity focusing, and M is M photographing magnification (∞ represents a far-focusing distance _{infinity.), r 1, r 2} ... curvature radius of each lens surface, d _1, d ₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... is D-line refractive index of each lens, ν _d1 , ν
_d2 ... is the Abbe number of each lens. The aspherical shape is expressed by the following equation, where x is the optical axis direction and y is the distance from the optical axis. ^{x = y 2 / {r +} r [1-P (y / r) 2 ] ^1/2} + A ₄
y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ where r is the paraxial radius of curvature, P is the conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are aspherical coefficients.

[0037] Example _{1 f = 100 F NO = 2.86} r 1 = 100.2613 d 1 = 3.3528 n d1 = 1.77250 ν d1 = 49.66 r 2 = -634.7240 d 2 = 1.0596 r 3 = 38.7503 d 3 = 10.9255 n d2 = 1.80610 _{ν d2 = 40.95 r 4 = 113.1185} d 4 = 0.5525 r 5 = 257.1733 d 5 = 4.4162 n d3 = 1.78470 ν d3 = 26.22 r 6 = 30.5058 d 6 = 10.4828 r 7 = -37.1521 d 7 = 1.8404 n d4 = 1.67270 ν _d4 = 32.10 r ₈ = 377.5959 d ₈ = 5.5707 n _d5 = 1.78590 ν _d5 = 44.18 r ₉ = -53.1287 d ₉ = (variable) r ₁₀ = -193.5082 d ₁₀ = 2.1241 n _d6 = 1.78800 ν _d6 = 47.38 r ₁₁ = _{-69.1551 d 11 = 0.0064 r 12 =} 138.7597 d 12 = 2.1873 n d7 = 1.74100 ν d7 = 52.68 r 13 = -3490.9154 d 13 = ( _{variable) r 14 = 359.6462 d 14 =} 2.2057 n d8 = 1.80518 ν d8 = 25.43 r _{15 = -95.6058 d 15 = 0.9222 r} 16 = -114.1472 d 16 = 1.4612 n d9 = 1.79952 ν d9 = 42.24 r 17 = 35.9870 d 17 = 8.6702 r 18 = 44.5976 d 18 = 5.8308 n d10 = 1.61272 ν d10 = 58.75 r ₁₉ = 249.0311 (1) f ₃ /f=-1.89 (2) Δd _ab / m ₁ = 0.080 (3) f ₁ / f ₁₂ = 1.90 (4) r _1R /f=0.31
.

[0038] Example _{2 f = 100 F NO = 2.90} r 1 = 79.0842 ( _{aspherical) d 1 = 3.8192 n d1 =} 1.77250 ν d1 = 49.66 r 2 = -5032.4373 d 2 = 2.6325 r 3 = 38.4633 d 3 = 10.7188 _{n d2 = 1.78590 ν d2 = 44.18} r 4 = 91.2940 d 4 = 0.8209 r 5 = 156.2928 d 5 = 4.3738 n d3 = 1.78470 ν d3 = 26.22 r 6 = 28.3543 d 6 = 9.9477 r 7 = -35.6731 d 7 = 1.9909 n _{d4 = 1.67270 ν d4 = 32.10 r} 8 = 320.2481 d 8 = 4.2169 n d5 = 1.78590 ν d5 = 44.18 r 9 = -47.9688 d 9 = ( _{variable) r 10 = 196.9227 d 10 =} 2.4865 n d6 = 1.78590 ν d6 = 44.18 r ₁₁ = -93.3213 d ₁₁ = _{(variable) r 12 = 233.6723 d 12 =} 2.4656 n d7 = 1.80518 ν d7 = 25.43 r 13 = -100.9232 d 13 = 0.4833 r 14 = -120.3763 d 14 = 1.3581 n d8 = 1.80610 ν _{d8 = 40.95 r 15 = 36.5358 d} 15 = 10.4077 r 16 = 45.5721 d 16 = 4.3497 n d9 = 1.62280 ν d9 = 57.06 r 17 = 202.8410 Aspheric surface first surface P = 1.0000 A ₄ = -0.11520 × 10 ^-6 A ₆ = 0.10736 × 10 ^-9 A ₈ = -0.14745 × 10 ^-14 A ₁₀ = -0.45440 × 10 ^-15 (1) f ₃ / f = −2.13 (2) Δd _ab / m ₁ = 0.091 (3) f ₁ / f ₁₂ = 1.88 (4) r _1R /f=0.28
.

