JP5316035B2 - Wide angle lens, imaging device, and manufacturing method of wide angle lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide-angle lens which secures back focus and has high imaging performance, an imaging apparatus including the same, and a method for manufacturing the wide-angle lens. <P>SOLUTION: The wide-angle lens includes, in order from an object side, a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power. The first lens group includes, in order from the object side, a positive lens component L11 turning its convex surface to the object side, and a subgroup G1B having negative refractive power. The subgroup of the first lens group has at least two negative meniscus lens components each turning a convex surface to the object side. The second lens group includes, in order from the object side, a first positive lens component, a positive meniscus lens component L23 turning its convex surface to the object side, and a subgroup G2B having positive refractive power. The subgroup of the second lens group includes, in order from the object side, a cemented positive lens including a negative lens L24 and a positive lens L25, and a second positive lens component L26. The wide-angle lens satisfies a predetermined condition. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a wide-angle lens, an imaging device, and a method for manufacturing a wide-angle lens that are optimal for a photographing optical system.

  Conventionally, a thin wide-angle lens used in a camera has been proposed (for example, Patent Document 1).

Japanese Patent Laid-Open No. 3-288109

  However, the conventional thin wide-angle lens has a problem that it is difficult to maintain high imaging performance if further back focus is to be secured.

To solve the above problems, the present invention includes, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a substantially two lens groups becomes the first lens group comprises, in order from the object side, a positive lens component having a convex surface directed toward the object side, a subgroup having a negative refractive power, the subgroup of the first lens group, the object consists two negative meniscus lens component having a convex surface directed toward the side, the second lens group includes, in order from the object side, a first positive lens component, a positive meniscus lens component having a convex surface directed toward the object side, a positive consists of a subgroup having a refractive power, the subgroup of the second lens group includes, in order from the object side, a cemented positive lens of a negative lens and a positive lens made of a second positive lens component, the following conditions A wide-angle lens characterized by satisfaction is provided.
0.90 <Σd / Ymax <2.00
1.30 <BF / f0 <2.50
0.20 <(− f1B) / f0 <1.50

Where Σd is the distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the wide-angle lens, Ymax is the image height when the wide-angle lens has the maximum field angle, and BF is the wide-angle lens. The distance from the apex of the lens surface closest to the image side to the paraxial image surface, f0 is the focal length of the wide-angle lens at the time of focusing on infinity , and f1B is the focal length of the partial group of the first lens group .

  In addition, the present invention provides an imaging apparatus including the wide-angle lens.

Further, according to the present invention, in order from the object side, a wide-angle lens that is substantially composed of two lens groups is formed by a first lens group having negative refractive power and a second lens group having positive refractive power. In the method, only a positive lens component and a partial group having a negative refractive power are arranged in order from the object side in the first lens group, and two negative lenses are arranged in the partial group of the first lens group. only meniscus lens component disposed in the second lens group, in order from the object side, a first positive lens component, a positive meniscus lens component, only the subunit having positive refractive power, the second lens Provided is a method of manufacturing a wide-angle lens in which only a cemented positive lens of a negative lens and a positive lens and a second positive lens component are disposed in order from the object side in the partial group of the group, and the following conditions are satisfied. .
0.90 <Σd / Ymax <2.00
1.30 <BF / f0 <2.50
0.20 <(− f1B) / f0 <1.50

Where Σd is the distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the wide-angle lens, Ymax is the image height when the wide-angle lens has the maximum field angle, and BF is the wide-angle lens. The distance from the apex of the lens surface closest to the image side to the paraxial image surface, f0 is the focal length of the wide-angle lens at the time of focusing on infinity , and f1B is the focal length of the partial group of the first lens group .

  According to the present invention, it is possible to provide a wide-angle lens that secures back focus and has high imaging performance, an imaging apparatus having the same, and a method for manufacturing a wide-angle lens.

It is sectional drawing which shows the lens structure in the infinite point focusing state of the wide angle lens which concerns on 1st Example. FIG. 7 is a diagram illustrating various aberrations of the wide-angle lens according to Example 1 in an infinitely focused state. It is sectional drawing which shows the lens structure in the infinite point focusing state of the wide angle lens which concerns on 2nd Example. FIG. 12 is a diagram illustrating various aberrations of the wide-angle lens according to Example 2 in a focused state at infinity. It is sectional drawing which shows the lens structure in the infinite point focusing state of the wide angle lens which concerns on 3rd Example. FIG. 12 is a diagram illustrating various aberrations of the wide-angle lens according to Example 3 in the infinitely focused state. It is sectional drawing which shows the lens structure in the infinite point focusing state of the wide angle lens which concerns on 4th Example. It is various aberrational figures in the infinity focusing state of the wide angle lens which concerns on 4th Example. It is a figure which shows the structure of the imaging device (camera) provided with the wide angle lens which concerns on 1st Example. It is a figure which shows the manufacturing process of the wide angle lens which concerns on embodiment.

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

The wide-angle lens according to the present embodiment includes, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power, and the first lens group is arranged from the object side. In order, it has a positive lens component having a convex surface facing the object side and a partial group having negative refractive power, and the partial group of the first lens group has at least two negative meniscus lens components having a convex surface facing the object side. The second lens group includes, in order from the object side, a first positive lens component, a positive meniscus lens component having a convex surface facing the object side, and a partial group having a positive refractive power. The partial group of the lens group includes, in order from the object side, a cemented positive lens of a negative lens and a positive lens, and a second positive lens component, and satisfies the following conditional expressions (1) and (2).
(1) 0.90 <Σd / Ymax <2.00
(2) 1.30 <BF / f0 <2.50

  Where Σd is the distance on the optical axis from the lens surface closest to the object side of the wide-angle lens to the lens surface closest to the image (hereinafter referred to as total lens thickness), and Ymax is the image height when the wide-angle lens has the maximum angle of view. (Hereinafter referred to as the maximum image height), BF is the distance from the apex of the lens surface closest to the image side of the wide-angle lens to the paraxial image surface (so-called back focus), and f0 is that of the wide-angle lens at the time of focusing on infinity. Each focal length is shown.

