Zoom lens and imaging device

Abstract

To provide a zoom lens which is advantageous in reducing the size thereof and obtaining high optical performance over an entire zoom range.SOLUTION: A zoom lens is provided, consisting of a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, and succeeding groups L3, L4, arranged in order from the object side to the image side. The first lens group does not move for zooming while distances between adjacent lens groups change when zooming. The zoom lens satisfies conditions expressed as: 0.68≤f1 / ft≤1.20, 0.27≤TDt / ft≤0.90, where f1 represents a focal length of the first lens group, ft represents a focal length at the telephoto end, and TDt represents an optical axial distance from the most object-side surface of the zoom lens to the image plane at the telephoto end.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a zoom lens and an imaging apparatus. [Background technology]

[0002] In some imaging devices such as surveillance cameras, network cameras, and video cameras, there is a trend to increase the number of pixels while widening the pixel pitch of the imaging element, i.e., to increase the size of the imaging element. On the other hand, there is a demand for zoom lenses used in such imaging devices to be smaller and lighter.

[0003] Patent Document 1 discloses a zoom lens having first to fifth lens groups having positive, negative, positive, negative and positive refractive powers in that order from the object side to the image side, moving the second, third and fourth lens groups to change magnification, and having a magnification ratio of about 5. Patent Document 2 discloses a zoom lens having first to fourth lens groups having positive, negative, negative and positive refractive powers in that order from the object side to the image side, moving the second and third lens groups to change magnification, and having a magnification ratio of about 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-118737 A [Patent Document 2] Japanese Patent Application Publication No. 62-027712 Summary of the Invention [Problem to be solved by the invention]

[0005] The zoom lens of Patent Document 1 has a relatively high zoom ratio, but it may become large in order to accommodate the increase in size of the image sensor while maintaining optical performance, while the zoom lens of Patent Document 2 is relatively small and lightweight, but its optical performance is insufficient for the increase in the number of pixels of the image sensor.

[0006] The present invention provides a zoom lens that is advantageous in terms of, for example, compactness and high optical performance over the entire zoom range. [Means for solving the problem]

[0007] A zoom lens according to one aspect of the present invention includes, in order from an object side to an image side, a first lens group having positive refractive power, a second lens group having negative refractive power, Contains two or more lens groups The first lens group does not move for zooming, and the spacing between adjacent lens groups does not change during zooming. The first lens group has a first subgroup having positive refractive power on the object side of the longest air space in the first lens group, and a second subgroup having negative refractive power on the image side of the air space. The focal length of the first lens group is f1, the focal length at the telephoto end is ft, and the length on the optical axis from the surface closest to the object of the zoom lens to the image plane at the telephoto end is TDt. The focal length of the first lens group is f1a, the length on the optical axis from the surface of the first lens group closest to the object side to the surface of the first lens group closest to the image side is D1 When 0.68≦f1 / ft≦1.20 0.27≦TDt / ft≦0.90 1.20≦f1 / f1a≦2.60 0.01≦D1 / f1≦0.30 The present invention is characterized in that the following conditions are satisfied: An image pickup apparatus using the above-described zoom lens also constitutes another aspect of the present invention. Effect of the Invention

[0008] The present invention can provide, for example, a zoom lens that is advantageous in terms of size reduction and high optical performance over the entire zoom range. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment. [Diagram 2] 5A and 5B are aberration diagrams of the zoom lens of Example 1 at the wide-angle end and an intermediate zoom position, respectively. [Diagram 3] 5A to 5C are aberration diagrams at the telephoto end of the zoom lens of the first embodiment. [Figure 4] FIG. 11 is a cross-sectional view of a zoom lens according to a second embodiment. [Diagram 5] 11A and 11B are aberration diagrams of the zoom lens of Example 2 at the wide-angle end and an intermediate zoom position, respectively. [Figure 6] 8A to 8C are aberration diagrams at the telephoto end of the zoom lens of Example 2. [Figure 7] FIG. 11 is a cross-sectional view of a zoom lens according to a third embodiment. [Figure 8] 11A and 11B are aberration diagrams of the zoom lens of Example 3 at the wide-angle end and an intermediate zoom position, respectively. [Figure 9] 11A to 11C are aberration diagrams at the telephoto end of the zoom lens of Example 3. [Figure 10] FIG. 11 is a cross-sectional view of a zoom lens according to a fourth embodiment. [Figure 11] 11A and 11B are aberration diagrams of the zoom lens of Example 4 at the wide-angle end and an intermediate zoom position, respectively. [Figure 12] 13A to 13C are aberration diagrams at the telephoto end of the zoom lens of Example 4. [Figure 13] FIG. 13 is a cross-sectional view of a zoom lens according to a fifth embodiment. [Figure 14] 13A and 13B are aberration diagrams of the zoom lens of Example 5 at the wide-angle end and an intermediate zoom position, respectively. [Figure 15] 13A to 13C are aberration diagrams at the telephoto end of the zoom lens of Example 5. [Figure 16] FIG. 13 is a cross-sectional view of a zoom lens according to a sixth embodiment. [Figure 17] 13A and 13B are aberration diagrams of the zoom lens of Example 6 at the wide-angle end and an intermediate zoom position, respectively. [Figure 18] 13A to 13C are aberration diagrams at the telephoto end of the zoom lens of Example 6. [Figure 19] 1A and 1B are diagrams showing a surveillance camera using the zoom lens of each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] Prior to the description of specific Examples 1 to 6 described later, matters common to each of the Examples will be described. Figures 1, 3, 5, 7, 9, and 11 respectively show cross sections of the zoom lenses of Examples 1 to 6 at the wide-angle end. The zoom lenses of each Example are used as imaging optical systems in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras. In each figure, the left side is the object side, and the right side is the image side. The zoom lenses of each Example have multiple lens groups. The lens group here refers to a group of one or more lenses that move or stand still as a unit when changing magnification. The distance between adjacent lens groups changes when changing magnification.

