Zoom lens and imaging device

Abstract

To provide a small-sized and light-weight zoom lens having high optical performance with a wide angle of view.SOLUTION: The zoom lens consists of, in order from the object side to the image side, a first lens group of a negative refractive power, a second lens group of a positive refractive power, a third lens group of a negative refractive power, and a fourth lens group of a positive refractive power. When zooming, the first lens group and the fourth group do not move while the second lens group and the third group move, so that a distance between adjacent lens groups changes. A third lens group L3 has a negative lens and a positive lens placed closer to the image side than the negative lens. The fourth lens group is formed of one positive meniscus lens convex toward the image side. When a focal distance of the first lens group is f1 and a focal distance of the third lens group is f3, 0.5≤f3 / f1≤2.0 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a zoom lens suitable for an image pickup apparatus. [Background technology]

[0002] Zoom lenses used in imaging devices are required to have high optical performance over the entire zoom range at a wide angle of view, and to be compact. Patent Document 1 discloses a negative-lead wide-angle zoom lens in which a lens group with negative refractive power is arranged on the object side, as a zoom lens that is compact and easy to achieve a wide angle of view. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-059597 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the zoom lens disclosed in Patent Document 1 has insufficient correction of curvature of field at the wide-angle end, and performance at the periphery of the image plane is low.

[0005] The present invention provides a negative-lead type zoom lens that is small, lightweight, has a wide angle of view, and has high optical performance over the entire zoom range. [Means for solving the problem]

[0006] A zoom lens according to one aspect of the present invention is composed of four lens groups. The four lens groups are, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with negative refractive power, and a fourth lens group with positive refractive power. During zooming, the first lens group and the fourth lens group do not move, and the second lens group and the third lens group move, changing the distance between adjacent lens groups. The third lens group L3 has a negative lens and a positive lens arranged closer to the image side than the negative lens. The fourth lens group is composed of one positive meniscus lens that is convex toward the image side. When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 0.5≦f3 / f1≦2.0 The present invention is characterized in that the above conditions are satisfied. An image pickup apparatus including the above zoom lens also constitutes another aspect of the present invention. Effect of the Invention

[0007] According to the present invention, it is possible to provide a negative-lead type zoom lens that is small, lightweight, has a wide angle of view, and has high optical performance over the entire zoom range. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a zoom lens according to a first embodiment at a wide-angle end and a telephoto end in an infinity focused state; [Diagram 2] 4A and 4B are longitudinal aberration diagrams of the zoom lens of Example 1 at the wide-angle end and at the telephoto end when focused on an object at infinity. [Diagram 3] 1 is a cross-sectional view of a zoom lens according to a second embodiment at a wide-angle end and a telephoto end in an infinity focused state; [Figure 4] 11A and 11B are longitudinal aberration diagrams of the zoom lens of Example 2 at the wide-angle end and at the telephoto end when focused on an object at infinity. [Diagram 5] 11 is a cross-sectional view of a zoom lens according to a third embodiment at a wide-angle end and a telephoto end in an infinity focused state; [Figure 6]11A and 11B are longitudinal aberration diagrams of the zoom lens of Example 3 at the wide-angle end and at the telephoto end when focused on an object at infinity. [Figure 7] 11 is a cross-sectional view of a zoom lens according to a fourth embodiment at a wide-angle end and a telephoto end in an infinity focused state; [Figure 8] 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 4 at the wide-angle end and at the telephoto end when focused on an object at infinity. [Figure 9] 13 is a cross-sectional view of a zoom lens according to a fifth embodiment at a wide-angle end and a telephoto end in an infinity focused state; [Figure 10] 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 5 at the wide-angle end and at the telephoto end when focused on an object at infinity. [Figure 11] 1 is a schematic diagram of an image pickup apparatus including a zoom lens according to each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] Prior to the detailed description of Examples 1 to 5, matters common to each of the Examples will be described with reference to FIG.

[0011] In a zoom lens, a lens group is a group of one or more lenses that move together during zooming between the wide-angle end and the telephoto end. That is, the spacing between adjacent lens groups changes during zooming. The lens group may include an aperture stop. The wide-angle end and the telephoto end respectively indicate the zoom states of the maximum angle of view (shortest focal length) and the minimum angle of view (maximum focal length) when the lens group that moves during zooming is located at both ends of the range that it can move mechanically or controllably on the optical axis.

[0012] The zoom lens of each embodiment is composed of four lens groups. The four lens groups are arranged in order from the object side to the image side: a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, and a fourth lens group L4 with positive refractive power. During zooming, the first lens group L1 and the fourth lens group L4 do not move, but the second lens group L2 and the third lens group L3 move, changing the distance between adjacent lens groups.

