JP2006039531A - Zoom lens and imaging apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a zoom lens that has a structure suitable for widening the field angle and realizes high optical performance, over the entire zoom range. <P>SOLUTION: Regarding the zoom lens including, in the order starting from an object side to an image side, a 1st lens group L1 having negative refractive power, a 2nd lens group L2 having positive refractive power, a 3rd lens group L3 having negative refractive power, and a 4th lens group L4 having positive refractive power, a back focus and the refractive power of each lens group are set appropriately. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens suitable for a photographing optical system of, for example, a silver salt film camera or a digital still camera.

Conventionally, a so-called negative lead type zoom lens that is preceded by a lens unit having a negative refractive power is known. The negative lead zoom lens
(A) The proximity shooting distance is relatively short,
(B) Wide angle of view is relatively easy.
(C) It is easy to make the back focus relatively long.
Therefore, it is widely used for wide-angle zoom lenses.

For example, in Patent Documents 1 to 19, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a first lens group having a positive refractive power. A zoom lens having four lens groups and performing zooming by moving at least two of these lens groups has been proposed.
JP-A-57-11315 JP 58-95315 A JP 59-229517 A JP 60-55313 A JP-A-60-87312 JP-A-61-62013 JP 61-123811 A JP-A-62-63909 Japanese Patent Laid-Open No. 2-136812 JP-A-4-235515 JP-A-4-163415 Japanese Patent Laid-Open No. 5-19170 JP-A-5-313065 JP-A-6-82698 JP-A-7-287168 Japanese Patent Laid-Open No. 10-82594 Japanese Unexamined Patent Publication No. 2000-33897 JP 2002-287031 A Japanese Patent No. 2629904

  In recent years, zoom lenses for digital single-lens reflex cameras have been required to have a wider angle and higher image quality.

  In general, if the refractive power of each lens group in a zoom lens is increased, the amount of movement of each lens group to obtain a predetermined zoom ratio is reduced, so that a wide angle of view can be achieved while shortening the overall lens length. Become.

  However, simply increasing the refracting power of each lens group increases aberration fluctuations associated with zooming. In particular, when widening the angle of view, it is difficult to obtain good optical performance over the entire zoom range.

  Further, when trying to widen the angle of view, it is difficult to ensure the back focus, it is difficult to correct distortion and astigmatism, and high performance cannot be obtained, or the size tends to increase.

  It is an object of the present invention to provide a zoom lens that has a configuration suitable for widening the angle of view and can realize high optical performance over the entire zoom range.

  An exemplary zoom lens system of the present invention includes, in order from the object side to the image side, a first lens group having negative refractive power (optical power = reciprocal of focal length), and a second lens group having positive refractive power; The third lens group has a negative refractive power and the fourth lens group has a positive refractive power. In the zoom lens, during zooming from the wide-angle end to the telephoto end, the axial distance between the first lens group and the second lens group decreases, the axial distance between the second lens group and the third lens group increases, The axial distance between the lens group and the fourth lens group decreases.

When the back focus at the wide angle end is bfw, the focal length of the entire system at the wide angle end is fw, and the focal lengths of the second lens group and the fourth lens group are f2 and f4, respectively,
2.9 <bfw / fw <5.0
3.1 <f4 / fw <4.5
0.1 <fw / f2 <0.42
Each element is set to satisfy the following conditions.

Further, for example, the second lens group includes, in order from the object side to the image side, a 21st lens group having a negative refractive power and a 22nd lens group having a positive refractive power, and the focal length of the second lens group is f2, When the focal length of the 21st lens group is f2,
2.9 <bfw / fw <5.0
−0.8 <f2 / f2a <−0.05
0.1 <fw / f2 <0.42
Each element is set to satisfy the following conditions.

  According to the present invention, it is possible to realize a zoom lens having a configuration suitable for widening the angle of view and having high optical performance over the entire zoom range.

  Embodiments of a zoom lens system and an imaging apparatus according to the present invention will be described below with reference to the drawings. The zoom lens of this embodiment is suitable for an interchangeable lens of a single-lens reflex camera.

  1, 3, 5, 7, 9, and 11 are lens cross-sectional views at the wide-angle end of the zoom lenses according to Embodiments 1 to 6, respectively. 2, 4, 6, 8, 10, and 12 are aberration diagrams of the zoom lenses of Examples 1 to 6, respectively. (A) is the wide angle end, (b) is the intermediate focal length, and (c) is The state at the telephoto end is shown.

  In each lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In each lens cross-sectional view, L1 is a first lens group having negative refractive power (optical power = reciprocal of focal length), L2 is a second lens group having positive refractive power, and L3 is a first lens group having negative refractive power. The third lens group, L4, is a fourth lens group having a positive refractive power.

  SP is an aperture stop. SSP is a sub-aperture and is a member for regulating the open F number.

  In each aberration diagram, fno represents an F number, and Y represents a maximum image height. d and g represent aberrations at the d-line and g-line, respectively. S. C. Is a sine condition. ΔS represents the state of the sagittal image plane, and ΔM represents the state of the meridional image plane.