[0012] The zoom lens of each embodiment is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, and subsequent groups L3 to Ln (n=4 to 6) arranged in this order from the object side to the image side. When changing the magnification from the wide-angle end to the telephoto end, the first lens group L1 is stationary, and any of the other lens groups moves so that the interval between the adjacent lens groups changes. The zoom lens of each embodiment satisfies the conditions shown in the following formulas (1) and (2), where f1 is the focal length of the first lens group L1, ft is the focal length at the telephoto end of the zoom lens, and TDt is the total optical length at the telephoto end of the zoom lens. By satisfying these conditions, it is possible to realize high optical performance over the entire zoom range while being compact. 0.68≦f1 / ft≦1.20 (1) 0.27≦TDt / ft≦0.90 (2) The total optical length of a zoom lens is the length on the optical axis from the surface closest to the object (front surface) to the image surface. More specifically, it is the total lens length, which is the length on the optical axis from the front surface to the surface closest to the image (last surface), plus the back focus, which is the air-equivalent length on the optical axis from the last surface to the image surface. If there are optical elements such as a filter or glass block in the back focus, the air-equivalent length increased by the optical elements is also added to the back focus.

[0013] Formula (1) shows the condition regarding the relationship between the focal length of the first lens group L1 and the focal length at the telephoto end of the zoom lens. If f1 / ft is below the lower limit of formula (1), the refractive power of the first lens group L1 becomes too strong, which makes it difficult to correct spherical aberration and coma aberration over the entire zoom range, which is undesirable. If f1 / ft is above the upper limit of formula (1), the refractive power of the first lens group L1 becomes too weak, which leads to an increase in the overall optical length, which is undesirable.

[0014] Equation (2) shows the condition regarding the relationship between the total optical length of the zoom lens and the focal length at the telephoto end of the zoom lens. If TDt / ft exceeds the upper limit of equation (2), the total optical length becomes too long, which is undesirable. If TDt / ft falls below the lower limit of equation (2), the power of each lens group in the zoom lens becomes excessively strong, which is undesirable because it becomes difficult to correct spherical aberration and curvature of field over the entire zoom range.

[0015] In the zoom lens of each embodiment, the first lens group L1 is composed of a positive first subgroup 1a arranged on the object side and a negative second subgroup 1b arranged on the image side in terms of the longest air gap in the first lens group. The focal length of the first subgroup 1a is f1a, the focal length of the second subgroup 1b is f1b, the total length of the first lens group (the length on the optical axis from the surface of the first lens group L1 closest to the object side to the surface closest to the image side) is D1, and the focal length of the second lens group is f2. In this case, it is desirable to satisfy at least one of the conditions shown in the following expressions (1), (2), and (3).

[0016] 1.20≦f1 / f1a≦3.00 (3) 0.90≦f1b / f2≦6.50 (4) 0.01≦D1 / f1≦0.60 (5) Formula (3) shows the condition regarding the relationship between the focal length of the first lens group L1 and the focal length of the first sub group 1a. When f1 / f1a exceeds the upper limit of formula (3), the refractive power of the first sub group 1a with respect to the first lens group L1 becomes too strong, which is undesirable because it becomes difficult to correct chromatic aberration in the first lens group L1. When f1 / f1a falls below the lower limit of formula (3), the refractive power of the first lens group L1 becomes too strong, which is undesirable because it becomes difficult to correct spherical aberration and coma aberration over the entire zoom range.