[0013] The third lens group L3 includes at least a negative lens and a positive lens arranged closer to the image side than the negative lens, and the fourth lens group is composed of one positive meniscus lens G41 having a convex shape facing the image side.

[0014] Furthermore, in the above configuration, when the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 0.5≦f3 / f1≦2.0 (1) The following conditions are satisfied.

[0015] By making the first and fourth lens groups, which tend to be large and have a large mass, immobile (fixed) during zooming, the mechanism for moving the first and fourth lens groups can be made compact, which is advantageous for making the zoom lens more compact and lightweight. Also, by configuring the third lens group with at least a negative lens and a positive lens closer to the image side than the negative lens, it is possible to satisfactorily correct the curvature of field at the wide-angle end, and to achieve high optical performance.

[0016] Furthermore, the fourth lens group is composed of only one positive meniscus lens G41 that is convex toward the image side, which reduces the weight of the fourth lens group while reducing ghosting that occurs near the image plane, achieving high optical performance with high contrast.

[0017] The condition of formula (1) indicates an appropriate range of the ratio of the focal length f1 of the first lens group L1 to the focal length f3 of the third lens group L3. When f3 / f1 exceeds the upper limit of formula (1), the refractive power of the first lens group L1 becomes strong, which is undesirable because it becomes difficult to correct the curvature of field at the wide-angle end side. When f3 / f1 falls below the lower limit of formula (1), the refractive power of the first lens group L1 becomes weak, which is undesirable because it leads to an increase in the size of the zoom lens.

[0018] The zoom lens of each embodiment is configured to satisfy the formula (1), and it is possible to provide a negative-lead type wide-angle zoom lens that is small and lightweight yet has high optical performance over the entire zoom range.

[0019] In the zoom lenses of the respective embodiments, it is preferable that the first lens group is composed of only lenses having refractive power. This allows the first lens group L1 to be made compact. It is preferable that the first lens group L1 includes at least two negative lenses and one positive lens. This allows the aberrations occurring in the first lens group L1 to be corrected well, and is advantageous for making the zoom lens compact. In particular, it is preferable that the first lens group L1 is composed of a negative lens, a negative lens, and a positive lens arranged in this order from the object side to the image side. This allows the first lens group L1 to be made compact while allowing the aberrations occurring in the first lens group L1 to be corrected well.

[0020] In the zoom lens of each embodiment, it is preferable that the second lens group L2 includes an aperture stop. This allows the aperture unit to be made more compact, which is also advantageous for making the zoom lens more compact. Furthermore, it is preferable that the whole or part of the second lens group L2 is an anti-vibration group that moves relative to the optical axis to reduce (correct) image blur caused by camera shake such as hand shake, that is, to perform anti-vibration. This allows high optical performance to be obtained even during anti-vibration.

[0021] In the zoom lens of each embodiment, it is preferable to perform focusing by moving the third lens unit L3, which makes it possible to obtain high optical performance while performing focusing on objects at both close and long distances.

[0022] Furthermore, it is preferable that the zoom lens of each embodiment satisfies at least one of the conditions of the following expressions (2) to (9). The focal length of the second lens group L2 is f2, and the focal length of the fourth lens group L4 is f4. The distance on the optical axis from the image side surface of the lens closest to the image side in the zoom lens to the image plane is BFw, and the distance on the optical axis from the object side surface of the lens closest to the object side in the zoom lens to the image plane is LDw. When the shape factor of the positive meniscus lens constituting the fourth lens group L4 is SF_G41, and the radii of curvature of the object side surface and image side surface of the positive meniscus lens are rG41a and rG41b, respectively, SF_G41=(rG41b+rG41a) / (rG41b-rG41a) In addition, the lateral magnifications of the second lens group L2 at the telephoto end and the wide-angle end in a state focused on an object at infinity (hereinafter referred to as an infinity focused state) are respectively β2t and β2w, and the lateral magnifications of the third lens group L3 at the telephoto end and the wide-angle end in a state focused on infinity are respectively β3t and β3w.

[0023] 0.70≦f2 / (-f1)≦1.40 (2) 1.90≦f4 / (-f1)≦3.50 (3) 0.20≦f2 / (-f3)≦0.90 (4) 0.30≦(-f3) / f4≦0.80 (5) 0.10≦BFw / LDw≦0.30 (6) -3.00≦SF_G41≦-1.01 (7) 1.35≦β2t / β2w≦2.00 (8) 1.05≦β3t / β3w≦1.45 (9) The condition of formula (2) shows an appropriate relationship between the focal lengths f1 and f2 of the first and second lens groups L1 and L2. If the refractive power of the first lens group L1 becomes so strong that f2 / (-f1) exceeds the upper limit of formula (2), it becomes difficult to correct aberrations, which is not preferable. If the refractive power of the first lens group L1 becomes so weak that f2 / (-f1) falls below the lower limit of formula (2), it leads to an increase in the size of the zoom lens, which is not preferable.

