JP3231404B2 - Shooting lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera lens, and more particularly to a photographing lens suitable for a single-lens reflex camera.

[0002]

2. Description of the Related Art In recent years, a zoom lens has become popular as a lens for a single-lens reflex camera, and a zoom lens including a wide-angle lens to a telephoto lens has been widely used in place of a single focus lens having a focal length about the diagonal length of a film. It is supposed to be.

[0003] However, the zoom lens has been improved with respect to miniaturization and high zoom ratio, but its optical performance has been neglected.

[0004] Under such circumstances, a single focus lens is required to have good optical performance over the entire screen and to have little deterioration in performance even at a short distance.

As a standard lens having a focal length approximately equal to the diagonal length of a film, a Gauss type lens system such as a lens system described in JP-A-51-148421 is widely used. The Gauss type lens system is suitable for enlargement of the aperture, but it is difficult to correct sagittal coma flare, and extroverted coma is generated in short-distance shooting, resulting in deterioration of contrast.

Further, a lens system having good optical performance by correcting aberrations even at a short distance is disclosed in JP-A-59-15.
There are known macro lenses described in JP-A-2414, JP-A-2-285313 and JP-A-1-214812. These macro lenses have many Gauss type lens systems, and employ a floating system which includes a plurality of lens groups and independently moves each lens group during focusing. The performance is maintained within the range of the photographing magnification of about -1/2 to -1 by floating.

However, these macro lenses aim at improving the optical performance up to a very short distance,
The F number is about 2.8, and the half angle of view ω is slightly narrow, about 20 ° to 23 °.

Further, German Patent Application Publication No. 4005300A
The lens system shown in No. 1 has a wide half angle of view of 32 ° and a bright F number of 1.4, but has a short back focus and cannot be used for a single-lens reflex camera.
The lens system described in Japanese Patent Application Laid-Open No. 1-145617 is a copying lens system, which is limited to photographing at a finite distance, and has a dark F-number of 7 to 8.

A standard lens usually has a photographing magnification of 0 to −1/5.
Most of the lenses are used in a range of about 2.times., And a high-spec single focus lens having a good photographic magnification in this range is desired.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a standard lens for a single-lens reflex camera having a focal length close to the diagonal length of a film and an F-number of about 2.0, which is bright and has good performance over the entire screen. To provide.

Further, the present invention provides a standard lens for a single-lens reflex camera provided with a floating mechanism for maintaining good performance at a photographing magnification of about 0 to -1/5.

[0012]

According to the present invention, there is provided a photographing lens comprising:
In order from the object side, a first group having a positive refractive power, an aperture, and a second
And a third group having a positive refractive power. The first group has a negative lens disposed closest to the object side and a negative lens whose concave surface faces the image side disposed closest to the image side. The group includes a cemented lens component of two or three cemented lenses including a cemented lens in which a biconcave lens and a positive lens are cemented. The third lens group includes a negative lens having a concave surface facing the image side. A lens system in which a lens is arranged closest to the image side, and satisfies the following conditions (1) to (3). _{(1) -2 <(r b} + r a) / (r b -r a) <0 (2) -3 <(r d + r c) / (r d -r c) <0 (3) -1. _{6 <f 1 (1) /f<-0.6} f is the focal length of the entire _{system, f 1 (1)} is the focal length of the negative lens disposed on the most object side of the first _{group, r a,} r _b the object side of the negative lens curvature of the object side surface and image side surface of the negative lens disposed on the most object side of the first group radius, r _c, the r _d which is arranged on the most image side of the third group And the radius of curvature of the image side surface and the image side surface. The lens system of the present invention has a configuration in which a negative lens is arranged on the object side and the image side of a Gaussian type lens, and by setting the refractive power and the shape of the negative lens appropriately, good performance is achieved over the entire screen. Things.

That is, by arranging the negative lens before and after the Gaussian type lens system, the entrance pupil and the exit pupil can be made closer. As a result, the height of off-axis rays passing through the lens is reduced, and a wider angle and a sufficient amount of peripheral light can be secured.

Further, by adopting the above-described configuration, it is possible to correct spherical aberration, Petzval sum, and sagittal coma flare, and a good image can be obtained with a large aperture over the entire screen.

In the Gauss type lens system, spherical aberration and Petzval sum are corrected by negative lenses before and after the stop. For this purpose, it is necessary to increase the refractive power of the negative lenses before and after the stop. When the refractive power of the negative lens before and after the stop is increased in this way, the radius of curvature of the concave surface decreases,
Coma flare occurs in the sagittal direction.

In the lens system of the present invention, correction of spherical aberration and Petzval sum is shared by two newly added negative lenses. As a result, the radius of curvature of the concave surface of the negative lens before and after the stop can be increased, and thus sagittal coma flare can be corrected.

Further, according to the present invention, an almost symmetric lens arrangement is provided across the stop, which is advantageous for correction of coma, distortion, and chromatic aberration of magnification.

In order to correct longitudinal chromatic aberration and chromatic coma, a cemented lens in which a biconcave lens disposed immediately after the stop and a positive lens component are particularly effective is used. The cemented surface is convex toward the object side. Is preferable for correcting chromatic aberration. For this reason, the second lens group is moved immediately after the stop,
A component in which a biconcave lens and a positive lens are cemented is arranged closest to the object side in the group. This cemented lens component is based on the fact that a biconcave lens is arranged closest to the object side. Either a cemented lens or a cemented three lens in which one or two lenses are cemented on the image side thereof is used. Good.

For the reasons described above, the taking lens of the present invention has the above-described lens configuration.