[0017] Formula (4) shows the condition regarding the relationship between the focal length of the second sub-group 1b and the focal length L2 of the second lens group. When f1b / f2 exceeds the upper limit of formula (4), the refractive power of the second sub-group f1b becomes too strong, which makes it difficult to correct chromatic aberration in the first lens group L1, which is not preferable. When f1b / f2 falls below the lower limit of formula (4), the refractive power of the second lens group L2 relative to the second sub-group 1b becomes too strong, which increases the fluctuation of spherical aberration and coma aberration due to zooming, which is not preferable.

[0018] Equation (5) shows the condition regarding the relationship between the total length of the first lens group L1 and the focal length of the first lens group L1. If D1 / f1 exceeds the upper limit of equation (5), the total length of the first lens group L1 becomes too large, which undesirably increases the size of the entire zoom lens system. If D1 / f1 falls below the lower limit of equation (5), the total length of the first lens group L1 becomes too small, which undesirably increases the refractive power of the lenses constituting the first lens group L1 and makes it difficult to correct spherical aberration.

[0019] It is also preferable that the first lens group L1 is made up of four or less lenses. By making the first lens group L1 out of four or less lenses, it is possible to prevent the first lens group L1 and the entire zoom lens system from becoming large.

[0020] In addition, it is desirable that in the first lens group L1, the lens closest to the object side has positive refractive power and the lens closest to the image side has negative refractive power, so that the principal point position of the first lens group L1 is located on the object side, thereby realizing a more compact telephoto zoom lens.

[0021] Furthermore, it is desirable that the zoom lens of each embodiment satisfies the condition shown in the following formula (6), where the average Abbe number of at least one negative lens in the first lens unit L1 is ν1nave. 15.0≦ν1nave≦60.0 (6) Formula (6) shows the condition for the average Abbe number of the negative lenses in the first lens group L1. If v1nave exceeds the upper limit of formula (6), it is not preferable because it becomes difficult to correct axial chromatic aberration, particularly at the telephoto end. If v1nave falls below the lower limit of formula (6), it is not preferable because it becomes difficult to correct lateral chromatic aberration over the entire zoom range.

[0022] It is also desirable to provide at least one rear stationary group in the subsequent group that does not move during zooming from the wide-angle end to the telephoto end, and at least one of the rear stationary groups is composed of three or more lenses. By configuring the rear stationary group, in which the chief ray of the off-axis light beam becomes relatively high, with three or more lenses, it is possible to satisfactorily correct aberrations of the off-axis light beam, that is, coma aberration and curvature of field.

[0023] Furthermore, it is desirable that the lens group closer to the image side than the second lens group L2 moves during focusing. The smaller the mass of the lens group that moves during focusing, the more preferable it is for the mechanism that drives it. It is also desirable that the focal length change less during focusing. The lens group disposed closer to the image side than the second lens group L2 tends to have a smaller mass and has a smaller magnification change effect, making it suitable for focusing. It is more preferable to set the numerical ranges of the formulas (1) to (6) as follows: 0.69≦f1 / ft≦1.07 (1a) 0.50≦TDt / ft≦0.89 (2a) 1.40≦f1 / f1a≦2.80 (3a) 1.20≦f1b / f2≦5.00 (4a) 0.05≦D1 / f1≦0.45 (5a) 20.0≦ν1ave≦50.0 (6a) Moreover, it is more preferable to set the numerical ranges of the formulas (1a) to (6a) as follows: 0.69≦f1 / ft≦0.94 (1b) 0.73≦TDt / ft≦0.88 (2b) 1.60≦f1 / f1a≦2.60 (3b) 1.50≦f1b / f2≦4.35 (4b) 0.09≦D1 / f1≦0.30 (5b) 24.0≦ν1ave≦41.0 (6b) Examples 1 to 6 will now be described in detail. EXAMPLES

[0024] The zoom lens of the first embodiment shown in FIG. 1 is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power as a subsequent group, and a fourth lens group L4 with positive refractive power, which are arranged in order from the object side to the image side. As shown by the arrows in FIG. 1, when changing the magnification from the wide-angle end to the telephoto end, the first lens group L1 is stationary, and the second and fourth lens groups L2 and L4 move, thereby changing the interval between the adjacent lens groups. Note that the fourth lens group L4 moves along the locus shown by the solid and dotted arrows when focused on an object at infinity and a close distance object, respectively. The fourth lens group L4 moves during focusing.

[0025] SP is the aperture and I is the image plane. The light receiving surface of an image sensor such as a CCD sensor or CMOS sensor or the photosensitive surface of a silver halide film is disposed on the image plane I. P is a glass block such as a low pass filter or a face plate of the image sensor. These are the same in the other embodiments described later. In this embodiment, the aperture SP is provided closest to the object in the third lens group L3.