  This wide-angle lens has a positive lens component with a convex surface facing the object side in the first lens group, so that it is possible to satisfactorily correct off-axis aberrations, particularly distortion. Further, by having a partial group having at least two negative meniscus lens components having a convex surface facing the object side behind the positive lens component in the first lens group, it is possible to maintain good distortion and lateral chromatic aberration. Thus, off-axis aberrations, particularly image surface aberrations and astigmatism can be corrected satisfactorily. The lens component refers to a lens made up of a single lens or a cemented lens.

  In addition, since the second lens group has two positive lens components in order from the object side, it is possible to satisfactorily correct downward coma and spherical aberration. In particular, since the second lens group includes a positive meniscus lens component having a convex surface facing the object side, spherical aberration and axial chromatic aberration can be corrected well.

  In addition, when the negative lens is arranged independently in the air, there is a problem that astigmatism is generated on the diverging surface. However, the present wide-angle lens does not arrange the negative lens independently in the air. Since it is arranged as a cemented positive lens of a negative lens and a positive lens in a partial group of the lens group and the partial group has two positive lens components, off-axis aberrations, particularly astigmatism, field aberration, The coma aberration can be corrected satisfactorily. Further, the cemented positive lens can achieve good spherical aberration even when the lens configuration is thin, and can optimize the Petzval sum.

  With the above configuration, the wide-angle lens can achieve a so-called thin wide-angle lens while maintaining a brightness and enabling an extremely thin angle at the same time as increasing the angle of view. As the total lens thickness of the wide-angle lens is reduced, the on-axis and off-axis aberration correction is simultaneously performed on the same lens surface, and the number of constituent lenses is also limited due to the reduction in thickness. I can not take a proper configuration. Accordingly, it is particularly difficult to correct off-axis aberrations, and the optical system tends to have large coma. This wide-angle lens is characterized in that good aberration characteristics are achieved by the optimum lens configuration and refractive power arrangement of each lens group.

  Conditional expression (1) defines an optimum range of the ratio between the total lens thickness and the maximum image height of the wide-angle lens. When the conditional expression (1) shows a small value, it can be said that the lens is a thin wide-angle lens compared to the format size. However, since conditional expression (1) has limitations in securing back focus and correcting aberrations, it is necessary to define an optimum value. By satisfying conditional expression (1), it is possible to achieve a wide-angle lens having a large angle of view and high imaging performance.

  When the upper limit value of conditional expression (1) is exceeded, the maximum image height becomes small in a wide-angle lens having a certain total lens thickness. In that case, the peripheral luminous flux is scattered and the image circle becomes smaller. In addition, when the maximum image height is constant, the entire lens thickness is increased, and the original wide-angle lens cannot be achieved. Also, increasing the thickness of the entire lens leads to an increase in the filter size. In order to reduce the diameter in this state, a refractive power arrangement and a lens arrangement that reduce the incident height of off-axis rays are required, and as a result, field curvature, distortion, and the like deteriorate.

  In addition, size reduction can be achieved by setting the upper limit of conditional expression (1) to 1.85. Further, by making the upper limit value of conditional expression (1) 1.80, further miniaturization can be achieved, and the effect of the present invention can be ensured. Further, by setting the upper limit value of conditional expression (1) to 1.75, it is possible to sufficiently reduce the size and to maximize the effects of the present invention.

  When the lower limit value of conditional expression (1) is not reached, the maximum image height is increased in a wide-angle lens having a certain total lens thickness. In that case, the peripheral imaging performance deteriorates, and in particular, field curvature, astigmatism, and coma become worse. Further, when the maximum image height is constant, the total lens thickness is remarkably reduced. In this case, curvature of field, astigmatism, and coma are particularly deteriorated.

  Various aberrations can be corrected satisfactorily by setting the lower limit of conditional expression (1) to 0.95. Further, various aberrations can be corrected more favorably by setting the lower limit value of conditional expression (1) to 1.00. Further, various aberrations can be corrected more satisfactorily by setting the lower limit value of conditional expression (1) to 1.30. Further, by setting the lower limit of conditional expression (1) to 1.42, various aberrations can be corrected more satisfactorily. Further, by setting the lower limit of conditional expression (1) to 1.49, various aberrations can be corrected more satisfactorily, and the effects of the present invention can be maximized.

  Conditional expression (2) is a condition in which the back focus of the wide-angle lens is defined by the focal length of the wide-angle lens. This is an important measure when this wide-angle lens is used in a single-lens reflex camera. By satisfying conditional expression (2), it is possible to secure a back focus and achieve a wide-angle lens having high imaging performance.

  If the upper limit value of conditional expression (2) is exceeded, it means that the back focus is longer than the focal length of the wide-angle lens. In this case, the refractive power of the first lens unit is remarkably increased with the retrofocus configuration, and as a result, field curvature, astigmatism, and coma are deteriorated.

  Various aberrations can be corrected satisfactorily by setting the upper limit of conditional expression (2) to 2.30. Further, various aberrations can be corrected more favorably by setting the upper limit of conditional expression (2) to 2.00. Further, by setting the upper limit of conditional expression (2) to 1.80, various aberrations can be corrected more satisfactorily, and the effects of the present invention can be maximized.

  If the lower limit of conditional expression (2) is not reached, sufficient back focus cannot be obtained, making it difficult to use this wide-angle lens for a single-lens reflex camera. In addition, since the exit pupil approaches the image plane, it is disadvantageous to use the wide-angle lens for a digital camera. Therefore, if the lower limit value of conditional expression (2) is not reached, it is necessary to move the exit pupil away from the image plane. If it is attempted to move away from the image plane, correction of off-axis aberrations, particularly coma aberration, cannot be performed satisfactorily.