  The first lens unit L1 includes, in order from the object side to the image side, a negative lens G11 having a concave surface on the image side and a larger absolute value of the refractive power of the image side surface than the object side surface. The negative lens G12 has a concave shape and has a larger absolute value of the refractive power of the image side surface than the object side surface, and a meniscus positive lens G13 having a convex surface on the object side. . In any of the embodiments, the object-side lens surface of the negative lens G11, that is, the most object-side lens surface in the entire system is an aspherical surface. In Examples 1 and 3 to 6, the image side surface of the negative lens G12 is also an aspherical surface. The aspherical surface of the negative lens G12 is a so-called replica aspherical surface in which an aspherical layer made of resin is formed on the surface of a glass lens.

  The second lens unit L2 includes, in order from the object side to the image side, a second-a lens unit L2a having a negative refractive power and a second-b lens unit L2b having a positive refractive power. The second-a lens unit L2a is constituted by a cemented lens in which a meniscus negative lens G21 having a concave surface on the image side and a biconvex positive lens G22 are cemented. The second b lens unit L2b is composed of a biconvex positive lens G23.

  In Example 1, the third lens unit L3 includes, in order from the object side to the image side, a biconcave negative lens, and a cemented lens obtained by cementing a meniscus negative lens having a concave surface on the image side and a biconvex positive lens. Consists of two lenses. In Example 2, in order from the object side to the image side, a biconcave negative lens, a cemented lens formed by cementing a meniscus negative lens having a concave surface on the image side and a meniscus positive lens having a convex surface on the object side are used. It is configured. In Examples 3 to 6, the lens is composed of two lenses, a biconcave negative lens and a biconvex positive lens in order from the object side to the image side.

  In the first to fourth and sixth embodiments, the fourth lens unit L4 includes, in order from the object side to the image side, a biconvex positive lens, the image side surface having a concave shape, and the image side compared to the object side surface. This is composed of three lenses, a cemented lens in which a negative lens having a large absolute value of the refractive power of the surface and a biconvex positive lens are cemented. In Example 5, a cemented lens obtained by cementing a biconvex positive lens and a biconcave negative lens, a biconvex positive lens, a meniscus negative lens having a concave object side, and a biconvex positive lens It consists of a total of five lenses, which are cemented lenses. In any of the embodiments, the lens surface on the image side of the positive lens disposed closest to the image side, that is, the lens surface closest to the image side in the entire system is an aspherical surface.

  In the zoom lens of each embodiment, during zooming from the wide-angle end to the telephoto end, the axial interval between the first lens unit L1 and the second lens unit L2 is reduced, and the axial range between the second lens unit L2 and the third lens unit L3 is reduced. Both the second to fourth lens units L2 to L3 are moved to the object side so that the interval increases and the axial interval between the third lens unit L3 and the fourth lens unit L4 decreases. In the present embodiment, in order to simplify the mechanism, the second lens unit L2 and the fourth lens unit L4 are configured to move together during zooming. However, it is not necessary to move the second lens unit L2 and the fourth lens unit L4 together as long as some mechanism complexity is allowed. When the second lens unit L2 and the fourth lens unit L4 are configured to be movable along independent trajectories, the degree of freedom is increased in terms of suppressing aberration fluctuations during zooming.

  At the wide-angle end, the first lens unit L1 having negative refractive power is positioned closer to the object side than the telephoto end, and the fourth lens unit L4 having positive refractive power is closer to the image side than the telephoto end. By positioning, the degree of retro focus type is strengthened. Thereby, the form which is easy to ensure the back focus in a wide angle end is taken. At the telephoto end, the second lens unit L2 having a positive refractive power is positioned closer to the object side than the telephoto end, and the third lens unit L3 having a negative refractive power is more imagewise than the telephoto end. By being located to the side, it is closer to the telephoto type. As a result, the total optical length (the distance from the lens surface closest to the object side to the image plane) is shortened.

  In the present embodiment, by adopting such a zoom method, a zoom lens having high optical performance is realized while downsizing.

  As described above, the zoom lens of the present embodiment reduces the on-axis distance between the first lens unit L1 and the second lens unit L2 during zooming from the wide-angle end to the telephoto end, and the second lens unit L2 and the third lens unit L2. The axial distance between the lens groups L3 is increased, and the axial distance between the third lens group L3 and the fourth lens group L4 is decreased. The zoom lens system of the present invention is based on such a refractive power arrangement and a change in distance during zooming.

  At the wide-angle end where the back focus is shortest, it is necessary to arrange the refractive power so that the image-side principal point of the entire system is located as close to the image side as possible in order to ensure the back focus. Therefore, the zoom lens according to the present exemplary embodiment has the second, third, and fourth lens units L2, L3, and L4 having a positive refractive power separated from the first lens unit L1 having a negative refractive power at the wide angle end. It is arranged. That is, as a whole, the refractive power arrangement is such that the rear group of positive refractive power is arranged on the image side of the front group of negative refractive power. With such a refractive power arrangement, the degree of retrofocus type is increased and the back focus at the wide-angle end is secured. In the rear group constituted by the second, third, and fourth lens groups L2, L3, and L4, the third lens group L3 having a negative refractive power is telephoto so that the image-side principal point is positioned as close to the image side as possible. It is arranged closer to the object side than the end. Such a refractive power arrangement of each lens group constituting the rear group also contributes to ensuring the back focus of the entire system.

