JP2015227984A - Zoom lens and image capturing device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which has a compact lens system and offers a wide view angle, high zoom ratio, and superior optical performance over an entire zoom range.SOLUTION: A zoom lens comprises, in order from the object side to the image side, a first lens group L1 having negative refractive power, a second lens group L2 having positive refractive power, and a third lens group L3 having positive refractive power, where a distance between each pair of adjacent lens groups changes while zooming. The first lens group comprises a negative lens G11 and one or more lenses arranged in order from the object side to the image side. A focal length f1 of the first lens group, a focal length f2 of the second lens group, and curvature radii R11, R12 of an object-side lens surface and an image side lens surface of the negative lens G11, respectively, are each set appropriately.

Description

  The present invention relates to a zoom lens, and is particularly suitable as an imaging optical system used in an imaging apparatus such as a surveillance camera, a digital camera, a video camera, and a broadcast camera.

  In recent years, there has been a demand for an imaging optical system used in an imaging apparatus to be a small zoom lens with a simple lens configuration and a wide angle of view and a high zoom ratio. For example, the imaging optical system for a surveillance camera is a miniature dome, so it is compact, and can easily capture a wide area (wide angle of view) with a single surveillance camera, and has a high zoom ratio. It is requested. As a wide-angle zoom lens, in order from the object side to the image side, a negative lead type including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power A three-group zoom lens is known.

  In this three-group zoom lens, the first lens group is composed of a negative lens and a positive lens, the second lens group is composed of three or four lenses, and the third lens group is composed of one positive lens. A three-group zoom lens having a wide angle of view is known (Patent Documents 1 and 2). In digital cameras and video cameras, zoom lens distortion is allowed in order to widen the shooting field, and distortion at this time is corrected by electrical image processing.

Japanese Patent Laying-Open No. 2005-258057 JP 2007-140359 A

  The negative lead type three-group zoom lens described above is relatively easy to achieve a wide angle of view and a high zoom ratio while reducing the size of the entire system. In a negative lead type three-group zoom lens, in order to reduce the size of the entire system and increase the zoom ratio, the lens configuration of each lens group constituting the zoom lens, the refractive power of each lens group (reciprocal of focal length), etc. It is important to set up properly.

  For example, it is important to appropriately set the refractive power of the first lens group and the second lens group, the lens shape of each lens group constituting the first lens group, and the like. If these configurations are inappropriate, it becomes very difficult to obtain a zoom lens having a wide angle of view and a high zoom ratio and high optical performance.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens and an image pickup apparatus having the zoom lens in which the entire lens system is small, has a wide angle of view and a high zoom ratio, and can easily obtain high optical performance in the entire zoom range.

The zoom lens according to the present invention includes, 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 index, and a third lens group having a positive refractive power.
In zoom lenses where the distance between adjacent lens groups changes during zooming,
The first lens group includes, in order from the object side to the image side, a negative lens G11 and one or more lenses.
When the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the radiuses of curvature of the object-side lens surface and the image-side lens surface of the negative lens G11 are R11 and R12, respectively.
−0.9 <f1 / f2 <−0.2
0.10 <(R11 + R12) / (R11-R12) <0.55
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens in which the entire lens system is small, has a wide angle of view, a high zoom ratio, and can easily obtain high optical performance in the entire zoom range.

FIG. 5 is a diagram of a lens cross section and a movement locus at the wide angle end according to the first embodiment. (A), (B), (C) Various aberration diagrams in Example 1 at the wide-angle end, the intermediate zoom position, and the telephoto end FIG. 10 is a diagram of a lens cross section and a movement locus at the wide angle end according to the second embodiment. (A), (B), (C) Various aberration diagrams in Example 2 at the wide-angle end, the intermediate zoom position, and the telephoto end FIG. 12 is a diagram of a lens cross section and a movement locus at the wide angle end according to the third embodiment. (A), (B), (C) Various aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Example 3. FIG. 12 is a diagram of a lens cross section and a movement locus at the wide angle end according to the fourth embodiment. (A), (B), (C) Various aberration diagrams of Example 4 at the wide-angle end, the intermediate zoom position, and the telephoto end FIG. 12 is a diagram of a lens cross section and a movement locus at the wide angle end according to the fifth embodiment. (A), (B), (C) Various aberration diagrams of Example 5 at the wide-angle end, the intermediate zoom position, and the telephoto end FIG. 12 is a diagram of a lens cross section and a movement locus at the wide angle end according to the sixth embodiment. (A), (B), (C) Various aberration diagrams of Example 6 at the wide-angle end, the intermediate zoom position, and the telephoto end Schematic diagram of essential parts when the zoom lens of the present invention is applied to a surveillance camera.

  Hereinafter, a zoom lens of the present invention and an image pickup apparatus having the same will be described with reference to the drawings. The zoom lens according to the present invention includes, 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 index, and a third lens group having a positive refractive power. The distance between adjacent lens units changes during zooming.