[0024] The condition of formula (3) shows an appropriate relationship between the focal lengths f1 and f4 of the first and fourth lens groups L1 and L4. If the refractive power of the first lens group L1 becomes so strong that f4 / (-f1) exceeds the upper limit of formula (3), it becomes difficult to correct aberrations, which is not preferable. If the refractive power of the first lens group L1 becomes so weak that f4 / (-f1) falls below the lower limit of formula (3), it leads to an increase in the size of the zoom lens, which is not preferable.

[0025] The condition of formula (4) shows the appropriate relationship between the focal lengths f2 and f3 of the second and third lens groups L2 and L3. If the refractive power of the second lens group L2 is weak so that f2 / (-f3) exceeds the upper limit of formula (4), the zoom lens becomes large, which is not preferable. If the refractive power of the second lens group L2 is strong so that f2 / (-f3) falls below the lower limit of formula (4), it becomes difficult to correct aberrations, which is not preferable.

[0026] The condition of formula (5) shows an appropriate relationship between the focal lengths f3 and f4 of the third and fourth lens groups L3 and L4. If the refractive power of the third lens group L3 is weakened so that (-f3) / f4 exceeds the upper limit of formula (5), the third lens group L3 will become larger, which is not preferable. If the refractive power of the fourth lens group L4 is weakened so that (-f3) / f4 falls below the lower limit of formula (5), telecentricity cannot be ensured, which is not preferable.

[0027] The condition of formula (6) shows the appropriate relationship between the distance BFw from the image side surface of the lens positioned closest to the image among the zoom lenses at the infinity focus state and the wide-angle end to the image plane, and the distance LDw from the object side surface of the lens positioned closest to the object to the image plane. Note that the distances BFw and LDw are distances when optical members such as parallel plates that do not have refractive power (optical filters, color separation prisms, etc.) are not considered as lenses. If BFw / LDw falls within the numerical range of formula (6), it is possible to miniaturize the zoom lens while ensuring telecentricity.

[0028] The condition of formula (7) indicates an appropriate range of the shape factor SF_G41 of the positive meniscus lens G41. If the meniscus shape is weakened so that SF_G41 exceeds the upper limit of formula (7), the reduction of ghosts occurring near the image plane becomes insufficient, which is undesirable. If the meniscus shape is strengthened so that SF_G41 falls below the lower limit of formula (7), it becomes difficult to correct aberrations, which is undesirable.

[0029] Equation (8) shows the appropriate relationship between the lateral magnifications β2t and β2w of the second lens unit L2 when focused at infinity and at the telephoto and wide-angle ends. If β2t / β2w falls outside the numerical range of equation (8), it becomes difficult to correct aberrations over the entire zoom range, which is not preferable.

[0030] Equation (9) shows the appropriate relationship between the lateral magnifications β3t and β3w of the third lens unit L3 when focused at infinity and at the telephoto and wide-angle ends. If β3t / β3w falls outside the numerical range of equation (9), it becomes difficult to correct aberrations over the entire zoom range, which is not preferable.

[0031] It is more preferable that the numerical ranges of the formulas (1) to (9) are as follows:

[0032] 0.89≦f3 / f1≦1.90 (1a) 0.77≦f2 / (-f1)≦1.15 (2a) 2.14≦f4 / (-f1)≦3.30 (3a) 0.34≦f2 / (-f3)≦0.78 (4a) 0.42≦(-f3) / f4≦0.69 (5a) 0.13≦BFw / LDw≦0.26 (6a) -2.64≦SF_G41≦-1.05 (7a) 1.51≦β2t / β2w≦1.87 (8a) 1.11≦β3t / β3w≦1.33 (9a) Moreover, it is more preferable that the numerical ranges of the formulas (1) to (9) are as follows:

[0033] 1.28≦f3 / f1≦1.80 (1b) 0.84≦f2 / (-f1)≦0.91 (2b) 2.35≦f4 / (-f1)≦3.11 (3b) 0.48≦f2 / (-f3)≦0.66 (4b) 0.53≦(-f3) / f4≦0.59 (5b) 0.15≦BFw / LDw≦0.23 (6b) -2.27≦SF_G41≦-1.09 (7b) 1.65≦β2t / β2w≦1.74 (8b) 1.16≦β3t / β3w≦1.22 (9b) Examples 1 to 5 will be described in detail below. Figs. 1, 3, 5, 7, and 9 show the configurations of the zoom lenses of Examples 1 to 5 in the infinity focused state at the wide-angle end (WIDE) and the telephoto end (TELE), respectively. In each figure, the left side is the object side (front side), and the right side is the image side (rear side). SP is an aperture stop, and IP is an image plane. On the image plane IP, an imaging surface (light receiving surface) of an imaging element such as a CCD sensor or a CMOS sensor in a digital still camera or a video camera, or a film surface (photosensitive surface) in a silver halide film camera is disposed. Also, an arrow indicates the movement locus during zooming from the wide-angle end to the telephoto end under the lens group that moves during zooming, and an arrow indicates the movement direction during focusing from a distant object to a close object over the lens group that moves during focusing.

