JP3518886B2 - High-performance wide-angle 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 high-performance wide-angle lens suitable for a photographic lens, particularly a camera for a lens shutter.

[0002]

2. Description of the Related Art Conventionally, as a wide-angle photographing lens used for a lens shutter camera, a triplet type and a tesser type have been known for a long time. These types of photographic lenses have a small number of lenses and are small in size, but cannot be said to have high performance, and in particular, tend to have a large bulge on the sagittal image plane, and have large astigmatism.

A conventional photographic lens is disclosed in Japanese Patent Application Laid-Open No. 55-105.
In the lens system disclosed in Japanese Patent No. 216, the sagittal image plane is greatly expanded, the astigmatic difference increases toward the periphery of the screen, and the chromatic aberration of magnification is not sufficiently corrected. Therefore, it is difficult to maintain high performance around the screen.

Further, most of the triplet type and the tesser type lens systems are behind apertures. Therefore, it is necessary to secure the peripheral light amount and to prevent the diameter of the front lens from becoming large.

The lens system described in Japanese Patent Application Laid-Open No. Sho 60-121413 is a lens system in which a negative meniscus lens is arranged on the image side of a Tessar type lens system. If a negative lens is added to the image plane side of a Tessar type lens as in this conventional lens system, the principal point position can be located before the front lens, so that the entire length of the lens system (first lens system) This is very effective for shortening the distance from the surface to the image plane). In particular, when the negative lens is arranged near the image plane position away from the lens on the object side, the effect of the telephoto type increases and the overall length can be shortened.

However, when the final negative lens is brought closer to the image plane, the occurrence of astigmatism and distortion becomes large. In a conventional lens system, the shape of the negative lens is formed as a meniscus lens having a convex surface facing the image surface side so as to suppress occurrence of astigmatism and distortion. In this way, it is possible to shorten the overall length of the lens system, but it is necessary to secure a certain air gap on the object side of the negative lens, and the length of the lens system (from the first lens surface to the final Distance to the surface).

[0007] Many recent compact cameras are of a type in which a taking lens is retracted so that the camera becomes thinner when being carried. It is preferable that the photographing lens used in such a retractable camera has a short configuration length of the lens system.

The lens system described in Japanese Patent Application Laid-Open No. Sho 60-121413 is a triplet type lens system in which a negative lens is provided on the image plane side, and the negative lens is a biconcave lens. This lens system has a configuration similar to a behind-the-spot type optical system of the Tessar type, in which the cemented lens of the Tessar type lens system is separated. Therefore, it has the drawbacks of the above-mentioned optical system of the Tesser type and does not have satisfactory optical performance.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a simple configuration with a small number of lenses, good optical performance up to the periphery of the screen, and a short lens configuration length, particularly an image suitable for a retractable camera. An object of the present invention is to provide a wide-angle photographing lens having an angle of 60 ° or more.

[0010]

The wide-angle lens according to the present invention comprises:
A positive first lens group having an aspheric surface, in order from the object side;
It is composed of a negative second lens group, a positive third lens group, and a negative fourth lens group whose image-side surface is a concave surface having a stronger curvature than the object-side surface.

In the lens system having a configuration like a wide-angle lens according to the present invention, it is necessary to bring the fourth lens group closer to the third lens group in order to shorten the configuration length. When the fourth lens group is brought closer to the third lens group in this manner, when the fourth lens group is a meniscus-shaped lens as in the conventional example, the position of the principal point of the combination from the first lens group to the third lens group is determined. The distance between the principal points of the fourth lens group is reduced, the effect of the telephoto type is reduced, and the overall length is increased.

In the present invention, the curvature of the fourth lens unit on the object side is reduced and the curvature of the fourth lens unit on the image plane side is increased in the negative direction. By bringing the position as close to the image plane as possible,
The distance between the combined principal point position of the lens group to the third lens group and the principal point position of the fourth lens group was not reduced, and the overall length of the lens system was not increased .

However, when the fourth lens group is formed as described above, the fourth lens group has a shape close to aplanatic, so that the amount of spherical aberration is small but the amount of astigmatism and distortion is large. become.