  FIG. 1 is a lens cross-sectional view at the wide-angle end (short focal length end) of the zoom lens according to Embodiment 1 of the present invention. 2A, 2B, and 2C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end (long focal length end) of the zoom lens according to the first exemplary embodiment of the present invention. Example 1 is a zoom lens having a zoom ratio of 3.93 and an aperture ratio of 1.84 to 2.99.

  FIG. 3 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention. FIGS. 4A, 4B, and 4C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the second embodiment of the present invention. Example 2 is a zoom lens having a zoom ratio of 5.88 and an aperture ratio of 1.85 to 4.30.

  FIG. 5 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 3 of the present invention. FIGS. 6A, 6B, and 6C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the third exemplary embodiment of the present invention. Example 3 is a zoom lens having a zoom ratio of 6.77 and an aperture ratio of 1.85 to 4.80.

  FIG. 7 is a lens cross-sectional view at the wide-angle end of the zoom lens according to a fourth exemplary embodiment of the present invention. FIGS. 8A, 8B, and 8C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the fourth exemplary embodiment of the present invention. Example 4 is a zoom lens having a zoom ratio of 4.83 and an aperture ratio of 1.85 to 3.80.

  FIG. 9 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 5 of the present invention. FIGS. 10A, 10B, and 10C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the fifth exemplary embodiment of the present invention. Example 5 is a zoom lens having a zoom ratio of 4.23 and an aperture ratio of 1.85 to 3.59.

  FIG. 11 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 6 of the present invention. 12A, 12B, and 12C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 6 of the present invention. Example 6 is a zoom lens having a zoom ratio of 7.69 and an aperture ratio of 1.85 to 5.66. FIG. 13 is a schematic view of a main part of a surveillance camera (imaging device) having a zoom lens according to the present invention.

  The zoom lens of each embodiment is an image pickup optical system used in the image pickup apparatus. In the lens cross-sectional view, the left side is the object side (front) and the right side is the image side (rear). The zoom lens of each embodiment may be used in an optical device such as a projector. In this case, the left side is a screen and the right side is a projected image. In the 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 third lens group having positive refractive power. It is. SP is an F number determining member (hereinafter also referred to as “aperture stop”) that functions as an aperture stop that determines (limits) an open F number (Fno) light beam.

  GB is an optical block corresponding to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, and the like. IP is an image plane, and when used as a photographing optical system of a video camera or a digital still camera, an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is placed.

  The arrows indicate the movement trajectory of each lens unit during zooming from the wide-angle end to the telephoto end. An arrow 3a related to the third lens unit L3 indicates a movement locus during zooming from the wide-angle end to the telephoto end when focusing on an object at infinity. An arrow 3b indicates a movement locus during zooming from the wide-angle end to the telephoto end when focusing on a short-distance object. An arrow 3c related to the third lens unit L3 indicates a moving direction during focusing from an infinitely distant object to a close object.

  Among the aberration diagrams, in the spherical aberration diagram, the solid line indicates the d line and the dotted line indicates the g line. Fno is an F number. In the astigmatism diagram, ΔM is a meridional image plane, and ΔS is a sagittal image plane. Lateral chromatic aberration is represented by the g-line. ω is a half angle of view (degree). In each of the following embodiments, the wide-angle end and the telephoto end are zoom positions when the zoom lens unit is positioned at both ends of the range in which the zoom lens unit can move on the optical axis.

  In each example, in order from the object side to the image side, three groups including a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens unit L3 having a positive refractive power. This is a zoom lens having a configuration. When zooming from the wide-angle end to the telephoto end, each lens unit moves as indicated by an arrow. Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a convex locus toward the image side, the second lens unit monotonously moves toward the object side, and the third lens unit moves toward the object side. Move to the side.

  The zoom type of the zoom lens of each embodiment has a lens configuration suitable for zooming by changing the interval between adjacent lens groups, while being a negative lead type that is advantageous for miniaturization with a small lens group configuration. During zooming from the wide-angle end to the telephoto end, the second lens unit L2 (variable magnification lens unit) is moved to change the magnification. Then, the first lens unit L1 and the third lens unit L3 correct the image plane variation accompanying zooming.

  During focusing, the third lens unit L3 moves. This is performed by the third lens unit L3 that easily reduces the lens diameter, thereby reducing the configuration of the lens barrel for focus driving, and is suitable for downsizing the imaging apparatus.

  Although the zoom lens of the present invention has a simple lens configuration, it has a wide angle of view and a zoom ratio of about 4-7. In order to realize a high magnification of the zoom lens, for example, in order from the object side to the image side, a positive lead having a four-group configuration including a first lens group to a fourth lens group having positive, negative, positive, and positive refractive powers is used. A zoom lens is advantageous. However, since the number of lenses in a four-group zoom lens increases, the entire optical system becomes large. In order to achieve a simple lens configuration with a small number of lenses and a wide angle of view, the zoom lens having the negative lead three-group configuration described above is more advantageous.