[0034] In the zoom lenses of Examples 1, 3 and 5 shown in FIG. 1, FIG. 5 and FIG. 9, the first lens group L1 with negative refractive power is composed of a negative lens G11, a negative lens G12 and a positive lens (positive meniscus lens in Examples 2, 3 and 4) G13 arranged in this order from the object side to the image side. The second lens group L2 with positive refractive power is composed of four lenses G21 to G24, among which the lenses G23 and G24 are cemented lenses. An aperture stop SP is arranged between the lenses G21 and G22. The lens G21 may be moved with respect to the optical axis (in a direction including a component perpendicular thereto) to perform vibration reduction. The third lens group L3 with negative refractive power is composed of a negative lens G31 arranged on the object side and a positive lens G32 arranged on the image side. The fourth lens group L4 with positive refractive power is composed of a positive meniscus lens G41 with a convex surface facing the image side.

[0035] In the zoom lenses of Examples 2 and 4 shown in FIG. 3 and FIG. 7, the first lens group L1 with negative refractive power is composed of a negative lens G11, a negative lens G12, and a positive meniscus lens G13 arranged in this order from the object side to the image side. The second lens group L2 with positive refractive power is composed of five lenses G21 to G25, among which the lenses G22, G23, and the lenses G24 and G25 are cemented lenses. An aperture stop SP is arranged between the lenses G21 and G22. The lens G21 may be moved relative to the optical axis to perform vibration reduction. The third lens group L3 with negative refractive power is composed of a negative lens G31 arranged on the object side and a positive lens G32 arranged on the image side. The fourth lens group L4 with positive refractive power is composed of a positive meniscus lens G41 with a convex surface facing the image side.

[0036] In the first to fifth embodiments, the first lens group L1 and the fourth lens group L4 do not move during zooming from the wide-angle end to the telephoto end, and the second lens group L2 and the third lens group L3 move toward the object side. During focusing from an object at infinity to an object at close range, the third lens group L3 moves toward the image side. The first lens group L1 may include lenses other than the lenses G11, G12, and G13. The third lens group L3 may include lenses other than the lenses G31 and G32. The entire second lens group L2 may be moved relative to the optical axis to perform vibration reduction.

[0037] Numerical Examples 1 to 5 corresponding to Examples 1 to 5 are shown below. In each numerical example, surface number i indicates the order of the surface when counted from the object side. r indicates the radius of curvature (mm) of the i-th surface from the object side, and d indicates the lens thickness or air distance (mm) between the i-th and (i+1)-th surfaces. The (variable) in d indicates that the distance changes during zooming. nd is the refractive index at the d-line of the optical material between the i-th and (i+1)-th surfaces. νd is the Abbe number based on the d-line of the optical material between the i-th and (i+1)-th surfaces.

[0038] The Abbe number νd based on the d-line is expressed as νd=(Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm).

[0039] BF stands for back focus (mm). Back focus is the distance on the optical axis from the final surface of a zoom lens (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. The total lens length is the distance on the optical axis from the frontmost surface of a zoom lens (the lens surface closest to the object) to the final surface plus the back focus.

[0040] An "*" next to a surface number means that the surface has an aspheric shape. The aspheric shape is expressed by the following formula, where X is the displacement from the apex of the surface in the optical axis direction, H is the height from the optical axis in a direction perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, K is the conic constant, and A4 to A12 are aspheric coefficients. The "e±x" of the conic constant and the aspheric coefficients is ×10 ±x means.

[0041]

number

[0042] Moreover, values ​​corresponding to the conditions of the above-mentioned expressions (1) to (9) in Numerical Examples 1 to 5 are summarized in Table 1. The zoom lens of each Numerical Example satisfies all of the conditions of the expressions (1) to (9).