  Various aberrations can be corrected well by setting the lower limit of conditional expression (2) to 1.40. Further, various aberrations can be corrected more favorably by setting the lower limit value of conditional expression (2) to 1.45. Further, by setting the lower limit of conditional expression (2) to 1.50, various aberrations can be corrected more satisfactorily, and the effects of the present invention can be maximized.

In addition, it is desirable that this wide-angle lens satisfies the following conditional expression (3).
(3) 0.20 <(− f1B) / f0 <1.50

    Here, f1B indicates the focal length of the partial group of the first lens group, and f0 indicates the focal length of the wide-angle lens when focusing on infinity.

  Conditional expression (3) is a conditional expression in which the focal length of the partial group of the first lens group is defined by the focal length of the wide-angle lens. The magnitude of the refractive power of the sub-group of the first lens group has an influence on the size of the wide-angle lens and whether the off-axis aberration can be corrected satisfactorily. By satisfying conditional expression (3), a wide-angle lens having high imaging performance can be achieved.

  When exceeding the upper limit value of the conditional expression (3), it means that the absolute value of the focal length of the partial group of the first lens group becomes large, that is, the negative refractive power becomes weak. When the negative refractive power is weakened, the diameter of the first lens group is increased, the diameter of the wide-angle lens is increased, and the back focus is shortened, so that the conditional expressions (1) and (2) are not satisfied. Further, in terms of aberration correction, the refractive power balance between the first lens group having a negative refractive power and the second lens group having a positive refractive power is lost, so that the distortion aberration cannot be corrected satisfactorily.

  The effect of the present invention can be ensured by setting the upper limit value of conditional expression (3) to 1.40. Moreover, the effect of this invention can be made more reliable by making the upper limit of conditional expression (3) 1.10. Moreover, the effect of this invention can be exhibited to the maximum by setting the upper limit of conditional expression (3) to 1.00.

  If the lower limit value of conditional expression (3) is not reached, it means that the absolute value of the focal length of the subgroup of the first lens group becomes small, that is, the subgroup having negative refractive power in the first lens group. It means that the refractive power becomes remarkably strong. In that case, the back focus becomes remarkably long and it becomes difficult to reduce the size of the wide-angle lens, and as a result, the conditional expressions (1) and (2) cannot be satisfied. In terms of aberration correction, a significantly negative refractive power increases off-axis aberrations, and in particular, field curvature, astigmatism, and coma become worse.

  Various aberrations can be corrected well by setting the lower limit of conditional expression (3) to 0.30. Further, various aberrations can be corrected more favorably by setting the lower limit of conditional expression (3) to 0.40. Further, by setting the lower limit of conditional expression (3) to 0.50, various aberrations can be corrected more satisfactorily, and the effects of the present invention can be maximized.

In addition, it is preferable that the wide-angle lens satisfies the following conditional expression (4).
(4) 0.50 <f2B / f0 <2.00

  Here, f2B represents the focal length of the partial group of the second lens group, and f0 represents the focal length of the wide-angle lens when focusing on infinity.

  Conditional expression (4) is a conditional expression that prescribes an optimum value of the focal length of the partial group of the second lens group. By optimizing the refractive power of the second lens group, it is possible to satisfactorily correct spherical aberration and coma.

  If the upper limit value of conditional expression (4) is exceeded, it means that the focal length of the second lens unit subgroup becomes long and the refractive power becomes weak, and the spherical aberration is overcorrected. In this case, coma aberration is deteriorated. Further, in this case, the second lens group is increased in size, which in turn leads to an increase in the size of the wide-angle lens.

  Various aberrations can be favorably corrected by setting the upper limit of conditional expression (4) to 1.80. Further, various aberrations can be corrected more favorably by setting the upper limit value of conditional expression (4) to 1.70. Also, by setting the upper limit of conditional expression (4) to 1.50, various aberrations can be corrected more satisfactorily, and the effects of the present invention can be maximized.

  If the lower limit value of conditional expression (4) is not reached, it means that the focal length of the second lens group subgroup becomes short, that is, the positive refractive power becomes strong, and the spherical aberration is undercorrected. In this case, the back focus is shortened as a result.

  Various aberrations can be corrected satisfactorily by setting the lower limit of conditional expression (4) to 0.60. Further, various aberrations can be corrected more favorably by setting the lower limit value of conditional expression (4) to 0.70. Further, by setting the lower limit of conditional expression (4) to 0.80, various aberrations can be corrected more satisfactorily, and the effects of the present invention can be maximized.

  Further, in this wide-angle lens, the partial group of the second lens group has at least one aspheric surface, and the aspheric surface has a negative refractive power or a negative value as it goes from the optical axis to the periphery. It is desirable that the aspherical surface has a strong refractive power. Such an aspherical surface is suitable for the present wide-angle lens, which is a bright and wide-angle lens with a large angle of view, and with such a configuration, coma, curvature of field, and distortion can be corrected well. . In particular, it is desirable to employ this aspherical surface for the most image-side lens in the second lens group. With this configuration, it is possible to satisfactorily correct coma, curvature of field, and distortion.

In addition, it is desirable that this wide-angle lens satisfies the following conditional expression (5).
(5) R2F <R2R (Unit: mm)

  R2F represents the radius of curvature of the object side lens surface of the positive meniscus lens component in the second lens group, and R2R represents the radius of curvature of the image side lens surface of the positive meniscus lens component in the second lens group.

  Conditional expression (5) is a conditional expression regarding the shape of the positive meniscus lens component of the second lens group. When this conditional expression (5) is satisfied, spherical aberration can be corrected satisfactorily.