  At the telephoto end, in order to reduce (shorten) the total lens length of the entire system, it is necessary to arrange the refractive power so that the image-side principal point of the entire system is located as close to the object side as possible. Therefore, the zoom lens according to the present exemplary embodiment forms a front group having a positive refractive power as a whole by bringing the first lens unit L1 having a negative refractive power and the second lens unit L2 having a positive refractive power close to each other at the telephoto end. In addition, a rear group of negative refractive power as a whole is configured close to the third lens group L3 having negative refractive power and the fourth lens group L4 having positive refractive power. With such a refractive power arrangement, the optical length at the telephoto end is shortened by forming a telephoto type.

In addition to the above basic configuration, the zoom lens system according to one aspect of the present invention includes bfw for the back focal length of the entire system at the wide angle end, fw for the focal length of the entire system at the wide angle end, and the second lens unit L2 and the fourth lens. When the focal lengths of the group L4 are f2 and f4, respectively.
2.9 <bfw / fw <5.0 (1)
3.1 <f4 / fw <4.5 (2)
0.1 <fw / f2 <0.42 (3)
Is satisfied.

In the zoom lens system according to another aspect of the present invention, when the focal length of the 2a lens unit L2a is f2a,
2.9 <bfw / fw <5.0 (1)
−0.8 <f2 / f2a <−0.05 (4)
0.1 <fw / f2 <0.42 (3)
Is satisfied.

  Next, the technical meaning of the above conditional expression will be described.

  Conditional expression (1) defines the ratio of the focal length of the entire system to the back focus at the wide-angle end, and is intended to reduce the size.

  If the back focus becomes too long compared to the focal length beyond the lower limit of conditional expression (1), the total optical length at the wide-angle end increases. On the other hand, when the back focus is too short compared to the focal length beyond the upper limit, the rear lens diameter increases.

  Conditional expression (2) is for achieving both high performance and downsizing by appropriately setting the focal length of the fourth lens unit L4.

  If the lower limit value of conditional expression (2) is exceeded, the refractive power of the fourth lens unit L4 becomes too strong (the focal length becomes too short), and it is difficult to correct astigmatism fluctuations especially during zooming. Become. In addition, it becomes difficult to correct distortion aberration and lateral chromatic aberration particularly at the wide-angle end. On the other hand, if the upper limit is exceeded, the effect of extending the back focus due to the configuration of the retrofocus type becomes weak, and it becomes difficult to ensure the back focus at the wide angle end. When the refractive power other than the fourth lens unit L4 is adjusted so that the refractive power arrangement for securing the back focus is achieved in a state where the upper limit value of the conditional expression (2) is exceeded, the refractive power of the first lens unit L1 is increased. It becomes weaker and the front lens diameter tends to increase.

  Furthermore, in order to maintain a balance between high performance and downsizing, it is desirable to set the lower limit of conditional expression (2) to 3.3. Moreover, it is desirable that the upper limit value be 3.9.

  Conditional expression (3) is for achieving both high performance and small size by appropriately setting the focal length of the second lens unit L2.

  If the upper limit of conditional expression (3) is exceeded and the refractive power of the second lens unit L2 becomes too strong, it is difficult to correct spherical aberration, particularly at the telephoto end. When adjustment is made so that spherical aberration generated in the second lens unit L2 is canceled by the fourth lens unit L4 in a state where the upper limit value of the conditional expression (3) is exceeded, the second lens unit L2 is parallel to the fourth lens unit L4. The eccentricity sensitivity becomes too high, making it difficult to manufacture. If the lower limit is exceeded, the effect of shortening the overall length due to the construction of the telephoto type particularly at the telephoto end is weakened, the overall optical length is increased, and the lens diameter of the second lens unit L2 is increased.

  In order to maintain a balance between higher performance and smaller size, it is desirable to set the upper limit of conditional expression (3) to 0.38.

  Conditional expression (4) is mainly for appropriately setting the principal point position of the second lens unit L2 with respect to the ratio of the focal lengths of the second lens unit L2 and the second a lens unit L2a.

  If the lower limit of conditional expression (4) is exceeded and the refractive power of the 2a lens unit L2a becomes too strong, in particular, the central beam incident on the 2b lens L2b becomes large and it becomes difficult to correct spherical aberration. Also, if the refractive power of the second lens unit L2a becomes too weak beyond the upper limit, the image side principal point position of the second lens unit L2 is relatively located on the object side, so that particularly ensuring the back focus at the wide angle end. It becomes difficult.

  Furthermore, it is desirable that the zoom lens system of the present invention satisfies at least one of the following requirements (A) to (G).

(A)
When the focal length of the first lens unit L1 is f1,
−0.9 <fw / f1 <−0.4 (5)
Satisfy the following conditions.

  Conditional expression (5) relates to the ratio between the focal length of the entire system at the wide-angle end and the focal length of the first lens unit L1, and is mainly for achieving a balance between miniaturization and correction of distortion.

  If the lower limit of conditional expression (5) is exceeded and the refractive power of the first lens unit L1 becomes too strong, the negative distortion generated in the first lens unit L1 becomes too large and correction becomes difficult. If the upper limit is exceeded and the refractive power of the first lens unit L1 becomes too weak, the lens diameter of the first lens unit L1 having the largest lens diameter in the entire system increases.

  Furthermore, it is preferable to set the lower limit of conditional expression (5) to -0.75.

(B)
When the focal length of the third lens unit L3 is f3,
−0.3 <fw / f3 <−0.3 (6)
Satisfy the following conditions.

  Conditional expression (6) relates mainly to the ratio between the focal length of the entire system at the wide-angle end and the focal length of the third lens unit L3 in order to maintain a balance between high performance and miniaturization.