[0026] Numerical Example 1 shows examples of more specific numerical values ​​of the zoom lens of Example 1. Fig. 2(A) is an aberration diagram of the zoom lens of Example 1 (Numerical Example 1) at the wide-angle end, Fig. 2(B) is an aberration diagram of the zoom lens at the intermediate zoom position, and Fig. 3 is an aberration diagram of the zoom lens at the telephoto end.

[0027] In Numerical Example 1, surface number i is the order of the surface when counted from the object side, r is the radius of curvature of the i-th surface (mm), d is the lens thickness or air space (mm) between the i-th surface and the (i+1)-th surface, and nd is the refractive index at the d-line of the optical material between the i-th surface and the (i+1)-th surface. νd is the Abbe number based on the d-line of the optical material between the i-th surface and the (i+1)-th surface. The Abbe number νd of a material is given by, when the refractive indexes of the optical material at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, respectively. νd=(Nd-1) / (NF-NC) It is expressed as:

[0028] As mentioned above, the total optical length is the length on the optical axis from the surface closest to the object (the front surface) of a zoom lens to the image plane. More specifically, it is the total lens length, which is the length on the optical axis from the front surface to the surface closest to the image (the final surface), plus the back focus, which is the air-equivalent length on the optical axis from the final surface to the image plane.

[0029] BF stands for back focus (mm). "Back focus" is the distance on the optical axis from the final surface of a zoom lens (the surface of the lens with power closest to the image side) to the paraxial image plane, expressed in air equivalent length. In the spherical aberration diagrams, Fno indicates the F-number, the solid line indicates the spherical aberration for the d-line (wavelength 587.6 nm), and the two-dot chain line indicates the spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagrams, ω is the half angle of view (°), the solid line S indicates the sagittal image plane, and the dashed line M indicates the meridional image plane. The distortion aberration is shown for the d-line. The chromatic aberration diagrams show the chromatic aberration of magnification at the g-line. The explanations regarding the numerical examples and aberration diagrams are the same for the other embodiments described later.

[0030] The values ​​of the above-mentioned conditions (formulas (1) to (6)) in Example 1 (Numerical Example 1) are summarized in Table 1. As can be seen from Table 1, the zoom lens of Numerical Example 1 satisfies each of the conditions. EXAMPLES

[0031] The zoom lens of the second embodiment shown in FIG. 4 is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power, which are successive groups, arranged in order from the object side to the image side. As shown by the arrows in FIG. 4, when changing the magnification from the wide-angle end to the telephoto end, the first lens group L1 is stationary, and the second, fourth, and fifth lens groups L2, L4, and L5 move, thereby changing the interval between the adjacent lens groups. The fourth lens group L4 moves along the locus shown by the solid and dotted arrows when focused on an object at infinity and a close distance object, respectively. The fourth lens group L4 moves during focusing. The aperture SP is provided on the most image side of the third lens group L3.

[0032] Numerical Example 2 shows more specific examples of numerical values ​​of the zoom lens of Example 2. Fig. 5(A) is an aberration diagram of the zoom lens of Example 2 (Numerical Example 2) at the wide-angle end, Fig. 5(B) is an aberration diagram of the zoom lens at the intermediate zoom position, and Fig. 6 is an aberration diagram of the zoom lens at the telephoto end.

[0033] Table 1 shows the values ​​of the above-mentioned conditions (formulas (1) to (6)) in Example 2 (Numerical Example 2) together. As can be seen from Table 1, the zoom lens of Numerical Example 2 satisfies each of the conditions. EXAMPLES

[0034] The zoom lens of the third embodiment shown in FIG. 7 is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power, which are successive groups, arranged in order from the object side to the image side. As shown by the arrows in FIG. 7, when changing the magnification from the wide-angle end to the telephoto end, the first lens group L1 is stationary, and the second, fourth, and fifth lens groups L2, L4, and L5 move, thereby changing the interval between the adjacent lens groups. Note that the fifth lens group L5 moves along the locus shown by the solid and dotted arrows when focused on an object at infinity and a close distance object, respectively. The fifth lens group L5 moves during focusing. The aperture SP is provided on the most object side of the third lens group L3.

[0035] Numerical Example 3 shows an example of more specific numerical values ​​of the zoom lens of Example 3. Fig. 8(A) is an aberration diagram of the zoom lens of Example 3 (Numerical Example 3) at the wide-angle end, Fig. 8(B) is an aberration diagram of the zoom lens at the intermediate zoom position, and Fig. 9 is an aberration diagram of the zoom lens at the telephoto end.