  Further, the third lens group has a positive refractive power, and the positive refractive power as a whole is shared with the second lens group, so that the spherical aberration and the coma are corrected well. On the other hand, if the third lens group has a negative refractive power, the light beam diameter spreads in the second lens group, so that spherical aberration increases and optical performance deteriorates. In order to correct the spherical aberration at this time, it is necessary to increase the number of lenses, and the entire system becomes larger. Therefore, in the present invention, the third lens unit has a positive refractive power in order to achieve a simple lens configuration with a small number of lenses.

  On the other hand, if an attempt is made to achieve a wide angle of view while reducing the size of the entire system, the effective diameter of the front lens increases, and the curvature of field increases at the wide angle end. Therefore, in the present invention, the negative lens G11 is disposed on the most object side in the first lens unit L1, and the lens shape of the negative lens G11 is appropriately set. Specifically, the lens surface on the object side of the negative lens G11 has a concave shape with a strong curvature, and the front lens effective diameter is obtained by bending the peripheral luminous flux largely with this concave lens surface and allowing barrel distortion. Is aiming for downsizing and wide angle of view.

  Further, when the zoom ratio is increased, a large amount of spherical aberration occurs at the telephoto end. Therefore, the generation of spherical aberration is reduced by the second lens unit L2 near the aperture stop SP where the axial light beam spreads. Specifically, the curvature of each lens surface is relaxed by relatively weakening the positive refractive power of the second lens unit L2, and the occurrence of spherical aberration and the like is suppressed on each lens surface.

The zoom lens according to the present invention is configured as follows in order to obtain a good optical performance with a wide angle of view and a zoom ratio of about 4 to 7 with a simple lens configuration. The first lens unit L1 includes, in order from the object side to the image side, a negative lens G11 and one or more lenses. The focal length of the first lens unit L1 is f1, the focal length of the second lens unit L2 is f2, and the curvature radii of the object side lens surface and the image side lens surface of the negative lens G11 are R11 and R12, respectively. At this time,
−0.9 <f1 / f2 <−0.2 (1)
0.10 <(R11 + R12) / (R11−R12) <0.55 (2)
The following conditional expression is satisfied.

  In the zoom lens of the present invention, the refractive power of the lens unit before and after the aperture stop SP where the beam diameter is widened and the lens shape of the negative lens G11 in the first lens unit L1 are appropriately set.

  Conditional expression (1) relates to the refractive powers of the first lens unit L1 and the second lens unit L2. Conditional expression (1) is for satisfactorily correcting curvature of field at the wide-angle end and spherical aberration at the telephoto end while shortening the total lens length. If the lower limit of conditional expression (1) is not reached, the negative refractive power of the first lens unit L1 becomes weak (the absolute value of the negative refractive power becomes small), and the positive refractive power of the second lens unit L2 becomes strong. For this reason, the Petzval sum increases in the positive direction, and when the angle of view is widened, the curvature of field increases at the wide angle end, which makes it difficult to correct this.

  When the zoom ratio is increased, spherical aberration increases at the telephoto end, and it is difficult to correct this with the second lens unit L2. On the other hand, if the upper limit value of conditional expression (1) is exceeded, the positive refractive power of the second lens unit L2 will weaken, and the amount of movement during zooming will increase, increasing the size of the entire system.

  Conditional expression (2) relates to the lens shape of the negative lens G11 in the first lens unit L1. Conditional expression (2) is for correcting the variation of spherical aberration due to zooming while reducing the effective diameter of the front lens. If the lower limit of conditional expression (2) is not reached, the curvature of the lens surface on the object side becomes stronger and the distortion increases. Therefore, it is advantageous to reduce the effective diameter of the front lens and increase the angle of view. In this case, the field curvature increases and it is difficult to reduce this.

  On the other hand, if the upper limit of conditional expression (2) is exceeded, the curvature of the lens surface on the object side becomes weak, and it becomes difficult to suppress the variation of spherical aberration due to zooming while achieving a wide angle of view.

More preferably, the numerical ranges of conditional expressions (1) and (2) are set as follows.
−0.88 <f1 / f2 <−0.30 (1a)
0.12 <(R11 + R12) / (R11−R12) <0.53 (2a)
More preferably, the numerical ranges of conditional expressions (1a) and (2a) are set as follows.
−0.85 <f1 / f2 <−0.40 (1b)
0.15 <(R11 + R12) / (R11-R12) <0.50 (2b)
In the present invention, it is more preferable to satisfy one or more of the following conditional expressions.