  When the lower limit value of conditional expression (6) is exceeded, the refractive power of the third lens unit L3 becomes too strong, and it becomes difficult to satisfactorily correct field curvature in the entire zoom range. Further, when the refractive power of the third lens unit L3 becomes too weak beyond the upper limit, it is possible to set a refractive power arrangement for obtaining a full length shortening effect at the telephoto end while securing the back focus particularly at the wide angle end. It becomes difficult.

  In order to maintain a balance between higher performance and smaller size, it is desirable to set the lower limit of conditional expression (6) to −0.25.

(C)
When the focal length of the entire system at the telephoto end is ft,
1.8 <ft / fw <2.9 (7)
Satisfy the following conditions.

  Conditional expression (7) defines the zoom ratio.

  When the lower limit of conditional expression (7) is exceeded, the zoom ratio becomes too small to obtain the desired zoom ratio. If the lower limit is exceeded, the total length becomes too large.

(D)
When the refractive index of the material constituting the negative lens G11 arranged closest to the object side in the first lens unit L1 is Ng1,
1.55 <Ng1 <1.75 (8)
Satisfy the following conditions.

  Conditional expression (8) defines the refractive index of the material constituting the negative lens G11 in the first lens unit L1, and is intended to balance cost, optical performance, and miniaturization.

  If the lower limit of conditional expression (8) is exceeded and the refractive index of the negative lens G11 is low, the lens diameter increases. Further, the Petzval sum increases negatively, and the field curvature deteriorates. Further, if the refractive index of the negative lens G11 is high beyond the upper limit value, the cost increases.

(E)
When the Abbe number of the material constituting the negative lens G11 disposed closest to the object side in the first lens unit L1 is νg1,
50 <νg1 <70 (9)
Satisfy the following conditions.

  Conditional expression (9) defines the Abbe number of the material constituting the negative lens G11 in the first lens unit L1.

  When the lower limit of conditional expression (9) is exceeded and the Abbe number of the negative lens G11 increases, the lateral chromatic aberration at the wide-angle end becomes too large at a high image height, making correction difficult. If the Abbe number of the negative lens G11 becomes too small beyond the lower limit, the lateral chromatic aberration at the wide-angle end becomes too large at a high image height and becomes difficult to correct.

(F)
When the Abbe number of the material constituting the negative lens G21 in the second lens group L2a is νg4 and the Abbe number of the material constituting the positive lens G22 is νg5,
3 <νg5-νg4 <25 (10)
Satisfy the following conditions.

  Conditional expression (10) is mainly for correcting chromatic aberration with respect to the difference in Abbe number between the negative lens and the positive lens constituting the 2a lens group L2a.

  If the lower limit of conditional expression (10) is exceeded, axial chromatic aberration will increase to the negative side, especially at the telephoto end, making correction difficult. If the upper limit is exceeded, axial chromatic aberration increases to the plus side at the telephoto end, making correction difficult.

(G)
The fourth lens unit L4 includes a positive lens having an aspheric surface whose positive refractive power decreases from the center (optical axis) toward the periphery, and the refractive index and Abbe number of the material constituting the positive lens are set. When N4p and ν4p respectively,
1.4 <N4p <1.55 (11)
69 <ν4p <100 (12)
Satisfy the following conditions.

  If various aberrations are not corrected to some extent as the entire fourth lens unit L4, it is difficult to obtain good optical performance over the entire zoom range. Since the fourth lens unit L4 has a relatively strong positive refractive power, various aberrations can be corrected satisfactorily by providing an aspherical surface in which the positive refractive power decreases from the center toward the periphery. . It is more desirable to satisfy the conditional expression (11) and the conditional expression (12) at the same time.

  Conditional expression (11) defines the refractive index of the aspherical positive lens in the fourth lens unit L4, and is mainly for favorably correcting curvature of field.

  If the lower limit of conditional expression (11) is exceeded and the refractive index of the aspherical positive lens becomes too low, the radius of curvature of the aspherical positive lens becomes too small for a given refractive power. This not only causes processing difficulties, but also increases the lens thickness, which is disadvantageous in ensuring back focus. If the refractive index of the positive lens is too high beyond the upper limit, the Petzval sum increases too negatively and image surface characteristics deteriorate.

  Conditional expression (12) defines the Abbe number of the aspherical positive lens in the fourth lens unit L4 and is mainly for correcting chromatic aberration favorably.

  If the lower limit of conditional expression (12) is exceeded and the Abbe number of the aspherical positive lens becomes too small, it is difficult to correct lateral chromatic aberration, particularly at the wide-angle end. If the upper limit is exceeded and the Abbe number of the aspherical positive lens becomes too large, the color image surface particularly at the wide angle end becomes under and difficult to correct.

  According to the embodiment described above, it is possible to realize a zoom lens having a very wide angle of view and high optical performance over the entire zoom range and having a long back focus compared to the focal length.

  Next, Numerical Examples 1 to 6 corresponding to Numerical Examples 1 to 6 will be shown. In the numerical example, Ri is the radius of curvature of the i-th lens surface (i-th surface) in order from the object side, Di is the axial distance between the i-th surface and the (i + 1) -th surface, and Ni and νi are the i-th surface. The refractive index and the Abbe number (νd) with respect to the d-line of the material constituting the member. Further, f is a focal length, Fno is an F number, and ω is a half angle of view.