[0043] 2, 4, 6, 8, and 10 respectively show longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) at (a) the wide-angle end and (b) the telephoto end in the infinity focused state of the zoom lenses of Numerical Examples 1 to 5. The vertical axis shows the image height (mm) at which the lateral aberration is evaluated, and the horizontal axis shows the amount of aberration. In the spherical aberration diagrams, Fno shows the F-number, the solid line shows the spherical aberration for the d-line (wavelength 587.6 nm), and the two-dot chain line shows the spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagrams, the solid line S shows the astigmatism on the sagittal image plane, and the dashed line M shows the astigmatism on the meridional image plane. The distortion aberration diagrams show the distortion aberration at the d-line. The chromatic aberration diagrams show the chromatic aberration of magnification at the g-line. ω is the half angle of view (°). [Numerical example 1] Unit: mm Surface Data Surface number rd nd νd 1 103.873 1.43 1.60311 60.6 2 10.850 5.97 3* -186.184 2.18 1.53504 55.7 4* 38.942 1.65 5 58.485 2.77 1.84666 23.8 6 -1747.182 (variable) 7 -311.967 2.10 1.48749 70.2 8 -35.702 3.00 9(Aperture) ∞ 1.00 10 15.588 2.70 1.77250 49.6 11 40.316 3.74 12 13.813 2.05 1.91082 35.2 13 7.282 4.91 1.49700 81.7 14 -44.568 (variable) 15 -35.780 1.43 1.80518 25.4 16 41.580 1.69 17* -24.214 2.00 1.53504 55.7 18* -23.108 (variable) 19 -815.444 4.09 1.84666 23.8 20 -38.459 12.34 Image plane ∞ Aspheric Data 3rd page K = 0.00000e+00 A 4=-6.74603e-05 A 6= 1.08422e-06 A 8=-1.26175e-08 A10 = 4.47171e-11 Side 4 K = 0.00000e+00 A 4=-9.54960e-05 A 6= 1.00703e-06 A 8=-1.55082e-08 A10= 6.23127e-11 Page 17 K = 0.00000e+00 A 4=-1.97758e-04 A 6= 2.23182e-06 A 8= 1.03932e-07 A10=-5.01273e-10 Side 18 K = 0.00000e+00 A 4=-7.84118e-05 A 6= 1.39236e-06 A 8= 5.85891e-08 A10=-3.20321e-10 Various data Zoom ratio 2.02 Wide Angle Mid-Telephoto Focal length 14.42 20.00 29.10 F-number 4.08 4.98 5.71 Half angle of view (°) 38.88 32.46 24.93 Image height 11.63 12.72 13.52 Lens length 78.51 78.51 78.51 BF 12.34 12.34 12.34 d 6 16.18 9.09 1.50 d14 1.80 2.31 4.68 d18 5.47 12.05 17.27 Lens Group Data Group starting plane focal length 1 1 -20.11 2 7 16.82 3 15 -25.60 4 19 47.56 [Numerical example 2] Unit: mm Surface Data Surface number rd nd νd 1 -1003.559 1.45 1.65844 50.9 2 11.098 5.39 3* 34.762 2.00 1.53110 55.9 4* 16.432 2.46 5 24.768 2.38 1.84666 23.8 6 64.790 (variable) 7 -658.578 2.08 1.48749 70.2 8 -28.601 3.00 9(Aperture) ∞ 1.00 10 15.618 4.08 1.72916 54.1 11 -13.742 1.45 1.83481 42.7 12 -574.376 3.40 13 28.235 1.45 1.83481 42.7 14 7.839 4.35 1.49700 81.7 15 -25.583 (variable) 16 -32.533 1.45 1.63980 34.5 17 19.586 0.46 18* 33.492 2.25 1.53110 55.9 19 25250.657 (variable) 20 -81.453 3.57 2.05090 26.9 21 -31.525 12.41 Image plane ∞ Aspheric Data 3rd page K = 0.00000e+00 A 4= 2.03027e-05 A 6= 5.92109e-07 A 8=-1.58429e-09 A10 = 1.86363e-11 Side 4 K = 0.00000e+00 A 4=-4.11883e-05 A 6= 3.28081e-07 A 8=-7.07908e-10 A10=-1.47238e-11 Side 18 K = 0.00000e+00 A 4=-4.96608e-05 A 6= 3.67035e-07 A 8= 1.26779e-08 A10=-1.44610e-10 Various data Zoom ratio 2.02 Wide Angle Mid-Telephoto Focal length 14.42 20.00 29.10 F-number 4.12 5.22 6.40 Half angle of view (°) 38.92 32.50 24.89 Image height 11.65 12.75 13.50 Lens length 78.53 78.53 78.53 BF 12.41 12.41 12.41 d 6 15.95 8.96 1.45 d15 1.20 1.85 4.77 d19 6.74 13.08 17.67 Lens Group Data Group starting plane focal length 1 1 -19.48 2 7 17.59 3 16 -27.47 4 20 47.21 [Numerical example 3] Unit: mm Surface Data Surface number rd nd νd 1 107.396 1.44 1.60311 60.6 2 10.941 6.45 3* -71.181 2.51 1.53504 55.7 4* 59.185 1.57 5 55.328 2.57 1.84666 23.8 6 1839.252 (variable) 7 -295.204 2.01 1.48749 70.2 8 -35.713 