  The first positive lens component of the second lens group is preferably a positive lens component having a cemented lens of a negative lens and a positive lens or a cemented lens of a positive lens and a negative lens. With this configuration, it is possible to achieve good lateral chromatic aberration and optimize the Petzval sum.

  In this wide-angle lens, it is desirable that the aperture stop be disposed closer to the object side than the most image side lens of the second lens group. The aperture stop determines the F number of the wide-angle lens. This wide-angle lens can satisfactorily correct field curvature, distortion, and lateral chromatic aberration by disposing the aperture stop closer to the object side than the most image side lens of the second lens group.

In addition, it is desirable that this wide-angle lens satisfies the following conditional expression (6).
(6) νd> 65.0

  Here, νd represents the Abbe number of the negative lens included in at least one sub-group of the first lens group.

  Conditional expression (6) indicates that the partial group of the first lens group has at least one negative lens using a low-dispersion glass material. In particular, it is desirable to use a glass material having an anomalous partial dispersion among low-dispersion glass materials for this negative lens. With this configuration, it is possible to satisfactorily correct the secondary dispersion component of lateral chromatic aberration. In addition, high optical performance can be achieved by disposing at least one negative lens in the partial group of the first lens group.

  Hereinafter, each numerical example of the wide-angle lens according to the present embodiment will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a cross-sectional view illustrating a lens configuration of a wide-angle lens according to a first example.

  The wide-angle lens according to the first example includes, in order from the object side, a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power.

  The first lens group G1 includes, in order from the object side, a positive meniscus lens L11 having a convex surface directed toward the object side, and a partial group G1B having negative refractive power. The subgroup G1B includes, in order from the object side, a negative meniscus lens L12 having a convex surface facing the object side and an aspheric surface on the image side lens surface, and a negative meniscus lens L13 having a convex surface facing the object side. .

  The second lens group G2 determines, in order from the object side, a cemented positive lens formed by cementing a negative meniscus lens L21 having a convex surface toward the object side and a positive meniscus lens L22 having a convex surface toward the object side, and an F number. An aperture stop S, a positive meniscus lens L23 having a convex surface facing the object side, and a subgroup G2B having a positive refractive power are configured. The subgroup G2B includes, in order from the object side, a cemented positive lens formed by cementing a biconcave negative lens L24 and a biconvex positive lens L25, and a biconvex shape in which an aspheric surface is provided on the image side lens surface. And a positive lens L26.

  In addition, a notch is provided at a position having a vertex distance of 4 mm from the object-side lens surface of the negative meniscus lens L21 of the second lens group, and the ray of the lower ray is determined with an effective diameter of 10.4 mmφ.

  Table 1 below shows specification values of the wide-angle lens according to the first example.

  In (surface data) in the table, the surface number is the number of the lens surface counted from the object side, r is the radius of curvature of the lens surface, d is the surface spacing of the lens surface, and nd is the d-line (wavelength λ = 587.6 nm). And νd represents the Abbe number for the d-line (wavelength λ = 587.6 nm).

  The object plane indicates the object plane, (aperture) indicates the aperture stop S, and the image plane indicates the image plane I. Note that “∞” in the radius of curvature r column indicates a plane. If the lens surface is aspherical, the surface number is marked with * and the paraxial radius of curvature is shown in the radius of curvature column.

(Aspherical data) shows the aspherical coefficient when the shape of the aspherical surface shown in (Surface data) is expressed by the following equation.
X (y) = (y ² / r) / [1+ [1-κ (y ² / r ² )] ^1/2 ]
+ A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰
+ A12 × y ¹² + A14 × y ¹⁴ + A16 × y ¹⁶

Here, the height in the direction perpendicular to the optical axis is y, the displacement (sag amount) in the optical axis direction at the height y is X (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, and the cone The coefficient is κ, and the nth-order aspheric coefficient is An. “En” represents “× 10 ⁻ⁿ ”, for example “1.234E-05” represents “1.234 × 10 ⁻⁵ ”.

  In (various data), f is the focal length, FNO is the F number, ω is the half angle of view (unit: °), Y is the image height, TL is the total length of the lens system, and Σd is the lens surface on the most object side of the wide-angle lens. The distance on the optical axis from the lens surface to the lens surface closest to the image, BF, represents the back focus.

  (Conditional expression corresponding value) indicates the corresponding value of each conditional expression.

  In all the following specification values, “mm” is generally used as the focal length f, radius of curvature r, surface interval d and other lengths, etc. unless otherwise specified, but the optical system is proportional. Even if it is enlarged or proportionally reduced, the same optical performance can be obtained, and the present invention is not limited to these. Further, the unit is not limited to “mm”, and other appropriate units may be used. Further, these symbols are the same in the other embodiments described below, and the description thereof is omitted.

(Table 1) 1st Example (surface data)
Surface number rd nd νd
Object ∞ ∞
1) 60.2367 3.7000 1.487490 70.45
2) 1253.2521 0.1000 1.000000
3) 23.0000 1.2000 1.497820 82.56
4) * 9.7255 3.0000 1.000000
5) 17.0653 1.0000 1.497820 82.56
6) 11.2587 3.0000 1.000000
7) 209.7383 6.0000 1.581440 40.75
8) 15.3142 4.0000 1.672700 32.11
9) 999.0000 1.0000 1.000000
10> (Aperture) ∞ 0.7000 1.000000
11) 16.8962 1.6000 1.497820 82.56
12) 26.5870 2.9977 1.000000
13) -17.0825 1.0000 1.717360 29.52
14) 115.0466 3.9000 1.603000 65.47
15) -12.9513 0.1000 1.000000
16) 102.8313 3.0000 1.603000 65.47
17) * -33.5404 37.9998 1.000000
Image plane ∞