  In addition, the aspherical shape has a radius of curvature (paraxial radius of curvature) at the center of the lens surface as R, an optical axis direction as an X axis, and a direction perpendicular to the optical axis as a Y axis, and A, B, C, D, When E and F are respectively aspheric coefficients,

It is represented by

  Table 1 shows the relationship between the above-described conditional expressions of the present invention and numerical examples.

(Numerical example 1)
f = 10.3 to 20.1 Fno = 4.1 to 4.1 2ω = 105.8 to 68.2

* R 1 = 146.274 D 1 = 2.20 N 1 = 1.677900 ν 1 = 55.3
R 2 = 17.828 D 2 = 14.01
R 3 = 1661.193 D 3 = 1.20 N 2 = 1.834807 ν 2 = 42.7
R 4 = 17.632 D 4 = 0.15 N 3 = 1.491710 ν 3 = 57.4
* R 5 = 15.816 D 5 = 1.30
R 6 = 17.928 D 6 = 4.00 N 4 = 1.846660 ν 4 = 23.9
R 7 = 36.306 D 7 = Variable
R 8 = 61.096 D 8 = 1.10 N 5 = 1.834000 ν 5 = 37.2
R 9 = 12.118 D 9 = 5.00 N 6 = 1.526366 ν 6 = 48.5
R10 = -338.384 D10 = 0.09
R11 = 21.035 D11 = 2.80 N 7 = 1.624799 ν 7 = 47.6
R12 = -46.951 D12 = variable
R13 = Aperture D13 = 1.50
R14 = -31.514 D14 = 1.20 N 8 = 1.795274 ν 8 = 44.0
R15 = 65.002 D15 = 0.32
R16 = 94.188 D16 = 1.00 N 9 = 1.594947 ν 9 = 40.7
R17 = 17.520 D17 = 3.00 N10 = 1.764821 ν10 = 26.8
R18 = -1129.575 D18 = variable
R19 = 16.616 D19 = 4.40 N11 = 1.438750 ν11 = 95.0
R20 = -25.027 D20 = 0.09
R21 = -90.406 D21 = 0.75 N12 = 1.834000 ν12 = 37.2
R22 = 13.774 D22 = 5.00 N13 = 1.487490 ν13 = 70.2
* R23 = -25.212

\ Focal length 10.3 15.5 20.1
Variable interval \
D 7 25.35 14.63 9.97
D12 0.56 5.83 8.96
D18 9.33 4.05 0.93

Aspheric coefficient
Side 1: A = 0.00000e + 00 B = 2.02239e-05 C = -4.37934e-08
D = 6.66016e-11 E = -4.35169e-14 F = 9.13878e-18

5th: A = 0.00000e + 00 B = -9.41879e-06 C = -2.53762e-07
D = 6.33799e-10 E = 1.28832e-12 F = -5.07824e-15

23: A = 0.00000e + 00 B = 5.81996e-05 C = 2.75462e-07
D = 1.13007e-09 E = 3.04350e-11 F = -2.12316e-13

(Numerical example 2)
f = 10.3 to 19.8 Fno = 3.5 to 4.6 2ω = 105.8 to 69.0

* R 1 = 855.604 D 1 = 2.20 N 1 = 1.677900 ν 1 = 55.3
R 2 = 18.638 D 2 = 16.19
R 3 = -104.987 D 3 = 1.20 N 2 = 1.834807 ν 2 = 42.7
R 4 = 20.466 D 4 = 1.25
R 5 = 20.302 D 5 = 4.50 N 3 = 1.846660 ν 3 = 23.9
R 6 = 55.840 D 6 = variable
R 7 = 163.166 D 7 = 1.10 N 4 = 1.834000 ν 4 = 37.2
R 8 = 12.506 D 8 = 4.59 N 5 = 1.536535 ν 5 = 46.7
R 9 = -114.891 D 9 = 0.09
R10 = 23.328 D10 = 2.80 N 6 = 1.576559 ν 6 = 46.5
R11 = -37.016 D11 = variable
R12 = Aperture D12 = 1.50
R13 = -30.800 D13 = 1.20 N 7 = 1.767079 ν 7 = 50.2
R14 = 79.785 D14 = 0.16
R15 = 59.680 D15 = 1.00 N 8 = 1.589407 ν 8 = 39.7
R16 = 18.409 D16 = 2.60 N 9 = 1.771912 ν 9 = 29.2
R17 = 467.942 D17 = variable
R18 = 16.276 D18 = 5.40 N10 = 1.438750 ν10 = 95.0
R19 = -29.890 D19 = 0.09
R20 = -174.128 D20 = 0.75 N11 = 1.834000 ν11 = 37.2
R21 = 14.196 D21 = 5.70 N12 = 1.487490 ν12 = 70.2
* R22 = -28.270

\ Focal length 10.3 15.3 19.8
Variable interval \
D 6 22.07 11.66 6.92
D11 1.00 6.92 10.47
D17 11.08 5.16 1.61

Aspheric coefficient
Side 1: A = 0.00000e + 00 B = 2.21103e-05 C = -4.07350e-08
D = 6.98306e-11 E = -6.88215e-14 F = 3.05918e-17

22 side: A = 0.00000e + 00 B = 5.68063e-05 C = 2.92257e-07
D = -1.66003e-10 E = 2.90448e-11 F = -7.13569e-14