Next, the meaning of each of the above conditions will be described. Of the conditions (1) to (3), the conditions (1),
(2) is provided to maintain a good balance of aberration correction before and after the stop, and is a negative lens disposed farthest from the stop, that is, a negative lens disposed closest to the object side in the first group. And the shape of the negative lens disposed closest to the image side of the third group.

The lens system of the present invention has a substantially symmetrical lens arrangement with a stop therebetween. However, in order to use it for photographing an object at infinity and an object at a short distance, it is not preferable to form a completely symmetric arrangement up to the lens shape.

In the present invention, the balance in aberration correction is improved by setting the shapes of the above both negative lenses in ranges satisfying the conditions (1) and (2), respectively.

If the upper limits of the conditions (1) and (2) are exceeded, coma and distortion will be insufficiently corrected.
If the lower limit of (2) is exceeded, the above aberrations will be overcorrected.

Condition (3) relates to the correction of Petzval's sum. By making the negative lens closest to the object side have sufficient refracting power, the axial ray height of the positive lens closer to the image side than the negative lens can be reduced. It is possible to make the sum higher and Petzval sum smaller. If the lower limit of the condition (3) is exceeded, the Petzval sum is insufficiently corrected. Conversely, if the upper limit is exceeded, the Petzval sum is advantageous for correction, but distortion is insufficiently corrected, which is not preferable.

Although the conditions (1) to (3) are collectively shown, as described above, the conditions (1) and (2) are for correcting coma aberration and distortion as a center, and 3) is for correcting mainly the Petzval sum. If the conditions (1) and (2) are satisfied, the above-described correction effect can be obtained regardless of whether the condition (3) is satisfied. Similarly, if the condition (3) is satisfied, a certain correction effect can be obtained irrespective of the conditions (1) and (2).

In the lens system having the above-described configuration, it is preferable to satisfy the following conditions (4), (5), and (6) from the viewpoint of aberration correction. (4) 0.3 <R _2C /f<1.2 (5) 8 <ν _2P −ν _2N <40 (6) 0.4 <(R _1R + | R _2F |) / 2f <2, R _2F <0 where R _1R is the radius of curvature of the image side surface of the negative lens closest to the image side of the first group, R _2F is the radius of curvature of the object side surface of the negative lens closest to the object side of the second group, and R _2C is The radii of curvature of the cemented surfaces convex to the object side of the cemented lens of the second group, ν _2N and ν _2P, are the Abbe numbers of the biconcave lens and the positive lens of the cemented lens of the second group, respectively.

Conditions (4) and (5) relate to the cemented lens of the second group and are preferable conditions for correcting chromatic aberration. Under these conditions, if the upper limit of the condition (4) or the lower limit of the condition (5) is exceeded, axial chromatic aberration and chromatic coma tend to be insufficiently corrected, and if the lower limit of the condition (4) or the upper limit of the condition (5) is exceeded. Both aberrations are likely to be overcorrected.

The condition (6) defines the radius of curvature of the concave surface facing the diaphragm, and if it is within this range, it is advantageous for correcting spherical aberration and sagittal coma flare. Exceeding the lower limit of the condition (6) is disadvantageous for correcting sagittal coma flare, while exceeding the upper limit is disadvantageous for correcting spherical aberration, and both are disadvantageous for increasing the aperture ratio of the lens system.

As described above, one object of the present invention is to provide a lens system provided with a floating mechanism capable of obtaining good optical performance in both shooting of an object at infinity and shooting of a short-distance object. It is in.

In order to achieve this object, the lens system of the present invention has the following configuration. That is, in order from the object side, a first unit having a positive refractive power, a stop, a second unit , and a third unit having a positive refractive power are provided. The third unit has a negative surface with a concave surface facing the image side.
A lens in which the first lens unit, the diaphragm, and the second lens unit are integrally extended to the object side, and the third lens unit is extended to the object side so as to increase the distance between the second lens unit and the second lens unit. This is a photographic lens that focuses on a distance object and satisfies the following conditions (7) and (8). _{(7) 1.2 <f 12 /} f <3 (8) 1.2 <f 3 / f <3 provided that f is the focal length of the entire _{system, f 12} is the composite focal length of the first group and the second group, f ₃ is the focal length of the third group.

The most problematic problem at the time of short-range photographing is that outward coma greatly occurs. In order to correct this aberration, floating in which the interval effective for the correction changes is performed. In this case, it is more advantageous to increase the change interval effective for the above correction, but the configuration of the lens frame becomes complicated, and up to a photographing magnification of about −1/5, the change interval due to floating is one place. Good.

In the present invention, as described above, the first group, the aperture, and the second group are formed as one movable group (referred to as a front group), and the third group is defined as another movable group (referred to as a rear group). By moving the lens unit toward the object side so as to increase the distance between the front group and the rear group, focusing on a short-distance object is performed.

Here, the power arrangement of the front group and the rear group is preferably such that both groups have a positive refractive power and share the refractive power of the entire system. If the positive refractive power is shared between the two groups, the refractive power of each group can be reduced, which is advantageous in correcting aberrations.

If the refractive power of the front group is positive and the refractive power of the rear group is negative, it is advantageous to reduce the feeding amount, so that close-up photographing at a photographing magnification of about -1 is performed. Although suitable for a macro lens, it is disadvantageous for securing the back focus, and it is difficult to reduce the focal length, that is, to increase the angle of view.

In addition, when photographing at a short distance, not only the outward coma but also the spherical aberration and the distortion are insufficiently corrected. In order to correct the spherical aberration and distortion, the third lens unit has a positive refractive power, and a negative lens having a concave surface closest to the image side is disposed.