(Aspheric data)
4th surface κ = 0.5233
A4 = 7.38600E-05
A6 = 1.87510E-07
A8 = 1.29680E-08
A10 = 5.53830E-11
A12 = -0.98108E-12
A14 = -0.17874E-13
A16 = 0.44513E-15

17th surface κ = 6.3253
A4 = 4.20950E-05
A6 = 7.78040E-08
A8 = 1.36830E-09
A10 = 7.36610E-13
A12 = 0.00
A14 = 0.00
A16 = 0.00

(Various data)
f = 24.698
FNO = 2.9
ω = 41.86 °
Y = 21.6
TL = 74.298
Σd = 36.297
BF = 38.000

(Lens group data)
Group Start surface Focal length
G1 1 -28.546
G2 7 22.093

(Values for conditional expressions)
(1): Σd / Ymax = 1.68
(2): BF / f0 = 1.54
(3): (−f1B) /f0=0.907
(4): f2B / f0 = 1.13
(5): R2F <R2R = 16.90 <26.59
(6): νd = 82.56

  FIG. 2 shows various aberrations when the wide-angle lens according to Example 1 is focused at infinity.

  In each aberration diagram, FNO is an F number, Y is an image height, ω is a half angle of view (unit: degree), d is a d-line (wavelength λ = 587.6 nm), and g is a g-line (wavelength λ = 435. 8 nm). In astigmatism, the solid line indicates the sagittal image plane, and the dotted line indicates the meridional image plane. The solid line in coma indicates meridional coma. In the aberration diagrams of other examples shown below, the same reference numerals as those in this example are used and the description thereof is omitted.

  From the various aberration diagrams, it can be seen that the wide-angle lens according to Example 1 has excellent imaging performance with various aberrations corrected satisfactorily.

(Second embodiment)
FIG. 3 is a cross-sectional view illustrating the lens configuration of the wide-angle lens according to the second example.

  The wide-angle lens according to Example 2 includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power.

  The first lens group G1 includes, in order from the object side, a positive meniscus lens L11 having a convex surface directed toward the object side, and a partial group G1B having negative refractive power. The subgroup G1B includes, in order from the object side, a negative meniscus lens L12 having a convex surface facing the object side and a negative meniscus lens L13 having a convex surface facing the object side.

  The second lens group G2 determines, in order from the object side, a cemented positive lens formed by cementing a negative meniscus lens L21 having a convex surface toward the object side and a positive meniscus lens L22 having a convex surface toward the object side, and an F number. An aperture stop S, a positive meniscus lens L23 having a convex surface facing the object side, and a subgroup G2B having a positive refractive power are configured. The subgroup G2B includes a cemented positive lens formed by cementing a biconcave negative lens L24 and a biconvex positive lens L25, and a biconvex positive lens L26 provided with an aspheric surface on the image side lens surface. Composed.

  Note that a notch is provided at a position with a vertex distance of 5 mm from the object-side lens surface of the negative meniscus lens L21 of the second lens group G2, and the ray of the lower ray is determined with an effective diameter of 10.62 mmφ.

Table 2 below shows specification values of the wide-angle lens according to the second example.
(Table 2) 2nd Example (surface data)
Surface number rd nd νd
Object ∞ ∞
1) 45.0041 3.6000 1.603000 65.47
2) 182.0811 0.1000 1.000000
3) 23.0000 1.2000 1.755000 52.29
4) 12.0000 1.8000 1.000000
5) 14.4678 1.0000 1.497820 82.56
6) 8.5548 4.0000 1.000000
7) 75.6692 6.0000 1.581440 40.75
8) 11.1099 4.0000 1.672700 32.11
9) 999.0000 1.0000 1.000000
10) (Aperture) ∞ 0.7000 1.000000
11) 19.2664 1.5000 1.487490 70.45
12) 21.1548 2.9977 1.000000
13) -22.5900 1.0000 1.755200 27.51
14) 61.9542 3.7000 1.593190 67.87
15) -13.0368 0.1000 1.000000
16) 108.4396 3.0000 1.603000 65.47
17) * -32.4109 37.9999 1.000000
Image plane ∞

(Aspheric data)
Surface 17 κ = 2.4373
A4 = 1.83600E-05
A6 = -4.18830E-08
A8 = 1.37730E-09
A10 = -5.38610E-12
A12 = 0.000
A14 = 0.000
A16 = 0.000

(Various data)
f = 24.70
FNO = 2.88
ω = 41.75 °
Y = 21.6
TL = 73.698
Σd = 35.698
BF = 37.998

(Lens group data)
Group Start surface Focal length
G1 1 -25.237
G2 7 21.541

(Values for conditional expressions)
(1): Σd / Ymax = 1.65
(2): BF / f0 = 1.54
(3): (−f1B) /f0=0.766
(4): f2B / f0 = 1.01
(5): R2F <R2R = 19.27 <21.20
(6): νd = 82.56

  FIG. 4 shows various aberrations when the wide-angle lens according to Example 2 is in focus at infinity. From the various aberration diagrams, it can be seen that the wide-angle lens according to the second example has excellent imaging performance with various aberrations corrected satisfactorily.

(Third embodiment)
FIG. 5 is a cross-sectional view showing a lens configuration of a wide-angle lens according to the third example.

  The wide-angle lens according to the third example includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power.

   The first lens group G1 includes, in order from the object side, a positive meniscus lens L11 having a convex surface directed toward the object side, and a partial group G1B having negative refractive power. The subgroup G1B includes, in order from the object side, a negative meniscus lens L12 having a convex surface facing the object side and an aspheric surface on the image side lens surface, and a negative meniscus lens L13 having a convex surface facing the object side. .