[0039] Example _{3 f = 100 F NO = 2.60} r 1 = 604.6515 d 1 = 7.7780 n d1 = 1.69680 ν d1 = 55.52 r 2 = -305.1304 d 2 = 0.1333 r 3 = 75.0446 d 3 = 3.2532 n d2 = 1.77250 _{ν d2 = 49.66 r 4 = 272.3840} d 4 = 0.1333 r 5 = 38.6022 d 5 = 10.5728 n d3 = 1.78590 ν d3 = 44.18 r 6 = 55.1875 d 6 = 0.9444 r 7 = 95.4099 d 7 = 3.1842 n d4 = 1.78470 ν d4 _{= 26.22 r 8 = 30.8285 d 8} = 12.2193 r 9 = -31.5379 d 9 = 1.2887 n d5 = 1.67270 ν d5 = 32.10 r 10 = 192.9620 d 10 = 5.5035 n d6 = 1.78590 ν d6 = 44.18 r 11 = -43.4020 d 11 = _{(variable) r 12 = -248.0289 d 12 =} 2.6111 n d7 = 1.78590 ν d7 = 44.18 r 13 = -74.3135 d 13 = 1.0561 r 14 = 208.2001 d 14 = 2.6563 n d8 = 1.72916 ν d8 = 54.68 r 15 = - 498.5283 d ₁₅ = _{(variable) r 16 = 565.4013 d 16 =} 3.0094 n d9 = 1.80518 ν d9 = 25.43 r 17 = -116.6258 d 17 = 0.9444 r 18 = -165.0658 d 18 = 1.5224 n d10 = 1.78590 ν d10 = 44.18 r ₁₉ = 37.2497 d ₁₉ = 11.0527 r ₂₀ = 46.5181 d _{2 0 = 4.7057 n d11 = 1.61272 ν} d11 = 58.75 r 21 = 248.3963 (1) f ₃ /f=−2.16 (2) Δd _ab / m ₁ = 0.078 (3) f ₁ / f ₁₂ = 1.89 (4) r _1R /f=0.31
.

[0040] Example _{4 f = 100 F NO = 2.86} r 1 = 77.7363 d 1 = 3.4700 n d1 = 1.77250 ν d1 = 49.66 r 2 = -643.6652 d 2 = 1.0973 r 3 = 42.2967 d 3 = 11.1569 n d2 = 1.80610 _{ν d2 = 40.95 r 4 = 83.9796} d 4 = 0.6273 r 5 = 187.4029 d 5 = 4.0256 n d3 = 1.78470 ν d3 = 26.22 r 6 = 31.4646 d 6 = 11.5310 r 7 = -30.8571 d 7 = 1.8444 n d4 = 1.67270 ν _{d4 = 32.10 r 8 = 641.8826 d} 8 = 5.5077 n d5 = 1.78590 ν d5 = 44.18 r 9 = -44.1170 d 9 = ( _{variable) r 10 = -258.6575 d 10 =} 2.1168 n d6 = 1.77250 ν d6 = 49.66 r 11 = _{-65.2111 d 11 = 0.1111 r 12 =} 152.2193 d 12 = 2.1464 n d7 = 1.74100 ν d7 = 52.68 r 13 = 897.5515 d 13 = ( _{variable) r 14 = -238.0454 d 14 =} 2.2223 n d8 = 1.80518 ν d8 = 25.43 r _{15 = -61.8452 d 15 = 0.9222 r} 16 = -68.8823 d 16 = 1.3334 n d9 = 1.78590 ν d9 = 44.18 r 17 = 41.9769 d 17 = 9.6628 r 18 = 56.2180 d 18 = 6.7262 n d10 = 1.61700 ν d10 = 62.79 r ₁₉ = -182.9115 (1) f ₃ /f=−3.22 (2) Δd _ab / m ₁ = 0.058 (3) f ₁ / f ₁₂ = 1.85 (4) r _1R /f=0.31
.