Next, the meaning of the conditions (7) and (8) will be described. Conditions (7) and (8) define the refracting power of the front group and the rear group, respectively. If the upper limit of the condition (7) or the lower limit of the condition (8) is exceeded, spherical aberration and distortion will occur when focusing on a short distance. If aberration correction becomes difficult, and if the lower limit of the condition (7) or the upper limit of the condition (8) is exceeded, it becomes difficult to secure the back focus, and the floating interval at the time of short-distance focusing becomes large. The height of off-axis rays passing through the rear group becomes high, and it becomes difficult to secure the amount of peripheral light.

It is more preferable that the following condition (2) be satisfied in addition to the above conditions. _{(2) -3 <(r d} + r c) / (r d - r c) <0 However r _c, r _d is the object-side surface of the negative lens disposed respectively closest to the image side of the third group and This is the radius of curvature of the image-side surface.

This condition relates to the shape of the negative lens disposed closest to the image side of the third lens unit, and is for correcting distortion at the time of short-range photographing. If the upper limit or lower limit of the condition (2) is exceeded, the fluctuation of the distortion at the time of focusing becomes large, so that it is disadvantageous when the photographing magnification is increased.

[0039]

Next, embodiments of the taking lens according to the present invention will be described. Example 1 f = 1, F / 2.0, 2ω = 51.6 °, f _B = 0.835 r ₁ = −1.4363 d ₁ = 0.0330 n ₁ = 1.60342 ν ₁ = 38.01 r ₂ = 0.8052 d ₂ = 0.0858 r ₃ = 0.8978 d _{3 = 0.1081 n 2 = 1.83481 ν} 2 = 42.72 r 4 = -1.6004 d 4 = 0.0029 r 5 = 0.7367 d 5 = 0.1148 n 3 = 1.83400 ν 3 = 37.16 r 6 = 5.3117 d 6 = 0.0208 r 7 = -5.4856 d ₇ = 0.0311 n ₄ = 1.58144 ν ₄ = 40.75 r ₈ = 0.6330 d ₈ = 0.0744 r ₉ = ∞ (aperture) d ₉ = 0.1524 r ₁₀ = -0.5215 d ₁₀ = 0.0311 n ₅ = 1.75520 ν ₅ = 27.51 r ₁₁ = _{0.5894 d 11 = 0.1100 n 6 =} 1.66524 ν 6 = 55.12 r 12 = -2.6568 ( _{aspherical) d 12 = 0.0056 r 13 =} 3.0018 d 13 = 0.0796 n 7 = 1.83481 ν 7 = 42.72 r 14 = -0.9138 d 14 = 0.0097 r ₁₅ = -13.7003 d ₁₅ = 0.0760 n ₈ = 1.83400 v ₈ = 37.16 r ₁₆ = -0.8037 d ₁₆ = 0.0029 r ₁₇ = 3.3817 d ₁₇ = 0.0330 n ₉ = 1.56732 v ₉ = 42.83 r ₁₈ = 0.8881 P = 1.0000, E = 0.15037 10, F = -0.22036 × 10, G = 0.42687 × 10 2 H = -0.31076 × 10 3 D 23 = 0.031 (r b + r a) / (r b -r a) = (r 2 + r 1) / (r ₂ -r ₁ ) =-0.282, (r _b + r _a ) / (r _b -r _a ) = (r ₁₈ + r ₁₇ ) / (r ₁₈ -r ₁₇ ) =-1.71, f _{1 (1 ) / f = -0.850, R 2C} / f = r 11 / f = 0.589, ν 2P -ν 2N = ν 6 -ν 5 = 27.6, f 12 / f = 1.86, f 3 / f = 1.91, (R 1R _{+ | R 2F |) / 2f} = (r 8 + | r 10 |) / 2f = 0.577

Example 2 f = 1, F / 2.0, 2ω = 50.0 °, f _B = 0.836 r ₁ = -1.5245 d ₁ = 0.0330 n ₁ = 1.51454 ν ₁ = 54.69 r ₂ = 0.7207 d ₂ = 0.1214 r ₃ = 0.8777 d ₃ = 0.1081 n ₂ = 1.78590 v ₂ = 44.18 r ₄ = -1.5212 d ₄ = 0.0029 r ₅ = 0.6296 d ₅ = 0.1222 n ₃ = 1.77 250 v ₃ = 49.66 r ₆ = 4.1050 d ₆ = 0.0220 r ₇ = _{-4.5849 d 7 = 0.0311 n 4 =} 1.64769 ν 4 = 33.80 r 8 = 0.5544 d 8 = 0.0787 r 9 = ∞ ( _{stop) d 9 = 0.0958 r 10 =} -0.5759 d 10 = 0.0311 n 5 = 1.75520 ν 5 = 27.51 _{r 11 = 0.5396 d 11 = 0.1051} n 6 = 1.66524 ν 6 = 55.12 r 12 = -2.7571 ( _{aspherical) d 12 = 0.0056 r 13 =} 3.0687 d 13 = 0.0816 n 7 = 1.78472 ν 7 = 25.68 r 14 = -0.8368 _{d 14 = 0.0097 r 15 = 5.1735} d 15 = 0.0835 n 8 = 1.77250 ν 8 = 49.66 r 16 = -0.7844 d 16 = 0.0029 r 17 = 9.4695 d 17 = 0.0330 n 9 = 1.67270 ν 9 = 32.10 r 18 = 0.8782 non Spherical coefficient P = 1.0000 E = 0.16832 × 10, F = -0.14716 × 10, G = 0.30461 × 10 2 H = -0.25785 × 10 3 D 23 = 0.026 (r b + r a) / (r b -r a) = (r 2 + r ₁ ) / (r ₂ -r ₁ ) =-0.358, (r _d + r _c ) / (r _d -r _c ) = (r ₁₈ + r ₁₇ ) / (r ₁₈ -r ₁₇ ) =-1.20, _{f 1 (1) / f =} -0.946, R 2C / f = r 11 / f = 0.540, ν 2P -ν 2N = ν 6 -ν 5 = 27.6, f 12 / f = 1.71, f 3 / f = 2.19 , (R _1R + | R _2F |) / 2f = (r ₈ + | r ₁₀ |) /2f=0.565