  The second lens group G2 determines, in order from the object side, a cemented positive lens formed by cementing a negative meniscus lens L21 having a convex surface toward the object side and a positive meniscus lens L22 having a convex surface toward the object side, and an F number. An aperture stop S, a positive meniscus lens L23 having a convex surface facing the object side, and a subgroup G2B having a positive refractive power are configured. The subgroup G2B includes, in order from the object side, a cemented positive lens formed by joining a biconcave negative lens L24 and a positive lens L25 having a convex surface facing the image side, and an aspherical surface provided on the image side lens surface. It consists of a convex positive lens L26.

  In addition, a notch is provided at a position having a vertex distance of 4 mm from the object-side lens surface of the negative meniscus lens L21 of the second lens group, and the ray of the lower ray is determined with an effective diameter of 10.4 mmφ.

Table 3 below shows specifications of the wide-angle lens according to the third example.
(Table 3) Third Example (surface data)
Surface number rd nd νd
Object ∞ ∞
1) 47.9219 4.0000 1.603000 65.47
2) 286.0566 0.1000 1.000000
3) 23.0000 1.2000 1.497820 82.56
4) * 9.7255 3.0000 1.000000
5) 17.7866 1.0000 1.755000 52.29
6) 11.7936 3.0000 1.000000
7) 192.4496 6.0000 1.581440 40.75
8) 14.3503 4.0000 1.672700 32.11
9) 999.0000 1.0000 1.000000
10> (Aperture) ∞ 0.7000 1.000000
11) 15.7831 1.6000 1.497820 82.56
12) 24.1251 2.9977 1.000000
13) -16.9402 1.0000 1.717360 29.52
14) 98.2188 3.9000 1.603000 65.47
15) -13.0197 0.1000 1.000000
16) 87.7345 3.0000 1.603000 65.47
17) * -32.6504 37.9999 1.000000
Image plane ∞

(Aspheric data)
4th surface κ = 0.5514
A4 = 8.71930E-05
A6 = 1.45310E-07
A8 = 1.44120E-08
A10 = 3.11220E-11
A12 = -0.47684E-12
A14 = -0.49445E-14
A16 = 0.32880E-15

Surface 17 κ = 5.7591
A4 = 3.99600E-05
A6 = 1.66930E-07
A8 = 3.04000E-10
A10 = 6.06570E-12
A12 = 0.000
A14 = 0.000
A16 = 0.000

(Various data)
f = 24.70
FNO = 2.88
ω = 41.26 °
Y = 21.6
TL = 74.598
Σd = 36.598
BF = 38.000

(Lens group data)
Group Start surface Focal length
G1 1 -26.856
G2 7 21.575

(Values for conditional expressions)

(1): Σd / Ymax = 1.69
(2): BF / f0 = 1.54
(3): (−f1B) /f0=0.792
(4): f2B / f0 = 1.10
(5): R2F <R2R = 15.78 <24.13
(6): νd = 82.56

  FIG. 6 shows various aberrations of the wide-angle lens according to Example 3 when focusing on infinity. From the various aberration diagrams, it can be seen that the wide-angle lens according to the third example has excellent imaging performance with various aberrations corrected satisfactorily.

(Fourth embodiment)
FIG. 7 is a cross-sectional view showing a lens configuration of a wide-angle lens according to the fourth example.

  The wide-angle lens according to the fourth example includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power.

  The first lens group G1 includes, in order from the object side, a positive meniscus lens L11 having a convex surface directed toward the object side, and a partial group G1B having negative refractive power. The subgroup G1B includes, in order from the object side, a negative meniscus lens L12 having a convex surface facing the object side and an aspheric surface on the image side lens surface, and a negative meniscus lens L13 having a convex surface facing the object side. .

  The second lens group G2 includes, in order from the object side, a cemented positive lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22, an aperture stop S that determines an F number, and an object side. It is composed of a positive meniscus lens L23 having a convex surface and a subgroup G2B having a positive refractive power. The subgroup G2B includes, in order from the object side, a cemented positive lens formed by cementing a biconcave negative lens L24 and a biconvex positive lens L25, and a positive lens L26 provided with an aspheric surface on the image side lens surface. It is composed of

Table 4 below shows specification values of the wide-angle lens according to the fourth example.
(Surface data)
Surface number rd nd νd
Object ∞ ∞
1) 31.3830 4.0000 1.487490 70.45
2) 150.8827 0.1000 1.000000
3) 23.0000 1.2000 1.497820 82.56
4) * 9.7255 2.0000 1.000000
5) 15.3269 1.0000 1.497820 82.56
6) 7.9129 3.0000 1.000000
7) 108.8032 5.0000 1.672700 32.11
8) -16.9652 1.0000 1.581440 40.75
9) 111.3590 1.5000 1.000000
10> (Aperture) ∞ 0.7000 1.000000
11) 21.5578 1.8000 1.497820 82.56
12) 48.0513 2.9977 1.000000
13) -26.4152 1.0000 1.717360 29.52
14) 75.3003 4.4000 1.497820 82.56
15) -11.0814 0.1000 1.000000
16) 288.1280 3.0000 1.589130 61.18
17) * -32.6421 37.9995 1.000000
Image plane ∞

(Aspheric data)
4th surface κ = 1.0683
A4 = 1.98710E-06
A6 = 1.03460E-07
A8 = -1.40520E-09
A10 = 3.28720E-11
A12 = 0.000
A14 = 0.000
A16 = 0.000

Surface 17 κ = 1.3009
A4 = 2.11830E-05
A6 = 2.27450E-08
A8 = 1.17810E-09
A10 = -3.86520E-12
A12 = 0.000
A14 = 0.000
A16 = 0.000

(Various data)
f = 24.70
FNO = 2.89
ω = 41.80 °
Y = 21.6
TL = 70.797
Σd = 32.798
BF = 38.000

(Lens group data)
Group Start surface Focal length
G1 1 -23.272
G2 7 20.154

(Values for conditional expressions)
(1): Σd / Ymax = 1.52
(2): BF / f0 = 1.54
(3): (-f1B) / f0 = 0.674
(4): f2B / f0 = 0.990
(5): R2F <R2R = 21.56 <48.05
(6): νd = 82.56

  FIG. 8 shows various aberrations when the wide-angle lens according to Example 4 is in focus at infinity. From the various aberration diagrams, it can be seen that the wide-angle lens according to the fourth example has excellent imaging performance with various aberrations corrected satisfactorily.