3.00 9(Aperture) ∞ 1.00 10 15.110 2.41 1.77250 49.6 11 41.722 3.76 12 13.783 2.05 1.91082 35.2 13 7.064 4.73 1.49700 81.7 14 -61.950 (variable) 15 -35.711 1.43 1.76182 26.5 16 35.712 1.30 17* -50.246 1.98 1.53504 55.7 18* -34.460 (variable) 19 -351.849 4.02 1.84666 23.8 20 -37.402 11.74 Image plane ∞ Aspheric Data 3rd page K = 0.00000e+00 A 4=-5.85235e-06 A 6= 3.59366e-07 A 8=-3.07329e-09 A10=-3.10257e-12 Side 4 K = 0.00000e+00 A 4=-3.23448e-05 A 6= 2.71346e-07 A 8=-4.36123e-09 A10=-5.84250e-12 Page 17 K = 0.00000e+00 A 4=-1.47706e-04 A 6= 3.18761e-06 A 8= 6.92571e-08 A10=-4.81924e-10 Side 18 K = 0.00000e+00 A 4=-4.11418e-05 A 6= 1.74602e-06 A 8= 4.98882e-08 A10=-3.86901e-10 Various data Zoom ratio 2.02 Wide Angle Mid-Telephoto Focal length 14.42 20.00 29.10 F-number 4.08 5.22 6.43 Half angle of view (°) 38.95 32.48 24.89 Image height 11.66 12.73 13.50 Lens length 78.51 78.51 78.51 BF 11.74 11.74 11.74 d 6 16.21 9.12 1.50 d14 1.52 1.90 4.21 d18 6.81 13.53 18.84 Lens Group Data Group starting plane focal length 1 1 -20.29 2 7 16.91 3 15 -27.24 4 19 49.14 [Numerical example 4] Unit: mm Surface Data Surface number rd nd νd 1 190.216 1.50 1.67830 57.2 2 10.664 4.52 3* 173.419 2.21 1.53110 55.9 4* 27.175 1.51 5 33.930 2.33 1.97068 28.1 6 185.811 (variable) 7 -81.272 1.94 1.50200 80.7 8 -26.236 1.34 9(Aperture) ∞ 1.00 10 18.272 3.55 1.78089 49.1 11 -14.880 1.00 1.88225 38.1 12 -534.955 4.86 13 30.470 0.99 1.79820 37.3 14 9.466 3.32 1.49700 81.7 15 -25.423 (variable) 16 -19.319 1.00 1.75561 47.1 17 25.982 0.75 18 325.028 2.01 1.85185 43.0 19 -24.928 (variable) 20* -352.726 3.73 1.53110 55.9 21* -31.364 17.22 Image plane ∞ Aspheric Data 3rd page K = 0.00000e+00 A 4=-9.10237e-06 A 6=-1.86815e-07 A 8= 8.45854e-09 A10=-4.13943e-11 Side 4 K = 0.00000e+00 A 4=-5.78205e-05 A 6=-5.77617e-07 A 8= 1.29562e-08 A10=-1.07334e-10 Page 20 K = 0.00000e+00 A 4=-2.47579e-05 A 6= 5.14230e-08 A 8=-1.33592e-10 A10=-6.60940e-13 Page 21 K = 0.00000e+00 A 4=-2.30481e-05 A 6= 2.35015e-08 A 8= 5.19608e-11 A10=-2.05357e-12 Various data Zoom ratio 2.02 Wide Angle Mid-Telephoto Focal length 14.42 20.00 29.10 F-number 4.12 5.22 6.40 Half angle of view (°) 38.94 32.38 24.84 Image height 11.65 12.68 13.47 Lens length 75.78 75.78 75.78 d 6 16.26 8.74 1.00 d15 1.16 1.72 4.77 d19 3.57 10.53 15.22 Lens Group Data Group starting plane focal length 1 1 -20.78 2 7 17.54 3 16 -37.21 4 20 64.56 [Numerical example 5] Unit: mm Surface Data Surface number rd nd νd 1∞0.00 2 49.683 1.20 1.77250 49.6 3 11.439 6.55 4* -52.694 2.38 1.53504 55.7 5* 83.284 0.58 6 77.119 2.86 1.84666 23.9 7 -146.627 (variable) 8 -788.613 2.27 1.48749 70.2 9 -38.750 3.20 10 (Aperture) ∞ 0.00 11∞1.00 12 16.034 2.34 1.80400 46.5 13 33.602 4.30 14 12.731 1.60 1.95375 32.3 15 7.424 4.05 1.49700 81.7 16 -52.566 (variable) 17 -31.291 1.00 1.63980 34.5 18 22.704 1.52 19* -31.961 1.95 1.53504 55.7 20* -19.173 (variable) 21 -105.252 3.95 1.90043 37.4 22 -32.563 14.20 Image plane ∞ Aspheric Data Side 4 K = 0.00000e+00 A 4=-5.04723e-05 A 6= 9.76372e-07 A 8=-1.59689e-08 A10= 1.32446e-10 A12=-5.68130e-13 5th page K = 0.00000e+00 A 4=-7.17848e-05 A 6= 7.38593e-07 A 8=-1.30318e-08 A10=9.24639e-11 A12=-3.59028e-13 Page 19 K = 0.00000e+00 A 4=-2.04732e-04 A 6= 3.95714e-07 A 8= 4.88410e-08 A10=2.88130e-09 A12=-5.69956e-11 Page 20 K = 0.00000e+00 A 4=-1.03004e-04 A 6=-4.09262e-07 A 8= 4.95272e-08 A10=5.33678e-10 A12=-9.62541e-12 Various data Zoom ratio 2.04 Wide Angle Mid-Telephoto Focal length 14.41 20.03 29.35 F-number 4.08 5.18 6.43 Half angle of view (°) 40.33 33.59 25.69 Image height 12.24 13.31 14.12 Lens length 80.14 80.14 80.14 BF 14.20 14.20 14.20 d 7 16.90 9.35 1.30 d16 2.57 3.06 5.63 d20 5.74 12.79 18.28 Lens Group Data Group starting plane focal length 1 1 -20.50 2 8 17.40 3 17 -29.02 4 21 51.05