Example 3 f = 1, F / 2.06, 2ω = 51.8 °, f _B = 0.83 r ₁ = -1.6622 d ₁ = 0.0330 n ₁ = 1.54072 ν ₁ = 47.20 r ₂ = 0.6503 d ₂ = 0.0858 r _{3 = 0.7019 d 3 = 0.1345 n 2} = 1.79952 ν 2 = 42.24 r 4 = -1.9054 d 4 = 0.0029 r 5 = 0.6818 d 5 = 0.0980 n 3 = 1.83400 ν 3 = 37.16 r 6 = 1.4453 d 6 = 0.0240 r 7 = 5.5065 d ₇ = 0.0311 n ₄ = 1.60342 v ₄ = 38.01 r ₈ = 0.6051 d ₈ = 0.0793 r ₉ = ∞ (aperture) d ₉ = 0.0724 r ₁₀ = -0.5510 d ₁₀ = 0.0301 n ₅ = 1.75520 v ₅ = 27.51 r ₁₁ = 0.4653 d ₁₁ = 0.0899 n ₆ = 1.66524 v ₆ = 55.12 r ₁₂ = -2.3890 (aspheric surface) d ₁₂ = 0.0056 r ₁₃ = 1.5790 d ₁₃ = 0.1098 n ₇ = 1.80400 v ₇ = 46.57 r ₁₄ =-1.2056 d _{14 = 0.0255 r 15 = -8.9143 d} 15 = 0.0651 n 8 = 1.83400 ν 8 = 37.16 r 16 = -0.7196 d 16 = 0.0029 r 17 = 2.4047 d 17 = 0.0621 n 9 = 1.49831 ν 9 = 65.03 r 18 = 0.6449 non Spherical coefficient P = 1.0000 E = 0.19658 × 10, F = 0.87501 × 10, G = -0.10099 × 10 3 H = 0.63155 × 10 3 D 23 = 0.028 (r b + r a) / (r b -r a) = (r 2 + r ₁ ) / (r ₂ -r ₁ ) =-0.438, (r _d + r _c ) / (r _d -r _c ) = (r ₁₈ + r ₁₇ ) / (r ₁₈ -r ₁₇ ) =-1.73, f _{1 (1) / f = -0.860} , R 2C / f = r 11 / f = 0.465, ν 2P -ν 2N = ν 6 -ν 5 = 27.6, f 12 / f = 2.02, f 3 / f = 1.84, (R _1R + | R _2F |) / 2f = (r ₈ + | r ₁₀ |) /2f=0.578

Example 4 f = 1, F / 2.05, 2ω = 51.8 °, f _B = 0.77 r ₁ = −1.5710 d ₁ = 0.0321 n ₁ = 1.54814 ν ₁ = 45.78 r ₂ = 0.5855 d ₂ = 0.0286 r _{3 = 0.6275 d 3 = 0.1246 n 2} = 1.78590 ν 2 = 44.18 r 4 = -1.7335 d 4 = 0.0049 r 5 = 0.5143 d 5 = 0.0833 n 3 = 1.78590 ν 3 = 44.18 r 6 = 0.7883 d 6 = 0.0283 r 7 = 2.1444 d ₇ = 0.0350 n ₄ = 1.66446 ν ₄ = 35.81 r ₈ = 0.4575 d ₈ = 0.0965 r ₉ = ∞ (aperture) d ₉ = 0.0469 r ₁₀ = -1.7938 (aspherical surface) d ₁₀ = 0.0301 n ₅ = 1.68893 ν _{5 = 31.08 r 11 = 0.4762 d} 11 = 0.0822 n 6 = 1.78590 ν 6 = 44.18 r 12 = 2.3183 d 12 = 0.0636 r 13 = -1.9971 ( _{aspherical) d 13 = 0.0787 n 7 =} 1.71300 ν 7 = 53.84 r 14 _{= -0.5697 d 14 = 0.0029 r 15} = 1.1813 d 15 = 0.1028 n 8 = 1.79952 ν 8 = 42.24 r 16 = -0.9785 d 16 = 0.0051 r 17 = 3.2217 d 17 = 0.0544 n 9 = 1.67270 ν 9 = 32.10 r 18 = 0.5174 Aspheric coefficient (Tenth surface) P = 1.0000, E = -0.56407 × 10, F = −0.23973 × 10 ² , G = 0.25284 × 10 ³ , H = −0.23013 × 10 ⁴ (Thirteenth surface) P = 1.0000, E = 0.84444 × 10, F = −0.27704 × 10, G = −0.37345 × 10 ² , H = −0.56361 × 10 ² D ₂₃ = 0.019 (r _b + r _a ) / (r _b -r _a ) = (r ₂ + r ₁ ) / (r ₂ -r ₁ ) =-0.457, (r _d + r _c ) / (r _d -r _c ) = (r ₁₈ + r ₁₇ ) / (r ₁₈ -r ₁₇ ) =-1.38, f _{1 (1) / f = -0.774} , R 2C / f = r 11 / f = 0.476, ν 2P -ν 2N = ν 6 -ν 5 = 13.1, f 12 / f = 1.92, f 3 / f = 2.03, _{(R 1R + | R 2F |} ) / 2f = (r 8 + | r 10 |) / 2f = 1.13