According to the present invention, astigmatism and distortion generated in the fourth lens group are corrected by using an aspheric surface in the first lens group. The first lens group has a positive refractive power and the fourth lens group has a negative refractive power.
It is impossible for the first lens group to correct astigmatism and distortion generated in the lens groups. For this reason, in the present invention, the first lens group uses an aspheric surface whose negative refractive power becomes stronger toward the periphery of the lens, and the aberration generated in the first lens group is generated in the negative lens group. In the same manner, astigmatism and distortion generated in the fourth lens group are corrected by the first lens group having an aspheric surface.

The spherical aberration and coma generated by the third lens group are simultaneously corrected by the spherical aberration and coma generated by the aspheric surface of the first lens group.

Next, it is preferable that the first lens group is a positive meniscus lens having a convex surface facing the object side, thereby reducing aberrations generated on the spherical surface of the first lens group, that is, aberrations generated by the positive lens. And the burden on the aspherical surface can be reduced.

As described above, the occurrence of spherical aberration and coma due to the aspherical surface of the first lens unit can be reduced, and the spherical aberration and coma due to the aspherical surface can be prevented from being overcorrected.

Preferably, the second lens group is a meniscus lens having a convex surface facing the object side. If the second lens group is a meniscus lens with the convex surface facing the object side,
The occurrence of spherical aberration, coma, and astigmatism occurring on the object-side surface can be suppressed, and these aberrations caused by the aspheric surface of the first lens unit are prevented from being overcorrected.
The aberration of the entire lens system can be balanced. Further, performance deterioration due to eccentricity of the second lens group can be reduced.

The third lens group includes, in order from the object side, a biconvex lens and a negative meniscus lens having a convex surface facing the image surface side. The image side surface of the positive lens (biconvex lens) and the negative lens surface Higher-order spherical aberration is generated on the object-side surface, whereby high-order spherical aberration generated on the image-side surface of the second lens group can be balanced, and the aberration as a whole can be favorably corrected. . In addition, the positive lens and the negative lens may be joined to generate a higher-order spherical aberration by the joint surface. If the third lens group is a cemented lens as described above, it is easy to suppress eccentricity, which is advantageous in terms of manufacturing. The most image side surface of the third lens group has a convex surface facing the image side, so that astigmatism and distortion generated on this surface can be reduced, and spherical aberration and coma generated on this surface can be reduced. Aberration is the first
Correction can be made with the aspherical surface of the lens group, and correction can be made with good balance as a whole.

It is preferable that the fourth lens unit satisfies the following condition.

(1) 0.1 <(R _4a + R _4b ) / (R
_{4a- R4b} ) <1.5 where _R4a is the radius of curvature of the object-side surface of the fourth lens unit,
R _4b is the radius of curvature of the image-side surface of the fourth lens group.

When the lower limit of 0.1 to condition (1) is exceeded, the curvature of the object-side surface of the fourth lens unit becomes too strong with respect to the curvature of the image-side surface, and the spherical surface generated by the fourth lens unit. Aberration becomes large, the distance between the third lens unit and the fourth lens unit must be increased, and the fourth lens unit must be arranged at a position close to the image plane.
The lens configuration length becomes large, and the object of the present invention cannot be achieved. When the value exceeds the upper limit of 1.5 of the condition (1), the curvature of the image-side surface becomes too strong with respect to the curvature of the object-side surface, so that astigmatism and distortion occur too much. Can not be corrected even with an aspheric surface. Although the lens length can be shortened, the position of the outer periphery of the surface of the fourth lens group on the image plane side on the optical axis is much closer to the image plane side than the top, so that the total length of the lens barrel becomes large and the camera is collapsed. It becomes difficult to reduce the thickness.

When the focal length of the fourth lens unit is f ₄ and the focal length of the entire lens system when focused on an object point at infinity is f, the following condition (2) must be satisfied. Is desirable.