[0036] Table 1 shows the values ​​of the above-mentioned conditions (formulas (1) to (6)) in Example 3 (Numerical Example 3). As can be seen from Table 1, the zoom lens of Numerical Example 3 satisfies each of the conditions. EXAMPLES

[0037] The zoom lens of the fourth embodiment shown in FIG. 10 is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power as a subsequent group, and a fourth lens group L4 with positive refractive power, which are arranged in order from the object side to the image side. As shown by the arrows in FIG. 10, when changing the magnification from the wide-angle end to the telephoto end, the first lens group L1 is stationary, and the second and fourth lens groups L2 and L4 move, so that the interval between the adjacent lens groups changes. Note that the fourth lens group L4 moves along the locus shown by the solid and dotted arrows when focused on an object at infinity and a close distance object, respectively. The fourth lens group L4 moves during focusing. The aperture SP is provided on the most object side of the third lens group L3.

[0038] Numerical Example 4 shows an example of more specific numerical values ​​of the zoom lens of Example 4. Fig. 11(A) is an aberration diagram of the zoom lens of Example 4 (Numerical Example 4) at the wide-angle end, Fig. 11(B) is an aberration diagram of the zoom lens at the intermediate zoom position, and Fig. 12 is an aberration diagram of the zoom lens at the telephoto end.

[0039] Table 1 shows the values ​​of the above-mentioned conditions (equations (1) to (6)) in Example 4 (Numerical Example 4). As can be seen from Table 1, the zoom lens of Numerical Example 4 satisfies each of the conditions. EXAMPLES

[0040] The zoom lens of the fifth embodiment shown in FIG. 13 is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with negative refractive power, and a sixth lens group L6 with positive refractive power, which are subsequent groups, arranged in order from the object side to the image side. As shown by the arrows in FIG. 13, when changing the magnification from the wide-angle end to the telephoto end, the first lens group L1 is stationary, and the second, third, and fifth lens groups L2, L3, and L5 move, thereby changing the interval between the adjacent lens groups. The fifth lens group L5 moves to trace the loci shown by the solid and dotted arrows when focused on an object at infinity and a close distance object, respectively. The fifth lens group L5 moves during focusing. An aperture SP is provided in the fourth lens group L4.

[0041] Numerical Example 5 shows more specific examples of numerical values ​​of the zoom lens of Example 5. Fig. 14(A) is an aberration diagram of the zoom lens of Example 5 (Numerical Example 5) at the wide-angle end, Fig. 14(B) is an aberration diagram of the zoom lens at the intermediate zoom position, and Fig. 15 is an aberration diagram of the zoom lens at the telephoto end.

[0042] Table 1 shows the values ​​of the above-mentioned conditions (formulas (1) to (6)) in Example 5 (Numerical Example 5) together. As can be seen from Table 1, the zoom lens of Numerical Example 5 satisfies each of the conditions. EXAMPLES

[0043] The zoom lens of Example 6 shown in FIG. 16 is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power as a subsequent group, and a fourth lens group L4 with positive refractive power, which are arranged in order from the object side to the image side. As shown by the arrows in FIG. 16, when changing the magnification from the wide-angle end to the telephoto end, the first lens group L1 is stationary, and the second and fourth lens groups L2 and L4 move, so that the interval between the adjacent lens groups changes. Note that the fourth lens group L4 moves along the locus shown by the solid and dotted arrows when focused on an object at infinity and a close distance object, respectively. The fourth lens group L4 moves during focusing. The aperture SP is provided on the most object side of the third lens group L3.

[0044] Numerical Example 6 shows an example of more specific numerical values ​​of the zoom lens of Example 6. Fig. 17(A) is an aberration diagram of the zoom lens of Example 6 (Numerical Example 6) at the wide-angle end, Fig. 17(B) is an aberration diagram of the zoom lens at the intermediate zoom position, and Fig. 18 is an aberration diagram of the zoom lens at the telephoto end.