[0044] [Table 1]

[0045] Fig. 11 shows an imaging device (digital camera) equipped with the zoom lens of Examples 1 to 5. In the figure, 10 denotes a camera body, and 11 denotes an imaging optical system constituted by the zoom lens of any of Examples 1 to 5. Reference numeral 12 denotes an imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body 10 and receives a subject image formed by the imaging optical system 11 (captures the subject).

[0046] By using the zoom lenses according to the first to fifth embodiments as an imaging optical system, it is possible to provide an imaging device that is small and lightweight, has a wide angle of view, and is capable of acquiring images of good quality.

[0047] The above embodiment includes the following configurations.

[0048] (Configuration 1) A zoom lens consisting of four lens groups, the four lens groups are, in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power; During zooming, the first lens group and the fourth lens group do not move, and the second lens group and the third lens group move, thereby changing the interval between adjacent lens groups; the third lens group L3 has a negative lens and a positive lens arranged closer to the image side than the negative lens, the fourth lens group is composed of one positive meniscus lens having a convex shape facing an image side, When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 0.5≦f3 / f1≦2.0 A zoom lens characterized by satisfying the following conditions. (Configuration 2) When the focal length of the second lens group is f2, 0.70≦f2 / (-f1)≦1.40 2. The zoom lens according to claim 1, wherein the following condition is satisfied: (Configuration 3) When the focal length of the fourth lens group is f4, 1.90≦f4 / (-f1)≦3.50 3. The zoom lens according to configuration 1 or 2, which satisfies the following conditions: (Configuration 4) When the focal length of the second lens group is f2, 0.20≦f2 / (-f3)≦0.90 4. The zoom lens according to any one of configurations 1 to 3, which satisfies the following condition: (Configuration 5) When the focal length of the fourth lens group is f4, 0.30≦(-f3) / f4≦0.80 5. The zoom lens according to any one of configurations 1 to 4, which satisfies the following condition: (Configuration 6) Let BFw be the distance on the optical axis from the image side surface of the lens closest to the image side in the zoom lens to the image plane, and LDw be the distance on the optical axis from the object side surface of the lens closest to the object side in the zoom lens to the image plane. 0.10≦BFw / LDw≦0.30 6. The zoom lens according to any one of configurations 1 to 5, which satisfies the following condition: (Configuration 7) The shape factor of the positive meniscus lens is SF_G41, the radius of curvature of the object side surface of the positive meniscus lens is rG41a, and the radius of curvature of the image side surface of the positive meniscus lens is rG41b, SF_G41=(rG41b+rG41a) / (rG41b-rG41a) When -3.00≦SF_G41≦-1.01 7. The zoom lens according to any one of configurations 1 to 6, which satisfies the following condition: (Configuration 8) When the lateral magnifications of the second lens group at the telephoto end and the wide-angle end in a state where the lens is focused on an object at infinity are β2t and β2w, respectively, 1.35≦β2t / β2w≦2.00 8. The zoom lens according to any one of configurations 1 to 7, which satisfies the following condition: (Configuration 9) When the lateral magnifications of the third lens group at the telephoto end and the wide-angle end in a state where the lens is focused on an object at infinity are β3t and β3w, respectively, 0.05≦β3t / β3w≦1.45 9. The zoom lens according to any one of configurations 1 to 8, which satisfies the following condition: (Configuration 10) 2. The zoom lens according to configuration 1, wherein the first lens group is composed only of lenses having refractive power. (Configuration 11) 11. The zoom lens according to any one of configurations 1 to 10, wherein the first lens group includes at least two negative lenses and one positive lens. (Configuration 12) 12. The zoom lens according to configuration 11, wherein the first lens group is composed of, in order from the object side to the image side, a negative lens, a negative lens, and a positive lens. (Configuration 13) 13. The zoom lens according to any one of configurations 1 to 12, wherein the second lens group includes an aperture stop. (Configuration 14) 14. The zoom lens according to any one of configurations 1 to 13, wherein the third lens group moves for focusing. (Configuration 15) 15. A zoom lens according to any one of configurations 1 to 14, wherein the second lens group, in whole or in part, moves relative to the optical axis as an anti-vibration group. (Configuration 16) The zoom lens according to any one of configurations 1 to 15, and an image sensor for capturing an image of a subject through the zoom lens.