(2) 0.5 <| f ₄ /f|<2.5 When the lower limit of 0.5 to condition (2) is exceeded, the refractive power of the fourth lens unit becomes too strong. It becomes difficult to correct the astigmatism and distortion that occur, and the curvatures of the surfaces on the object side and the image plane side increase, and the total length of the lens system and the lens frame increases for the above-described reason. If the upper limit of 2.5 is exceeded, the fourth
Since the refracting power of the lens group becomes too weak, the principal point position is shifted to the image plane side, and the telephoto ratio of the lens system becomes large.
As described above, when the telephoto ratio becomes large, the amount of collapsing must be increased in order to make the camera body thinner, and a mechanism for that becomes difficult, and the amount of eccentricity of the lens system tends to increase. Further, since the refractive power of the fourth lens group is effective in correcting the Petzval sum, it is difficult to balance the Petzval sum if the upper limit of 2.5 of the condition (2) is exceeded.

Next, the focusing method in the lens system of the present invention will be described.

In general, focusing from an object point at infinity to an object point at a short distance can be performed by extracting the entire lens system. However, focusing can also be performed by the following method. High performance can be maintained over the whole area to the object point.

That is, the applicant's patent application, Japanese Patent Application No. Hei.
As in the method described in No. -21207, focusing is performed from an object point at infinity to an object point at a short distance while increasing the air gap between the second lens unit and the third lens unit.

In the lens system according to the present invention, when focusing is performed by the whole hollowing-out method, the fluctuation of astigmatism becomes very large when the practical photographing magnification at the time of close-up photographing becomes about -1/10. And the performance is significantly deteriorated. Therefore, a so-called floating method is adopted to stabilize the optical performance at a short-distance object point and to enable focusing to a closer object point. As a result, fluctuations of astigmatism that cannot be completely corrected in the case of focusing by whole drawing can be suppressed by slightly increasing the distance between the second lens unit and the third lens unit.

In order to stabilize the optical performance when focusing on an object at a short distance, it is preferable that the aperture stop is disposed between the second lens unit and the third lens unit. Conventionally, there has been known a lens system that performs floating by changing an air interval other than the air interval in which the diaphragm is arranged. This lens system can correct aberrations at a reference wavelength, but has off-axis chromatic aberration. However, it was difficult to correct them at the same time.

In the present invention, floating is performed by changing the distance between the air where the aperture stop is disposed, and various aberrations, particularly astigmatism, chromatic aberration of magnification, and coma when focusing on an object at a short distance. Fluctuations can be minimized.

Here, in order to further stabilize the performance when focusing on a short-distance object, it is desirable to satisfy the following conditions (3) and (4).

(3) 0.01 <| f ₃₄ / f ₁₂ | <0.25 (4) 0.01 <| f / f ₁₂ | <0.3 where f ₁₂ is the first lens group and the second lens group composite focal length of the lens group, f ₃₄ is a composite focal length of the third lens group and the fourth lens group.

Condition (3) is a condition of the ratio of the focal length of the front group on the object side to the rear group on the image plane side, ie, the distribution of the refractive power between the front group and the rear group, at the boundary of the air space for floating. It is specified. When the value exceeds the upper limit of 0.25 of the condition (3), the refractive power of the front group becomes too strong, and the amount of various aberrations in the front group increases, and it becomes difficult to correct them in the rear group.
If the lower limit of 0.01 is exceeded, it is effective for correcting off-axis aberrations at an object point at infinity, but the fluctuation of aberrations when focusing on a short-distance object point increases and the performance deteriorates, which is good. It becomes difficult to focus on a closer object while maintaining excellent optical performance.

Condition (4) defines the ratio of the focal length of the front group to the focal length of the entire lens system. If the condition exceeds the upper limit of 0.3, the refractive power of the front group becomes too strong. The amount of occurrence of various aberrations in the front group becomes large, and it becomes difficult to correct them in the rear group. If the lower limit of 0.01 to condition (4) is exceeded, the refracting power of the rear group becomes too strong, which is effective for correcting various aberrations at an object point at infinity. Becomes large and it becomes difficult to obtain a high photographing magnification.

When the third lens group is constituted by a cemented lens as described above, it is desirable to satisfy the following conditions (5) and (6).

(5) 0.2 <| f · (n _P −n _N )
/R|<1.4 (6) 5 <ν _P −ν _N <20 where n _P and ν _P are the refractive index and Abbe number of the positive lens of the third lens unit, and n _N and ν _N are the third. These are the refractive index and Abbe number of the negative lens in the lens group.