The radius of curvature of the lens surface on the object side of the lens G12 disposed adjacent to the image side of the negative lens G11 is R21. The refractive power of the object-side lens surface of the negative lens G11 is defined as fR11. The refractive power fR11 of the lens surface is N1n as the refractive index of the material of the negative lens G11, and R11 as the radius of curvature of the lens surface.
fR11 = R11 / (N1n-1)
Defined by

  The distance from the most object side lens surface of the first lens unit L1 to the most image side lens surface of the first lens unit L1 is defined as D1. Let the focal length of the negative lens G11 be f1n. The first lens unit L1 has one or more positive lenses, and the refractive index and Abbe number of the material of one positive lens among the one or more positive lenses constituting the first lens unit L1 are N1p and ν1p, respectively. And

At this time, it is preferable to satisfy one or more of the following conditional expressions.
-20.0 <(R12 + R21) / (R12-R21) <-3.5 (3)
−0.95 <f2 / fR11 <−0.55 (4)
−1.0 <D1 / f1 <−0.4 (5)
0.4 <f1n / f1 <0.7 (6)
N1p> 1.9 (7)
ν1p <19.0 (8)
Next, the technical meaning of each conditional expression described above will be described.

  Conditional expression (3) relates to the shape of the air lens in the first lens unit L1. Conditional expression (3) is for satisfactorily correcting spherical aberration and curvature of field. If the lower limit of conditional expression (3) is not reached, the shape of the air lens in the first lens unit L1 becomes a convex meniscus shape that is strong on the object side, which is advantageous in increasing distortion and widening the angle of view. Become. However, it is difficult to correct curvature of field at the wide-angle end. On the other hand, if the upper limit of conditional expression (3) is exceeded, the shape of the air lens in the first lens unit L1 approaches a convex shape, so it is advantageous to correct field curvature on the wide-angle side, but distortion It becomes difficult to reduce spherical aberration at the aberration and at the telephoto end.

  Conditional expression (4) relates to the refractive power of the second lens unit L2 and the refractive power of the lens surface closest to the object side of the first lens unit L1. Conditional expression (4) is mainly for correcting distortion and spherical aberration well at the telephoto end. If the lower limit of conditional expression (4) is not reached, the negative refractive power of the lens surface closest to the object side of the first lens unit L1 will become stronger, which is advantageous in generating distortion and widening the field of view. The curvature of field increases at the wide-angle end, and it is difficult to correct this.

  On the other hand, if the upper limit value of conditional expression (4) is exceeded, the negative refractive power of the lens surface closest to the object side of the first lens unit L1 is weakened, and more spherical aberration occurs at the telephoto end than the first lens unit L1, It becomes difficult to correct this.

  Conditional expression (5) relates to the refractive power of the first lens unit L1 and the lens thickness of the first lens unit L1. Conditional expression (5) is mainly for reducing the total lens length and the effective diameter of the front lens. Below conditional expression (5), the negative refracting power of the first lens unit L1 increases, and the curvature of field increases at the wide-angle end, making it difficult to correct this. On the other hand, if the upper limit value of conditional expression (5) is exceeded, the lens thickness of the first lens unit L1 becomes thin, which is advantageous for downsizing, but the negative lens closest to the object side of the first lens unit L1 The interval between subsequent lenses is narrowed, and it becomes difficult to reduce the variation in lateral chromatic aberration during zooming.

  Conditional expression (6) relates to the refractive power of the negative lens G11 in the first lens unit L1. Conditional expression (6) is mainly for correcting the lateral chromatic aberration satisfactorily while increasing the photographing field angle at the wide-angle end. If the upper limit of conditional expression (6) is exceeded, the negative refractive power of the negative lens G11 in the first lens unit L1 will be weakened, distortion will be less likely to occur, and it will be difficult to increase the angle of view. On the other hand, if the lower limit value of conditional expression (6) is not reached, the negative refractive power of the negative lens G11 in the first lens unit L1 becomes stronger, which is advantageous for widening the field angle of view. It becomes difficult to reduce.

  Conditional expression (7) relates to the material of the positive lens G12 of the first lens unit L1. Conditional expression (7) is mainly for favorably correcting curvature of field on the wide angle side. Below the lower limit value of conditional expression (7), the Patzval sum increases in the positive direction, making it difficult to correct curvature of field. Conditional expression (8) relates to the material of the positive lens G12 of the first lens unit L1. Conditional expression (8) is mainly for correcting chromatic aberration well in the entire zoom range from the wide-angle end to the telephoto end. If the upper limit of conditional expression (8) is exceeded, it will be difficult to correct lateral chromatic aberration at the wide-angle end and axial chromatic aberration at the telephoto end.