  According to each of the above embodiments, the inclusion angle exceeds 2ω = 84 °, and has a relatively large aperture of about F2.8 to F3.6, and is small and thin, high performance, spherical aberration, curvature of field, A wide-angle lens in which astigmatism and coma are corrected well can be realized.

  In addition, the following content can be appropriately employed as long as the optical performance of the wide-angle lens of the present application is not impaired.

  The numerical example of the wide-angle lens of the present application is shown as having a two-group configuration, but the present application is not limited to this, and a wide-angle lens of another group configuration (for example, three groups) can be configured. Specifically, a configuration in which a lens or a lens group is added to the most object side or the most image side of the wide-angle lens of the present application may be used. The lens group refers to a portion having at least one lens separated by an air interval.

  The wide-angle lens of the present application uses a part of a lens group, an entire lens group, or a plurality of lens groups as a focusing lens group in order to perform focusing from an object at infinity to a short-distance object. It is good also as a structure moved to. In particular, it is preferable that the whole lens, or at least a part of the second lens group, or at least two parts of the whole lens group be the focusing lens group. Such a focusing lens group can also be applied to autofocus, and is also suitable for driving by an autofocus motor, such as an ultrasonic motor.

  In the wide-angle lens of the present application, either the entire lens group or a part thereof is moved so as to include a component perpendicular to the optical axis as an anti-vibration lens group, or rotationally moved in an in-plane direction including the optical axis The image blur caused by the camera shake can be corrected by swinging). In particular, in the wide-angle lens of the present application, it is preferable that at least a part of the second lens group is a vibration-proof lens group.

  The lens surface of the lens constituting the wide-angle lens of the present application may be a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, it is preferable because lens processing and assembly adjustment are easy, and deterioration of optical performance due to errors in lens processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is aspherical, any of aspherical surface by grinding, glass mold aspherical surface in which glass is molded into an aspherical shape, or composite aspherical surface in which resin provided on the glass surface is formed in an aspherical shape Good. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In the wide-angle lens of the present application, it is preferable that the aperture stop is disposed in or near the second lens group, but the role may be substituted by a lens frame without providing a member as the aperture stop.

  Further, an antireflection film having a high transmittance in a wide wavelength range may be applied to the lens surface of the lens constituting the wide-angle lens of the present application. Thereby, flare and ghost can be reduced, and high optical performance with high contrast can be achieved.

  In the wide-angle lens of the present application, it is preferable that the first lens group has one positive lens component and two negative lens components. In the first lens group, it is preferable that the lens components are arranged in order of positive and negative from the object side with an air gap interposed therebetween.

  In the wide-angle lens of the present application, it is preferable that the second lens group has three positive lens components.

  In the wide-angle lens of the present application, it is preferable that the second lens group has four positive lens components.

  Next, an image pickup apparatus including the wide-angle lens of the present application will be described with reference to the drawings. FIG. 9 is a diagram illustrating a configuration of an imaging apparatus (camera) including the wide-angle lens according to the first example.

  The camera 1 is a digital single-lens reflex camera provided with the wide-angle lens according to the first embodiment as a photographing lens 2 as shown in FIG.

  In the camera 1, light from an object (subject) (not shown) is collected by the taking lens 2 and imaged on the focusing screen 4 through the quick return mirror 3. The light imaged on the focusing screen 4 is reflected in the pentaprism 5 a plurality of times and guided to the eyepiece lens 6. Thus, the photographer can observe the subject image as an erect image through the eyepiece 6.

  Further, when a release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted to the outside of the optical path, and the light from the subject (not shown) collected by the photographing lens 2 forms a subject image on the image sensor 7. Form. As a result, light from the subject is picked up by the image sensor 7 and recorded as a subject image in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1.

  Here, as described in the first embodiment, the wide-angle lens according to the first embodiment mounted on the camera 1 as the photographing lens 2 has a curvature of field and astigmatism due to its characteristic lens configuration. Realizes a wide-angle lens with little coma. As a result, the camera 1 can realize a thin imaging device capable of wide-angle imaging with less curvature of field, astigmatism, and coma.

  In the above embodiment, the camera 1 is configured by mounting the wide-angle lens according to the first embodiment as the photographing lens 2, but the wide-angle lens according to the embodiment other than the first embodiment is mounted. Needless to say, the same effects as those of the camera 1 can be obtained.

  Hereinafter, the outline of the manufacturing method of the wide-angle lens of this application is demonstrated based on FIG. FIG. 10 is a diagram showing a method for manufacturing the wide-angle lens of the present application.

  The wide-angle lens manufacturing method of the present application is a method for manufacturing a wide-angle lens having a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side. Each step S1 to S5 shown is included.

Step S1:
In step S1, an optical member including a positive lens component and a partial group having negative refractive power is arranged in the first lens group in order from the object side.

Step S2:
In step S2, an optical member including a negative meniscus lens component is disposed as a partial group of the first lens group.

Step S3:
In step S3, an optical member including a first positive lens component, a positive meniscus lens component, and a partial group having a positive refractive power is arranged in the second lens group in order from the object side.

Step S4:
In step S4, as a partial group having a positive refractive power of the second lens group, a cemented positive lens of a negative lens and a positive lens and an optical member including a second positive lens component are arranged in this order from the object side.