The condition (5) is a condition for correcting spherical aberration and coma in a well-balanced manner. If the upper limit of 1.4 of the condition (5) is exceeded, the amount of generation of higher-order aberrations at the cemented surface increases. Overcorrection. Petzval also increases. If the lower limit of 0.2 is exceeded, the aberration at the cemented surface will be undercorrected, making it difficult to correct spherical aberration and coma.

Condition (6) is a condition for balancing axial chromatic aberration and higher-order aberrations generated at the cemented surface. If the upper limit of 20 is exceeded, axial chromatic aberration will be overcorrected, and the lower limit will be reduced. If it exceeds 5, the curvature of the cemented surface becomes strong to correct axial chromatic aberration, and high-order aberrations are overcorrected.

When the ranges of the above conditions (1) to (6) are set to the following conditions (1 ') to (6'), it is more preferable for miniaturization and high performance of the lens system.

(1 ′) 0.2 <(R _4a + R _4b ) /
(R _4a -R _4b ) <1.0 (2 ′) 0.8 <| f ₄ /f|<2.0 (3 ′) 0.04 <| f ₃₄ / f ₁₂ | <0.15 (4 ') 0.05 <| f / f ₁₂ | <0.18 (5 ′) 0.3 <| f · (n _P −n _N ) / R | <
1.0 (6 ′) 7 <ν _P −ν _N <16

[0041]

Next, embodiments of the high-performance wide-angle lens according to the present invention will be described. Example 1 f = 35.0, F / 2.86, ω = 31.45 ° r ₁ = 12.6603 d ₁ = 4.411 n ₁ = 1.78590 ν ₁ = 44.19 r ₂ = 29.9408 (aspherical surface) d ₂ = 0.524 r ₃ = 35.3188 d ₃ = 1.150 n ₂ = 1.72825 v ₂ = 28.46 r ₄ = 10.6912 d ₄ = 3.800 (variable) r ₅ = ∞ (aperture) d ₅ = 1.800 r ₆ = 47.2124 d ₆ = 3.433 n ₃ = 1.77250 v ₃ = 49.60 r ₇ = _{-12.5906 d 7 = 1.200 n 4 =} 1.59270 ν 4 = 35.30 r 8 = -30.8498 d 8 = 1.665 r 9 = -511.9636 d 9 = 1.000 n 5 = 1.51633 ν 5 = 64.15 r 10 = 28.8440 aspherical coefficients (second Surface) A ₄ = 5.7046 × 10 ^-5 , A ₆ = -2.2546 × 10 ^-7 A ₈ = 5.8917 × 10 ^-9 , A ₁₀ = -5.1372 × 10 ^-12 Focusing distance Infinite object point Closest (40cm) d _{4 3.800 4.128 f B 21.782 25.575 (R} 4a + R 4b) / (R 4a -R 4b) = 0.89, | f 4 /f|=1.51 | f 34 / f 12 | = 0.11, | f / f 12 | = 0.12 | _{f · (n P -n N)} /R|=0.50,ν P -ν N = 14.3

Example 2 f = 35.0, F / 2.86, ω = 31.36 ° r ₁ = 12.4241 d ₁ = 4.183 n ₁ = 1.78590 ν ₁ = 44.19 r ₂ = 19.0646 (aspherical surface) d ₂ = 0.616 r ₃ = 22.8606 _{d 3 = 1.150 n 2 = 1.72825} ν 2 = 28.46 r 4 = 10.1121 d 4 = 3.148 ( variable) r ₅ = ∞ _{(stop) d 5 = 1.800 r 6 =} 31.0376 d 6 = 4.655 n 3 = 1.77250 ν 3 = 49.60 _{r 7 = -9.3182 d 7 = 1.200} n 4 = 1.59270 ν 4 = 35.30 r 8 = -26.8650 d 8 = 0.783 r 9 = -52.4130 d 9 = 1.000 n 5 = 1.51633 ν 5 = 64.15 r 10 = 26.6689 ( aspherical Aspheric coefficient (second surface) A ₄ = 5.6311 × 10 ^-5 , A ₆ = 7.0804 × 10 ^-7 A ₈ = -7.7295 × 10 ^-9 , A ₁₀ = 1.8481 × 10 ^-10 (tenth surface) ₄ = 5.0390 x 10 ^-5 , A ₆ = -7.8256 x 10 ^-7 A ₈ = 1.7028 x 10 ^-8 , A ₁₀ = -1.0165 x 10 ^-10 Focusing distance Infinite object point Closest (40cm) d ₄ 3.148 3.248 f _{B 23.661 27.449 (R 4a + R} 4b) / (R 4a -R 4b) = 0.33, | f 4 / f | _{0.97 | f 34 / f 12 |} = 0.07, | f / f 12 | = 0.10 | f · (n P -n N) /R|=0.68,ν P -ν N = 14.3