In order to correct aberrations, it is more preferable to set the numerical ranges of conditional expressions (3) to (8) as follows.
-18.0 <(R12 + R21) / (R12-R21) <-3.7 (3a)
−0.93 <f2 / fR11 <−0.57 (4a)
−0.95 <D1 / f1 <−0.42 (5a)
0.42 <f1n / f1 <0.70 (6a)
1.9 <N1p <2.4 (7a)
10.0 <ν1p <19.0 (8a)

More preferably, the numerical ranges of the conditional expressions (3a) to (8a) are set as follows.
-15.0 <(R12 + R21) / (R12-R21) <-4.0 (3b)
−0.90 <f2 / fR11 <−0.59 (4b)
−0.90 <D1 / f1 <−0.45 (5b)
0.45 <f1n / f1 <0.68 (6b)
1.93 <N1p <2.30 (7b)
12.0 <ν1p <18.0 (8b)

  In each embodiment, each lens group is configured as described above, thereby obtaining a zoom lens having a good optical performance capable of handling a wide angle of view and a zoom magnification of about 4 to 7 times with a simple lens configuration. ing.

  Next, the lens configuration of each lens group will be described. The first lens unit L1 includes a negative lens G11 having a concave object-side lens surface and a biconcave negative lens G11 and a positive meniscus lens G12 having a convex object-side lens surface. In order to reduce the size of the entire system, the negative refractive power of the first lens unit L1 is increased within an appropriate range. At this time, various aberrations generated from within the first lens unit L1, particularly distortion and field curvature are generated at the wide angle end. At this time, it is configured to allow distortion aberration generated in the first lens unit L1 and correct curvature of field.

  The second lens unit L2 includes a cemented lens obtained by cementing an aspherical positive lens having a convex object-side lens surface and a negative lens having a concave image-side surface, and a biconvex positive lens. The positive refractive power of the second lens unit L2 is increased within an appropriate range. At this time, various aberrations, particularly spherical aberration and coma aberration, occur more in the entire zoom range than in the second lens unit L2. In particular, a lot of field curvature occurs at the wide-angle end.

  Therefore, in each embodiment, a positive lens having a refractive index of the material exceeding 1.8 and having an aspherical lens surface is arranged on the most object side to reduce the occurrence of spherical aberration. Further, the positive refractive power is shared by the cemented lens and one positive lens, thereby reducing the occurrence of these various aberrations. The third lens unit L3 includes one positive lens having a convex shape on the object side. By configuring the third lens unit L3 with a small number of lenses, the third lens unit L3 is made thinner and lighter. In particular, by using a positive lens having a convex lens surface on the object side, fluctuations in field curvature during focusing from an object at infinity to a close object at the telephoto end are reduced.

  When focusing from an object at infinity to a near object, the third lens unit L3 is moved to the object side to effectively use the space between the second lens unit L2 and the third lens unit L3 and shorten the total lens length. Is effectively achieved.

  In the zoom lens of each embodiment, the effective image circle diameter at the wide-angle end is smaller than the effective image circle diameter at the telephoto end. The first lens unit L1 is fixed in the optical axis direction for focusing, but may be moved as necessary for aberration correction. In addition, the whole or a part of the second lens unit L2 may be moved in a direction having a component perpendicular to the optical axis for image blur correction. When used in an imaging apparatus, distortion or chromatic aberration may be corrected by an electric correction means.

  FIG. 13 is a schematic diagram of a main part of a monitoring camera (imaging device) using the zoom lens of the present invention as a photographing optical system. In FIG. 13, reference numeral 30 denotes a main body of the surveillance camera, and reference numeral 31 denotes an imaging optical system constituted by any one of the zoom lenses described in each embodiment.

  Reference numeral 32 denotes a solid-state imaging device such as a CCD sensor or a CMOS sensor that is incorporated in the main body of the surveillance camera and receives a subject image formed by the photographing optical system 31. Reference numeral 33 denotes a memory for recording information corresponding to the subject image photoelectrically converted by the solid-state image sensor 32. Reference numeral 34 denotes a network cable for transferring a subject image photoelectrically converted by the photographed 32. The imaging device is not limited to a monitoring camera, and can be used in a video camera, a digital camera, and the like.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments and optical specifications (view angle and Fno), and various modifications are possible within the scope of the gist.

  Next, numerical examples of the present invention will be shown. In each numerical example, i indicates the order of the surfaces from the object side, and ri is the radius of curvature of the lens surface. di is a lens thickness and an air space between the i-th surface and the (i + 1) -th surface. ndi and νdi denote the refractive index and Abbe number for the d-line, respectively. * Indicates an aspherical surface. The two surfaces closest to the image side are glass materials such as face plates. K, A4, A6, A8, A10, A12, and A14 are aspherical coefficients.