Example 5 f = 1, F / 2.05, 2ω = 51.8 °, f _B = 0.77 r ₁ -10.4298 d ₁ = 0.0359 n ₁ = 1.54072 ν ₁ = 47.20 r ₂ = 0.6912 d ₂ = 0.0322 r _{3 = 0.8351 d 3 = 0.1001 n 2} = 1.83481 ν 2 = 42.72 r 4 = -2.8965 d 4 = 0.0049 r 5 = 0.5054 d 5 = 0.0889 n 3 = 1.83481 ν 3 = 42.72 r 6 = 0.9600 d 6 = 0.0255 r 7 = 3.2381 d ₇ = 0.0350 n ₄ = 1.67270 v ₄ = 32.10 r ₈ = 0.4101 d ₈ = 0.0942 r ₉ = ∞ (aperture) d ₉ = 0.0734 r ₁₀ = -0.8578 (aspherical surface) d ₁₀ = 0.0310 n ₅ = 1.71736 v _{5 = 29.51 r 11 = 0.7969 d} 11 = 0.1237 n 6 = 1.83481 ν 6 = 42.72 r 12 = -0.7299 d 12 = 0.1197 n 7 = 1.51823 ν 7 = 58.96 r 13 = -0.8642 d 13 = 0.0243 r 14 = -10.9232 _{d 14 = 0.0668 n 8 = 1.80400} ν 8 = 46.57 r 15 = -0.6481 d 15 = 0.0027 r 16 = 4.7977 d 16 = 0.0544 n 9 = 1.69895 ν 9 = 30.12 r 17 = 0.9446 aspherical coefficient P = 1.0000, E = -0.19514 × 10, F = -0. 44053 × 10 ² , G = 0.10468 × 10 ⁴ , H = −0.11789 × 10 ⁵ D ₂₃ = 0.040 (r _b + r _a ) / (r _b -r _a ) = (r ₂ + r ₁ ) / (r ₂ -r ₁ ) =-0.876, (r _d + r _c ) / (r _d -r _c ) = (r ₁₇ + r ₁₆ ) / (r ₁₇ -r ₁₆ ) =-1.49, f _{1 (1)} / f _{= -1.120, R 2C / f =} r 11 / f = 0.797, ν 2P -ν 2N = ν 6 -ν 5 = 13.2, f 12 / f = 2.04, f 3 / f = 1.64, (R 1R + | R _{2F |) / 2f = (r} 8 + | r 10 |) / 2f = 0.634

Embodiment 6 f = 1, F / 2.06, 2ω = 50.0 °, f _B = 0.856 r ₁ = -1.9093 d ₁ = 0.0367 n ₁ = 1.51602 ν ₁ = 56.80 r ₂ = 0.7123 d ₂ = 0.1061 r _{3 = 0.9353 d 3 = 0.1184 n 2} = 1.77250 ν 2 = 49.66 r 4 = -1.5354 d 4 = 0.0032 r 5 = 0.6328 d 5 = 0.1257 n 3 = 1.77250 ν 3 = 49.66 r 6 = 1.6125 d 6 = 0.0230 r 7 = 22.5335 d ₇ = 0.0367 n ₄ = 1.61293 ν ₄ = 37.00 r ₈ = 0.5741 d ₈ = 0.0793 r ₉ = ∞ (aperture) d ₉ = 0.0912 r ₁₀ = -0.4852 d ₁₀ = 0.0351 n ₅ = 1.69895 ν ₅ = 30.12 r _{11 = 0.8006 d 11 = 0.1113 n} 6 = 1.77250 ν 6 = 49.66 r 12 = -1.1803 d 12 = 0.0052 r 13 = 7.7749 d 13 = 0.0636 n 7 = 1.68893 ν 7 = 31.08 r 14 = -1.0482 ( aspherical) d ₁₄ = 0.0081 r ₁₅ = -13.3429 d ₁₅ = 0.0813 n ₈ = 1.83481 ν ₈ = 42.72 r ₁₆ = -0.6910 d ₁₆ = 0.0032 r ₁₇ = -6.4450 d ₁₇ = 0.0351 n ₉ = 1.71736 ν ₉ = 29.51 r ₁₈ = 1.3063 Aspherical surface coefficient P = 1.00 00, E = 0.14274 × 10, F = 0.29763 × 10, G = −0.26645 × 10 ² , H = 0.18021 × 10 ³ D ₂₃ = 0.025 (r _b + r _a ) / (r _b -r _a ) = (r ₂ + r ₁ ) / (r ₂ -r ₁ ) = -0.457, (r _d + r _c ) / (r _d -r _c ) = (r ₁₈ + r ₁₇ ) / (r ₁₈ -r ₁₇ ) =- _{0.663, f 1 (1) /} f = -1.001, R 2C / f = r 11 / f = 0.801, ν 2P -ν 2N = ν 6 -ν 5 = 19.5, f 12 / f = 1.82, f 3 / f _{= 2.00, (R 1R + |} R 2F |) / 2f = (r 8 + | r 10 |) / 2f = 0.530