Example 3 f = 35.0, F / 2.86, ω = 31.29 ° r ₁ = 12.9474 (aspherical surface) d ₁ = 3.369 n ₁ = 1.80610 ν ₁ = 40.95 r ₂ = 60.3960 (aspherical surface) d ₂ = 0.753 r ₃ = 36.0722 d ₃ = 1.143 n ₂ = 1.71736 ν ₂ = 29.51 r ₄ = 8.2184 d ₄ = 3.220 (variable) r ₅ = ∞ (aperture) d ₅ = 1.800 r ₆ = 38.0541 d ₆ = 4.249 n ₃ = 1.77250 ν ₃ = 49.60 r ₇ = -7.7743 d ₇ = 1.500 n ₄ = 1.58144 ν ₄ = 40.75 r ₈ = -30.0205 d ₈ = 0.102 r ₉ = -117.6754 d ₉ = 1.068 n ₅ = 1.56384 ν ₅ = 60.70 r ₁₀ = 26.0596 (aspherical) aspherical coefficients (first ^{_{surface) A 4 = -4.4042 × 10 -5}} , A 6 = -5.5192 × 10 -7 A 8 = -4.0919 × 10 -9, A 10 = -7.4208 × 10 - ¹² (Second surface) A ₄ = -1.7360 × 10 ^-5 , A ₆ = -6.0721 × 10 ^-7 A ₈ = 9.1256 × 10 ^-9 , A ₁₀ = -6.6594 × 10 ^-11 (10th surface) A _{4 ^{= 2.8974 × 10 -5, A 6}} = -1.7627 × 10 -7 A 8 = 6.0987 × 10 -9, A 10 = -8.7232 × Mu 10 ^-12 focusing distance Object point closest _{(40cm) d 4 3.220 3.230 f} B 25.017 28.801 (R 4a + R 4b) / (R 4a -R 4b) = 0.64, | f 4 /f|=1.08 | f 34 / f 12 | = 0.07, | f / f ₁₂ | = 0.09 | f · (n _P −n _N ) /R|=0.86, v _P −v _N = 8.85 where r ₁ , r ₂ ,...
_.. , D ₂ ,...
₁ , n ₂ ,... Are the refractive indices of each lens, ν ₁ , ν ₂ ,.
Is the Abbe number of each lens.

Examples 1 to 3 are lens systems having the structures shown in FIGS. 1 to 3, respectively. The aberration situation in the first embodiment is as follows.
As shown in FIGS. 4A, 4B, 5A, and 5B, FIG.
4B shows spherical aberration, astigmatism, chromatic aberration of magnification and distortion for the object point at infinity, and FIG. 4B shows coma aberration for the object point at infinity.
5A shows spherical aberration, astigmatism, chromatic aberration of magnification, and distortion for an object point distance of 40 cm, and FIG. 5B shows an object point distance of 40c.
This is coma aberration with respect to m. 6A, 6B, 7A, and 7B show the aberration states in Example 2. FIG. 6A shows spherical aberration, astigmatism, chromatic aberration of magnification, distortion, and FIG. Coma for distant objects,
FIG. 7A shows spherical aberration, astigmatism, chromatic aberration of magnification and distortion for an object point distance of 40 cm, and FIG. 7B shows an object point distance of 40c.
This is coma aberration with respect to m. 8A, FIG. 8B, FIG. 9A, and FIG. 9B. FIG. 8A shows spherical aberration, astigmatism, chromatic aberration of magnification, and distortion with respect to an object point at infinity, and FIG. FIG. 9A shows spherical aberration, astigmatism, chromatic aberration of magnification and distortion at an object point distance of 40 cm, and FIG.
Coma aberration with respect to cm.