When the aspherical shape is x with the displacement in the optical axis direction at the position of the height h from the optical axis as x based on the surface vertex,
^{x = (h 2 / R)} / [1+ {1- (1 + k) (h / R) 2} 1/2] + A4 · h 4 + A6 · h 6 + A8 · h 8 + A10 · h 10 + A12 · h 12 + A14 · h ¹⁴
It is represented by Where R is the paraxial radius of curvature. “E-X” means “× 10 ^−X ”. An aspherical surface is marked with * on the right side of the surface number in each table. The back focus BF is indicated by the air distance from the lens surface closest to the image side to the image surface. The total lens length is a value obtained by adding back focus to the distance from the first lens surface to the final lens surface. In the numerical examples 1 to 6, the interval d5 is negative because it is counted as the aperture stop SP and the second lens unit L2 in order from the object side to the image side. Table 1 shows the relationship between the above-described conditional expressions and numerical examples.

Numerical example 1
Surface data surface number rd nd νd
1 * -8.954 0.70 1.84954 40.1
2 * 4.739 0.35
3 5.445 2.32 1.95906 17.5
4 11.711 (variable)
5 (Aperture) ∞ -0.45
6 * 5.397 2.23 1.85 135 40.1
7 -9.614 0.50 1.80809 22.8
8 5.058 0.42
9 14.027 1.17 1.91082 35.3
10 -14.717 (variable)
11 13.021 1.10 1.59282 68.6
12 -16.463 (variable)
13 ∞ 0.80 1.51633 64.1
14 ∞ 1.04
Image plane ∞

Aspheric data 1st surface
K = 4.61620e-001 A 4 = 1.12449e-003 A 6 = -7.49953e-005
A 8 = 7.75284e-006 A10 = -3.48847e-007 A12 = 6.07585e-009

Second side
K = -1.03076e + 000 A 4 = 1.59743e-003 A 6 = -4.44740e-005
A 8 = 7.45060e-006 A10 = 3.17011e-007 A12 = -7.02640e-008
A14 = 2.80440e-009

6th page
K = -5.57257e-001 A 4 = -3.52868e-004 A 6 = 2.50836e-005
A 8 = -3.04108e-006

Various data Zoom ratio 3.93
Wide angle Medium telephoto focal length 2.20 5.96 8.66
F number 1.84 2.55 2.99
Half angle of view (degrees) 53.28 15.51 10.60
Total lens length 28.54 24.78 28.73
BF 3.98 7.75 11.51

d 4 13.23 3.28 1.05
d10 2.99 5.41 7.83
d12 2.41 6.18 9.95

Zoom lens group data group Start surface Focal length
1 1 -5.51
2 6 7.65
3 11 12.44

Numerical example 2
Surface data surface number rd nd νd
1 * -8.757 0.70 1.84954 40.1
2 * 4.815 0.43
3 6.185 1.80 1.95906 17.5
4 15.678 (variable)
5 (Aperture) ∞ -0.40
6 * 5.484 1.74 1.85135 40.1
7 -59.643 0.50 1.80518 25.5
8 4.869 0.24
9 * 6.826 1.84 1.55332 71.7
10 * -9.151 (variable)
11 21.704 0.95 1.59282 68.6
12 -31.463 (variable)
13 ∞ 1.63 1.51633 64.1
14 ∞ 1.06
Image plane ∞

Aspheric data 1st surface
K = -4.28985e + 000 A 4 = -4.99112e-004 A 6 = 3.85720e-005
A 8 = 8.69996e-007 A10 = -1.49511e-007 A12 = 3.48399e-009

Second side
K = -1.20634e + 000 A 4 = 6.76672e-004 A 6 = 8.94741e-005
A 8 = -5.76347e-006 A10 = 6.95375e-007 A12 = -4.55193e-008
A14 = 6.55979e-010

6th page
K = -5.57257e-001 A 4 = 4.08081e-005 A 6 = 7.26720e-006
A 8 = -4.95461e-006

9th page
K = -2.02655e + 000 A 4 = 6.78698e-005 A 6 = -1.86794e-004
A 8 = 5.85007e-005

10th page
K = 1.12537e + 000 A 4 = 5.03807e-004 A 6 = -2.56800e-004
A 8 = 4.82593e-005

Various data Zoom ratio 5.88
Wide angle Medium telephoto focal length 2.21 7.76 13.00
F number 1.85 3.09 4.30
Half angle of view (degrees) 54.74 11.75 6.96
Total lens length 30.97 25.52 30.70
BF 4.39 10.97 17.55

d 4 15.80 3.07 0.97
d10 2.98 3.68 4.38
d12 2.25 8.83 15.42

Zoom lens group data group Start surface Focal length
1 1 -5.65
2 6 7.72
3 11 21.81

Numerical example 3
Surface data surface number rd nd νd
1 * -8.728 0.70 1.84954 40.1
2 * 5.089 0.45
3 6.632 1.70 1.95906 17.5
4 17.501 (variable)
5 (Aperture) ∞ -0.40
6 * 5.292 1.80 1.85135 40.1
7 -47.762 0.50 1.80518 25.5
8 4.899 0.30
9 * 7.717 1.75 1.55332 71.7
10 * -9.220 (variable)
11 15.467 0.88 1.59282 68.6
12 928.080 (variable)
13 ∞ 1.63 1.51633 64.1
14 ∞ 1.06
Image plane ∞