Example 7 f = 1, F / 2.05, 2ω = 50.0 °, f _B = 0.848 r ₁ = −2.4360 d ₁ = 0.0367 n ₁ = 1.51742 ν ₁ = 52.41 r ₂ = 0.7027 d ₂ = 0.0913 r _{3 = 0.9814 d 3 = 0.0994 n 2} = 1.77250 ν 2 = 49.66 r 4 = -1.5784 d 4 = 0.0029 r 5 = 0.6788 d 5 = 0.1283 n 3 = 1.77250 ν 3 = 49.66 r 6 = 1.3709 d 6 = 0.0281 r 7 = -15.8784 d ₇ = 0.0367 n ₄ = 1.56444 ν ₄ = 43.78 r ₈ = 0.6879 d ₈ = 0.0859 r ₉ = ∞ (aperture) d ₉ = 0.1127 r ₁₀ = -0.5252 d ₁₀ = 0.0367 n ₅ = 1.69895 ν ₅ = 30.12 _{r 11 = 0.6292 d 11 = 0.1099} n 6 = 1.78590 ν 6 = 44.18 r 12 = -1.3779 d 12 = 0.0032 r 13 = -10.7690 d 13 = 0.0659 n 7 = 1.78590 ν 7 = 43.90 r 14 = -1.0524 ( aspherical _{) d 14 = 0.0081 r 15 =} -35.6603 d 15 = 0.0852 n 8 = 1.78590 ν 8 = 44.18 r 16 = -0.6559 d 16 = 0.0032 r 17 = -2.5685 d 17 = 0.0367 n 9 = 1.62004 ν 9 = 36.25 r 18 = 1.7204 Aspherical surface coefficient P = 1 .0023, E = 0.12162 x 10, F = 0.32914 x 10, G = -0.22817 x 10 ² , H = 0.17658 x 10 ³ D ₂₃ = 0.024 (r _b + r _a ) / (r _b -r _a ) = ( r ₂ + r ₁ ) / (r ₂ -r ₁ ) =-0.552, (r _d + r _c ) / (r _d -r _c ) = (r ₁₈ + r ₁₇ ) / (r ₁₈ -r ₁₇ ) = _{-0.198, f 1 (1) /} f = -1.050, R 2C / f = r 11 / f = 0.629, ν 2P -ν 2N = ν 6 -ν 5 = 14.1, f 12 / f = 2.08, f 3 / _{f = 1.71, (R 1R +} | R 2F |) / 2f = (r 8 + | r 10 |) / 2f = 0.607

Embodiment 8 f = 1, F / 2.05, 2ω = 50.0 °, f _B = 0.854 r ₁ = -1.9972 d ₁ = 0.0367 n ₁ = 1.54814 ν ₁ = 45.78 r ₂ = 0.7352 d ₂ = 0.1045 r _{3 = 0.9411 d 3 = 0.1191 n 2} = 1.77250 ν 2 = 49.66 r 4 = -1.6247 d 4 = 0.0032 r 5 = 0.6619 d 5 = 0.1258 n 3 = 1.77250 ν 3 = 49.66 r 6 = 1.4523 d 6 = 0.0237 r 7 = 6.2158 d ₇ = 0.0367 n ₄ = 1.51112 ν ₄ = 60.48 r ₈ = 0.5767 d ₈ = 0.0863 r ₉ = ∞ (aperture) d ₉ = 0.0966 r ₁₀ = -0.4796 d ₁₀ = 0.0367 n ₅ = 1.68893 ν ₅ = 31.08 r _{11 = 0.6057 d 11 = 0.1099 n} 6 = 1.77250 ν 6 = 49.66 r 12 = -1.1992 d 12 = 0.0032 r 13 = 16.2099 d 13 = 0.0637 n 7 = 1.66524 ν 7 = 55.12 r 14 = -1.0324 ( aspherical) d _{14 = 0.0086 r 15 = -5.6658 d} 15 = 0.0795 n 8 = 1.78590 ν 8 = 44.18 r 16 = -0.6516 d 16 = 0.0032 r 17 = -3.1496 d 17 = 0.0367 n 9 = 1.54814 ν 9 = 45.78 r 18 = 1.3421 Aspherical surface coefficient P = 1.000 0, E = 0.15445 × 10, F = 0.29928 × 10, G = -0.12397 × 10 ² , H = 0.87032 × 10 ² D ₂₃ = 0.026 (r _b + r _a ) / (r _b -r _a ) = (r ₂ + r ₁ ) / (r ₂ -r ₁ ) = -0.462, (r _d + r _c ) / (r _d -r _c ) = (r ₁₈ + r ₁₇ ) / (r ₁₈ -r ₁₇ ) =- _{0.402, f 1 (1) /} f = -0.976, R 2C / f = r 11 / f = 0.606, ν 2P -ν 2N = ν 6 -ν 5 = 18.6, f 12 / f = 1.80, f 3 / f _{= 2.00, (R 1R + |} R 2F |) / 2f = (r 8 + | r 10 |) / 2f = 0.528

Example 9 f = 1, F / 2.06, 2ω = 50.0 °, f _B = 0.85 r ₁ = −2.3633 d ₁ = 0.0432 n ₁ = 1.56732 ν ₁ = 42.83 r ₂ = 0.7542 d ₂ = 0.1154 r _{3 = 0.9661 d 3 = 0.1332 n 2} = 1.83481 ν 2 = 42.72 r 4 = -1.8007 d 4 = 0.0032 r 5 = 0.6562 d 5 = 0.1190 n 3 = 1.83481 ν 3 = 42.72 r 6 = 1.8546 d 6 = 0.0189 r 7 = 21.1328 d ₇ = 0.0324 n ₄ = 1.63636 ν ₄ = 35.37 r ₈ = 0.5692 d ₈ = 0.0961 r ₉ = ∞ (aperture) d ₉ = 0.1213 r ₁₀ = -0.5440 d ₁₀ = 0.0442 n ₅ = 1.71736 ν ₅ = 29.51 r ₁₁ = 0.7493 d ₁₁ = 0.1122 n ₆ = 1.77250 v ₆ = 49.66 r ₁₂ = -1.3459 d ₁₂ = 0.0059 r ₁₃ = ｄ d ₁₃ = 0.0678 n ₇ = 1.68893 v ₇ = 31.08 r ₁₄ = -1.2132 (aspherical surface) d ₁₄ = 0.0108 r ₁₅ = -16.9861 d ₁₅ = 0.0765 n ₈ = 1.83481 ν ₈ = 42.72 r ₁₆ = -0.7368 d ₁₆ = 0.0032 r ₁₇ = -16.0531 d ₁₇ = 0.0337 n ₉ = 1.74077 ν ₉ = 27.79 r ₁₈ = 1.8424 Aspherical coefficient P = 1. 0000, E = 0.111 15 × 10, F = 0.89669, G = 0.12796 × 10 D ₂₃ = 0.032 (r _b + r _a ) / (r _b -r _a ) = (r ₂ + r ₁ ) / (r ₂ -r _{1) = -0.516, (r d} + r c) / (r d -r c) = (r 18 + r 17) / (r 18 -r 17) = -0.794, f 1 (1) / f = - _{1.003, R 2C / f = r} 11 / f = 0.749, ν 2P -ν 2N = ν 6 -ν 5 = 20.2, f 12 / f = 2.33, f 3 / f = 1.55, (R 1R + | R 2F | _{) / 2f = (r 8 +} | r 10 |) / 2f = 0.557