Step S5:
In step S5, the optical member including the first lens group and the second lens group is arranged in the cylindrical lens barrel from the object side so that the wide-angle lens satisfies the following conditional expressions (1) and (2). .
(1) 0.90 <Σd / Ymax <2.00
(2) 1.30 <BF / f0 <2.50

  Where Σd is the distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the wide-angle lens, Ymax is the image height when the wide-angle lens has the maximum field angle, and BF is the most image-side of the wide-angle lens. The distance from the apex of the lens surface to the paraxial image plane, f0 indicates the focal length of the wide-angle lens when focusing on infinity.

  According to such a wide-angle lens manufacturing method of the present application, a wide-angle lens having a wide field angle and good optical performance can be manufactured.

  In addition, each said Example has shown one specific example of this invention, and this invention is not limited to these.

G1: first lens group G2: second lens group G1B: partial group G2B of the first lens group: partial group S of the second lens group S: aperture stop I: image plane 1: camera 2: taking lens 3: quick return mirror 4: Focusing plate 5: Penta prism 6: Eyepiece lens 7: Image sensor

Claims (10)

In order from the object side, the first lens group having a negative refractive power and the second lens group having a positive refractive power substantially consist of two lens groups,
The first lens group includes, in order from the object side, a positive lens component having a convex surface facing the object side, and a partial group having negative refractive power ,
The partial group of the first lens group includes two negative meniscus lens components having a convex surface facing the object side ,
The second lens group comprises, in order from the object side, a first positive lens component, a positive meniscus lens component having a convex surface directed toward the object side, a subgroup having a positive refractive power,
Wherein the subgroup of the second lens group includes, in order from the object side, a cemented positive lens of a negative lens and a positive lens made of a second positive lens component, wide-angle lens that satisfies the following conditions.
0.90 <Σd / Ymax <2.00
1.30 <BF / f0 <2.50
0.20 <(− f1B) / f0 <1.50
However,
Σd: Distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the wide-angle lens Ymax: Image height when the wide-angle lens has a maximum field angle BF: The image-most side of the wide-angle lens The distance from the apex of the lens surface to the paraxial image plane f0: the focal length of the wide-angle lens when focusing on infinity
f1B: Focal length of the partial group of the first lens group In order from the object side, the first lens group having a negative refractive power and the second lens group having a positive refractive power substantially consist of two lens groups,
The first lens group includes, in order from the object side, a positive lens component having a convex surface facing the object side, and a partial group having negative refractive power ,
The partial group of the first lens group includes two negative meniscus lens components having a convex surface facing the object side ,
The second lens group comprises, in order from the object side, a first positive lens component, a positive meniscus lens component having a convex surface directed toward the object side, a subgroup having a positive refractive power,
Wherein the subgroup of the second lens group includes, in order from the object side, a cemented positive lens of a negative lens and a positive lens made of a second positive lens component, wide-angle lens that satisfies the following conditions.
0.90 <Σd / Ymax <2.00
1.30 <BF / f0 <2.50
0.50 <f2B / f0 <2.00
However,
Σd: Distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the wide-angle lens Ymax: Image height when the wide-angle lens has a maximum field angle BF: The image-most side of the wide-angle lens The distance from the apex of the lens surface to the paraxial image plane f0: the focal length of the wide-angle lens when focusing on infinity
f2B: Focal length of the partial group of the second lens group The wide-angle lens according to claim 1 , wherein the following condition is satisfied.
0.50 <f2B / f0 <2.00
However,
f2B: Focal length of the partial group of the second lens group f0: Focal length of the wide-angle lens when focusing on infinity The partial group of the second lens group has at least one aspheric surface;
4. The aspherical surface according to claim 1, wherein the aspherical surface is an aspherical surface in which the positive refractive power becomes weaker or the negative refractive power becomes stronger as it goes from the optical axis to the periphery. 5. Wide angle lens. The wide-angle lens according to claim 1, wherein the following condition is satisfied.
R2F <R2R (Unit: mm)
However,
R2F: radius of curvature of the object side lens surface of the positive meniscus lens component in the second lens group R2R: radius of curvature of the image side lens surface of the positive meniscus lens component in the second lens group   The wide-angle lens according to any one of claims 1 to 5, wherein the first positive lens component includes a cemented lens of a negative lens and a positive lens or a cemented lens of a positive lens and a negative lens. .   The wide-angle lens according to claim 1, further comprising an aperture stop closer to the object side than a lens closest to the image side of the second lens group. The wide-angle lens according to any one of claims 1 to 7, wherein the partial group of the first lens group includes at least one negative lens that satisfies the following condition.
νd> 65.0
However,
νd: Abbe number of the negative lens included in at least one of the partial groups of the first lens group   An imaging apparatus comprising the wide-angle lens according to claim 1. In order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power, a method for producing a wide-angle lens substantially consisting of two lens groups ,
The first lens group, in order from the object side, a positive lens component, only the subunit having negative refractive power are arranged,
In the partial group of the first lens group, only two negative meniscus lens components are arranged,
The second lens group, in order from the object side, a first positive lens component, a positive meniscus lens component, only the subunit having positive refractive power,
In the partial group of the second lens group, in order from the object side, a cemented positive lens of a negative lens and a positive lens, and only a second positive lens component are arranged,
A method for producing a wide-angle lens, wherein the following conditions are satisfied.
0.90 <Σd / Ymax <2.00
1.30 <BF / f0 <2.50
0.20 <(− f1B) / f0 <1.50
However,
Σd: Distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the wide-angle lens Ymax: Image height when the wide-angle lens has a maximum field angle BF: The image-most side of the wide-angle lens The distance from the apex of the lens surface to the paraxial image plane f0: the focal length of the wide-angle lens when focusing on infinity
f1B: Focal length of the partial group of the first lens group

Images