Aspheric data 1st surface
K = -5.32288e + 000 A 4 = -7.36530e-004 A 6 = 4.51808e-005
A 8 = 1.31893e-006 A10 = -1.68652e-007 A12 = 3.35382e-009

Second side
K = -1.38898e + 000 A 4 = 7.95130e-004 A 6 = 2.46986e-005
A 8 = 1.80687e-006 A10 = 5.69277e-007 A12 = -7.14369e-008
A14 = 1.81035e-009

6th page
K = -5.57257e-001 A 4 = 3.51412e-005 A 6 = 8.00238e-006
A 8 = -4.07063e-006

9th page
K = -2.75769e + 000 A 4 = 5.91618e-005 A 6 = -1.99352e-004
A 8 = 5.69620e-005

10th page
K = 4.06210e-001 A 4 = 3.39125e-004 A 6 = -2.45525e-004
A 8 = 4.68594e-005

Various data Zoom ratio 6.77
Wide angle Medium Telephoto focal length 2.22 8.61 15.00
F number 1.85 3.20 4.80
Half angle of view (degrees) 54.36 10.56 6.02
Total lens length 31.98 25.85 31.62
BF 4.36 12.16 19.96

d 4 16.96 3.00 0.94
d10 2.97 3.00 3.03
d12 2.23 10.03 17.83

Zoom lens group data group Start surface Focal length
1 1 -5.84
2 6 7.78
3 11 26.52

Numerical example 4
Surface data surface number rd nd νd
1 * -8.887 0.70 1.84954 40.1
2 * 4.034 0.72
3 5.593 1.94 1.95906 17.5
4 12.354 (variable)
5 (Aperture) ∞ -0.40
6 * 5.693 1.60 1.85135 40.1
7 -35.386 0.50 1.80518 25.5
8 4.946 0.27
9 * 8.341 2.13 1.55332 71.7
10 * -6.204 0.00
11 ∞ (variable)
12 30.889 0.99 1.59282 68.6
13 -18.072 (variable)
14 ∞ 1.63 1.51633 64.1
15 ∞ 1.06
Image plane ∞

Aspheric data 1st surface
K = -1.70854e + 001 A 4 = 3.80917e-004 A 6 = -5.20392e-005
A 8 = 2.72892e-006 A10 = -1.06937e-007 A12 = 2.07707e-009

Second side
K = -9.58399e-001 A 4 = 3.59233e-003 A 6 = -6.20851e-005
A 8 = -1.00736e-005 A10 = 7.77853e-007 A12 = -2.86536e-008
A14 = 5.22861e-010

6th page
K = -5.57257e-001 A 4 = -5.11870e-004 A 6 = 8.46847e-006
A 8 = -1.55276e-005

9th page
K = -1.77956e + 000 A 4 = 2.25028e-004 A 6 = -1.56374e-004
A 8 = 9.69657e-005

10th page
K = 3.13695e-001 A 4 = 4.59240e-004 A 6 = -3.00701e-004 A 8 = 6.53404e-005

Various data Zoom ratio 4.83
Wide angle Medium Telephoto focal length 1.93 5.92 9.30
F number 1.85 2.90 3.80
Half angle of view (degrees) 58.95 15.43 9.75
Total lens length 29.99 25.19 29.51
BF 4.20 8.65 13.10

d 4 14.37 3.14 1.03
d11 2.98 4.96 6.94
d13 2.07 6.52 10.96

Zoom lens group data group Start surface Focal length
1 1 -4.93
2 6 7.39
3 12 19.38

Numerical example 5
Surface data surface number rd nd νd
1 * -10.511 0.70 1.84954 40.1
2 * 3.671 0.91
3 5.522 2.06 2.10205 16.8
4 9.845 (variable)
5 (Aperture) ∞ -0.30
6 * 6.758 1.92 1.85135 40.1
7 -37.189 0.50 2.00069 25.5
8 6.255 0.15
9 * 8.379 2.33 1.55332 71.7
10 * -4.745 (variable)
11 12.937 1.10 1.59282 68.6
12 -32.299 (variable)
13 ∞ 1.63 1.51633 64.1
14 ∞ 1.07
Image plane ∞

Aspheric data 1st surface
K = -2.66594e + 001 A 4 = 8.83038e-004 A 6 = -9.11166e-005
A 8 = 4.45881e-006 A10 = -1.23734e-007 A12 = 1.45115e-009

Second side
K = -9.29116e-001 A 4 = 4.37645e-003 A 6 = -1.84321e-004
A 8 = 5.96815e-007 A10 = 8.20085e-007 A12 = -7.99274e-008
A14 = 2.03879e-009