Example 10 f = 1, F / 2.06, 2ω = 50.0 °, f _B = 0.85 r ₁ = −2.4014 d ₁ = 0.0432 n ₁ = 1.67732 ν ₁ = 42.83 r ₂ = 0.7613 d ₂ = 0.1152 r _{3 = 0.9686 d 3 = 0.1347 n 2} = 1.83481 ν 2 = 42.72 r 4 = -1.8248 d 4 = 0.0032 r 5 = 0.6561 d 5 = 0.1191 n 3 = 1.83481 ν 3 = 42.72 r 6 = 1.8625 d 6 = 0.0188 r 7 = 21.1363 d ₇ = 0.0324 n ₄ = 1.63636 ν ₄ = 35.37 r ₈ = 0.5658 d ₈ = 0.1029 r ₉ = (aperture) d ₉ = 0.1221 r ₁₀ = -0.5436 d ₁₀ = 0.0441 n ₅ = 1.71736 ν ₅ = 29.51 r _{11 = 0.7453 d 11 = 0.1122 n} 6 = 1.77250 ν 6 = 49.66 r 12 = -1.4147 d 12 = 0.0057 r 13 = ∞ d 13 = 0.0678 n 7 = 1.67270 ν 7 = 32.10 r 14 = -1.2176 ( aspherical) d ₁₄ = 0.0108 r ₁₅ = -22.3691 d ₁₅ = 0.0766 n ₈ = 1.83481 ν ₈ = 42.72 r ₁₆ = -0.7387 d ₁₆ = 0.0032 r ₁₇ = -41.0093 d ₁₇ = 0.0337 n ₉ = 1.74077 ν ₉ = 27.79 r ₁₈ = 1.9045 Aspheric coefficient P 1.0000, E = 0.11102 × 10, F = 0.81520, G = 0.16924 × 10 D 23 = 0.032 (r b + r a) / (r b -r a) = (r 2 + r 1) / (r 2 -r _{1) = -0.519, (r d} + r c) / (r d -r c) = (r 18 + r 17) / (r 18 -r 17) = -0.909, f 1 (1) / f = - _{1.014, R 2C / f = r} 11 / f = 0.745, ν 2P -ν 2N = ν 6 -ν 5 = 20.2, f 12 / f = 2.59, f 3 / f = 1.44, (R 1R + | R 2F | _{) / 2f = (r 8 +} | r 10 |) / 2f = 0.555 However r _1, r _2, ··· the radius of curvature of each lens surface, d
_.. , D ₂ ,...
₁ , n ₂ ,... Are the refractive indices of each lens, ν ₁ , ν ₂ ,.
The Abbe number of each lens, f _B is the back focus, D ₂₃
Is the distance between the second and third units when the imaging magnification (β) is -0.2.

The first to fourth embodiments have lens configurations as shown in FIGS. 1 to 4, respectively, and the sixth to eighth embodiments have lens configurations as shown in FIGS. 6 to 8, respectively. That is, the first group G ₁ having a positive refractive power, the stop, the second group G _2, and the third group G ₃ having a positive refractive power.
And The first group G ₁ is the most object side of the most places the negative lens on the image side of which, the most negative lens on the image side is characterized by that the surface on the image side concave surface. Second group G ₂
Has a positive refractive power as a whole. Third group G ₃
Is a negative lens whose most image-side lens is concave on the image side. The above conditions are satisfied. Each of these embodiments has an aspheric surface whose positive refractive power becomes weaker toward the periphery of the lens. Therefore, when the aspherical surface is used for the convex surface, the radius of curvature increases toward the lens periphery, and when the aspherical surface is used for the concave surface, the radius of curvature decreases toward the lens periphery. This aspherical surface is mainly for correcting spherical aberration and coma.

The fifth embodiment has a configuration as shown in FIG. In the first embodiment and the like, the cemented lens in which the second group is cemented with the biconcave lens and the positive lens in the order from the object side to the second group is arranged from the object side. In the fifth embodiment, the biconcave lens and the positive lens are combined. A negative lens having a convex surface facing the image side is further cemented to the image side of the cemented lens.

Further, Embodiments 9 and 10 correspond to FIGS. 9 and 1 respectively.
0, which is similar to the first embodiment, etc.
The difference is that the second group has a negative refractive power as a whole.

In the embodiments, the shape of the aspherical surface is represented by the following equation when the x-axis is taken along the optical axis and the y-axis is taken in the direction perpendicular to the optical axis. Where r is the paraxial radius of curvature, P, E, F, G, H,.
Is an aspheric coefficient.