[0045] Table 1 shows the values ​​of the above-mentioned conditions (formulas (1) to (6)) in Example 6 (Numerical Example 6). As can be seen from Table 1, the zoom lens of Numerical Example 6 satisfies each of the conditions. [Numerical example 1] Unit: mm Surface Data Surface number rd nd νd 1 143.242 4.00 1.49700 81.6 2 -143.242 0.20 3 43.357 4.50 1.49700 81.6 4 202.735 10.42 5 572.578 1.20 1.76182 26.5 6 79.390 (variable) 7 62.416 0.80 1.51680 64.2 8 26.127 2.25 9 -37.802 0.70 1.83481 42.7 10 37.230 1.50 1.94594 18.0 11 224.375 (variable) 12 (Aperture) ∞ 0.75 13 43.472 3.30 1.69680 55.5 14 -58.067 0.20 15 21.339 5.80 1.62041 60.3 16 -43.365 0.80 1.92286 18.9 17 47.508 3.75 18 30.401 4.70 1.92286 18.9 19 -22.570 0.70 1.90366 31.3 20 14.836 (variable) 21 33.444 2.70 1.48749 70.2 22 ∞ (variable) 23 ∞ 1.20 1.51633 64.1 24∞1.00 Image plane ∞ Various data Zoom ratio 2.99 Wide Angle Mid-Telephoto Focal length 49.29 88.26 147.49 F-number 4.12 4.12 4.12 Half angle of view (°) 12.40 6.82 4.05 Image height 10.72 10.72 10.72 Optical total length 127.94 127.94 127.94 BF 26.99 32.82 19.06 d 6 1.99 19.31 33.49 d11 34.58 17.26 3.08 d20 16.10 10.27 24.03 d22 25.20 31.03 17.27 Lens Group Data Group starting plane focal length 1 1 102.89 2 7 -28.29 3 12 36.99 4 21 68.60 5 23∞ [Numerical example 2] Unit: mm Surface Data Surface number rd nd νd 1 187.144 3.10 1.49700 81.6 2 -187.144 0.20 3 37.843 5.37 1.59522 67.7 4 224.478 12.32 5 -5366.802 1.20 2.00100 29.1 6 61.733 (variable) 7 -182.674 0.70 1.88300 40.8 8 19.525 1.77 1.94594 18.0 9 40.864 (variable) 10 33.896 3.93 1.62299 58.2 11 -50.266 0.20 12 38.215 3.90 1.59522 67.7 13 -33.355 0.80 2.00069 25.5 14 520.525 0.71 15 (Aperture) ∞ (Variable) 16 -33.703 0.70 1.59282 68.6 17 18.434 (variable) 18 56.450 4.14 1.95375 32.3 19 -55.914 (variable) 20∞1.201.5163364.1 21∞1.00 Image plane ∞ Various data Zoom ratio 2.62 Wide Angle Mid-Telephoto Focal length 66.00 109.71 173.00 F-number 4.12 4.84 4.84 Half angle of view (°) 9.13 5.46 3.44 Image height 10.72 10.72 10.72 Optical total length 127.94 127.94 127.94 BF 20.98 14.91 9.94 d6 1.66 19.08 33.33 d 9 34.58 17.16 2.91 d15 19.12 21.46 19.82 d17 12.57 16.30 22.90 d19 19.19 13.12 8.15 Lens Group Data Group starting plane focal length 1 1 137.96 2 7 -40.28 3 10 30.10 4 16 -20.00 5 18 29.99 6 20∞ [Numerical example 3] Unit: mm Surface Data Surface number rd nd νd 1 133.782 4.13 1.49700 81.6 2 -133.782 0.20 3 35.717 5.68 1.49700 81.6 4 201.019 9.86 5 11281.738 1.20 1.74950 35.3 6 56.450 (variable) 7 -74.976 0.70 1.95375 32.3 8 18.809 1.60 1.94594 18.0 9 51.428 (variable) 10 (Aperture) ∞ 0.65 11 18.732 4.48 1.63854 55.4 12 -41.720 0.20 13 40.386 5.67 1.59282 68.6 14 -16.362 0.80 2.00330 28.3 15 -1420.006 (variable) 16 -31.427 0.70 1.53775 74.7 17 15.859 (variable) 18 45.758 3.47 1.74950 35.3 19 -104.537 (variable) 20∞1.201.5163364.1 21∞1.00 Image plane ∞ Various data Zoom ratio 2.14 Wide Angle Mid-Telephoto Focal length 70.00 105.54 150.00 F-number 4.12 4.84 4.84 Half angle of view (°) 8.81 5.82 4.07 Image height 10.72 10.72 10.72 Optical total length 127.94 127.94 127.94 BF 42.23 38.61 24.73 d 6 5.12 18.76 29.91 d 9 27.70 14.07 2.91 d15 2.91 3.43 3.86 d17 10.66 13.75 27.20 d19 40.43 36.82 22.94 Lens Group Data Group starting plane