[0049] The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0050] L1 First lens group L2 Second lens group L3: Third lens group L4 4th lens group

Claims

1. A zoom lens consisting of four lens groups, the four lens groups are, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power; During zooming, the first lens group and the fourth lens group do not move, and the second lens group and the third lens group move, thereby changing the interval between adjacent lens groups; The third lens group L3 has a negative lens and a positive lens arranged closer to the image side than the negative lens, the fourth lens group is composed of one positive meniscus lens having a convex shape facing an image side, When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 0.5≦f3 / f1≦2.0 A zoom lens characterized by satisfying the following conditions.

2. When the focal length of the second lens group is f2, 0.70≦f2 / (-f1)≦1.40 2. The zoom lens according to claim 1, which satisfies the following condition:

3. When the focal length of the fourth lens group is f4, 1.90≦f4 / (-f1)≦3.50 2. The zoom lens according to claim 1, which satisfies the following condition:

4. When the focal length of the second lens group is f2, 0.20≦f2 / (-f3)≦0.90 2. The zoom lens according to claim 1, which satisfies the following condition:

5. When the focal length of the fourth lens group is f4, 0.30≦(-f3) / f4≦0.80 2. The zoom lens according to claim 1, which satisfies the following condition:

6. Let BFw be the distance on the optical axis from the image side surface of the lens closest to the image side in the zoom lens to the image plane, and LDw be the distance on the optical axis from the object side surface of the lens closest to the object side in the zoom lens to the image plane. 0.10≦BFw / LDw≦0.30 2. The zoom lens according to claim 1, which satisfies the following condition:

7. The shape factor of the positive meniscus lens is SF_G41, the radius of curvature of the object side surface of the positive meniscus lens is rG41a, and the radius of curvature of the image side surface of the positive meniscus lens is rG41b, SF_G41=(rG41b+rG41a) / (rG41b−rG41a) When −3.00≦SF_G41≦−1.01 2. The zoom lens according to claim 1, which satisfies the following condition:

8. When the lateral magnifications of the second lens group at the telephoto end and the wide-angle end in a state in which the lens is focused on an object at infinity are β2t and β2w, respectively, 1.35≦β2t / β2w≦2.00 2. The zoom lens according to claim 1, which satisfies the following condition:

9. When the lateral magnifications of the third lens group at the telephoto end and the wide-angle end in a state in which the lens is focused on an object at infinity are β3t and β3w, respectively, 0.05≦β3t / β3w≦1.45 2. The zoom lens according to claim 1, which satisfies the following condition:

10. 2. The zoom lens according to claim 1, wherein the first lens group is composed only of lenses having refractive power.

11. 2. The zoom lens of claim 1, wherein the first lens group includes at least two negative lenses and one positive lens.

12. 12. The zoom lens according to claim 11, wherein the first lens group is composed of, in order from the object side to the image side, a negative lens, a negative lens and a positive lens.

13. 2. The zoom lens according to claim 1, wherein the second lens group includes an aperture stop.

14. 2. The zoom lens according to claim 1, wherein the third lens group moves for focusing.

15. 2. The zoom lens according to claim 1, wherein the second lens group is configured to move, in whole or in part, relative to the optical axis as a vibration isolating group.

16. A zoom lens according to any one of claims 1 to 15; and an image sensor for capturing an image of a subject through the zoom lens.

Images