[0041] Example _{5 f = 100 F NO = 2.86} r 1 = 82.0072 d 1 = 3.3887 n d1 = 1.77250 ν d1 = 49.66 r 2 = -2285.5860 d 2 = 1.0973 r 3 = 41.3474 d 3 = 10.9704 n d2 = 1.80610 _{ν d2 = 40.95 r 4 = 102.8031} d 4 = 0.6710 r 5 = 202.5416 d 5 = 4.4065 n d3 = 1.78470 ν d3 = 26.22 r 6 = 31.2387 d 6 = 10.5551 r 7 = -34.4776 d 7 = 1.9409 n d4 = 1.67270 ν _{d4 = 32.10 r 8 = 345.8288 d} 8 = 5.8469 n d5 = 1.78590 ν d5 = 44.18 r 9 = -47.4529 d 9 = ( _{variable) r 10 = -227.5868 d 10 =} 2.1666 n d6 = 1.77250 ν d6 = 49.66 r 11 = _{-83.7747 d 11 = 0.2337 r 12 =} 172.1880 d 12 = 2.2682 n d7 = 1.74100 ν d7 = 52.68 r 13 = -395.4384 d 13 = ( _{variable) r 14 = 337.7301 d 14 =} 2.2221 n d8 = 1.80518 ν d8 = 25.43 r _{15 = -122.1248 d 15 = 0.9222 r} 16 = -171.1019 d 16 = 1.3265 n d9 = 1.78590 ν d9 = 44.18 r 17 = 36.1930 d 17 = 9.9621 r 18 = 44.8308 d 18 = 4.0554 n d10 = 1.62299 ν d10 = 58.14 r ₁₉ = 195.9432 (1) f ₃ /f=−2.17 (2) Δd _ab / m ₁ = 0.078 (3) f ₁ / f ₁₂ = 1.86 (4) r _1R /f=0.31
.

[0042] Example _{6 f = 100 F NO = 2.86} r 1 = 82.8340 d 1 = 3.5287 n d1 = 1.81600 ν d1 = 46.62 r 2 = -5378.8801 d 2 = 1.4629 r 3 = 37.9553 d 3 = 10.2883 n d2 = 1.78590 _{ν d2 = 44.18 r 4 = 89.4926} d 4 = 0.8110 r 5 = 167.0664 d 5 = 4.4569 n d3 = 1.80518 ν d3 = 25.43 r 6 = 29.3994 d 6 = 10.3880 r 7 = -35.8500 d 7 = 1.9626 n d4 = 1.67270 ν _d4 = 32.10 r ₈ = 349.9547 d ₈ = 4.0533 n _d5 = 1.79952 ν _d5 = 42.24 r ₉ = -48.9335 d ₉ = (variable) r ₁₀ = 192.8326 (aspherical surface) d ₁₀ = 3.3292 n _d6 = 1.78590 ν _d6 = 44.18 r ₁₁ = -93.8475 d ₁₁ = _{(variable) r 12 = 238.9547 d 12 =} 2.2220 n d7 = 1.80518 ν d7 = 25.43 r 13 = -99.4567 d 13 = 0.3333 r 14 = -123.2562 d 14 = 1.3415 n d8 = 1.80610 ν _d8 = 40.95 r ₁₅ = 36.0534 d ₁₅ = 11.3330 r ₁₆ = 44.8238 d ₁₆ = 3.9849 _{nd 9} = 1.61700 ν _d9 = 62.79 r ₁₇ = 194.8566 Aspheric surface 10th surface P = 1.0000 A ₄ = -0.23837 × 10 ^-6 A ₆ = 0.85244 × 10 ^-12 A ₈ = 0.49412 × 10 ^-12 A ₁₀ = -0.43293 × 10 ^-15 (1) f ₃ / f = -2.16 (2) Δd _ab / m ₁ = 0.08 (3) f ₁ / f ₁₂ = 1.90 (4) r _1R /f=0.29
.

[0043] Example _{7 f = 100 F NO = 2.86} r 1 = 97.8196 d 1 = 3.6808 n d1 = 1.77250 ν d1 = 49.66 r 2 = -348.4924 d 2 = 1.6239 r 3 = 42.8550 d 3 = 10.9278 n d2 = 1.80610 _{ν d2 = 40.95 r 4 = 111.8485} d 4 = 1.1396 r 5 = 400.7552 d 5 = 4.3314 n d3 = 1.78470 ν d3 = 26.22 r 6 = 33.4828 d 6 = 8.9511 r 7 = -34.8885 d 7 = 1.7222 n d4 = 1.67270 ν _{d4 = 32.10 r 8 = 874.4911 d} 8 = 5.1348 n d5 = 1.78590 ν d5 = 44.18 r 9 = -56.0857 d 9 = ( _{variable) r 10 = -168.7927 d 10 =} 2.0738 n d6 = 1.77250 ν d6 = 49.66 r 11 = _{-62.5854 d 11 = 0.0064 r 12 =} 267.6063 d 12 = 2.0912 n d7 = 1.74100 ν d7 = 52.68 r 13 = -159.6212 d 13 = ( _{variable) r 14 = 304.5439 d 14 =} 2.0544 n d8 = 1.80518 ν d8 = 25.43 r _{15 = -131.6794 d 15 = 0.9223 r} 16 = -199.6176 d 16 = 1.2130 n d9 = 1.78590 ν d9 = 44.18 r 17 = 36.1074 d 17 = 13.0359 r 18 = 45.7858 d 18 = 4.5506 n d10 = 1.61272 ν d10 = 58.75 r ₁₉ = 176.9179 (1) f ₃ /f=−2.13 (2) Δd _ab / m ₁ = 0.023 (3) f ₁ / f ₁₂ = 1.91 (4) r _1R /f=0.33
.