focal length 1 1 104.85 2 7 -31.43 3 10 22.44 4 16 -19.50 5 18 42.89 6 20∞ [Numerical example 4] Unit: mm Surface Data Surface number rd nd νd 1 173.951 3.29 1.49700 81.6 2 -173.951 0.20 3 36.009 1.20 1.76182 26.5 4 31.126 6.59 1.49700 81.6 5 164.821 22.99 6 -369.147 1.20 1.69895 30.1 7 49.265 (variable) 8 28.138 0.80 1.51680 64.2 9 24.125 1.79 10 -33.276 0.70 1.83481 42.7 11 21.542 1.39 1.94594 18.0 12 61.963 (variable) 13(Aperture) ∞ 0.68 14 41.273 3.99 1.69680 55.5 15 -36.994 0.19 16 31.334 3.59 1.62041 60.3 17 -23.866 0.80 1.92286 18.9 18 337.121 4.00 19 29.813 2.47 1.92286 18.9 20 -23.865 0.70 1.90366 31.3 21 17.305 (variable) 22 -55.688 2.70 1.48749 70.2 23 -27.644 (variable) 24 ∞ 1.20 1.51633 64.1 25∞1.00 Image plane ∞ Various data Zoom ratio 1.56 Wide Angle Mid-Telephoto Focal length 94.36 118.27 147.42 F-number 4.12 4.63 4.64 Half angle of view (°) 6.46 5.08 4.06 Image height 10.72 10.72 10.72 Optical total length 127.95 127.95 127.95 BF 19.02 30.36 34.48 d 7 1.60 8.78 14.65 d12 16.56 9.38 3.51 d21 31.50 20.15 16.03 d23 17.22 28.57 32.69 Lens Group Data Group starting plane focal length 1 1 136.91 2 8 -26.15 3 13 30.37 4 22 109.16 5 24∞ [Numerical example 5] Unit: mm Surface Data Surface number rd nd νd 1 46.858 7.63 1.49700 81.5 2 -79.530 2.83 3 -71.562 1.30 1.88300 40.8 4 -274.316 (variable) 5 -77.084 0.80 1.57099 50.8 6 53.024 (variable) 7 107.810 0.81 1.95906 17.5 8 193.512 (variable) 9 24.269 3.53 1.48749 70.2 10 -141.966 8.43 11(Aperture) ∞ 8.12 12 39.009 1.71 1.53775 74.7 13 -57.992 0.46 14 -26.465 0.60 1.96300 24.1 15 -98.143 (variable) 16 -34.480 0.59 1.49700 81.5 17 21.934 (variable) 18 -706.480 2.28 1.92286 18.9 19 -40.776 6.78 20∞1.201.5163364.1 21∞1.00 Image plane ∞ Various data Zoom ratio 2.30 Wide Angle Mid-Telephoto Focal length 68.17 126.83 156.80 F-number 4.12 4.12 4.12 Half angle of view (°) 8.90 4.79 3.89 Image height 10.82 10.82 10.82 Optical total length 126.65 126.65 126.65 BF 8.57 8.57 8.57 d4 1.38 36.37 48.03 d 6 7.04 13.55 2.32 d 8 43.09 1.59 1.15 d15 20.26 8.08 2.42 d17 7.23 19.41 25.06 Lens Group Data Group starting plane focal length 1 1 120.40 2 5 -54.90 3 7 252.65 4 9 44.73 5 16 -26.88 6 18 46.81 7 20∞ [Numerical example 6] Unit: mm Surface Data Surface number rd nd νd 1 183.897 2.86 1.49700 81.5 2 -164.756 0.20 3 44.535 4.37 1.49700 81.5 4 327.457 13.50 5 1448.057 1.20 1.85478 24.8 6 95.116 (variable) 7 109.040 1.00 1.49700 81.5 8 26.580 2.12 9 -35.010 0.80 1.83481 42.7 10 51.613 1.24 1.95906 17.5 11 4281.220 (variable) 12(Aperture) ∞ 1.99 13 29.085 3.58 1.49700 81.5 14 -32.787 0.19 15 24.189 4.34 1.48749 70.2 16 -21.298 0.80 1.90366 31.3 17 113.532 10.91 18 51.154 2.43 1.72825 28.5 19 -29.228 5.52 20 -18.460 0.80 1.77250 49.6 21 20.506 (variable) 22 28.397 3.91 1.49700 81.5 23 -89.540 (variable) 24 ∞ 1.20 1.51633 64.1 25∞1.00 Image plane ∞ Various data Zoom ratio 2.98 Wide Angle Mid-Telephoto Focal length 50.36 94.13 150.00 F-number 4.12 4.12 4.12 Half angle of view (°) 12.10 6.41 4.01 Image height 10.72 10.72 10.72 Optical total length 127.60 127.60 127.60 BF 16.44 24.52 16.75 d 6 1.25 20.25 32.91 d11 34.16 15.16 2.50 d21 14.00 5.92 13.69 d23 14.65 22.73 14.96 Lens Group Data Group starting plane focal length 1 1 108.00 2 7 -27.55 3 12 30.04 4 22 43.86 5 24∞