6th page
K = -5.57257e-001 A 4 = -8.35326e-004 A 6 = -6.97410e-005
A 8 = -1.16940e-005

9th page
K = -3.96947e + 000 A 4 = -4.11586e-004 A 6 = 1.17299e-004
A 8 = 3.25287e-005

10th page
K = 4.45473e-001 A 4 = 1.93458e-004 A 6 = -3.06263e-005
A 8 = 1.33219e-005

Various data Zoom ratio 4.23
Wide angle Medium Telephoto focal length 1.73 4.89 7.30
F number 1.85 2.87 3.59
Half angle of view (degrees) 62.49 18.78 12.51
Total lens length 30.17 26.04 30.30
BF 4.13 6.43 8.73

d 4 13.83 3.38 1.33
d10 2.84 6.85 10.87
d12 1.99 4.29 6.59

Zoom lens group data group Start surface Focal length
1 1 -4.77
2 6 7.46
3 11 15.72

Numerical example 6
Surface data surface number rd nd νd
1 * -8.469 0.70 1.84954 40.1
2 * 5.553 0.65
3 7.516 1.57 1.95906 17.5
4 22.138 (variable)
5 (Aperture) ∞ -0.40
6 * 5.247 1.93 1.85135 40.1
7 -23.367 0.50 1.80518 25.5
8 5.082 0.21
9 * 7.430 1.67 1.55332 71.7
10 * -9.878 (variable)
11 133.944 0.72 1.59282 68.6
12 -40.845 (variable)
13 ∞ 1.63 1.51633 64.1
14 ∞ 1.07
Image plane ∞

Aspheric data 1st surface
K = -2.60893e + 001 A 4 = -2.94192e-003 A 6 = 2.27797e-004
A 8 = -4.56507e-006 A10 = -2.50399e-007 A12 = 9.57874e-009

Second side
K = 2.17979e-001 A 4 = 1.45040e-003 A 6 = -5.20278e-004
A 8 = 7.79566e-005 A10 = -4.15233e-006 A12 = -3.49059e-008
A14 = 6.20182e-009

6th page
K = -5.57257e-001 A 4 = 2.31056e-004 A 6 = -1.10394e-005
A 8 = -3.32341e-006

9th page
K = -2.00818e + 000 A 4 = -4.32791e-004 A 6 = -1.45538e-004
A 8 = 7.88711e-005

10th page
K = -1.60716e + 000 A 4 = 5.54417e-004 A 6 = -2.89879e-004
A 8 = 8.40787e-005

Various data Zoom ratio 7.69

Focal length 2.21 9.67 17.00
F number 1.85 3.76 5.66
Half angle of view (degrees) 53.00 9.37 5.31
Total lens length 32.95 26.21 32.95
BF 4.31 12.54 20.77

d 4 18.40 2.95 0.96
d10 2.70 3.18 3.67
d12 2.17 10.40 18.63

Zoom lens group data group Start surface Focal length
1 1 -6.21
2 6 7.41
3 11 52.88

L1 First lens group L2 Second lens group L3 Third lens group SP Aperture stop

Claims (9)

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 index, and a third lens group having a positive refractive power,
In zoom lenses where the distance between adjacent lens groups changes during zooming,
The first lens group includes, in order from the object side to the image side, a negative lens G11 and one or more lenses.
When the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the radiuses of curvature of the object-side lens surface and the image-side lens surface of the negative lens G11 are R11 and R12, respectively.
−0.9 <f1 / f2 <−0.2
0.10 <(R11 + R12) / (R11-R12) <0.55
A zoom lens satisfying the following conditional expression: When the radius of curvature of the object-side lens surface of the lens G12 arranged adjacent to the image side of the negative lens G11 is R21,
-20.0 <(R12 + R21) / (R12-R21) <-3.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the refractive power of the object side lens surface of the negative lens G11 is fR11,
−0.95 <f2 / fR11 <−0.55
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the distance from the most object side lens surface of the first lens group to the most image side lens surface of the first lens group is D1,
−1.0 <D1 / f1 <−0.4
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the negative lens G11 is f1n,
0.4 <f1n / f1 <0.7
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The first lens group includes one or more positive lenses, and the refractive index and the Abbe number of one positive lens among the one or more positive lenses constituting the first lens group are N1p and ν1p, respectively. And when
N1p> 1.9
ν1p <19.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   The zoom lens according to claim 1, wherein the first lens group includes one negative lens and one positive lens.   The zoom lens according to any one of claims 1 to 7, wherein an effective image circle diameter on the wide-angle side is smaller than an effective image circle diameter at the telephoto end.   An image pickup apparatus comprising: the zoom lens according to claim 1; and an image pickup element that receives an image formed by the zoom lens.