[0053]

The lens system of the present invention is a standard lens for a single-lens reflex camera, has a focal length near the diagonal of the film, an F-number of about 2.0, and is very good in performance over the entire screen. have.

The lens system according to the present invention has a photographing magnification of 0 to -1 / 1 / by adopting an appropriate floating mechanism.
Good performance is maintained in the range of about 5 times.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a seventh embodiment of the present invention.

FIG. 8 is a sectional view of Embodiment 8 of the present invention.

FIG. 9 is a sectional view of Embodiment 9 of the present invention.

FIG. 10 is a sectional view of Embodiment 10 of the present invention.

FIG. 11 is an aberration curve diagram for an object point at infinity according to the first embodiment of the present invention.

FIG. 12 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the first embodiment of the present invention.

FIG. 13 is an aberration curve diagram for an object point at infinity according to the second embodiment of the present invention.

FIG. 14 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the second embodiment of the present invention.

FIG. 15 is an aberration curve diagram for an object point at infinity according to a third embodiment of the present invention.

FIG. 16 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the third embodiment of the present invention.

FIG. 17 is an aberration curve diagram for an object point at infinity according to a fourth embodiment of the present invention.

FIG. 18 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the fourth embodiment of the present invention.

FIG. 19 is an aberration curve diagram for an object point at infinity according to a fifth embodiment of the present invention.

FIG. 20 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the fifth embodiment of the present invention.

FIG. 21 is an aberration curve diagram for an object point at infinity according to a sixth embodiment of the present invention.

FIG. 22 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the sixth embodiment of the present invention.

FIG. 23 is an aberration curve diagram for an object point at infinity according to a seventh embodiment of the present invention.

FIG. 24 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the seventh embodiment of the present invention.

FIG. 25 is an aberration curve diagram for an object point at infinity according to the eighth embodiment of the present invention.

FIG. 26 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the eighth embodiment of the present invention.

FIG. 27 is an aberration curve diagram for an object point at infinity according to a ninth embodiment of the present invention.

FIG. 28 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the ninth embodiment of the present invention.

FIG. 29 is an aberration curve diagram for an object point at infinity according to a tenth embodiment of the present invention.

FIG. 30 is an aberration curve diagram for a short-distance object point at a photographing magnification of −0.2 according to the tenth embodiment of the present invention.

Continuation of the front page (56) References JP-A-1-145617 (JP, A) JP-A-5-80252 (JP, A) JP-A-3-208004 (JP, A) JP-A-59-152414 (JP) JP-A-51-148421 (JP, A) JP-A-2-285313 (JP, A) JP-A-1-214812 (JP, A) JP-A-37-5536 (JP, A) 55-35322 (JP, A) JP-A-55-59216 (JP, A) JP-A-63-205625 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00 -17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (4)

(57) [Claims] 1. A first group having a positive refractive power, in order from the object side,
An aperture stop, a second unit, and a third unit having a positive refractive power, wherein the first unit has a negative lens arranged closest to the object side and a negative lens arranged concave toward the image side arranged closest to the image side. In the second group, the biconcave lens and the positive lens are cemented in order from the object side.
Double cemented lens or biconcave lens and positive lens in order from the object side
Lens of three cemented lenses in which lens and lens are joined
Is obtained by placing the components, the third group are those arranged on the most image side negative lens having a concave surface on the image side, the imaging lens satisfying the following conditions (1) to (3). (1) −2 <(r _b + r _a ) / (r _b −r _a ) <0 (2) −3 <(r _d + r _c ) / (r _d −r _c ) <0 (3) − _{1.6 <f 1 (1) /f<-0.6} f is the focal length of the entire system, f _{1 (1)} is the focal length of the negative lens disposed on the most object side of the first group, r _a, r _b is the radius of curvature of the object-side surface and image side surface of the negative lens disposed on the most object side of the first group radius, r _c, r _d is the negative lens disposed on the most image side of the third group This is the radius of curvature of the object-side surface and the image-side surface. 2. A first group having a positive refractive power, in order from the object side,
An aperture, a second unit, and a third unit having a positive refractive power. The third unit is a unit in which a negative lens having a concave surface facing the image side is disposed closest to the image side. The second lens unit and the second lens unit are unified to the object side, and the third lens unit is extended to the object side so as to increase the distance between the second lens unit and the second lens unit to focus on a short-distance object.
A photographing lens satisfying the following conditions (7) and (8). (7) 1.2 <f ₁₂ / f <3 (8) 1.2 <f ₃ / f <3 where f is the focal length of the entire system, f ₁₂ is the combined focal length of the first and second groups, f ₃ is the focal length of the third group. 3. The photographing lens according to claim 1, wherein the following conditions (4), (5), and (6) are satisfied. (4) 0.3 <R _2C /f<1.2 (5) 8 <ν _2P −ν _2N <40 (6) 0.4 <(R _1R + | R _2F |) / 2f <2, R _2F
<0 where R _1R is the radius of curvature of the image side surface of the negative lens closest to the image side of the first group, R _2F is the radius of curvature of the object side surface of the negative lens closest to the object side of the second group, and R _2C is The radii of curvature of the cemented surfaces convex to the object side of the cemented lens of the second group, ν _2N and ν _2P, are the most object side biconcave lens of the cemented lens of the second group and the tangent thereto, respectively.
The Abbe number of the positive lens to be combined . 4. The photographing lens according to claim 2, wherein the following condition (9) is satisfied. _{(9) -3 <(r d} + r c) / (r d -r c) <0 However r _c, r _d is the object-side surface of the negative lens disposed respectively closest to the image side of the third group and the image The radius of curvature of the side surface.