(Numerical Example 3)
f = 10.3 to 21.5 Fno = 4.1 to 4.1 2ω = 105.8 to 64.7

* R 1 = -625.482 D 1 = 3.30 N 1 = 1.693501 ν 1 = 53.2
R 2 = 18.763 D 2 = 17.37
R 3 = -170.284 D 3 = 1.20 N 2 = 1.772499 ν 2 = 49.6
R 4 = 22.936 D 4 = 0.17 N 3 = 1.524210 ν 3 = 51.4
* R 5 = 22.530 D 5 = 1.46
R 6 = 24.154 D 6 = 5.00 N 4 = 1.846660 ν 4 = 23.9
R 7 = 82.219 D 7 = Variable
R 8 = Sub-aperture D 8 = 1.23
R 9 = 293.989 D 9 = 1.00 N 5 = 1.834000 ν 5 = 37.2
R10 = 17.616 D10 = 2.85 N 6 = 1.517417 ν 6 = 52.4
R11 = -97.684 D11 = 0.11
R12 = 28.317 D12 = 2.80 N 7 = 1.517417 ν 7 = 52.4
R13 = -37.988 D13 = Variable
R14 = Aperture D14 = 3.55
R15 = -27.331 D15 = 1.44 N 8 = 1.804000 ν 8 = 46.6
R16 = 115.328 D16 = 0.39
R17 = 41.036 D17 = 5.89 N 9 = 1.740769 ν 9 = 27.8
R18 = -171.294 D18 = variable
R19 = 19.792 D19 = 6.16 N10 = 1.438750 ν10 = 95.0
R20 = -64.144 D20 = 0.17
R21 = 71.177 D21 = 1.12 N11 = 1.834000 ν11 = 37.2
R22 = 14.827 D22 = 7.37 N12 = 1.487490 ν12 = 70.2
* R23 = -43.054

\ Focal length 10.3 16.2 21.5
Variable interval \
D 7 26.67 10.44 3.28
D13 0.84 7.18 10.30
D18 12.00 5.66 2.54

Aspheric coefficient
1 side: A = 0.00000e + 00 B = 2.13780e-05 C = -3.63672e-08
D = 4.58245e-11 E = -3.22118e-14 F = 9.98800e-18

5th: A = 0.00000e + 00 B = 1.23725e-05 C = -1.03957e-07
D = -4.46764e-12 E = 5.60360e-13 F = 1.98205e-15

23 side: A = 0.00000e + 00 B = 2.80646e-05 C = 1.45068e-07
D = -3.35514e-10 E = -7.32878e-13 F = 3.46534e-14

(Numerical example 4)
f = 10.3 to 21.4 Fno = 3.5 to 4.6 2ω = 105.8 to 65.1

* R 1 = 12522.667 D 1 = 3.60 N 1 = 1.583126 ν 1 = 59.4
R 2 = 18.218 D 2 = 13.86
R 3 = -91.160 D 3 = 1.20 N 2 = 1.804000 ν 2 = 46.6
R 4 = 18.899 D 4 = 0.16 N 3 = 1.524210 ν 3 = 51.4
* R 5 = 18.224 D 5 = 1.61
R 6 = 21.501 D 6 = 5.20 N 4 = 1.805181 ν 4 = 25.4
R 7 = 88.240 D 7 = Variable
R 8 = 117.682 D 8 = 0.95 N 5 = 1.834807 ν 5 = 42.7
R 9 = 15.679 D 9 = 2.80 N 6 = 1.516330 ν 6 = 64.1
R10 = -74.239 D10 = 0.88
R11 = Aperture D11 = 1.68
R12 = 29.025 D12 = 2.80 N 7 = 1.517417 ν 7 = 52.4
R13 = -38.262 D13 = Variable
R14 = -26.597 D14 = 0.92 N 8 = 1.772499 ν 8 = 49.6
R15 = 53.111 D15 = 0.20
R16 = 32.774 D16 = 5.24 N 9 = 1.728250 ν 9 = 28.5
R17 = -130.858 D17 = variable
R18 = 18.247 D18 = 6.49 N10 = 1.438750 ν10 = 95.0
R19 = -52.394 D19 = 0.15
R20 = 137.851 D20 = 1.00 N11 = 1.834000 ν11 = 37.2
R21 = 13.762 D21 = 7.50 N12 = 1.487490 ν12 = 70.2
* R22 = -30.485

\ Focal length 10.3 16.1 21.4
Variable interval \
D 7 25.13 11.61 5.80
D13 1.38 6.93 10.30
D17 9.60 4.05 0.68

Aspheric coefficient
Side 1: A = 0.00000e + 00 B = 2.33683e-05 C = -4.36269e-08
D = 7.08920e-11 E = -6.68556e-14 F = 2.91205e-17

5th: A = 0.00000e + 00 B = 3.33261e-06 C = -1.22229e-07
D = 7.17771e-11 E = 5.26933e-13 F = -1.48671e-15

22 side: A = 0.00000e + 00 B = 3.27834e-05 C = 1.85266e-07
D = -2.51524e-11 E = -6.39785e-12 F = 9.28438e-14