[0046] [Table 1]

[0047] FIG. 19 shows an imaging device (monitoring camera) 10 equipped with a zoom lens according to any one of the above-mentioned embodiments 1 to 6. Reference numeral 11 denotes a camera body, and reference numeral 12 denotes an imaging element built into the camera body 11 for receiving (capturing) a subject image formed by a zoom lens 15 as an imaging optical system. Image data generated using an imaging signal from the imaging element 12 is recorded in a memory 13 or output to the outside (network, etc.) via a cable 14. An electrical signal instructing the operation of the imaging device may be received via the cable 14. Also, image data with higher image quality may be recorded or output by performing electronic aberration correction processing on the generated image data.

[0048] The above-described embodiments are merely representative examples, and various modifications and changes are possible for each embodiment when implementing the present invention. For example, the number of lenses constituting each lens group may be changed, and the shape of each lens may be changed (such as by providing an aspheric surface). In addition, any of the lens groups or lenses may be moved in a direction perpendicular to the optical axis to reduce (correct) image blur caused by vibrations such as camera shake. [Explanation of symbols]

[0049] L1 First lens group L2 Second lens group L3: Third lens group L4 4th lens group L5 Fifth lens group L6 6th lens group

Claims

1. A zoom lens having, in order from an object side to an image side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a subsequent group including two or more lens groups, the first lens group does not move for varying magnification, and the interval between adjacent lens groups varies during the variation of magnification; the first lens group has a first subgroup having a positive refractive power on an object side of the longest air space in the first lens group, and a second subgroup having a negative refractive power on an image side of the air space; Let f1 be the focal length of the first lens group, ft be the focal length at the telephoto end, TDt be the length on the optical axis from the surface of the zoom lens closest to the object side to the image plane at the telephoto end, f1a be the focal length of the first sub group, and D1 be the length on the optical axis from the surface of the first lens group closest to the object side to the surface of the first lens group closest to the image side. 0.68≦f1 / ft≦1.20 0.27≦TDt / ft≦0.90 1.20≦f1 / f1a≦2.60 0.01≦D1 / f1≦0.30 A zoom lens characterized by satisfying the following conditions.

2. When the focal length of the second subgroup is f1b and the focal length of the second lens group is f2, 0.90≦f1b / f2≦6.50 2. The zoom lens according to claim 1, which satisfies the following condition:

3. 3. The zoom lens according to claim 1, wherein the first lens group is made up of four or less lenses.

4. 4. The zoom lens according to claim 1, wherein in the first lens group, the lens closest to the object side has positive refractive power, and the lens closest to the image side has negative refractive power.

5. When the average Abbe number of the negative lenses in the first lens group is ν1nave, 15.0≦ν1nave≦60.0 5. The zoom lens according to claim 1, which satisfies the following condition:

6. 6. The zoom lens according to claim 1, wherein the subsequent group includes at least one lens group that does not move for varying magnification, and at least one of the at least one lens group includes at least three lenses.

7. 7. The zoom lens according to claim 1, wherein a lens group closer to the image side than the second lens group moves for focusing.

8. 8. The zoom lens according to claim 1, wherein the subsequent lens group comprises, in order from the object side to the image side, a third lens group having a positive refractive power and a fourth lens group having a positive refractive power.

9. 8. The zoom lens according to claim 1, wherein the subsequent lens group consists of, arranged in order from the object side to the image side, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power.

10. 8. The zoom lens according to claim 1, wherein the subsequent group consists of, arranged in order from the object side to the image side, a third lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a sixth lens group having positive refractive power.

11. A zoom lens having, in order from an object side to an image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a subsequent group including two or more lens groups, the first lens group does not move for varying magnification, and the interval between adjacent lens groups varies during the variation of magnification; the first lens group has a first subgroup having a positive refractive power on an object side of the longest air space in the first lens group, and a second subgroup having a negative refractive power on an image side of the air space; Let f1 be the focal length of the first lens group, ft be the focal length at the telephoto end, TDt be the length on the optical axis from the surface of the zoom lens closest to the object to the image plane at the telephoto end, f1b be the focal length of the second sub group, f2 be the focal length of the second lens group, and D1 be the length on the optical axis from the surface of the first lens group closest to the object to the surface of the first lens group closest to the image. 0.68≦f1 / ft≦1.20 0.27≦TDt / ft≦0.90 1.20≦f1b / f2≦6.50 0.01≦D1 / f1≦0.30 A zoom lens characterized by satisfying the following conditions.

12. A zoom lens according to any one of claims 1 to 11; and an image sensor for capturing an image formed by the zoom lens.

Images