[0044] Example _{8 f = 100 F NO = 2.86} r 1 = 79.3589 d 1 = 7.5215 n d1 = 1.81600 ν d1 = 46.62 r 2 = -1549.3469 d 2 = 1.0381 r 3 = 39.9383 d 3 = 10.3508 n d2 = 1.80400 _{ν d2 = 46.57 r 4 = 77.3323} d 4 = 0.9829 r 5 = 160.9329 d 5 = 4.5910 n d3 = 1.80518 ν d3 = 25.43 r 6 = 30.8738 d 6 = ( _{variable) r 7 = -35.4277 d 7 =} 1.8629 n d4 = _{1.66680 ν d4 = 33.04 r 8 =} 384.3600 d 8 = 5.5057 n d5 = 1.78590 ν d5 = 44.18 r 9 = -48.9606 d 9 = ( _{variable) r 10 = -186.1971 d 10 =} 2.1907 n d6 = 1.78590 ν d6 = 44.18 r _{11 = -90.2600 d 11 = 1.0176 r} 12 = 144.5069 d 12 = 1.9405 n d7 = 1.72916 ν d7 = 54.68 r 13 = -262.3764 d 13 = ( _{variable) r 14 = 280.4038 d 14 =} 2.2223 n d8 = 1.80518 ν d8 = _{25.43 r 15 = -121.1287 d 15 =} 0.1185 r 16 = -180.7959 d 16 = 1.3334 n d9 = 1.79500 ν d9 = 45.29 r 17 = 36.0967 d 17 = 10.9422 r 18 = 45.0729 d 18 = 4.0972 n d10 = 1.60311 ν d10 = 60.70 r ₁₉ = 195.6851 (1) f ₃ /f=-2.16 (2) Δd _ab / m ₁ = 0.079 (3) f ₁ / f ₁₂ = 1.83 (4) r _1R /f=0.31
.

[0045]

As is clear from the above description, according to the present invention, in all the states from infinity to the close distance from infinity to near the same magnification, the lens is very well corrected for aberrations. This makes it possible to provide a lens that can perform short-distance shooting, in which various aberrations such as spherical aberration and curvature of field are corrected satisfactorily in the vicinity of the same magnification, in particular, near the same magnification.

[Brief description of the drawings]

FIG. 1 is a lens cross-sectional view of a macro lens according to a first embodiment of the present invention when focused on an object at infinity (a) and when photographing at the same magnification (b).

FIG. 2 is a lens cross-sectional view of Example 2 upon focusing on infinity.

FIG. 3 is a lens cross-sectional view of Example 3 upon focusing on infinity.

FIG. 4 is a lens cross-sectional view of Example 4 upon focusing on infinity.

FIG. 5 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion in Example 1 at an infinity state.

FIG. 6 is an aberration diagram similar to FIG. 5 in a 1 / 2-fold state of Example 1.

FIG. 7 is an aberration diagram similar to FIG. 5 in an equal magnification state of the first embodiment.

FIG. 8 is an aberration diagram similar to FIG. 5 in Example 2 at an infinite distance.

FIG. 9 is an aberration diagram similar to FIG. 5 in a 1 / 2-fold state of Example 2.

FIG. 10 is an aberration diagram similar to FIG. 5 in an equal magnification state of the second embodiment.

FIG. 11 is an aberration diagram similar to FIG. 5 in Example 3 at infinity.

FIG. 12 is an aberration diagram similar to FIG. 5 in a half-fold state of the third embodiment.