The present invention includes the following lens systems in addition to those described in the claims. (1) The high-performance wide-angle lens according to (1), wherein the third lens group includes, in order from the object side, a biconvex positive lens and a negative meniscus lens having a convex surface facing the image surface side. . (2) In the lens system according to claim 1, when the radius of curvature of the fourth lens group on the object side is R _4a and the radius of curvature on the image plane side is R _4b , the following condition (1) is satisfied. High-performance wide-angle lens.

(1) 0.1 <(R _4a + R _4b ) / (R
_{4a- R4b} ) <1.5 (3) The high-performance wide-angle lens according to claim 2, wherein the image-side surface of the first lens group is aspheric. (4) The lens system described in (1) above,
A high-performance wide-angle lens whose lens group is a cemented lens. (5) The lens system described in (2), wherein
A high-performance wide-angle lens in which the image-side surface of the lens group is aspheric. (6) A high-performance wide-angle lens according to claim 2, wherein both surfaces of the first lens group are aspherical. (7) A high-performance wide-angle lens according to claim 1, wherein a brightness stop is arranged between the second lens group and the third lens group. (8) A high-performance wide-angle lens according to claim 1, wherein focusing from an object at infinity to an object at a short distance is performed by increasing the distance between the second lens group and the third lens group. (9) In the lens system of claim 1, when the focal length of the entire system at an infinite object point focusing f, and the focal length of the fourth lens group and the f _4, high to satisfy the following condition (2) High-performance wide-angle lens.

(2) 0.5 <| f ₄ /f|<2.5 (10) In the lens system according to claim 1, the focal length of the entire system at the time of focusing on an object point at infinity is f, and the first lens is When the combined focal length of the first lens unit and the second lens unit is f ₁₂ , and the combined focal length of the third and fourth lens units is f ₃₄ , a high-performance lens satisfying the following conditions (3) and (4) Wide-angle lens.

(3) 0.01 <| f ₃₄ / f ₁₂ | <0.25 (4) 0.01 <| f / f ₁₂ | <0.3 (11) Lens described in item (4) In the system, f is the focal length of the entire system at infinity focusing, and n _P and ν _P are the refractive index and Abbe number of the positive lens in the fourth lens group, respectively.
When the refractive index and Abbe number of the negative lens are n _N and ν _N , and the radius of curvature of the joint surface is R, the following conditions (5) and (6)
High-performance wide-angle lens that satisfies the requirements.

(5) 0.2 <| f · (n _P −n _N )
/R|<1.4 (6) 5 <ν _P −ν _N <20

[0050]

The wide-angle lens according to the present invention is a high-performance lens system having a simple structure with a small number of lenses, good performance up to the periphery of the film, and having an angle of view of 60 ° or more.

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

FIG. 5 is an aberration curve diagram for a short-distance object point according to the first embodiment of the present invention.

FIG. 6 is an aberration curve diagram for an object point at infinity according to a second embodiment of the present invention.

FIG. 7 is an aberration curve diagram for a short-distance object point according to the second embodiment of the present invention.

FIG. 8 is an aberration curve diagram for an object point at infinity according to a third embodiment of the present invention.

FIG. 9 is an aberration curve diagram for a short-distance object point according to the third embodiment of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-223408 (JP, A) JP-A-4-21114 (JP, A) JP-A-2-167516 (JP, A) JP-A-3-213 138612 (JP, A) JP-A-5-303036 (JP, A) JP-A-5-303037 (JP, A) JP-A-6-59189 (JP, A) JP-A-62-39811 (JP, A) JP-A-62-160413 (JP, A) JP-A-62-200315 (JP, A) JP-A-63-274904 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 13/00 G02B 9/00

Claims (13)