(Numerical example 5)
f = 10.3 to 21.4 Fno = 3.5 to 4.6 2ω = 105.8 to 65.0

* R 1 = 15000.000 D 1 = 3.50 N 1 = 1.583126 ν 1 = 59.4
R 2 = 18.867 D 2 = 14.03
R 3 = -226.498 D 3 = 1.30 N 2 = 1.772499 ν 2 = 49.6
R 4 = 18.212 D 4 = 0.06 N 3 = 1.524210 ν 3 = 51.4
* R 5 = 16.990 D 5 = 2.72
R 6 = 21.759 D 6 = 5.25 N 4 = 1.728 250 ν 4 = 28.5
R 7 = 74.984 D 7 = Variable
R 8 = 57.846 D 8 = 1.25 N 5 = 1.834807 ν 5 = 42.7
R 9 = 15.171 D 9 = 3.50 N 6 = 1.517417 ν 6 = 52.4
R10 = -331.383 D10 = 1.54
R11 = Aperture D11 = 1.10
R12 = 31.100 D12 = 2.55 N 7 = 1.518229 ν 7 = 58.9
R13 = -31.100 D13 = variable
R14 = -29.031 D14 = 0.80 N 8 = 1.804000 ν 8 = 46.6
R15 = 48.270 D15 = 0.94
R16 = 35.215 D16 = 2.18 N 9 = 1.846660 ν 9 = 23.9
R17 = -1475.794 D17 = variable
R18 = 20.163 D18 = 5.77 N10 = 1.496999 ν10 = 81.5
R19 = -118.970 D19 = 1.00 N11 = 1.834000 ν11 = 37.2
R20 = 34.753 D20 = 0.05
R21 = 35.934 D21 = 4.15 N12 = 1.438750 ν12 = 95.0
R22 = -48.578 D22 = 0.15
R23 = 42.917 D23 = 1.00 N13 = 1.834000 ν13 = 37.2
R24 = 15.239 D24 = 7.51 N14 = 1.484560 ν14 = 70.0
* R25 = -33.295

\ Focal length 10.3 15.0 21.4
Variable interval \
D 7 25.15 12.57 4.73
D13 1.03 5.32 9.62
D17 10.23 5.94 1.64

Aspheric coefficient
Side 1: A = 0.00000e + 00 B = 2.33700e-05 C = -4.61000e-08
D = 7.45700e-11 E = -6.90700e-14 F = 2.82500e-17

5th: A = 0.00000e + 00 B = 3.82416e-06 C = -1.84863e-07
D = 1.59788e-10 E = 1.36095e-12 F = -7.62240e-15

25th: A = 0.00000e + 00 B = 2.79907e-05 C = 9.77159e-08
D = -1.24882e-10 E = 2.46435e-12 F = 1.04886e-14

(Numerical example 6)
f = 10.3 to 24.3 Fno = 3.2 to 4.6 2ω = 105.8 to 58.6

* R 1 = 10448.091 D 1 = 3.40 N 1 = 1.693501 ν 1 = 53.2
R 2 = 18.781 D 2 = 15.15
R 3 = -100.501 D 3 = 1.20 N 2 = 1.772499 ν 2 = 49.6
R 4 = 20.147 D 4 = 0.16 N 3 = 1.524210 ν 3 = 51.4
* R 5 = 19.787 D 5 = 1.41
R 6 = 22.166 D 6 = 5.30 N 4 = 1.805181 ν 4 = 25.4
R 7 = 97.935 D 7 = Variable
R 8 = 124.556 D 8 = 0.95 N 5 = 1.834807 ν 5 = 42.7
R 9 = 17.063 D 9 = 2.62 N 6 = 1.516330 ν 6 = 64.1
R10 = -83.672 D10 = 1.01
R11 = Aperture D11 = 0.80
R12 = 28.856 D12 = 2.90 N 7 = 1.517417 ν 7 = 52.4
R13 = -38.630 D13 = variable
R14 = -26.466 D14 = 1.13 N 8 = 1.772499 ν 8 = 49.6
R15 = 71.048 D15 = 0.20
R16 = 36.519 D16 = 3.09 N 9 = 1.728250 ν 9 = 28.5
R17 = -221.184 D17 = variable
R18 = 18.118 D18 = 6.74 N10 = 1.438750 ν10 = 95.0
R19 = -55.417 D19 = 0.15
R20 = 97.831 D20 = 1.00 N11 = 1.834807 ν11 = 42.7
R21 = 14.055 D21 = 7.20 N12 = 1.487490 ν12 = 96.0
* R22 = -35.924

\ Focal length 10.3 17.6 24.3
Variable interval \
D 7 25.67 9.76 3.81
D13 1.25 7.82 11.19
D17 11.81 5.25 1.88

Aspheric coefficient
1 side: A = 0.00000e + 00 B = 2.34783e-05 C = -4.58852e-08
D = 7.33713e-11 E = -6.89739e-14 F = 2.96011e-17

5th: A = 0.00000e + 00 B = 1.36829e-05 C = -1.55276e-07
D = 2.28744e-10 E = 5.21833e-14 F = 1.89902e-15

22 side: A = 0.00000e + 00 B = 3.53195e-05 C = 1.69354e-07
D = -5.14294e-11 E = 1.65007e-12 F = 4.84168e-14

  Next, an embodiment in which the zoom lens system of the present invention is applied to an imaging apparatus will be described with reference to FIG.