FIG. 13 is an aberration diagram similar to FIG. 5 in an equal magnification state of the third embodiment.

FIG. 14 is an aberration diagram similar to FIG. 5 in Example 4 at infinity.

15 is an aberration diagram similar to FIG. 5 in a 1 / 10-fold state of Example 4. FIG.

FIG. 16 is an aberration diagram similar to FIG. 5 in a 倍 magnification state of the fourth embodiment.

FIG. 17 is an aberration diagram similar to FIG. 5 in an equal magnification state of the fourth embodiment.

18 is an aberration diagram similar to FIG. 5 in Example 5 at infinity. FIG.

19 is an aberration diagram similar to FIG. 5 in a 1 / 10-fold state of Example 5. FIG.

FIG. 20 is an aberration diagram similar to that of FIG.

FIG. 21 is an aberration diagram similar to FIG. 5 in Example 1 in the same magnification state.

FIG. 22 is an aberration diagram similar to FIG. 5 in Example 6 at infinity.

FIG. 23 is an aberration diagram similar to FIG. 5 in a 1 / 10-fold state of Example 6.

FIG. 24 is an aberration diagram similar to that of FIG. 5 in a 1 / 2-fold state of Example 6.

FIG. 25 is an aberration diagram similar to FIG. 5 in a same-magnification state of the sixth embodiment.

26 is an aberration diagram similar to FIG. 5 in Example 7 at infinity. FIG.

FIG. 27 is an aberration diagram similar to FIG. 5 in a half-fold state of Example 7.

FIG. 28 is an aberration diagram similar to FIG. 5 in a same-magnification state of the seventh embodiment.

FIG. 29 is an aberration diagram similar to FIG. 5 in Example 8 at infinity.

30 is an aberration diagram similar to FIG. 5 in a 1 / 10-fold state of Example 8. FIG.

FIG. 31 is an aberration diagram similar to FIG. 5 in a １ ／ magnification state of the eighth embodiment.

FIG. 32 is an aberration diagram similar to FIG. 5 in Example 8 in the same magnification state.

[Explanation of symbols]

G1 first lens group G2 second lens group G3 third lens group _G2a front group of second lens group _G2b rear group of second lens group

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (5)

(57) [Claims] 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. The first lens group (G1) has at least one negative lens.
Lens group (G2) consists of the group (G _2b) a front group (G _2a) and positive refractive power having at least one negative lens, infinity upon focusing at a short distance, the first lens group (G
1) The second lens group (G2) is the third lens group (G
3) moving toward the object side relative to
The front group (G _2a ) and the rear group (G _2b ) of the lens group (G2) move toward the object side so that the distance between them becomes wider when focusing on a short distance than when focusing on infinity. A lens capable of short-distance photography characterized by satisfying the condition: −3.3 <f ₃ /f<−1.5 (1) 0.01 <Δd _ab / m ₁ <0.20 .. (2) where f is the focal length of the entire system in the infinity in-focus state,
f ₃ is the focal length of the third lens group (G3), Δd _ab is infinity close distance the second lens group upon focusing on (G2) in the front group (G _2a) and the rear group (G _2b ), The maximum distance change amount m ₁ is the movement amount of the first lens group (G1) when focusing from infinity to a close distance. 2. When focusing from infinity to a short distance, the distance between the front group (G _2a ) and the rear group (G _2b ) in the second lens group (G2) changes from infinity to intermediate magnification. Without focusing, the second lens group (G
2. The near-field photographing method according to claim 1, wherein the front group (G _2a ) and the rear group (G _2b ) in the second group move toward the object side so as to widen the distance between the front group and the rear group. lens. 3. The first lens group (G1) and the second lens group (G1).
Lens group the combined focal length at infinity state of (G2) f _12, the refractive power of the first lens group (G1) when the f _1, claim 1, characterized by satisfying the following conditions Or the lens capable of short-distance photography according to 2. 1.5 <f ₁ / f ₁₂ <2.0 (3) 4. The following condition is satisfied, where f is the focal length of the entire system at infinity, and r _1R is the radius of curvature of the lens surface closest to the image side in the first lens group (G1). 3. The lens according to claim 1, wherein the lens is capable of photographing at a short distance. 0.25 <r _1R /f<0.35 (4) 5. When focusing from infinity to a close distance state near the same magnification, the first positive lens group (G1) and the second positive lens group (G2) change the distance between the third lens group. 3. The lens according to claim 1, wherein the lens moves toward an object relative to (G3).