(57) [Claims] 1. A positive first lens having an aspheric surface in order from the object side.
A first lens unit including a second lens unit, a second negative lens unit, a third positive lens unit, and a fourth negative lens unit having a concave surface having a stronger curvature on the image side than on the object side; The lens group is a positive meniscus lens having a convex surface facing the object side, the second lens group is a negative meniscus lens having a convex surface facing the object side, and the third lens group is biconvex in order from the object side. A cemented lens consisting of a positive lens and a negative meniscus lens with the convex surface facing the image side,
The focal length of the entire system at the time of sing is f, and the positive
The refractive index and Abbe number of the lens are n _P and ν _P , respectively.
The refractive index and Abbe number of the lens are n _N and ν _N , respectively,
When the radius of curvature of R is R, the following conditions (5) and (6) are satisfied.
High-performance wide-angle lens to be added. (5) 0.2 <| f · (n P -n N) / R | <1.4 (6) 5 <ν P -ν N <20 2. When the radius of curvature of the object-side surface of the fourth lens group is R _4a and the radius of curvature of the image-side surface of the fourth lens group is R _4b , the following condition (1) is satisfied. The high-performance wide-angle lens according to claim 1. (1) 0.1 <( _R4a + _R4b ) / ( _{R4a- R4b} ) <1.5 3. The high-performance wide-angle lens according to claim 1, wherein an image-side surface of said first lens group is aspheric. 4. The high-performance wide-angle lens according to claim 2, wherein an image-side surface of said fourth lens group is aspheric. 5. The high-performance wide-angle lens according to claim 1, wherein both surfaces of said first lens group are aspherical. 6. The high-performance wide-angle lens according to claim 1, wherein a brightness stop is arranged between said second lens group and said third lens group. 7. A high-performance wide-angle lens according to claim 1, wherein focusing from an object point at infinity to an object point at a short distance is performed by increasing a distance between said second lens group and said third lens group. lens. When 8. infinite object point and the focal length of the entire system during focusing f, and the focal length of the fourth lens group and the f _4, claim satisfies the following condition (2) 1,2,6 Or 7 high-performance wide-angle lens. (2) 0.5 <| f ₄ /f|<2.5 9. The focal length of the entire system when focusing on an object point at infinity is f,
When the composite focal length of the first lens group and the second lens group is f ₁₂ and the composite focal length of the third lens group and the fourth lens group is f ₃₄ , the following conditions (3) and (4) 9. The high-performance wide-angle lens according to claim 1, 2, 3, or 6, which satisfies (1). _{(3) 0.01 <| f 34} / f 12 | <0.25 (4) 0.01 <| f / f 12 | <0.3 10. The high-performance lens according to claim 1, wherein the following condition (1 ′) is satisfied when the radius of curvature of the fourth lens group on the object side is R _4a and the radius of curvature on the image plane side is R _4b. Wide-angle lens. (1 ′) 0.2 <(R _4a + R _4b ) / (R _4a −R _4b ) <1.0 When 11. The focal length of the entire system at an infinite object point focusing f, and the focal length of the fourth lens group and the f _4,
8. The method according to claim 1, wherein the following condition (2 ') is satisfied.
High-performance wide-angle lens. (2 ′) 0.8 <| f ₄ /f|<2.0 12. The focal length of the entire system when focusing on an object point at infinity is f, the combined focal length of said first lens group and said second lens group is f _{12 ,} said third lens group and said fourth lens. when the composite focal length of the group was f _34, the following condition (3 '),
The high-performance wide-angle lens according to claim 1, 2, 6, or 7, which satisfies (4 '). (3 ′) 0.04 <| f ₃₄ / f ₁₂ | <0.15 (4 ′) 0.05 <| f / f ₁₂ | <0.18 13. The focal length of the entire system at the time of focusing on an object point at infinity is f, the refractive index and Abbe number of the positive lens of the third lens group are n _P and ν _P , respectively, and the refractive index and Abbe number of the negative lens. Where n _N and v _N , respectively, and the radius of curvature of the joint surface is R, the following conditions (5 ′) and (6 ′) are satisfied.
High-performance wide-angle lens. (5 ') 0.3 <| f · (n P -n N) / R | <1.0 (6') 7 <ν P -ν N <16