  FIG. 13 is a schematic view of the main part of a single-lens reflex camera. In FIG. 13, reference numeral 10 denotes a photographing lens having the zoom lens 1 according to the first to sixth embodiments. The zoom lens 1 is held by a lens barrel 2 that is a holding member. Reference numeral 20 denotes a camera body, which includes a quick return mirror 3 that reflects the light beam from the photographing lens 10 upward, a focusing plate 4 that is disposed at an image forming position of the photographing lens 10, and an inverted image formed on the focusing plate 4. It is composed of a penta roof prism 5 for converting to an eyepiece, an eyepiece 6 for observing the erect image, and the like. Reference numeral 7 denotes a photosensitive surface, on which a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, or a silver salt film is disposed. At the time of photographing, the quick return mirror 3 is retracted from the optical path, and an image is formed on the photosensitive surface 7 by the photographing lens 10.

  The benefits described in Examples 1 to 6 are effectively enjoyed in the optical apparatus as disclosed in the present embodiment.

2 is a lens cross-sectional view of a zoom lens of Example 1. FIG. FIG. 5 is a diagram illustrating all aberrations of the zoom lens according to Example 1; 6 is a lens cross-sectional view of a zoom lens according to Example 2. FIG. FIG. 5 is a diagram illustrating all aberrations of the zoom lens according to Example 2. 5 is a lens cross-sectional view of a zoom lens according to Example 3. FIG. FIG. 6 is a diagram illustrating all aberrations of the zoom lens according to Example 3; 6 is a lens cross-sectional view of a zoom lens according to Example 4. FIG. FIG. 10 is a diagram illustrating all aberrations of the zoom lens according to Example 4; 10 is a lens cross-sectional view of a zoom lens according to Example 5. FIG. FIG. 10 is a diagram illustrating all aberrations of the zoom lens according to Example 5; 10 is a lens cross-sectional view of a zoom lens according to Example 6. FIG. FIG. 10 is a diagram illustrating all aberrations of the zoom lens according to Example 6; It is a principal part schematic diagram of an imaging device.

Explanation of symbols

L1 1st lens group L2 2nd lens group L2a 2a lens group L2b 2b lens group L3 3rd lens group L4 4th lens group SP Aperture stop

Claims (12)

In order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power are provided. During zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, and the third lens group and the second lens group increase. A zoom lens in which the distance between the four lens groups is reduced;
When the back focus at the wide angle end is bfw, the focal length of the entire system at the wide angle end is fw, and the focal lengths of the second lens group and the fourth lens group are f2 and f4, respectively.
2.9 <bfw / fw <5.0
3.1 <f4 / fw <4.5
0.1 <fw / f2 <0.42
A zoom lens characterized by satisfying the following conditions: In order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power are provided. During zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, and the third lens group and the second lens group increase. A zoom lens in which the distance between the four lens groups is reduced;
The second lens group includes, in order from the object side to the image side, a second a lens group having a negative refractive power and a second b lens group having a positive refractive power,
When the back focus at the wide angle end is bfw, the focal length of the entire system at the wide angle end is fw, the focal length of the second lens group is f2, and the focal length of the second a lens group is f2a.
2.9 <bfw / fw <5.0
−0.8 <f2 / f2a <−0.05
0.1 <fw / f2 <0.42
A zoom lens characterized by satisfying the following conditions: When the focal length of the first lens group is f1,
−0.9 <fw / f1 <−0.4
The zoom lens according to claim 1 or 2, wherein the following condition is satisfied. When the focal length of the third lens group is f3,
−0.3 <fw / f3 <−0.3
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the entire system at the telephoto end is ft,
1.8 <ft / fw <2.9
The zoom lens according to claim 1, wherein the following condition is satisfied. The first lens group has at least one negative lens, and among the negative lenses of the first lens group, when the refractive index of the material forming the negative lens disposed closest to the object side is Ng1,
1.55 <Ng1 <1.75
The zoom lens according to claim 1, wherein the following condition is satisfied. The first lens group has at least one negative lens, and among the negative lenses of the first lens group, when the Abbe number of the material forming the negative lens disposed closest to the object side is νg1,
50 <νg1 <70
The zoom lens according to claim 1, wherein the following condition is satisfied. The fourth lens group includes a positive lens having an aspheric surface whose positive refractive power decreases from the center toward the periphery, and the refractive index and Abbe number of the material forming the positive lens are N4p and ν4p, respectively. and when,
1.4 <N4p <1.55
69 <ν4p <100
The zoom lens according to claim 1, wherein the following condition is satisfied. The second lens group includes, in order from the object side to the image side, a second-a lens group having a negative refractive power and a second-b lens group having a positive refractive power, and the second-a lens group is the second-a lens group. When the Abbe number of the material forming the negative lens is νg4 and the Abbe number of the material forming the positive lens in the second a lens group is νg5,
3 <νg5-νg4 <25
The zoom lens according to claim 1, further comprising a combination of a negative lens and a positive lens satisfying the following condition. In the second a lens group, when the Abbe number of the material forming the negative lens in the second a lens group is νg4 and the Abbe number of the material forming the positive lens in the second a lens group is νg5,
3 <νg5-νg4 <25
The zoom lens according to claim 2, further comprising a combination of a negative lens and a positive lens satisfying the following condition.   The zoom lens according to claim 1, wherein an image is formed on the photoelectric conversion element.   An image pickup apparatus comprising: the zoom lens according to claim 1; and a photoelectric conversion element that receives an image formed by the zoom lens.

Images